Evaluation of the antibacterial activity of poly-(d,l-lactide-co-glycolide) nanoparticles containing violacein

Since violacein—an antibiotic, antiviral, and antiparasitic compound—exhibits poor solubility in water, polymeric poly-(d,l-lactide-co-glycolide) nanoparticles containing this compound improved its solubility and biological activity. The nanoparticles were prepared by the nanoprecipitation method and characterized in terms of average diameter, zeta potential, drug loading, polymer recovery, in vitro release kinetic, and in vitro antibacterial activity. Nanoparticles with diameters between 116 and 139 nm and negative-charged outer surfaces were obtained. Drug-loading efficiency and polymer recovery were 87 and 93%, respectively. In vitro release kinetics assays showed that violacein loaded in these nanoparticles has sustained release behavior until 5 days. Both free and nanoparticles-loaded violacein exhibited in vitro antibacterial activity against Staphylococcus aureus ATCC 29213 and ATCC 25923 strains and exhibiting around two to five times lower minimum inhibitory concentration (MIC) than free violacein, respectively. The encapsulated violacein was efficient against methicilin-resistant Staphylococcus aureus (MRSA) strains. No significant activity against Escherichia coli and Salmonella enterica was found.