Enhanced osteoconductivity of titanium implant by polarization-induced surface charges

Electrically polarized TiO2 nanotubes on Ti implants to enhance early-stage osseointegration

Ti is characteristically bioinert and is supplemented with modifications in surface topography and chemistry to find use in biomedical applications. The aim of this study is to understand the effects of surface charge on TiO2 nanotubes (TNT) on Ti implants towards early stage osseointegration. We hypothesize that charge storage on TNT will improve bioactivity and enhance early-stage osseointegration in vivo. Commercially pure Ti surface was altered by growing TNT via anodic oxidation followed by the introduction of surface charge through electrothermal polarization to form bioelectret. Our results indicate a stored charge of 37.15 ± 14 mC/cm2 for TNT surfaces. The polarized TNT (TNT-Ps) samples did not show any charge leakage up to 18 months, and improved wettability with a measured contact angle less than 1°. No cellular toxicity through osteoblast proliferation and differentiation in vitro were shown by the TNT-Ps. Enhanced new bone formation at 5 weeks post-implantation for the TNT-Ps in contrast to TNTs was observed in vivo. Histomorphometric analyses show ∼40% increase in mineralized bone formation around the TNT-P implants than the TNTs at 5 weeks, which is indicative of accelerated bone remodeling cycle. These results show that stored surface charge on TiO2 nanotubes helped to accelerate bone healing due to early-stage osseointegration in vivo. STATEMENT OF SIGNIFICANCE: To improve surface bioactivity of metallic biomaterials, various approaches have been proposed and implemented. Among them, stored surface charge has been explored to enhance biological responses for hydroxyapatite ceramics where charged surfaces show favorable bone tissue ingrowth. However, surface charge effects have not yet been explored as a way to mitigate bio-inertness of titanium. This study intends to understand novel integration of bioactive titania-nanotubes and charge storage as surface modification for titanium implants. Our results show excellent biological response due to surface charge on titania-nanotubes offering possibilities of faster healing particularly for patients with compromised bone health.

Enhanced osteoconductivity on electrically charged titanium implants treated by physicochemical surface modifications methods

Biomimetic design is a key tenet of orthopedic device technology, and in particular the development of responsive surfaces that promote ion exchange with interfacing tissues, facilitating the ionic events that occur naturally during bone repair, hold promise in orthopedic fixation strategies. Non-bioactive nanostructured titanium implants treated by shot-blasting and acid-etching (AE) induced higher bone implant contact (BIC=52% and 65%) compared to shot-blasted treated (SB) implants (BIC=46% and 47%) at weeks 4 and 8, respectively. However, bioactive charged implants produced by plasma (PL) or thermochemical (BIO) processes exhibited enhanced osteoconductivity through specific ionic surface-tissue exchange (PL, BIC= 69% and 77% and BIO, BIC= 85% and 87% at weeks 4 and 8 respectively). Furthermore, bioactive surfaces (PL and BIO) showed functional mechanical stability (resonance frequency analyses) as early as 4 weeks post implantation via increased total bone area (BAT=56% and 59%) ingrowth compared to SB (BAT=35%) and AE (BAT=35%) surfaces.

Suppression effects of dental glass-ceramics with polarization-induced highly dense surface charges against bacterial adhesion

This study investigated the surface characteristics and antibacterial ability capacity of surface-improved dental glass-ceramics by an electrical polarization process. Commercially available dental glass-ceramic materials were electrically polarized to induce surface charges in a direct current field by heating. The surface morphology, chemical composition, crystal structure, and surface free energy (SFE) were evaluated using scanning electron microscopy, energy dispersive X-ray spectrometry, X-ray diffraction, and water droplet methods, respectively. The antibacterial capacity was assessed by a bacterial adhesion test using Streptococcus mutans. Although the surface morphology, chemical composition, and crystal structure were not affected by electrical polarization, the polar component and total SFE were enhanced. After 24 h incubation at 37ºC, bacterial adhesion to the polarized samples was inhibited. The electrical polarization method may confer antibacterial properties on prosthetic devices, such as porcelain fused to metal crowns or all ceramic restorations, without any additional bactericidal agents.