Modulation of size, shape and surface charge of chitosan nanoparticles with reference to antimicrobial activity

Chitosan is extensively used in medicine and medical textiles for drug delivery and other applications because of its biocompatibility, biodegradability and inherent antimicrobial properties. In this study, we demonstrated a manipulating route with suitable process conditions to synthesize chitosan nanoparticles which are expected to have the best antibacterial activity for medical application. Ionotropic cross-linking using sodium tripolyphosphate (TPP) was the chosen route for synthesis of chitosan nanoparticles. It was interesting to observe that pH of the chitosan and TPP solution has a significant role in controlling the nanoparticle shape and size and thus can be fine tuned to achieve optimum antimicrobial activity. Solution pH of both chitosan and TPP was demonstrated to be the most critical factor in controlling particle size, surface charge and even shape as revealed by the SEM and TEM micrograph. It was also found that variation in size, shape and surface charge of chitosan nanoparticles resulted in significant variation in their antibacterial activity. The study demonstrated that best antimicrobial activity against bacteria S. aureus was achieved when the chitosan nanoparticles were synthesized at chitosan solution pH fixed at 6.0 and the TPP solution pH at 8.9. These observations can be used to fine tune the synthesis of chitosan nanoparticles for their application as an effective antimicrobial agent in polymers and textiles for their noble use in medical field