Formulation, Optimization and In-vitro Evaluation of Chitosan-lipid nanoparticles for Antibacterial activity against Salmonella typhimurium

Salmonella infections are difficult to treat due to the poor permeability of antibiotics into intracellular compartments and the cell walls of microorganisms with less selectivity, which results in the development of drug resistance. Chitosan is a biocompatible, naturally occurring polymer with shown antibacterial activity against a wide range of pathogenic microorganisms. In the present work, chitosan-based polymer lipid nanoparticles (PLNs) were designed to enhance the antibacterial activity against Salmonella typhimurium. PLNs were optimized by 32 full factorial design with two independent variables viz., polymer-lipid ratio (X1) ranging from 0.8 to 1.2 and surfactants (X2) Tween80:Poloxamer188 (2:1) with a concentration of 1% to 2%. Formulations were prepared by melt emulsification with a homogenization process. The influence of independent variables was checked on particle size (Y1), Polydispersity Index (Y2) and Zeta potential (Y3). The optimized batch had particle size of 234.3±4.2nm, a PDI of 0.291±0.01, and a Zeta potential of 28.9±3.4mV. FTIR analysis reveals the polymer's compatibility with lipid and additives. Analysis of DSC and XRD confirmed the existence of amorphous PLNs. The FESEM findings suggest that PLNs have a nearly spherical shape with a smooth surface morphology. Furthermore, the formulation was tested for in-vitro antibacterial activity against Salmonella typhimurium. From the results of an antibacterial study, it was found that the zone of inhibition, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of PLNs were 24mm, 15.12µg/ml, and 31.25µg/ml, respectively, which was better than the results of pure chitosan (18mm, 62.5µg/ml, and 125µg/ml).