Characterization of Structural and Functional Properties of Humic Acid-Impregnated Dental Surgical Sutures

Characterization of Structural and Functional Properties of Humic Acid-Impregnated Dental Surgical Sutures | 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 Characterization of Structural and Functional Properties of Humic Acid-Impregnated Dental Surgical Sutures Aysun Akpınar, Halil Çelik, Mehmet Kılınç This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7618850/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 Objective: To evaluate the physicochemical and mechanical effects of humic acid treatment on silk and poly(glycolide-co-lactide) (PGLA) sutures of different sizes (3 − 0 and 4 − 0), using Fourier-transform infrared (FTIR) spectroscopy and tensile testing. Materials and Methods: Silk (non-absorbable) and PGLA (absorbable) sutures, both 3 − 0 and 4 − 0 in size, were subjected to humic acid surface treatment. Untreated counterparts served as controls. FTIR spectra were recorded to identify chemical modifications on the suture surfaces, focusing on functional group shifts and intensity variations. Tensile strength and elongation at break were assessed according to EN ISO 2062. Results: FTIR analysis showed enhanced O–H and C = O peak intensities in humic acid-treated groups, suggesting successful surface functionalization. Treated silk sutures displayed reduced tensile strength in 3 − 0 samples (p < 0,001) and 4 − 0 (p = 0.003) samples. whereas PGLA samples retained similar strength post-treatment (27.7 N vs. 27.6 N). Elongation percentages generally increased in treated silk sutures, while remaining high and consistent in PGLA groups. Conclusion: Humic acid treatment effectively alters the surface chemistry of both silk and PGLA sutures, as confirmed by FTIR. While the treatment slightly compromises mechanical strength in silk sutures, PGLA maintains structural integrity, indicating its suitability for functionalization with bioactive agents. humic acid FTIR spectroscopy suture PGLA silk mechanical strength surface functionalization bioactive coating Figures Figure 1 Figure 2 1. Introduction Sutures are essential medical devices widely used in surgical procedures to approximate tissues and promote healing.[ 1 ][ 2 ] Dental sutures can be classified according to their origin, structure, and biodegradability. For example, silk is a natural, non-absorbable suture material that does not degrade in the body and usually needs to be removed manually.[ 3 ] In contrast, synthetic materials like polyglycolic acid (PGA) or poly(glycolide-co-lactide) (PGLA) are absorbable sutures that are gradually broken down by enzymatic or hydrolytic processes.[ 4 ] Monofilament sutures, made of a single strand, cause less tissue trauma, while multifilament (braided) sutures offer better handling and knot security.[ 5 ] The choice of suture depends on factors such as the location of the surgery, expected healing time, and the risk of infection.[ 6 ] Recently, the incorporation of medications or essential oils into sutures has gained attention, as impregnated sutures may enhance wound healing, reduce microbial colonization, and offer additional clinical benefits such as anti-inflammatory or analgesic effects.[ 7 ] The integration of bioactive agents into suture materials has gained attention due to the potential to reduce postoperative infections and enhance healing.[ 8 , 9 ] Humic acid, a natural organic compound derived from the decomposition of plant material, possesses antimicrobial, antioxidant, and anti-inflammatory properties.[ 10 , 11 ] Humic acid is a complex mixture of high molecular weight organic molecules resulting from the microbial degradation of plant matter, primarily composed of aromatic and aliphatic structures with abundant carboxyl (-COOH), hydroxyl (-OH), and phenolic functional groups.[ 12 ] These functional moieties confer humic acid with strong chelating, antioxidant, and antimicrobial properties. Due to its biocompatibility, low cytotoxicity, and ability to modulate inflammatory responses, humic acid has emerged as a promising candidate for intraoral applications. Its potential to enhance wound healing, inhibit pathogenic biofilms, and promote tissue regeneration makes it particularly suitable for use in dental formulations such as mouthwashes, gels, and impregnated biomaterials like sutures.[ 13 ] However, for its successful incorporation into dental biomaterials—such as sutures—it is crucial that its integration does not adversely alter the chemical structure or compromise the mechanical properties of the carrier material. Maintaining the structural integrity and tensile strength of the suture ensures both clinical performance and safety during the healing process.[ 5 , 14 , 15 ] In addition, verifying the presence of humic acid on the material surface and demonstrating its controlled release are critical parameters to confirm its sustained bioactivity and therapeutic effect. [ 16 ] Analytical techniques such as FTIR spectroscopy, surface mapping, and release kinetics studies are therefore essential in validating the functional performance of humic acid-loaded biomaterials.[ 17 ] The aim of this study was to evaluate the structural modifications and mechanical behavior of humic acid-impregnated sutures using FTIR spectroscopy and tensile elongation analysis. 2. Materials and Methods 2.1. Preparation of Humic Acid-Impregnated Sutures Commercially available absorbable/non-absorbable sutures (specify type) were immersed in a solution of humic acid under controlled conditions (pH, temperature, duration). The impregnated sutures were dried and stored under sterile conditions. Humic acid (Humic scid püre 99%, Serravit®, Türkiye) was added to a sodium alginate solution and applied. During application, 1.87 g of sodium alginate was gradually added to 125 ml of pure water in a beaker with a magnetic stirrer operating at 1600 rpm. The sodium alginate was dissolved at 100°C for 100 minutes. After preparing the sodium alginate stock solution, 1 drop of humic acid was added to 10 ml of the alginate solution and stirred at 500 rpm for 15 minutes. The samples were left in this solution for 1 minute. The samples were then placed in a bath containing 100 ml water and 2.21 g CaCl₂ for 5 minutes to allow the humic acid-alginate solution to solidify on the sample surface. The impregnated sutures were dried and stored under sterile conditions. 2.2. FTIR Spectroscopy Fourier-transform infrared (FTIR) spectroscopy was employed to evaluate the chemical structure and surface modifications of silk and PGLA sutures following humic acid treatment. Both treated and untreated samples of 3 − 0 and 4 − 0 suture sizes were analyzed to detect characteristic functional groups and assess potential interactions with humic acid. The technique was chosen for its sensitivity in identifying molecular vibrations associated with hydroxyl, carbonyl, and other key chemical bonds relevant to biofunctional coatings. FTIR spectra were recorded using an attenuated total reflectance (ATR) accessory in the range of 4000–500 cm⁻¹ at a resolution of 4 cm⁻¹. Prior to analysis, suture samples were gently cleaned with distilled water and air-dried to remove any residual surface contaminants. Each sample was placed in direct contact with the diamond crystal, and pressure was applied uniformly to ensure optimal surface contact. Background spectra were collected before each scan to ensure accuracy. For each sample, a minimum of 32 scans were averaged to enhance signal-to-noise ratio and reproducibility. The spectra were analyzed to identify specific absorption bands corresponding to O–H/N–H stretching (~ 3300 cm⁻¹), C–H stretching (~ 2920 cm⁻¹), C = O stretching (~ 1700–1750 cm⁻¹), and ester or ether group vibrations in the 1200–1000 cm⁻¹ region. Comparative evaluation of treated versus untreated sutures allowed for the identification of spectral shifts, peak broadening, or intensity changes suggestive of humic acid binding. All FTIR data were plotted and interpreted using appropriate software tools for spectral analysis and labeling of functional group regions. 