The construction of pH-sensitive starch-based carrier to control the delivery of curcumin for preservation

The construction of pH-sensitive starch-based carrier to control the delivery of curcumin for preservation | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article The construction of pH-sensitive starch-based carrier to control the delivery of curcumin for preservation Xiaojia Guo, Shujin Liu, Lanyan Yang, Chaoguang Zhao, Liu Shi, and 5 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-3887107/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 9 You are reading this latest preprint version Abstract The controlled release of curcumin by the pH-sensitive carrier can achieve a long-term preservation effect, which is beneficial to extend the shelf-life of fish. The FTIR, XRD, 1 H NMR, zeta potential, swelling ratio, and TG indicates the pH-sensitive starch-based carrier with a narrow pH-sensitive range (pH 6-7) is successfully fabricated by the carboxymethyl starch grafted with methacrylic acid first and then cross-linked with β-cyclodextrin to achieve dual-functionalities. The FTIR, XRD, and fluorescence spectroscopy reveals the mechanism of curcumin encapsulated by starch-based carrier is related to hydrophobic interactions and inter-molecular hydrogen bonding. The encapsulated curcumin shows improved stability, enjoyable antioxidant activity, antibacterial activity, and biocompatibility. The pH, TVB-N, TVC, and drip loss tests prove the application of carrier-curcumin complex with the concentration of 10 mg/mL on the preservation of yellow catfish can extend the shelf-life for 2-4 days with chilling storage and improve the storage quality of fillets. This work provides a dual-functionalities strategy to construct a pH-sensitive starch-based carrier to deliver curcumin and offers a promising choice in fish preservation. pH-sensitive carrier carboxymethyl starch fish preservation Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 1. Introduction Fish is a part of a healthy diet and provides essential components such as proteins, vitamins, polyunsaturated fatty acids, and minerals that are necessary for human health. However, fish is spoiled easily due to microbial growth, enzymatic autolysis, and lipid oxidation(Ali et al. 2022). Excellent preservation techniques can effectively prevent microbial spoilage and extend the shelf-life with limited adverse changes in the quality. Traditional preservation methods such as freezing, chilling, drying, salting, and preservative additives also are applied for fish preservation(Gokoglu 2019 ). Natural preservatives, such as plant-derived polyphenols, phenolics, flavonoids, and animal-derived lysozymes, lactoferrin, polysaccharides, etc., have become promising alternatives to synthetic preservatives due to the reduction of negative impacts on health(Yu et al. 2021 ). Among them, curcumin (Cur), widely used as spices, flavorings, and colorants in the food industry, is a natural polyphenolic bioactive ingredient extracted from dry rhizomes of Curcuma longa(Yilmaz et al. 2016 ). Even though curcumin has both antimicrobial and antioxidant properties, the actual applications of curcumin are often limited by its low water solubility and sensitivity to light, heat, oxygen, enzymes, etc.(Shlar et al. 2015 ). In this case, curcumin is a promising candidate for the development of new carriers to enhance its stability and solubility. Environmental responsive polymeric materials have attracted great attention due to their dynamic structures and properties in response to environmental changes, such as temperature, light, pH, magnetic fields, etc.(Ding et al. 2022 ). Among them, pH-sensitive material is the most representative and widely used in the delivery of drugs or functional factors in biomedical and food areas, which is designed to improve the targetability and uptake of drugs or functional factors(Xu et al. 2022 ). The pH changes during the chilling storage of fish, which decreases first and then increases due to the lactic acid accumulation and protein degradation respectively. However seldom pH-sensitive material is used in the preservation of fish. Even though the controlled release of preservations can achieve long-term preservation. Herein, we construct a pH-sensitive starch-based carrier to deliver curcumin for the preservation of yellow catfish. Starch is a nontoxic, inexpensive, biocompatible, and renewable natural polymer, which has been used to design carriers(Rodrigues and Emeje 2012 ). Carboxymethyl starch (CMS) is an anionic polymer obtained from the introduction of carboxylic groups in starch structure and has been proposed as a novel pH-sensitive excipient(Assaad et al. 2011 ). The existence of polar functional groups such as carboxylic acid endows the polymer with pH-sensitive properties. The grafting of methacrylic acid (MAA) on CMS modification promotes the pH-sensitive properties because it provides more hydrogen bonds at low pH and enhances electrostatic repulsion at high pH(Saboktakin et al. 2009 ). β-cyclodextrin (β-CD) is a kind of suitable microgel containing a molecular inclusion component(Zhang et al. 2015 ). Based on the unique molecular recognition ability of β-CD and the pH-sensitive nature of CMS grafted with MAA (CMS-PMAA), the microgel (CMS-PMAA-β-CD) obtained by the cross-linking reaction not only possesses the function of including organic compounds but also sensitively responds to pH changes. It is used as a carrier to deliver curcumin for the preservation of yellow catfish Pelteobagrus fulvidraco . The pH-sensitivity, stability, antioxidant activity, antibacterial activity, biocompatibility, and fish preservation effect of carrier-curcumin complex (CMS-PMAA-β-CD-Cur) are evaluated. This work provides a dual-functionalities strategy to construct a pH-sensitive starch-based carrier to deliver curcumin and verifies the preservation effect on fish during chilling storage. 2. Materials and methods 2.1 Materials Carboxymethyl starch sodium (CMS) with DS of 0.2, methacrylic acid (MAA), potassium persulfate (KPS), sodium hydroxide, ethanol, sodium trimetaphosphate (STMP), and β-cyclodextrin (β-CD) with 99% purity were obtained from Sinopharm Chemical Reagent Co., Ltd. Curcumin (Cur) with 98% purity was purchased from Shanghai Macklin Biochemical Technology Co., Ltd. All other chemicals and reagents were purchased from Sigma-Aldrich Trading Co. Ltd. The reagents and solvents without special instruction were of analytical grade and used without further purification. 2.2 Synthesis of CMS-PMAA The CMS grafted MAA was prepared according to the method introduced by the previous report with some modifications(Haq 2020 ). CMS (2 g) was dispersed in distilled water (98 mL) in a three-mouth flask with constant mechanical stirring. The resulting solution was gelatinized at 90 ℃ for 30 min and then cooled at 70 ℃. KPS solution (20 mL, 0.04 g/mL) used as the initiator to activate starch hydroxyl groups was added to the flask and incubated for 30 min. Then the solution mixed with PMAA (10 mL) and NaOH (2 mL, 0.5 g/mL) solution was slowly added to the flask and reacted for 2 h. The whole reaction occurred in an N 2 atmosphere. Afterward, the reaction mixture was cooled to room temperature and washed with deionized water and ethanol in turns three times. The precipitation was collected and freeze-dried to obtain CMS-PMAA. 2.3 Preparation of CMS-PMAA-β-CD The CMS-PMAA was crosslinked with β-CD using STMP as the crosslinking agent according to the method described by the previous report with slight modifications(Zhang et al. 2015 ). CMS-PMAA (10 g) and β-CD (1 g) were dissolved in NaOH solution (50 mL, pH 9). STMP (1 g) was slowly added to the mixture with thorough stirring. Then the mixture was heated at 40 ℃ for 1 h without stirring to form the gel. The whole gel was crushed with a spatula and washed with deionized water, ethanol, and acetone in turns three times. After freeze-drying, the gel was further crushed by a crusher and passed through a sieve of 200 mesh to obtain CMS-PMAA-β-CD. 2.4 Loading of curcumin into CMS-PMAA-β-CD CMS-PMAA-β-CD solution (100 mL) with predetermined concentration (1, 2, 4, 6, 8 mg/mL) was gelatinized for 30 min in the boiling water bath and then cooled at 40 ℃. The pH value of CMS-PMAA-β-CD solution was adjusted to predetermined pH (6.0, 6.5, 7.0, 7.5, 8.0) by adding citric acid/phosphate buffer (0.1 mol/L). Then curcumin/ethanol solution (8 mL, 2.5 mg/mL) was slowly added and stirred for predetermined time (1, 2, 3, 4 h) in the dark. The ethanol was removed by rotary evaporation and the unembedded curcumin was removed by centrifugation at 1000 r/min for 10 min(Hu et al. 2022 ). The supernatant was collected and freeze-dried to complete the loading process. Among them, CMS-PMAA-β-CD solution (2 mg/mL, pH 6.5) and reaction for 3 h were the optimal loading parameters to fabricate CMS-PMAA-β-CD-Cur. As the control, curcumin/ethanol solution (8 mL, 2.5 mg/mL) was slowly added to β-CD solution (100 mL, 2 mg/mL) and stirred for 3 h in the dark to obtain β-CD-Cur. 2.5 Characterization The morphology of the samples was performed on a scanning electron microscope (SEM, SU8100, Hitachi, Japan) with an electron accelerating voltage of 10 kV. Fourier transform infrared (FT-IR) spectra were recorded on Nicolet iS50 FTIR spectrometer (Thermo-Fisher, USA) using the KBr-disk method. X-ray diffractometry (XRD) was performed on a D8-ADVANCE X-Ray diffractometer (Bruker, Germany) with Cu-Kα radiation source (λ = 1.5405 Å) at 40 kV and 15 mA. All diffraction peaks were determined in a 2θ range of 4–40º at a scan speed of 2º/min. Hydrogen Nuclear magnetic resonance ( 1 H NMR) spectra were recorded on a 400M spectrometer (Bruker, Germany) operating at 400 MHz. The CMS-PMAA-β-CD was dissolved in DMSO-D 2 O (20 mg/mL), and the other samples were dispersed in D 2 O (20 mg/mL). The zeta potential was measured by Zeta-sizer Nano ZSE (Malvern, UK). Thermogravimetry (TG) analysis and derivative thermal gravimetric (DTG) analysis experiments were performed on a Simultaneous Thermal Analysis instrument (Mettler Toledo, Switzerland) in nitrogen flow with a heating rate of 10 ℃/min and a temperature range from room temperature to 800 ℃. The binding between Cur and CMS-PMAA-β-CD was determined using fluorescence spectrophotometry F-7000 (Hitachi, Tokyo, Japan). The excitation wavelength was 425 nm, and the emission spectra were recorded from 450 to 650 nm with slit widths of 5 nm. 2.6 Determination of swelling ratio The CMS-PMAA-β-CD (0.1 g) was immersed in various citric acid/phosphate buffer solutions (25 mL, 0.1 mol/L) with predetermined pH (6.0, 6.5, 7.0, 7.5, 8.0) at 25 ℃ for 24 h. Then the solution was centrifugated at 2000 r/min for 10 min to remove the excess water. The weight of the swollen sample was measured. The swelling ratio was calculated according to the following relation(Mahkam 2010 ): $$Swelling ratio\left(\%\right)=\frac{{W}_{s}-{\text{W}}_{d}}{{W}_{s}}\times 100$$ Where, W s and W d represent the weight of swollen sample and dried samples, respectively. 2.7 Loading efficiency and loading ability of curcumin 2.7.1 Loading efficiency In section 2.4 , the unembedded curcumin precipitate was collected by centrifugation. Then the precipitate was dissolved in 100% ethanol (100 mL). Its absorbance was measured by a UV-vis spectrophotometer at 425 nm to determine the content of unembedded curcumin, which was calculated by the standard curve of curcumin-absorbance. The total weight of curcumin added in the loading process was 20 mg. The Loading efficiency was calculated by the following formula(Xiao-Min et al. 2019): $$Loading efficiency\left(\%\right)=(1-\frac{\text{A}\text{m}\text{o}\text{u}\text{n}\text{t} \text{o}\text{f} \text{u}\text{n}\text{e}\text{m}\text{b}\text{e}\text{d}\text{d}\text{e}\text{d} \text{c}\text{u}\text{r}\text{c}\text{u}\text{m}\text{i}\text{n}}{\text{T}\text{o}\text{t}\text{a}\text{l} \text{w}\text{e}\text{i}\text{g}\text{h}\text{t} \text{o}\text{f} \text{c}\text{u}\text{r}\text{c}\text{u}\text{m}\text{i}\text{n}})\times 100$$ 2.7.2 Loading ability CMS-PMAA-β-CD-Cur (0.50 mg) was dispersed in 80% (v/v) ethanol (10 mL), and then the solution was dealt with ultrasonic for 10 min and centrifugated at 3500 r/min for 10 min. The absorbance of the supernatant was measured by a UV-vis spectrophotometer at 425 nm to obtain the content of embedded curcumin, which was determined by the standard curve of curcumin-absorbance. The loading ability was calculated by the following formula(Xiao-Min et al. 2019): $$Loading ability(ug/mg)=\frac{\text{A}\text{m}\text{o}\text{u}\text{n}\text{t} \text{o}\text{f} \text{e}\text{m}\text{b}\text{e}\text{d}\text{d}\text{e}\text{d} \text{c}\text{u}\text{r}\text{c}\text{u}\text{m}\text{i}\text{n}}{\text{T}\text{o}\text{t}\text{a}\text{l} \text{w}\text{e}\text{i}\text{g}\text{h}\text{t} \text{o}\text{f} \text{C}\text{M}\text{S}-\text{P}\text{M}\text{A}\text{A}-{\beta }-\text{C}\text{D}-\text{C}\text{u}\text{r}}$$ 2.8 The release of curcumin The sample (0.5 g) was dispersed in 80% (v/v) ethanol (10 mL). The obtained suspension (5 mL) placed in a dialysis bag (8–12 kDa) was put in phosphate-buffered saline (PBS, 100 mL, 0.1 mol/L, pH 6.0, 6.5, 7.0, 7.5, 8.0) containing 1 wt.