Synthesis of gold nanoparticles using extract of Carica papaya fruit: Evaluation of its antioxidant properties and effect on colorectal and breast cancer cells

Green synthesis of gold nanoparticles (AuNPs) is a fast-growing and eco-friendly approach in the field of biomedical research. The present study reports the synthesis of AuNPs using unripe Carica papaya fruit (CPf) extract and its possible antioxidant and anti-cancer activities. Parameters such as plant extract concentration, reaction pH, temperature, size and morphology of the AuNPs were examined using UV-Vis absorption spectroscopy, dynamic light scattering (DLS) and high resolution transmission electron microscope (HRTEM). The in vitro antioxidant activities were estimated using total antioxidant capacity assay and 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay. The anti-proliferative activity of CPf and CPf-AuNPs were assessed against different cancer cell lines using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) reduction assay. The CPf-AuNPs showed a characteristic absorption peak at 529 nm, while the HRTEM analysis revealed spherically-shaped AuNPs with an average size of 12 +/- 2.31 nm. The antioxidant activities of CPf-AuNPs were in a concentration dependent manner. The CPfAuNPs showed cytotoxic effects against different cancer cells (HT-29 and MDA-MB-231) and non-cytotoxic to normal human fibroblast cells (KMST-6), at various concentrations. It can be concluded based on the results of this study that CPf-AuNPs demonstrated antioxidant and anticancer properties, which give an insight to the development of potential drug molecules for the treatment of various solid cancers.