Cell based biological assay using microfluidics

Abstract

A microfluidic device has been designed to measure and manipulate microdroplets, in which protein expression is induced in single cells. The device exploits the permeation of water through poly (dimethylsiloxane) (PDMS) in order to keep the concentration of solutes in aqueous picoliter volume microdroplets stored in wells. The device operates by first creating droplets of the water/solute mixture. Next, droplets are transported down channels and then guided into storage wells using surface tension forces. Finally, the solute concentration of each stored droplet is maintained by chemical potential in a reservoir that is separated from the droplets by a thin layer of PDMS through which water, but not the solutes, permeates. We coexpressed two target proteins, alkaline phosphatase (AP) [1] and red fluorescent protein (mRFP1) [2], in single cells while they have been encapsulated in microdroplets. We interrogated the enzymatic activity of AP and the expression of mRFP1 by following the fluorescence of stored droplets.