% Tween 80. The process occurred in 37 ℃ with constant stirring. PBS (5 mL) was withdrawn and replaced with fresh PBS (5 mL) at predetermined time. Then its absorbance value was read at 425 nm using a UV-vis spectrophotometer to determine the released curcumin. The total amount of curcumin in sample was calculated by loading ability. The cumulative release of curcumin from the sample was calculated as follows: $$Curcumin release\left(\text{%}\right)=\frac{\text{A}\text{m}\text{o}\text{u}\text{n}\text{t} \text{o}\text{f} \text{r}\text{e}\text{l}\text{e}\text{a}\text{s}\text{e}\text{d} \text{c}\text{u}\text{r}\text{c}\text{u}\text{m}\text{i}\text{n} }{\text{T}\text{o}\text{t}\text{a}\text{l} \text{a}\text{m}\text{o}\text{u}\text{n}\text{t} \text{o}\text{f} \text{c}\text{u}\text{r}\text{c}\text{u}\text{m}\text{i}\text{n} \text{i}\text{n} \text{s}\text{a}\text{m}\text{p}\text{l}\text{e}}\times 100$$ 2.9 Stability of curcumin 2.9.1 Thermal stability The sample (0.5 g) placed in a transparent glass vial was put in the hot water bath at predetermined temperature (50, 70, 90, 110 ℃) for 20 min. Subsequently, the heated sample was immediately cooled at 25 ℃ using an ice water bath(Meng et al. 2021b ). 2.9.2 Photochemical stability The sample (0.5 g) was evenly placed in a transparent glass vial and exposed to a UV light (365 nm, 10 W) for predetermined time (24, 48, 72, 96 h). The distance between the sample and UV light was 10 cm. After treatment, the retained curcumin in the sample was determined according to the method described in 2.7.2. The total amount of curcumin in sample was calculated by loading ability. The retention rate of curcumin was calculated by using the following equations(Sun et al. 2017 ): $$Retention rate\left(\text{%}\right)=\frac{\text{A}\text{m}\text{o}\text{u}\text{n}\text{t} \text{o}\text{f} \text{r}\text{e}\text{t}\text{a}\text{i}\text{n}\text{e}\text{d} \text{c}\text{u}\text{r}\text{c}\text{u}\text{m}\text{i}\text{n}}{\text{T}\text{o}\text{t}\text{a}\text{l} \text{a}\text{m}\text{o}\text{u}\text{n}\text{t} \text{o}\text{f} \text{c}\text{u}\text{r}\text{c}\text{u}\text{m}\text{i}\text{n} \text{i}\text{n} \text{s}\text{a}\text{m}\text{p}\text{l}\text{e}}\times 100$$ 2.10 Antioxidant activity 2.10.1 DPPH radical scavenging activity The sample (0.1 g) dispersed in deionized water (10 mL) was added to DPPH-ethanol solution (10 mL, 0.2 mol/L) and mixed thoroughly. The mixed solution was placed in the dark for 30 min. The absorbance (A t ) of the above solutions was measured at 517 nm using the UV-vis spectrophotometer. The free radical scavenging activity of the sample was calculated as follows(Stojadinovic et al. 2013 ): $$DPPH scavenging activity\left(\text{%}\right)=(1-\frac{{\text{A}}_{t}-{\text{A}}_{b}}{{\text{A}}_{c}})\times 100$$ Where the A b was the absorbance of the mixed solution of 10 mL sample solution and 10 mL ethanol, and the A c was the absorbance of the mixed solution of 10 mL deionized water and 10 mL DPPH-ethanol solution. 2.10.2 ABTS radical scavenging activity ABTS free radicals stock solution was produced by mixing ABTS (14.4 mmol/L) with potassium persulfate (5.2 mmol/L) in a ratio of 1:1 (v/v). The stock solution was placed in the dark at room temperature for 16 h. The ABTS working solution with an absorbance value of 0.70 at 734 nm was obtained by diluting the stock solution with PBS solution (0.01 mol/L, pH 7.4). The sample (1 mL, 10 mg/mL) was mixed with ABTS working solution (4.5 mL) and reacted for 6 min in the dark. The ABTS free radical scavenging capability of sample was calculated as follows(Bhoopathy et al. 2020 ): $$ABTS scavenging activity\left(\text{%}\right)=\frac{{\text{A}}_{d}-{\text{A}}_{s}}{{\text{A}}_{d}}\times 100$$ Where the A d was the absorbance of the mixed solution of 1 mL PBS and 4.5 mL ABTS working solution at 734 nm, and A s was the absorbance of the test samples at 734 nm. 2.11 In vitro antibacterial test Fish spoilage bacteria Shewanella putrefaciens was selected to assess the antibacterial activity of CMS-PMAA-β-CD-Cur. After sterilization by UV irradiation for 2 h, the sample was dispersed in physiological saline to obtain the suspension with the concentration of 10 mg/mL. A prepared test solution was mixed with nutrient agar medium to yield predetermined concentration. The bacterial suspension (100 µL, 10 6 CFU/mL) and test solution (50 µL) were seeded into a 96-well tissue culture plate and incubated at 37 ℃ for 10 h. The sterile water as the test solution was the blank control. The absorbance values (OD 600) were measured at a test wavelength of 600 nm. 2.12 Cytotoxicity assay Cell viability performance of CMS-PMAA-β-CD-Cur was tested by MTT assay using mouse lung fibroblasts (L929). The samples with the predetermined weight (2.5, 5, 10 mg) were immersed in MEM medium (1 mL) at 4 ℃ for 24 h to prepare extracted solutions. L929 fibroblasts were seeded into a 96-well tissue culture plate at a density of 2 × 10 3 cells/well and incubated in a humidified 37 ℃, 5% CO 2 atmosphere for 24 h. Then the culture medium was replaced with the prepared extraction medium and continued incubation for 24 h. The blank tissue culture plates were served as the control. For the cell viability determination, the medium was replaced with MTT/MEM solution (100 µL, 0.5 mg/mL) and incubated for 4 h. Then MTT/MEM solution was replaced with dimethyl sulfoxide (DMSO, 150 µL). The OD value of the obtained solution was measured at 490 nm by an enzyme-linked immune absorbent assay reader (SpectraMax iD5, China). The cell viability of sample was calculated as follows: $$Cell viability\left(\text{%}\right)=\frac{{\text{O}\text{D}}_{Sample}-{\text{O}\text{D}}_{Blank}}{{\text{O}\text{D}}_{Control}-{\text{O}\text{D}}_{Blank}}\times 100$$ 2.13 Fish preservation trial 2.13.1 Preparation of fish samples All animal assays were carried out abided by the standard of the National Regulation of China for the Care and Use of Laboratory Animals complied with the National Research Council's Guide for the Care and Use of Laboratory Animals. The live yellow catfish Pelteobagrus fulvidraco (250 ± 50 g; N = 105) were purchased from a local market (Wuhan, China). All samples were beheaded, eviscerated, rinsed with running water, and placed on ice. The samples were divided into three groups: (1) samples were sprayed with distilled water as the control; (2) samples were sprayed with 10 mg/mL CMS-PMAA-β-CD-Cur solution; (3) samples were sprayed with 10 mg/mL CMS-PMAA-β-CD solution. After being drained, all samples were individually packed in a vacuum bag and pumped to a vacuum state. Each treatment was analyzed at a 2-day interval during 12 days(Lan et al. 2022 ). 2.13.2 Determination of pH values Fillet samples (1 g) were homogenized in distilled water (9 mL) for 20 min at 4 ℃. The pH of the supernatant of the solution was tested. 2.13.3 Determination of TVB-N The total volatile basic nitrogen (TVB-N) value was estimated by steam-distillation method, expressed in units of mg nitrogen/100 g sample(Shi et al. 2020a ). 2.13.4 Bacteriological analysis The total viable counts (TVC) were determined by the agar plate count method (GB/T 4789.2–2003). 2.13.5 Determination of drip loss The rate of drip loss of fish during storage was calculated as follows(Wu et al. 2023 ): $$Drip loss\left(\text{%}\right)=\frac{\text{W}\text{e}\text{i}\text{g}\text{h}\text{t} \text{o}\text{f} \text{f}\text{i}\text{s}\text{h} \text{a}\text{t} \text{p}\text{r}\text{e}\text{d}\text{e}\text{t}\text{e}\text{r}\text{m}\text{i}\text{n}\text{e}\text{d} \text{t}\text{i}\text{m}\text{e}}{\text{I}\text{n}\text{i}\text{t}\text{i}\text{a}\text{l} \text{w}\text{e}\text{i}\text{g}\text{h}\text{t} \text{o}\text{f} \text{f}\text{i}\text{s}\text{h}}\times 100$$ 2.14 Statistical analysis All experiments were done at least triplicate. The data was expressed as mean and standard deviation and processed by SPSS (Version 25.0; SPSS Inc., Chicago, IL, USA). Different letters represent significant differences (p < 0.05). 3. Results and discussion 3.1 The construction of CMS-PMAA-β-CD The CMS-PMAA-β-CD was synthesized by the reaction of CMS grafted with MAA and the crosslinking with β-CD. The stepwise procedure and synthetic mechanism are given in Fig. 1 A. The FTIR spectra of CMS, β-CD, CMS-PMAA, and CMS-PMAA-β-CD are shown in Fig. 1 B. In the FTIR spectra of CMS(Kizil et al. 2002 ), the absorption peak about 3300 cm − 1 corresponded to O-H stretching vibration. The peaks on 753 cm − 1 and 856 cm − 1 corresponded to the skeletal stretching vibration of glucose unit of CMS. The peak on 1080 cm − 1 corresponded to C-O-H bending vibration. The peak on 1026 cm − 1 was attributed to C-O-C stretching vibration. The peak on 1579 cm − 1 corresponded to the C = O stretching vibration of the carbonyl group presented in the CMS. The peak on 1415 cm − 1 was assigned to O-H bending. For the FTIR spectra of CMS-PMAA and CMS-PMAA-β-CD, all the peaks in the fingerprint region (800–1500 cm − 1 ) were similar. The CMS-PMAA shows the new peak on 1257 cm − 1 corresponded to the deformation vibrations of COOH group of PMAA(Güler et al. 2015 ). The strong peak on 1685 cm − 1 was attributed to the stretching vibration of C = O of the carbonyl group presented in the grafted PMAA, indicating the successful grafting of PMAA onto CMS(Haq 2020 ). Compared to that of CMS-PMAA, the characteristic peak of CMS-PMAA-β-CD corresponded to C = O vibration moved from 1685 cm − 1 to 1730 cm − 1 , attributing to the formation of hydrogen bonds between the encapsulated β-CD and the CMS-PMAA(Zhang et al. 2015 ). The absorption peak of O-H stretching vibration shows a red shift and became broad, indicating more O-H introduced by β-CD. The increased intensity of absorption peak on 2932 cm − 1 showed more C-H was introduced by the cross-linking of β-CD. The hydroxyl of CMS-PMAA and β-CD were crosslinked with STMP, a non-toxic crosslinker, by the formation of phosphate esters(Muhammad et al. 2000 ). However, the characteristic absorption peaks inherent to P-O and P-O-C did not appear in the spectra of CMS-PMAA-β-CD, indicating a low degree of crosslinking(Gao et al. 2014 ). The crystalline structure of CMS, CMS-PMAA, β-CD, and CMS-PMAA-β-CD were investigated by XRD patterns (Fig. 1 C). The XRD pattern of CMS shows different diffraction peaks at 14.98°, 17.07°, 17.88°, 23.04°, and 31.60°, which was corresponding to the A-type semi-crystalline nature of the CMS(Haq 2020 ). After modification, the diffraction peaks in CMS-PMAA were lost, indicating the amorphous nature. The weakened diffraction peak indicated the crystalline structure of CMS-PMAA-β-CD was further broken. The typical 1 H NMR spectra of CMS, CMS-PMAA, β-CD, and CMS-PMAA-β-CD are shown in Fig. 1 D. The peak appeared at 4.8 ppm was attributed to D 2 O. The peaks appeared at chemical shifts 5.2–5.4 ppm and 3.5–3.7 ppm corresponded to the proton of carbon atoms of the glucose unit of CMS(Haq 2020 ). After modification, the new peaks appeared at a range from 0.8 to 1.1 ppm were assigned to the protons of C of -CH 3 of PMAA part. The peak area of 0.8–1.1 ppm of CMS-PMAA-β-CD increased, indicating the crosslinking with β-CD induced more -CH 3 . The characteristic peaks of CMS, CMS-PMAA, and CMS-PMAA-β-CD appeared at 5.2–5.4 ppm and 3.5–3.7 ppm didn’t show obvious difference, reflecting the grafting and crosslinking reacted at the hydroxyl in glucose unit, which was consistent with the mechanism of crosslinking using STMP(Lack et al. 2004 ). Above all, the FTIR, XRD, and 1 H NMR spectra proved the successful construction of CMS-PMAA-β-CD. The morphology of CMS, CMS-PMAA, and CMS-PMAA-β-CD are displayed in Fig. 2 . Most CMS granules (Fig. 2 A) showed irregular shapes with frosted surfaces, which was depending on the degree of carboxymethyl of starch. Each CMS-PMAA granule (Fig. 2 B) remained individual. However, the structure of CMS-PMAA presented noticeable changes. The surface became rough and showed partly collapsed. Some CMS-PMAA granules were heavily distorted and appeared as folded cavity structures. After cross-linking, the CMS-PMAA aggregated to form bulk hydrogel (CMS-PMAA-β-CD), and the wall thickness of the cavity structure of granule increased obviously. The irregular shape and different sizes of CMS-PMAA-β-CD were caused by crushing. 