MWCNTs/Ag-enhanced Molecularly Imprinted Resorcinol Polymer Voltammetric Sensing Platform for Dopamine Determination

MWCNTs/Ag-enhanced Molecularly Imprinted Resorcinol Polymer Voltammetric Sensing Platform for Dopamine Determination | 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 MWCNTs/Ag-enhanced Molecularly Imprinted Resorcinol Polymer Voltammetric Sensing Platform for Dopamine Determination Shufang Ren, Junpeng Zhao, Xiaohang Liu, Yahui Liu, Yuan Zhang, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-3977624/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract The most prevalent catecholamine neurotransmitter of brain, dopamine (DA), is crucial to the operation of the hormone, blood vessel, and central nervous system systems. The effective determination of dopamine by means of advanced, efficient, and sensitive determination techniques has attracted much attention. This experiment designed and prepared a molecularly imprinted electroanalytical determination platform for the determination of DA. In this work, silver nanoparticles (Ag NPs) were in-situ carried on the walls of multiwalled carbon nanotube (CNTs) using sodium borohydride (NaBH4) as a reducing agent. The CNTs/Ag/GCE altered electrode was prepared using a simple drop-casting method. Molecularly imprinted polymer (MIP) membranes towards recognizing DA molecules were prepared on altered electrode surfaces using electropolymerization using resorcinol as the functional unit and dopamine (DA) as the template molecule. The cooperative effect of Ag and CNTs boosted the conductivity as well as the electrocatalytic efficiency, thereby enhancing the sensitivity to electrochemical response of the platform and reducing the determination limit. After optimizing the parameters, including the proportion of templates to functional units, electropolymerization cycles, incubation time, and pH, the platform's linear determination range for DA was 0.008 - 0.1 μM and 3 - 100 μM, with a 0.003 μM determination limit. Additionally, the platform exhibits great selectivity, anti-interference, and reproducibility. The sample recovery rate for spiked real samples, urine and serum, was good. This study provides a reference for the extraction, separation, and determination of DA. Molecularly imprinted polymer Dopamine Multi-walled carbon nanotubes Silver nanoparticles Voltammetry sensing platform Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 1. Introduction The primary catecholamine neurotransmitter of brain, dopamine (DA), is essential to the operation of cardiovascular, hormonal, and central neurological systems 1. Parkinson's disease, schizophrenia, attention deficit hyperactivity disorder, and pituitary tumors are among the disorders linked to dysregulation of the dopamine system 2-6. Due to its role as a major chemical regulating human neural network physiology and behavior, there is significant interest in advanced, efficient, and sensitive determination techniques for dopamine 7-9. Various methods for detecting DA have been developed, including spectroscopy 10, high-performance liquid chromatography 11, and mass spectrometry 12, but the above methods are complex, involving intricate sample preparation, expensive equipment, and high-cost equipment. In comparison, electrochemical sensing offers high sensitivity, compact and portable devices, and simple operation without the need for complex sample pretreatment. Sensing methods have been widely researched and applied in areas such as environmental pollutants 13, pesticide residues 14, food safety 15, biomarkers 16, and healthcare 17. The interconversion between the hydroxyl and quinone forms on the benzene ring of the DA molecule, which permits electron transfer for electrochemical measurement, is the basis for the electrochemical determination of DA 18 , 19. Additionally, electrochemical analysis facilitates in vivo and in vitro determination of DA 20. However, when using electrochemical analysis for determination, the oxidation reaction of DA on bare GCE is irreversible, requiring high potential and being prone to contamination, resulting in poor reproducibility and low sensitivity. Furthermore, substances commonly coexisting with DA, such as uric acid (UA) and ascorbic acid (AA), incline to disturb the determination of DA because of the similar oxidation potentials. Therefore, high sensitivity and specific selectivity are two key limiting factors for electrochemical determination of DA, making it a recent research hotspot 21. Immunology was the first discipline to use molecular imprinting technology (MIT) in the 1980s 22 , 23. MIT was motivated by the unique way that biological antigens and antibodies recognize each other, and involves the preparation of artificial synthetic receptors for target molecules, known as molecularly imprinted polymers (MIPs) 23 , 24. Compared to naturally occurring biological recognition systems like monoclonal antibodies or receptors, MIPs are distinguished by their distinct physical, chemical, and physical characteristics, outstanding stability, ease of synthesis, and particular selectivity 23 , 24. As a result, they have been widely applied in targeted drug delivery, molecular catalysis, chemical and biological sensing and analysis (electrochemistry, fluorescence, surface plasmon resonance, column chromatography, etc.), sample pre-treatment/chromatographic separation (solid-phase extraction, column chromatography, etc.), and others 25-34. Analytical and electroanalytical chemistry have advanced significantly as a result of the application of MIT in the realm of electrochemical sensing. Presently, cross-linking agents, initiators, light, or heat are used as inducers in the free radical polymerization of acrylic acid or ethylene-based chemical compounds as functional units to create the majority of MIPs. Functional units having electrochemical activity, on the other hand, can be used to build conductive MIP systems 35-39. These MIPs combine electrochemical activity with molecular selectivity, and have found wide applications in highly sensitive and selectively electrochemical platforms. The other side of the MIT, MIPs prepared from electroactive functional units are organic polymers with a certain degree of electrochemical inertness. Their conductivity and electrocatalytic activity are relatively poor, which reduces the sensitivity of electrochemical sensing for target analytes relying on electronic signal transmission. Therefore, the main goals of research in the domain of molecularly imprinted electrochemical sensing are to improve platform sensitivity and selectivity, increase the conductivity of MIPs, speed up electron transfer rates, and design and develop new preparation methods and strategies for MIPs appropriate for electrochemical sensing. Because electrochemical reactions frequently take place at interfaces, high conductivity carrier materials are crucial for altering the electrode surface in electrochemical sensing. The key to solving the problem is to change electrodes by functionalizing materials with high electrocatalytic activity, large specific surface area, and high conductivity 32 , 36 , 40. The modification of carrier materials on electrodes has the advantages of accelerating electron transfer, increasing active surface area, enhancing electrocatalytic activity, and improving adsorption and enrichment of target analytes. For example, Ming et al. 41 altered the electrode using reduced graphene oxide and gold nanoparticles to create a highly selective and sensitive electrochemical platform for DA detection. Las et al. 42 used electropolymerization to create a molecularly imprinted membrane that could voltammetrically detect DA in biological matrix. The membrane demonstrated exceptional selectivity in this process. Zhang et al. 43 used polypyrrole as the unit and glassy carbon electrode (GCE) altered with platinum to create a DA molecularly imprinted platform. Liu et al. 44 used molecular imprinting to alter a carbon aerogel electrode in order to create a DA electrochemical platform. AuNPs were utilized by Sha et al. 45 to alter a GCE, creating an electrochemical platform for the simultaneous measurement of uric acid and dopamine. Zhou 46 and associates created a molecularly imprinted platform with DA as the template molecule by modifying the electrodes using polymerized pyrrole and multi-walled carbon nanotubes (CNTs). Excellent DA selectivity and determination limit were demonstrated by the platform. In light of the study above, a molecularly imprinted electrochemical platform was designed and prepared in this experiment (Scheme 1), with resorcinol as the functional unit, dopamine (DA) as the template. A MIP membrane towards selective determination of DA was carried on CNTs/Ag composite, who was chosen as the signal enhancing carrier material. To manufacture the CNTs/Ag composite material, silver nanoparticles (Ag NPs) reduced with sodium borohydride (NaBH 4 ) were carried in situ on the walls of CNTs. The CNTs/Ag/GCE altered electrode was created utilizing a simple drop-coating technique. Electropolymerization was used to create a MIP membrane capable of identifying DA molecules on the altered electrodes. Ag and CNTs worked in concert to increase conductivity and electrocatalytic efficiency, which strengthened the molecularly imprinted platform's response sensitivity and decreased the determination limit. Electrochemical tests demonstrated that the MIP/CNTs/Ag/GCE platform has significant electrocatalytic activity towards DA, coupled with good selectivity, consistent performance, and anti-interference characteristic traits. 2. Experiments 2.1 Experimental Regents and Equipment NaBH 4 was purchased from Tianjin Kaitong Chemical Reagent Co., Ltd., sodium citrate was purchased from Shanghai Jianxin Chemical Co., Ltd., resorcinol was purchased from Shanghai Zhongtai Chemical Reagent Co., Ltd., silver nitrate (AgNO 3 ) was purchased from Beijing Chemical Reagent Factory. MWCNTs (industrial grade) were purchased from Pioneer Nanotechnology Co., Ltd., acetaminophenol and Nafion was purchased from Alpha Aesar (China) Chemical Co., Ltd., glucose, uric acid, disodium hydrogen phosphate (Na 2 HPO 4 ·12H 2 O) and sodium dihydrogen phosphate (NaH 2 PO 4 ) were purchased from China Pharmaceutical Chemical Reagent Co., Ltd., sodium hydroxide (NaOH) was purchased from Shanghai Wokai Biotechnology Co., Ltd., and potassium ferrocyanide was purchased from Shanghai McLin Biochemical Technology Co., Ltd. 2.2 Preparation of CNTs/Ag Ag NPs were decorated on the surface of CNTs using NaBH 4 as a reducing agent. The particular procedure was filling a round-bottom flask with 60 mL of deionized water and 60 milligrams of CNTs. 100 mM of AgNO 3 (2.4 mL) and 100 mM of sodium citrate (2.4 mL) solution were added to the flask under ultrasonic conditions. Using a magnetic stirrer, the resultant solution was rapidly agitated forcefully in an ice bath while 4.6 mL of aqueous NaBH 4 solution was gradually added. After five hours in the ice bath, the combination was allowed to mature for nineteen hours at room temperature. The final step was filtering the resultant product, repeatedly washing it with deionized water and ethanol, then drying it for an entire night at 80°C in a vacuum oven. 2.3 Preparation of MIP/CNTs/Ag/GCE In this experiment, MIP/CNTs/Ag/GCE was prepared using electropolymerization. Prior to altering the working electrode GCE (Φ 3 mm) with CNTs/Ag and MIP, the electrodes were repeatedly rinsed with deionized water after being polished with alumina powder with particle sizes of 1, 0.3, and 0.05 μm on a chamois. The electrode was cleaned with a 1:1 ethanol to water mixture and allowed to air dry after every cleaning. A suspension was created by dispersing 1 mg of CNTs/Ag in 990 μL of DMF and 10 μL of Nafion solution, followed by 30 minutes of sonication. Next, 2.5 μL of the suspension was dried by drop-casting onto a 3 mm GCE. PBS (phosphate buffer solution) with 0.01 M DA and 0.03 M resorcinol was made. The pre-elution MIP/CNTs/Ag/GCE was obtained by CV scanning 15 times at a scan rate of 100 mV s –1 . The voltage range covered by the scanning was –0.6 V to 1.5 V. After that, it was subjected to CV elution in a 0.1 M NaOH solution for 20 cycles at a scan rate of 50 mV s –1 and a voltage range of –0.6 V to 1.2 V. This produced the post-elution MIP/CNTs/Ag/GCE. With the exception of the lack of DA, the non-imprinted (NIP) electrode preparation procedure is the same as the one described before. 