Synergetic effect of vancomycin loaded silver nanoparticles for enhanced antibacterial activity

In recent years, there is significant growth in the bacterial resistance to various classic antibiotics. This has opened and enhanced the field of metal nanoparticles and antibiotic-metal nanoparticle complex. This research was designed to load a glycopeptide antibiotic named vancomycin on citrate-capped silver nanoparticles to enhance its antibacterial activity against both Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria. Colloidal solution of silver nanoparticles (AgNPs) was prepared by chemical reduction method using silver nitrate (AgNO₃) as a precursor in the presence of ionic surfactant trisodium-citrate which acts as a both capping and reducing agent. Synthesized nanoparticles were functionalized with vancomycin to form nano-drug complex (Van@AgNPs). Various analytical techniques such as UV-vis absorption spectra, FTIR, DLS, TEM and XRD were carried out to study the loading and interaction of drug with silver nanoparticles. The observed shift in SPR peak of UV-vis and various reflections of XRD spectra is attributed towards the loading of vancomycin on silver nanoparticle surface. FTIR studies shows the hydrogen bonding between vancomycin and silver nanoparticles through NH (amine) group of vancomycin and oxygen of anionic citrate. The increase in average particle size and particle size distribution of vancomycin-loaded nanoparticles in comparison to bare NPs also hints the drug loading. Agar well diffusion method was used to study the synergetic antibacterial activity of vancomycin-loaded silver nanoparticles against both test strains. The well diffusion test showed the notable enhancement in antibacterial activity against both class of bacteria. This enhancement has been observed to be synergetic rather than the additive.