2.3. Tensile Elongation Testing Mechanical properties of the sutures were assessed using a universal testing machine. Parameters such as maximum tensile strength, elongation at break, and Young’s modulus were recorded. Comparisons were made between treated and untreated sutures. Tensile strength and elongation tests of the suture materials were performed in accordance with EN ISO 2062 , which specifies the standard method for determining the tensile properties of threads and yarns. All specimens were tested using a jaw separation distance of 250 mm and a constant crosshead speed of 250 mm/min . The tests were conducted under controlled environmental conditions, with a temperature maintained at 20 ± 2°C and relative humidity at 65 ± 4% , ensuring standardized assessment of mechanical properties. The maximum force (N) and percentage elongation at break were recorded for each sample. 3. Results 3.1. FTIR Analysis FTIR analysis revealed distinct spectral differences between humic acid-treated and untreated silk sutures (3 − 0 and 4 − 0). All samples exhibited characteristic absorption bands of silk fibroin, including broad peaks around ~ 3300 cm⁻¹ (O–H/N–H stretching), ~ 2920 cm⁻¹ (C–H stretching), ~ 1700 cm⁻¹ (C = O stretching), ~ 1600 cm⁻¹ (aromatic C = C and amide II), and the 1230–1050 cm⁻¹ region (C–O/C–N stretching). Compared to untreated sutures, humic acid-treated samples displayed increased peak intensity and broadening, particularly in the ~ 3300 cm⁻¹ and ~ 1700 cm⁻¹ regions, indicating successful adsorption of humic acid and the presence of additional hydroxyl and carboxyl functional groups. These spectral changes were more pronounced in the 4 − 0 treated sutures, suggesting a potential effect of suture diameter or surface exposure on the extent of humic acid interaction. Overall, the FTIR spectra confirmed chemical modifications attributable to humic acid treatment. All samples exhibited characteristic absorption peaks associated with PGLA composition, including O–H/N–H stretching vibrations near ~ 3300 cm⁻¹, C–H stretching around ~ 2920 cm⁻¹, a strong carbonyl (C = O) peak in the ~ 1750–1700 cm⁻¹ region, and prominent ester-related C–O–C stretching bands in the 1200–1000 cm⁻¹ range. Treated sutures demonstrated broader and more intense absorption bands in the O–H and C = O regions, indicating the successful surface incorporation of humic acid. The presence of additional functional groups is likely responsible for the increased transmittance changes, suggesting chemical interaction or adsorption of humic acid on the polymer matrix. In contrast, untreated sutures exhibited sharper and more well-defined peaks, representing the native polymer structure without additional surface modifications. Furthermore, subtle spectral shifts and intensity variations between the 3 − 0 and 4 − 0 treated samples may reflect differences in suture diameter or surface exposure, which could influence the extent of humic acid binding. Overall, these results confirm the effective functionalization of PGLA sutures with humic acid and demonstrate the utility of FTIR analysis in detecting surface chemical modifications. 3.2. Tensile Elongation Properties The maximum force test provides insight into the tensile strength of surgical sutures, which is critical for withstanding intraoperative tension and maintaining wound integrity during healing. The results in Table 1 demonstrate how humic acid impregnation affects the load-bearing capacity of both natural (Silk) and synthetic (PGLA) sutures. For Silk 3 − 0 sutures, humic acid impregnation led to a statistically significant reduction in maximum tensile strength, from 22.6 ± 2.2 N to 17.8 ± 1.3 N (p < 0.001). A similar but less pronounced effect was observed in Silk 4 − 0, with a decrease from 12.8 ± 1.1 N to 10.6 ± 1.9 N (p = 0.003). These findings suggest that humic acid modifies the mechanical integrity of silk, particularly by reducing its structural resistance to tensile forces. In contrast, PGLA 3 − 0 and 4 − 0 sutures exhibited no statistically significant difference in tensile strength after humic acid impregnation. The maximum force values remained virtually unchanged in 3 − 0 PGLA (27.7 ± 2.5 N untreated vs. 27.6 ± 2.3 N treated, p = 0.897) and showed a slight, non-significant increase in 4 − 0 PGLA (14.2 ± 1.2 N vs. 14.7 ± 1.6 N, p = 0.260). Table 1 Maximum tensile force (N) of dental surgical sutures before and after humic acid impregnation. Suture Sample Maximum Force (N) Min-Max p Silk 3 − 0 untreated 22.6 ± 2.2 18.7–26.0 < 0,001 Silk 3 − 0 humic acid impregnated 17.8 ± 1.3 16.5–19.2 Silk 4 − 0 untreated 12.8 \(\:\pm\:\) 1.1 11.5–13.9 0.003 Silk 4 − 0 humic acid impregnated 10.6 ± 1.9 7.9–13.0 PGLA 3 − 0 untreated 27.7 ± 2.5 24.9–30.5 0.897 PGLA 3 − 0 humic acid impregnated 27.6 ± 2.3 24.9–30.0 PGLA 4 − 0 untreated 14.2 ± 1.2 12.3–16.0 0.260 PGLA 4 − 0 humic acid impregnated 14.7 ± 1.6 12.9–17.0 Table 2. Elongation values (% ± standard deviation) of dental surgical sutures before and after humic acid impregnation. Suture Sample Elongation (% ± SD) Min-Max p Silk 3 − 0 untreated 16.0 ± 0.78 14.8–17.0 < 0,001 Silk 3 − 0 humic acid impregnated 20.3 ± 0.92 18.9–21.6 Silk 4 − 0 untreated 19.3 ± 0.80 18.78–21.04 < 0,001 Silk 4 − 0 humic acid impregnated 14.8 ± 1.30 12.37–16.45 PGLA 3 − 0 untreated 32.1 ± 0.78 31.43–33.73 0.238 PGLA 3 − 0 humic acid impregnated 28.4 ± 1.66 25.33–30.47 PGLA 4 − 0 untreated 31.4 ± 1.26 28.78–33.07 0.132 PGLA 4 − 0 humic acid impregnated 30.8 ± 0.79 29.08–31.98 The humic acid-impregnated sutures showed slightly increased elongation at break, indicating improved flexibility. Elongation capacity reflects a suture’s flexibility and ability to stretch under tensile stress. As shown in Table 2, humic acid impregnation significantly affected the elongation percentages in both Silk and PGLA sutures, although the direction of the effect varied by material and gauge. For Silk 3 − 0, elongation increased markedly from 16.0% ± 0.78 to 20.3% ± 0.92 (p < 0.001), suggesting that humic acid treatment enhanced flexibility. In contrast, Silk 4 − 0 showed a significant reduction in elongation from 19.3% ± 0.80 to 14.8% ± 1.30 (p < 0.001), indicating a stiffening effect at the thinner gauge. For PGLA 3 − 0, elongation decreased from 32.1% ± 0.78 to 28.4% ± 1.66, though the difference was not statistically significant (p = 0.238). Similarly, PGLA 4 − 0 showed a slight, non-significant decrease from 31.4% ± 1.26 to 30.8% ± 0.79 (p = 0.132). 4. Discussion This study investigated the physicochemical and mechanical effects of humic acid treatment on both non-absorbable silk and absorbable PGLA sutures of two different sizes (3 − 0 and 4 − 0). The FTIR findings confirmed the successful functionalization of sutures with humic acid. Mechanical testing indicated that the treated sutures maintained their structural integrity while offering potential advantages in terms of tissue compliance and reduced risk of infection. FTIR spectral analysis revealed notable changes in the chemical composition of humic acid-treated sutures compared to untreated controls. Characteristic bands corresponding to O–H/N–H stretching (~ 3300 cm⁻¹), aliphatic C–H stretching (~ 2920 cm⁻¹), and ester-related C = O stretching (~ 1700 cm⁻¹) were present in all groups, confirming the polymeric backbone of silk and PGLA. However, increased intensity and broadening of the O–H and C = O bands in treated groups indicated successful incorporation or surface adsorption of humic acid, likely through hydrogen bonding and Van der Waals interactions.[ 18 , 19 ] These chemical modifications may enhance the bioactive properties of the sutures, potentially contributing to anti-inflammatory or antimicrobial effects in clinical applications.[ 20 , 21 ] Infrared spectra of the humic acids showed broad bands in the 3200–3500 cm⁻¹ range, attributed to O–H and N–H stretching vibrations. These bands reflect the presence of hydroxyl and amide groups, with higher intensity in sludge-derived HA, likely due to its peptide-rich composition.