title: Apatite deposition on titanium surfaces--the role of albumin adsorption.
abstract: Titanium implant surfaces are known to spontaneously nucleate apatite layers when in contact with simulated body fluids. However, adsorption of proteins may influence the process of apatite layer formation. In this study the role of bovine serum albumin (BSA) adsorption in the process of apatite deposition on titanium substrates is investigated. Deposition of calcium phosphate was induced by immersing titanium substrates in a Hank's balanced salt solution (HBSS) for times ranging from 1 to 23 days. The resulting substrates were studied by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), wettability measurements and electrochemical impedance determinations. All these methods indicate the presence of a calcium phosphate layer. The same procedure was repeated substituting HBSS with a solution of BSA in HBSS. Although SEM, EDS and electrochemical impedance spectra do not reveal the presence of an apatite layer, XPS analysis strongly indicates that the inhibition of apatite formation by BSA is only partial. The competition between BSA adsorption and apatite deposition seems to lead to a mixed film where the protein co-exists with calcium phosphate. Wettability studies suggest that this surface film is heterogeneous and porous, similar to the thicker films formed in albumin-free HBSS.
authors.affiliation: Centro de Química Estrutural, Complexo I, Instituto Superior Técnico,Lisboa, Portugal.
authors.forename: A P
authors.initials: AP
authors.lastname: Serro
authors.forename: A C
authors.initials: AC
authors.lastname: Fernandes
authors.forename: B
authors.initials: B
authors.lastname: Saramago
authors.forename: J
authors.initials: J
authors.lastname: Lima
authors.forename: M A
authors.initials: MA
authors.lastname: Barbosa
mesh_terms: D000327:Adsorption; D000818:Animals; D001031:Apatites / Q000378:metabolism*; D001665:Binding Sites; D002130:Calcium Phosphates / Q000378:metabolism; D002417:Cattle; D017097:Electric Impedance; D007552:Isotonic Solutions / Q000737:chemistry; D008855:Microscopy, Electron, Scanning; D019736:Prostheses and Implants / Q000592:standards; D012710:Serum Albumin, Bovine / Q000378:metabolism*; D013052:Spectrometry, X-Ray Emission; D013499:Surface Properties; D014021:Tissue Preservation; D014025:Titanium / Q000737:chemistry* / Q000378:metabolism
chemical_list: D001031:Apatites; D002130:Calcium Phosphates; C072670:Hanks Balanced Salt Solution; D007552:Isotonic Solutions; C485828:alpha-tricalcium phosphate; C485830:tetracalcium phosphate; D012710:Serum Albumin, Bovine; C485838:calcium phosphate, monobasic, anhydrous; C020243:calcium phosphate; D014025:Titanium; C485829:calcium phosphate, dibasic, anhydrous