Oxidative damage to nucleic acids photosensitized by titanium dioxide

Area of Science:

• Photobiology
• Materials Science
• Biochemistry

Background:

• Titanium dioxide (TiO2) exhibits photobiological activity with potential applications in wastewater sterilization and cancer phototherapy.
• Understanding the mechanism of TiO2 photocatalysis is crucial for optimizing its applications and ensuring safety.

Purpose of the Study:

• To elucidate the mechanism of photocatalysis by TiO2 in biological systems.
• To investigate the photooxidative damage induced by TiO2 in cellular components like DNA and RNA.
• To assess the photocytotoxicity of TiO2 in human skin fibroblasts.

Main Methods:

• Electron spin resonance (ESR) spectroscopy was used to detect hydroxyl radical formation.
• UV-A irradiation of DNA and RNA in the presence of TiO2 to assess base modification.
• Exposure of human skin fibroblasts to TiO2 and UV-A radiation, followed by analysis of cellular damage.

Main Results:

• UV irradiation of TiO2 in water generated hydroxyl radicals, confirmed by ESR.
• UVA irradiation of DNA with TiO2 led to guanine base hydroxylation, dependent on UVA fluence and TiO2 concentration.
• TiO2-treated fibroblasts exposed to UVA showed dose-dependent photocytotoxicity and significant RNA photooxidation (guanine hydroxylation), but no detectable DNA damage.

Conclusions:

• Nucleic acids, particularly RNA, are susceptible to photooxidative damage sensitized by TiO2.
• TiO2 photocatalysis effectively generates free radicals, leading to damage in biological molecules.
• The findings support TiO2's role in photocatalyzing free radical formation and highlight potential risks in photobiological applications.