Nanostructural Characteristics of TiO2/ZnO Nanocomposites and Their Cytotoxicity at Ultralow Concentrations

While TiO₂ and ZnO nanomaterials have shown promising cytotoxic activities in cancer treatment studies, they did not achieve the same results as for low concentrations. Here, TiO₂/ZnO nanocomposites are synthesized using a sol-gel method, and characterized in terms of crystal structure, morphology, composition, and chemical state by various techniques. The resulting nanocomposites with different TiO₂/ZnO molar ratios (90:10 and 50:50) are examined for their cytotoxic effects on colon cancer HT29 cell lines using MTT assay and flow cytometry analysis, taking into consideration the tumor selectivity, potency selectivity expression, apoptosis, necrosis, and viability of the cells. The results obtained show that the TiO₂/ZnO (50:50) nanocomposite with fine crystallite size and clustered morphology is able to significantly reduce the percentage of viable cells (28.79 ± 2%) compared to the control sample (99.4 ± 5.4%) at ultralow concentrations (≤ 10 µg/ml). Meanwhile, the late apoptosis, early apoptosis, and necrosis values of the cells are found to be 12.86 ± 1.1%, 58.25 ± 0.3%, and 0.10 ± 0.05%, respectively. Accordingly, the TiO₂/ZnO nanocomposite with high cytotoxicity can be used as an appropriate candidate for medical applications in order to effectively eliminate the colorectal cancer cells.