Chitosan‑iodine complexes: Preparation, characterization, and antibacterial activity

Bacterial infections have always been a major threat to public health, and the development of effective antibacterial substances from natural polymers is crucial. 2-Aminoisonicotinic acid (AN) was grafted onto chitosan by 1-ethyl-(3-dimethylaminopropyl)carbodiimide-mediated coupling reactions, and then modified chitosan‑iodine (CSAN-I) complexes were prepared by solvent-assisted grinding. The samples were characterized using ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, proton nuclear magnetic resonance spectroscopy, and X-ray diffraction, confirming that CSAN-I complexes had been successfully prepared. Thermogravimetric (TG) analysis indicated that the chemical modification of chitosan and iodine complexation reduced the thermal stability; X-ray photoelectron spectroscopy (XPS) analysis revealed that 81 % of the iodine in CSAN-I complex was in the form of triiodide ions. The iodine contents of three CSAN-I complexes (CSAN-I-1, CSAN-I-2 and CSAN-I-3) were 1.59 ± 0.22 %, 3.18 ± 0.26 %, and 5.56 ± 0.41 %, respectively. The antibacterial effects were evaluated in vitro, and the results indicated that CSAN-I complexes had strong antibacterial activities against both E. coli and S. aureus. In particular, CSAN-I-3 exhibited the best antibacterial effect. In addition, CSAN-I-3 was nontoxic to L929 cells with good cytocompatibility. Therefore, CSAN-I complexes can be considered as promising candidates for wound management in clinical applications.