2.4 Electrochemical Testing and Physicochemical Characterization of Samples A standard three-electrode setup on an electrochemical workstation (CHI660E) was used for all electrochemical measurements. Ag/AgCl was the reference electrode in the three-electrode system, a platinum sheet (1 cm 2 in surface area) was the counter electrode, and the modified electrode was the working electrode. To make a 0.1 M PBS solution, NaH 2 PO 4 and Na 2 HPO 4 ·12H 2 O were dissolved in ultrapure water. To get rid of O 2 interference, the 0.1 M PBS solution was purged with N 2 for 30 minutes prior to each electrochemical test. Cyclic voltammetry (CV) measurements were performed at a scan rate of 50 mV s –1 in a 5 mM potassium ferricyanide solution containing 0.1 M KCl. In the previously indicated solution, Electrochemical impedance spectroscopy (EIS) measurements were carried out in the frequency range of 10 kHz to 0.1 Hz, and the resistance was ascertained using the resulting Nyquist plot. A 0.1 M PBS containing DA was used for the differential pulse voltammetry (DPV) measurements, which were performed in the voltage range of –0.2 to 0.6 V. Using a powder X-ray diffractometer (XRD, X'Pert PRO, Netherlands) and copper target Kα radiation (λ = 0.15416), the crystal structure of the products was ascertained. Field emission scanning electron microscopy (FESEM, Carl Zeiss Ultra Plus, Germany) and transmission electron microscopy (FETEM, FEI TECNAI G2 TF20, USA)) were used to examine the morphology of the materials. Fourier transform infrared spectroscopy (FT-IR, Digilab FTS-3000, USA) was used to examine the functional groups of the samples. 3. Results and Discussion 3.1 Characterization of Materials Figure 1 FESEM images of CNTs (A), CNTs/Ag (B), FETEM (C) and high-resolution FETEM (D) images of CNTs/Ag, FESEM of MIP/CNTs/Ag/GCE before elution (E), after elution (F), and NIP/CNTs/Ag/GCE before elution (G), after elution (H). FESEM was utilized to examine the shape and microstructure of the prepared material by characterizing different materials. As shown in Figure 1, the tube structure of the CNTs can be seen from Figure 1A. The surface became noticeably rough when Ag and CNTs were compounded using the in situ reduction method, and the granular Ag nanoparticles were uniformly attached to the CNTs, forming a structure with a large surface area (Figure 1B and Figure 1C). This will greatly increase the electrode surface's printing area and the number of platform's effective printing points, thereby raising the platforms' sensitivity. Figure 1D depicts a high-resolution CNTs/Ag composite material TEM graph, revealing the crystal spacing of Ag particles. After measurement, the crystal strip gap is around 2.3 Å, indicating that it is the (111) crystal surface of face cubic Ag. Before elution, the surface of the CNTs/Ag connected to the MIP membrane has a particle-shaped MIP coating that obscures portions of the CNTs' boundaries (Figure 1E). Figure 1F shows the MIP/CNTs/Ag/GCE post-elution image, where the MIP particle size is smaller and the CNT boundaries are more visible. Figures 1G and H depict unsealed NIP/CNTs/Ag/GCE image. The non-printed NIP differs little from the printed MIP. Figure 2 XRD (A) and FT-IR (B) of CNTs and CNTs/Ag. The diffraction peaks for CNTs emerge at 26.1° and 42.85° in the XRD spectrum of CNTs/Ag, as illustrated in Figure 2A. These positions correspond to the crystal surfaces of CNTs (002) and (100). The signature diffraction peak of CNTs (002) at 26.1° can be identified in the spectrum of CNTs/Ag. The crystals of silver metal (111), (200), (220), and (311) of the central cubic structure are represented by the diffraction peaks in the XRD spectrum of CNTs/Ag, which are located at 38.1°, 44.3°, 64.39°, and 77.31°, respectively. This is supported by the successful loading of Ag particles onto the CNT, as reported by the JCPDS number 04-0783. We used FT-IR to test the synthetic nanocomposites, as seen in Figure 2B. The stretch vibration of O–H is responsible for the absorption peak at 3405 cm –1 , while the C=O stretch is responsible for the absorptive peak at 1723 cm –1 . These results suggest that there are a few carbonyl groups (–C=O) on the surface of the carbon nanotubes (CNTs). The double-cluster vibration peaks of the CNTs' carbon skeleton are located at 1600 cm –1 and 1636 cm –1 , respectively, and the stretching vibrations of the cluster C–OH attached to the surface are at 1045 cm –1 . The active oxidizing groups of –C=O and C–OH on the CNTs is helpful for the adsorption and polymerization of MIP menbrine. The CNTs/Ag composite has an absorption spectra that is comparable to CNTs, which means the loading Ag had no substantial effect on the groups of CNTs. 3.2 Electrochemical characteristics of the altered electrode Figure 3 CV curves (A), peak current vs. electrodes of CV tests (B), potential differences of CV tests for different electrodes (C), EIS curves (D) and the corresponding resistance (E) of different electrodes for probe [Fe(CN) 6 ] 3−/4− , and DPV curves of electrodes in PBS (pH = 7) containing 0.1 μM DA (F). To investigate the electrochemical properties, CV studies were performed on bare GCE, CNTs/Ag/GCE, MIP/CNTs/Ag/GCE prior to and subsequent to elution, and NIP/CNTs/Ag/GCE electrodes subsequent to elution in a 5 mM [Fe(CN) 6 ] 3−/4− solution with 0.1 M KCl. In Figure 3A and B, redox peaks established for all electrodes, but the heights of the peaks varied with regard to the material used. Compared to the bare GCE, CNTs/Ag/GCE's peak current responsiveness was significantly higher (44 and -60 μA compared to 33 and -41 μA of GCE). Concurrently, the CNTs/Ag/GCE redox potential difference (ΔE p , 0.115 V) was less than the bare GCE (0.182 V) (Figure 3C). This is explained by high electrical conductivity and large surface area of the composite, which also quicken the electrode response kinetics. The currents of MIP/CNTs/Ag/GCE and NIP/CNTs/Ag/GCE prior to elution were smaller than those of bare GCE (oxidation currents are 19 and 15 μA, and reduction currents were –20 and –18 μA for MIP/CNTs/Ag/GCE and NIP/CNTs/Ag/GCE, respectively). The peak potential difference of redox was large (ΔE p was 0.284 and 0.247 V, respectively). In fact, the pre-elution MIP membrane is a relatively dense polymer membrane. Although it is a conductive polymer, its intrinsic properties of the polymer limit its high conductivity, which makes the redox current of the probe low and the electrode reaction kinetics slow. Following elution, templates were eliminated from MIP membranes, creating mimicked cavities that create electron transfer channels. This leads to markedly increased peak current responses, enhanced electrode dynamics, and significantly enhanced peak current signals (reoxidation currents of –52 and –41 μA, respectively) (Figure 3B). The potential difference ΔE p becomes smaller (0.127 V). However, as mentioned above, MIP is a polymer, and after being combined with CNTs/Ag, the electrical conductivity will be reduced to a certain extent. As a result, upon elution, MIP/CNTs/Ag/GCE has a smaller current than CNTs/Ag/GCE, and its potential difference is marginally greater. The experiment tested each electrode using EIS in order to examine the altered electrodes' electron transfer behavior. The resistance of CNTs/Ag/GCE (200 Ω) and MIP/CNTs/Ag/GCE (543 Ω) following elution is considerably lower than that of the bare GCE (1207 Ω), as shown in Figures 3D and E. This is explained by the composite material's good conductivity and the creation of "empty cavities" that reduce the impediment in the electronic transmission process. The resistance of MIP/CNTs/Ag/GCE (1615 Ω) and NIP/CNTs/Ag/GCE (1133 Ω) prior to elution is very high, due to the dense polymer membrane that inhibits electron transmission. Next, we examined the responsiveness of different electrodes to the DA determination. As shown in Figure 3F, response current of DA is spread from large to small in sequence to CNTs/Ag/GCE, MIP/CNTs/Ag/GCE after elution, bare GCE, before elution MIP/CNTs/Ag/GCE and NIP/CNTs/Ag/GCE. This is consistent with the electrical signals of the detected probe. The CNTs/Ag compound material enhances the current signal, and MIP treats the material with better recognition responsiveness. Figure 4 CV curves of bare GCE (A) CNTs/Ag/GCE (B) in 5 mM [Fe(CN) 6 ] 3-/4- containing 0.1 M KCl at different scan speeds, the corresponding plots of peak current vs. square root of scan rate (υ 1/2 ) (C) and (D). In a 0.1 M KCl solution containing 5 mM [Fe(CN) 6 ] 3–/4– , the area of electrochemical activity of the bare GCE (Figure 4A) and CNTs/Ag/GCE (Figure 4B) were assessed using CV at varying scanning speeds. The oxidation peak and reduction peak currents grow with scanning speed, indicating that diffusion controls the process. The peak potential shifts simultaneously, with the reduction peak shifting negatively and the oxide peak shifting positively. The peak currents at the anode and cathode are proportional to the square root (υ 1/2 ) of the scanning rate, as seen in Figures 4C and D. In this experiment, the active surface area of altered electrodes was calculated using the Randles-Sevcik equations: The variables in this equation are: A is the area of electrochemical activity; D is a proliferation coefficient (6.7×10 –6 cm 2 s –1 ); C is [Fe(CN) 6 ] 3–/4– , concentration C = 5.0 mM; and n is the number of electrons involved in the reaction in [Fe(CN) 6 ] 3–/4– solution (n = 1). According to the inclination of i p - υ 1/2 , the active surface area of the bare electrode and CNTs/Ag/GCE is 0.037 cm 2 and 0.055 cm 2 , respectively. This suggests that the material can increase the active area of electrodes. 3.3 Optimization of experiments Figure 5 Line chart of the proportion of functional unit to template (A), optimized line graph of polymerization cycles (B), accumulation time (C), DPV curves under variable pHs (D), peak currents vs. pH (E), and fitting line of oxidation potential vs. pH (F). Optimization of the proportion of functional units and templates Figure 5A shows the DPV peak current of altered electrodes with various proportion of functional units to template of 1:1, 3:1, 5:1, 7:1, and 9:1, respectively. It is clear that when the ratio is 3:1, the platform responds to the DA with the largest peak reaction. Conversely, when the proportion is 1:1, the amount of templates is relatively less, making it impossible to effectively polymerize to form a uniform continuous membrane, which results in a reduced effective identifying point and a decreased current. As a result, the peak electric current response decreases as the single unit proportion increases, a decrease may be attributed to the reduced template molecule, which decreases the number of printed empty cavities. However, because the functional unit is overweight and the templates are insufficient, the MIP membrane that forms is overly dense, which lowers conductivity and, as a result, lowers current. Optimization of the number of polymerization cycles Figure 5B illustrates our analysis of the DPV peak current response at 10, 12, 14, 16, and 18 of polymerization cycles. The platform's maximal response to the DA reaches its maximum at 14 cycles, and the peak reaction declines as the number of polymerization cycles rises. This is because a higher polymerization cycle results in a thicker MIP membrane, which makes elution more difficult and prevents electronic transmission. At 10 and 12 cycles, on the other hand, a thinner MIP membrane due to an insufficient number of polymerization cycles causes the membrane's effective printing points to be too few, potentially damaging the membrane's structure during the elution and removal process. Optimization of incubation time We examined the DPV peak current response for the altered electrodes incubated in the PBS containing 0.01 mM DA for 30, 60, 90, 120, and 150 s, respectively, as Figure 5C illustrates. Peak current increases over the course of the incubation period, peaking at 120 s. The peak current then starts to decrease and eventually stays the same, indicating that after incubation on the electrode surface for 120 s, DA has reached absorption balance. Thus, 120 s is the ideal incubation period for this experiment. pH optimization Because the pH of PBS will influence the detection of DA, we conducted DPV tests on the platform to determine DA in various pH solutions. As seen in Figure 5D, the proton's function in the electrochemical reaction process is responsible for the peak current response reaching its maximum at pH7. Electrochemical reactions become more challenging when the pH rises or falls due to an excess or shortage of protons. Figure 5F displays a linear overview of DA's peak voltage and peak current. This observation implies that the proton played a role in the DA's electrochemical reaction. The equation for E pa linear regression with pH is E pa (V) = 0.4809 - 0.0467 pH (R 2 = 0.9994). The absolute value of its inclination (0.0467 V pH –1 ) is almost exactly identical to the theoretical value (0.059 V pH –1 ), indicating that the quantity of protons and electrons involved in the redox reaction is equal. 