Preparation nanoparticle by ionic cross-linked emulsified chitosan and its antibacterial activity

Chitosan has antibacterial activity, and preparation of nanoparticles from chitosan was expected to improve its antibacterial properties. Therefore, in order to obtain nanoparticle which can be prepared in large quantities, chitosan was emulsified by different surfactants, and then cross-linked by sodium tripolyphosphate (TPP) to form antibacterial nanoparticles, which can be well dispersible via ionotropic gelation process. The chitosan of 138 kDa was selected to optimize the cross-linking condition. Among the five factors, Plackett-Burman Design (PBD) determines chitosan concentration, sodium tripolyphosphate (TPP) concentration and medium pH value as the significant factors influencing the particulate size. The optimal cross-linking condition predicted from the RSM-CCD are as follows: 2.03 mg/mL, 1.12mg/mL and 4.6 for chitosan concentration, TPP concentration and medium pH value, respectively. Under the optimum condition, the chitosan was obtained with the minimum average diameter of 173.0 +/- 5.0 nm. The antibacterial activities of chitosan nanoparticle against the microbial strains Staphylococcus aureus, Escherichia coli and Candida albicans were investigated by spread plate method. The results showed that the antimicrobial activity of nanoparticles was significant better than that of chitosan with the same molecular weight. The size of chitosan nanoparticle was negatively correlated with the antimicrobial activity in the range of 505-173 nm. The chitosan particulate size of 173.0 +/- 5.0nm at 75 mu g/mL can made the CFU% of E. coli, S. aureus and C. albicans decreased by 90.7%, 85.3% and 70.0% respectively, while the chitosan of 138 kDa without cross-linked process decreased by 26.2%. 25.3%. 9.05%. As TPP and chitosan were safely used in food, the chitosan nanoparticles as a kind of new antimicrobial agent have broad application prospect in food industry.