Green synthesized Gracilaria folifera-mediated MgO-ZnO nanocomposite for photocatalytic and anticancer applications

Gracilaria folifera-mediated MgO-ZnO nanocomposite (GF-MgO-ZnO NC) was synthesized through a green approach utilizing G. folifera extract as a reducing, stabilizing, and biofunctionalizing agent. The structural, optical, photocatalytic, and anticancer properties of the synthesized nanocomposite were systematically investigated. X-ray diffraction analysis confirmed the coexistence of crystalline MgO and ZnO phases, indicating the successful formation of a mixed-oxide nanocomposite with good crystallinity. UV-Visible spectroscopy revealed broad absorption in the UV region and an optical band gap of 4.88 eV, suggesting electronic interactions between the MgO and ZnO components. The photocatalytic performance of GF-MgO-ZnO NC demonstrated effective degradation of methyl orange dye under UV irradiation, which may be associated with improved charge separation within the MgO-ZnO nanocomposite. The anticancer activity evaluated against HT29 colorectal cancer cells using the MTT assay exhibited a concentration-dependent reduction in cell viability, with an IC₅₀ value of 93.23 μg/mL. The observed cytotoxicity may be associated with the synergistic effects of the MgO-ZnO nanocomposite and residual phytochemical species derived from G. folifera; however, the underlying molecular mechanisms were not directly investigated in the present study. These findings demonstrate that the green-synthesized GF-MgO-ZnO NC exhibits moderate photocatalytic activity and concentration-dependent cytotoxicity against HT29 colorectal cancer cells, warranting further investigation for environmental remediation and biomedical applications.