Antibacterial activity of inorganic and hybrid coatings based on SiO₂, TiO₂ and IrO_x

Titanium-based materials are commonly used for biomedical applications, especially in the dentistry and orthopedic fields, as they are characterized by a wide spectrum of morphological, compositional, and functional parameters. The intensive development of reliable dental implants relies on certain features such as appropriate mechanical resistance, biocompatibility, and the ability to promote Osseo integration. The aim of the work was the identification of the key parameters for obtaining inorganic and hybrid materials coatings appropriate for biomedical application (i.e. dental implants) with intrinsic antibacterial activity. For this purpose, nanostructured TiO₂ modified with Au/Ag metal nanoparticles and lysozyme, coated on titanium foil was synthesized. Scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), photoluminescence (PL), and UV–Vis spectroscopies were used to investigate the morphological, structural and functional properties of the resulting coatings. Several paths were studied as follows. Firstly, the singlet oxygen (¹O₂) generation by inorganic coatings exposed to visible light irradiation was carried out. Then, the antibacterial activity of the TiO₂/Ti, Au–TiO₂/Ti, and Ag–TiO₂/Ti was assessed. The lysozyme bioactivity for Micrococcus lysodeicticus, used as microbial substrate, was evaluated after its adsorption on Lys/TiO₂/Ti, Lys/Au–TiO₂/Ti and Lys/Ag–TiO₂/Ti inorganic surfaces. Finally, the enzymatic activity of the hybrids materials for the hydrolysis reaction of a synthetic organic substrate, 4-Methylumbelliferyl_-D-N,N0,N”-triacetylchitotrioside [4-MU-_- (GlcNAc)3], was emphasized by identifying the presence of a fluorescent reaction product, 7-hydroxy-4-metyl coumarin (4-methylumbelliferone)