Preparation of organic-inorganic composites with high antibacterial activity based on sepiolite, chitosan and zinc: The study of the active antibacterial sites of chitosan‑zinc oxide structure

The organic-inorganic composites with excellent antibacterial activities based on sepiolite, zinc and chitosan were successfully synthesized via different combination styles and named as chitosan‑zinc oxide/sepiolite (CTs-ZnO/Sep), zinc oxide/chitosan-sepiolite (ZnO/CTs-Sep) and chitosan/zinc oxide-sepiolite (CTs/ZnO-Sep), respectively. The antimicrobial activity, cytotoxicity and physicochemical properties were studied systematically. The results (CTs/ZnO-Sep) indicated that the prepared samples presented excellent antibacterial activities against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli), the inhibition zone was up to 62.2 and 30.1 mm, respectively, which could be attributed to the formation of chitosan‑zinc oxide (CTs-ZnO) structure. Particularly, only CTs/ZnO-Sep exhibited high antimicrobial activities against Aspergillus niger and the inhibition zone could reach to 34.9 mm. It was found that the different combination styles of CTs-ZnO and Sep support could affect the release of CTs-ZnO, the size of ZnO, and the amount of charge around ZnO, hence influence the antimicrobial activity.