Functionalization of biosynthesized gold nanoparticle from aqueous leaf extract of Catharanthus roseus for antibacterial studies

Synthesis of nanoparticles from various systems has been reported, but among all, biosynthesis of nanoparticles from plants is considered the most suitable method. The use of plant material not only makes the process eco-friendly or less toxic, but also makes it less expensive. This study investigated the ability of Catharanthus roseus as a reducing agent for gold nanoparticle biosynthesis and the effect of the functionalized gold nanoparticle on some human pathogenic bacteria. The biosynthesized nanoparticles and formulated nanodrug were characterized using UV-Vis spectrophotometry, Zetasizer, Scanning and transmission Electron Microscopy (SEM; TEM), Energy Dispersive spectrophotometry (EDAX) and Fourier Transform Infra-red Spectroscopy. Polyethylene glycol and Lincomycin were used to functionalize the surface of the Gold nanoparticle for antimicrobial properties. The absorption peak of the biosynthesized Gold nanoparticle was found to be 545.5 nm and Zetasizer analysis showed that the average particle size was 28.5 nm with morphological structure of spherical and triangular shapes using SEM and TEM. EDAX confirmed the presence of element gold, carbon, oxygen and copper. The Fourier transform infrared (FTIR) spectroscopy showed the strong band at 3417 cm-1 of hydroxyl (O-H) functional group in alcohols and phenolic compounds. The formulated nano-drug show antibacterial effects with maximum inhibition zones of 24 mm for Streptococcus pyogenes and 14.33 mm for Staphylococcus aureus. Therefore, this study demonstrated the bioreductive capability of aqueous leaf extract of Catharanthus roseus and the antibacterial activity of formulated gold nano-drug.