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 CPf-AuNPs 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 anti-cancer properties, which give an insight to the development of potential drug molecules for the treatment of various solid cancers. •Aqueous unripe fruit extract of Carica papaya was used for the synthesis of AuNPs.•Inherent phytochemicals in the extract serves as bio-reductant and capping agents.•Spherically-shaped AuNPs were produced.•CPf-AuNPs were cytotoxic against HT-29 and MDA-MB 231 cells, and non-cytotoxic to normal human fibroblast cells (KMST-6).•The synthesized CPf-AuNPs were more cytotoxic than the CPf extract.