Chitosan-sodium alginate nanoparticle as a delivery system for ε-polylysine: Preparation, characterization and antimicrobial activity

ε-Polylysine-loaded chitosan-sodium alginate nanoparticles (ε-PL NPs) were synthesized and characterized in terms of particle size distribution, surface morphology, thermal properties and structure, respectively. Their antibacterial activity on Escherichia coli, Bacillus subtilis , Staphylococcus aureus and Micrococcus luteus were studied. The ε-PL NPs were well dispersed as spherical particles within the range of 200–500 nm. In vitro release studies showed an initial burst release of ε-PL from the nanoparticles followed by a sustained release. The minimum inhibitory concentrations (MIC) of ε-PL NPs against four test bacteria were 7.81 μg/mL ( E. coli ), 31.25 μg/mL ( B. subtilis ), 15.63 μg/mL ( S. aureus ) and 38.67 μg/mL ( M. luteus ), respectively. The bacteriostatic activity of ε-PL NPs was three times higher ( P  < 0.05) than that of free ε-PL in terms of inhibition zone diameter, suggesting that ε-PL NPs has stronger antibacterial activity. These findings may provide some basis for the application of ε-PL NPs as a promising food preservative.