Nanochitin surface charge modulates nisin composite self-assembly: A multiscale simulation-experimental exploration.

Nisin, a GRAS-approved antimicrobial peptide, suffers from limited aqueous solubility hindering practical applications. This study engineered two modified chitin nanocarriers-surface-deacetylated chitin nanofibers (S-ChNF) and oxidized chitin nanowhiskers (O-ChNW)-to improve nisin delivery. At pH 4 and a mass ratio of 1:2, both types of nanochitin achieved their highest encapsulation efficiency (EE) and loading capacity (LC): S-ChNF (EE 92.23 %, LC 30.74 %) and O-ChNW (EE 79.62 %, LC 26.53 %). Spectroscopic analyses confirmed nisin binding via hydrogen bonding and electrostatic interactions. Molecular dynamics revealed distinct mechanisms: nisin@S-ChNF primarily utilized electrostatic forces, while nisin@O-ChNW favored hydrogen bonding and van der Waals interactions, influenced by surface charge and peptide conformation. Both composites exhibited potent antimicrobial activity, reducing E. coli survival to 2.28 % (S-ChNF) and 10.85 % (O-ChNW), and S. aureus to 0.66 % and 7.81 %, respectively, after 24 h. Cytotoxicity assays confirmed biocompatibility at 300 μg/mL. This work establishes nanochitin-nisin composites as non-toxic, high-performance antimicrobial systems, advancing structure-function insights for food preservation and biomedical applications.