Search

• Biofilm and cell monolayer adhesion are measured via the laser spallation technique. • Smooth and roughened dental implant-mimicking titanium surfaces are investigated. • Surface roughness increases cell adhesion but does not alter the adhesion of biofilms. • An Adhesion Index is developed to directly quantify the adhesive competition between bacteria and cells on an implant surface. The aims of this study are to quantify the adhesion strength differential between an oral bacterial biofilm and an osteoblast-like cell monolayer to a dental implant-simulant surface and develop a metric that quantifies the biocompatible effect of implant surfaces on bacterial and cell adhesion. High-amplitude short-duration stress waves generated by laser pulse absorption are used to spall bacteria and cells from titanium substrates. By carefully controlling laser fluence and calibration of laser fluence with applied stress, the adhesion difference between Streptococcus mutans biofilms and MG 63 osteoblast-like cell monolayers on smooth and rough titanium substrates is obtained. The ratio of cell adhesion strength to biofilm adhesion strength (i.e., Adhesion Index) is determined as a nondimensionalized parameter for biocompatibility assessment. Adhesion strength of 143 MPa, with a 95% C.I. (114, 176), is measured for MG 63 cells on smooth titanium and 292 MPa, with a 95% C.I. (267, 306), on roughened titanium. Adhesion strength for S. mutans on smooth titanium is 320 MPa, with a 95% C.I. (304, 333), and remained relatively constant at 332 MPa, with a 95% C.I. (324, 343), on roughened titanium. The calculated Adhesion Index for smooth titanium is 0.451, with a 95% C.I. (0.267, 0.622), which increased to 0.876, with a 95% C.I. (0.780, 0.932), on roughened titanium. The laser spallation technique provides a platform to examine the tradeoffs of adhesion modulators on both biofilm and cell adhesion. This tradeoff is characterized by the Adhesion Index, which is proposed to aid biocompatibility screening and could help improve implantation outcomes. The Adhesion Index is implemented to determine surface factors that promote favorable adhesion of cells greater than biofilms. Here, an Adhesion Index ≫ 1 suggests favorable biocompatibility. [ABSTRACT FROM AUTHOR]

Abstract With the growing interest in probiotic microorganisms based on their well established immense health benefits, the present investigation was aimed to assess the adhesion potential and safety of probiotic Lactobacillus rhamnosus MTCC- 5897 (LR) before it can be put into a probiotic formulations. L. rhamnosus showed an adhesion index of 166.7 ± 11, which was further confirmed by scanning electron microscopy and relative expression of mucus binding protein (Mub) and mucus adhesion promoting protein (Map-A) genes. In vitro safety assessment by tetrazolium dye reduction, neutral red and lactate dehydrogenase (LDH) release assays revealed unchanged metabolic activity of Caco-2 cells even when incubated with L. rhamnosus ranged between 106-1010 cfu/mL for 24 h. Similarly, a moderate increase in bile salt hydrolase (bsh) expression (6.84 ± 0.73 and 3.42 ± 0.39 folds in 1% and 3% bile medium respectively) further proved its safety towards normal lipid digestion and absorption. Moreover, L. rhamnosus feeding to mice (107, 109, 1011 and 1013 cfu/animal/d) repetitively for 28 days revealed no adverse effects on parameters of general animal health status including body weight, organ indices, plasma glucose, liver malondialdehyde (MDA), serum aspartate amino transaminase (AST), cholesterol, triglycerides, high-density lipoprotein (HDL). Similarly, significant (p ≤ 0.05) reduced activities of serum alanine amino transaminase (ALT) and LDH on continuous probiotic feeding were also indicative of normal liver/kidney functions as they were in normal range for mice. Further, insignificant changes in macrophage chemoattractant protein (MCP-1) in intestinal fluid irrespective of bacterial dose fed along with significant reduction (p ≤ 0.05) of tumor necrosis factor-α (TNF-α) at much higher dose (1013 cfu/animal/d) also confirmed safe response of probotic L.rhamnosus against inflammation. To conclude, the results obtained under in vitro and in vivo studies has established the Lactobacillus rhamnosus as safe and non-toxic to weaning mice as well as human epithelial cells and thus may be used as a safe food additive. Highlights • L. rhamnosus MTCC-5897 has sufficient adhesion capability to intestinal cells. • In vitro assays established L. rhamnosus MTCC-5897 as non-toxic to intestinal cells. • Feeding of L. rhamnosus MTCC-5897 was found safe to mice weanlings. [ABSTRACT FROM AUTHOR]

