Cationization of Silk Nanofibrils for Antibacterial Applications and Enhanced Biomineralization

Silk nanofibrils (SNF) demonstrate substantial potential as biomedical materials and biomineralization templates as a result of their biocompatibility, biodegradability, and resemblance to ECM structural proteins. However, a typical drawback is that the domesticated silk nanofibrils lack sufficient biological functional sites such as cationic groups that are beneficial for increasing cell adhesion, inhibiting bacterial growth, and promoting mineralized deposition. In this study, we developed a cationic SNF with dual functionalities of antibacterial properties and enhanced biomineralization using natural polysaccharide chitosan (CS) and synthetic polymer polyethyleneimine (PEI). The successful cationization of SNF was demonstrated through zeta potential measurement, XPS analysis, and antibacterial performance testing. Compared with polyethyleneimine modification, the CS-modified SNF exhibited superior cytocompatibility, highlighting the advantages of functionalizing proteins with natural cationized polysaccharides. Furthermore, the CS-modified SNF significantly accelerated the biomineralization process, enabling the formation of a uniform flower-like hydroxyapatite structure within 3 days in a 1.5 times simulated body fluid. This study offers a facile strategy for the surface functionalization of natural silk nanofibrils, thereby expanding the application of silks as functional biomaterials.