Effect of a Nanostructured Titanium Surface on Gingival Cell Adhesion, Viability and Properties against P. gingivalis.

OBJECTIVES: The transgingival part of titanium implants is either machined or polished. Cell-surface interactions as a result of nano-modified surfaces could help gingival fibroblast adhesion and support antibacterial properties by means of the physico-mechanical aspects of the surfaces. The aim of the present study was to determine how a nanocavity titanium surface affects the viability and adhesion of human gingival fibroblasts (HGF-1). Additionally, its properties against Porphyromonas gingivalis were tested. MATERIAL AND METHODS: Two different specimens were evaluated: commercially available machined titanium discs (MD) and nanostructured discs (ND). To obtain ND, machined titanium discs with a diameter of 15 mm were etched with a 1:1 mixture of 98% H2SO4 and 30% H2O2 (piranha etching) for 5 h at room temperature. Surface topography characterization was performed via scanning electron microscopy (SEM) and atomic force microscopy (AFM). Samples were exposed to HGF-1 to assess the effect on cell viability and adhesion, which were compared between the two groups by means of MTT assay, immunofluorescence and flow cytometry. After incubation with P. gingivalis, antibacterial properties of MD and ND were determined by conventional culturing, live/dead staining and SEM. Results: The present study successfully created a nanostructured surface on commercially available machined titanium discs. The etching process created cavities with a 10-20 nm edge-to-edge diameter. MD and ND show similar adhesion forces equal to about 10-30 nN. The achieved nanostructuration reduced the cell alignment along machining structures and did not negatively affect the proliferation of gingival fibroblasts when compared to MD. No differences in the expression levels of both actin and vinculin proteins, after incubation on MD or ND, were observed. However, the novel ND surface failed to show antibacterial effects against P. gingivalis. CONCLUSION: Antibacterial effects against P. gingivalis cannot be achieved with nanocavities within a range of 10-20 nm and based on the piranha etching procedure. The proliferation of HGF-1 and the expression levels and localization of the structural proteins actin and vinculin were not influenced by the surface nanostructuration. Further studies on the strength of the gingival cell adhesion should be performed in the future. CLINICAL RELEVANCE: Since osseointegration is well investigated, mucointegration is an important part of future research and developments. Little is known about how nanostructures on the machined transgingival part of an implant could possibly influence the surrounding tissue. Targeting titanium surfaces with improved antimicrobial properties requires extensive preclinical basic research to gain clinical relevance.

Differentiation of human mesenchymal stem cells on plasma-treated polyetheretherketone.

Polyetheretherketone (PEEK) generally exhibits physical and chemical characteristics that prevent osseointegration. To activate the PEEK surface, we applied oxygen and ammonia plasma treatments. These treatments resulted in surface modifications, leading to changes in nanostructure, contact angle, electrochemical properties and protein adhesion in a plasma power and process gas dependent way. To evaluate the effect of the plasma-induced PEEK modifications on stem cell adhesion and differentiation, adipose tissue-derived mesenchymal stem cells (adMSC) were seeded on PEEK specimens. We demonstrated an increased adhesion, proliferation, and osteogenic differentiation of adMSC in contact to plasma-treated PEEK. In dependency on the process gas (oxygen or ammonia) and plasma power (between 10 and 200 W for 5 min), varying degrees of osteogenic differentiation were induced. When adMSC were grown on 10 and 50 W oxygen and ammonia plasma-treated PEEK substrates they exhibited a doubled mineralization degree relative to the original PEEK. Thus plasma treatment of PEEK specimens induced changes in surface chemistry and topography and supported osteogenic differentiation of adMSC in vitro. Therefore plasma treated PEEK holds perspective for contributing to osseointegration of dental and orthopedic load-bearing PEEK implants in vivo.

Photoreaction of a hydroxyalkyphenone with the membrane of polymersomes: a versatile method to generate semipermeable nanoreactors.

Block copolymer vesicles can be turned into nanoreactors when a catalyst is encapsulated in these hollow nanostructures. However the membranes of these polymersomes are most often impermeable to small organic molecules, while applications as nanoreactor, as artificial organelles, or as drug-delivery devices require an exchange of substances between the outside and the inside of polymersomes. Here, a simple and versatile method is presented to render polymersomes semipermeable. It does not require complex membrane proteins or pose requirements on the chemical nature of the polymers. Vesicles made from three different amphiphilic block copolymers (α,ω-hydroxy-end-capped poly(2-methyl-2-oxazoline)-block-poly(dimethylsiloxane)-block-poly(2-methyl-2-oxazoline) (PMOXA-b-PDMS-b-PMOXA), α,ω-acrylate-end-capped PMOXA-b-PDMS-b-PMOXA, and poly(ethylene oxide)-block-poly(butadiene) (PEO-b-PB)) were reacted with externally added 2-hydroxy-4'-2-(hydroxyethoxy)-2-methylpropiophenone under UV-irradiation. The photoreactive compound incorporated into the block copolymer membranes independently of their chemical nature or the presence of double bonds. This treatment of polymersomes resulted in substantial increase in permeability for organic compounds while not disturbing the size and the shape of the vesicles. Permeability was assessed by encapsulating horseradish peroxidase into vesicles and measuring the accessibility of substrates to the enzyme. The permeability of photoreacted polymersomes for ABTS, AEC, pyrogallol, and TMB was determined to be between 1.9 and 38.2 nm s(-1). It correlated with the hydrophobicity of the compounds. Moreover, fluorescent dyes were released at higher rates from permeabilized polymersomes compared to unmodified ones. The permeabilized nanoreactors retained their ability to protect encapsulated biocatalysts from degradation by proteases.