Crystalline titanium oxides have shown photocatalytic activity (PCA) and the formation of antibacterial reactive oxygen species (ROS) when stimulated with UV light. Polyaniline (PANI) is a conductive polymer that has shown antibacterial effects. Previously, titanium oxides have been PANI-doped using a multi-step approach. In the present study, we compared PANI-doped specimens produced with a two-step method (ACV), to PANI-doped specimens produced by a novel single-step direct anodization (AAn) method, and a control group of anodized un-doped specimens. The surface morphology, oxide crystallinity, surface elemental composition, surface roughness, surface wettability, oxide adhesion, corrosion resistance, PCA, and ROS generation of each oxide group were evaluated. All groups exhibited mixed anatase and rutile phase oxides. The AAn group revealed less anatase and rutile, but more PANI-surface coverage. The AAn group exhibited significantly increased PCA after 60 minutes of direct UVA illumination compared to the ACV group, despite containing lower amounts of anatase and rutile. The ACV and AAn groups showed significant increases in ROS production after 4 hours UVA illumination while the control group showed similar ROS production. These findings suggested that PANI doping using the novel direct anodization technique significantly improved PCA even for oxides containing less crystallinity. The S. aureus attachment response to each oxide group was also compared under UVA pre-illumination, UVA direct illumination, and no illumination (dark) lighting conditions. Although no significant differences were shown in the bacterial response, both PANI-doped groups exhibited less average bacterial attachment compared to the control group. The response of MC3T3-E1 pre-osteoblast cells to each oxide group was evaluated using MTT and live/dead assays, and no evidence of cytotoxicity was found. Since many, if not most, titanium implant devices are routinely anodized as a part of the manufacturing processes, these study findings are applicable to a wide variety of implant applications.
The mechanical stability and long‐term success of an implant depends on the early healing phase and osseointegration of the bone around it. In addition, a healthy gingival tissue around the implant acts as a barrier that prevents bacteria and pathological byproducts from reaching the implant site. This study investigated the in‐vitro attachment and spreading of human gingival fibroblasts (HGF) on bacterial grade polystyrene (PS) at different distances from radio‐frequency glow‐discharge (RFGD)‐treated commercially pure titanium (cpTi) specimens. Controls included sterile cpTi specimens without RFGD treatment. A second set of experiments utilized media transferred to new bacterial grade polystyrene dishes (no cpTi) after the medium was conditioned by exposure to cpTi, either with or without RFGD treatment, for 24 hr. Surface characterization of the dishes was conducted through contact angle measurements and infrared spectroscopy. Cell numbers and surface areas were determined from Image J analysis of multiple microscopic images of fixed, stained cells. The results showed significantly greater numbers and surface areas on bacterial grade PS dishes at distances up to 15 mm from the RFGD‐treated cpTi groups than for the controls. Moreover, a significant effect of the conditioned medium from RFGD‐treated cpTi versus control cultures was shown on the numbers of fibroblasts attached to bacterial grade polystyrene dishes after 24 hr (p < 0.005) and 48 hr (p = 0.002) incubation. Surface areas of cells exposed to conditioned medium were not significantly different (p ≥ 0.05). Surface characterization of the PS dishes showed a higher value of the critical surface tensions of the treated group when compared to the control group.
Titanium anodization has been shown to produce crystalline oxides exhibiting photocatalytic reactions that form reactive oxygen species (ROS) when exposed to UV light. The ROS subsequently attack bacteria cells, and thus reduce bacteria attachment on titanium implant surfaces. Polyaniline (PANI) is a conductive polymer that has shown antibacterial properties when electropolymerized onto titanium. Our research group hypothesized the addition of PANI to crystalline titanium oxide surfaces would increase the available free electrons and thus increase photocatalytic activity (PCA). This research led to the development of a novel single‐step anodization approach for PANI doping crystalline titanium oxide layers. The objective of the present study was to determine the proper aniline electrolyte concentration needed to maximize the PCA and reduce bacterial attachment on the formed oxides. Aniline concentrations up to 1 M were added into a 1 M sulfuric acid electrolyte. The formed oxides exhibited increased PANI surface coverage but decreased anatase and rutile crystalline titanium oxide phase formation with increasing aniline electrolyte concentrations. Despite exhibiting the lowest levels of anatase and rutile formation, the 0.75 M and 1 M aniline oxides with the greatest PANI surface coverage also exhibited the highest PCA levels. 1 M aniline oxides showed significantly higher PCA under UVA irradiation compared to oxides formed from aniline concentrations up to 0.5 M (p < 0.001). 0.75 M aniline oxides exhibited significant reductions in Staphylococcus aureus attachment with or without UVA irradiation compared to control oxides without PANI. MTT and live/dead assays confirmed cytocompatibility and nearly 100% cell viability for the PANI doped oxides.
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