Background and Aim: In the medical field of science, bismuth and its related compounds, such as bismuth oxide nanoparticles (Bi2O3 NPs), are frequently used for drug delivery, cancer therapy, bio imaging, and combating pathogenic microorganisms. A lot of attention has recently been paid to the green synthesis of non-toxic and environmentally friendly nanoparticles because the majority of chemical compounds used in the synthesis of nanoparticles are hazardous to human health and the environment. As a stabilizing and capping agent for NPs during the biosynthesis process, cell extracts of organisms that contain bio-reductive compounds replace chemical reducing agents. Methods: In this study, cyanobacterial cell extract from Spirulina platensis was used to create bismuth oxide nanoparticles (Bi2O3 NPs) utilizing green synthesis. X-ray diffraction (XRD), energy dispersive X-ray (EDX) analysis, Fourier-transform infrared (FT-IR) spectroscopy, scanning, and transmission electron microscopy are used to investigate the physico-chemical properties of the Bi2O3 NPs (SEM). Real-time polymerase chain reaction was used to measure the influence of the Bi2O3 NPs on the expression of the BAX and BCL2 genes in MCF-7 and MCF-10a cell lines in order to assess the apoptotic capabilities of the biosynthesized nanoparticles. Results: The form, size, and shape of Bi2O3 NPs allow them to enter cancer cells and have an impact on their fundamental functions. The ratio of BAX/BCL2 expression in the MCF-7 cell line was noticeably larger than it was in the Bi2O3 NP-treated MCF-10a cell line. Conclusion: The findings showed that green produced Bi2O3 NPs stimulated apoptosis in breast cancer cell lines through an increase in the expression of apoptosis regulator genes.