3.2 The properties of CMS-PMAA-β-CD The successful synthesis of CMS-PMAA-β-CD has been proved by above results. The properties of CMS-PMAA-β-CD were further investigated. The zeta potentials of CMS, CMS-PMAA, and CMS-PMAA-β-CD at different pH values are shown in Fig. 3 A. All samples presented negative charges due to the ionization of carboxylate groups. The CMS-PMAA had the largest absolute potential value, followed by CMS-PMAA-β-CD and CMS, which was related to the content of carboxy group. The CMS grafted with MAA induced a large content of carboxy groups. The CMS-PMAA crosslinked with β-CD reduced the content of carboxy group, and the formed hydrogen bond between the macromolecular chains inhibited the ionization of carboxy group(Liu and Fan 2002 ). With the increase of pH value, the absolute value of zeta potential increased first and then decreased, which was consistent with the tendency of swelling ratio change (Fig. 3 B). Because the higher absolute zeta potential value reflected the larger electrostatic force, which could lead to the expanding of granule and cause the higher swelling ratio. The difference in swelling ratio at various pH indicated the promising pH-sensibility of CMS-PMAA-β-CD. The thermal stability of CMS, β-CD, CMS-PMAA, and CMS-PMAA-β-CD is revealed by TG (Fig. 3 C) and DTG (Fig. 3 D) analyses. All samples showed the weight loss stage occurred at 50–120 ℃ corresponded to the water evaporation. The CMS showed one weight loss stage was between 222 and 361 ℃, and the DTG max was 288 ℃, which was resulted from the decomposition of the glycosidic linkage of the CMS main chain(Wang et al. 2010 ). After grafted with PMAA, the CMS-PMAA showed three-step weight loss. One weight loss at DTG max 221 ℃ corresponded to the decomposition of the PMAA part from the CMS chain, the second weight loss at DTG max 313 ℃ attributed to the decomposition of the glycosidic linkage of the CMS main chain, and the third weight loss at DTG max 386 ℃ due to the decarboxylation of PMAA(Haq 2020 ). After cross-linking with β-CD, the CMS-PMAA-β-CD showed one weight loss at DTG max 291 ℃, which was similar to the DTG max of CMS. Besides, a minor weight loss stage occurred at DTG max 444 ℃ caused by the decomposition of β-CD crosslinked with the CMS main chain. When the temperature reached 700 ℃, the residue of CMS-PMAA-β-CD was more than others, probably due to the introduction of phosphorus element. 3.3 Encapsulation and release of curcumin in CMS-PMAA-β-CD To achieve the optimal conditions to encapsulate the curcumin, the effects of different embedding process parameters including the mass of curcumin, time, and pH on the loading efficiency and loading ability were investigated (Fig. 4 ). With the increased content of additional curcumin, the loading efficiency decreased, and the loading ability increased first and then decreased (Fig. 4 A). When the mass ratio of curcumin: CMS-PMAA-β-CD was 1:10, the loading ability was the highest. With the increase of reaction time, the loading efficiency and loading ability increased first and then decreased (Fig. 4 B), probably because hydrophilic CMS-PMAA-β-CD was easily swelling, resulting in the destruction of structure if the CMS-PMAA-β-CD was immersed in aqueous ethanol solution at low concentration for a long time(Zhou et al. 2021 ). With the increase of pH of ethanol solution, the loading efficiency and loading ability increased first and then decreased (Fig. 4 C). Because of the pH-sensibility of CMS-PMAA-β-CD, the swelling behavior of CMS-PMAA-β-CD at pH 6–7 induced more curcumin embedded. However, the curcumin was unstable and easily decomposed at an alkalescence condition(Shah et al. 2016 ), resulting in the decreased loading efficiency and loading ability. Based on these results, the optimal encapsulation condition was that the mass ratio of curcumin: CMS-PMAA-β-CD was 1:10, the reaction time was 3 h, and the pH of the ethanol solution was 6.5. The loading efficiency was 80.6%, and the loading ability was 52.47 µg/mg. The FTIR, XRD, and fluorescence spectroscopy of Cur, CMS-PMAA-β-CD, and CMS-PMAA-β-CD-Cur were investigated to verify the interaction between Cur and CMS-PMAA-β-CD. In the FTIR spectrum of CMS-PMAA-β-CD-Cur (Fig. 5 A), the characteristic peaks at 3395 cm − 1 , 1702 cm − 1 , 1583 cm − 1 , 1415 cm − 1 , 1258 cm − 1 , correlated with the typical Cur peaks, corresponded to phenolic -OH stretching vibration, C = O stretching vibration, C-O asymmetric stretching vibration, C-H bending vibration, and C-O aromatic stretching vibration, respectively(Liang et al. 2023 ; Liu et al. 2020 ). This result supported that Cur was successfully encapsulated in CMS-PMAA-β-CD. The XRD pattern of Cur showed sharp diffraction peaks, suggesting high crystallinity (Fig. 5 B). However, the characteristic Cur peaks almost disappeared in CMS-PMAA-β-CD-Cur, indicating that Cur was transformed into an amorphous form. The transformation of the crystalline structure of Cur was mainly attributed to the hydrogen bond and hydrophobic interaction between Cur and CMS-PMAA-β-CD during the embedding process and subsequent evaporation of the ethanol solvent, which hindered the crystallization of Cur(Shi et al. 2020b ; Xiao and Fang 2009 ). Cur with amorphous form had higher internal energy, which was conducive to absorption and utilization(Jog and Burgess 2017 ). The fluorescence spectrum of Cur was blue- or red-shifted according to changes in the polarity of the environment (Fig. 5 C). The difference in the fluorescence spectra of Cur and CMS-PMAA-β-CD-Cur showed that the maximum absorption spectrum of Cur was blue-shifted from 543 to 520 nm after CMS-PMAA-β-CD-Cur formation, which was consistent with other report(Acevedo-Guevara et al. 2018 ). The blue shift was attributed to the hydrogen bond between CMS-PMAA-β-CD and Cur, indicating that Cur entered the hydrophobic cavity of the β-CD(Huong et al. 2011 ). Based on the above results, the encapsulation mechanism of Cur was speculated and is shown in Fig. 5 D. The encapsulation of Cur by CMS-PMAA-β-CD mainly depended on the hydrophobic interactions of β-CD and inter-molecular hydrogen bonding of CMS-PMAA-β-CD. The curcumin release profiles of the CMS-PMAA-β-CD and β-CD are shown in Fig. 6 . For CMS-PMAA-β-CD-Cur, the release rate at various pH reached highest within approximately 120 min. They were about 27.9%, 42.1%, 51.6%, 55.7%, and 56.8% at pH 6.0, 6.5, 7.0, 7.5, and 8.0, respectively. The release behaviors of curcumin at pH 6.0, 6.5, and 7.0 showed obvious differences, indicating CMS-PMAA-β-CD had a narrow pH-sensitive range. The release rate of curcumin was determined by the swelling behavior of CMS-PMAA-β-CD. The larger degree of swelling caused the looser structure of CMS-PMAA-β-CD, which promoted the release of curcumin. The release rates at pH 7.5 and 8.0 were higher than those at pH 6.0 and 6.5, even though the swell ratios of CMS-PMAA-β-CD at corresponding pH were similar, probably caused by the decomposition of curcumin in an alkaline condition(Wang et al. 1997 ). Compared to CMS-PMAA-β-CD-Cur, the release rate of curcumin in β-CD-Cur decreased, and the release amount of curcumin increased. However, there was no pH-sensitivity presented in β-CD-Cur. 3.4 The properties of CMS-PMAA-β-CD-Cur The curcumin is encapsulated by the carrier to enhance stability. With the increase in temperature from 50 ℃ to 110 ℃, the retention of curcumin decreased. The retention of curcumin in CMS-PMAA-β-CD was higher than that of free curcumin at the same temperature. Especially the retention ratio of curcumin in CMS-PMAA-β-CD was 93.86%, while the retention ratio of free curcumin was 74.59% under the treatment at 110 ℃ for 20 min (Fig. 7 A). The results indicated that curcumin encapsulated by CMS-PMAA-β-CD significantly improved the thermal stability of curcumin. The light sensitivity of curcumin is related to its diketone structure, which is prone to degrade into colorless vanillin and ferulic acid under UV light(Liang et al. 2023 ). The percentage of undegraded free curcumin following exposure to UV light (96 h) was 81.43%, while the undegraded curcumin in CMS-PMAA-β-CD was 94.77%, revealing that the curcumin encapsulated by CMS-PMAA-β-CD significantly reduced its photodegradation (Fig. 7 B). The cavity structure in CMS-PMAA-β-CD provided a physical barrier, which prevented the contact of curcumin with UV light. The antioxidant activity of curcumin is attributed to an enol group and two phenolic hydroxyl groups(O’Toole et al. 2016 ). The protons in the phenolic hydroxyl of curcumin can combine with DPPH and ABTS free radicals in ethanol. With the increase in the mass ratio of curcumin: CMS-PMAA-β-CD from 1:40 to 1:5, the DPPH (Fig. 7 C) and ABTS (Fig. 7 D) radical scavenging ability increased first and then decreased, which was consistent with the tendency of loading ability. When the mass ratio of curcumin: CMS-PMAA-β-CD was 1:10, the highest DPPH and ABTS radical scavenging ability of curcumin were 81.54% and 85.56% respectively. While the DPPH and ABTS radical scavenging ability of free curcumin was 21.68% and 9.36% respectively, which were significantly lower than those of CMS-PMAA-β-CD-Cur. Hence, the CMS-PMAA-β-CD improved the solubility and enhanced the dispersibility of curcumin, promoting the exposure of the antioxidant groups of curcumin to the solution, and leading to the enhanced free radical capture(Meng et al. 2021a ). Curcumin has broad-spectrum antibacterial properties, owing to its structural characteristics and the generation of antioxidation products(Zheng et al. 2020 ). Fish spoilage bacteria Shewanella putrefaciens was selected to assess the antibacterial activity of CMS-PMAA-β-CD-Cur (Fig. 8 A). With the increase in the concentration of CMS-PMAA-β-CD-Cur, the bacteriostatic effect enhanced first and then became stable. The minimum inhibitory concentration (MIC) was recorded as the lowest concentration which showed complete inhibition of visible growth of the bacterial pathogens. Hence, the MIC of CMS-PMAA-β-CD-Cur for Shewanella putrefaciens was 0.625 mg/mL. When the concentration of CMS-PMAA-β-CD-Cur reached 10 mg/mL, the inhibition effect on Shewanella putrefaciens showed no obvious enhancement with the further increase of the concentration of CMS-PMAA-β-CD-Cur. The biosafety of preservatives is an essential index for their application in the food areas. The cytotoxicity of CMS-PMAA-β-CD-Cur and curcumin was assessed and the results are shown in Fig. 8 B. The cell viability of L929 incubated with CMS-PMAA-β-CD-Cur and curcumin with the concentration of 10 mg/mL were more than 100%, indicating the good biocompatibility. So CMS-PMAA-β-CD-Cur suspension with the concentration of 10 mg/mL was used for yellow catfish Pelteobagrus fulvidraco preservation. 3.5 The effect of CMS-PMAA-β-CD-Cur on the preservation The preservation effect of CMS-PMAA-β-CD-Cur was investigated by the comparison with the blank control group without any treatment and the CMS-PMAA-β-CD group treated with CMS-PMAA-β-CD, which was determined by the indexes of pH (Fig. 9 A), TVB-N (Fig. 9 B), TVC (Fig. 9 C), and drip loss (Fig. 9 D). The CMS-PMAA-β-CD-Cur was yellow powder, which was lighter colored than curcumin (Fig. S1 ). The appearance of yellow catfish did not show any difference after treated with yellow CMS-PMAA-β-CD-Cur because of the original yellow color of yellow catfish (Fig. S2). Figure 9 A shows pH values decreased first and then increased during the storage period, which was consistent with other research(Ju et al. 2018 ). The decrease in pH was probably due to the lactic acid induced by the glycolysis of glycogen and the phosphoric acid decomposed by ATP. With the extension of storage time, the increase in pH was caused by the volatile compounds such as ammonia, two methylamine, and trimethylamine generated by the protein decomposition. The pH of fish ranged from 6 to 7 was consistent with the pH-sensitive range of CMS-PMAA-β-CD-Cur. With the increase in the pH of fish, the release amount of curcumin in CMS-PMAA-β-CD-Cur increased. The pH values of the CMS-PMAA-β-CD-Cur group were lower than those of other groups. The treatment with CMS-PMAA-β-CD-Cur extended the pH increase of fish for 4 days. Total volatile basic nitrogen (TVB-N) is an important index to determine the spoilage degree of fish, which is composed of nitrogen compounds produced by the interaction of microorganisms and endogenous enzymes. The TVB-N content of yellow catfish was continuously increased during the storage period (Fig. 9 B). The initial TVB-N value of fresh yellow catfish was 6.18 mg/100 g. The TVB-N value increased slowly within 2 days and increased significantly after 2 days, which was consistent with the tendency of pH changes. The TVB-N values of the control group and CMS-PMAA-β-CD group reached the limit content (20 mg/100 g) of freshwater fish set by Chinese National Standards (GB2733-2015) at day 6, while that of CMS-PMAA-β-CD-Cur group was still lower than 20 mg/100 g at day 8. Figure 9 D displays the TVC content of each group. The edible upper limit of TVC in aquatic products is considered as 6 lg CFU/g(Al-Dagal and Bazaraa 1999 ). The initial TVC of fresh yellow catfish was 3.49 lg CFU/g. The increase tendency of TVC was similar to that of TVB-N. The TVC of the CMS-PMAA-β-CD-Cur group was significantly lower than that of other groups at day 8. The results of pH, TVB-N, and TVC indicated the treatment with CMS-PMAA-β-CD-Cur with the concentration of 10 mg/mL extended 2–4 days of shelf-life depending on the inhibition effect on spoilage microorganisms by curcumin but not CMS-PMAA-β-CD. The drip loss is an essential index to evaluate the quality of aquatic products. The freshness of fish affects its drip loss. The drip loss showed a continuous increase during the storage period (Fig. 9 D). The drip loss of the CMS-PMAA-β-CD-Cur group was lowest compared with that of other groups at the same condition, indicating the CMS-PMAA-β-CD-Cur could improve the storage quality of yellow catfish. 