Green and chemical synthesis of CuO nanoparticles: A comparative study for several in vitro bioactivities and in vivo toxicity in zebrafish embryos

CuO NPs is being applied for various applications including catalyst, electronics, cosmetics, and biomedicines due to its exceptional physicochemical properties. Physical and chemical routes for CuO NPs synthesis raised the concern of environmental hazard due to use of high energy, high temperature, and toxic chemicals. Conversely, green procedure is considered as an inexpensive and eco-friendly approach. To compare in vitro bioactivities and in vivo toxicity, CuO NPs was synthesized by two different methods; green and chemical routes. Leaf extract of a medicinal plant (Salacia reticulate) was used as a reducing and capping agent for green synthesis of CuO NPs. Sodium hydroxide was applied for chemical route of CuO NPs preparation. The in vivo toxicity of both CuO NPs (green and chemical) was examined in zebrafish (Dania rerio) embryos. Several in vitro biological activities e.g. antibacterial, cytotoxicity (in human cells), antidiabetic, and anti-inflammatory activities of both CuO NPs (green and chemical) was also assessed. Prepared CuO NPs (green and chemical) was characterized by SEM-EDX, FTIR, XRD, and UV–Vis spectroscopy. Several biomarkers such as hatching rate, malformation, and mortality rate of zebrafish embryos showed that green prepared CuO NPs exerted much lesser toxicity as compared to chemically synthesized CuO NPs. Antibacterial activity of green CuO NPs against Gram-negative (Escherichia coli, Staphylococcus aureus, and Enterobacter) and Gram-positive (Bacillus subtilis and Pseudomonas aeruginosa) bacteria was higher than chemical CuO NPs. Cytotoxicity results showed that human breast cancer cells (MCF-7) were more sensitive to green CuO NPs than chemical CuO NPs. Furthermore, antidiabetic and anti-inflammatory activities of green CuO NPs was greater than those of chemically prepared CuO NPs. This work revealed that in vitro bioactivities of green synthesized CuO NPs was better than chemically synthesized CuO NPs. Green CuO NPs also displayed higher biocompatibility towards zebrafish than chemical CuO NPs. This work highlights the importance eco-friendly green synthesis of CuO NPs for biomedical applications.