Magnetron sputtering deposition of tantalum oxide (Ta2O5) films onto titanium surface for biomedical applications: electrochemical behavior, biocompatibility and microbiologic analysis

Author(s)

Thamara Beline

• Document type: Doctoral Thesis
• Press: Piracicaba, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Faculdade de Odontologia de Piracicaba
• Defense date: 2020-02-21

Examining board members

Valentim Adelino Ricardo Barão; Jose Humberto Dias da Silva; Ricardo Armini Caldas; Francisco Humberto Nociti Junior; Marcelo Ferraz Mesquita

• Advisor: Valentim Adelino Ricardo Barão

Abstract

This study aimed to tailor the synthesis and controlling the properties of tantalum (Ta)-based thin films onto a commercially pure titanium (cpTi) surface by magnetron sputtering technique. Firstly, TaxOy films with different structures (amorphous or crystalline) were produced depending on the various oxygen flow rates and parameters used. The structural and optical properties, morphology, roughness, chemical composition and surface energy were assessed. The impact of TaxOy films on initial Streptococcus sanguinis adhesion was investigated. The morphology and spreading of pre-osteoblastic (MC3T3-E1) cells on a crystalline tantalum oxide film were evaluated. X-ray diffraction (XRD) analysis revealed that the 8 O2 sccm (600 °C/400 W) group showed crystallization corresponding to the beta-Ta2O5 phase. Optical analysis showed that the 4 O2 sccm (200 °C/300 W) to 8 O2 sccm (600 °C/300 W) groups and 10 O2 sccm (200 °C/300 W) group presented regular interference oscillations, suggesting high homogeneity of the films. The crystalline beta-Ta2O5 coating showed higher roughness and surface energy values than the other groups (p<.05) and was biocompatible. Compared with cpTi, the amorphous and crystalline tantalum oxide films did not increase bacterial adhesion (p>.05). Subsequently, a second in vitro study was developed which, in addition to evaluating the physical and chemical properties, analyzed the electrochemical and biological performances of the crystalline Ta2O5 film. CpTi disks were randomly divided into two groups: polished cpTi (control) and cpTi treated with Ta2O5 film (experimental). Surfaces were characterized by XRD, atomic force microscopy (AFM), surface energy and x-ray photoelectron spectroscopy (XPS). The electrochemical tests were conducted in simulated body fluid (SBF) and the open circuit potential, electrochemical impedance spectroscopy and potentiodynamic tests were performed according to the standardized method of three-cell electrodes. For biological assay, the protein adsorption of albumin and fibrinogen were investigated by electrochemical quartz crystal microbalance (EQCM). MC3T3-E1 cells were cultured on the cpTi surfaces and the metabolic analysis (MTT) and the morphology (SEM) were evaluated after 1, 2 and 4 days. Also, fluorescence microscopy was used to evaluate the morphology after 1 and 2 days of cell culturing. The mineralization was determined via staining with Alizarin Red-S after 4, 7 and 14 days. The expression levels of runt-related transcription factor 2 (RUNX2), alkaline phosphatase (ALP), osteocalcin (OC), Collagen-1 (Col-1) were analyzed after 1, 2 and 3 days. The bioactivity was evaluated by immersion of the coating in SBF for 14 days. Changes in surface topography were noted in AFM analysis for Ta2O5 group. Higher values of surface roughness and surface energy were found for Ta2O5 group (p<.05). Higher values of corrosion resistance were noted for Ta2O5 group (p<.05). More positive values of corrosion potential (Ecorr) and lower values of corrosion current density (Icorr) and corrosion rate were found for Ta2O5 group (p<.05). No statistically significant differences were found between the groups for protein adsorption (p>.05). Morphology analysis revealed that Ta2O5-treated surface positively impacted the cell morphology and spreading. In the mineralization test, Ta2O5 group showed the highest calcium ion concentration values when compared with cpTi surface on day 14 (p<.05). Ta2O5 group showed higher RUNX2 expression values on day 1 and higher OC and Col-1 expression on day 3 when compared with cpTi (p<.05). Tantalum oxide films were able to improve the surface properties, the electrochemical stability and the biocompatibility of cpTi (AU)

• FAPESP's process: 16/07269-3 - Magnetron sputtering deposition of tantalum oxide (Ta2O5) films onto titanium surface for biomedical applications: electrochemical behavior, biocompatibility and microbiologic analysis
• Grantee: Thamara Beline
• Support Opportunities: Scholarships in Brazil - Doctorate