4. Conclusion CMS-PMAA-β-CD microgels as a kind of pH-sensitive carrier were successfully fabricated to deliver curcumin. It has a narrow pH-sensitive range from 6-7, which is consistent with the pH change range of fish during chilling storage. The curcumin encapsulated by CMS-PMAA-β-CD shows improved stability, enjoyable antioxidant activity, antibacterial activity, and biocompatibility. The treatment with CMS-PMAA-β-CD-Cur with the concentration of 10 mg/mL extended the shelf-life of yellow catfish for 2-4 days and improved the storage quality of fillets. This work provided a dual-functionalities strategy to construct a pH-sensitive starch-based carrier and offered a promising application in fish preservation. Declarations Funding Declaration This work was supported by the National Key R&D Program of China (2022YFD2100904), the China Agriculture Research System (CARS-46), the Postdoctoral Innovative Practice Position of Hubei Province, and 2020 Annual Key Project of Scientific and Technological R&D of Hubei Agricultural Scientific and Technological Innovation Center (2020-620-000-002-06). Author Contributions Xiaojia Guo: Investigation, Methodology, Writing – original draft, Writing – review & editing, Funding acquisition. Shujin Liu: Methodology; Lanyan Yang: Methodology; Chaoguang Zhao: Methodology. Liu Shi: Investigation. Guangquan Xiong: Investigation, Funding acquisition. Lang Chen: Methodology. Sheng Chen: Methodology. Wenjin Wu: Project Administration, Resources, Supervision, Funding acquisition. Lan Wang: Conceptualization, Supervision, Project administration, Writing – review & editing, Funding acquisition. 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Supplementary Files FBTSupplementaryinformation.docx GA.jpg Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Revision requested 10 Mar, 2024 Reviews received at journal 10 Mar, 2024 Reviews received at journal 10 Feb, 2024 Reviewers agreed at journal 03 Feb, 2024 Reviewers agreed at journal 30 Jan, 2024 Reviewers invited by journal 30 Jan, 2024 Editor assigned by journal 30 Jan, 2024 Submission checks completed at journal 30 Jan, 2024 First submitted to journal 22 Jan, 2024 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-3887107","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":270194523,"identity":"1a40f78e-e6bb-4311-af7d-be9aed528972","order_by":0,"name":"Xiaojia Guo","email":"","orcid":"","institution":"Hubei Academy of Agricultural Sciences","correspondingAuthor":false,"prefix":"","firstName":"Xiaojia","middleName":"","lastName":"Guo","suffix":""},{"id":270194524,"identity":"e4965686-9989-4d08-981b-43ab2f27b19c","order_by":1,"name":"Shujin Liu","email":"","orcid":"","institution":"Hubei Academy of Agricultural Sciences","correspondingAuthor":false,"prefix":"","firstName":"Shujin","middleName":"","lastName":"Liu","suffix":""},{"id":270194525,"identity":"778a8d04-6553-47d9-89d5-0519d65e3000","order_by":2,"name":"Lanyan Yang","email":"","orcid":"","institution":"Hubei Academy of Agricultural Sciences","correspondingAuthor":false,"prefix":"","firstName":"Lanyan","middleName":"","lastName":"Yang","suffix":""},{"id":270194526,"identity":"392fe35b-f51e-48e7-8083-8e821c0af454","order_by":3,"name":"Chaoguang Zhao","email":"","orcid":"","institution":"Hubei Academy of Agricultural Sciences","correspondingAuthor":false,"prefix":"","firstName":"Chaoguang","middleName":"","lastName":"Zhao","suffix":""},{"id":270194527,"identity":"26747020-3a94-47c3-b9be-244c427ed4c3","order_by":4,"name":"Liu Shi","email":"","orcid":"","institution":"Hubei Academy of Agricultural Sciences","correspondingAuthor":false,"prefix":"","firstName":"Liu","middleName":"","lastName":"Shi","suffix":""},{"id":270194528,"identity":"aee115cd-112a-45e2-821a-a4eccfc808d7","order_by":5,"name":"Guangquan Xiong","email":"","orcid":"","institution":"Hubei Academy of Agricultural Sciences","correspondingAuthor":false,"prefix":"","firstName":"Guangquan","middleName":"","lastName":"Xiong","suffix":""},{"id":270194529,"identity":"7b7e3b5d-12de-4b04-bb75-89255bef9414","order_by":6,"name":"Lang Chen","email":"","orcid":"","institution":"Hubei Academy of Agricultural Sciences","correspondingAuthor":false,"prefix":"","firstName":"Lang","middleName":"","lastName":"Chen","suffix":""},{"id":270194530,"identity":"ce30d37e-e18b-4c23-a46a-b8400a14fdef","order_by":7,"name":"Sheng Chen","email":"","orcid":"","institution":"Hubei Academy of Agricultural Sciences","correspondingAuthor":false,"prefix":"","firstName":"Sheng","middleName":"","lastName":"Chen","suffix":""},{"id":270194531,"identity":"c631785c-d776-4f5a-8bcc-bb324bc8a6ee","order_by":8,"name":"Wenjin Wu","email":"","orcid":"","institution":"Hubei Academy of Agricultural Sciences","correspondingAuthor":false,"prefix":"","firstName":"Wenjin","middleName":"","lastName":"Wu","suffix":""},{"id":270194532,"identity":"afe59827-206c-4f7e-bf65-7a1b1730ee74","order_by":9,"name":"Lan Wang","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA8klEQVRIiWNgGAWjYBACPmbmBgiLvbHhwIcKCTl5QlrYmBmhWngOHzw444yFsWEDIS0MMC0SacmHOdsqEhkOENLCztgmzVNzx66BIcfgMOM8iQTGBuaHj27gdxhQy7FnyQ0MZwwOF26TyGNnYDM2ziGkJYftcDIDY4/B4ZnbJIoZG3jYpAlr+QfUwsxjcJh3jkRiwwFitOS2HbZjYGNLOMzbQJyWZuu/fYcTGHiYDxyccUzC2LCZgF/4+Q8fvDnj22F7BvmHzR8+1NTJybM3P3yMTwsQsEgAicT9B2B8ZvzKwUo+AAl7wupGwSgYBaNgxAIAPZxKJnaSZ5UAAAAASUVORK5CYII=","orcid":"","institution":"Hubei Academy of Agricultural Sciences","correspondingAuthor":true,"prefix":"","firstName":"Lan","middleName":"","lastName":"Wang","suffix":""}],"badges":[],"createdAt":"2024-01-22 06:32:11","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-3887107/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-3887107/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":50491965,"identity":"c76fa1cb-de4e-4659-8d5d-4fab8e8eeed7","added_by":"auto","created_at":"2024-02-01 10:34:47","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":121892,"visible":true,"origin":"","legend":"\u003cp\u003e(A) Scheme of the synthesis of CMS-PMAA-β-CD; (B) FTIR spectra, (C) XRD patterns, (D) \u003csup\u003e1\u003c/sup\u003eH NMR spectra of CMS, β-CD, CMS-PMAA, and CMS-PMAA-β-CD.\u003c/p\u003e","description":"","filename":"1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3887107/v1/87cf714e69be667d66daed1a.jpg"},{"id":50492370,"identity":"742c734d-e6bc-4436-8ff0-a15df270d6fc","added_by":"auto","created_at":"2024-02-01 10:42:47","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":54611,"visible":true,"origin":"","legend":"\u003cp\u003eSEM images of (A) CMS, (B) CMS-PMAA, and (C) CMS-PMAA-β-CD.\u003c/p\u003e","description":"","filename":"2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3887107/v1/d79342e8dd29f3219bf1a891.jpg"},{"id":50491968,"identity":"d7d0e7a7-6414-4fcc-a9f8-9474ea864de7","added_by":"auto","created_at":"2024-02-01 10:34:47","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":114510,"visible":true,"origin":"","legend":"\u003cp\u003e(A) Zeta potential of pH profiles of CMS, CMS-PMAA, and CMS-PMAA-β-CD; (B) the swelling ratio of CMS-PMAA-β-CD at different pH values; (C) TGA and (D) DTG curves of CMS, β-CD, CMS-PMAA, and CMS-PMAA-β-CD.\u003c/p\u003e","description":"","filename":"3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3887107/v1/281256934321f5c807b8184c.jpg"},{"id":50492372,"identity":"8fa05648-eb8b-4bae-a596-ff1e41bec615","added_by":"auto","created_at":"2024-02-01 10:42:47","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":46415,"visible":true,"origin":"","legend":"\u003cp\u003eThe effects of curcumin embedding process parameters: (A) the mass ratio of Cur: CMS-PMAA-β-CD; (B) time, and (C) pH on the loading efficiency and loading ability.\u003c/p\u003e","description":"","filename":"4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3887107/v1/7c98ee213e0b76e494349cbc.jpg"},{"id":50493111,"identity":"81450b7f-6ab3-4665-a4fa-c46af96684f9","added_by":"auto","created_at":"2024-02-01 10:50:47","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":124876,"visible":true,"origin":"","legend":"\u003cp\u003e(A) FTIR spectra and (B) XRD patterns of Cur, CMS-PMAA-β-CD, and CMS-PMAA-β-CD-Cur; (C) fluorescence spectroscopy of Cur and CMS-PMAA-β-CD-Cur; (D) schematic diagram of curcumin encapsulation principle.\u003c/p\u003e","description":"","filename":"5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3887107/v1/497d411263242ed35c2c0b41.jpg"},{"id":50491970,"identity":"67d04e6a-b9b1-47a8-acdb-83b1a6773788","added_by":"auto","created_at":"2024-02-01 10:34:47","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":61344,"visible":true,"origin":"","legend":"\u003cp\u003eCurcumin release profiles of (A) CMS-PMAA-β-CD-Cur and (B) β-CD-Cur at different pH.\u003c/p\u003e","description":"","filename":"6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3887107/v1/6510719d0e49813bf5a1e763.jpg"},{"id":50492373,"identity":"835afe26-bb77-4009-8d38-3df559df6ff2","added_by":"auto","created_at":"2024-02-01 10:42:47","extension":"jpg","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":119056,"visible":true,"origin":"","legend":"\u003cp\u003e(A) The thermal stability and (B) photochemical stability of CMS-PMAA-β-CD-Cur and free curcumin; (C) DPPH and (D) ABTS radical scavenging activity of different mass ratios of Cur: CMS-PMAA-β-CD.\u003c/p\u003e","description":"","filename":"7.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3887107/v1/e1d229586ec551682bf8ad84.jpg"},{"id":50491972,"identity":"8c54daa1-0cc4-4752-8a88-6e87a5d2c961","added_by":"auto","created_at":"2024-02-01 10:34:47","extension":"jpg","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":70327,"visible":true,"origin":"","legend":"\u003cp\u003e(A) The inhibition effect of different concentrations of CMS-PMAA-β-CD-Cur on \u003cem\u003eShewanella putrefaciens\u003c/em\u003e; (B) cell viability of L929 incubated with different concentrations of CMS-PMAA-β-CD-Cur and curcumin for 24 h.\u003c/p\u003e","description":"","filename":"8.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3887107/v1/1721a04238e4bf551cc454e4.jpg"},{"id":50491974,"identity":"54ecee72-4c24-4484-9d7a-d6c7eb12ab5f","added_by":"auto","created_at":"2024-02-01 10:34:48","extension":"jpg","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":135171,"visible":true,"origin":"","legend":"\u003cp\u003eThe effects of different treatments on the (A) pH, (B) TVB-N, (C) TVC, and (D) drip loss content of yellow catfish during chilling storage.\u003c/p\u003e","description":"","filename":"9.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3887107/v1/ab4d8f242ba8884a668c0b4d.jpg"},{"id":50493802,"identity":"75887140-6c65-46fa-afa4-408e96c3c3a0","added_by":"auto","created_at":"2024-02-01 10:58:49","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1142969,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-3887107/v1/ac3cccfb-7b36-44be-9514-749610c24000.pdf"},{"id":50491975,"identity":"b253f2f8-4378-49c4-bdf4-d57aec6192f1","added_by":"auto","created_at":"2024-02-01 10:34:48","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":2391936,"visible":true,"origin":"","legend":"","description":"","filename":"FBTSupplementaryinformation.docx","url":"https://assets-eu.researchsquare.com/files/rs-3887107/v1/917e59eb21a83afc8f82090e.docx"},{"id":50491969,"identity":"93576276-a9a8-4039-afe5-75e73d7f1207","added_by":"auto","created_at":"2024-02-01 10:34:47","extension":"jpg","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":80714,"visible":true,"origin":"","legend":"","description":"","filename":"GA.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3887107/v1/c26d7e9085c6df8ed0ea95c2.jpg"}],"financialInterests":"No competing interests reported.","formattedTitle":"The construction of pH-sensitive starch-based carrier to control the delivery of curcumin for preservation","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eFish is a part of a healthy diet and provides essential components such as proteins, vitamins, polyunsaturated fatty acids, and minerals that are necessary for human health. However, fish is spoiled easily due to microbial growth, enzymatic autolysis, and lipid oxidation(Ali et al. 2022). Excellent preservation techniques can effectively prevent microbial spoilage and extend the shelf-life with limited adverse changes in the quality. Traditional preservation methods such as freezing, chilling, drying, salting, and preservative additives also are applied for fish preservation(Gokoglu \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Natural preservatives, such as plant-derived polyphenols, phenolics, flavonoids, and animal-derived lysozymes, lactoferrin, polysaccharides, etc., have become promising alternatives to synthetic preservatives due to the reduction of negative impacts on health(Yu et al. \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Among them, curcumin (Cur), widely used as spices, flavorings, and colorants in the food industry, is a natural polyphenolic bioactive ingredient extracted from dry rhizomes of Curcuma longa(Yilmaz et al. \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). Even though curcumin has both antimicrobial and antioxidant properties, the actual applications of curcumin are often limited by its low water solubility and sensitivity to light, heat, oxygen, enzymes, etc.(Shlar et al. \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). In this case, curcumin is a promising candidate for the development of new carriers to enhance its stability and solubility.\u003c/p\u003e \u003cp\u003eEnvironmental responsive polymeric materials have attracted great attention due to their dynamic structures and properties in response to environmental changes, such as temperature, light, pH, magnetic fields, etc.