3.4 Linear range Figure 6 DPV of DA with concentrations of 0.008, 0.03, 0.05, 0.07, 0.09, 0.1, 3, 5, 10, 40, 60, and 100 μM (A), and calibration plot of DA (0.008 - 0.1 μM) (B) (3 - 100 μM) (C). To evaluate the sensitivity of the MIP platform, the peak current intensity of the platform towards DA at different concentrations was examined under optimal conditions using DPV tests. The oxide peak current increases as the concentration of DA increases, as seen in Figure 6A. The oxide peak currents and DA concentrations between 0.008 - 0.1 μM and 3 - 100 μM have linear relationship. Ip (μA) = 0.17733C (μM) + 9.51903 (R 2 = 0.9945) is the linear combination of the DA concentration with the response peak current at 3 - 100 μM. Ip (μA) = 43.49299C (μM) + 3.89407 (R 2 = 0.9949) is the linear equation of the DA concentration with the response peak current at 0.008 - 0.1 μM. The platform acquired a 0.003 μM (S/N = 3) determination limit. From Table 1, the MIP/CNTs/Ag/GCE performs on par with or better than other modified electrodes. There are two possible reasons for the improvement in the determination performance: (1) CNTs/Ag, prepared with the local restoration method as a printing support material, the excellent electrocatalysis properties of metal nanoparticles themselves and the good thermal stability after compounding with carbon materials make the platform have extremely high conductivity and stability; (2) the structure of the MIP/CNTs/Ag composition that forms a large surface area is conducive to the formation of more printing spots, so that more DA molecules can be absorbed during the electrolysis process. Table 1 Comparison of the DA with other published work Altered materials Electrode Methods Linear range/μM LOD/μM References AuNPs/rGO GCE DPV 0.05-10 0.017 41 Pt GCE DPV 0.01-0.1 0.0033 43 AuNPs/CNTs GCE DPV 0.0005-1 0.00016 47 Biomass carbon/MOF-derived Co 3 O 4 /FeCo 2 O 4 GCE DPV 0.1 - 250 0.1 - 250 48 MoS 2 /poly(3,4-ethylenedioxythiophene) GCE DPV 0.1 - 250 0.52 49 α-MnO 2 /Rutile TiO 2 composite GCE DPV 0.012 - 3.64 & 4.84 - 90 3.5 50 Hierarchical manganese dioxide nanoflower/multiwalled carbon nanotube Electrochemically pretreated GCE DPV 0.5 - 30.0 0.17 51 Sulfur vacancy (Sv) rich MoS 2 -CNTs with coaxial hierarchical structure and highly dispersed active gold particles (Au-Sv-MoS 2 -CNTs) GCE DPV 0.002 - 100 0.002 52 Hierarchical nanoporous (HNP) PtTi alloy GCE DPV 4 - 500 / 53 Au nanoplates and reduced graphene oxide (RGO) GCE DPV 6.8 - 41 1.4 54 Reduced graphene oxide-zinc oxide (RGO–ZnO) composite GCE DPV 3 - 330 1.08 55 Electrochemically reduced graphene oxide GCE 0.5 - 60 250 56 Copper terephthalate metal–organic framework, GO = graphene oxide GCE 1 - 50 0.21 57 Polypyrrole MIP/gold-nanowires GCE 0.4 - 10 58 Functional thia-bilane structure (product of addition reaction of tripyrrane 1 to nitrovinyl thiophene 2 in the presence of molecular iodine) MIP film Pencil graphite electrode DPV 0.05 - 250 0.020 59 Graphene/MIP Gold electrode DPV 0.1 - 10 0.033 60 MIP of poly-bromophenol blue GCE DPV 0 - 1.2 0.000162 61 MIP/CNTs/Ag GCE DPV 0.008-0.1 & 3 - 100 0.003 This work 3.5 Selectiveness, resistance to interference and reproducibility Selectiveness, interference resistance, and repeatability were investigated in order to evaluate the viability of the platform. A key performance indicator for the molecular imprint platform is selectivity. The DPV peak current response to acetaminophenol, glucose, and uric acid is displayed in Figure 7A. The MIP electrode and the NIP electrodes can both determine a concentration of 0.01 mM dopamine. It is evident that, when the test material is for acetaminophenol, glucose, and uric acid, the difference in peak response determined by NIP and NIP electrolyte is very small, and when the testing object is DA, the difference of the two current responses is clearly visible. MIP current is far higher than NIP, and the printing factor is 5.56 (IF = I MIP /I PIN ), indicating that the platform has good selectiveness. We employed DPV technology, as demonstrated in Figure 7B, to confirm the prepared platform's reproducibility. The measurement yielded a relative standard deviation (RSD) of 4.2% when five electrodes were used in parallel. These results indicate that the MIP platform exhibits good repeatability. The inorganic salt ions of Na + , K + , Cl - , and NO 3 2- with 50 times concentration of DA, almost has no effect on the detection current (Figure 7C), meaning the platform has desired freedom from jamming of inorganic salt ions. Figure 7 Histogram of DPV response of MIP and NIP platforms to DA (0.01 mM) and structural analogs or coexisted substances (acetaminophen (AP), glucose (GL), uric acid (UA), 0.01 mM) (A), DPV peak current diagram of parallel 5 MIP/CNTs/Ag/GCE electrodes (B), and currents in the presence of inorganic salt ions (Na + , K + , Cl - , NO 3 - ) with a concentration of 50 times the DA concentration (C). Table 2 Test results of real samples with marking method Samples Added (μM) Found (μM) Recovery (%) RSD (%) n = 5 Urine 1 1.11 111.0 7.31 5 5.34 106.8 5.16 10 10.72 107.4 3.27 Serum 1 0.92 92.0 6.53 5 4.37 87.4 4.84 10 9.61 96.1 2.95 3.6 Spiked Real Sample Tests In this investigation, we used the spiked approach to compute and assess the recovery rate of DA in urine and serum. The sealed normal human serum was bought from KOIZEE Scientific Lab's, and the urine was obtained from the healthy participants in our lab. 100 mL PBS (pH = 7) was used to dissolve 1.53 mg of DA, creating a mother solution with a 0.1 mM DA solubility. The 9.5 mL PBS solution was diluted with mother liquor, and 0.5 mL urine and serum were added. The mixture was well-shook, and PBS solutions with DA concentrations of 1, 5, and 10 μM were created. The DPV tests were run after the mixture was uniform. The test results in Table 2 demonstrate that, despite DA molecular imprinting being done to improve the ability of the altered electrode to recognize and adsorb DA, the recovery rate in urine is normally high and is impacted by the presence of uric acid in the urine. However, because there are some non-specific adsorption sites in MIP membranes and because DA and uric acid have similar oxidation potentials, DA recovery rates in urine are typically higher than 100%. Five parallel tests yield a relative standard deviation of 3.27%-7.31%. The recovery rates in serum are all lower than 100%, ranging from 87.4%-96.1%, and the relative standard deviation of five determinations is 2.95%-6.53%. 4. Conclusions This study used the in-situ reduction method to prepare CNTs/Ag composites and drop coating and electropolymerization to construct MIP/CNTs/Ag/GCE. The template molecule used in this process was DA, the composite functional unit was resorcinol, and the conductive catalytic material was the CNTs/Ag composite. On GCE, a molecularly imprinted electrochemical platform with a DA-specific recognition function was created. The enhanced electrochemical catalytic reaction rate is facilitated by the good synergistic catalytic effect of Ag composites with CNTs. The findings of the electrochemical test demonstrate that the enhanced electrode's electrical conductivity was derived from the high electrical conductivity CNTs/Ag composites. The platform shows good DA selectivity and sensitivity because to the enhanced specific surface area and synergistic catalysis of the conductive carrier material. After optimizing the ratio of the functional unit to template molecule, the number of electropolymerization cycles, the pH, and the incubation duration, the linear DA determination range and linear determination limit of the platform are 0.008 - 0.1 μM and 3 - 100 μM, respectively. Furthermore, the platform exhibits good repeatability and anti-interference properties. The indicated spiking samples had a high sample recovery rate. A reference for the extraction, separation, and determination of DA is given by this work. Declarations Acknowledgements Financial supports from the National Natural Science Foundation of China (22164003), the Natural Science Foundation of Gansu Province (23JRRA1228), the Higher Education Innovation Fund Project of Gansu Province (2023A-097, 2021B-177), the Science and Technology Major Project of Gansu Province (21ZD4FA032), and the Key Talent Project of Gansu Province (2022RCXM085) are gratefully acknowledged. Credit author statements Shufang Ren: Validation, Writing–review & editing, Funding acquisition. Junpeng Zhao: Investigation, Material preparation, Formal analysis. Data curation, Writing–original draft. Xiaohang Liu: Writing–original draft, Writing–review & editing. Yahui Liu: Writing–review & editing. Yuan Zhang: Funding acquisition. Zhixiang Zheng: Funding acquisition, Supervision. Declaration of competing interest The authors declare no competing financial interest. Supplementary information Not Applicable Data and code availability: The data that support the findings of this study are available from the corresponding author upon reasonable request. Ethical approval: Not Applicable References Ma, X.; Gao, F.; Dai, R.; Liu, G.; Zhang, Y.; Lu, L.; Yu, Y. Novel electrochemical sensing platform based on a molecularly imprinted polymer-decorated 3D-multi-walled carbon nanotube intercalated graphene aerogel for selective and sensitive detection of dopamine. 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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-3977624","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":274249156,"identity":"509cb4eb-0058-4c10-bad6-d6977f5d44b3","order_by":0,"name":"Shufang 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Law","correspondingAuthor":false,"prefix":"","firstName":"Zhixiang","middleName":"","lastName":"Zheng","suffix":""}],"badges":[],"createdAt":"2024-02-22 05:04:05","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-3977624/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-3977624/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":51541172,"identity":"8e42e63a-8a29-461c-9bcc-442802128ac9","added_by":"auto","created_at":"2024-02-23 11:21:38","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":480412,"visible":true,"origin":"","legend":"\u003cp\u003eFESEM images of CNTs (A), CNTs/Ag (B), FETEM (C) and high-resolution FETEM (D) images of CNTs/Ag, FESEM of MIP/CNTs/Ag/GCE before elution (E), after elution (F), and NIP/CNTs/Ag/GCE before elution (G), after elution (H).\u003c/p\u003e","description":"","filename":"Picture1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3977624/v1/72874e5052a391ef8642e39a.jpg"},{"id":51541346,"identity":"7e84808b-1870-4258-b717-d66605c5ef50","added_by":"auto","created_at":"2024-02-23 11:29:38","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":180551,"visible":true,"origin":"","legend":"\u003cp\u003eXRD (A) and FT-IR (B) of CNTs and CNTs/Ag.\u003c/p\u003e","description":"","filename":"Picture2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3977624/v1/74549495b9eff78024d205b3.jpg"},{"id":51541174,"identity":"34b82207-f8df-461b-aae8-6baaf2502aec","added_by":"auto","created_at":"2024-02-23 11:21:38","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":266001,"visible":true,"origin":"","legend":"\u003cp\u003eCV curves (A), peak current vs. electrodes of CV tests (B), potential differences of CV tests for different electrodes (C), EIS curves (D) and the corresponding resistance (E) of different electrodes for probe [Fe(CN)\u003csub\u003e6\u003c/sub\u003e]\u003csup\u003e3−/4−\u003c/sup\u003e, and DPV curves of electrodes in PBS (pH = 7) containing 0.1 μM DA (F).