The new development of inorganic (IO) nanoparticle (NPs)-based nanomedicines in anticancer therapy is an active area of research. The cellular uptake of IO NPs plays a crucial role in their efficacy as anticancer agents. In this case, IO NPs cellular uptake depends on physical and chemical parameters, including size, shape, and surface modification of the nanoparticles. From the cellular uptake, one of the essential parameters for small size plays a critical role in the NPs' due to their ability to passively diffuse across the cell membrane or enter cells through endocytosis. In this study, the inorganic SnO2 (tin dioxide) and SA (sodium alginate) were made into SnO2 (SASnO2) using a simple one-pot green method. Biomedical studies have shown that SASnO2 NPs exhibit greater antibacterial, antioxidant, and anticancer properties than SnO2 NPs. The prepared SnO2 and SASnO2 NPs were tested against breast cancer cells in anticancer studies. In cellular uptake studies, the smaller size of SASnO2 NPs (19 nm) resulted in higher cellular uptake compared to SnO2 NPs (38 nm). The larger surface area of these SASnO2 NPs allows for more contact with biological membranes and internalization (cell uptake) by cancer cells, resulting in enhanced anticancer therapy when using SASnO2 NPs.