Amine-Functionalized and Gold-Decorated Amine-Functionalized TiO₂ Nanoparticles Modulate Breast Cancer Cell Viability

Surface engineering is a key strategy for modulating the biological behavior of TiO₂-based nanomaterials, with potential relevance for future localized or adjuvant approaches targeting residual cancer cells. This study evaluated whether amine functionalization and subsequent gold decoration modify the effects of TiO₂ nanoparticles (TiO₂NPs) on MCF7 and MDA-MB-231 breast cancer cells. The synthesized materials preserved the anatase TiO₂ framework, while surface modification altered their physicochemical and optical properties. After 24 h of exposure, pristine TiO₂NPs produced minimal changes in cell viability, whereas NH₂-functionalized TiO₂NPs (TiO₂NPs-NH₂) and gold-decorated NH₂-functionalized TiO₂NPs (Au@TiO₂NPs-NH₂) reduced viability in a concentration-dependent and cell line-dependent manner. These effects were more evident in the MTT assay than in Trypan Blue exclusion counting, suggesting changes in metabolic activity before extensive membrane integrity loss. Overall, the findings indicate that surface modification, rather than the TiO₂ core alone, is a major determinant of the cellular response to these nanomaterials. These results provide an initial in vitro basis for further mechanistic studies evaluating surface-engineered TiO₂NPs as candidate platforms for future adjuvant breast cancer strategies.