(Ding et al. \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). Among them, pH-sensitive material is the most representative and widely used in the delivery of drugs or functional factors in biomedical and food areas, which is designed to improve the targetability and uptake of drugs or functional factors(Xu et al. \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). The pH changes during the chilling storage of fish, which decreases first and then increases due to the lactic acid accumulation and protein degradation respectively. However seldom pH-sensitive material is used in the preservation of fish. Even though the controlled release of preservations can achieve long-term preservation.\u003c/p\u003e \u003cp\u003eHerein, we construct a pH-sensitive starch-based carrier to deliver curcumin for the preservation of yellow catfish. Starch is a nontoxic, inexpensive, biocompatible, and renewable natural polymer, which has been used to design carriers(Rodrigues and Emeje \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). Carboxymethyl starch (CMS) is an anionic polymer obtained from the introduction of carboxylic groups in starch structure and has been proposed as a novel pH-sensitive excipient(Assaad et al. \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). The existence of polar functional groups such as carboxylic acid endows the polymer with pH-sensitive properties. The grafting of methacrylic acid (MAA) on CMS modification promotes the pH-sensitive properties because it provides more hydrogen bonds at low pH and enhances electrostatic repulsion at high pH(Saboktakin et al. \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2009\u003c/span\u003e). β-cyclodextrin (β-CD) is a kind of suitable microgel containing a molecular inclusion component(Zhang et al. \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). Based on the unique molecular recognition ability of β-CD and the pH-sensitive nature of CMS grafted with MAA (CMS-PMAA), the microgel (CMS-PMAA-β-CD) obtained by the cross-linking reaction not only possesses the function of including organic compounds but also sensitively responds to pH changes. It is used as a carrier to deliver curcumin for the preservation of yellow catfish \u003cem\u003ePelteobagrus fulvidraco\u003c/em\u003e. The pH-sensitivity, stability, antioxidant activity, antibacterial activity, biocompatibility, and fish preservation effect of carrier-curcumin complex (CMS-PMAA-β-CD-Cur) are evaluated. This work provides a dual-functionalities strategy to construct a pH-sensitive starch-based carrier to deliver curcumin and verifies the preservation effect on fish during chilling storage.\u003c/p\u003e"},{"header":"2. Materials and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Materials\u003c/h2\u003e \u003cp\u003eCarboxymethyl starch sodium (CMS) with DS of 0.2, methacrylic acid (MAA), potassium persulfate (KPS), sodium hydroxide, ethanol, sodium trimetaphosphate (STMP), and β-cyclodextrin (β-CD) with 99% purity were obtained from Sinopharm Chemical Reagent Co., Ltd. Curcumin (Cur) with 98% purity was purchased from Shanghai Macklin Biochemical Technology Co., Ltd. All other chemicals and reagents were purchased from Sigma-Aldrich Trading Co. Ltd. The reagents and solvents without special instruction were of analytical grade and used without further purification.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Synthesis of CMS-PMAA\u003c/h2\u003e \u003cp\u003eThe CMS grafted MAA was prepared according to the method introduced by the previous report with some modifications(Haq \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). CMS (2 g) was dispersed in distilled water (98 mL) in a three-mouth flask with constant mechanical stirring. The resulting solution was gelatinized at 90 ℃ for 30 min and then cooled at 70 ℃. KPS solution (20 mL, 0.04 g/mL) used as the initiator to activate starch hydroxyl groups was added to the flask and incubated for 30 min. Then the solution mixed with PMAA (10 mL) and NaOH (2 mL, 0.5 g/mL) solution was slowly added to the flask and reacted for 2 h. The whole reaction occurred in an N\u003csub\u003e2\u003c/sub\u003e atmosphere. Afterward, the reaction mixture was cooled to room temperature and washed with deionized water and ethanol in turns three times. The precipitation was collected and freeze-dried to obtain CMS-PMAA.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3 Preparation of CMS-PMAA-β-CD\u003c/h2\u003e \u003cp\u003eThe CMS-PMAA was crosslinked with β-CD using STMP as the crosslinking agent according to the method described by the previous report with slight modifications(Zhang et al. \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). CMS-PMAA (10 g) and β-CD (1 g) were dissolved in NaOH solution (50 mL, pH 9). STMP (1 g) was slowly added to the mixture with thorough stirring. Then the mixture was heated at 40 ℃ for 1 h without stirring to form the gel. The whole gel was crushed with a spatula and washed with deionized water, ethanol, and acetone in turns three times. After freeze-drying, the gel was further crushed by a crusher and passed through a sieve of 200 mesh to obtain CMS-PMAA-β-CD.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4 Loading of curcumin into CMS-PMAA-β-CD\u003c/h2\u003e \u003cp\u003eCMS-PMAA-β-CD solution (100 mL) with predetermined concentration (1, 2, 4, 6, 8 mg/mL) was gelatinized for 30 min in the boiling water bath and then cooled at 40 ℃. The pH value of CMS-PMAA-β-CD solution was adjusted to predetermined pH (6.0, 6.5, 7.0, 7.5, 8.0) by adding citric acid/phosphate buffer (0.1 mol/L). Then curcumin/ethanol solution (8 mL, 2.5 mg/mL) was slowly added and stirred for predetermined time (1, 2, 3, 4 h) in the dark. The ethanol was removed by rotary evaporation and the unembedded curcumin was removed by centrifugation at 1000 r/min for 10 min(Hu et al. \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). The supernatant was collected and freeze-dried to complete the loading process. Among them, CMS-PMAA-β-CD solution (2 mg/mL, pH 6.5) and reaction for 3 h were the optimal loading parameters to fabricate CMS-PMAA-β-CD-Cur.\u003c/p\u003e \u003cp\u003eAs the control, curcumin/ethanol solution (8 mL, 2.5 mg/mL) was slowly added to β-CD solution (100 mL, 2 mg/mL) and stirred for 3 h in the dark to obtain β-CD-Cur.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e2.5 Characterization\u003c/h2\u003e \u003cp\u003eThe morphology of the samples was performed on a scanning electron microscope (SEM, SU8100, Hitachi, Japan) with an electron accelerating voltage of 10 kV. Fourier transform infrared (FT-IR) spectra were recorded on Nicolet iS50 FTIR spectrometer (Thermo-Fisher, USA) using the KBr-disk method. X-ray diffractometry (XRD) was performed on a D8-ADVANCE X-Ray diffractometer (Bruker, Germany) with Cu-Kα radiation source (λ\u0026thinsp;=\u0026thinsp;1.5405 \u0026Aring;) at 40 kV and 15 mA. All diffraction peaks were determined in a 2θ range of 4\u0026ndash;40\u0026ordm; at a scan speed of 2\u0026ordm;/min. Hydrogen Nuclear magnetic resonance (\u003csup\u003e1\u003c/sup\u003eH NMR) spectra were recorded on a 400M spectrometer (Bruker, Germany) operating at 400 MHz. The CMS-PMAA-β-CD was dissolved in DMSO-D\u003csub\u003e2\u003c/sub\u003eO (20 mg/mL), and the other samples were dispersed in D\u003csub\u003e2\u003c/sub\u003eO (20 mg/mL). The zeta potential was measured by Zeta-sizer Nano ZSE (Malvern, UK). Thermogravimetry (TG) analysis and derivative thermal gravimetric (DTG) analysis experiments were performed on a Simultaneous Thermal Analysis instrument (Mettler Toledo, Switzerland) in nitrogen flow with a heating rate of 10 ℃/min and a temperature range from room temperature to 800 ℃. The binding between Cur and CMS-PMAA-β-CD was determined using fluorescence spectrophotometry F-7000 (Hitachi, Tokyo, Japan). The excitation wavelength was 425 nm, and the emission spectra were recorded from 450 to 650 nm with slit widths of 5 nm.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e2.6 Determination of swelling ratio\u003c/h2\u003e \u003cp\u003eThe CMS-PMAA-β-CD (0.1 g) was immersed in various citric acid/phosphate buffer solutions (25 mL, 0.1 mol/L) with predetermined pH (6.0, 6.5, 7.0, 7.5, 8.0) at 25 ℃ for 24 h. Then the solution was centrifugated at 2000 r/min for 10 min to remove the excess water. The weight of the swollen sample was measured. The swelling ratio was calculated according to the following relation(Mahkam \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2010\u003c/span\u003e):\u003cdiv id=\"Equa\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equa\" name=\"EquationSource\"\u003e\n$$Swelling ratio\\left(\\%\\right)=\\frac{{W}_{s}-{\\text{W}}_{d}}{{W}_{s}}\\times 100$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eWhere, W\u003csub\u003es\u003c/sub\u003e and W\u003csub\u003ed\u003c/sub\u003e represent the weight of swollen sample and dried samples, respectively.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e2.7 Loading efficiency and loading ability of curcumin\u003c/h2\u003e \u003cdiv id=\"Sec10\" class=\"Section3\"\u003e \u003ch2\u003e2.7.1 Loading efficiency\u003c/h2\u003e \u003cp\u003eIn section \u003cspan refid=\"Sec6\" class=\"InternalRef\"\u003e2.4\u003c/span\u003e, the unembedded curcumin precipitate was collected by centrifugation. Then the precipitate was dissolved in 100% ethanol (100 mL). Its absorbance was measured by a UV-vis spectrophotometer at 425 nm to determine the content of unembedded curcumin, which was calculated by the standard curve of curcumin-absorbance. The total weight of curcumin added in the loading process was 20 mg. The Loading efficiency was calculated by the following formula(Xiao-Min et al. 2019):\u003cdiv id=\"Equb\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equb\" name=\"EquationSource\"\u003e\n$$Loading efficiency\\left(\\%\\right)=(1-\\frac{\\text{A}\\text{m}\\text{o}\\text{u}\\text{n}\\text{t} \\text{o}\\text{f} \\text{u}\\text{n}\\text{e}\\text{m}\\text{b}\\text{e}\\text{d}\\text{d}\\text{e}\\text{d} \\text{c}\\text{u}\\text{r}\\text{c}\\text{u}\\text{m}\\text{i}\\text{n}}{\\text{T}\\text{o}\\text{t}\\text{a}\\text{l} \\text{w}\\text{e}\\text{i}\\text{g}\\text{h}\\text{t} \\text{o}\\text{f} \\text{c}\\text{u}\\text{r}\\text{c}\\text{u}\\text{m}\\text{i}\\text{n}})\\times 100$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section3\"\u003e \u003ch2\u003e2.7.2 Loading ability\u003c/h2\u003e \u003cp\u003eCMS-PMAA-β-CD-Cur (0.50 mg) was dispersed in 80% (v/v) ethanol (10 mL), and then the solution was dealt with ultrasonic for 10 min and centrifugated at 3500 r/min for 10 min. The absorbance of the supernatant was measured by a UV-vis spectrophotometer at 425 nm to obtain the content of embedded curcumin, which was determined by the standard curve of curcumin-absorbance. The loading ability was calculated by the following formula(Xiao-Min et al. 2019):\u003cdiv id=\"Equc\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equc\" name=\"EquationSource\"\u003e\n$$Loading ability(ug/mg)=\\frac{\\text{A}\\text{m}\\text{o}\\text{u}\\text{n}\\text{t} \\text{o}\\text{f} \\text{e}\\text{m}\\text{b}\\text{e}\\text{d}\\text{d}\\text{e}\\text{d} \\text{c}\\text{u}\\text{r}\\text{c}\\text{u}\\text{m}\\text{i}\\text{n}}{\\text{T}\\text{o}\\text{t}\\text{a}\\text{l} \\text{w}\\text{e}\\text{i}\\text{g}\\text{h}\\text{t} \\text{o}\\text{f} \\text{C}\\text{M}\\text{S}-\\text{P}\\text{M}\\text{A}\\text{A}-{\\beta }-\\text{C}\\text{D}-\\text{C}\\text{u}\\text{r}}$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003e2.8 The release of curcumin\u003c/h2\u003e \u003cp\u003eThe sample (0.5 g) was dispersed in 80% (v/v) ethanol (10 mL). The obtained suspension (5 mL) placed in a dialysis bag (8\u0026ndash;12 kDa) was put in phosphate-buffered saline (PBS, 100 mL, 0.1 mol/L, pH 6.0, 6.5, 7.0, 7.5, 8.0) containing 1 wt.% Tween 80. The process occurred in 37 ℃ with constant stirring. PBS (5 mL) was withdrawn and replaced with fresh PBS (5 mL) at predetermined time. Then its absorbance value was read at 425 nm using a UV-vis spectrophotometer to determine the released curcumin. The total amount of curcumin in sample was calculated by loading ability. The cumulative release of curcumin from the sample was calculated as follows:\u003cdiv id=\"Equd\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equd\" name=\"EquationSource\"\u003e\n$$Curcumin release\\left(\\text{%}\\right)=\\frac{\\text{A}\\text{m}\\text{o}\\text{u}\\text{n}\\text{t} \\text{o}\\text{f} \\text{r}\\text{e}\\text{l}\\text{e}\\text{a}\\text{s}\\text{e}\\text{d} \\text{c}\\text{u}\\text{r}\\text{c}\\text{u}\\text{m}\\text{i}\\text{n} }{\\text{T}\\text{o}\\text{t}\\text{a}\\text{l} \\text{a}\\text{m}\\text{o}\\text{u}\\text{n}\\text{t} \\text{o}\\text{f} \\text{c}\\text{u}\\text{r}\\text{c}\\text{u}\\text{m}\\text{i}\\text{n} \\text{i}\\text{n} \\text{s}\\text{a}\\text{m}\\text{p}\\text{l}\\text{e}}\\times 100$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003e2.9 Stability of curcumin\u003c/h2\u003e \u003cdiv id=\"Sec14\" class=\"Section3\"\u003e \u003ch2\u003e2.9.1 Thermal stability\u003c/h2\u003e \u003cp\u003eThe sample (0.5 g) placed in a transparent glass vial was put in the hot water bath at predetermined temperature (50, 70, 90, 110 ℃) for 20 min. Subsequently, the heated sample was immediately cooled at 25 ℃ using an ice water bath(Meng et al. \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2021b\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section3\"\u003e \u003ch2\u003e2.9.2 Photochemical stability\u003c/h2\u003e \u003cp\u003eThe sample (0.5 g) was evenly placed in a transparent glass vial and exposed to a UV light (365 nm, 10 W) for predetermined time (24, 48, 72, 96 h). The distance between the sample and UV light was 10 cm.