The aim of the current study is to report a simple and efficient method to chemically modify chitosan in order to form S-nitroso-chitosan for antibacterial applications. Firstly, commercial chitosan (CS) was modified to form thiolated chitosan (TCS) based on an easy and environmental-friendly method. TCS was featured based on physicochemical and morphological techniques. Results have confirmed that thiol groups in TCS formed after CS's primary amino groups were replaced with secondary amino groups. Free thiol groups in TCS were nitrosated to form S-nitrosothiol moieties covalently bond to the polymer backbone (S-nitroso-CS). Kinetic measurements have shown that S-nitroso-CS was capable of generating NO in a sustained manner at levels suitable for biomedical applications. The antibacterial activities of CS, TCS and S-nitroso-CS were evaluated based on the minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and time-kill curves determined for Escherichia coli, Staphylococcus aureus and Streptococcus mutans. MIC/MBC values reached 25/25, 0.7/0.7 and 3.1/3.1 μg mL⁻¹ for CS/TCS and 3.1/3.1, 0.1/0.2, 0.1/0.2 μg mL⁻¹ for S-nitroso-CS, respectively. Decreased MIC and MBC values have indicated that S-nitroso-CS has higher antibacterial activity than CS and TCS. Time-kill curves have shown that the bacterial cell viability decreased 5-fold for E. coli and 2-fold for S. mutans in comparison to their respective controls, after 0.5 h of incubation with S-nitroso-CS. Together, CS backbone chemically modified with S-nitroso moieties have yielded a polymer capable of generating therapeutic NO concentrations with strong antibacterial effect.

本研究的目的是报告一种简单有效的方法来化学修饰壳聚糖，以形成用于抗菌应用的S-亚硝基壳聚糖。首先，基于一种简单且环保的方法，将商业壳聚糖 (CS) 改性为硫醇化壳聚糖 (TCS)。TCS 的特点是基于物理化学和形态学技术。结果证实，TCS的伯氨基被仲氨基取代后形成了TCS中的硫醇基团。TCS 中的游离硫醇基团被亚硝化以形成与聚合物骨架共价键合的S-亚硝基硫醇部分 ( S-亚硝基-CS)。动力学测量表明S-亚硝基-CS能够以适合生物医学应用的水平持续产生NO。CS、TCS 和S-亚硝基-CS的抗菌活性是根据对大肠杆菌、金黄色葡萄球菌和变形链球菌确定的最低抑菌浓度 (MIC)、最低杀菌浓度 (MBC) 和时间-杀灭曲线来评估的。MIC / MBC值达到25/25，0.7 / 0.7和3.1 / 3.1微克毫升^-1为CS / TCS和3.1 / 3.1，0.1 / 0.2,0.1 / 0.2微克毫升^-1为小号亚硝基-CS，分别。MIC 和 MBC 值降低表明S-亚硝基-CS比CS和TCS具有更高的抗菌活性。时间-杀灭曲线表明，在与S-亚硝基-CS孵育 0.5 小时后，与它们各自的对照相比，大肠杆菌的细菌细胞活力降低了 5 倍，变异链球菌降低了2 倍。总之，用S-亚硝基部分化学修饰的 CS 主链产生了一种聚合物，能够产生具有强抗菌作用的治疗性 NO 浓度。