Adhesion, cell attachment assay

Different assays have been developed to qualitatively and quantitatively study cell adhesion. Usually, these assays probe the ability of cells to remain attached to an adhesive substrate when exposed to a certain detachment force. They can be classified into single-cell assays and bulk assays that analyze the average behavior of large cellular populations (an overview is given in Ref. 59). 

Cell adhesion. For most applications the adhesion of cells is of fnndamental interest being the initial event of cell attachment. A simple method to quantify adherent cells is to incnbate cells over a snrface for a period of time snbsequently followed by the detachment of loosely adherent cells by gently washing the surface. Remaining cells can be labeled by flnorescent dyes and quantihed using flnorescent measnrements. Cell adhesion assays are also freqnently used to assess monocyte or platelet adhesion on polymeric snrfaces [215, 216]. In this context Hezi-Yamit et al. [217] did show that polymer hydrophilicity should be considered as a parameter to assess the biocompatibility of polymer surfaces. They showed that hydrophobic polymers such as PBMA or SIBS promote the adhesion of inflammatory activated monocytes while more hydrophilic polymers (e.g. PC (Phosphorylcholine) polymer) lead to less pro-inflammatory responses. 

Figure 8. Results from fibroblast adhesion on starch-based hydrogel. Top - microscopic images showing cell morphology and spread on hydrogel treated with recombinant proteins (SBM or RGD-SBM) and control hydrogel without recombinant protein and polystyrene plate. Bottom - results from viability assay of cell attached to the hydrogels or polystyrene plate [adapted from 192].

The growth rate of mammalian cells in the presence of Cell-Tak adhesive was assayed to evaluate any potential adverse effects caused by this protein. Bovine corneal endothelial cell (BCE) stocks were grown to confluency in MEM plus 15% calf serum, trypsinized, and washed several times by centrifugation on MEM. Suspensions (5 x 104 cells/mL) were seeded onto untreated 35-mm dishes (control) and dishes with Cell-Tak protein (5 fig/cm2) in MEM with 15% calf serum. At various time points during the incubation at 37 °C with 5% CO2, triplicate plates were removed. The attached cells were then trypsinized from the surface, washed, and counted in a hemacytometer. 

Tumor cells that have the ability to attach to some defined substrates with the same apparent efficiency, as measured by the adhesion assays described above, may nonetheless adhere to the different substrates not with the same strength. Therefore, even though each substrate appears to be able to support cell adhesion, the tenaciousness characterizing each interaction may be different, and it may have an influence on the metastatic ability of tumor cells (Leung-Tack et al., 1988). 

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