\u003c/p\u003e \u003cp\u003eAfter treatment, the retained curcumin in the sample was determined according to the method described in 2.7.2. The total amount of curcumin in sample was calculated by loading ability. The retention rate of curcumin was calculated by using the following equations(Sun et al. \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2017\u003c/span\u003e):\u003cdiv id=\"Eque\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Eque\" name=\"EquationSource\"\u003e\n$$Retention rate\\left(\\text{%}\\right)=\\frac{\\text{A}\\text{m}\\text{o}\\text{u}\\text{n}\\text{t} \\text{o}\\text{f} \\text{r}\\text{e}\\text{t}\\text{a}\\text{i}\\text{n}\\text{e}\\text{d} \\text{c}\\text{u}\\text{r}\\text{c}\\text{u}\\text{m}\\text{i}\\text{n}}{\\text{T}\\text{o}\\text{t}\\text{a}\\text{l} \\text{a}\\text{m}\\text{o}\\text{u}\\text{n}\\text{t} \\text{o}\\text{f} \\text{c}\\text{u}\\text{r}\\text{c}\\text{u}\\text{m}\\text{i}\\text{n} \\text{i}\\text{n} \\text{s}\\text{a}\\text{m}\\text{p}\\text{l}\\text{e}}\\times 100$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec16\" class=\"Section2\"\u003e \u003ch2\u003e2.10 Antioxidant activity\u003c/h2\u003e \u003cdiv id=\"Sec17\" class=\"Section3\"\u003e \u003ch2\u003e2.10.1 DPPH radical scavenging activity\u003c/h2\u003e \u003cp\u003eThe sample (0.1 g) dispersed in deionized water (10 mL) was added to DPPH-ethanol solution (10 mL, 0.2 mol/L) and mixed thoroughly. The mixed solution was placed in the dark for 30 min. The absorbance (A\u003csub\u003et\u003c/sub\u003e) of the above solutions was measured at 517 nm using the UV-vis spectrophotometer. The free radical scavenging activity of the sample was calculated as follows(Stojadinovic et al. \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2013\u003c/span\u003e):\u003cdiv id=\"Equf\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equf\" name=\"EquationSource\"\u003e\n$$DPPH scavenging activity\\left(\\text{%}\\right)=(1-\\frac{{\\text{A}}_{t}-{\\text{A}}_{b}}{{\\text{A}}_{c}})\\times 100$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eWhere the A\u003csub\u003eb\u003c/sub\u003e was the absorbance of the mixed solution of 10 mL sample solution and 10 mL ethanol, and the A\u003csub\u003ec\u003c/sub\u003e was the absorbance of the mixed solution of 10 mL deionized water and 10 mL DPPH-ethanol solution.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec18\" class=\"Section3\"\u003e \u003ch2\u003e2.10.2 ABTS radical scavenging activity\u003c/h2\u003e \u003cp\u003eABTS free radicals stock solution was produced by mixing ABTS (14.4 mmol/L) with potassium persulfate (5.2 mmol/L) in a ratio of 1:1 (v/v). The stock solution was placed in the dark at room temperature for 16 h. The ABTS working solution with an absorbance value of 0.70 at 734 nm was obtained by diluting the stock solution with PBS solution (0.01 mol/L, pH 7.4). The sample (1 mL, 10 mg/mL) was mixed with ABTS working solution (4.5 mL) and reacted for 6 min in the dark. The ABTS free radical scavenging capability of sample was calculated as follows(Bhoopathy et al. \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2020\u003c/span\u003e):\u003cdiv id=\"Equg\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equg\" name=\"EquationSource\"\u003e\n$$ABTS scavenging activity\\left(\\text{%}\\right)=\\frac{{\\text{A}}_{d}-{\\text{A}}_{s}}{{\\text{A}}_{d}}\\times 100$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eWhere the A\u003csub\u003ed\u003c/sub\u003e was the absorbance of the mixed solution of 1 mL PBS and 4.5 mL ABTS working solution at 734 nm, and A\u003csub\u003es\u003c/sub\u003e was the absorbance of the test samples at 734 nm.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec19\" class=\"Section2\"\u003e \u003ch2\u003e2.11 In vitro antibacterial test\u003c/h2\u003e \u003cp\u003eFish spoilage bacteria \u003cem\u003eShewanella putrefaciens\u003c/em\u003e was selected to assess the antibacterial activity of CMS-PMAA-β-CD-Cur. After sterilization by UV irradiation for 2 h, the sample was dispersed in physiological saline to obtain the suspension with the concentration of 10 mg/mL. A prepared test solution was mixed with nutrient agar medium to yield predetermined concentration. The bacterial suspension (100 \u0026micro;L, 10\u003csup\u003e6\u003c/sup\u003e CFU/mL) and test solution (50 \u0026micro;L) were seeded into a 96-well tissue culture plate and incubated at 37 ℃ for 10 h. The sterile water as the test solution was the blank control. The absorbance values (OD 600) were measured at a test wavelength of 600 nm.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec20\" class=\"Section2\"\u003e \u003ch2\u003e2.12 Cytotoxicity assay\u003c/h2\u003e \u003cp\u003eCell viability performance of CMS-PMAA-β-CD-Cur was tested by MTT assay using mouse lung fibroblasts (L929). The samples with the predetermined weight (2.5, 5, 10 mg) were immersed in MEM medium (1 mL) at 4 ℃ for 24 h to prepare extracted solutions. L929 fibroblasts were seeded into a 96-well tissue culture plate at a density of 2 \u0026times; 10\u003csup\u003e3\u003c/sup\u003e cells/well and incubated in a humidified 37 ℃, 5% CO\u003csub\u003e2\u003c/sub\u003e atmosphere for 24 h. Then the culture medium was replaced with the prepared extraction medium and continued incubation for 24 h. The blank tissue culture plates were served as the control. For the cell viability determination, the medium was replaced with MTT/MEM solution (100 \u0026micro;L, 0.5 mg/mL) and incubated for 4 h. Then MTT/MEM solution was replaced with dimethyl sulfoxide (DMSO, 150 \u0026micro;L). The OD value of the obtained solution was measured at 490 nm by an enzyme-linked immune absorbent assay reader (SpectraMax iD5, China). The cell viability of sample was calculated as follows:\u003cdiv id=\"Equh\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equh\" name=\"EquationSource\"\u003e\n$$Cell viability\\left(\\text{%}\\right)=\\frac{{\\text{O}\\text{D}}_{Sample}-{\\text{O}\\text{D}}_{Blank}}{{\\text{O}\\text{D}}_{Control}-{\\text{O}\\text{D}}_{Blank}}\\times 100$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec21\" class=\"Section2\"\u003e \u003ch2\u003e2.13 Fish preservation trial\u003c/h2\u003e \u003c/div\u003e \u003cdiv id=\"Sec22\" class=\"Section2\"\u003e \u003ch2\u003e2.13.1 Preparation of fish samples\u003c/h2\u003e \u003cp\u003e All animal assays were carried out abided by the standard of the National Regulation of China for the Care and Use of Laboratory Animals complied with the National Research Council's Guide for the Care and Use of Laboratory Animals. The live yellow catfish \u003cem\u003ePelteobagrus fulvidraco\u003c/em\u003e (250\u0026thinsp;\u0026plusmn;\u0026thinsp;50 g; N\u0026thinsp;=\u0026thinsp;105) were purchased from a local market (Wuhan, China). All samples were beheaded, eviscerated, rinsed with running water, and placed on ice. The samples were divided into three groups: (1) samples were sprayed with distilled water as the control; (2) samples were sprayed with 10 mg/mL CMS-PMAA-β-CD-Cur solution; (3) samples were sprayed with 10 mg/mL CMS-PMAA-β-CD solution. After being drained, all samples were individually packed in a vacuum bag and pumped to a vacuum state. Each treatment was analyzed at a 2-day interval during 12 days(Lan et al. \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2022\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec23\" class=\"Section2\"\u003e \u003ch2\u003e2.13.2 Determination of pH values\u003c/h2\u003e \u003cp\u003eFillet samples (1 g) were homogenized in distilled water (9 mL) for 20 min at 4 ℃. The pH of the supernatant of the solution was tested.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec24\" class=\"Section2\"\u003e \u003ch2\u003e2.13.3 Determination of TVB-N\u003c/h2\u003e \u003cp\u003eThe total volatile basic nitrogen (TVB-N) value was estimated by steam-distillation method, expressed in units of mg nitrogen/100 g sample(Shi et al. \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2020a\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec25\" class=\"Section2\"\u003e \u003ch2\u003e2.13.4 Bacteriological analysis\u003c/h2\u003e \u003cp\u003eThe total viable counts (TVC) were determined by the agar plate count method (GB/T 4789.2\u0026ndash;2003).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec26\" class=\"Section2\"\u003e \u003ch2\u003e2.13.5 Determination of drip loss\u003c/h2\u003e \u003cp\u003eThe rate of drip loss of fish during storage was calculated as follows(Wu et al. \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2023\u003c/span\u003e):\u003cdiv id=\"Equi\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equi\" name=\"EquationSource\"\u003e\n$$Drip loss\\left(\\text{%}\\right)=\\frac{\\text{W}\\text{e}\\text{i}\\text{g}\\text{h}\\text{t} \\text{o}\\text{f} \\text{f}\\text{i}\\text{s}\\text{h} \\text{a}\\text{t} \\text{p}\\text{r}\\text{e}\\text{d}\\text{e}\\text{t}\\text{e}\\text{r}\\text{m}\\text{i}\\text{n}\\text{e}\\text{d} \\text{t}\\text{i}\\text{m}\\text{e}}{\\text{I}\\text{n}\\text{i}\\text{t}\\text{i}\\text{a}\\text{l} \\text{w}\\text{e}\\text{i}\\text{g}\\text{h}\\text{t} \\text{o}\\text{f} \\text{f}\\text{i}\\text{s}\\text{h}}\\times 100$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec27\" class=\"Section2\"\u003e \u003ch2\u003e2.14 Statistical analysis\u003c/h2\u003e \u003cp\u003eAll experiments were done at least triplicate. The data was expressed as mean and standard deviation and processed by SPSS (Version 25.0; SPSS Inc., Chicago, IL, USA). Different letters represent significant differences (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05).\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results and discussion","content":"\u003cdiv id=\"Sec29\" class=\"Section2\"\u003e \u003ch2\u003e3.1 The construction of CMS-PMAA-β-CD\u003c/h2\u003e \u003cp\u003eThe CMS-PMAA-β-CD was synthesized by the reaction of CMS grafted with MAA and the crosslinking with β-CD. The stepwise procedure and synthetic mechanism are given in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eA. The FTIR spectra of CMS, β-CD, CMS-PMAA, and CMS-PMAA-β-CD are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eB. In the FTIR spectra of CMS(Kizil et al. \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2002\u003c/span\u003e), the absorption peak about 3300 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e corresponded to O-H stretching vibration. The peaks on 753 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 856 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e corresponded to the skeletal stretching vibration of glucose unit of CMS. The peak on 1080 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e corresponded to C-O-H bending vibration. The peak on 1026 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e was attributed to C-O-C stretching vibration. The peak on 1579 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e corresponded to the C\u0026thinsp;=\u0026thinsp;O stretching vibration of the carbonyl group presented in the CMS. The peak on 1415 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e was assigned to O-H bending. For the FTIR spectra of CMS-PMAA and CMS-PMAA-β-CD, all the peaks in the fingerprint region (800\u0026ndash;1500 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) were similar. The CMS-PMAA shows the new peak on 1257 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e corresponded to the deformation vibrations of COOH group of PMAA(G\u0026uuml;ler et al. \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). The strong peak on 1685 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e was attributed to the stretching vibration of C\u0026thinsp;=\u0026thinsp;O of the carbonyl group presented in the grafted PMAA, indicating the successful grafting of PMAA onto CMS(Haq \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Compared to that of CMS-PMAA, the characteristic peak of CMS-PMAA-β-CD corresponded to C\u0026thinsp;=\u0026thinsp;O vibration moved from 1685 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e to 1730 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, attributing to the formation of hydrogen bonds between the encapsulated β-CD and the CMS-PMAA(Zhang et al. \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). The absorption peak of O-H stretching vibration shows a red shift and became broad, indicating more O-H introduced by β-CD. The increased intensity of absorption peak on 2932 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e showed more C-H was introduced by the cross-linking of β-CD. The hydroxyl of CMS-PMAA and β-CD were crosslinked with STMP, a non-toxic crosslinker, by the formation of phosphate esters(Muhammad et al. \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2000\u003c/span\u003e). However, the characteristic absorption peaks inherent to P-O and P-O-C did not appear in the spectra of CMS-PMAA-β-CD, indicating a low degree of crosslinking(Gao et al. \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2014\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe crystalline structure of CMS, CMS-PMAA, β-CD, and CMS-PMAA-β-CD were investigated by XRD patterns (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eC). The XRD pattern of CMS shows different diffraction peaks at 14.98\u0026deg;, 17.07\u0026deg;, 17.88\u0026deg;, 23.04\u0026deg;, and 31.60\u0026deg;, which was corresponding to the A-type semi-crystalline nature of the CMS(Haq \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). After modification, the diffraction peaks in CMS-PMAA were lost, indicating the amorphous nature. The weakened diffraction peak indicated the crystalline structure of CMS-PMAA-β-CD was further broken.