Cell Adhesion Force Measurements

It could be shown that the adhesion force also depended on the contact time between the cantilever and the implant surface. Longer adhesion times led to higher adhesion forces (Fig. 11.9, lower graph). This fact can be discussed as a time limitation on the bond formation between the individual ligand-receptor pairs and is in agreement with the pubhshed Hterature [38]. 

Cell-adsorptive coatings of PTFE with laminin, coUagen IV, and Bbronectin have been described in the Hterature to improve the growth of endothehal cells on vascular implants, but these methods did not show satisfactory results when ap-pHed to vessels with a small diameter. 

4 fibronectin 5 collagen IV adhesion time 2 s. Lower graph Dependence of calculated adhesion forces between the Min3-modified PTFE surface and the cantilever-attached EC on the contact time (between 0.1 and 60s). The adhesion force increased from 240 pN (0.1 s contact) to 1112 pN (60 s contact). 

This work was supported financially by the interdisciplinary research program Biologically Composed Materials and Systems funded by the Departments of Education, Culture, and Science of the Saarland and Aesculap AG (Tuthngen). We also thank the Ponds der Chemischen Industrie for financial support. U.B. is grateful to the Stiftung Deutscher Naturforscher Leopoldina (BMBF/LPD-9901/8-6) for financial support. Special thanks go to Prof Dr. K.J. Neis and his team from the Frauenklinik of the Caritas Khnik St Theresia, Saarbriicken, for the supply of umbilical cords. 

Goormastic, M., Cosgrove, D.M., Vein graft disease the clinical impact of stenoses in saphenous vein bypass grafts to coronary arteries. J. Thorac. Cardiovasc. 

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Dammer, U., Popescu, O., Wagner, P., Anselmetti, D., Giintherodt, H.-J., and Misevic, G.N. (1995) Binding strength between cell adhesion proteoglycans measured by atomic force microscopy. Science 267, 1173-1175. 

D. P. Das, Liquid water-droplet adhesion-force measurements on fresh and aged fuel-cell gas-diffusion layers,/. Electrochem. Soc., 159, B489-B496 (2012). 

This expression was derived by Bell (1978), who used Kramers theory to show that bond lifetime ean be shortened by an applied force in processes such as cell adhesion. Although Eq. (3.2) is quite useful, it is in practice limited, most notably by the fact that it assumes that xp is constant. Typically, measurements of force dependency are made under conditions in which force changes with time, and it is likely that the position of the transition state will move as the shape of the potential surface is perturbed by an applied force (Evans and Ritchie 1997 Hummer and Szabo 2003). Theoretical and empirical treatments of various cases have been put forth in the hterature, but they are outside the scope of this chapter and will not be reviewed here. 

Figure 12 Combination of dielectrophoretic field cage (DFC) and optical tweezers (OT) for the measurement of bead-cell adhesion (A) 4.1-(xm polystyrene particle trapped with laser tweezers (right) in contact with T-lymphoma cell ( — 1 5 pm in diameter). Cell and bead were brought into contact. The time for stable adhesion was measured. (B) Schematic representation of the experimental system used to measure the adhesion forces between bead and cell with the cell trapped in a DFC and the bead trapped in the laser focus of the OT. (C) Probing different surface regions of the cell for bead-cell adhesion (five beads are attached to a single cell). (Reprinted from Ref. 91 with permission.)...

Bigelow JC,NabeshimaY, Kataoka K, Giddings JC (1991) Separation of cells and measurement of surface adhesion forces. In Compala DS, Todd P (eds) ACS Symp Ser. American Chemical Society, Washington, DC, p 146... 

Benoit, M., Gabriel, D., Gerisch, G.t., and Gaub, H.E. (2000). Discrete interactions in cell adhesion measured by single-molecule force spectroscopy. Nat. Cell Biol, 2, 313 317. 

This basic assay is susceptible to be modified in order to measure the ability of adherent cells to withstand increasing shear forces, which can be obtained by increasing the rate of mixing. Using this approach, the strength of cell adhesion to different substrates, or the strength of adhesion of different cell types to the same substrate, can be compared. 

Several methods have been developed for the experimental investigation of the process and for the quantitative description of mucoadhesion. These methods can be classified into the following groups i) methods based on measuring viscosity [99-102], ii) separation of the substrate and the adhesive with microscales based on horizontal or vertical force measurement [94,95,103-105], the most up to-date means of which is the so-called texture analyser [106], iii) in vitro or in vivo cell culture examinations [107-109], and iv) animal experiments [94,105,110]. 

A Quantitative Measurement of Adhesion Force between Cell Adhesion... 

Dictyostelium has been shown thus far to only have relatively weak contacts with the substratum. Observations by interference reflection microscopy show that highly chemotactic Dictyostelium cells have relatively small areas of contact with the substratum [193, 231]. They do not demonstrate the focal contacts that are seen with mesenchymal cells. The contact areas with the substratum do not show focal accumulations of cytoskeletal proteins, consistent with the lack of focal contacts. Flow force measurements of cell adhesion and detachment show that mutations in cytoskeletal proteins can reduce the adhesion strength [55, 161, 208, 221]. Dictyostelium cells can form eupodia on their dorsal surfaces when in contact with agarose on that surface [74, 75]. These structures may represent more localized adhesion sites, which are present when the appropriate substratum is available. In addition, during aggregation, chemotactic responses may be modified by cell-cell adhesion. 

Kong, H. J., Polte, T. R., Alsberg, E. and Mooney, D. J. FRET measurements of cell-traction forces and nano-scale clustering of adhesion ligands varied by substrate stiffness. Proc Natl Acad Sci USA 102, 4300-4305, 2005. 

Sheng, X. X., Ting, Y. R, and Pehkonen, S. O. 2007. Force measurements of bacterial adhesion on metals using a cell probe atomic force microscope, / Colloid Interface Sci 310,661-669. 

Alternatively to force-based approaches, cell adhesion can be quantified by measuring the intersurface distance between the cell and a planar transparent substrate (Fig. 4.30). Reflection interference contrast microscopy (RICM) is ideally suited for studying cell adhesion characteristics and dynamics in aqueous environment, as it allows for nanometer precise determination of intersurface distances with milliseconds time resolution [62]. It has the added... 

Hilal et al. [30] used AFM, in conjunction with a colloid probe, coated colloid probe, and cell probe techniques, to measure directly the adhesive force between two different UF membranes and a polystyrene sphere (diameter 11 jim), protein bovine serum albumin (BSA), and a yeast cell. These two membranes were ES 404 and XP 117 mentioned above (Table 7.1). The experiments were performed in 10 M NaCl solution. It was reported that the adhesive force of the polystyrene, the protein, and the cell system on the ES 404 membrane was greater than that on the XP 117 membrane. The relatively high affinity of protein for synthetic membrane surfaces was also observed. 

Yet the observation and measurement of cell adhesion are difficult because the cells have small diameters, between 1-10 pm, and the adhesion force is generally low, typically 0.1-100 nN. Usually, cell adhesion must be studied in a microscope. Attachment of cells may then be observed in relation to the chemical environment, and the cells may be pulled apart and sensed by various techniques including direct mechanical probing, shearing with a flow, or cytometry (cell counting) to determine the adhesion quantitatively. 

AFM characterization of the surface wettability of hemp fibre was reported by [41]. These images detailed the rough primary cell wall, which is characteristic of the hemp fibre. The fibres showed lower adhesion force and were presumably hydrophobic. Surface roughness averages of the fibre samples were measured to be between 10 and 20 nm on 1 mm areas, which were significantly rougher than the... 

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