Protein Adsorption on Amorphous Metal Oxide Thin Films: An FTIR/ATR and Ellipsometry study
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Protein Adsorption on Amorphous Metal Oxide Thin Films: An FTIR/ATR and Ellipsometry study Phaedra Silva-Bermudez1,2 and Sandra E. Rodil1 1 Instituto de Investigaciones en Materiales, UNAM, Circuito Exterior s/n, C.U., 04510, México D.F. México. 2 División de Estudios de Posgrado, Facultad de Odontología, UNAM, Circuito Exterior s/n, C.U., 04510, México D.F., México. Email: [email protected] ABSTRACT The adsorption of bovine serum albumin (BSA) and fibrinogen proteins dissolved on Phosphate buffer solution onto Ta, Nb and Ti oxide thin films was studied. The metal oxide thin films were deposited by magnetron sputtering on Si(100) wafers and characterized by contact angle measurements and profilometry. Spectroscopic ellipsometry was employed to characterize the kinetics of the protein adsorption process in-situ at the solid-liquid interface and the optical properties of the adsorbed protein layer formed after 45 minutes of immersion of the thin film in the protein solution. Infrared spectroscopy was used to study the proteins within the adsorbed layer. A trend indicating that the surface mass density of the adsorbed protein layer increases as the Rt (peak-to-valley height) surface roughness parameter increases was observed for fibrinogen and BSA. An increment in the surface mass density of the adsorbed protein layer was also observed onto surfaces with higher polar components of the surface energy. BSA and fibrinogen seemed to more readily adsorbed onto tantalum oxide than onto titanium oxide.
INTRODUCTION It is well known that a cascade of biological events starts whenever an artificial material comes in close contact with biological fluids such as blood, as it is upon implantation of a biomaterial. Among all the biological events happening, adsorption of plasma proteins onto the material surface is one of the first to occur. The protein layer adsorbed onto the material’s surface, almost immediately after contact with blood, is the precursor for the subsequent biological events such as cell and platelet adhesion, coagulation, etc [1,2]. Cells adhere preferentially to specific proteins in specific conformations; thus, the type, amount, structure and conformation of the proteins adsorbed within the layer drive the response of the biological environment to the material and so these greatly determine its biocompatibility. Since the biological environment in contact with an artificial material interacts with its surface and not with the bulk, one approach to create useful biomaterials for biomedical implants is to design a material with the proper bulk properties for the implant’s performance and then tailor its surface properties towards improved biocompatibility by coating it with a biocompatible thin film. Due to the importance of protein adsorption in determining the biocompatibility of an artificial material, it is essential to develop a fundamental understanding of how proteins interact with surfaces in order to design novel and successful biocompatible coatings.
To elucidate the relations between physicochemic
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