SYNTHESIS, CHARACTERIZATION, AND BIOLOGICAL EVALUATION OF GOLD NANOPARTICLES AND GRAPHENE NANOFIBERS WITH AN AUNP–GNF COMPOSITE FOR ANTIBACTERIAL APPLICATION

Abstract

The increasing prevalence of multidrug-resistant bacterial infections has accelerated the development of multifunctional nanomaterials with high efficacy of antimicrobial activity and stability of physicochemical properties. This study synthesized citrate-stabilized gold nanoparticles (AuNPs) via citrate reduction, fabricated graphene nanofibers (GNFs) by electrospinning polyacrylonitrile with reduced graphene oxide (prepared via the modified Hummers' method), and developed an AuNP-GNF composite. The materials were characterized and evaluated for antibacterial activity to determine the zone of inhibition, and antioxidant capacity of the AuNPs was determined. Characterization by UV - spectroscopy, zeta potential analysis, high-resolution transmission electron microscopy (HR-TEM), Fourier transform infrared spectroscopy, and field emission scanning electron microscopy (FESEM) confirmed successful synthesis of the nanomaterials. From the surface plasmon resonance band, AuNPs showed the characteristic band at 540 nm, the zeta potential was −28.0 ± 6.67 mV, and the conductivity was 0.531 mS/cm, which means that the AuNPs were well dispersed in the solution. HR-TEM showed the presence of AuNPs with a mostly spherical shape and good dispersion while FESEM showed continuous bead free GNFs with uniform shape. FTIR substantiated citrate stabilization of AuNPs and embedding of rGO in the nanofibrous matrix. The antibacterial activity of AuNPs was concentration dependent against B. subtilis, P. aeruginosa, E. coli and S. aureus, but the activity of GNFs was very low throughout the concentrations. The AuNP-GNF composite retained effective antibacterial activity against all tested bacteria. Additionally, AuNPs exhibited 53 ± 0.7% DPPH free radical scavenging activity at 100 μg/mL. These results show the potential of the AuNP-GNF composite for antimicrobial coatings, wound dressings, and other infection-control applications.