Objective: Nowadays, gold nanoparticles (GNPs) are used in targeted nano photothermal cancer therapy. Considerable interest has been dedicated to gold nanoparticles because of their characteristics which are controllable and unique. Different synthesis methods have been proposed to produce these nanoparticles, which often require elevated temperatures/pressures or toxic solvents. Therefore, green synthesis would be a substitution selection as an environmentally friendly, economically viable and simple alternative method for the gold nanoparticles synthesis.

Materials and Methods: In this study, using walnut green external shell, GNPs have been synthesized by green chemistry method. In this reaction, walnut green shell is a reducer and stabilizing factor for preparing GNPs. In this work, after extracting walnut, 2 ml of extract was added to 4 ml of Au⁺³ solution (), purple color indicates synthesis of GNPs. For NPs synthesis with an appropriate size, some factors like pH, extract volume, gold salt concentration and reaction temperature were surveyed and by using UV-Visible (UV-Vis) absorption spectroscopy, optimum conditions were selected for preparing NPs. In addition, prepared NPs have been tested by x-ray diffraction (XRD) and transmission electron microscopy (TEM) to determine structure, size and their shape. Afterward, the synthesized GNPs were determined by 3- (4, 5-dimethylthiazolyl)-2, 5-diphenyl-tetrazolium bromide (MTT) to assay their antitumor, anti-oxidant properties.

Results: The results of these measurements show the spherical and triangular GNPs with different sizes between 10-50 nm were produced. There is an important development in the antioxidant and cytotoxicity characteristics of GNPs which are green synthesized ones. Statistical analysis also found a significant difference among various GNPs concentrations on declined cell viability of Michigan Cancer Foundation-7 (MCF7) cells in 24 h in concentration-dependent fashion. The IC50 value evaluated after 24 h of GNPs against MCF7 cells caused 52% cell death at the concentration of 3 mM.

Conclusions: The above-mentioned results suggest that synthesized nanoparticles employing green nanotechnology is a suitable technique to fight against infectious diseases and cancer.