Chemical cytometry on a picoliter-scale integrated microfluidic chip

Abstract

An integrated microfluidic device has been fabricated for analyzing the chemical contents of a single cell (chemical cytometry). The device is designed to accomplish four different functions: ( i ) cell handling, ( ii ) metering and delivering of chemical reagents, ( iii ) cell lysis and chemical derivatization, and ( iv ) separating derivatized compounds and detecting them by laser-induced fluorescence. These functions are accomplished with only two valves, formed by multilayer soft lithography. A new kind of three-state valve and a picopipette are described; these elements are crucial for minimizing the reaction volume and ensuring optimal shape of the channel for electrophoresis injection. By using these valves, a reaction volume of ≈70 pl is achieved for the lysis and derivitization of the contents of a single Jurkat T cell (≈10 μm diameter). As a demonstration of the use of this integrated microfluidic device, electropherograms of amino acids from individual Jurkat T cells are recorded and compared with those collected from a multiple-cell homogenate.