Enhanced Antibacterial Performance of Chitosan via Quaternary Ammonium Modification

Chitosan (CS) exhibits pH- and concentration-dependent antimicrobial activity, underscoring the need to develop CS-based materials with more stable and robust antibacterial performance. In this work, dimethyloctadecyl-(3-trimethoxysilylpropyl) ammonium (TSA) was chemically grafted onto the hydroxyl and amino groups of CS to synthesize TSA-CS derivatives. Two forms of microspheres—designated as GA-TSA-CS-12 and STPP-TSA-CS-12—were subsequently fabricated via emulsion cross-linking and ionic cross-linking methods, respectively. The resulting TSA-CS materials were thoroughly characterized by FT-IR, TGA, GPC, SEM, and XPS, confirming successful grafting, modified thermal properties, and altered molecular weight. Antibacterial evaluation revealed that TSA-CS-12 achieved high inhibition rates of 97.7% against E. coli and 98.7% against S. aureus , while the corresponding microsphere formulations maintained up to 93% antibacterial activity. These findings demonstrate that TSA-functionalized chitosan materials exhibit enhanced and more stable antibacterial performance, showing promising potential for biomedical applications.