SYNTHESIS AND CHARACTERIZATION OF CHITOSAN NANOPARTICLES WITH ENHANCED ANTIMICROBIAL ACTIVITY

Abstract

The present paper demonstrates how the antimicrobial properties of chitosan can be enhanced by converting it into nanoparticles of desired size and surface charge using TPP (tripolyphosphate) initiated gelation process. It has been investigated and found that ionic gelation of cationic chitosan macromolecules offers a flexible and easily controllable process for systematically and predictably manipulating the particle size and surface charge of chitosan nano-particles which is an important property for antimicrobial effect. Variations in chitosan to TPP weight ratio, pH of chitosan solution and chitosan solution concentration during nanoparticle formation were examined systematically for their effects on nanoparticle size, intensity of surface charge, so as to enable faster synthesis of chitosan nanoparticles with desired properties to have optimum antimicrobial property. The data on particle size and zeta potential was obtained by dynamic light scattering (DLS) and electrophoretic mobility measurement of the chitosan nanoparticles respectively. UV-VIS absorption of bacterial suspension was measured at 610 nm to evaluate the bacterial reduction. Solution pH of chitosan was demonstrated to be the most critical factor in controlling particle size and surface charge. At very strong acidic condition of chitosan solution, cross-linking was less resulting in lower conversion of chitosan to chitosan nanoparticles which was reaffirmed by colloidal titration of the surface groups of the chitosan nanoparticles with negatively charged polyelectrolytes poly(vinyl sulfate kalium salt). It was found that variation in size and surface charge of chitosan nanoparticles could be achieved by changing all the above mentioned process parameters and resulted in significant variation in their antimicrobial activity.