Evaluation of bioactive coatings for titanium surfacesa proteomic approach

Resumen

At present, biologically protheses represent the current gold-standard treatments for clinical treatment of bone defects. Titanium and its alloys are among the most used metals in bone implants due to their excellent bulk properties; however, they are relatively bioinert. Surface modifications are useful to improve its bioactivity via the delivery of tissue regeneration enhancer components, such as biomolecules and ions. The sol-gel process is one of many techniques that allow this modification and design control release vehicles for bioactive compounds that can potentiate tissue regeneration. Moreover, the ever-increasing demand for better biomaterials has led to the need to improve current in vitro test methods to be more predictive and representative of the in vivo outcomes. With this purpose, the application of proteomics presents an interesting alternative to be explored. On the one hand, upon implementation, a layer of proteins immediately adheres to the material surface, consequently modulating the following biological responses. On the other hand, the characterization of the proteomic profile of cells in contact with a material can give us an insight into the cellular responses to a biomaterial. Thus, this thesis aimed to develop sol-gel coatings doped with melatonin, zinc, magnesium, and calcium-magnesium mixtures and its in vitro characterization with osteoblasts and macrophages. Then, two experimental designs employing proteomics were performed. First, the serum protein adsorption patterns onto the material surface were analyzed. Secondly, the proteomic profile of osteoblasts in contact with the material with the best in vitro response was also analyzed. The results showed that materials specific properties conditioned the proteomic profile found. For example, materials with more osteogenic potential had a greater affinity with VTNC. At the same time, the inflammatory response was associated with a higher affinity with regulators of inflammation (CLUS, IC1, CFAH, and VTNC), and an increment in cell adhesion was associated with higher affinity with DSG1, FILA2, and DESP. The analysis of the proteomic profile of cells showed that the sol-gel coatings regulated early osteoblast differentiation, insulin metabolism, cell adhesion, and oxidative stress. These results show that the effects of the material on the cells are rather complex, affecting the whole cellular machinery. Thus, the application of proteomics allowed the identification of specific markers associated with distinct biological processes such as adhesion, inflammation, coagulation, and regeneration. From the identification of the proteins adhered to the material surface and the study of the proteomic profiles of the cells exposed to it, it was possible to establish a direct relationship with the in vitro results. This opens a door to the determination of biomarkers involved in the tissue regeneration processes and possible correlation with in vivo results.