Green chemistry-based synthesis of gold nanoparticles using Nicotiana plumbaginifolia and their anticancer properties against cervical cancer

Although various strategies have been reported for the synthesis of gold nanoparticles (AuNPs) for possible anticancer effects, green synthesis can be considered an efficient strategy for the production of efficient NPs with minimal toxic effects. In this study, we investigate the green synthesis of gold nanoparticles (AuNPs) using an aqueous leaf extract of Nicotiana plumbaginifolia and evaluated their protein/DNA binding, hemolysis characteristics, and anticancer properties against HeLa cervical cancer cells, while normal HUVECs were used as the control sample. Different techniques were utilized to characterize the development of AuNPs. Then, the interaction properties of biosynthesized AuNPs with HeLa cancer cells and HUVECs were assessed by cellular assays. The results showed that the Au nanosphere had an average particle size of 18 nm with four distinctive X-ray diffraction (XRD) peaks at 38.00°, 44.10°, 63.75° and 77.10°. Moreover, the UV–Vis spectrum showed a maximum absorption peak at about 538 nm, corresponding to the surface Plasmon resonance (SPR) characteristics of the AuNPs. Furthermore, an observed Fourier-transform infrared spectroscopy (FTIR) peak at about 769 cm⁻¹ was attributed to the AuO stretching vibration. Dynamic light scattering (DLS) analysis also showed that the maximum size and zeta potential values for colloid AuNPs were 68.69 nm and −47.92 mV, respectively. Then, it was detected that after incubation of maximum % solution of AuNPs, 0.1, % BSA and %DNA binding values were 58.76 % and 32.15 %, respectively. It was also determined that following incubation of red blood cells (RBC) with maximum concentrations of AuNPs, 20 μM, the hemolysis value was 2.29 %. Cellular assays showed that the IC₅₀ value of AuNPs was 1.53 μM in HeLa cells, whereas this value for HUVEC normal cells was 30.55 μM. It was also shown that incubation of cells with AuNPs for 24 h led to a higher upregulation in the levels of released Cytc. C, caspase-9, and caspase-3 in HeLa cancer cells compared with HUVECs. Then, it was determined that stimulation of ROS generation and subsequent apoptosis, upregulation of Bax/Bcl-2, caspase-9, and caspase-3 mRNA, induced by AuNPs can be reversed by pretreatment of cells with NAC, a potential antioxidant. Finally, it was demonstrated that although the exposure of HeLa cells to AuNPs after 24 h caused a significant reduction in cell viability mediated by apoptosis, pre-treatment of cells with caspase-9 and caspase-3 inhibitors, significantly mitigated apoptosis induction and recovered cell viability. In conclusion, this paper might provide useful information about the medicinal purposes enabled by AuNPs.