Development of azithromycin–PLGA nanoparticles: Physicochemical characterization and antibacterial effect against Salmonella typhi

The objective of the present research was to formulate poly(lactide-co-glycolide) nanoparticles loaded with azithromycin with appropriate physicochemical properties and antimicrobial activity. Azithromycin-loaded poly(lactide-co-glycolide) (PLGA) nanoparticles (NPs) were prepared in three different ratios of drug to polymer by nanoprecipitation technique. Antibacterial activity of these nanoparticles was examined against gram-negative intra cellular microorganism Salmonella typhi. The antibacterial effect was investigated using serial dilution technique to achieve the minimum inhibitory concentration (MIC) of nanoparticles. The results showed that physicochemical properties were affected by drug to polymer ratio. The results showed that nanoscale size particles ranging from 212 to 252 nm were achieved. Physicochemical properties were affected by drug to polymer ratio. The highest entrapment efficiency (78.5 ± 4.2%) was obtained when the ratio of drug to polymer was 1:3. Zeta (ζ) potential of the nanoparticles was fairly negative. The DSC thermograms and X-ray diffraction patterns revealed that the drug in the nanoparticles was in amorphous state. FT-IR spectroscopy demonstrated no detectable interactions between the drug and polymer in molecular level. In vitro release study showed two phases: an initial burst for 4 h followed by a very slow release pattern during a period of 24 h. The results of antimicrobial activity test showed that the nanoparticles were more effective than pure azithromycin against S. typhi with the nanoparticles showing equal antibacterial effect at 1/8 concentration of the intact drug. In conclusion, the azithromycin nanoparticle preparations showed appropriate physicochemical and improved antimicrobial properties which can be useful for oral administration.