Fine Structure of Bacterial Adhesion to the Epithelial Cell Membranes of the Filiform Papillae of Tongue and Palatine Mucosa of Rodents: A Morphometric, TEM, and HRSEM Study

Biological films adhering to the oral soft tissues: Structure, composition, and potential impact on taste perception

The role of free-flowing saliva in taste perception is increasingly recognized, but saliva is also present in the mouth as films intimately associated to soft or hard tissues. On mucosal surfaces, particularly on the tongue, the structure and composition of such films (including its microbial constitutive part) may play a particular role in the sense of taste due to their proximity with the taste anatomical structures. This review compiles the current knowledge on the structure of biological films adhering to oral mucosae and on their biochemical and microbiological composition, before presenting possible implications for taste perception. PRACTICAL APPLICATIONS: The understanding of the role of oral biological films on taste perception may provide new avenues of research and development for the industry or academia interested broadly in chemosensation.

Synergism between high hydrostatic pressure and glutaraldehyde for the inactivation of Staphylococcus aureus at moderate temperature

The sterilization of transplant and medical devices should be effective but not detrimental to the structural properties of the materials used. In this study, we examined the effectiveness of chemical and physical agents for inactivating Staphylococcus aureus, a gram-positive bacterium and important cause of infections and biofilm production. The treatment conditions in this work were chosen to facilitate their subsequent use with sensitive materials. The effects of temperature, high hydrostatic pressure, and glutaraldehyde disinfectant on the growth of two strains of S. aureus (ATCC 25923 and BEC 9393) were investigated individually and/or in combinations. A low concentration of glutaraldehyde (0.5 mM), high hydrostatic pressure (300 MPa for 10 min), and moderate temperature (50 °C), when used in combination, significantly potentiated the inactivation of both bacterial strains by > 8 orders of magnitude. Transmission electron microscopy revealed structural damage and changes in area that correlated with the use of pressure in the presence of glutaraldehyde at room temperature in both strains. Biofilm from strain ATCC 25923 was particularly susceptible to inactivation. The conditions used here provided effective sterilization that can be applied to sensitive surgical devices and biomaterials, with negligible damage. The use of this experimental approach to investigate other pathogens could lead to the adoption of this procedure for sterilizing sensitive materials.

The Associations between Biochemical and Microbiological Variables and Taste Differ in Whole Saliva and in the Film Lining the Tongue

The objective of this work was to investigate whether the biological film lining the tongue may play a role in taste perception. For that purpose, the tongue film and saliva of 21 healthy subjects were characterized, focusing on microorganisms and their main metabolic substrates and products. In parallel, taste sensitivity was evaluated using a test recently developed by our group, and the links between biological and sensory data were explored by a correlative approach. Saliva and tongue film differed significantly in biochemical composition (proportions of glucose, fructose, sucrose, and lactic, butyric, and acetic acids) and in microbiological profiles: compared to saliva, tongue film was characterized by significantly lower proportions of Bacteroidetes (p<0.001) and its main genus Prevotella (p<0.01) and significantly higher proportions of Firmicutes (p<0.01), Actinobacteria (p<0.001), and the genus Streptococcus (p<0.05). Generic taste sensitivity was linked to biological variables in the two compartments, but variables that appeared influent in saliva (flow, organic acids, proportion of Actinobacteria and Firmicutes) and in tongue film (sugars and proportions of Bacteroidetes) were not the same. This study points to two interesting areas in taste research: the oral microbiome and the specific characterization of the film lining the tongue.

Tuning Surface Chemistry of Polyetheretherketone by Gold Coating and Plasma Treatment

Polyetheretherketone (PEEK) has good chemical and biomechanical properties that are excellent for biomedical applications. However, PEEK exhibits hydrophobic and other surface characteristics which cause limited cell adhesion. We have investigated the potential of Ar plasma treatment for the formation of a nanostructured PEEK surface in order to enhance cell adhesion. The specific aim of this study was to reveal the effect of the interface of plasma-treated and gold-coated PEEK matrices on adhesion and spreading of mouse embryonic fibroblasts. The surface characteristics (polarity, surface chemistry, and structure) before and after treatment were evaluated by various experimental techniques (gravimetry, goniometry, X-ray photoelectron spectroscopy (XPS), and electrokinetic analysis). Further, atomic force microscopy (AFM) was employed to examine PEEK surface morphology and roughness. The biological response of cells towards nanostructured PEEK was evaluated in terms of cell adhesion, spreading, and proliferation. Detailed cell morphology was evaluated by scanning electron microscopy (SEM). Compared to plasma treatment, gold coating improved PEEK wettability. The XPS method showed a decrease in the carbon concentration with increasing time of plasma treatment. Cell adhesion determined on the interface between plasma-treated and gold-coated PEEK matrices was directly proportional to the thickness of a gold layer on a sample. Our results suggest that plasma treatment in a combination with gold coating could be used in biomedical applications requiring enhanced cell adhesion.

The interplay of plasma treatment and gold coating and ultra-high molecular weight polyethylene: On the cytocompatibility

We have investigated the application of Ar plasma for creation of nanostructured ultra high molecular weight polyethylene (PE) surface in order to enhance adhesion of mouse embryonic fibroblasts (L929). The aim of this study was to investigate the effect of the interface between plasma-treated and gold-coated PE on adhesion and spreading of cells. The surface properties of pristine samples and its modified counterparts were studied by different experimental techniques (gravimetry, goniometry and X-ray photoelectron spectroscopy (XPS), electrokinetic analysis), which were used for characterization of treated and sputtered layers, polarity and surface chemical structure, respectively. Further, atomic force microscopy (AFM) was employed to study the surface morphology and roughness. Biological responses of cells seeded on PE samples were evaluated in terms of cell adhesion, spreading, morphology and proliferation. Detailed cell morphology and intercellular connections were followed by scanning electron microscopy (SEM). As it was expected the thickness of a deposited gold film was an increasing function of the sputtering time. Despite the fact that plasma treatment proceeded in inert plasma, oxidized degradation products were formed on the PE surface which would contribute to increased hydrophilicity (wettability) of the plasma treated polymer. The XPS method showed a decrease in carbon concentration with increasing plasma treatment. Cell adhesion measured on the interface between plasma treated and gold coated PE was inversely proportional to the thickness of a gold layer on a sample.

Tailoring of PEEK bioactivity for improved cell interaction: plasma treatment in action

Despite the extensive use of polyetheretherketone (PEEK) in biomedical applications, information about cell adhesion on this biomaterial is limited.