(236g) Film Trapping Technique And Interaction With Another Interface Of Biological Or Fluid Interfaces, Covered With Non-Ionic Stabilizers

A method (FTT) for controlling the contact of cell-surface receptors with immobilized ligands has been developed by trapping cells in an asymmetric liquid film. Ligands adsorbed to the liquid-solid interface are forced into increasingly tighter contact with the cells by controlling the degree of thinning. This allowed examining the time course of Calcium mobilization in T cells upon activation with anti-CD3 antibody at different dilutions and ionic strengths. The APC-T cell contact depends on the biophysical forces between cells: specific bonds between two cells, nonspecific repulsive (electrostatic, steric, and hydration) and attractive forces (van der Waals and hydrophobic). Our method allows imposing a known, uniform external force bringing ligands into controlled contact with cell surface receptors. Because of the strong cell deformability another method was also developed (FTT-gentle), which allows exerting virtually zero capillary pressures by suitably adjusting the wettability and the sharpness of the edge of the capillary.The entrapped cells are illuminated by monochromatic light, creating interference rings. The latter are used to reconstruct the cell profile and calculate the pressure on the cell surface. Murine CD4+ T cell hybridomas, loaded with a calcium sensitive fluorescent dye were added to monitor the intracellular free calcium levels using fluorescence microscopy. The FTT method was applied also to films with globular proteins (GP), adsorbed at air/water (A/W) and oil/water (O/W) interfaces. To allow more quantitative data interpretation this was combined with studies of the surface equations of state of adsorbed and spread layers of GP, allowing precise determination of the molecular state of GP at the interface. A new theory was developed for the interaction force of a surface covered with adsorbed fluctuating non-ionic species with another surface (solid or fluid)-this is a model for interaction between biological cells or between bubbles and drops covered with surfactant molecules, particles or GP. The theory was tested by measuring the life time and the disjoining pressure of thin films stabilized by these species and by FTT determination of the critical pressure for collapse of such bubbles and drops.