Resumen de Functionalized cocr surfaces with adhesive molecules to improve endothelialization
Maria Isabel Castellanos Arboleda
Cobalt-chromium (CoCr) alloys are widely used as biomaterials for coronary stents due to their excellent mechanical properties, biocompatibility and corrosion resistance. However, these materials are bioinert, retarding the complete endothelialization and resulting in a higher risk of restenosis, narrowing of the artery, and late-stent thrombosis. Therefore, the improvement of implants surface endothelialization has acquired importance in the last years.
Immobilization of cell adhesive biomolecules onto biomaterials surface is a well-known strategy to control cell response. However, the strategy of immobilization, the optimal combination or the appropriate spatial presentation of the bioactive sequences to enhance endothelialization for cardiovascular applications, remains to be elucidated.
The present PhD thesis focused on the development of a new biofunctionalized CoCr alloy surfaces in order to improve the endothelialization. To that end, elastin-like recombinamers (ELR) genetically modified with an REDV (Arg-Glu-Asp-Val) sequence and short synthetized peptides RGDS (Arg-Gly-Asp-Ser), REDV, YIGSR (Tyr-Ile-Gly-Ser-Arg) and their equimolar combination, were attached by physisorption and covalent bonding onto CoCr alloy surfaces and thoroughly characterized physico-chemically and evaluated in vitro with human umbilical vein endothelial cells (HUVECs), coronary artery smooth muscle cells (CASMCs) and platelets from blood donors.
First, biofunctionalized surfaces with ELR were developed and optimized by evaluating different surface activation treatments, oxygen plasma and sodium hydroxide etching, and different binding strategies, physisorption and covalent bonding. The functionalized surfaces demonstrated a higher cell adhesion and spreading of HUVEC cells, this effect is emphasized as increases the amount of immobilized biomolecules and directly related to the immobilization technique: covalent bonding. Nevertheless, the silanization process was not completely effective since a mixture of covalent and physisorption behavior was observed probably due to the use of big molecules that decreased the control of the bonding between the biomolecule and the surface. Secondly, it was synthetized immobilized RGDS, REDV, YIGSR and their equimolar combination peptides onto the different surfaces. Cell studies demonstrated that the covalent functionalization of CoCr surfaces with an equimolar combination of RGDS/YIGSR represented the most powerful strategy to enhance the early stages of HUVECs adhesion, proliferation and migration, indicating a positive synergistic effect between the two peptide motifs. Besides, gene expression and platelet adhesion studies showed that surfaces silanized with the combination RGDS/YIGSR improved anti-thrombogenicity compared to non-modified surfaces.
Finally, cell co-cultures of HUVECs/CASMCs found that functionalization increased the amount of adhered HUVECs onto modified surfaces compared to plain CoCr, independently of the used peptide and the strategy of immobilization. Overall, the present thesis offer a comprehensive view of the effectiveness of immobilizing cell adhesive molecules onto CoCr alloy surfaces to enhance endothelialization while preventing restenosis and thrombosis for cardiovascular applications.
