Single-cell quantitative analysis of DNA incorporation and protein expression in microwells

Conventional biochemical assays are performed via an averaging procedure with the lysate of a large number of target cells; however, the averaged data lose information regarding the heterogeneity of individual cells. For quantitative assay of single cells, it is necessary to isolate single cells, extract cellular components and detect extremely small amounts of molecules from the individual cells. We developed new system combining a microfabricated lab-on-chip device and fluorescence correlation spectroscopy. The system features a simple protocol to isolate single-cells and detect small amounts of specific fluorescent molecules extracted from a single cell. Our results indicate that numbers of transfected DNA molecules were rather equal for each single cell; however, the expression rate of protein varied in each single cell.