Electrophysiological sorting of pluripotent stem cell-derived cardiomyocytes in a microfluidic platform

We are developing a microdevice for label-free cell sorting which sorts stem cells and their differentiated progeny based on their response to electrical stimulation. Specifically, we are interested in purifying ventricular-like cardiomyo-cytes from induced pluripotent stem cell (iPSC) derived populations for cardiac tissue replacement therapies. Electrophy-siological measurements are commonly used to identify subpopulations of electrically-excitable cells and to determine the degree to which stem cells have differentiated into these cell types. However, there is currently no way to sort cells based on electrophysiological parameters. Label-free, non-genetic cell purification methods are ideal for tissue replacement therapies because labeling molecules and antibodies may be toxic to the patient or interfere with the integration of the graft tissue. Furthermore, for certain cell types, such as cardiomyocytes, there are no reliable molecular surface markers available. Our recent efforts have focused on developing a microsystem and instrumentation to measure extracellular field potentials (FPs) from cells, and we have made a number of technical innovations to reduce feedthrough stimulus artifact and enhance FP signal amplitude. We are able to distinguish clusters of iPSC-derived cardiomyocytes from undifferen-tiated embryoid bodies with very good contrast. Our eventual goal is to develop an automated system capable of analyzing and sorting individual cells.