The paper describes a theoretical study of adhesive friction at elastic–plastic contact of rough surfaces based on n-point asperity model. Well defined adhesion index and plasticity index are used to study the prospective situations arising out of variation in load, material properties, and surface roughness. Results are obtained for the behavior of friction force, applied load, and coefficient of friction for different combinations of adhesion index, plasticity index and mean separation of surfaces. The results obtained are in line with earlier models. It is observed that the tensile load required in maintaining a separation increases with increase in adhesion effect and extent of plastic deformation. Also coefficient of friction increases with adhesion effect.

The work analyses the technical evaluation process of the suspension system for vehicles that have been adapted to natural-gas-fuelled engines from power light-duty gasoline, and diesel vehicles; this evaluation is done through a mechanical review established by national regulations. The development of this analysis is focused on establishing the relationship between the natural-gas-fuelled equipment and the dynamic effect caused by the extra-weight, according to two measuring criteria that determine the safety and driving comfort, these are: (i) tire-road adhesion index; and (ii) tire excitation phase angle. The paper also proposes new elements that can be added to the current national regulations and that are currently applied to assess the suspension of natural gas vehicles, recorded using a test standard benchmark for the evaluation of the suspension.

Aims: To investigate the adhesion of lactobacilli and their subsequent competitive exclusion ability against pathogens. Methods and Results: Four species of putative probiotic lactobacilli were studied for their adhesion abilities. First, the adhesion to Caco-2 cells was examined by light and electron microscopy. The four species were then labelled by [methyl-3H] thymidine and their adhesion to porcine intestinal mucus was determined by radioactivity. The tested lactobacilli showed best adhesion on ileal mucus compared with duodenal and jujenal mucus. Oxidative compound pre-treatment (NaIO3 and NaIO4) dramatically decreased the adhesion of the lactobacilli to mucus. Pre-treating mucus with proteolytic enzymes (proteinase K and trypsin) resulted in the increase of adhesion in Lactobacillus serotype Reuteri I2021, but the results in the other species were variable. Lactobacillus serotype Fermentum I5007 showed greatest adhesion potential and exerted the best competitive exclusion against Salmonella and Escherichia. Conclusions: Adhesion ability in lactobacilli is species-specific. Lactobacilli with higher adhesion index have better competitive exclusion ability. Significance and Impact of the Study: This study suggests that there is a positive correlation between adhesion and competitive exclusion ability of lactobacilli. Additionally, the in vitro adhesion assay is a feasible way to screen unknown lactobacilli, potentially for future industrial applications. [ABSTRACT FROM AUTHOR]

Corynebacterium diphtheriae strains displayed different degrees of attachment to HEp-2 cell monolayers with two distinct adherence patterns, termed localised (LA) and diffuse (DA). The LA phenotype predominated over the DA phenotype. The non-sucrose fermenting strains expressing DA pattern adhered mostly with high index values (≥10 bact/cell). Low adhesion index (<10 bact/cell) was mainly observed among sucrose fermenting strains. The fluorescein isothiocyanate (FITC)-labelled phalloidin assay (fluorescent-actin staining test) showed positive results for microorganisms of both LA and DA phenotypes. The FITC-labelled C. diphtheriae non-fimbrial surface proteins 67–72p interacted directly with HEp-2 cell membranes. Therefore, toxigenic C. diphtheriae exhibited LA and DA adherence patterns and ability to induce actin polymerisation. The experimental evidences also pointed to 67–72p as putative adhesins of C. diphtheriae to HEp-2 cells. [Copyright &y& Elsevier]