Biomimetic coatings enhance tribocorrosion behavior and cell responses of commercially pure titanium surfaces

CAPES - COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIORFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOBiofunctionalized surfaces for implants are currently receiving much attention in the health care sector. Our aims were ( 1) to create bioactive Ti-coatings doped with Ca, P, Si, and Ag produced by microarc oxidation ( MAO) to improve the surface properties of biomedical implants, ( 2) to investigate the TiO2 layer stability under wear and corrosion, and ( 3) to evaluate human mesenchymal stem cells ( hMSCs) responses cultured on the modified surfaces. Tribocorrosion and cell experiments were performed following the MAO treatment. Samples were divided as a function of different Ca/P concentrations and treatment duration. Higher Ca concentration produced larger porous and harder coatings compared to the untreated group ( p<0.001), due to the presence of rutile structure. Free potentials experiments showed lower drops ( 0.6 V) and higher coating lifetime during sliding for higher Ca concentration, whereas lower concentrations presented similar drops ( 0.8 V) compared to an untreated group wherein the drop occurred immediately after the sliding started. MAO-treated surfaces improved the matrix formation and osteogenic gene expression levels of hMSCs. Higher Ca/P ratios and the addition of Ag nanoparticles into the oxide layer presented better surface properties, tribocorrosive behavior, and cell responses. MAO is a promising technique to enhance the biological, chemical, and mechanical properties of dental implant surfaces. (C) 2016 American Vacuum Society.Biofunctionalized surfaces for implants are currently receiving much attention in the health care sector. Our aims were ( 1) to create bioactive Ti-coatings doped with Ca, P, Si, and Ag produced by microarc oxidation ( MAO) to improve the surface properties of biomedical implants, ( 2) to investigate the TiO2 layer stability under wear and corrosion, and ( 3) to evaluate human mesenchymal stem cells ( hMSCs) responses cultured on the modified surfaces. Tribocorrosion and cell experiments were performed following the MAO treatment. Samples were divided as a function of different Ca/P concentrations and treatment duration. Higher Ca concentration produced larger porous and harder coatings compared to the untreated group ( p<0.001), due to the presence of rutile structure. Free potentials experiments showed lower drops ( 0.6 V) and higher coating lifetime during sliding for higher Ca concentration, whereas lower concentrations presented similar drops ( 0.8 V) compared to an untreated group wherein the drop occurred immediately after the sliding started. MAO-treated surfaces improved the matrix formation and osteogenic gene expression levels of hMSCs. Higher Ca/P ratios and the addition of Ag nanoparticles into the oxide layer presented better surface properties, tribocorrosive behavior, and cell responses. MAO is a promising technique to enhance the biological, chemical, and mechanical properties of dental implant surfaces.113114CAPES - COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIORFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCAPES - COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIORFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO11838-13-22013/08451-1The authors would like to thank the University of Illinois at Chicago for providing the facilities to perform this study, Rush University Medical Center on behalf of R. Urban for the SEM facility, Denise Carleto Andia for providing the human bone marrow stromal cells for some cell experiments, Rafael Parra from Univ Estadual Paulista (Sorocaba, Brazil) for his contribution and support in the Plasma Technology Laboratory, the Coordination for the Improvement of Higher Level Personnel (CAPES) from Brazil for the doctoral fellowship of the first author (PDSE Proc. 11838-13-2), the State of Sao Paulo Research Foundation (FAPESP) for Grant No. 2013/08451-1, the National Science Foundation (NSF) for Grant No. 1067424, and finally financial support from NIH R03 AR064005

Tribocorrosive behaviour of commonly used temporomandibular implants in a synovial fluid-like environment: Ti-6Al-4V and CoCrMo

The temporomandibular joint implant metal alloys, Ti6Al4V and CoCrMo, (n = 3/group) were tested under free-potential and potentiostatic conditions using a custom-made tribocorrosion apparatus. Sliding duration (1800 cycles), frequency (1.0 Hz) and load (16 N) mimicked the daily mastication process. Synovial-like fluid (bovine calf serum, pH = 7.6 at 37 °C) was used to simulate the in vivo environment. Changes in friction coefficient were monitored throughout the sliding process. Changes in surface topography, total weight loss and roughness values were calculated using scanning electron microscopy and white-light interferometry. Finally, statistical analyses were performed using paired t-tests to determine significance between regions within each metal type and also independent sample t-tests to determine statistical significance between metal alloy types. Ti6Al4V demonstrated a greater decrease of potential than CoCrMo, a higher weight loss from wear (Kw = 257.8 versus 2.62 μg; p \u3c 0.0001), a higher weight loss from corrosion (Kc = 17.44 versus 0.14 μg; p \u3c 0.0001) and a higher weight loss from the combined effects of wear and corrosion (Kwc = 275.28 versus 2.76 μg; p \u3c 0.0001). White-light interferometry measurements demonstrated a greater difference in surface roughness inside the wear region in Ti6Al4V than CoCrMo after the sliding (Ra = 323.80 versus 70.74 nm; p \u3c 0.0001). In conclusion, CoCrMo alloy shows superior anti-corrosive and biomechanical properties. © 2013 IOP Publishing Ltd

Room-temperature relaxor ferroelectricity and photovoltaic effects in tin titanate directly deposited on silicon substrate

Tin titanate (SnTiO3) has been notoriously impossible to prepare as a thin-film ferroelectric, probably because high-temperature annealing converts much of the Sn2+ to Sn4+. In the present paper, we show two things: first, perovskite phase SnTiO3 can be prepared by ALD directly onto p-type Si substrates; and second, these films exhibit ferroelectric switching at room temperature, with p-type Si acting as electrodes. X-ray diffraction (XRD) measurements reveal that the film is single-phase, preferred-orientation ferroelectric perovskite SnTiO3. Our films showed well-saturated, square and repeatable hysteresis loopsof around 3 μC/cm2 remnant polarization at room temperature, as detected by out-of-plane polarization versus electric field (P-E) and field cycling measurements. Furthermore, photovoltaic and photoferroelectricity were found in Pt/SnTiO3/Si/SnTiO3/Pt heterostructures, of which properties can be tuned through band gap engineering by strain according to the first-principles calculations. This is a new lead-free room-temperature ferroelectric oxide of potential device application

Room-temperature relaxor ferroelectricity and photovoltaic effects in tin titanate directly deposited on a silicon substrate

Tin titanate (SnTiO3) has been notoriously impossible to prepare as a thin-film ferroelectric, probably because high-temperature annealing converts much of the Sn2+ to Sn4+. In the present paper, we show two things: first, perovskite phase SnTiO3 can be prepared by atomic-layer deposition directly onto p-type Si substrates; and second, these films exhibit ferroelectric switching at room temperature, with p-type Si acting as electrodes. X-ray diffraction measurements reveal that the film is single-phase, preferred-orientation ferroelectric perovskite SnTiO3. Our films showed well-saturated, square, and repeatable hysteresis loops of around 3 mu C/cm(2) remnant polarization at room temperature, as detected by out-of-plane polarization versus electric field and field cycling measurements. Furthermore, photovoltaic and photoferroelectricity were found in Pt/SnTiO3/Si/SnTiO3/Pt heterostructures, the properties of which can be tuned through band-gap engineering by strain according to first-principles calculations. This is a lead-free room-temperature ferroelectric oxide of potential device application