title: Biocompatibility and mechanical properties of diamond-like coatings on cobalt-chromium-molybdenum steel and titanium-aluminum-vanadium biomedical alloys.
abstract: Diamond-like carbon (DLC) films are favored for wear components because of diamond-like hardness, low friction, low wear, and high corrosion resistance (Schultz et al., Mat-wiss u Werkstofftech 2004;35:924-928; Lappalainen et al., J Biomed Mater Res B Appl Biomater 2003;66B:410-413; Tiainen, Diam Relat Mater 2001;10:153-160). Several studies have demonstrated their inertness, nontoxicity, and the biocompatibility, which has led to interest among manufacturers of surgical implants (Allen et al., J Biomed Mater Res B Appl Biomater 2001;58:319-328; Uzumaki et al., Diam Relat Mater 2006;15:982-988; Hauert, Diam Relat Mater 2003;12:583-589; Grill, Diam Relat Mater 2003;12:166-170). In this study, hydrogen-free amorphous, tetrahedrally bonded DLC films (ta-C) were deposited at low temperatures by physical vapor deposition on medical grade Co28Cr6Mo steel and the titanium alloy Ti6Al4V (Scheibe et al., Surf Coat Tech 1996;85:209-214). The mechanical performance of the ta-C was characterized by measuring its surface roughness, contact angle, adhesion, and wear behavior, whereas the biocompatibility was assessed by osteoblast (OB) attachment and cell viability via Live/Dead assay. There was no statistical difference found in the wettability as measured by contact angle measurements for the ta-C coated and the uncoated samples of either Co28Cr6Mo or Ti6Al4V. Rockwell C indentation and dynamic scratch testing on 2-10 μm thick ta-C films on Co28Cr6Mo substrates showed excellent adhesion with HF1 grade and up to 48 N for the critical load L(C2) during scratch testing. The ta-C coating reduced the wear from 3.5 × 10(-5) mm(3)/Nm for an uncoated control sample (uncoated Co28Cr6Mo against uncoated stainless steel) to 1.1 × 10(-7) mm(3)/Nm (coated Co28Cr6Mo against uncoated stainless steel) in reciprocating pin-on-disk testing. The lowest wear factor of 3.9 × 10(-10) mm(3)/Nm was measured using a ta-C coated steel ball running against a ta-C coated and polished Co28Cr6Mo disk. Student's t-test found that the ta-C coating had no statistically significant (p < 0.05) effect on OB attachment, when compared with the uncoated control samples. There was no significant difference (p < 0.05) in the Live/Dead assay results in cell death between the ta-C coated Co28Cr6Mo and Ti6Al4V samples and the uncoated controls. Therefore, these ta-C coatings show improved wear and corrosion (Dorner-Reisel et al., Diam Relat Mater 2003;11:823-827; Affato et al., J Biomed Mater Res B Appl Biomater 2000;53:221-226; Dorner-Reisel et al., Surf Coat Tech 2004;177-178:830-837; Kim et al., Diam Relat Mater 2004;14:35-41) performance and excellent in vitro cyto-compatibility, when compared with currently used uncoated Co28Cr6Mo and Ti6Al4V implant materials.
authors.affiliation: Fraunhofer Center for Coatings and Laser Applications, East Lansing, Michigan 48823, USA.
authors.forename: C
authors.initials: C
authors.lastname: Hinüber
authors.forename: C
authors.initials: C
authors.lastname: Kleemann
authors.forename: R J
authors.initials: RJ
authors.lastname: Friederichs
authors.forename: L
authors.initials: L
authors.lastname: Haubold
authors.forename: H J
authors.initials: HJ
authors.lastname: Scheibe
authors.forename: T
authors.initials: T
authors.lastname: Schuelke
authors.forename: C
authors.initials: C
authors.lastname: Boehlert
authors.forename: M J
authors.initials: MJ
authors.lastname: Baumann
mesh_terms: D016475:3T3 Cells; D000497:Alloys; D000818:Animals; D002448:Cell Adhesion; D002478:Cells, Cultured; D020099:Coated Materials, Biocompatible / Q000737:chemistry / Q000378:metabolism; D018130:Diamond / Q000737:chemistry / Q000378:metabolism; D006622:Hip Prosthesis; D006801:Humans; D008422:Materials Testing; D051379:Mice; D010006:Osteoblasts / Q000166:cytology / Q000502:physiology; D011475:Prosthesis Failure; D013232:Steel / Q000737:chemistry*; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry / Q000378:metabolism; D014800:Vitallium / Q000737:chemistry / Q000378:metabolism
chemical_list: D000497:Alloys; D020099:Coated Materials, Biocompatible; D013232:Steel; D014800:Vitallium; C031462:titanium alloy (TiAl6V4); D018130:Diamond; D014025:Titanium