Integration of lysozyme into chitosan nanoparticles for improving antibacterial activity

• Lysozyme was integrated into CS-NPs via ionotropic gelation technology by the interaction between NH and OH groups.
• CS-Lys-NPs showed enhanced antibacterial activity.
• The antibacterial action was probably due to the ability of nanoparticles to penetrate the cell membrane or influence metabolism enzyme activities and interfere with bacterial metabolism.

Lysozyme was integrated into chitosan nanoparticles (CS-NPs) to improve the antibacterial activity. CS-NPs and chitosan-lysozyme nanoparticles (CS-Lys-NPs) were prepared according to the ionic gelation technique and then characterized by average size, zeta potential, polydispersity index (PDI), atomic force microscopy (AFM), fourier transform infrared (FT-IR), small-angle X-ray scattering (SAXS), circular dichroism (CD) and UV–visible spectroscopy. Antibacterial properties were investigated by transmission electron microscopy (TEM) based on observation of the inhibition zone and measurement of the minimum inhibitory concentration (MIC) and minimum bacterial concentration (MBC) of CS-NPs and CS-Lys-NPs against E. coli and B. subtilis. The CS-NPs had particle sizes of 476.2–548.1 nm, while an increase to ∼488.8 to 613.5 nm was observed upon loading with lysozyme. The results suggested that the integration of lysozyme into CS-NPs enhanced the antibacterial activity against E. coli and B. subtilis, which may show great potential for use in the food industry and other applications in the form of direct addition or incorporation into packaging.