\u003c/p\u003e","description":"","filename":"Picture3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3977624/v1/afe145715791ae1248d1ed1d.jpg"},{"id":51541345,"identity":"e74528ac-b74d-4e87-a2f4-6f9b457a5c23","added_by":"auto","created_at":"2024-02-23 11:29:38","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":272292,"visible":true,"origin":"","legend":"\u003cp\u003eCV curves of bare GCE (A) CNTs/Ag/GCE (B) in 5 mM [Fe(CN)\u003csub\u003e6\u003c/sub\u003e]\u003csup\u003e3-/4-\u003c/sup\u003e containing 0.1 M KCl at different scan speeds, the corresponding plots of peak current vs. square root of scan rate (υ\u003csup\u003e1/2\u003c/sup\u003e) (C) and (D).\u003c/p\u003e","description":"","filename":"Picture4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3977624/v1/815b2dc98e8f9881ee48551c.jpg"},{"id":51541177,"identity":"994743c1-5e68-4af3-8ab6-8b52ddf02ba8","added_by":"auto","created_at":"2024-02-23 11:21:38","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":202386,"visible":true,"origin":"","legend":"\u003cp\u003eLine chart of the proportion of functional unit to template (A), optimized line graph of polymerization cycles (B), accumulation time (C), DPV curves under variable pHs (D), peak currents vs. pH (E), and fitting line of oxidation potential vs. pH (F).\u003c/p\u003e","description":"","filename":"Picture5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3977624/v1/a086f8cda294f8f8813a015b.jpg"},{"id":51541178,"identity":"fe14b643-6f7d-475f-a762-560568563ca0","added_by":"auto","created_at":"2024-02-23 11:21:38","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":106572,"visible":true,"origin":"","legend":"\u003cp\u003eDPV of DA with concentrations of 0.008, 0.03, 0.05, 0.07, 0.09, 0.1, 3, 5, 10, 40, 60, and 100 μM (A), and calibration plot of DA (0.008 - 0.1 μM) (B) (3 - 100 μM) (C).\u003c/p\u003e","description":"","filename":"Picture6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3977624/v1/fdbbd94470c90d82867e9988.jpg"},{"id":51541176,"identity":"84e0269e-5a4e-472a-afbb-770dfffb109e","added_by":"auto","created_at":"2024-02-23 11:21:38","extension":"jpg","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":104219,"visible":true,"origin":"","legend":"\u003cp\u003eHistogram of DPV response of MIP and NIP platforms to DA (0.01 mM) and structural analogs or coexisted substances (\u003ca href=\"javascript:;\"\u003eacetaminophen\u003c/a\u003e (AP), glucose (GL), uric acid (UA), 0.01 mM) (A), DPV peak current diagram of parallel 5 MIP/CNTs/Ag/GCE electrodes (B), and currents in the presence of inorganic salt ions (Na\u003csup\u003e+\u003c/sup\u003e, K\u003csup\u003e+\u003c/sup\u003e, Cl\u003csup\u003e-\u003c/sup\u003e, NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e-\u003c/sup\u003e) with a concentration of 50 times the DA concentration (C).\u003c/p\u003e","description":"","filename":"Picture7.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3977624/v1/87ca8ca115f707dd7f78e10b.jpg"},{"id":65306956,"identity":"80127dd1-f005-43d4-89bf-d9c5bd8d5080","added_by":"auto","created_at":"2024-09-26 01:23:33","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2474659,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-3977624/v1/bbc5805a-a707-4769-a294-494ea9e1afcc.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"MWCNTs/Ag-enhanced Molecularly Imprinted Resorcinol Polymer Voltammetric Sensing Platform for Dopamine Determination","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eThe primary catecholamine neurotransmitter of brain, dopamine (DA), is essential to the operation of cardiovascular, hormonal, and central neurological systems 1. Parkinson\u0026apos;s disease, schizophrenia, attention deficit hyperactivity disorder, and pituitary tumors are among the disorders linked to dysregulation of the dopamine system 2-6. Due to its role as a major chemical regulating human neural network physiology and behavior, there is significant interest in advanced, efficient, and sensitive determination techniques for dopamine 7-9. Various methods for detecting DA have been developed, including spectroscopy 10, high-performance liquid chromatography 11, and mass spectrometry 12, but the above methods are complex, involving intricate sample preparation, expensive equipment, and high-cost equipment. In comparison, electrochemical sensing offers high sensitivity, compact and portable devices, and simple operation without the need for complex sample pretreatment. Sensing methods have been widely researched and applied in areas such as environmental pollutants 13, pesticide residues 14, food safety 15, biomarkers 16, and healthcare 17.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe interconversion between the hydroxyl and quinone forms on the benzene ring of the DA molecule, which permits electron transfer for electrochemical measurement, is the basis for the electrochemical determination of DA 18\u003csup\u003e,\u003c/sup\u003e19. Additionally, electrochemical analysis facilitates in vivo and in vitro determination of DA 20. However, when using electrochemical analysis for determination, the oxidation reaction of DA on bare GCE is irreversible, requiring high potential and being prone to contamination, resulting in poor reproducibility and low sensitivity. Furthermore, substances commonly coexisting with DA, such as uric acid (UA) and ascorbic acid (AA), incline to disturb the determination of DA because of the similar oxidation potentials. Therefore, high sensitivity and specific selectivity are two key limiting factors for electrochemical determination of DA, making it a recent research hotspot 21.\u003c/p\u003e\n\u003cp\u003eImmunology was the first discipline to use molecular imprinting technology (MIT) in the 1980s 22\u003csup\u003e,\u003c/sup\u003e23. MIT was motivated by the unique way that biological antigens and antibodies recognize each other, and involves the preparation of artificial synthetic receptors for target molecules, known as molecularly imprinted polymers (MIPs) 23\u003csup\u003e,\u003c/sup\u003e24. Compared to naturally occurring biological recognition systems like monoclonal antibodies or receptors, MIPs are distinguished by their distinct physical, chemical, and physical characteristics, outstanding stability, ease of synthesis, and particular selectivity 23\u003csup\u003e,\u003c/sup\u003e24. As a result, they have been widely applied in targeted drug delivery, molecular catalysis, chemical and biological sensing and analysis (electrochemistry, fluorescence, surface plasmon resonance, column chromatography, etc.), sample pre-treatment/chromatographic separation (solid-phase extraction, column chromatography, etc.), and others 25-34. Analytical and electroanalytical chemistry have advanced significantly as a result of the application of MIT in the realm of electrochemical sensing. Presently, cross-linking agents, initiators, light, or heat are used as inducers in the free radical polymerization of acrylic acid or ethylene-based chemical compounds as functional units to create the majority of MIPs. Functional units having electrochemical activity, on the other hand, can be used to build conductive MIP systems 35-39. These MIPs combine electrochemical activity with molecular selectivity, and have found wide applications in highly sensitive and selectively electrochemical platforms.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe other side of the MIT, MIPs prepared from electroactive functional units are organic polymers with a certain degree of electrochemical inertness. Their conductivity and electrocatalytic activity are relatively poor, which reduces the sensitivity of electrochemical sensing for target analytes relying on electronic signal transmission. Therefore, the main goals of research in the domain of molecularly imprinted electrochemical sensing are to improve platform sensitivity and selectivity, increase the conductivity of MIPs, speed up electron transfer rates, and design and develop new preparation methods and strategies for MIPs appropriate for electrochemical sensing. Because electrochemical reactions frequently take place at interfaces, high conductivity carrier materials are crucial for altering the electrode surface in electrochemical sensing. The key to solving the problem is to change electrodes by functionalizing materials with high electrocatalytic activity, large specific surface area, and high conductivity 32\u003csup\u003e,\u003c/sup\u003e36\u003csup\u003e,\u003c/sup\u003e40. The modification of carrier materials on electrodes has the advantages of accelerating electron transfer, increasing active surface area, enhancing electrocatalytic activity, and improving adsorption and enrichment of target analytes. For example, Ming et al. 41 altered the electrode using reduced graphene oxide and gold nanoparticles to create a highly selective and sensitive electrochemical platform for DA detection. Las et al. 42 used electropolymerization to create a molecularly imprinted membrane that could voltammetrically detect DA in biological matrix. The membrane demonstrated exceptional selectivity in this process. Zhang et al. 43 used polypyrrole as the unit and glassy carbon electrode (GCE) altered with platinum to create a DA molecularly imprinted platform. Liu et al. 44 used molecular imprinting to alter a carbon aerogel electrode in order to create a DA electrochemical platform. AuNPs were utilized by Sha et al. 45 to alter a GCE, creating an electrochemical platform for the simultaneous measurement of uric acid and dopamine. Zhou 46 and associates created a molecularly imprinted platform with DA as the template molecule by modifying the electrodes using polymerized pyrrole and multi-walled carbon nanotubes (CNTs). Excellent DA selectivity and determination limit were demonstrated by the platform.\u003c/p\u003e\n\u003cp\u003eIn light of the study above, a molecularly imprinted electrochemical platform was designed and prepared in this experiment (Scheme 1), with resorcinol as the functional unit, dopamine (DA) as the template. A MIP membrane towards selective determination of DA was carried on CNTs/Ag composite, who was chosen as the signal enhancing carrier material. To manufacture the CNTs/Ag composite material, silver nanoparticles (Ag NPs) reduced with sodium borohydride (NaBH\u003csub\u003e4\u003c/sub\u003e) were carried in situ on the walls of CNTs. The CNTs/Ag/GCE altered electrode was created utilizing a simple drop-coating technique. Electropolymerization was used to create a MIP membrane capable of identifying DA molecules on the altered electrodes. Ag and CNTs worked in concert to increase conductivity and electrocatalytic efficiency, which strengthened the molecularly imprinted platform\u0026apos;s response sensitivity and decreased the determination limit. Electrochemical tests demonstrated that the MIP/CNTs/Ag/GCE platform has significant electrocatalytic activity towards DA, coupled with good selectivity, consistent performance, and anti-interference characteristic traits.\u003c/p\u003e"},{"header":"2. Experiments","content":"\u003ch2\u003e2.1 Experimental Regents and Equipment\u003c/h2\u003e\n\u003cp\u003eNaBH\u003csub\u003e4\u003c/sub\u003e was purchased from Tianjin Kaitong Chemical Reagent Co., Ltd., sodium citrate was purchased from Shanghai Jianxin Chemical Co., Ltd., resorcinol was purchased from Shanghai Zhongtai Chemical Reagent Co., Ltd., silver nitrate (AgNO\u003csub\u003e3\u003c/sub\u003e) was purchased from Beijing Chemical Reagent Factory. MWCNTs (industrial grade) were purchased from Pioneer Nanotechnology Co., Ltd., acetaminophenol and Nafion was purchased from Alpha Aesar (China) Chemical Co., Ltd., glucose,\u0026nbsp;uric acid,\u0026nbsp;disodium hydrogen phosphate (Na\u003csub\u003e2\u003c/sub\u003eHPO\u003csub\u003e4\u003c/sub\u003e\u0026middot;12H\u003csub\u003e2\u003c/sub\u003eO) and sodium dihydrogen phosphate (NaH\u003csub\u003e2\u003c/sub\u003ePO\u003csub\u003e4\u003c/sub\u003e) were purchased from China Pharmaceutical Chemical Reagent Co., Ltd., sodium hydroxide (NaOH) was purchased from Shanghai Wokai Biotechnology Co., Ltd., and potassium ferrocyanide was purchased from Shanghai McLin Biochemical Technology Co., Ltd.