Novel Self-Patented Gold Nanoparticle Synthesis, Characterization and Antibacterial Susceptibility Testing

With soaring increase in the cases of multi-drug resistant (MDR) bacteria all over the world, we are on the verge of entering post-antibiotic era if no immediate action is taken against this global crisis. As an alternative route to modify current commercial antibiotics, we made an attempt to design an array of effective antibacterial agents involving gold nanoparticles (AuNPs) conjugated to an antibiotic, like those of the aminoglycoside, cephalosporin, and carbapenem drug classes. Due to recent emergence of infections due to both Gram-positive and Gramnegative bacterial strains with advanced patterns of antimicrobial resistance bactericidal agents such as these are being view as a prime candidates for further development and augmentation. Unlike conventional methods, a unique self-patented green process was used for AuNPs synthesis wherein the antibiotic assists in both reducing and stabilizing the AuNPs resulting in antibiotic conjugated gold nanoparticles (Ab-AuNPs) which were morphologically characterized using transmission electron microscope (TEM), UV-Vis spectroscopy, scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM-EDS), and dynamic light scattering (DLS). The presence of ligand (antibiotic) onto AuNPs was confirmed using TGA analysis. Antibacterial efficiency was evaluated on Gram-positive and Gram-negative bacterial strains using turbidmetric and spread plate assay. AuNPs activity was further confirmed with propidium iodide assay. Super-thin cross-sections of bacteria treated with Ab-AuNPs observed under TEM showed bactericidal activity by causing perforations and disturbing the cellular environment leading to cell lysis and apoptosis. The minimum inhibitory concentrations (MIC) of Ab-AuNPs were significantly less when compared to pure antibiotic drugs. This finding supports the idea of synergistic activity of Ab-AuNPs