Phytosynthesizing gold nanoparticles: Characterization, bioactivity, and catalysis evaluation

Abstract

Worldwide health problem generally due to the lack of widespread and comprehensive early detection methods, the associated poor prognosis of patients diagnosed in later stages of the disease and its increasing incidence on a global scale. Indeed, the struggle to fight cancer is one of the greatest challenges of mankind. Centella Asiatica (CA) and Andrographis Paniculata (AP) are two medicinal plant extracts used in the environmentally friendly extracellular production of metallic gold nanoparticles. The size, shape, stability and crystallinity of the synthesized gold nanoparticles were characterised and various characterization methods were used; UV–Vis spectroscopy, Fourier Transform Infrared Spectroscopy, X-ray diffraction, Zeta potential, Selected Area Electron Diffraction, Energy Dispersive X-ray Spectroscopy, High Resolution Transmission Electron Microscopy equipped with elemental mapping in order to confirm the formation of gold nanoparticles. The TEM results showed that gold nanoparticles were mostly spherical in shape. Their effects on anti-bacterial, catalytic, photocatalytic and anticancer cell lines were examined. The MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] test was used to confirm the cytotoxic properties of both gold nanoparticles samples and the results showed that both the human lung cancer and human breast cancer cell line growth and proliferation were inhibited. Strong antibacterial activity against gram-negative bacteria and moderate antibacterial activity against gram-positive bacteria were identified. It has also been shown that gold nanoparticles have catalytic properties for reducing 4-nitrophenol to 4-aminophenol. By degrading the two dyes methyl orange and congo red in the presence of nano catalysts, the photocatalytic activity of synthesized nanoparticles has been assessed.