\u003c/p\u003e\n\u003ch2\u003e2.2 Preparation of CNTs/Ag\u003c/h2\u003e\n\u003cp\u003eAg NPs were decorated on the surface of CNTs using NaBH\u003csub\u003e4\u003c/sub\u003e as a reducing agent. The particular procedure was filling a round-bottom flask with 60 mL of deionized water and 60 milligrams of CNTs. 100 mM of AgNO\u003csub\u003e3\u003c/sub\u003e (2.4 mL) and 100 mM of sodium citrate (2.4 mL) solution were added to the flask under ultrasonic conditions. Using a magnetic stirrer, the resultant solution was rapidly agitated forcefully in an ice bath while 4.6 mL of aqueous NaBH\u003csub\u003e4\u003c/sub\u003e solution was gradually added. After five hours in the ice bath, the combination was allowed to mature for nineteen hours at room temperature. The final step was filtering the resultant product, repeatedly washing it with deionized water and ethanol, then drying it for an entire night at 80\u0026deg;C in a vacuum oven.\u003c/p\u003e\n\u003ch2\u003e2.3 Preparation of MIP/CNTs/Ag/GCE\u003c/h2\u003e\n\u003cp\u003eIn this experiment, MIP/CNTs/Ag/GCE was prepared using electropolymerization. Prior to altering the working electrode GCE (\u0026Phi; 3 mm) with CNTs/Ag and MIP, the electrodes were repeatedly rinsed with deionized water after being polished with alumina powder with particle sizes of 1, 0.3, and 0.05 \u0026mu;m on a chamois. The electrode was cleaned with a 1:1 ethanol to water mixture and allowed to air dry after every cleaning. A suspension was created by dispersing 1 mg of CNTs/Ag in 990 \u0026mu;L of DMF and 10 \u0026mu;L of Nafion solution, followed by 30 minutes of sonication. Next, 2.5 \u0026mu;L of the suspension was dried by drop-casting onto a 3 mm GCE. PBS (phosphate buffer solution) with 0.01 M DA and 0.03 M resorcinol was made.\u0026nbsp;The pre-elution MIP/CNTs/Ag/GCE was obtained by CV scanning 15 times at a scan rate of 100 mV s\u003csup\u003e\u0026ndash;1\u003c/sup\u003e. The voltage range covered by the scanning was \u0026ndash;0.6 V to 1.5 V. After that, it was subjected to CV elution in a 0.1 M NaOH solution for 20 cycles at a scan rate of 50 mV s\u003csup\u003e\u0026ndash;1\u003c/sup\u003e and a voltage range of \u0026ndash;0.6 V to 1.2 V. This produced the post-elution MIP/CNTs/Ag/GCE. With the exception of the lack of DA, the non-imprinted (NIP) electrode preparation procedure is the same as the one described before.\u003c/p\u003e\n\u003ch2\u003e2.4 Electrochemical Testing and Physicochemical Characterization of Samples\u003c/h2\u003e\n\u003cp\u003eA standard three-electrode setup on an electrochemical workstation (CHI660E) was used for all electrochemical measurements. Ag/AgCl was the reference electrode in the three-electrode system, a platinum sheet (1 cm\u003csup\u003e2\u003c/sup\u003e in surface area) was the counter electrode, and the modified electrode was the working electrode. To make a 0.1 M PBS solution, NaH\u003csub\u003e2\u003c/sub\u003ePO\u003csub\u003e4\u003c/sub\u003e and Na\u003csub\u003e2\u003c/sub\u003eHPO\u003csub\u003e4\u003c/sub\u003e\u0026middot;12H\u003csub\u003e2\u003c/sub\u003eO were dissolved in ultrapure water. To get rid of O\u003csub\u003e2\u003c/sub\u003e interference, the 0.1 M PBS solution was purged with N\u003csub\u003e2\u003c/sub\u003e for 30 minutes prior to each electrochemical test. Cyclic voltammetry (CV) measurements were performed at a scan rate of 50 mV s\u003csup\u003e\u0026ndash;1\u003c/sup\u003e in a 5 mM potassium ferricyanide solution containing 0.1 M KCl. In the previously indicated solution, Electrochemical impedance spectroscopy (EIS) measurements were carried out in the frequency range of 10 kHz to 0.1 Hz, and the resistance was ascertained using the resulting Nyquist plot. A 0.1 M PBS containing DA was used for the differential pulse voltammetry (DPV) measurements, which were performed in the voltage range of \u0026ndash;0.2 to 0.6 V.\u003c/p\u003e\n\u003cp\u003eUsing a powder X-ray diffractometer (XRD, X\u0026apos;Pert PRO, Netherlands) and copper target K\u0026alpha; radiation (\u0026lambda; = 0.15416), the crystal structure of the products was ascertained. Field emission scanning electron microscopy (FESEM, Carl Zeiss Ultra Plus, Germany) and transmission electron microscopy (FETEM, FEI TECNAI G2 TF20, USA)) were used to examine the morphology of the materials. Fourier transform infrared spectroscopy (FT-IR, Digilab FTS-3000, USA) was used to examine the functional groups of the samples.\u003c/p\u003e"},{"header":"3. Results and Discussion ","content":"\u003ch2\u003e3.1 Characterization of Materials\u003c/h2\u003e\n\u003cp\u003e\u003cstrong\u003eFigure 1\u003c/strong\u003e FESEM images of CNTs (A), CNTs/Ag (B), FETEM (C) and high-resolution FETEM (D) images of CNTs/Ag, FESEM of MIP/CNTs/Ag/GCE before elution (E), after elution (F), and NIP/CNTs/Ag/GCE before elution (G), after elution (H).\u003c/p\u003e\n\u003cp\u003eFESEM was utilized to examine the shape and microstructure of the prepared material by characterizing different materials. As shown in Figure 1, the tube structure of the CNTs can be seen from Figure 1A. The surface became noticeably rough when Ag and CNTs were compounded using the in situ reduction method, and the granular Ag nanoparticles were uniformly attached to the CNTs, forming a structure with a large surface area (Figure 1B and Figure 1C). This will greatly increase the electrode surface\u0026apos;s printing area and the number of platform\u0026apos;s effective printing points, thereby raising the platforms\u0026apos; sensitivity. Figure 1D depicts a high-resolution CNTs/Ag composite material TEM graph, revealing the crystal spacing of Ag particles. After measurement, the crystal strip gap is around 2.3 \u0026Aring;, indicating that it is the (111) crystal surface of face cubic Ag. Before elution, the surface of the CNTs/Ag connected to the MIP membrane has a particle-shaped MIP coating that obscures portions of the CNTs\u0026apos; boundaries (Figure 1E). Figure 1F shows the MIP/CNTs/Ag/GCE post-elution image, where the MIP particle size is smaller and the CNT boundaries are more visible. Figures 1G and H depict unsealed NIP/CNTs/Ag/GCE image. The non-printed NIP differs little from the printed MIP.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFigure 2\u003c/strong\u003e XRD (A) and FT-IR (B) of CNTs and CNTs/Ag.\u003c/p\u003e\n\u003cp\u003eThe diffraction peaks for CNTs emerge at 26.1\u0026deg; and 42.85\u0026deg; in the XRD spectrum of CNTs/Ag, as illustrated in Figure 2A. These positions correspond to the crystal surfaces of CNTs (002) and (100). The signature diffraction peak of CNTs (002) at 26.1\u0026deg; can be identified in the spectrum of CNTs/Ag. The crystals of silver metal (111), (200), (220), and (311) of the central cubic structure are represented by the diffraction peaks in the XRD spectrum of CNTs/Ag, which are located at 38.1\u0026deg;, 44.3\u0026deg;, 64.39\u0026deg;, and 77.31\u0026deg;, respectively. This is supported by the successful loading of Ag particles onto the CNT, as reported by the JCPDS number 04-0783.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eWe used FT-IR to test the synthetic nanocomposites, as seen in Figure 2B. The stretch vibration of O\u0026ndash;H is responsible for the absorption peak at 3405 cm\u003csup\u003e\u0026ndash;1\u003c/sup\u003e, while the C=O stretch is responsible for the absorptive peak at 1723 cm\u003csup\u003e\u0026ndash;1\u003c/sup\u003e. These results suggest that there are a few carbonyl groups (\u0026ndash;C=O) on the surface of the carbon nanotubes (CNTs). The double-cluster vibration peaks of the CNTs\u0026apos; carbon skeleton are located at 1600 cm\u003csup\u003e\u0026ndash;1\u003c/sup\u003e and 1636 cm\u003csup\u003e\u0026ndash;1\u003c/sup\u003e, respectively, and the stretching vibrations of the cluster C\u0026ndash;OH attached to the surface are at 1045 cm\u003csup\u003e\u0026ndash;1\u003c/sup\u003e. The active oxidizing groups of \u0026ndash;C=O and C\u0026ndash;OH \u0026nbsp;on the CNTs is helpful for the adsorption and polymerization of MIP menbrine. The CNTs/Ag composite has an absorption spectra that is comparable to CNTs, which means the loading Ag had no substantial effect on the groups of CNTs.\u003c/p\u003e\n\u003ch1\u003e3.2 Electrochemical characteristics of the altered electrode\u003c/h1\u003e\n\u003cp\u003e\u003cstrong\u003eFigure 3\u003c/strong\u003e CV curves (A), peak current vs. electrodes of CV tests (B), potential differences of CV tests for different electrodes (C), EIS curves (D) and the corresponding resistance (E) of different electrodes for probe [Fe(CN)\u003csub\u003e6\u003c/sub\u003e]\u003csup\u003e3\u0026minus;/4\u0026minus;\u003c/sup\u003e, and DPV curves of electrodes in PBS (pH = 7) containing 0.1 \u0026mu;M DA (F).\u003c/p\u003e\n\u003cp\u003eTo investigate the electrochemical properties, CV studies were performed on bare GCE, CNTs/Ag/GCE, MIP/CNTs/Ag/GCE prior to and subsequent to elution, and NIP/CNTs/Ag/GCE electrodes subsequent to elution in a 5 mM [Fe(CN)\u003csub\u003e6\u003c/sub\u003e]\u003csup\u003e3\u0026minus;/4\u0026minus;\u003c/sup\u003e solution with 0.1 M KCl. In Figure 3A and B, redox peaks established for all electrodes, but the heights of the peaks varied with regard to the material used. Compared to the bare GCE, CNTs/Ag/GCE\u0026apos;s peak current responsiveness was significantly higher (44 and -60 \u0026mu;A compared to 33 and -41 \u0026mu;A of GCE). Concurrently, the CNTs/Ag/GCE redox potential difference (\u0026Delta;E\u003csub\u003ep\u003c/sub\u003e, 0.115 V) was less than the bare GCE (0.182 V) (Figure 3C). This is explained by high electrical conductivity and large surface area of the composite, which also quicken the electrode response kinetics. The currents of MIP/CNTs/Ag/GCE and NIP/CNTs/Ag/GCE prior to elution were smaller than those of bare GCE (oxidation currents are 19 and 15 \u0026mu;A, and reduction currents were \u0026ndash;20 and \u0026ndash;18 \u0026mu;A for MIP/CNTs/Ag/GCE and NIP/CNTs/Ag/GCE, respectively). The peak potential difference of redox was large (\u0026Delta;E\u003csub\u003ep\u003c/sub\u003e was 0.284 and 0.247 V, respectively). In fact, the pre-elution MIP membrane is a relatively dense polymer membrane. Although it is a conductive polymer, its intrinsic properties of the polymer limit its high conductivity, which makes the redox current of the probe low and the electrode reaction kinetics slow. Following elution, templates were eliminated from MIP membranes, creating mimicked cavities that create electron transfer channels. This leads to markedly increased peak current responses, enhanced electrode dynamics, and significantly enhanced peak current signals (reoxidation currents of \u0026ndash;52 and \u0026ndash;41 \u0026mu;A, respectively) (Figure 3B). The potential difference \u0026Delta;E\u003csub\u003ep\u003c/sub\u003e becomes smaller (0.127 V). However, as mentioned above, MIP is a polymer, and after being combined with CNTs/Ag, the electrical conductivity will be reduced to a certain extent. As a result, upon elution, MIP/CNTs/Ag/GCE has a smaller current than CNTs/Ag/GCE, and its potential difference is marginally greater.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe experiment tested each electrode using EIS in order to examine the altered electrodes\u0026apos; electron transfer behavior. The resistance of CNTs/Ag/GCE (200 \u0026Omega;) and MIP/CNTs/Ag/GCE (543 \u0026Omega;) following elution is considerably lower than that of the bare GCE (1207 \u0026Omega;), as shown in Figures 3D and E. This is explained by the composite material\u0026apos;s good conductivity and the creation of \u0026quot;empty cavities\u0026quot; that reduce the impediment in the electronic transmission process. The resistance of MIP/CNTs/Ag/GCE (1615 \u0026Omega;) and NIP/CNTs/Ag/GCE (1133 \u0026Omega;) prior to elution is very high, due to the dense polymer membrane that inhibits electron transmission.