Urtica dioica L. extracts as a green catalyst for the biosynthesis of zinc oxide nanoparticles: characterization and cytotoxic effects on fibroblast and MCF-7 cell lines

Green synthesis using biological agents has been an effective approach for the preparation of various forms of nanoparticles. In this study, according to a green protocol, ethanolic and aqueous extracts of Urtica dioica L. have been utilized for the synthesis of zinc oxide nanoparticles (ZnO NPs). To evaluate the physical characteristics of the ZnO NPs, common techniques such as X-ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive X-ray Spectroscopy (EDS), Fourier Transform Infrared Spectroscopy (FTIR), Photoluminescence (PL) and UV-visible spectroscopy have been employed. Analysis of the XRD patterns confirmed the hexagonal wurtzite structure and the crystallite size was calculated using the Debye-Scherrer formula to be 19 to 28 nm. Also, the crystallite shape and size of the ZnO NPs were determined using FESEM. The FTIR results confirmed the presence of various functional groups in the NP structure. Some biological assays including in vitro cytotoxicity, hemolytic, and antibacterial activities were performed to evaluate the biological characteristics of the ZnO NPs. The cytotoxic effects of the NPs were determined after exposure to different concentrations (5-200 mg mL(-1)) at 24, 48 and 72 h. Light microscopic examination was performed and the cell viability was measured using an MTT assay. The results demonstrated that ZnO NPs prepared using ethanolic extracts had lower toxicity than those prepared using aqueous extracts in fibroblast and MCF-7 cell lines. The NPs showed good blood biocompatibility and also reliable antibacterial activities against both Gram-positive and Gram-negative bacteria.