\u003c/p\u003e \u003cp\u003eThe typical \u003csup\u003e1\u003c/sup\u003eH NMR spectra of CMS, CMS-PMAA, β-CD, and CMS-PMAA-β-CD are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eD. The peak appeared at 4.8 ppm was attributed to D\u003csub\u003e2\u003c/sub\u003eO. The peaks appeared at chemical shifts 5.2\u0026ndash;5.4 ppm and 3.5\u0026ndash;3.7 ppm corresponded to the proton of carbon atoms of the glucose unit of CMS(Haq \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). After modification, the new peaks appeared at a range from 0.8 to 1.1 ppm were assigned to the protons of C of -CH\u003csub\u003e3\u003c/sub\u003e of PMAA part. The peak area of 0.8\u0026ndash;1.1 ppm of CMS-PMAA-β-CD increased, indicating the crosslinking with β-CD induced more -CH\u003csub\u003e3\u003c/sub\u003e. The characteristic peaks of CMS, CMS-PMAA, and CMS-PMAA-β-CD appeared at 5.2\u0026ndash;5.4 ppm and 3.5\u0026ndash;3.7 ppm didn\u0026rsquo;t show obvious difference, reflecting the grafting and crosslinking reacted at the hydroxyl in glucose unit, which was consistent with the mechanism of crosslinking using STMP(Lack et al. \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2004\u003c/span\u003e). Above all, the FTIR, XRD, and \u003csup\u003e1\u003c/sup\u003eH NMR spectra proved the successful construction of CMS-PMAA-β-CD.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe morphology of CMS, CMS-PMAA, and CMS-PMAA-β-CD are displayed in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. Most CMS granules (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eA) showed irregular shapes with frosted surfaces, which was depending on the degree of carboxymethyl of starch. Each CMS-PMAA granule (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eB) remained individual. However, the structure of CMS-PMAA presented noticeable changes. The surface became rough and showed partly collapsed. Some CMS-PMAA granules were heavily distorted and appeared as folded cavity structures. After cross-linking, the CMS-PMAA aggregated to form bulk hydrogel (CMS-PMAA-β-CD), and the wall thickness of the cavity structure of granule increased obviously. The irregular shape and different sizes of CMS-PMAA-β-CD were caused by crushing.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec30\" class=\"Section2\"\u003e \u003ch2\u003e3.2 The properties of CMS-PMAA-β-CD\u003c/h2\u003e \u003cp\u003eThe successful synthesis of CMS-PMAA-β-CD has been proved by above results. The properties of CMS-PMAA-β-CD were further investigated. The zeta potentials of CMS, CMS-PMAA, and CMS-PMAA-β-CD at different pH values are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eA. All samples presented negative charges due to the ionization of carboxylate groups. The CMS-PMAA had the largest absolute potential value, followed by CMS-PMAA-β-CD and CMS, which was related to the content of carboxy group. The CMS grafted with MAA induced a large content of carboxy groups. The CMS-PMAA crosslinked with β-CD reduced the content of carboxy group, and the formed hydrogen bond between the macromolecular chains inhibited the ionization of carboxy group(Liu and Fan \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2002\u003c/span\u003e). With the increase of pH value, the absolute value of zeta potential increased first and then decreased, which was consistent with the tendency of swelling ratio change (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eB). Because the higher absolute zeta potential value reflected the larger electrostatic force, which could lead to the expanding of granule and cause the higher swelling ratio. The difference in swelling ratio at various pH indicated the promising pH-sensibility of CMS-PMAA-β-CD.\u003c/p\u003e \u003cp\u003eThe thermal stability of CMS, β-CD, CMS-PMAA, and CMS-PMAA-β-CD is revealed by TG (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eC) and DTG (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eD) analyses. All samples showed the weight loss stage occurred at 50\u0026ndash;120 ℃ corresponded to the water evaporation. The CMS showed one weight loss stage was between 222 and 361 ℃, and the DTG\u003csub\u003emax\u003c/sub\u003e was 288 ℃, which was resulted from the decomposition of the glycosidic linkage of the CMS main chain(Wang et al. \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2010\u003c/span\u003e). After grafted with PMAA, the CMS-PMAA showed three-step weight loss. One weight loss at DTG\u003csub\u003emax\u003c/sub\u003e 221 ℃ corresponded to the decomposition of the PMAA part from the CMS chain, the second weight loss at DTG\u003csub\u003emax\u003c/sub\u003e 313 ℃ attributed to the decomposition of the glycosidic linkage of the CMS main chain, and the third weight loss at DTG\u003csub\u003emax\u003c/sub\u003e 386 ℃ due to the decarboxylation of PMAA(Haq \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). After cross-linking with β-CD, the CMS-PMAA-β-CD showed one weight loss at DTG\u003csub\u003emax\u003c/sub\u003e 291 ℃, which was similar to the DTG\u003csub\u003emax\u003c/sub\u003e of CMS. Besides, a minor weight loss stage occurred at DTG\u003csub\u003emax\u003c/sub\u003e 444 ℃ caused by the decomposition of β-CD crosslinked with the CMS main chain. When the temperature reached 700 ℃, the residue of CMS-PMAA-β-CD was more than others, probably due to the introduction of phosphorus element.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec31\" class=\"Section2\"\u003e \u003ch2\u003e3.3 Encapsulation and release of curcumin in CMS-PMAA-β-CD\u003c/h2\u003e \u003cp\u003eTo achieve the optimal conditions to encapsulate the curcumin, the effects of different embedding process parameters including the mass of curcumin, time, and pH on the loading efficiency and loading ability were investigated (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). With the increased content of additional curcumin, the loading efficiency decreased, and the loading ability increased first and then decreased (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eA). When the mass ratio of curcumin: CMS-PMAA-β-CD was 1:10, the loading ability was the highest. With the increase of reaction time, the loading efficiency and loading ability increased first and then decreased (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eB), probably because hydrophilic CMS-PMAA-β-CD was easily swelling, resulting in the destruction of structure if the CMS-PMAA-β-CD was immersed in aqueous ethanol solution at low concentration for a long time(Zhou et al. \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). With the increase of pH of ethanol solution, the loading efficiency and loading ability increased first and then decreased (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eC). Because of the pH-sensibility of CMS-PMAA-β-CD, the swelling behavior of CMS-PMAA-β-CD at pH 6\u0026ndash;7 induced more curcumin embedded. However, the curcumin was unstable and easily decomposed at an alkalescence condition(Shah et al. \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2016\u003c/span\u003e), resulting in the decreased loading efficiency and loading ability. Based on these results, the optimal encapsulation condition was that the mass ratio of curcumin: CMS-PMAA-β-CD was 1:10, the reaction time was 3 h, and the pH of the ethanol solution was 6.5. The loading efficiency was 80.6%, and the loading ability was 52.47 \u0026micro;g/mg.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe FTIR, XRD, and fluorescence spectroscopy of Cur, CMS-PMAA-β-CD, and CMS-PMAA-β-CD-Cur were investigated to verify the interaction between Cur and CMS-PMAA-β-CD. In the FTIR spectrum of CMS-PMAA-β-CD-Cur (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eA), the characteristic peaks at 3395 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, 1702 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, 1583 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, 1415 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, 1258 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, correlated with the typical Cur peaks, corresponded to phenolic -OH stretching vibration, C\u0026thinsp;=\u0026thinsp;O stretching vibration, C-O asymmetric stretching vibration, C-H bending vibration, and C-O aromatic stretching vibration, respectively(Liang et al. \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; Liu et al. \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). This result supported that Cur was successfully encapsulated in CMS-PMAA-β-CD. The XRD pattern of Cur showed sharp diffraction peaks, suggesting high crystallinity (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eB). However, the characteristic Cur peaks almost disappeared in CMS-PMAA-β-CD-Cur, indicating that Cur was transformed into an amorphous form. The transformation of the crystalline structure of Cur was mainly attributed to the hydrogen bond and hydrophobic interaction between Cur and CMS-PMAA-β-CD during the embedding process and subsequent evaporation of the ethanol solvent, which hindered the crystallization of Cur(Shi et al. \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2020b\u003c/span\u003e; Xiao and Fang \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2009\u003c/span\u003e). Cur with amorphous form had higher internal energy, which was conducive to absorption and utilization(Jog and Burgess \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). The fluorescence spectrum of Cur was blue- or red-shifted according to changes in the polarity of the environment (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eC). The difference in the fluorescence spectra of Cur and CMS-PMAA-β-CD-Cur showed that the maximum absorption spectrum of Cur was blue-shifted from 543 to 520 nm after CMS-PMAA-β-CD-Cur formation, which was consistent with other report(Acevedo-Guevara et al. \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). The blue shift was attributed to the hydrogen bond between CMS-PMAA-β-CD and Cur, indicating that Cur entered the hydrophobic cavity of the β-CD(Huong et al. \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). Based on the above results, the encapsulation mechanism of Cur was speculated and is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eD. The encapsulation of Cur by CMS-PMAA-β-CD mainly depended on the hydrophobic interactions of β-CD and inter-molecular hydrogen bonding of CMS-PMAA-β-CD.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe curcumin release profiles of the CMS-PMAA-β-CD and β-CD are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e. For CMS-PMAA-β-CD-Cur, the release rate at various pH reached highest within approximately 120 min. They were about 27.9%, 42.1%, 51.6%, 55.7%, and 56.8% at pH 6.0, 6.5, 7.0, 7.5, and 8.0, respectively. The release behaviors of curcumin at pH 6.0, 6.5, and 7.0 showed obvious differences, indicating CMS-PMAA-β-CD had a narrow pH-sensitive range. The release rate of curcumin was determined by the swelling behavior of CMS-PMAA-β-CD. The larger degree of swelling caused the looser structure of CMS-PMAA-β-CD, which promoted the release of curcumin. The release rates at pH 7.5 and 8.0 were higher than those at pH 6.0 and 6.5, even though the swell ratios of CMS-PMAA-β-CD at corresponding pH were similar, probably caused by the decomposition of curcumin in an alkaline condition(Wang et al. \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e1997\u003c/span\u003e). Compared to CMS-PMAA-β-CD-Cur, the release rate of curcumin in β-CD-Cur decreased, and the release amount of curcumin increased. However, there was no pH-sensitivity presented in β-CD-Cur.