Adsorption of Guanine on Oxygen-Deficient TiO<sub>2</sub> Surface:\nA Combined MD-DFTB/DFT Strategy

Metal oxides (MOs)\nare key materials in many fields, including\ntechnological, industrial, and biomedical applications. In most of\nthese implementations, surface reactivity and reducibility properties\nare critical considerations. In their nanosized form, MOs exhibit\nenhanced reactivity that is connected to toxicity. Besides the fact\nthat the biological molecule and the surface of the corresponding\nmaterial interact chemically, little is known about the toxicological\nmechanisms involved on the atomic scale. The goal of this study is\nto investigate the role of TiO<sub>2</sub> surfaces in interaction\nwith one genetic base, namely guanine. Using a combination of the\nquasi-electronic density functional-tight binding molecular dynamics\nsimulations and density functional theory calculations, we explored\nthe adsorption modes of guanine with a stoichiometric and oxygen-deficient\nanatase TiO<sub>2</sub> (101) surface. With such an approach, we have\ncharacterized new adsorption modes not previously found, and we have\nhighlighted the relevance of defective surfaces in the adsorption\nof genetic basis, as a model for explaining possible toxicology mechanisms\ninduced by the adsorption process.