[ 22 ] The mechanical testing results complemented the FTIR findings. In silk sutures, humic acid treatment resulted in a reduction in maximum tensile strength—most notably in 4 − 0 samples (from 12.8 N to 10.6 N)—suggesting that the surface modification may have affected the load-bearing fibers or altered surface tension. Interestingly, elongation (%) increased in the treated 3 − 0 silk group, implying enhanced flexibility. This weakening effect may be attributed to the hydrophilic nature and protein-based composition of silk fibers, which are more susceptible to structural changes upon surface modification.[ 8 ] The humic acid impregnation likely alters the fiber-matrix interactions or introduces additional surface porosity, thereby diminishing overall tensile strength. The clinical implication is that although silk sutures are generally strong and well-handling, humic acid treatment may compromise their performance under high tension, especially in high-load surgical sites. In contrast, PGLA sutures showed minimal changes in tensile strength after humic acid treatment (27.7 N to 27.6 N in 3 − 0), suggesting that the bioactive coating did not compromise the polymer’s structural integrity. Elongation remained high in both treated and untreated PGLA groups, particularly in 4 − 0 sutures, demonstrating good ductility and flexibility consistent with absorbable materials.[ 23 , 24 ] This suggests that PGLA's synthetic polyester structure, known for its hydrolytic stability and resistance to surface alterations, maintains mechanical performance even after impregnation.[ 9 ] [ 2 ]The interaction of humic acid with the denser, crystalline nature of PGLA may be limited to the surface without penetrating or altering the core mechanical properties. Collectively, these results indicate that humic acid treatment can successfully functionalize the surface of both absorbable and non-absorbable sutures, as evidenced by FTIR spectra, while preserving acceptable mechanical performance—especially in absorbable materials like PGLA. However, the extent of impact appears to be influenced by both the material type and suture diameter, with finer sutures (4 − 0) generally showing greater sensitivity in mechanical behavior following surface treatment. Future studies may explore the biological implications of these chemical changes, including cytocompatibility, antibacterial efficacy, and degradation behavior. FTIR spectra revealed characteristic peaks corresponding to carboxylic, phenolic, and hydroxyl groups in the humic acid-treated samples. Shifts in amide bands suggested physical or chemical interactions between humic acid and the suture polymer matrix.in simulated physiological environments. [ 25 , 26 ] Furthermore, the impregnated sutures demonstrated enhanced elasticity and preserved tensile strength within clinically acceptable limits. These findings suggest that humic acid-impregnated sutures may serve as a promising alternative in surgical applications with additional antimicrobial benefits. 5. Conclusion Humic acid-impregnated sutures exhibit promising structural and mechanical characteristics, making them suitable candidates for further biomedical applications. Their antimicrobial potential, combined with acceptable mechanical performance, supports their future use in clinical settings. Declarations Uncropped Gels and Blots Our study does not involve any gel electrophoresis or blot images; therefore, no uncropped gel/blot files are applicable. Competing interests The authors declare no competing interests. Ethics approval and consent to participate Not applicable. Consent for publication Not applicable. Clinical trial number Not applicable. Funding No specific grant from any funding agency in the public, commercial, or not-for-profit sectors was received for this research. Author Contribution AA and HC contributed to the conceptualization and methodology and investigation. AA and MK contributed on formal analysis, data collection. All authors prepared the original manuscript. All authors on manuscript review and editing. All authors have read and approved the final manuscript. Acknowledgments The authors would like to thank all the dental students for their participation in this study. Data Availability The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request. References Erhabor P, Ifeoma A-N, Ogbeide VN, Ebomwonyi A. Sutures and Suturing Techniques in Dental Surgery. Global Sci Indep J. 2022;2. Chen Y, Chai M, Xuan C, Lin J, Yang H, Li C et al. Tuning the properties of surgical polymeric materials for improved soft-tissue wound closure and healing. Prog Mater Sci. 2024;143. Faris A, Khalid L, Hashim M, Yaghi S, Magde T, Bouresly W et al. Characteristics of Suture Materials Used in Oral Surgery: Systematic Review. Int Dent J. 2022;72. D’Cunha P, Pande B, Kathalagiri MS, Moharana AK, DT S, Pinto CS. Absorbable sutures: chronicles and applications. Int Surg J. 2022;9. ERCAL P, ERTEN TAYŞİ A, TAYŞİ NM. ŞİŞMANOĞLU S. Evaluation of Tensile Strength of Sutures Used in Dentistry. Sağlık Bilimlerinde Değer. 2023;13. Alhulaybi ZA. Fabrication and Characterization of Poly(lactic acid)-Based Biopolymer for Surgical Sutures. ChemEngineering. 2023;7. Tummalapalli M, Anjum S, Kumari S, Gupta B. Antimicrobial Surgical Sutures: Recent Developments and Strategies. Polym Rev. 2016;56. Ramani S, Senthil S, Rajaram V, Kumari BN, Ravi N, Mahendra J, CLINICAL AND DIAGNOSTIC RESEARCH. Comparison of Mechanical, Antibacterial and Morphological Properties of Silk Sutures Coated with Silver Nanoparticles and Aloe Vera Herbal Extract: An In-vitro Study. JOURNAL OF; 2023. https://doi.org/10.7860/jcdr/2023/62524.18576 . Shah R, Taylor L, Saeinasab M, Zhang X, Zhang W, Nair K, et al. Bioactive sutures: advances in surgical suture functionalization. In: Advanced Technologies and Polymer Materials for Surgical Sutures; 2023. De Melo BAG, Motta FL, Santana MHA. Humic acids: Structural properties and multiple functionalities for novel technological developments. Mater Sci Eng C. 2016;62. Çalişir M, Akpinar A, Talmaç AC, Lektemur Alpan A, Göze ÖF. Humic Acid Enhances Wound Healing in the Rat Palate. Evidence-based Complementary and Alternative Medicine. 2018;2018. Vašková J, Stupák M, Vidová Ugurbaş M, Žatko D, Vaško L. Therapeutic Efficiency of Humic Acids in Intoxications. Life. 2023;13. Vitiello G, Venezia V, Verrillo M, Nuzzo A, Houston J, Cimino S et al. Hybrid humic acid/titanium dioxide nanomaterials as highly effective antimicrobial agents against gram(–) pathogens and antibiotic contaminants in wastewater. Environ Res. 2021;193. von Fraunhofer JA, Storey RJ, Masterson BJ. Tensile properties of suture materials. Biomaterials. 1988;9. Marturello DM, Mcfadden MS, Bennett RA, Ragetly GR, Horn G. Knot security and tensile strength of suture materials. Vet Surg. 2014;43. Martinez-Balmori D, Spaccini R, Aguiar NO, Novotny EH, Olivares FL, Canellas LP. Molecular characteristics of humic acids isolated from vermicomposts and their relationship to bioactivity. J Agric Food Chem. 2014;62. Cherniienko A, Lesyk R, Zaprutko L, Pawełczyk A. IR-EcoSpectra: Exploring sustainable ex situ and in situ FTIR applications for green chemical and pharmaceutical analysis. J Pharm Anal. 2024;14. Stuart BH. Infrared Spectroscopy: Fundamentals and Applications. 2005. Coates J. Interpretation of Infrared Spectra, A Practical Approach. In: Encyclopedia of Analytical Chemistry. 2000. Klöcking R, Sprössig M. Antiviral properties of humic acids. Experientia. 1972;28. Piccolo A. The supramolecular structure of humic substances. Soil Sci. 2001;166. Piccolo A, Zaccheo P, Genevini PG. Chemical characterization of humic substances extracted from organic-waste-amended soils. Bioresour Technol. 1992;40. Varma S, Jaber M, Aboufanas S, Thomas S, Al Hujailan R, Al Qaoud S. Evaluating tensile strengths of absorbable suture materials in herbal solutions: An in vitro study. J Int Oral Health. 2019;11. Karabulut R, Sonmez K, Turkyilmaz Z, Bagbanci B, Basaklar AC, Kale N. An In Vitro and In Vivo Evaluation of Tensile Strength and Durability of Seven Suture Materials in Various pH and Different Conditions: An Experimental Study in Rats. Indian J Surg. 2010;72. Chanu NR, Gogoi P, Barbhuiya PA, Dutta PP, Pathak MP, Sen S. Natural Flavonoids as Potential Therapeutics in the Management of Diabetic Wound: A Review. Curr Top Med Chem. 2023;23. Verrillo M, Salzano M, Savy D, Di Meo V, Valentini M, Cozzolino V, et al. Antibacterial and antioxidant properties of humic substances from composted agricultural biomasses. Volume 9. Chemical and Biological Technologies in Agriculture; 2022. