Center for Natural and Human Sciences, Universidade Federal do ABC, Santo André, Brazil.
Department of Microbiology, Biology Sciences Center, Londrina State University (UEL), Londrina, Brazil.
Nitric Oxide. 2021 Jan 1;106:24-34. doi: 10.1016/j.niox.2020.10.003. Epub 2020 Oct 22.
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 for CS/TCS and 3.1/3.1, 0.1/0.2, 0.1/0.2 μg mL 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.
本研究旨在报道一种简单有效的化学修饰壳聚糖的方法，以形成用于抗菌应用的 S-亚硝基壳聚糖。首先，根据一种简单且环保的方法，将商业壳聚糖（CS）修饰形成巯基化壳聚糖（TCS）。TCS 的特点基于物理化学和形态学技术。结果证实，TCS 中的巯基基团是在 CS 的伯氨基被仲氨基取代后形成的。TCS 中的游离巯基基团被硝化为与聚合物主链共价结合的 S-亚硝硫醇部分（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生成 NO。基于最小抑菌浓度（MIC）、最小杀菌浓度（MBC）和大肠杆菌、金黄色葡萄球菌和变形链球菌的时间杀伤曲线，评估了 CS、TCS 和 S-亚硝基-CS 的抗菌活性。CS/TCS 的 MIC/MBC 值分别达到 25/25、0.7/0.7 和 3.1/3.1μg mL，而 S-亚硝基-CS 的 MIC/MBC 值分别达到 3.1/3.1、0.1/0.2 和 0.1/0.2μg mL。MIC/MBC 值降低表明 S-亚硝基-CS 的抗菌活性高于 CS 和 TCS。时间杀伤曲线表明，与各自的对照相比，S-亚硝基-CS 孵育 0.5 小时后，大肠杆菌的细菌细胞活力降低了 5 倍，变形链球菌的活力降低了 2 倍。总之，用 S-亚硝基基团化学修饰的 CS 骨架产生了一种能够产生治疗性 NO 浓度并具有强抗菌作用的聚合物。
