Kinase activity assay gets microfluidic platform

Schematic of the kinase activity assay based on nanofluidic preconcentration. (GND = ground)
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Researchers need data on the kinases involved in complex cell signaling pathways, but current methods, from MS to affinity-based techniques, have one drawback or another. So Jongyoon Han and colleagues at the Massachusetts Institute of Technology have created a micro- and nanofluidic device that measures the activity of kinases from a small number of cells, using standard cell-culture and lysis methods. The device can also be integrated with other microfluidic-based cell assays.

Han and colleagues weren’t the first to develop a miniaturized device for enzymatic assays, but they are the first to tackle low-abundance kinase activities. A key component of their device is a nanofluidic preconcentrator that concentrates proteins by electrokinetic trapping in a specific region of the microfluidic chip while depleting ions. The kinase activity is then monitored by measuring the fluorescence produced from a special substrate. The current device tracks kinase activities directly from cell lysates—previous versions could only handle assays in standard buffers, not physiological samples.

The investigators demonstrated the device’s ability to monitor two important kinases, MK2 and PKA, from a sample size as small as 5 cells. In the microfluidic format, the reaction velocity was increased by 25-fold and the assay’s sensitivity enhanced by 65-fold. The assay time went from ~1 hour to <10 minutes. Han and colleagues suggested that their device could be a generic and important tool for single-cell diagnostics and systems biology studies if it were optimized for and integrated with cell-culture microdevices. (J. Am. Chem. Soc. 2009, DOI 10.1021/ja902594f)