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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17:12:28","extension":"xml","order_by":7,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":68529,"visible":true,"origin":"","legend":"","description":"","filename":"626ab389281947699e7cf3ee5b85dac31structuring.xml","url":"https://assets-eu.researchsquare.com/files/rs-7618850/v1/2b9100325a470560f861052f.xml"},{"id":96205759,"identity":"c5accb96-5803-43b9-9e18-94717f98c935","added_by":"auto","created_at":"2025-11-18 17:12:28","extension":"html","order_by":8,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":74028,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-7618850/v1/e0f772b588fd21f505f34e9d.html"},{"id":96205754,"identity":"2fdefc81-60be-4b3b-aa4d-aa9baaf92813","added_by":"auto","created_at":"2025-11-18 17:12:28","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":182860,"visible":true,"origin":"","legend":"\u003cp\u003eComparative FTIR spectra of humic acid treated and untreated silk sutures (3-0). Key absorption bands are marked for functional groups such as O–H/N–H (~3300 cm⁻¹), C–H (~2920 cm⁻¹), C=O (~1700 cm⁻¹), aromatic C=C (~1600 cm⁻¹), and C–O/C–N (~1230 cm⁻¹).\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-7618850/v1/55bcf6d1093e745829a66fe0.png"},{"id":96205757,"identity":"6656f5fe-b2b1-4de6-a4d0-bc6c93911c56","added_by":"auto","created_at":"2025-11-18 17:12:28","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":210606,"visible":true,"origin":"","legend":"\u003cp\u003eComparative FTIR spectra of humic acid treated and untreated PGLA sutures (3-0). Key absorption bands are marked for functional groups such as O–H/N–H (~3300 cm⁻¹), C–H (~2920 cm⁻¹), C=O (~1700 cm⁻¹), aromatic C=C (~1600 cm⁻¹), and C–O/C–N (~1230 cm⁻¹).\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-7618850/v1/2f72311956dcbe99c8e20a89.png"},{"id":100357790,"identity":"bb7f1238-893f-4eff-82bd-36aac60482cf","added_by":"auto","created_at":"2026-01-16 07:20:20","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":979407,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7618850/v1/b6517cce-bf69-4089-9b03-bdf79d9d755e.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Characterization of Structural and Functional Properties of Humic Acid-Impregnated Dental Surgical Sutures","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eSutures are essential medical devices widely used in surgical procedures to approximate tissues and promote healing.[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e][\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003c/ol\u003e\u003cdiv class=\"BlockQuote\"\u003e\u003cp\u003eDental sutures can be classified according to their origin, structure, and biodegradability. For example, silk is a natural, non-absorbable suture material that does not degrade in the body and usually needs to be removed manually.[\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e] In contrast, synthetic materials like polyglycolic acid (PGA) or poly(glycolide-co-lactide) (PGLA) are absorbable sutures that are gradually broken down by enzymatic or hydrolytic processes.[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e] Monofilament sutures, made of a single strand, cause less tissue trauma, while multifilament (braided) sutures offer better handling and knot security.[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e] The choice of suture depends on factors such as the location of the surgery, expected healing time, and the risk of infection.[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]\u003c/p\u003e\u003cp\u003eRecently, the incorporation of medications or essential oils into sutures has gained attention, as impregnated sutures may enhance wound healing, reduce microbial colonization, and offer additional clinical benefits such as anti-inflammatory or analgesic effects.[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e] The integration of bioactive agents into suture materials has gained attention due to the potential to reduce postoperative infections and enhance healing.[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]\u003c/p\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eHumic acid, a natural organic compound derived from the decomposition of plant material, possesses antimicrobial, antioxidant, and anti-inflammatory properties.[\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e] Humic acid is a complex mixture of high molecular weight organic molecules resulting from the microbial degradation of plant matter, primarily composed of aromatic and aliphatic structures with abundant carboxyl (-COOH), hydroxyl (-OH), and phenolic functional groups.[\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e] These functional moieties confer humic acid with strong chelating, antioxidant, and antimicrobial properties. Due to its biocompatibility, low cytotoxicity, and ability to modulate inflammatory responses, humic acid has emerged as a promising candidate for intraoral applications. Its potential to enhance wound healing, inhibit pathogenic biofilms, and promote tissue regeneration makes it particularly suitable for use in dental formulations such as mouthwashes, gels, and impregnated biomaterials like sutures.[\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]\u003cdiv class=\"BlockQuote\"\u003e\u003cp\u003eHowever, for its successful incorporation into dental biomaterials\u0026mdash;such as sutures\u0026mdash;it is crucial that its integration does not adversely alter the chemical structure or compromise the mechanical properties of the carrier material. Maintaining the structural integrity and tensile strength of the suture ensures both clinical performance and safety during the healing process.[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]\u003c/p\u003e\u003cp\u003eIn addition, verifying the presence of humic acid on the material surface and demonstrating its controlled release are critical parameters to confirm its sustained bioactivity and therapeutic effect. [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e] Analytical techniques such as FTIR spectroscopy, surface mapping, and release kinetics studies are therefore essential in validating the functional performance of humic acid-loaded biomaterials.[\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]\u003c/p\u003e\u003cp\u003eThe aim of this study was to evaluate the structural modifications and mechanical behavior of humic acid-impregnated sutures using FTIR spectroscopy and tensile elongation analysis.\u003c/p\u003e\u003c/div\u003e\u003c/p\u003e"},{"header":"2. Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e2.1. Preparation of Humic Acid-Impregnated Sutures\u003c/h2\u003e\u003cp\u003eCommercially available absorbable/non-absorbable sutures (specify type) were immersed in a solution of humic acid under controlled conditions (pH, temperature, duration). The impregnated sutures were dried and stored under sterile conditions. Humic acid (Humic scid p\u0026uuml;re 99%, Serravit\u0026reg;, T\u0026uuml;rkiye) was added to a sodium alginate solution and applied. During application, 1.87 g of sodium alginate was gradually added to 125 ml of pure water in a beaker with a magnetic stirrer operating at 1600 rpm. The sodium alginate was dissolved at 100\u0026deg;C for 100 minutes. After preparing the sodium alginate stock solution, 1 drop of humic acid was added to 10 ml of the alginate solution and stirred at 500 rpm for 15 minutes. The samples were left in this solution for 1 minute. The samples were then placed in a bath containing 100 ml water and 2.21 g CaCl₂ for 5 minutes to allow the humic acid-alginate solution to solidify on the sample surface. The impregnated sutures were dried and stored under sterile conditions.