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec32\" class=\"Section2\"\u003e \u003ch2\u003e3.4 The properties of CMS-PMAA-β-CD-Cur\u003c/h2\u003e \u003cp\u003eThe curcumin is encapsulated by the carrier to enhance stability. With the increase in temperature from 50 ℃ to 110 ℃, the retention of curcumin decreased. The retention of curcumin in CMS-PMAA-β-CD was higher than that of free curcumin at the same temperature. Especially the retention ratio of curcumin in CMS-PMAA-β-CD was 93.86%, while the retention ratio of free curcumin was 74.59% under the treatment at 110 ℃ for 20 min (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003eA). The results indicated that curcumin encapsulated by CMS-PMAA-β-CD significantly improved the thermal stability of curcumin. The light sensitivity of curcumin is related to its diketone structure, which is prone to degrade into colorless vanillin and ferulic acid under UV light(Liang et al. \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). The percentage of undegraded free curcumin following exposure to UV light (96 h) was 81.43%, while the undegraded curcumin in CMS-PMAA-β-CD was 94.77%, revealing that the curcumin encapsulated by CMS-PMAA-β-CD significantly reduced its photodegradation (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003eB). The cavity structure in CMS-PMAA-β-CD provided a physical barrier, which prevented the contact of curcumin with UV light.\u003c/p\u003e \u003cp\u003eThe antioxidant activity of curcumin is attributed to an enol group and two phenolic hydroxyl groups(O\u0026rsquo;Toole et al. \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). The protons in the phenolic hydroxyl of curcumin can combine with DPPH and ABTS free radicals in ethanol. With the increase in the mass ratio of curcumin: CMS-PMAA-β-CD from 1:40 to 1:5, the DPPH (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003eC) and ABTS (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003eD) radical scavenging ability increased first and then decreased, which was consistent with the tendency of loading ability. When the mass ratio of curcumin: CMS-PMAA-β-CD was 1:10, the highest DPPH and ABTS radical scavenging ability of curcumin were 81.54% and 85.56% respectively. While the DPPH and ABTS radical scavenging ability of free curcumin was 21.68% and 9.36% respectively, which were significantly lower than those of CMS-PMAA-β-CD-Cur. Hence, the CMS-PMAA-β-CD improved the solubility and enhanced the dispersibility of curcumin, promoting the exposure of the antioxidant groups of curcumin to the solution, and leading to the enhanced free radical capture(Meng et al. \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2021a\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eCurcumin has broad-spectrum antibacterial properties, owing to its structural characteristics and the generation of antioxidation products(Zheng et al. \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Fish spoilage bacteria \u003cem\u003eShewanella putrefaciens\u003c/em\u003e was selected to assess the antibacterial activity of CMS-PMAA-β-CD-Cur (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003eA). With the increase in the concentration of CMS-PMAA-β-CD-Cur, the bacteriostatic effect enhanced first and then became stable. The minimum inhibitory concentration (MIC) was recorded as the lowest concentration which showed complete inhibition of visible growth of the bacterial pathogens. Hence, the MIC of CMS-PMAA-β-CD-Cur for \u003cem\u003eShewanella putrefaciens\u003c/em\u003e was 0.625 mg/mL. When the concentration of CMS-PMAA-β-CD-Cur reached 10 mg/mL, the inhibition effect on \u003cem\u003eShewanella putrefaciens\u003c/em\u003e showed no obvious enhancement with the further increase of the concentration of CMS-PMAA-β-CD-Cur. The biosafety of preservatives is an essential index for their application in the food areas. The cytotoxicity of CMS-PMAA-β-CD-Cur and curcumin was assessed and the results are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003eB. The cell viability of L929 incubated with CMS-PMAA-β-CD-Cur and curcumin with the concentration of 10 mg/mL were more than 100%, indicating the good biocompatibility. So CMS-PMAA-β-CD-Cur suspension with the concentration of 10 mg/mL was used for yellow catfish \u003cem\u003ePelteobagrus fulvidraco\u003c/em\u003e preservation.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec33\" class=\"Section2\"\u003e \u003ch2\u003e3.5 The effect of CMS-PMAA-β-CD-Cur on the preservation\u003c/h2\u003e \u003cp\u003eThe preservation effect of CMS-PMAA-β-CD-Cur was investigated by the comparison with the blank control group without any treatment and the CMS-PMAA-β-CD group treated with CMS-PMAA-β-CD, which was determined by the indexes of pH (Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003eA), TVB-N (Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003eB), TVC (Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003eC), and drip loss (Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003eD). The CMS-PMAA-β-CD-Cur was yellow powder, which was lighter colored than curcumin (Fig. \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e). The appearance of yellow catfish did not show any difference after treated with yellow CMS-PMAA-β-CD-Cur because of the original yellow color of yellow catfish (Fig. S2). Figure\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003eA shows pH values decreased first and then increased during the storage period, which was consistent with other research(Ju et al. \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). The decrease in pH was probably due to the lactic acid induced by the glycolysis of glycogen and the phosphoric acid decomposed by ATP. With the extension of storage time, the increase in pH was caused by the volatile compounds such as ammonia, two methylamine, and trimethylamine generated by the protein decomposition. The pH of fish ranged from 6 to 7 was consistent with the pH-sensitive range of CMS-PMAA-β-CD-Cur. With the increase in the pH of fish, the release amount of curcumin in CMS-PMAA-β-CD-Cur increased. The pH values of the CMS-PMAA-β-CD-Cur group were lower than those of other groups. The treatment with CMS-PMAA-β-CD-Cur extended the pH increase of fish for 4 days. Total volatile basic nitrogen (TVB-N) is an important index to determine the spoilage degree of fish, which is composed of nitrogen compounds produced by the interaction of microorganisms and endogenous enzymes. The TVB-N content of yellow catfish was continuously increased during the storage period (Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003eB). The initial TVB-N value of fresh yellow catfish was 6.18 mg/100 g. The TVB-N value increased slowly within 2 days and increased significantly after 2 days, which was consistent with the tendency of pH changes. The TVB-N values of the control group and CMS-PMAA-β-CD group reached the limit content (20 mg/100 g) of freshwater fish set by Chinese National Standards (GB2733-2015) at day 6, while that of CMS-PMAA-β-CD-Cur group was still lower than 20 mg/100 g at day 8. Figure\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003eD displays the TVC content of each group. The edible upper limit of TVC in aquatic products is considered as 6 lg CFU/g(Al-Dagal and Bazaraa \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e1999\u003c/span\u003e). The initial TVC of fresh yellow catfish was 3.49 lg CFU/g. The increase tendency of TVC was similar to that of TVB-N. The TVC of the CMS-PMAA-β-CD-Cur group was significantly lower than that of other groups at day 8. The results of pH, TVB-N, and TVC indicated the treatment with CMS-PMAA-β-CD-Cur with the concentration of 10 mg/mL extended 2\u0026ndash;4 days of shelf-life depending on the inhibition effect on spoilage microorganisms by curcumin but not CMS-PMAA-β-CD. The drip loss is an essential index to evaluate the quality of aquatic products. The freshness of fish affects its drip loss. The drip loss showed a continuous increase during the storage period (Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003eD). The drip loss of the CMS-PMAA-β-CD-Cur group was lowest compared with that of other groups at the same condition, indicating the CMS-PMAA-β-CD-Cur could improve the storage quality of yellow catfish.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"4. Conclusion","content":"\u003cp\u003eCMS-PMAA-\u0026beta;-CD microgels as a kind of pH-sensitive carrier were successfully fabricated to deliver curcumin. It has a narrow pH-sensitive range from 6-7, which is consistent with the pH change range of fish during chilling storage. The curcumin encapsulated by CMS-PMAA-\u0026beta;-CD shows improved stability, enjoyable antioxidant activity, antibacterial activity, and biocompatibility. The treatment with CMS-PMAA-\u0026beta;-CD-Cur with the concentration of 10 mg/mL extended the shelf-life of yellow catfish for 2-4 days and improved the storage quality of fillets. This work provided a dual-functionalities strategy to construct a pH-sensitive starch-based carrier and offered a promising application in fish preservation.\u0026nbsp;\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eFunding Declaration\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was supported by the National Key R\u0026amp;D Program of China (2022YFD2100904), the China Agriculture Research System (CARS-46), the Postdoctoral Innovative Practice Position of Hubei Province, and 2020 Annual Key Project of Scientific and Technological R\u0026amp;D of Hubei Agricultural Scientific and Technological Innovation Center (2020-620-000-002-06).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor Contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eXiaojia Guo: Investigation, Methodology, Writing \u0026ndash; original draft, Writing \u0026ndash; review \u0026amp; editing, Funding acquisition. Shujin Liu: Methodology; Lanyan Yang: Methodology; Chaoguang Zhao: Methodology. Liu Shi: Investigation. Guangquan Xiong: Investigation, Funding acquisition. Lang Chen: Methodology. Sheng Chen: Methodology. Wenjin Wu: Project Administration, Resources, Supervision, Funding acquisition. Lan Wang: Conceptualization, Supervision, Project administration, Writing \u0026ndash; review \u0026amp; editing, Funding acquisition.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflicts of interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData Availability Statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors confirm that the data supporting the findings of this study are available within the article and its supplementary materials.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAcevedo-Guevara L, Nieto-Suaza L, Sanchez LT, Pinzon MI \u0026amp; Villa CC (2018) Development of native and modified banana starch nanoparticles as vehicles for curcumin. 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The FTIR, XRD, \u003csup\u003e1\u003c/sup\u003eH NMR, zeta potential, swelling ratio, and TG indicates the pH-sensitive starch-based carrier with a narrow pH-sensitive range (pH 6-7) is successfully fabricated by the carboxymethyl starch grafted with methacrylic acid first and then cross-linked with β-cyclodextrin to achieve dual-functionalities. The FTIR, XRD, and fluorescence spectroscopy reveals the mechanism of curcumin encapsulated by starch-based carrier is related to hydrophobic interactions and inter-molecular hydrogen bonding. The encapsulated curcumin shows improved stability, enjoyable antioxidant activity, antibacterial activity, and biocompatibility. The pH, TVB-N, TVC, and drip loss tests prove the application of carrier-curcumin complex with the concentration of 10 mg/mL on the preservation of yellow catfish can extend the shelf-life for 2-4 days with chilling storage and improve the storage quality of fillets. This work provides a dual-functionalities strategy to construct a pH-sensitive starch-based carrier to deliver curcumin and offers a promising choice in fish preservation.\u003c/p\u003e","manuscriptTitle":"The construction of pH-sensitive starch-based carrier to control the delivery of curcumin for preservation","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-02-01 10:34:43","doi":"10.21203/rs.3.rs-3887107/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2024-03-10T12:28:43+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-03-10T12:23:38+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-02-10T08:11:20+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"05086791-4cd8-44af-9dc9-ea794fe8a003","date":"2024-02-03T21:06:51+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"9bbc431d-b0b8-4db9-86c5-99a7a4825f37","date":"2024-01-31T02:39:00+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-01-31T01:29:06+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-01-30T11:24:44+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2024-01-30T10:23:30+00:00","index":"","fulltext":""},{"type":"submitted","content":"Food and Bioprocess Technology","date":"2024-01-22T06:29:28+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"food-and-bioprocess-technology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [Food and Bioprocess Technology](https://www.springer.com/journal/11947)","snPcode":"11947","submissionUrl":"https://submission.nature.com/new-submission/11947/3","title":"Food and Bioprocess Technology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"120f92c2-1a9e-4811-a4b6-1d207632a03c","owner":[],"postedDate":"February 1st, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2024-03-25T11:44:13+00:00","versionOfRecord":[],"versionCreatedAt":"2024-02-01 10:34:43","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-3887107","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-3887107","identity":"rs-3887107","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}