Microfluidic device performs 1024 click-chemistry reactions in parallel

This microfluidic device handles 1024 click-chemistry reactions. (Courtesy of UCLA)
View larger image.

In situ click chemistry is a target-guided synthetic method used to produce enzyme inhibitors, which can then be screened for drug leads. Click-chemistry reactions are often performed in 96 well plates, but a new microfluidic device can perform 1024 reactions in parallel with off-line identification of hits.

Researchers from the University of California Los Angeles (UCLA), California State University, Siemens Medical Solutions USA, Inc., and Wuhan University (China) developed the device. They previously created a microfluidic device that could handle 32 click-chemistry reactions, but they wanted to improve on it with a platform that could multiplex more reactions with greater throughput and sensitivity.

For click chemistry, microfluidic devices offer several advantages over well plates. The former platform consumes less reagent and target protein, performs faster screening, and allows easier automation of the reactions and subsequent hit analysis.

The researchers created a device with a total reaction volume of ~400 nanoliters (nL). A pair of microfluidic multiplexers regulates duplicate inlets for 16 reagents, which are mixed by a 150 nL rotary mixer. A 150 nL serpentine channel provides any additional phosphate buffered saline needed to reach the 400 nL reaction volume or to manipulate or mix reagents. Several replaceable 20-centimeter-long poly(tetrafluoroethylene) tubes that the researchers attached to the chip’s outlet hold the resulting 1024 reaction-mixture slugs; these are then screened for hits with ESI MS.

Because polar (charged) reagents might interfere with direct ESI MS analysis, the researchers incorporated a reversed-phase clean-up step to remove them from the reaction mixtures. This increased the sensitivity and throughput of hit identification, says Hsian-Rong Tseng, who was part of the UCLA team. The researchers also incorporated multiple-reaction monitoring.

The improved design reduced preparation time for one reaction to 17 seconds, a big improvement from the 1.0 minute (min) required for their previous device. The analysis improvements allowed hit identification at a rate of 15 seconds per reaction (2 min for 8 samples), while the first-generation device required 40 min per reaction.

Tseng says that the device is restricted to screening reactions in aqueous solutions because it uses PDMS materials, which can be susceptible to organic solvents or harsh chemicals. As for the future, he adds that the researchers plan to automate the analysis of the reaction results, which could greatly increase throughput for enzyme inhibitor discovery. (Lab Chip 2009, DOI 10.1021/b907430a)