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\u003ch2\u003e2.2. FTIR Spectroscopy\u003c/h2\u003e\u003cp\u003eFourier-transform infrared (FTIR) spectroscopy was employed to evaluate the chemical structure and surface modifications of silk and PGLA sutures following humic acid treatment. Both treated and untreated samples of 3\u0026thinsp;\u0026minus;\u0026thinsp;0 and 4\u0026thinsp;\u0026minus;\u0026thinsp;0 suture sizes were analyzed to detect characteristic functional groups and assess potential interactions with humic acid. The technique was chosen for its sensitivity in identifying molecular vibrations associated with hydroxyl, carbonyl, and other key chemical bonds relevant to biofunctional coatings.\u003c/p\u003e\u003cp\u003eFTIR spectra were recorded using an attenuated total reflectance (ATR) accessory in the range of 4000\u0026ndash;500 cm⁻\u0026sup1; at a resolution of 4 cm⁻\u0026sup1;. Prior to analysis, suture samples were gently cleaned with distilled water and air-dried to remove any residual surface contaminants. Each sample was placed in direct contact with the diamond crystal, and pressure was applied uniformly to ensure optimal surface contact. Background spectra were collected before each scan to ensure accuracy. For each sample, a minimum of 32 scans were averaged to enhance signal-to-noise ratio and reproducibility.\u003c/p\u003e\u003cp\u003eThe spectra were analyzed to identify specific absorption bands corresponding to O\u0026ndash;H/N\u0026ndash;H stretching (~\u0026thinsp;3300 cm⁻\u0026sup1;), C\u0026ndash;H stretching (~\u0026thinsp;2920 cm⁻\u0026sup1;), C\u0026thinsp;=\u0026thinsp;O stretching (~\u0026thinsp;1700\u0026ndash;1750 cm⁻\u0026sup1;), and ester or ether group vibrations in the 1200\u0026ndash;1000 cm⁻\u0026sup1; region. Comparative evaluation of treated versus untreated sutures allowed for the identification of spectral shifts, peak broadening, or intensity changes suggestive of humic acid binding. All FTIR data were plotted and interpreted using appropriate software tools for spectral analysis and labeling of functional group regions.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\u003ch2\u003e2.3. Tensile Elongation Testing\u003c/h2\u003e\u003cp\u003eMechanical properties of the sutures were assessed using a universal testing machine. Parameters such as maximum tensile strength, elongation at break, and Young\u0026rsquo;s modulus were recorded. Comparisons were made between treated and untreated sutures.\u003c/p\u003e\u003cp\u003eTensile strength and elongation tests of the suture materials were performed in accordance with \u003cb\u003eEN ISO 2062\u003c/b\u003e, which specifies the standard method for determining the tensile properties of threads and yarns. All specimens were tested using a jaw separation distance of \u003cb\u003e250 mm\u003c/b\u003e and a constant crosshead speed of \u003cb\u003e250 mm/min\u003c/b\u003e. The tests were conducted under controlled environmental conditions, with a temperature maintained at \u003cb\u003e20\u0026thinsp;\u0026plusmn;\u0026thinsp;2\u0026deg;C\u003c/b\u003e and relative humidity at \u003cb\u003e65\u0026thinsp;\u0026plusmn;\u0026thinsp;4%\u003c/b\u003e, ensuring standardized assessment of mechanical properties. The maximum force (N) and percentage elongation at break were recorded for each sample.\u003c/p\u003e\u003c/div\u003e"},{"header":"3. Results","content":"\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\n \u003ch2\u003e3.1. FTIR Analysis\u003c/h2\u003e\n \u003cp\u003eFTIR analysis revealed distinct spectral differences between humic acid-treated and untreated silk sutures (3\u0026thinsp;\u0026minus;\u0026thinsp;0 and 4\u0026thinsp;\u0026minus;\u0026thinsp;0). All samples exhibited characteristic absorption bands of silk fibroin, including broad peaks around ~\u0026thinsp;3300 cm⁻\u0026sup1; (O\u0026ndash;H/N\u0026ndash;H stretching), ~\u0026thinsp;2920 cm⁻\u0026sup1; (C\u0026ndash;H stretching), ~\u0026thinsp;1700 cm⁻\u0026sup1; (C\u0026thinsp;=\u0026thinsp;O stretching), ~\u0026thinsp;1600 cm⁻\u0026sup1; (aromatic C\u0026thinsp;=\u0026thinsp;C and amide II), and the 1230\u0026ndash;1050 cm⁻\u0026sup1; region (C\u0026ndash;O/C\u0026ndash;N stretching). Compared to untreated sutures, humic acid-treated samples displayed increased peak intensity and broadening, particularly in the ~\u0026thinsp;3300 cm⁻\u0026sup1; and ~\u0026thinsp;1700 cm⁻\u0026sup1; regions, indicating successful adsorption of humic acid and the presence of additional hydroxyl and carboxyl functional groups. These spectral changes were more pronounced in the 4\u0026thinsp;\u0026minus;\u0026thinsp;0 treated sutures, suggesting a potential effect of suture diameter or surface exposure on the extent of humic acid interaction. Overall, the FTIR spectra confirmed chemical modifications attributable to humic acid treatment.\u003c/p\u003e\n \u003cp\u003eAll samples exhibited characteristic absorption peaks associated with PGLA composition, including O\u0026ndash;H/N\u0026ndash;H stretching vibrations near ~\u0026thinsp;3300 cm⁻\u0026sup1;, C\u0026ndash;H stretching around ~\u0026thinsp;2920 cm⁻\u0026sup1;, a strong carbonyl (C\u0026thinsp;=\u0026thinsp;O) peak in the ~\u0026thinsp;1750\u0026ndash;1700 cm⁻\u0026sup1; region, and prominent ester-related C\u0026ndash;O\u0026ndash;C stretching bands in the 1200\u0026ndash;1000 cm⁻\u0026sup1; range.\u003c/p\u003e\n \u003cp\u003eTreated sutures demonstrated broader and more intense absorption bands in the O\u0026ndash;H and C\u0026thinsp;=\u0026thinsp;O regions, indicating the successful surface incorporation of humic acid. The presence of additional functional groups is likely responsible for the increased transmittance changes, suggesting chemical interaction or adsorption of humic acid on the polymer matrix. In contrast, untreated sutures exhibited sharper and more well-defined peaks, representing the native polymer structure without additional surface modifications.\u003c/p\u003e\n \u003cp\u003eFurthermore, subtle spectral shifts and intensity variations between the 3\u0026thinsp;\u0026minus;\u0026thinsp;0 and 4\u0026thinsp;\u0026minus;\u0026thinsp;0 treated samples may reflect differences in suture diameter or surface exposure, which could influence the extent of humic acid binding.\u003c/p\u003e\n \u003cp\u003eOverall, these results confirm the effective functionalization of PGLA sutures with humic acid and demonstrate the utility of FTIR analysis in detecting surface chemical modifications.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\n \u003ch2\u003e3.2. Tensile Elongation Properties\u003c/h2\u003e\n \u003cp\u003eThe maximum force test provides insight into the tensile strength of surgical sutures, which is critical for withstanding intraoperative tension and maintaining wound integrity during healing. The results in Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e demonstrate how humic acid impregnation affects the load-bearing capacity of both natural (Silk) and synthetic (PGLA) sutures.\u003c/p\u003e\n \u003cp\u003eFor Silk 3\u0026thinsp;\u0026minus;\u0026thinsp;0 sutures, humic acid impregnation led to a statistically significant reduction in maximum tensile strength, from 22.6\u0026thinsp;\u0026plusmn;\u0026thinsp;2.2 N to 17.8\u0026thinsp;\u0026plusmn;\u0026thinsp;1.3 N (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). A similar but less pronounced effect was observed in Silk 4\u0026thinsp;\u0026minus;\u0026thinsp;0, with a decrease from 12.8\u0026thinsp;\u0026plusmn;\u0026thinsp;1.1 N to 10.6\u0026thinsp;\u0026plusmn;\u0026thinsp;1.9 N (p\u0026thinsp;=\u0026thinsp;0.003). These findings suggest that humic acid modifies the mechanical integrity of silk, particularly by reducing its structural resistance to tensile forces.\u003c/p\u003e\n \u003cp\u003eIn contrast, PGLA 3\u0026thinsp;\u0026minus;\u0026thinsp;0 and 4\u0026thinsp;\u0026minus;\u0026thinsp;0 sutures exhibited no statistically significant difference in tensile strength after humic acid impregnation. The maximum force values remained virtually unchanged in 3\u0026thinsp;\u0026minus;\u0026thinsp;0 PGLA (27.7\u0026thinsp;\u0026plusmn;\u0026thinsp;2.5 N untreated vs. 27.6\u0026thinsp;\u0026plusmn;\u0026thinsp;2.3 N treated, p\u0026thinsp;=\u0026thinsp;0.897) and showed a slight, non-significant increase in 4\u0026thinsp;\u0026minus;\u0026thinsp;0 PGLA (14.2\u0026thinsp;\u0026plusmn;\u0026thinsp;1.2 N vs. 14.7\u0026thinsp;\u0026plusmn;\u0026thinsp;1.6 N, p\u0026thinsp;=\u0026thinsp;0.260).