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A simple method of synthesis of a stable bimetallic copper-silver nano-particle (CuAg-NP) was developed by successive reduction of Cu(NO) and AgNO, using hydrazine hydrate as the reducing agent and gelatin and poly-vinyl pyrrolidone (PVP) as the capping agents. The round-shaped particles were of a core-shell structure with a core of Cu atoms surrounded by a shell of Ag atoms. The size and the mol. wt. of the NPs were (100 ± 10) nm and (820 ± 157) Kd, respectively; the particles were crystalline in nature and 90% of the precursors Cu(NO) and AgNO were converted to the NPs. The particles were more toxic to cancer cells than normal cells; the dose of the NPs (4-5 μg ml), that killed about 75% of the different human cancer cell lines viz, HepG2 (liver cancer), A549 (lung cancer) and AGS (stomach cancer), killed only about 22.5% of the normal cell lines viz, WRL68 (liver) and WI38 (lung). Therefore, the NP may be developed as a potent anticancer drug in future. The more detailed study on the cytotoxicity of the CuAg-NP on the HepG2 cell line revealed that the particles caused cell cycle arrest in a G2/M phase, depolarization of mitochondrial membrane potential, translocation of phosphatidylserine residues from inner to outer leaflets of cell membrane and DNA degradation; these phenomena confirmed that the NP-induced cell death was apoptotic in nature.

This study was initiated to resolve the ambiguity of contradictory pro-oxidant (toxic) and antioxidant (protective) effects of cerium oxide nanoparticles (CeONPs) taking zebrafish as a model system. To carry out the investigation, different CeONPs having different surface charges (+ve/−ve) with similar shapes and sizes were synthesized at different pH conditions (acidic/basic) using different capping agents (lysine/citrate). Our findings show that the alteration of the capping agent or pH had a profound effect on the biological activity of CeONPs. CeONPs synthesized at alkaline pH showed almost no toxic effect on zebrafish larvae; on the contrary, CeONPs synthesized at acidic pH were found to be toxic, leading to mortality, morphological changes, and abnormal swimming behavior of the larvae and altered levels of reactive oxygen species (ROS), mitochondrial membrane potential, and DNA degradation in larval cells. Moreover, the level of toxicity further increased on coating the NPs with positively charged capping agents. Thus, the study will be very useful in designing CeONPs for killing or protecting biological cells as needed.