Biomimetic calcium phosphate coatings on Ti6AI4V: a crystal growth study of octacalcium phosphate and inhibition by Mg2+ and HCO3-.
The biomimetic approach for coating metal implants allows the deposition of new calcium phosphate (Ca-P) phases. Films elaborated at physiological conditions might have structures closer to bone mineral than hydroxylapatite (HA) plasma-sprayed coatings. In this study, different Ca-P coatings have been deposited through a two-step procedure. After cleaning and etching, Ti6Al4V plates were pretreated by soaking in a simulated body fluid (SBF), i.e., a solution containing inorganic components in concentration more or less similar to body fluids: a thin amorphous carbonated Ca-P layer precipitated on the metal substrate. Second, by soaking these thinly coated metal substrates in another SBF, with different concentrations, the thin amorphous carbonated Ca-P layer led to the fast precipitation of a second and thick Ca-P layer. Different SBF solutions were used in order to investigate the influence of magnesium and carbonate ions. From SBF containing only Ca2+ and HPO4(2-) ions, an octacalcium phosphate layer grew epitaxially on the substrate. When Mg2+ was added into this SBF, the coating was composed of Ca-deficient apatite crystals, while the addition of HCO3- in SBF led to the formation of a B-carbonated apatite layer. Magnesium and carbonate acted as inhibitors of crystal growth. The three phases obtained by our biomimetic process are closer to bone mineral structure than plasma-sprayed HA. Therefore, the obtained results may be particularly relevant for the development of biomimetic Ca-P coatings with optimal bioactivity.
Barrére
F
F
IsoTis BV, Bilthoven, The Netherlands. florence.barrere@isotis.nl
Layrolle
P
P
van Blitterswijk
C A
CA
de Groot
K
K
D000497:Alloys; D001639:Bicarbonates / Q000737:chemistry; D001826:Body Fluids / Q000737:chemistry; D002130:Calcium Phosphates / Q000737:chemistry*; D002413:Cations, Divalent / Q000737:chemistry; D020099:Coated Materials, Biocompatible / Q000737:chemistry*; D003460:Crystallization; D006622:Hip Prosthesis; D008274:Magnesium / Q000737:chemistry; D008855:Microscopy, Electron, Scanning; D014025:Titanium / Q000737:chemistry*
D000497:Alloys; D001639:Bicarbonates; D002130:Calcium Phosphates; D002413:Cations, Divalent; D020099:Coated Materials, Biocompatible; C485828:alpha-tricalcium phosphate; C485830:tetracalcium phosphate; C031462:titanium alloy (TiAl6V4); C022045:octacalcium phosphate; C485838:calcium phosphate, monobasic, anhydrous; C020243:calcium phosphate; D014025:Titanium; D008274:Magnesium; C485829:calcium phosphate, dibasic, anhydrous