Garlic-induced Stable Black Gold Nanostructure: Optical, Morphological, Antibacterial, Antioxidant and Cytotoxic Properties

We have successfully developed a direct, one-step phyto-synthesis of stable black gold nanostructure (AuNS) using garlic extract (GE). The presence of abundant S in GE has a high affinity for Au, forming strong Au-S bonds to induce the growth of anisotropic crystals on Au and continue to form an extensive network of nanowires resembling a dendrimer. The synthesized garlic-induced stable black AuNS was observed by a color change from brick-red to black through the addition of GE at various concentrations and confirmed by the UV–Vis spectrophotometer, particle size analyzer (PSA), transmission electron microscope (TEM), Fourier transform infrared (FTIR), and x-ray diffraction (XRD) spectrophotometer. In addition, the antibacterial, antioxidant, and cytotoxic properties of the black AuNS were studied. Black-AuNs showed no antibacterial activity on gram-negative bacteria (Escherichia coli) and two gram-positive bacteria (Staphylococcus aureus and Bacillus subtilisin) but had very high antioxidant activity (99.68% DPPH inhibition). The cytotoxic effect of black-AuNS was studied in normal cells and showed that the inhibition in both Vero and Chang cells was dose-dependent. These findings offer new opportunities to develop a “green” superstructure of black AuNS for other biomedical applications.