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Microfluidic device combining hydrodynamic and dielectrophoretic trapping for the controlled contact between single micro-sized objects and application to adhesion assays

The understanding of cell-cell and cell-matrix interactions via receptor and ligand binding relies on our ability to study the very first events of their contact. Of particular interest is the interaction between a T cell receptor and its cognate peptide-major histocompatibility complex. Indeed analyzing their binding kinetics and cellular avidity in large-scale low-cost and fast cell sorting would largely facilitate the access to cell-based cancer immunotherapies. We thus propose a microfluidic tool able to independently control two types of micro-sized objects, put them in contact for a defined time and probe their adhesion state. The device consists in hydrodynamic traps holding the first type of cells from below against the fluid flow, and a dielectrophoretic system to force the second type of object to remain in contact to the first one. First the device is validated by performing an adhesion frequency assay between fibroblasts and fibronectin coated bead. Then, a study is conducted on the modification of the cellular environment to match the dielectrophoretic technology requirements without modifying the cells viability and interaction functionalities. Finally, we demonstrate the capability of the developed device to put cancer cells and a population of T cells in contact and show the discrimination between specific and non specific interactions based on pairs lifetime.