\u003c/p\u003e\n\u003cp\u003eNext, we examined the responsiveness of different electrodes to the DA determination. As shown in Figure 3F, response current of DA is spread from large to small in sequence to CNTs/Ag/GCE, MIP/CNTs/Ag/GCE after elution, bare GCE, before elution MIP/CNTs/Ag/GCE and NIP/CNTs/Ag/GCE. This is consistent with the electrical signals of the detected probe. The CNTs/Ag compound material enhances the current signal, and MIP treats the material with better recognition responsiveness.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFigure 4\u003c/strong\u003e CV curves of bare GCE (A) CNTs/Ag/GCE (B) in 5 mM [Fe(CN)\u003csub\u003e6\u003c/sub\u003e]\u003csup\u003e3-/4-\u003c/sup\u003e containing 0.1 M KCl at different scan speeds, the corresponding plots of peak current vs. square root of scan rate (\u0026upsilon;\u003csup\u003e1/2\u003c/sup\u003e) (C) and (D).\u003c/p\u003e\n\u003cp\u003eIn a 0.1 M KCl solution containing 5 mM [Fe(CN)\u003csub\u003e6\u003c/sub\u003e]\u003csup\u003e3\u0026ndash;/4\u0026ndash;\u003c/sup\u003e, the area of electrochemical activity of the bare GCE (Figure 4A) and CNTs/Ag/GCE (Figure 4B) were assessed using CV at varying scanning speeds. The oxidation peak and reduction peak currents grow with scanning speed, indicating that diffusion controls the process. The peak potential shifts simultaneously, with the reduction peak shifting negatively and the oxide peak shifting positively. The peak currents at the anode and cathode are proportional to the square root (\u0026upsilon;\u003csup\u003e1/2\u003c/sup\u003e) of the scanning rate, as seen in Figures 4C and D. In this experiment, the active surface area of altered electrodes was calculated using the Randles-Sevcik equations:\u003c/p\u003e\n\u003cp\u003e\u003cimg src=\"data:image/png;base64,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\"\u003e\u003c/p\u003e\n\u003cp\u003eThe variables in this equation are: A is the area of electrochemical activity; D is a proliferation coefficient (6.7\u0026times;10\u003csup\u003e\u0026ndash;6\u003c/sup\u003e cm\u003csup\u003e2\u003c/sup\u003e s\u003csup\u003e\u0026ndash;1\u003c/sup\u003e); C is [Fe(CN)\u003csub\u003e6\u003c/sub\u003e]\u003csup\u003e3\u0026ndash;/4\u0026ndash;\u003c/sup\u003e, concentration C = 5.0 mM; and n is the number of electrons involved in the reaction in [Fe(CN)\u003csub\u003e6\u003c/sub\u003e]\u003csup\u003e3\u0026ndash;/4\u0026ndash;\u003c/sup\u003e solution (n = 1). According to the inclination of i\u003csub\u003ep\u003c/sub\u003e - \u0026upsilon;\u003csup\u003e1/2\u003c/sup\u003e, the active surface area of the bare electrode and CNTs/Ag/GCE is 0.037 cm\u003csup\u003e2\u003c/sup\u003e and 0.055 cm\u003csup\u003e2\u003c/sup\u003e, respectively. This suggests that the material can increase the active area of electrodes.\u003c/p\u003e\n\u003ch1\u003e3.3 Optimization of experiments\u003c/h1\u003e\n\u003cp\u003e\u003cstrong\u003eFigure\u003c/strong\u003e \u003cstrong\u003e5\u003c/strong\u003e Line chart of the proportion of functional unit to template (A), optimized line graph of polymerization cycles (B), accumulation time (C), DPV curves under variable pHs (D), peak currents vs. pH (E), and fitting line of oxidation potential vs. pH (F).\u003c/p\u003e\n\u003ch2\u003eOptimization of the proportion of functional units and templates\u003c/h2\u003e\n\u003cp\u003eFigure 5A shows the DPV peak current of altered electrodes with various\u0026nbsp;proportion\u0026nbsp;of functional units to template of 1:1, 3:1, 5:1, 7:1, and 9:1, respectively. It is clear that when the ratio is 3:1, the platform responds to the DA with the largest peak reaction. Conversely, when the proportion is 1:1, the amount of templates is relatively less, making it impossible to effectively polymerize to form a uniform continuous membrane, which results in a reduced effective identifying point and a decreased current. As a result, the peak electric current response decreases as the single unit proportion increases, a decrease may be attributed to the reduced template molecule, which decreases the number of printed empty cavities. However, because the functional unit is overweight and the templates are insufficient, the MIP membrane that forms is overly dense, which lowers conductivity and, as a result, lowers current.\u003c/p\u003e\n\u003ch2\u003eOptimization of the number of polymerization cycles\u003c/h2\u003e\n\u003cp\u003eFigure 5B illustrates our analysis of the DPV peak current response at 10, 12, 14, 16, and 18 of polymerization cycles. The platform\u0026apos;s maximal response to the DA reaches its maximum at 14 cycles, and the peak reaction declines as the number of polymerization cycles rises. This is because a higher polymerization cycle results in a thicker MIP membrane, which makes elution more difficult and prevents electronic transmission. At 10 and 12 cycles, on the other hand, a thinner MIP membrane due to an insufficient number of polymerization cycles causes the membrane\u0026apos;s effective printing points to be too few, potentially damaging the membrane\u0026apos;s structure during the elution and removal process.\u003c/p\u003e\n\u003ch2\u003eOptimization of incubation time\u003c/h2\u003e\n\u003cp\u003eWe examined the DPV peak current response for the altered electrodes incubated in the PBS containing 0.01 mM DA for 30, 60, 90, 120, and 150 s, respectively, as Figure 5C illustrates. Peak current increases over the course of the incubation period, peaking at 120 s. The peak current then starts to decrease and eventually stays the same, indicating that after incubation on the electrode surface for 120 s, DA has reached absorption balance. Thus, 120 s is the ideal incubation period for this experiment.\u003c/p\u003e\n\u003ch2\u003epH optimization\u0026nbsp;\u003c/h2\u003e\n\u003cp\u003eBecause the pH of PBS will influence the detection of DA, we conducted DPV tests on the platform to determine DA in various pH solutions. As seen in Figure 5D, the proton\u0026apos;s function in the electrochemical reaction process is responsible for the peak current response reaching its maximum at pH7. Electrochemical reactions become more challenging when the pH rises or falls due to an excess or shortage of protons. Figure 5F displays a linear overview of DA\u0026apos;s peak voltage and peak current. This observation implies that the proton played a role in the DA\u0026apos;s electrochemical reaction. The equation for E\u003csub\u003epa\u003c/sub\u003e linear regression with pH is E\u003csub\u003epa\u003c/sub\u003e (V) = 0.4809 - 0.0467 pH (R\u003csup\u003e2\u003c/sup\u003e = 0.9994). The absolute value of its inclination (0.0467 V pH\u003csup\u003e\u0026ndash;1\u003c/sup\u003e) is almost exactly identical to the theoretical value (0.059 V pH\u003csup\u003e\u0026ndash;1\u003c/sup\u003e), indicating that the quantity of protons and electrons involved in the redox reaction is equal.\u003c/p\u003e\n\u003ch2\u003e3.4 Linear range\u003c/h2\u003e\n\u003cp\u003e\u003cstrong\u003eFigure 6\u003c/strong\u003e DPV of DA with concentrations of 0.008, 0.03, 0.05, 0.07, 0.09, 0.1, 3, 5, 10, 40, 60, and 100 \u0026mu;M (A), and calibration plot of DA (0.008 - 0.1 \u0026mu;M) (B) (3 - 100 \u0026mu;M) (C).\u003c/p\u003e\n\u003cp\u003eTo evaluate the sensitivity of the MIP platform, the peak current intensity of the platform towards DA at different concentrations was examined under optimal conditions using DPV tests. The oxide peak current increases as the concentration of DA increases, as seen in Figure 6A. The oxide peak currents and DA concentrations between 0.008 - 0.1 \u0026mu;M and 3 - 100 \u0026mu;M have linear relationship. Ip (\u0026mu;A) = 0.17733C (\u0026mu;M) + 9.51903 (R\u003csup\u003e2\u003c/sup\u003e = 0.9945) is the linear combination of the DA concentration with the response peak current at 3 - 100 \u0026mu;M. Ip (\u0026mu;A) = 43.49299C (\u0026mu;M) + 3.89407 (R\u003csup\u003e2\u003c/sup\u003e = 0.9949) is the linear equation of the DA concentration with the response peak current at 0.008 - 0.1 \u0026mu;M. The platform acquired a 0.003 \u0026mu;M (S/N = 3) determination limit.\u003c/p\u003e\n\u003cp\u003eFrom Table 1, the MIP/CNTs/Ag/GCE performs on par with or better than other modified electrodes. There are two possible reasons for the improvement in the determination performance: (1) CNTs/Ag, prepared with the local restoration method as a printing support material, the excellent electrocatalysis properties of metal nanoparticles themselves and the good thermal stability after compounding with carbon materials make the platform have extremely high conductivity and stability; (2) the structure of the MIP/CNTs/Ag composition that forms a large surface area is conducive to the formation of more printing spots, so that more DA molecules can be absorbed during the electrolysis process.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 1\u003c/strong\u003e Comparison of the DA with other published work\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"848\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"44.62809917355372%\"\u003e\n \u003cp\u003e\u003cstrong\u003eAltered materials\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.035419126328216%\"\u003e\n \u003cp\u003e\u003cstrong\u003eElectrode\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.160566706021251%\"\u003e\n \u003cp\u003e\u003cstrong\u003eMethods\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.521841794569067%\"\u003e\n \u003cp\u003e\u003cstrong\u003eLinear range/\u0026mu;M\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.85478158205431%\"\u003e\n \u003cp\u003e\u003cstrong\u003eLOD/\u0026mu;M\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.799291617473436%\" colspan=\"2\"\u003e\n \u003cp\u003e\u003cstrong\u003eReferences\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"44.62809917355372%\" valign=\"top\"\u003e\n \u003cp\u003eAuNPs/rGO\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.035419126328216%\" valign=\"top\"\u003e\n \u003cp\u003eGCE\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.160566706021251%\" valign=\"top\"\u003e\n \u003cp\u003eDPV\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.521841794569067%\" valign=\"top\"\u003e\n \u003cp\u003e0.05-10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.85478158205431%\" valign=\"top\"\u003e\n \u003cp\u003e0.017\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.799291617473436%\" colspan=\"2\" valign=\"top\"\u003e\n \u003cp\u003e41\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"44.62809917355372%\" valign=\"top\"\u003e\n \u003cp\u003ePt\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.035419126328216%\" valign=\"top\"\u003e\n \u003cp\u003eGCE\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.160566706021251%\" valign=\"top\"\u003e\n \u003cp\u003eDPV\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.521841794569067%\" valign=\"top\"\u003e\n \u003cp\u003e0.01-0.