Method for conducting reactions involving biological molecules in plugs in a microfluidic system

A method of forming a plurality of plugs and conducting a reaction in at least one thereof, the method comprising the steps of:

• providing a microfluidic device comprising a substrate having at least a first channel and a second channel intersecting each other at a plug-forming junction;
• introducing to the first channel of the microfluidic device a stream of a first plug fluid containing at least one biological molecule and introducing to the first channel a stream of a second plug fluid containing one or more reagents for conducting the reaction with the at least one biological molecule of the first plug fluid;
• continuously coflowing the stream of the first plug fluid and the stream of the second plug fluid with one another and through the first channel of the microfluidic device towards the plug-forming junction such that at least one biological molecule of the first plug fluid and the one or more reagents, of the second plug fluid, for conducting a reaction with the at least one biological molecule coflow with one another prior to contact with a carrier fluid and prior to plug formation;
• continuously flowing a stream of a carrier fluid comprising an oil immiscible with the streams of first and second plug fluids through the second channel of the microfluidic device towards the plug-forming junction, wherein the carrier fluid comprises a fluorosurfactant that comprises an oligoethylene glycol (OEG) terminal end to which an OEG is linked;
• forming a plurality of plugs comprising a portion of the coflowing and streaming first and second plug fluids containing the at least one biological molecule and the one or more reagents, respectively, by partitioning the continuously coflowing streams of first and second plug fluids with the continuously flowing stream of carrier fluid at the plug-forming junction of the first and second channels, each of the plurality of plugs being substantially surrounded by the carrier fluid, wherein at least one of the plurality of plugs comprises the at least one biological molecule and the one or more reagents for conducting the reaction with the at least one biological molecule;
• and
• providing conditions suitable for a polymerase chain reaction (PCR) to occur in the at least one plug involving the at least one biological molecule and the one or more reagents to form a PCR product.