Rapid detection of DNA damage could serve as a basis for genotoxicity studies of new bio-nanoconjugations. A novel TiO2 bio-nanoconjugation, consisting of mesoporous TiO2 microbeads, dopamine (DA) and ss-DNA, was constructed on fluorine-doped tin oxide-coated glass (FTO) and used for the detection of DNA damage in the photocatalytic reaction of TiO2 under visible light. Stable mesoporous TiO2 microbead films were coated on FTO by the doctor-blade method; dopamine with oxygen containing ligands, was tightly coupled to the titanium surface prepared under phase coordination. Specific single-strands of DNA were electronically linked to TiO2 by using a dopamine bridge. DNA damage, caused by reactive oxygen species (ROS) that were photogenerated through the photocatalytic reaction, was detected with square wave voltammetry (SWV) by recording the catalytic oxidation current of [Ru(NH3)6]3+, an intercalated electroactive probe. The ability of antioxidant to protect DNA against damage in the photocatalytic reaction was also tested. Keywords: DNA damage, TiO2 microbeads, Reactive oxygen species, Electrochemical detection