Biosynthesis of nanoparticles (NPs) is an eco-friendly, safe and cost-effective approach, specifically when bacteria are used to produce NPs. In addition, loading of NPs on minerals such as zeolite affects their diffusion in various solutions. Gastric cancer ranks as 5th for incidence and 4th for mortality among all cancer types globally. To introduce novel NPs with toxic effects on gastric cancer cells, we synthesized bismuth oxide (Bi2O3) NPs, alone and loaded on zeolite (Bi2O3-Z) using a bacterium Vibrio sp. VLC, and evaluated their cytotoxicity on MKN-45 cells. In this regard, Bi2O3 NPs (in two forms of heated and non-heated) and Bi2O3-Z nanocomposites (NCs, with 3.35 and 15.56 wt%) were synthesized, while bismuth salt and zeolite were considered as controls. For treatment of cells, 25, 50 and 100 µg/ml of all agents were freshly prepared and after 24 h, alamar Blue assay was carried out to determine cell viability. Results of this study revealed that heated and non-heated Bi2O3 NPs induced their cytotoxic effects in a dose-dependent manner. In addition, toxicity of Bi2O3-Z NCs (3.35 wt%) was more than Bi2O3-Z NCs (15.56 wt%), bismuth salt and zeolite. In conclusion, obtained findings indicated that toxicity of bismuth salt increased when formed as NPs and NCs. Nevertheless, more research is necessary to determine the mechanism of observed actions.

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