TiO 2 as a Nanozyme Mimicking Photolyase to Repair DNA Damage.

Cyclobutane pyrimidine dimer (CPD) is the most abundant DNA photolesion, and it can be repaired by photolyases based on electron-transfer mechanisms. However, photolyase is absent in the human body and lacks stability for applications. Can one develop natural enzyme mimetics utilizing nanoparticles (termed nanozymes) to mimic photolyase in repairing DNA damage? Herein, we observe the successful reversal of thymine dimer T<>T to normal T base by TiO 2 under UVA irradiation. Time-resolved spectroscopy provides direct evidence that the photogenerated electron of TiO 2 transfers to T<>T, causing structural instability and initiating the repair process. T-T - would then undergo bond cleavage to form T and T - , and T - returns an electron to TiO 2 , finishing the photocatalytic cycle. For the first time, TiO 2 is discovered to exhibit photocatalytic properties similar to those of natural enzymes, pointing to its extraordinary application potential as a nanozyme to mimic photolyase in repairing DNA damage.