Nitrogen and bismuth-doped TiO2 coating for dental implants: photocatalytic performance under visible light and antimicrobial effect

Author(s)

Bruna Egumi Nagay

• Document type: Master's Dissertation
• Press: Piracicaba, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Faculdade de Odontologia de Piracicaba
• Defense date: 2019-02-22

Examining board members

Valentim Adelino Ricardo Barão; Aldiéris Alves Pesqueira; Nilson Cristino da Cruz

• Advisor: Valentim Adelino Ricardo Barão

Abstract

The improvement of biomaterials for dental implants that reduces bacterial adhesion is necessary for the prevention of peri-implant infections. The coating with titanium dioxide (TiO2), known for its excellent antibacterial photocatalytic properties, would be a great alternative for the treatment of peri-implantitis if its effect was not limited to ultraviolet (UV) light spectrum. Since UV has potential carcinogenic effect, doping TiO2 with nitrogen (N) and bismuth (Bi) could be an option to achieve photocatalytic effect under visible light. The purpose of this study was to develop a N,Bi-codoped TiO2 coating on the surface of commercially pure titanium (cpTi) discs via plasma electrolytic oxidation (PEO) to investigate the photocatalytic and antibacterial activities of the coating under the presence and absence of visible light. Ammonium acetate was used to form crystalline TiO2 and to incorporate N, urea was used as an additional source of N and bismuth nitrate was used as Bi precursor. The studied groups were: (1) polished cpTi (control group); (2) TiO2 (PEO with TiO2); (3) U-TiO2 (PEO with TiO2 and urea); (4) Bi-TiO2 (PEO with TiO2 and Bi); (5) U, Bi-TiO2 (PEO with TiO2, urea and Bi). Discs¿ surfaces were characterized in terms of morphology (scanning electron microscopy - SEM and confocal laser scanning microscopy), chemical composition (energy dispersive spectrometry and X-ray excited photoelectron spectroscopy), crystal structure (X-ray diffraction), roughness (profilometry), wettability (water contact angle) and band gap (UV-visible diffuse reflectance spectroscopy). The photocatalytic activity and the reusability (after 24 h and 72 h) were evaluated using the methyl orange (MO) degradation assay. The bacterial adhesion (2 h) and biofilm (24 h) composed of Streptococcus sanguinis and Actinomyces naeslundii on discs were evaluated after irradiation or not (dark) of the biofilm with visible light (30 min; LED 105W, ? = 420 nm - 690 nm, 45 mW/cm²) by colony forming units and structure (SEM). Albumin adsorption on the surfaces was evaluated using the bicinchoninic acid method. Data were subjected to analysis of variance (ANOVA) and Tukey HSD test (?=0.05). PEO formed crystalline TiO2 doped with the proposed elements. The experimental surfaces showed greater roughness, hydrophilicity and albumin adsorption compared to cpTi (p<0.05). Bi-TiO2 and U,Bi-TiO2 presented the lowest band gap values and greater degradation of MO in both light and dark conditions when compared to the other groups (p<0.05), with photocatalytic effect even after 72 h from the first analysis. The groups with Bi, especially Bi-TiO2 group, presented antibacterial activity against 24-h biofilm formation after 30 min in the dark compared to cpTi (p <0.05), and this effect was potentiated in the presence of light (?1 log). These results support the use of Bi-TiO2 coating synthesized via PEO as an alternative for the surface treatment of dental implants and for the control of peri-implant infections, presenting ability to increase the adsorption of albumin and antibacterial activity (24 h biofilm) in the dark with greater effect after the application of visible light (AU)

• FAPESP's process: 17/00314-6 - Photocatalytic antibacterial activity of Nb2O5-doped TiO2 films deposited by plasma electrolytic oxidation onto commercially-pure titanium surface.
• Grantee: Bruna Egumi Nagay
• Support Opportunities: Scholarships in Brazil - Master