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.85478158205431%\" valign=\"top\"\u003e\n \u003cp\u003e0.0033\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.799291617473436%\" colspan=\"2\" valign=\"top\"\u003e\n \u003cp\u003e43\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"44.62809917355372%\" valign=\"top\"\u003e\n \u003cp\u003eAuNPs/CNTs\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.035419126328216%\" valign=\"top\"\u003e\n \u003cp\u003eGCE\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.160566706021251%\" valign=\"top\"\u003e\n \u003cp\u003eDPV\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.521841794569067%\" valign=\"top\"\u003e\n \u003cp\u003e0.0005-1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.85478158205431%\" valign=\"top\"\u003e\n \u003cp\u003e0.00016\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.799291617473436%\" colspan=\"2\" valign=\"top\"\u003e\n \u003cp\u003e47\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"44.575471698113205%\" valign=\"top\"\u003e\n \u003cp\u003eBiomass carbon/MOF-derived Co\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e/FeCo\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.023584905660377%\" valign=\"top\"\u003e\n \u003cp\u003eGCE\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.14622641509434%\" valign=\"top\"\u003e\n \u003cp\u003eDPV\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.504716981132075%\" valign=\"top\"\u003e\n \u003cp\u003e0.1 - 250\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.84433962264151%\" valign=\"top\"\u003e\n \u003cp\u003e0.1 - 250\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.787735849056604%\" valign=\"top\"\u003e\n \u003cp\u003e48\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"0.1179245283018868%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"44.575471698113205%\" valign=\"top\"\u003e\n \u003cp\u003eMoS\u003csub\u003e2\u003c/sub\u003e/poly(3,4-ethylenedioxythiophene)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.023584905660377%\" valign=\"top\"\u003e\n \u003cp\u003eGCE\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.14622641509434%\" valign=\"top\"\u003e\n \u003cp\u003eDPV\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.504716981132075%\" valign=\"top\"\u003e\n \u003cp\u003e0.1 - 250\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.84433962264151%\" valign=\"top\"\u003e\n \u003cp\u003e0.52\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.787735849056604%\" valign=\"top\"\u003e\n \u003cp\u003e49\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"0.1179245283018868%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"44.575471698113205%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026alpha;-MnO\u003csub\u003e2\u003c/sub\u003e/Rutile TiO\u003csub\u003e2\u003c/sub\u003e composite\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.023584905660377%\" valign=\"top\"\u003e\n \u003cp\u003eGCE\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.14622641509434%\" valign=\"top\"\u003e\n \u003cp\u003eDPV\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.504716981132075%\" valign=\"top\"\u003e\n \u003cp\u003e0.012 - 3.64 \u0026amp;\u003c/p\u003e\n \u003cp\u003e4.84 - 90\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.84433962264151%\" valign=\"top\"\u003e\n \u003cp\u003e3.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.787735849056604%\" valign=\"top\"\u003e\n \u003cp\u003e50\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"0.1179245283018868%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"44.575471698113205%\" valign=\"top\"\u003e\n \u003cp\u003eHierarchical manganese dioxide nanoflower/multiwalled carbon nanotube\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.023584905660377%\" valign=\"top\"\u003e\n \u003cp\u003eElectrochemically pretreated GCE\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.14622641509434%\" valign=\"top\"\u003e\n \u003cp\u003eDPV\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.504716981132075%\" valign=\"top\"\u003e\n \u003cp\u003e0.5 - 30.0\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.84433962264151%\" valign=\"top\"\u003e\n \u003cp\u003e0.17 \u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.787735849056604%\" valign=\"top\"\u003e\n \u003cp\u003e51\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"0.1179245283018868%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"44.575471698113205%\" valign=\"top\"\u003e\n \u003cp\u003eSulfur vacancy (Sv) rich MoS\u003csub\u003e2\u003c/sub\u003e-CNTs with coaxial hierarchical structure and highly dispersed active gold particles (Au-Sv-MoS\u003csub\u003e2\u003c/sub\u003e-CNTs)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.023584905660377%\" valign=\"top\"\u003e\n \u003cp\u003eGCE\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.14622641509434%\" valign=\"top\"\u003e\n \u003cp\u003eDPV\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.504716981132075%\" valign=\"top\"\u003e\n \u003cp\u003e0.002 - 100\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.84433962264151%\" valign=\"top\"\u003e\n \u003cp\u003e0.002\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.787735849056604%\" valign=\"top\"\u003e\n \u003cp\u003e52\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"0.1179245283018868%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"44.575471698113205%\" valign=\"top\"\u003e\n \u003cp\u003eHierarchical nanoporous (HNP) PtTi alloy\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.023584905660377%\" valign=\"top\"\u003e\n \u003cp\u003eGCE\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.14622641509434%\" valign=\"top\"\u003e\n \u003cp\u003eDPV\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.504716981132075%\" valign=\"top\"\u003e\n \u003cp\u003e4 - 500\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.84433962264151%\" valign=\"top\"\u003e\n \u003cp\u003e/\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.787735849056604%\" valign=\"top\"\u003e\n \u003cp\u003e53\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"0.1179245283018868%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"44.575471698113205%\" valign=\"top\"\u003e\n \u003cp\u003eAu nanoplates and reduced graphene oxide (RGO)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.023584905660377%\" valign=\"top\"\u003e\n \u003cp\u003eGCE\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.14622641509434%\" valign=\"top\"\u003e\n \u003cp\u003eDPV\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.504716981132075%\" valign=\"top\"\u003e\n \u003cp\u003e6.8 - 41\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.84433962264151%\" valign=\"top\"\u003e\n \u003cp\u003e1.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.787735849056604%\" valign=\"top\"\u003e\n \u003cp\u003e54\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"0.1179245283018868%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"44.575471698113205%\" valign=\"top\"\u003e\n \u003cp\u003eReduced graphene oxide-zinc oxide (RGO\u0026ndash;ZnO) composite\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.023584905660377%\" valign=\"top\"\u003e\n \u003cp\u003eGCE\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.14622641509434%\" valign=\"top\"\u003e\n \u003cp\u003eDPV\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.504716981132075%\" valign=\"top\"\u003e\n \u003cp\u003e3 - 330\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.84433962264151%\" valign=\"top\"\u003e\n \u003cp\u003e1.08\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.787735849056604%\" valign=\"top\"\u003e\n \u003cp\u003e55\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"0.1179245283018868%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"44.575471698113205%\" valign=\"top\"\u003e\n \u003cp\u003eElectrochemically reduced graphene oxide\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.023584905660377%\" valign=\"top\"\u003e\n \u003cp\u003eGCE\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.14622641509434%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.504716981132075%\" valign=\"top\"\u003e\n \u003cp\u003e0.5 - 60\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.84433962264151%\" valign=\"top\"\u003e\n \u003cp\u003e250\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.787735849056604%\" valign=\"top\"\u003e\n \u003cp\u003e56\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"0.1179245283018868%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"44.575471698113205%\" valign=\"top\"\u003e\n \u003cp\u003eCopper terephthalate metal\u0026ndash;organic framework, GO = graphene oxide\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.023584905660377%\" valign=\"top\"\u003e\n \u003cp\u003eGCE\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.14622641509434%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.504716981132075%\" valign=\"top\"\u003e\n \u003cp\u003e1 - 50\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.84433962264151%\" valign=\"top\"\u003e\n \u003cp\u003e0.21\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.787735849056604%\" valign=\"top\"\u003e\n \u003cp\u003e57\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"0.1179245283018868%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"44.575471698113205%\" valign=\"top\"\u003e\n \u003cp\u003ePolypyrrole MIP/gold-nanowires\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.023584905660377%\" valign=\"top\"\u003e\n \u003cp\u003eGCE\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.14622641509434%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.504716981132075%\" valign=\"top\"\u003e\n \u003cp\u003e0.4 - 10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.84433962264151%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.787735849056604%\" valign=\"top\"\u003e\n \u003cp\u003e58\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"0.1179245283018868%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"44.575471698113205%\" valign=\"top\"\u003e\n \u003cp\u003eFunctional thia-bilane structure (product of addition reaction of tripyrrane 1 to nitrovinyl thiophene 2 in the presence of molecular iodine) MIP film\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.023584905660377%\" valign=\"top\"\u003e\n \u003cp\u003ePencil graphite electrode\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.14622641509434%\" valign=\"top\"\u003e\n \u003cp\u003eDPV\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.504716981132075%\" valign=\"top\"\u003e\n \u003cp\u003e0.05 - 250\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.84433962264151%\" valign=\"top\"\u003e\n \u003cp\u003e0.020\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.787735849056604%\" valign=\"top\"\u003e\n \u003cp\u003e59\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"0.1179245283018868%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"44.575471698113205%\" valign=\"top\"\u003e\n \u003cp\u003eGraphene/MIP\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.023584905660377%\" valign=\"top\"\u003e\n \u003cp\u003eGold electrode\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.14622641509434%\" valign=\"top\"\u003e\n \u003cp\u003eDPV\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.504716981132075%\" valign=\"top\"\u003e\n \u003cp\u003e0.1 - 10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.84433962264151%\" valign=\"top\"\u003e\n \u003cp\u003e0.033\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.787735849056604%\" valign=\"top\"\u003e\n \u003cp\u003e60\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"0.1179245283018868%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"44.575471698113205%\" valign=\"top\"\u003e\n \u003cp\u003eMIP of poly-bromophenol blue\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.023584905660377%\" valign=\"top\"\u003e\n \u003cp\u003eGCE\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.14622641509434%\" valign=\"top\"\u003e\n \u003cp\u003eDPV\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.504716981132075%\" valign=\"top\"\u003e\n \u003cp\u003e0 - 1.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.84433962264151%\" valign=\"top\"\u003e\n \u003cp\u003e0.000162\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.787735849056604%\" valign=\"top\"\u003e\n \u003cp\u003e61\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"0.1179245283018868%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"44.62809917355372%\" valign=\"top\"\u003e\n \u003cp\u003eMIP/CNTs/Ag\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.035419126328216%\" valign=\"top\"\u003e\n \u003cp\u003eGCE\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.160566706021251%\" valign=\"top\"\u003e\n \u003cp\u003eDPV\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.521841794569067%\" valign=\"top\"\u003e\n \u003cp\u003e0.008-0.1 \u0026amp; 3 - 100\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.85478158205431%\" valign=\"top\"\u003e\n \u003cp\u003e0.003\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.799291617473436%\" colspan=\"2\" valign=\"top\"\u003e\n \u003cp\u003eThis work\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003c/p\u003e\n\u003ch2\u003e3.5 Selectiveness, resistance to interference and reproducibility\u003c/h2\u003e\n\u003cp\u003eSelectiveness, interference resistance, and repeatability were investigated in order to evaluate the viability of the platform. A key performance indicator for the molecular imprint platform is selectivity. The DPV peak current response to acetaminophenol, glucose, and uric acid is displayed in Figure 7A. The MIP electrode and the NIP electrodes can both determine a concentration of 0.01 mM dopamine. It is evident that, when the test material is for acetaminophenol, glucose, and\u0026nbsp;uric acid, the difference in peak response determined by NIP and NIP electrolyte is very small, and when the testing object is DA, the difference of the two current responses is clearly visible. MIP current is far higher than NIP, and the printing factor is 5.56 (IF = I\u003csub\u003eMIP\u003c/sub\u003e/I\u003csub\u003ePIN\u003c/sub\u003e), indicating that the platform has good selectiveness.