Apparatus and methods for conducting assays and high throughput screening

A method of treating a cell, comprising:

• (a) providing a microfluidic device comprising:
• (i) a main flow channel;
• (ii) a plurality of branch flow channels, each branch flow channel being in fluid communication with the main flow channel;
• (iii) a plurality of control channels;
• and
• (iv) a plurality of storage valves, wherein a pair of storage valves are operatively disposed with respect to each of the branch flow channels, and wherein, each of the storage valves comprises an elastomeric segment that separates one of the branch flow channels and one of the control channels and that is deflectable, into or retractable from the flow channel upon which the valve operates in response to an actuation force applied to the control channel, the storage valves of a pair being disposed with respect to one another such that when the elastomeric segment of each storage valve of the pair extends into the branch flow channel a holding space is formed between the segments in which one or more cells can be retained;
• (b) introducing a solution containing one or more cells into each of the branch flow channels;
• (c) actuating the storage valves within each of the branch flow channels to form the holding space to hold at least one of the cells, within the sample introduced into the branch flow channel;
• and
• (d) contacting the cell or cells within the holding space with a solution containing one or more assay agents.

A method for conducting an assay, comprising:

• (a) providing a microfluidic device comprising:
• (i) a main flow channel;
• (ii) a plurality of branch flow channels, each in fluid communication with the main flow channel and comprising a detection region;
• (iii) a plurality of control channels;
• and
• (iv) a plurality of valves operatively disposed with respect to the main flow channel and/or the plurality of branch flow channels to regulate flow of the first and second solutions therethrough, wherein each of the valves comprises one of the control channels and an elastomeric segment that is deflectable into or retractable from the main or branch flow channel upon which the valve operates in response to an actuation force applied to the control channel, the elastomeric segment when positioned in the flow channel restricting solution flow therethrough;
• (b) introducing a first assay solution into the main flow channel and a second assay solution into each of the plurality of branch flow channels;
• (c) actuating one or more of the valves to control flow of the first and second assay solutions through the main and branch flow channels, whereby the first and second assay solutions are brought into contact with one another to form an assay solution mixture;
• and
• (d) monitoring each of the assay solution mixtures for a desired property within the detection region.