Preparation and antibacterial activity of quaternized chitosan with iodine

•We prepared a novel iodine complex based on chitosan.•The CTS–CTA–I2 complex improved the stability of iodine.•The max mole ratio of CTS–CTA with iodine was 1:1.33.•The CTS–CTA–I2 complex showed significant antibacterial activity.

Chitosan (CTS) is a natural polymer with active groups such as –NH2 which can be functionalized to introduce new positively charged N-atoms and protonated amino group for better use. In this study, to improve the stability of iodine, a novel complex (CTS–CTA–I2) was prepared by mixing N-(2-hydroxy) propyl-3-trimethylammonium chitosan chloride (CTS–CTA) with iodine in ethanol solution. The CTS–CTA–I2 was characterized by Fourier transform infrared spectra (FTIR), Ultraviolet and visible (UV–vis) spectra and thermal gravimetric analysis (TG). Besides, the interaction of iodine with CTS–CTA was also studied. The mole ratio of CTS–CTA with iodine was measured by iodometric titration method and the max mole ratio of CTS–CTA with iodine was 1:1.33. The antimicrobial activity of CTS, CTS–CTA and CTS–CTS–I2 complexes was investigated against Escherichia coli and Staphylococcus aureus and the antibacterial property of CTS–CTA–I2 was superior to CTS–CTA.