title: The role of surface functional groups in calcium phosphate nucleation on titanium foil: a self-assembled monolayer technique.
abstract: Surface functional groups play important roles in nucleating calcium phosphate deposition on surgical titanium implants. In this study, various functional groups were introduced onto the surface of commercially pure titanium foils using a self-assembled monolayer (SAM) technique. An organic silane, 7-oct-1-enyltrichlorosilane (OETS) was used and -OH, -PO4H2, -COOH groups were derived from its unsaturated double bond. Ti foils were first oxidized in concentrated H2SO4/H2O2. ESCA and contact angle measurements were used to characterize the SAM surfaces and confirm the presence of various functional groups. A fast calcium phosphate deposition experiment was carried out by mixing Ca2+- and (PO4)(3-)-containing solutions in the presence of the surface-modified Ti samples at pH 7.4 at room temperature in order to verify the nucleating abilities of these functional groups. SEM, Raman spectroscopy, XRD and ATR-FTIR results showed that poorly crystallized hydroxyapatite (HA) can be deposited on the SAM surfaces with -PO4H2 and -COOH functional groups, but not onto the SAM with -CH=CH2 and -OH. -PO4H2 exhibited a stronger nucleating ability than that of -COOH. The oxidized Ti sample also showed some calcium phosphate deposition but to a lesser extent as compared to SAM surfaces with -PO4H2 and -COOH. The pre-deposited HA can rapidly induce biomimetic apatite layer formation after immersion in 1.5 SBF for 18 h regardless of the amount of pre-deposited HA. The results suggested that the pre-deposition of HA onto these functionalized SAM surfaces might be an effective and fast way to prepare biomimetic apatite coatings on surgical implants.
authors.affiliation: Center for Bioengineering and Biomaterials, College of Engineering, Temple University, Philadelphia, PA 19122, USA.
authors.forename: Qing
authors.initials: Q
authors.lastname: Liu
authors.forename: Jiang
authors.initials: J
authors.lastname: Ding
authors.forename: Francis K
authors.initials: FK
authors.lastname: Mante
authors.forename: Stephanie L
authors.initials: SL
authors.lastname: Wunder
authors.forename: George R
authors.initials: GR
authors.lastname: Baran
mesh_terms: D001672:Biocompatible Materials / Q000737:chemistry*; D002130:Calcium Phosphates / Q000737:chemistry*; D003460:Crystallization; D017886:Durapatite / Q000737:chemistry; D006801:Humans; D006900:Hydroxylation; D066298:In Vitro Techniques; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D010766:Phosphorylation; D019736:Prostheses and Implants; D017550:Spectroscopy, Fourier Transform Infrared; D013059:Spectrum Analysis, Raman; D013499:Surface Properties; D014025:Titanium; D014961:X-Ray Diffraction
chemical_list: D001672:Biocompatible Materials; D002130:Calcium Phosphates; D017886:Durapatite; D014025:Titanium