3D Microstructures Array Single-cell-based DEP Chip for Studying Apoptosis of U937 & A431 Cells

This study presents the design, simulation, fabrication and preliminary results of a cell trap device for detecting the early stage of apoptosis, PS (phosph-atidylserine) exposure, under single-cell resolution. The structure of biochip is consisted of ITO top electrode, PDMS flow chamber, bottom electrode array and SU-8 3D microstructure array. In order to achieve single-cell resolution, we utilize the excimer laser micromachining technique to simultaneously fabricate a chess-type bottom electrode array and a bowl-type 3D microstructure array, which design not only constructs a nonuniform electric field for trapping cells in the flow chamber by dielectrophoresis (DEP), but also enhances the positioning and immobilization of trapped cells. In addition, the optimal electrode width based on the simulation results is 30 mum for a cell size in the range of 15~20 mum such as U937 (Human histiocytic lymphoma) and A431 (Human epidermoid carcinoma) cancer cells. By using this DEP chip, we can study the physiological change of apoptosis in one single cell instead of whole cell population. As the preliminary results, 25 mum latex beads can be successfully trapped with single-bead resolution in a short time. Furthermore, the time- and dose-dependent manners for A431/As2O3 and U937/Taol are also confirmed by agarose gel electrophoresis and flow cytometry but not on-chip monitoring. We are still working on real-time and on-chip study for development of a high-throughput drug screening with single-cell level