Photo-irradiated Titanium Dioxide Catalyzes Site Specific DNA Damage via Generation of Hydrogen Peroxide

Abstract

Titanium dioxide (TiO2) is a potential photosensitizer for photodynamic therapy. In this study, the mechanism of DNA damage catalyzed by photo-irradiated TiO2 was examined using [32P]-5'-end-labeled DNA fragments obtained from human genes. Photo-irradiated TiO2 (anatase and rutile) caused DNA cleavage frequently at the guanine residue in the presence of Cu(II) after E. coli formamidopyrimidine-DNA glycosylase treatment, and the thymine residue was also cleaved after piperidine treatment. Catalase, SOD and bathocuproine, a chelator of Cu(I), inhibited the DNA damage, suggesting the involvement of hydrogen peroxide, superoxide and Cu(I). The photocatalytic generation of Cu(I) from Cu(II) was decreased by the addition of SOD. These findings suggest that the inhibitory effect of SOD on DNA damage is due to the inhibition of the reduction of Cu(II) by superoxide. We also measured the formation of 8-oxo-7,8-dihydro-2'-deoxyguanosine, an indicator of oxidative DNA damage, and showed that anatase is more active than rutile. On the other hand, high concentration of anatase caused DNA damage in the absence of Cu(II). Typical free hydroxyl radical scavengers, such as ethanol, mannnitol, sodium formate and DMSO, inhibited the copper-independent DNA photodamage by anatase. In conclusion, photo-irradiated TiO2 particles catalyze the copper-mediated site-specific DNA damage via the formation of hydrogen peroxide rather than that of a free hydroxyl radical. This DNA-damaging mechanism may participate in the phototoxicity of TiO2.

Hydrogen peroxide induced repression of icaADBC transcription and biofilm development in Staphylococcus epidermidis

“…In practice, surfaces coated with the photocatalyst titanium dioxide (TiO 2 ), which can be activated by UV light to release DNA damaging oxygen radicals 24 including hydrogen peroxide, 25 have also been shown to limit bacterial biofilm development. Similarly, glass surfaces treated with photocatalytically active TiO 2 also resist bacterial adhesion in the presence of UV light.…”

Systematic Approach to In-Depth Understanding of Photoelectrocatalytic Bacterial Inactivation Mechanisms by Tracking the Decomposed Building Blocks

“…However, most of the studies regarding the PC inactivation mechanism mainly focused on the specification of the roles of extracellular ROSs. Studies investigating the bactericidal effect of intracellular ROSs are very limited, although intracellular ROSs are believed to be responsible for the oxidative damage of enzymes 14 and DNA, 15 and potentially play very important roles in cell damage during PC inactivation of microorganisms.…”

“…17 In the work of Lu et al, quantum dots of ∼5 nm in diameter were observed to be able to penetrate E. coli cells exposed to TiO 2 with 20 min illumination, suggesting the destruction of the cell envelope (i.e., cell wall and cell membrane) and the leakage of intracellular macromolecules. 18 The leaked proteins and nucleic acids from bacterial cells are believed to be oxidatively damaged or segmented and further attacked by extracellular-and intracellular-produced ROSs, 14,15 leading to degradation and complete mineralization. However, identifying the details of cell leakage or specific damage to biomolecules, such as proteins and nucleic acids, was rarely attempted in PC inactivation systems.…”

Antibacterial Evaluation of Nerium Oleander Extract Enhanced by Titanium Oxide Nanoparticles

“…Also, free TiO2 particles can attack intracellular components directly if it is enhanced with UV irradiation. This may lead to physical and chemical damages of DNA and RNA, causing the conversion of the pyrimidine and purine bases to carbon dioxide, ammonia and nitrate ions [23,24]. Although there are at least three hypotheses of the antimicrobial effect of TiO2 photocatalytic reaction, that mechanism is still to be proved.…”