A thermodynamic theory of short-term cell adhesion in vitro has been developed based on a physical model of the initial formation of a cell-substrate interface. The special role of material and cell membrane wetting properties in cell adhesion was elucidated and monitored as a function of surfactant concentration. Surfactant effects on adhesion of an ordinary non-ionic detergent (Tween-80) and a complex protein mixture (fetal bovine serum) were shown to be identical in this regard, illustrating the importance of proteins as biosurfactants and supporting the general applicability of the model. Theory provides a means of calculating reversible work of adhesion, estimation of a term proportional to cell-substrate contact area, and a method of determining a parameter related to cell wetting tension that does not require special manipulations which might desiccate or denature delicate cell membranes. Semiquantitative agreement between predicted and experimentally-measured cell adhesion obtained for three different cell types (MDCK, RBL-1, and HCT-15) in two different liquid phase compositions of surfactants (Tween-80 and fetal bovine serum) supports concepts and approximations utilized in development of theory. Cell-substrate contact areas were largest for wettable surfaces treated with ionizing corona or plasma discharges and smallest for hydrophobic materials for each cell type studied. Contact area for the continuous dog-kidney cell line MDCK was larger than that of either the leukemic blood cell RBL-1 or the anaplastic human colon cell HCT-15.
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