On-chip cell sorting system using thermoreversible gelation polymer

We have developed a microfabricated fluorescence-activated cell sorter system using laminar flow of thermoreversible gelation polymer (TGP). The glass sorter chip consists of microchannels with two inlets for sample and buffer solutions, and two outlets for collection and waste of the specimen. A biological specimen containing fluorescently labeled cells, is mixed with a solution containing a TGP. The laminar flow of the mixed solution and buffer solution are then introduced into the sorter chip. The fluorescently labeled target cells were detected with sensitive fluorescence microscopy. In the absence of a fluorescence signal, the laminar flow of the specimen is directed into the waste channel. Upon detection of a fluorescence signal from the target cells, the sol-gel transformation was locally induced by site-directed infrared laser irradiation for the flow switching and for allowing the fluorescent cells to be channeled into the collection reservoir. The flow switching time of 100 ms was achieved. Using this system, we have demonstrated the sorting of Escherichia coli cells expressing fluorescent proteins. These cells were found to be viable after extraction from the sorting system, indicating no damage to the cells.