Biosynthesis of gold nanoparticles using monosaccharides of Artemisia afra and their antioxidant and anticancer properties

Bongisiwe Shelembe, Nomfundo Thobeka Mahlangeni and Roshila Moodley

Abstract

Biogenic synthesis of gold nanoparticles has received much attention due to their varied medicinal application. Monosaccharides from Artemisia afra were used as reducing and capping agents for the synthesis of gold nanoparticles. The gold nanoparticles were characterised by ultraviolet-visible (UV–vis) spectroscopy, transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The shape and morphology obtained for gold nanoparticles differed with different reaction conditions. TEM images of gold nanoparticles synthesised at high pH yielded a mixture of shapes (hexagons, rods and spheres) with average size of 7.75 nm whilst those synthesised at neutral pH yielded spheres with average size of 9.08 nm. Antioxidant activity of saccharides and gold nanoparticles by DPPH, ferric reducing antioxidant power and phosphomolybdenum methods showed gold nanoparticles synthesised at a high pH to have better antioxidant activity than those synthesised at neutral pH. The anticancer activity of the saccharides and gold nanoparticles was also investigated by the 3-[4,5-dimethylthiazol-2-yl]-2, 5-diphenyltetrazolium bromide (MTT) assay against the cancerous MCF-7 (breast adenocarcinoma) and non-cancerous HEK293 (human embryonic kidney) cell lines. Gold nanoparticles exhibited excellent cytotoxic activity towards MCF-7 cells with those synthesised at neutral pH (compared to higher pH) showing greater cell viability towards HEK293. The study shows that the size and shape of gold nanoparticles are dependent on reaction conditions and consequently affects their biological activity.