Bactericidal effect of photocatalytically-active nanostructured TiO2 surfaces on biofilms of the early oral colonizer, Streptococcus oralis.

This study evaluated the photocatalytic bactericidal effect of nanostructured anatase-rich titanium dioxide (TiO2 ) on microbial biofilms. Commercially pure titanium discs were spin-coated with photocatalytic TiO2 nanoparticles (P25). Uncoated discs were used as control (CTRL). Half of the CTRL and half of the P25-coated surfaces were coated with purified saliva (SAL) to give four different groups (CTRL, CTRL + SAL, P25 and P25 + SAL). Streptococcus oralis were allowed to form biofilms on the discs for 18 h and non-adherent cells were rinsed off. Bacterial viability was assessed at time 0 with Live/Dead BacLight staining and epifluorescence microscopy. The remaining discs were divided into a non-UV group and UVA-irradiated (+UV) group (irradiation time, 6 or 24 h). Thereafter, viability was assessed as above. Viability at time 0 was high and no dead cells were seen on any of the surfaces, even after 24 h, in the absence of UVA. However, after 24 h of exposure, the proportion of viable cells was reduced by 40% on the P25 discs compared to 0 and 6 h, and this effect was enhanced with a salivary pellicle. Members of mixed species biofilms differ in their susceptibility to the bactericidal effect of the surfaces tested and further investigations are needed to optimize the conditions. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 2321-2328, 2017.

Using QCM-D to study the adhesion of human gingival fibroblasts on implant surfaces.

Sealing the soft tissue-implant interface is one of the key issues in preventing transcutaneous implant-associated infections. A promising surface modification for improving osseointegration and possibly soft tissue integration is to coat the implant surface with hydroxyapatite (HA) nanoparticles. When new implant materials are developed, their ability to facilitate cell attachment and spreading are commonly investigated in vitro to establish their potential for good in vivo performance. However, commonly used techniques, such as microscopy methods, are time consuming, invasive, and subjective. This is the first study using quartz crystal microbalance with dissipation monitoring, where the real-time adhesion of biopsy-derived human gingival fibroblasts onto titanium and nanostructured HA was investigated. Experiments were performed for at least 16 h, and we found that cellular attachment and spreading kinetics can be followed in situ by observing the change in dissipation and frequency with time. Interestingly, a correlation between cell coverage and the magnitude of dissipation shift reached at the end of the experiment was found, but no such trend was observed for the frequency. Furthermore, the level of cell coverage was found to influence the cellular attachment and spreading behavior. No difference in cell response to the two surface types, Ti and nanostructured HA, was found.

Biofilm formation on nanostructured hydroxyapatite-coated titanium.

Biofilm formation on medical devices is a common cause of implant failure, especially regarding implants that breach the epithelial tissue, so-called transcutaneous implants. Nanotechnology and the development of new nanomaterials have given the opportunity to design nanotextured implant surfaces. Such surfaces have been studied using various in vitro methods showing that nanosized features strongly benefit bone cell growth. However, little is known on how nanostructured features affect biofilm formation. The aim of this study was therefore to examine the shape- and chemical-dependent effect of a nanostructured hydroxyapatite (HA) coating on the degree of Staphylococcus epidermidis biofilm formation. Three different types of nanosized HA particles having different shapes and calcium to phosphate ratios were compared to uncoated turned titanium using safranin stain in a biofilm assay and confocal laser scanning microscopy (CLSM) for assessment of biofilm biomass and bacterial volume, respectively. No difference in biofilm biomass was detected for the various surfaces after 6 h incubation with S. epidermidis. Additionally, image analysis of CLSM Z-stacks confirmed the biofilm assay and showed similar results. In conclusion, the difference in nanomorphology and chemical composition of the surface coatings did not influence the adhesion and biofilm formation of S. epidermidis.