Energy landscape of glutamine (L) ON Au / Ag / Cu doped TiO2 surfaces and potential biomedical applications

A better understanding of the molecular inorganic-organic interactions in biological environments is of key importance for understanding physiological processes, and the safe application of medical implants, medicaments, drug delivery systems, etc. In this study, Glutamine (L) was selected as the model molecule for the investigation of inorganic-organic interactions due to its important role in cancer metabolism - it serves as an alternative to glucose for fueling the tricarboxylic acid (TCA) cycle in cancer cells, with many tumor cells relying on extracellular glutamine for survival [1,2], while one of the inorganic materials that show antitumor properties is titanium dioxide, and Au / Ag / Cu doped TiO2 particles showed toxic effects on several cancer cell lines. To simulate the interactions between nanoparticles and an amino acid molecule in a vacuum, we constructed systems with different glutamine conformations onto 2D slab surfaces of anatase TiO2, oriented along the (001) and (101) planes, both in their pristine form and doped with Au, Ag, or Cu. Ab initio calculations were performed using Density Functional Theory (DFT) with the LDA and GGA-PBE functionals, employing two different computational codes-CRYSTAL17 and Quantum Espresso [3]. To optimize the search for low-energy configurations of molecule on ceramic-type surfaces, we implemented an iterative approach that alternated between doped and undoped surfaces, which proved to be highly efficient for identifying stable structures in inorganic–organic systems of this nature. We observed 3 different types of molecule adsorption on the surfaces - the physical interaction, chemical interaction, and breaking up of a molecule/separation of H atoms from a molecule, with significant deformations. The presented results can contribute to general investigations of biomolecules on metal-oxide surfaces, as well as to the potential design of new anticancer materials and drug delivery systems, nanoscale therapeutics, environmental remediation, catalytic, and corrosion-resistant materials [3].