\u003c/p\u003e\n \u003cdiv class=\"gridtable\"\u003e\n \u003cdiv align=\"left\" class=\"colspec\"\u003e\u003cbr\u003e\u003c/div\u003e\u003cbr\u003e\n \u003ctable id=\"Tab1\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eMaximum tensile force (N) of dental surgical sutures before and after humic acid impregnation.\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSuture Sample\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMaximum Force (N)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMin-Max\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003ep\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSilk 3\u0026thinsp;\u0026minus;\u0026thinsp;0 untreated\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e22.6\u0026thinsp;\u0026plusmn;\u0026thinsp;2.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e18.7\u0026ndash;26.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003e\u0026lt;\u0026thinsp;0,001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSilk 3\u0026thinsp;\u0026minus;\u0026thinsp;0 humic acid impregnated\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e17.8\u0026thinsp;\u0026plusmn;\u0026thinsp;1.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e16.5\u0026ndash;19.2\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSilk 4\u0026thinsp;\u0026minus;\u0026thinsp;0 untreated\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e12.8 \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\pm\\:\\)\u003c/span\u003e\u003c/span\u003e 1.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e11.5\u0026ndash;13.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003e0.003\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSilk 4\u0026thinsp;\u0026minus;\u0026thinsp;0 humic acid impregnated\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e10.6 \u0026plusmn; 1.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e7.9\u0026ndash;13.0\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePGLA 3\u0026thinsp;\u0026minus;\u0026thinsp;0 untreated\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e27.7 \u0026plusmn; 2.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e24.9\u0026ndash;30.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003e0.897\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePGLA 3\u0026thinsp;\u0026minus;\u0026thinsp;0 humic acid impregnated\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e27.6\u0026thinsp;\u0026plusmn;\u0026thinsp;2.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e24.9\u0026ndash;30.0\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePGLA 4\u0026thinsp;\u0026minus;\u0026thinsp;0 untreated\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e14.2\u0026thinsp;\u0026plusmn;\u0026thinsp;1.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e12.3\u0026ndash;16.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003e0.260\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePGLA 4\u0026thinsp;\u0026minus;\u0026thinsp;0 humic acid impregnated\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e14.7\u0026thinsp;\u0026plusmn;\u0026thinsp;1.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e12.9\u0026ndash;17.0\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003cdiv class=\"gridtable\"\u003e\n \u003cdiv align=\"char\" class=\"colspec\"\u003e\u003cstrong\u003eTable 2.\u003c/strong\u003e Elongation values (% \u0026plusmn; standard deviation) of dental surgical sutures before and after humic acid impregnation.\u003c/div\u003e\n \u003cdiv align=\"left\" class=\"colspec\"\u003e\u003cbr\u003e\u003c/div\u003e\n \u003ctable id=\"Taba\" border=\"1\"\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSuture Sample\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eElongation (% \u0026plusmn; SD)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMin-Max\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003ep\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSilk 3\u0026thinsp;\u0026minus;\u0026thinsp;0 untreated\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e16.0\u0026thinsp;\u0026plusmn;\u0026thinsp;0.78\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e14.8\u0026ndash;17.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003e\u0026lt;\u0026thinsp;0,001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSilk 3\u0026thinsp;\u0026minus;\u0026thinsp;0 humic acid impregnated\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e20.3\u0026thinsp;\u0026plusmn;\u0026thinsp;0.92\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e18.9\u0026ndash;21.6\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSilk 4\u0026thinsp;\u0026minus;\u0026thinsp;0 untreated\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e19.3\u0026thinsp;\u0026plusmn;\u0026thinsp;0.80\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e18.78\u0026ndash;21.04\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003e\u0026lt;\u0026thinsp;0,001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSilk 4\u0026thinsp;\u0026minus;\u0026thinsp;0 humic acid impregnated\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e14.8\u0026thinsp;\u0026plusmn;\u0026thinsp;1.30\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e12.37\u0026ndash;16.45\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePGLA 3\u0026thinsp;\u0026minus;\u0026thinsp;0 untreated\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e32.1\u0026thinsp;\u0026plusmn;\u0026thinsp;0.78\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e31.43\u0026ndash;33.73\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003e0.238\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePGLA 3\u0026thinsp;\u0026minus;\u0026thinsp;0 humic acid impregnated\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e28.4\u0026thinsp;\u0026plusmn;\u0026thinsp;1.66\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e25.33\u0026ndash;30.47\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePGLA 4\u0026thinsp;\u0026minus;\u0026thinsp;0 untreated\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e31.4\u0026thinsp;\u0026plusmn;\u0026thinsp;1.26\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e28.78\u0026ndash;33.07\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003e0.132\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePGLA 4\u0026thinsp;\u0026minus;\u0026thinsp;0 humic acid impregnated\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e30.8 \u0026plusmn; 0.79\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e29.08\u0026ndash;31.98\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003cp\u003eThe humic acid-impregnated sutures showed slightly increased elongation at break, indicating improved flexibility. Elongation capacity reflects a suture\u0026rsquo;s flexibility and ability to stretch under tensile stress. As shown in Table 2, humic acid impregnation significantly affected the elongation percentages in both Silk and PGLA sutures, although the direction of the effect varied by material and gauge. For Silk 3\u0026thinsp;\u0026minus;\u0026thinsp;0, elongation increased markedly from 16.0% \u0026plusmn; 0.78 to 20.3% \u0026plusmn; 0.92 (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001), suggesting that humic acid treatment enhanced flexibility. In contrast, Silk 4\u0026thinsp;\u0026minus;\u0026thinsp;0 showed a significant reduction in elongation from 19.3% \u0026plusmn; 0.80 to 14.8% \u0026plusmn; 1.30 (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001), indicating a stiffening effect at the thinner gauge. For PGLA 3\u0026thinsp;\u0026minus;\u0026thinsp;0, elongation decreased from 32.1% \u0026plusmn; 0.78 to 28.4% \u0026plusmn; 1.66, though the difference was not statistically significant (p\u0026thinsp;=\u0026thinsp;0.238). Similarly, PGLA 4\u0026thinsp;\u0026minus;\u0026thinsp;0 showed a slight, non-significant decrease from 31.4% \u0026plusmn; 1.26 to 30.8% \u0026plusmn; 0.79 (p\u0026thinsp;=\u0026thinsp;0.132).