New theory and observations of cell adhesion

Abstract

Over the years, attempts have been made to measure cell adhesion by several techniques, including, most recently, laser tweezers. Such tests have been used to interpret molecular theories of cell attachment and aggregation. However, the connection between adhering cells and molecular interactions is not fully understood. Here we define a new definition of cell adhesion which is exact and absolute at low cell concentrations. The idea is based on the statistical mechanics argument that particle bonding is directly related to the number of doublets existing in an ensemble. The theory is extended by computer modelling to high cell volume fractions. The benefit of this new theory is that it can be used in conjunction with cell counting machines, such as the Coulter counter, to obtain adhesion parameters directly, without applying any forces to the cells themselves. Experiments fitted the theory for human cells. The theory was also tested by using surface molecular treatments to alter the adhesive character of the cell suspension. Glutaraldehyde reduced adhesion, whereas dextran and fibronection increased adhesion of the red cells.

van der Waals forces influencing adhesion of cells

“…Taking the ratio of doublets to singlets, the gradient (N 2 /N 1 )w was obtained. The effect of glutaraldehyde in reducing adhesion was noted, while fibronectin gave a slight increase in the gradient figure 5 [9]. Horse and rat erythrocytes were then tested in the same way and shown to give significantly higher adhesion.…”

“…The conclusion of this argument is that a plot of doublet to singlet ratio versus particle volume fraction should yield a straight line passing through the origin. The gradient of the line is a measure of the adhesion which depends on range and energy of the interactions [9]. Thus a high gradient signifies high adhesion and a low gradient low adhesion.…”

“…The approaching sphere travels at constant speed, is accelerated into the potential well, reflects rigidly on contact, and then is decelerated as the particles move apart. Stainton [9,20] solved this problem to predict the number of doublets in a suspension. The result is that the ratio of doublets to singlets N 2 /N 1 is proportional to the volume fraction f of the cells and depends on the range l and the energy 1 of the well Figure 3.…”

“…Cells which float freely around the body without adhering strongly to other structures, for example red blood cells (erythrocytes), may possibly be described through these weak van der Waals adhesive forces alone, because their attractions are comparable to Brownian impulses, very much weaker than those measured by atomic force microscopy (AFM) and other conventional adhesion measurements [9], also much weaker than chemical bonds.…”

Biomechanical and Physiological Conditions Influence Erythrocytes - Erythrocyte Adhesion. An in vitro Study

“…Erythrocytes adhesion may be described through weak van der Waals adhesive forces alone which is much weaker than chemical bonds (Kendall, Liang, & Stainton, 1998).…”