Photo-induced synthesis of GO–ZnO heterostructures with selective cytotoxic behavior toward colon cancer cells

A novel photo-induced, additive-minimized strategy was developed for the synthesis of graphene oxide–zinc oxide (GO–ZnO) heterostructures under mild reaction conditions. Unlike conventional hydrothermal or chemically assisted approaches, the present method utilizes light-driven nucleation and growth to achieve controlled interfacial integration of nanocrystalline ZnO (∼17–24 nm) on ultrathin GO sheets without requiring complex reagents or harsh processing conditions. Structural analyses using XRD, FTIR, and HRTEM confirmed the successful formation of a well-dispersed GO–ZnO heterostructure with strong interfacial interaction between ZnO nanoparticles and oxygen-functionalized GO layers. The synthesized nanocomposite exhibited selective cytotoxic behavior toward HCT116 colon cancer cells, showing concentration-dependent reduction in cell viability with an IC₅₀ value of ∼69.68 µg mL⁻¹ , while maintaining high biocompatibility (>93% viability) toward HEK293 normal cells even at 200 µg mL⁻¹ . The enhanced selective response is attributed to the synergistic interfacial effects of the GO–ZnO heterostructure, which may promote reactive oxygen species (ROS)-related cellular stress in cancer cells. This work demonstrates a simple and energy-efficient light-assisted route for constructing GO–ZnO heterostructures with selective biological activity and highlights their potential for future biomedical applications.