title: Modification of Ti6Al4V implant surfaces by biocompatible TiO2/PCL hybrid layers prepared via sol-gel dip coating: Structural characterization, mechanical and corrosion behavior.
abstract: Surface modification of metallic implants is a promising strategy to improve tissue tolerance, osseointegration and corrosion resistance of them. In the present work, bioactive and biocompatible organic-inorganic hybrid coatings were prepared using a sol-gel dip coating route. They consist of an inorganic TiO2matrix in which different percentages of poly(ε-caprolactone) (PCL), a biodegradable and biocompatible polymer, were incorporated. The coatings were used to modify the surface of Ti6Al4V substrates in order to improve their wear and corrosion resistance. The chemical structure of the coatings was analyzed by attenuated total reflectance (ATR) Fourier transform infrared (FTIR) spectroscopy. Coating microstructure, mechanical properties and ability to inhibit the corrosion of the substrates were evaluated as a function of the PCL amount. Scanning electron microscopy (SEM) showed that the polymer allows to obtain crack-free coatings, but when high percentages were added uncoated areas appear. Nano-indentation tests revealed that, as expected, surface hardness and elastic modulus decrease as the percentage of polymeric matrix increases, but scratch testing demonstrated that the coatings are effective in preventing scratching of the underlying metallic substrate, at least for PCL contents up to 20wt%. The electrochemical tests (polarization curves acquired in order to evaluate the corrosion resistance) allowed to asses that the coatings have a significant effect in term of corrosion potential (Ecorr) but they do not significantly affect the passivation process that titanium undergoes in contact with the test solution used (modified Dulbecco's phosphate-buffered saline or DPBS).
authors.affiliation: Department of Industrial and Information Engineering, Second University of Naples, Via Roma 21, 81031 Aversa, Italy. Electronic address: michelina.catauro@unina2.it.
authors.forename: Michelina
authors.initials: M
authors.lastname: Catauro
authors.affiliation: Department of Industrial and Information Engineering, Second University of Naples, Via Roma 21, 81031 Aversa, Italy.
authors.forename: Flavia
authors.initials: F
authors.lastname: Bollino
authors.affiliation: Department of Engineering "Enzo Ferrari", University of Modena and Reggio Emilia, Via Vivarelli 10, 41125 Modena, Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Giovanardi
authors.affiliation: Department of Engineering "Enzo Ferrari", University of Modena and Reggio Emilia, Via Vivarelli 10, 41125 Modena, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Veronesi
mesh_terms: D000497:Alloys; D020099:Coated Materials, Biocompatible / Q000737:chemistry; D003343:Corrosion; D055664:Electrochemical Techniques; D004566:Electrodes; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D011091:Polyesters / Q000737:chemistry*; D019736:Prostheses and Implants; D017550:Spectroscopy, Fourier Transform Infrared; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry*
chemical_list: D000497:Alloys; D020099:Coated Materials, Biocompatible; D011091:Polyesters; C031462:titanium alloy (TiAl6V4); C009495:titanium dioxide; C016240:polycaprolactone; D014025:Titanium
keywords: Corrosion behavior; Dip coating technique; Organic-inorganic hybrid materials; Scratch test; Sol-gel process