\u0026nbsp;We employed DPV technology, as demonstrated in Figure 7B, to confirm the prepared platform\u0026apos;s reproducibility. The measurement yielded a relative standard deviation (RSD) of 4.2% when five electrodes were used in parallel. These results indicate that the MIP platform exhibits good repeatability. The inorganic salt ions of Na\u003csup\u003e+\u003c/sup\u003e, K\u003csup\u003e+\u003c/sup\u003e, Cl\u003csup\u003e-\u003c/sup\u003e, and NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e2-\u003c/sup\u003e with 50 times concentration of DA, almost has no effect on the detection current (Figure 7C), meaning the platform has desired freedom from jamming of inorganic salt ions.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFigure 7\u003c/strong\u003e Histogram of DPV response of MIP and NIP platforms to DA (0.01 mM) and structural analogs or coexisted substances (acetaminophen (AP), glucose (GL), uric acid (UA), 0.01 mM) (A), DPV peak current diagram of parallel 5 MIP/CNTs/Ag/GCE electrodes (B), and currents in the presence of inorganic salt ions (Na\u003csup\u003e+\u003c/sup\u003e, K\u003csup\u003e+\u003c/sup\u003e, Cl\u003csup\u003e-\u003c/sup\u003e, NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e-\u003c/sup\u003e) with a concentration of 50 times the DA concentration (C).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 2\u003c/strong\u003e Test results of real samples with marking method\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"570\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"20%\"\u003e\n \u003cp\u003e\u003cstrong\u003eSamples\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\"\u003e\n \u003cp\u003e\u003cstrong\u003eAdded (\u0026mu;M)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\"\u003e\n \u003cp\u003e\u003cstrong\u003eFound (\u0026mu;M)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\"\u003e\n \u003cp\u003e\u003cstrong\u003eRecovery (%)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\"\u003e\n \u003cp\u003e\u003cstrong\u003eRSD (%) n\u003c/strong\u003e=\u003cstrong\u003e5\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"20%\"\u003e\n \u003cp\u003eUrine\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\"\u003e\n \u003cp\u003e1.11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\"\u003e\n \u003cp\u003e111.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\"\u003e\n \u003cp\u003e7.31\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"20%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\"\u003e\n \u003cp\u003e5.34\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\"\u003e\n \u003cp\u003e106.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\"\u003e\n \u003cp\u003e5.16\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"20%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\"\u003e\n \u003cp\u003e10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\"\u003e\n \u003cp\u003e10.72\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\"\u003e\n \u003cp\u003e107.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\"\u003e\n \u003cp\u003e3.27\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"20%\"\u003e\n \u003cp\u003eSerum\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\"\u003e\n \u003cp\u003e0.92\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\"\u003e\n \u003cp\u003e92.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\"\u003e\n \u003cp\u003e6.53\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"20%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\"\u003e\n \u003cp\u003e4.37\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\"\u003e\n \u003cp\u003e87.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\"\u003e\n \u003cp\u003e4.84\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"20%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\"\u003e\n \u003cp\u003e10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\"\u003e\n \u003cp\u003e9.61\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\"\u003e\n \u003cp\u003e96.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\"\u003e\n \u003cp\u003e2.95\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003ch2\u003e3.6 Spiked Real Sample Tests\u003c/h2\u003e\n\u003cp\u003eIn this investigation, we used the spiked approach to compute and assess the recovery rate of DA in urine and serum. The sealed normal human serum was bought from KOIZEE Scientific Lab\u0026apos;s, and the urine was obtained from the healthy participants in our lab. 100 mL PBS (pH = 7) was used to dissolve 1.53 mg of DA, creating a mother solution with a 0.1 mM DA solubility. The 9.5 mL PBS solution was diluted with mother liquor, and 0.5 mL urine and serum were added. The mixture was well-shook, and PBS solutions with DA concentrations of 1, 5, and 10 \u0026mu;M were created. The DPV tests were run after the mixture was uniform. The test results in Table 2 demonstrate that, despite DA molecular imprinting being done to improve the ability of the altered electrode to recognize and adsorb DA, the recovery rate in urine is normally high and is impacted by the presence of uric acid in the urine. However, because there are some non-specific adsorption sites in MIP membranes and because DA and uric acid have similar oxidation potentials, DA recovery rates in urine are typically higher than 100%. Five parallel tests yield a relative standard deviation of 3.27%-7.31%. The recovery rates in serum are all lower than 100%, ranging from 87.4%-96.1%, and the relative standard deviation of five determinations is 2.95%-6.53%.\u003c/p\u003e"},{"header":"4. Conclusions","content":"\u003cp\u003eThis study used the in-situ reduction method to prepare CNTs/Ag composites and drop coating and electropolymerization to construct MIP/CNTs/Ag/GCE. The template molecule used in this process was DA, the composite functional unit was resorcinol, and the conductive catalytic material was the CNTs/Ag composite. On GCE, a molecularly imprinted electrochemical platform with a DA-specific recognition function was created. The enhanced electrochemical catalytic reaction rate is facilitated by the good synergistic catalytic effect of Ag composites with CNTs. The findings of the electrochemical test demonstrate that the enhanced electrode\u0026apos;s electrical conductivity was derived from the high electrical conductivity CNTs/Ag composites. The platform shows good DA selectivity and sensitivity because to the enhanced specific surface area and synergistic catalysis of the conductive carrier material. After optimizing the ratio of the functional unit to template molecule, the number of electropolymerization cycles, the pH, and the incubation duration, the linear DA determination range and linear determination limit of the platform are 0.008 - 0.1 \u0026mu;M and 3 - 100 \u0026mu;M, respectively. Furthermore, the platform exhibits good repeatability and anti-interference properties. The indicated spiking samples had a high sample recovery rate. A reference for the extraction, separation, and determination of DA is given by this work.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eFinancial supports from the National Natural Science Foundation of China (22164003), the Natural Science Foundation of Gansu Province (23JRRA1228), the Higher Education Innovation Fund Project of Gansu Province (2023A-097, 2021B-177), the Science and Technology Major Project of Gansu Province (21ZD4FA032), and the Key Talent Project of Gansu Province (2022RCXM085) are gratefully acknowledged.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCredit author statements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eShufang Ren: Validation, Writing\u0026ndash;review \u0026amp; editing, Funding acquisition.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eJunpeng Zhao: Investigation, Material preparation, Formal analysis. Data curation, Writing\u0026ndash;original draft.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eXiaohang Liu: Writing\u0026ndash;original draft, Writing\u0026ndash;review \u0026amp; editing.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eYahui Liu: Writing\u0026ndash;review \u0026amp; editing.\u003c/p\u003e\n\u003cp\u003eYuan Zhang: Funding acquisition.\u003c/p\u003e\n\u003cp\u003eZhixiang Zheng: Funding acquisition, Supervision.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDeclaration of competing interest \u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing financial interest.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSupplementary information\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot Applicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData and code availability:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe data that support the findings of this study are available from the corresponding author upon reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthical approval:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot Applicable\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eMa, X.; Gao, F.; Dai, R.; Liu, G.; Zhang, Y.; Lu, L.; Yu, Y. 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A Molecular Imprinted Electrochemical Sensor For Selectively and Electro-catalytically Voltammetric Determination of Dopamine. \u003cem\u003eActa Chimica Sinica \u003c/em\u003e\u003cstrong\u003e2013,\u003c/strong\u003e\u003cem\u003e71\u003c/em\u003e (6), 951.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Molecularly imprinted polymer, Dopamine, Multi-walled carbon nanotubes, Silver nanoparticles, Voltammetry sensing platform ","lastPublishedDoi":"10.21203/rs.3.rs-3977624/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-3977624/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"The most prevalent catecholamine neurotransmitter of brain, dopamine (DA), is crucial to the operation of the hormone, blood vessel, and central nervous system systems. The effective determination of dopamine by means of advanced, efficient, and sensitive determination techniques has attracted much attention. This experiment designed and prepared a molecularly imprinted electroanalytical determination platform for the determination of DA. In this work, silver nanoparticles (Ag NPs) were in-situ carried on the walls of multiwalled carbon nanotube (CNTs) using sodium borohydride (NaBH4) as a reducing agent. The CNTs/Ag/GCE altered electrode was prepared using a simple drop-casting method. Molecularly imprinted polymer (MIP) membranes towards recognizing DA molecules were prepared on altered electrode surfaces using electropolymerization using resorcinol as the functional unit and dopamine (DA) as the template molecule. The cooperative effect of Ag and CNTs boosted the conductivity as well as the electrocatalytic efficiency, thereby enhancing the sensitivity to electrochemical response of the platform and reducing the determination limit. After optimizing the parameters, including the proportion of templates to functional units, electropolymerization cycles, incubation time, and pH, the platform's linear determination range for DA was 0.008 - 0.1 μM and 3 - 100 μM, with a 0.003 μM determination limit. Additionally, the platform exhibits great selectivity, anti-interference, and reproducibility. The sample recovery rate for spiked real samples, urine and serum, was good. This study provides a reference for the extraction, separation, and determination of DA.","manuscriptTitle":"MWCNTs/Ag-enhanced Molecularly Imprinted Resorcinol Polymer Voltammetric Sensing Platform for Dopamine Determination","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-02-23 11:21:33","doi":"10.21203/rs.3.rs-3977624/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"40e592ca-0e5c-4e6d-a706-ce4cd4d58924","owner":[],"postedDate":"February 23rd, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2024-09-26T01:23:15+00:00","versionOfRecord":[],"versionCreatedAt":"2024-02-23 11:21:33","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-3977624","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-3977624","identity":"rs-3977624","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}