Synthesis, structure, and application of new benzyl-functionalized chitosan derivatives and their tripolyphosphate cross-linked nanoparticles as antimicrobial agents

Five N-benzyl chitosan (NBCh) derivatives were synthesized through a two-step process. In the first step, chitosan (Ch) underwent a Schiff base reaction with various aromatic aldehydes to produce corresponding imines. Subsequently, these Schiff bases were subjected to reductive amination using sodium borohydride, yielding the desired amine products as NBChs. Sodium tripolyphosphate was then ionotropically gelled with Ch and NBChs to form Ch nanoparticles (ChNPs) and N-benzyl chitosan nanoparticles (NBChNPs), respectively. The NBCh derivatives were characterized using 1H-NMR and FT-IR spectroscopy, while ChNPs and NBChNPs were analyzed by scanning electron microscopy (SEM), particle size analysis, determination of polydispersity index (PDI) and zeta potential, and FT-IR spectroscopy. The products were tested in vitro for antimicrobial activity against Escherichia coli, Staphylococcus aureus, Aspergillus flavus, and Candida albicans. The results exhibited that the nanoparticles were the most active products compared to unmodified Ch and NBChs. This research has led to the development of novel Ch derivatives demonstrating enhanced antimicrobial activity compared to unmodified Ch molecule. These novel nanomaterials show strong potential for applications in biomedical anti-infective coatings, wound healing, food preservation, and agriculture, offering a sustainable strategy to combat microbial pathogens.