\u003c/p\u003e\n\u003c/div\u003e"},{"header":"4. Discussion","content":"\u003cp\u003eThis study investigated the physicochemical and mechanical effects of humic acid treatment on both non-absorbable silk and absorbable PGLA sutures of two different sizes (3\u0026thinsp;\u0026minus;\u0026thinsp;0 and 4\u0026thinsp;\u0026minus;\u0026thinsp;0). The FTIR findings confirmed the successful functionalization of sutures with humic acid. Mechanical testing indicated that the treated sutures maintained their structural integrity while offering potential advantages in terms of tissue compliance and reduced risk of infection.\u003c/p\u003e\u003cp\u003e\u003cb\u003eFTIR spectral analysis\u003c/b\u003e revealed notable changes in the chemical composition of humic acid-treated sutures compared to untreated controls. Characteristic bands corresponding to O\u0026ndash;H/N\u0026ndash;H stretching (~\u0026thinsp;3300 cm⁻\u0026sup1;), aliphatic C\u0026ndash;H stretching (~\u0026thinsp;2920 cm⁻\u0026sup1;), and ester-related C\u0026thinsp;=\u0026thinsp;O stretching (~\u0026thinsp;1700 cm⁻\u0026sup1;) were present in all groups, confirming the polymeric backbone of silk and PGLA. However, increased intensity and broadening of the O\u0026ndash;H and C\u0026thinsp;=\u0026thinsp;O bands in treated groups indicated successful incorporation or surface adsorption of humic acid, likely through hydrogen bonding and Van der Waals interactions.[\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e] These chemical modifications may enhance the bioactive properties of the sutures, potentially contributing to anti-inflammatory or antimicrobial effects in clinical applications.[\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]\u003c/p\u003e\u003cp\u003eInfrared spectra of the humic acids showed broad bands in the 3200\u0026ndash;3500 cm⁻\u0026sup1; range, attributed to O\u0026ndash;H and N\u0026ndash;H stretching vibrations. These bands reflect the presence of hydroxyl and amide groups, with higher intensity in sludge-derived HA, likely due to its peptide-rich composition.[\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]\u003c/p\u003e\u003cp\u003eThe mechanical testing results complemented the FTIR findings. In silk sutures, humic acid treatment resulted in a reduction in maximum tensile strength\u0026mdash;most notably in 4\u0026thinsp;\u0026minus;\u0026thinsp;0 samples (from 12.8 N to 10.6 N)\u0026mdash;suggesting that the surface modification may have affected the load-bearing fibers or altered surface tension. Interestingly, elongation (%) increased in the treated 3\u0026thinsp;\u0026minus;\u0026thinsp;0 silk group, implying enhanced flexibility. This weakening effect may be attributed to the hydrophilic nature and protein-based composition of silk fibers, which are more susceptible to structural changes upon surface modification.[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e] The humic acid impregnation likely alters the fiber-matrix interactions or introduces additional surface porosity, thereby diminishing overall tensile strength. The clinical implication is that although silk sutures are generally strong and well-handling, humic acid treatment may compromise their performance under high tension, especially in high-load surgical sites.\u003c/p\u003e\u003cp\u003eIn contrast, \u003cb\u003ePGLA sutures\u003c/b\u003e showed minimal changes in tensile strength after humic acid treatment (27.7 N to 27.6 N in 3\u0026thinsp;\u0026minus;\u0026thinsp;0), suggesting that the bioactive coating did not compromise the polymer\u0026rsquo;s structural integrity. Elongation remained high in both treated and untreated PGLA groups, particularly in 4\u0026thinsp;\u0026minus;\u0026thinsp;0 sutures, demonstrating good ductility and flexibility consistent with absorbable materials.[\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e, \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]\u003c/p\u003e\u003cp\u003eThis suggests that PGLA's synthetic polyester structure, known for its hydrolytic stability and resistance to surface alterations, maintains mechanical performance even after impregnation.[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e] [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]The interaction of humic acid with the denser, crystalline nature of PGLA may be limited to the surface without penetrating or altering the core mechanical properties.\u003c/p\u003e\u003cp\u003eCollectively, these results indicate that humic acid treatment can successfully functionalize the surface of both absorbable and non-absorbable sutures, as evidenced by FTIR spectra, while preserving acceptable mechanical performance\u0026mdash;especially in absorbable materials like PGLA. However, the extent of impact appears to be influenced by both the material type and suture diameter, with finer sutures (4\u0026thinsp;\u0026minus;\u0026thinsp;0) generally showing greater sensitivity in mechanical behavior following surface treatment. Future studies may explore the biological implications of these chemical changes, including cytocompatibility, antibacterial efficacy, and degradation behavior.\u003c/p\u003e\u003cp\u003eFTIR spectra revealed characteristic peaks corresponding to carboxylic, phenolic, and hydroxyl groups in the humic acid-treated samples. Shifts in amide bands suggested physical or chemical interactions between humic acid and the suture polymer matrix.in simulated physiological environments. [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e, \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]\u003c/p\u003e\u003cp\u003eFurthermore, the impregnated sutures demonstrated enhanced elasticity and preserved tensile strength within clinically acceptable limits. These findings suggest that humic acid-impregnated sutures may serve as a promising alternative in surgical applications with additional antimicrobial benefits.\u003c/p\u003e"},{"header":"5. Conclusion","content":"\u003cp\u003eHumic acid-impregnated sutures exhibit promising structural and mechanical characteristics, making them suitable candidates for further biomedical applications. Their antimicrobial potential, combined with acceptable mechanical performance, supports their future use in clinical settings.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003ch2\u003eUncropped Gels and Blots\u003c/h2\u003e\u003cp\u003eOur study does not involve any gel electrophoresis or blot images; therefore, no uncropped gel/blot files are applicable.\u003c/p\u003e\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003cp\u003eNot applicable.\u003c/p\u003e\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003cp\u003eNot applicable.\u003c/p\u003e\u003c/p\u003e\u003cp\u003e\u003ch2\u003eClinical trial number\u003c/h2\u003e\u003cp\u003eNot applicable.\u003c/p\u003e\u003c/p\u003e\u003ch2\u003eFunding\u003c/h2\u003e\u003cp\u003eNo specific grant from any funding agency in the public, commercial, or not-for-profit sectors was received for this research.\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eAA and HC contributed to the conceptualization and methodology and investigation. AA and MK contributed on formal analysis, data collection. All authors prepared the original manuscript. All authors on manuscript review and editing. All authors have read and approved the final manuscript.\u003c/p\u003e\u003ch2\u003eAcknowledgments\u003c/h2\u003e\u003cp\u003eThe authors would like to thank all the dental students for their participation in this study.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eThe datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eErhabor P, Ifeoma A-N, Ogbeide VN, Ebomwonyi A. Sutures and Suturing Techniques in Dental Surgery. Global Sci Indep J. 2022;2.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eChen Y, Chai M, Xuan C, Lin J, Yang H, Li C et al. Tuning the properties of surgical polymeric materials for improved soft-tissue wound closure and healing. Prog Mater Sci. 2024;143.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eFaris A, Khalid L, Hashim M, Yaghi S, Magde T, Bouresly W et al. Characteristics of Suture Materials Used in Oral Surgery: Systematic Review. Int Dent J. 2022;72.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eD\u0026rsquo;Cunha P, Pande B, Kathalagiri MS, Moharana AK, DT S, Pinto CS. Absorbable sutures: chronicles and applications. Int Surg J. 2022;9.