Gold nanoparticles synthesised by flavonoid tricetin as a potential antibacterial nanomedicine to treat respiratory infections causing opportunistic bacterial pathogens

In this study, flavonoid tricetin was used as a reducing and capping agent for the synthesis of gold nanoparticles (AuNPs). Further, the antibacterial efficacy of the synthesised AuNPs was evaluated against the opportunistic bacterial pathogens that cause respiratory infections. The optimum levels for the synthesis of AuNPs were found to be pH 8, temperature 30 degrees C, tricetin 125 mu M and chloroauric acid 250 mu M. The tricetin synthesised AuNPs exhibited in spherical shape with an average size of 12 nm. FT-IR results confirmed that the hydroxyl (OH) and carbonyl (C=O) groups of tricetin were mainly participated in the synthesis of AuNPs. The opportunistic bacterial pathogens isolated from immunocompromised patients suffering with different respiratory infections were identified as Staphylococcus aureus, Enterobacter xiangfangensis, Bacillus licheniformis, Escherichia fergusonii, Acinetobacter pittii, Pseudomonas aeruginosa, Aeromonas enteropelogenes and Proteus mirabilis. The antibacterial studies confirmed the broad-spectrum antibacterial activity of AuNPs against the tested Gram-positive and Gram-negative bacteria. The synthesised AuNPs showed high biocompatibility on primary normal human dermal fibroblast (NHDF-c) cells up to 50 mu M mL(-1). Best of our knowledge, this is the first report on the synthesis of AuNPs using tricetin, which may be a potential antibacterial nanomedicine to treat bacterial infections.