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eERCAL P, ERTEN TAYŞİ A, TAYŞİ NM. ŞİŞMANOĞLU S. Evaluation of Tensile Strength of Sutures Used in Dentistry. Sağlık Bilimlerinde Değer. 2023;13.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eAlhulaybi ZA. Fabrication and Characterization of Poly(lactic acid)-Based Biopolymer for Surgical Sutures. ChemEngineering. 2023;7.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eTummalapalli M, Anjum S, Kumari S, Gupta B. Antimicrobial Surgical Sutures: Recent Developments and Strategies. Polym Rev. 2016;56.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eRamani S, Senthil S, Rajaram V, Kumari BN, Ravi N, Mahendra J, CLINICAL AND DIAGNOSTIC RESEARCH. Comparison of Mechanical, Antibacterial and Morphological Properties of Silk Sutures Coated with Silver Nanoparticles and Aloe Vera Herbal Extract: An In-vitro Study. JOURNAL OF; 2023. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.7860/jcdr/2023/62524.18576\u003c/span\u003e\u003cspan address=\"10.7860/jcdr/2023/62524.18576\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eShah R, Taylor L, Saeinasab M, Zhang X, Zhang W, Nair K, et al. Bioactive sutures: advances in surgical suture functionalization. In: Advanced Technologies and Polymer Materials for Surgical Sutures; 2023.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eDe Melo BAG, Motta FL, Santana MHA. Humic acids: Structural properties and multiple functionalities for novel technological developments. Mater Sci Eng C. 2016;62.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003e\u0026Ccedil;alişir M, Akpinar A, Talma\u0026ccedil; AC, Lektemur Alpan A, G\u0026ouml;ze \u0026Ouml;F. Humic Acid Enhances Wound Healing in the Rat Palate. Evidence-based Complementary and Alternative Medicine. 2018;2018.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eVaškov\u0026aacute; J, Stup\u0026aacute;k M, Vidov\u0026aacute; Ugurbaş M, Žatko D, Vaško L. Therapeutic Efficiency of Humic Acids in Intoxications. Life. 2023;13.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eVitiello G, Venezia V, Verrillo M, Nuzzo A, Houston J, Cimino S et al. Hybrid humic acid/titanium dioxide nanomaterials as highly effective antimicrobial agents against gram(\u0026ndash;) pathogens and antibiotic contaminants in wastewater. Environ Res. 2021;193.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003evon Fraunhofer JA, Storey RJ, Masterson BJ. Tensile properties of suture materials. Biomaterials. 1988;9.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMarturello DM, Mcfadden MS, Bennett RA, Ragetly GR, Horn G. Knot security and tensile strength of suture materials. Vet Surg. 2014;43.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMartinez-Balmori D, Spaccini R, Aguiar NO, Novotny EH, Olivares FL, Canellas LP. Molecular characteristics of humic acids isolated from vermicomposts and their relationship to bioactivity. J Agric Food Chem. 2014;62.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eCherniienko A, Lesyk R, Zaprutko L, Pawełczyk A. IR-EcoSpectra: Exploring sustainable ex situ and in situ FTIR applications for green chemical and pharmaceutical analysis. J Pharm Anal. 2024;14.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eStuart BH. Infrared Spectroscopy: Fundamentals and Applications. 2005.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eCoates J. Interpretation of Infrared Spectra, A Practical Approach. In: Encyclopedia of Analytical Chemistry. 2000.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eKl\u0026ouml;cking R, Spr\u0026ouml;ssig M. Antiviral properties of humic acids. Experientia. 1972;28.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003ePiccolo A. The supramolecular structure of humic substances. Soil Sci. 2001;166.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003ePiccolo A, Zaccheo P, Genevini PG. Chemical characterization of humic substances extracted from organic-waste-amended soils. Bioresour Technol. 1992;40.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eVarma S, Jaber M, Aboufanas S, Thomas S, Al Hujailan R, Al Qaoud S. Evaluating tensile strengths of absorbable suture materials in herbal solutions: An in vitro study. J Int Oral Health. 2019;11.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eKarabulut R, Sonmez K, Turkyilmaz Z, Bagbanci B, Basaklar AC, Kale N. An In Vitro and In Vivo Evaluation of Tensile Strength and Durability of Seven Suture Materials in Various pH and Different Conditions: An Experimental Study in Rats. Indian J Surg. 2010;72.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eChanu NR, Gogoi P, Barbhuiya PA, Dutta PP, Pathak MP, Sen S. Natural Flavonoids as Potential Therapeutics in the Management of Diabetic Wound: A Review. Curr Top Med Chem. 2023;23.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eVerrillo M, Salzano M, Savy D, Di Meo V, Valentini M, Cozzolino V, et al. Antibacterial and antioxidant properties of humic substances from composted agricultural biomasses. Volume 9. Chemical and Biological Technologies in Agriculture; 2022.\u003c/span\u003e\u003c/li\u003e\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":"humic acid, FTIR spectroscopy, suture, PGLA, silk, mechanical strength, surface functionalization, bioactive coating","lastPublishedDoi":"10.21203/rs.3.rs-7618850/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7618850/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eObjective:\u003c/h2\u003e\u003cp\u003eTo evaluate the physicochemical and mechanical effects of humic acid treatment on silk and poly(glycolide-co-lactide) (PGLA) sutures of different sizes (3\u0026thinsp;\u0026minus;\u0026thinsp;0 and 4\u0026thinsp;\u0026minus;\u0026thinsp;0), using Fourier-transform infrared (FTIR) spectroscopy and tensile testing.\u003c/p\u003e\u003ch2\u003eMaterials and Methods:\u003c/h2\u003e\u003cp\u003eSilk (non-absorbable) and PGLA (absorbable) sutures, both 3\u0026thinsp;\u0026minus;\u0026thinsp;0 and 4\u0026thinsp;\u0026minus;\u0026thinsp;0 in size, were subjected to humic acid surface treatment. Untreated counterparts served as controls. FTIR spectra were recorded to identify chemical modifications on the suture surfaces, focusing on functional group shifts and intensity variations. Tensile strength and elongation at break were assessed according to EN ISO 2062.\u003c/p\u003e\u003ch2\u003eResults:\u003c/h2\u003e\u003cp\u003eFTIR analysis showed enhanced O\u0026ndash;H and C\u0026thinsp;=\u0026thinsp;O peak intensities in humic acid-treated groups, suggesting successful surface functionalization. Treated silk sutures displayed reduced tensile strength in 3\u0026thinsp;\u0026minus;\u0026thinsp;0 samples (p\u0026thinsp;\u0026lt;\u0026thinsp;0,001) and 4\u0026thinsp;\u0026minus;\u0026thinsp;0 (p\u0026thinsp;=\u0026thinsp;0.003) samples. whereas PGLA samples retained similar strength post-treatment (27.7 N vs. 27.6 N). Elongation percentages generally increased in treated silk sutures, while remaining high and consistent in PGLA groups.\u003c/p\u003e\u003ch2\u003eConclusion:\u003c/h2\u003e\u003cp\u003eHumic acid treatment effectively alters the surface chemistry of both silk and PGLA sutures, as confirmed by FTIR. While the treatment slightly compromises mechanical strength in silk sutures, PGLA maintains structural integrity, indicating its suitability for functionalization with bioactive agents.\u003c/p\u003e","manuscriptTitle":"Characterization of Structural and Functional Properties of Humic Acid-Impregnated Dental Surgical Sutures","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-11-18 17:12:23","doi":"10.21203/rs.3.rs-7618850/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":"acb1e851-306a-477f-b8b2-9786a5ceae2f","owner":[],"postedDate":"November 18th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-01-09T07:24:50+00:00","versionOfRecord":[],"versionCreatedAt":"2025-11-18 17:12:23","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7618850","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7618850","identity":"rs-7618850","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}