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Jan 15, 2009 (Vol. 29, No. 2)

Microfluidics Makes Strides to Fulfill Promise

As the Field Grows and Matures, It Is Becoming an Essential Tool in Product Development

  • Enzymatic Assays

    Much of drug discovery focuses on finding inhibitors of enzyme targets such as kinases, phosphatases, and proteases. Caliper Life Sciences offers its Mobility Shift Assay to interrogate druggable enzymes. It combines the advantages of capillary electrophoresis with microfluidics technology for the direct measurement of substrate and product. 

    Raj Singh, Ph.D., director of assay R&D, reports that the basis of the technology is Caliper’s sipper chip. “Our mobility shift microfluidics assay technology monitors the modulation of enzyme activity by inhibitors using a ratiometric fluorescence readout of the substrate and product.  Basically, potent drugs produce a lower amount of the enzymatic product at a lower concentration than less potent ones. For example, kinase assays are not only analyzed on our LabChip EZ Reader, they also are rapidly profiled for selectivity and specificity against a panel of 200 plus enzymes. 

    “The assay components and compounds assembled in a microtiter well format are sipped into a 4- or 12-sipper chip via capillaries under vacuum. Reactions are separated by electrophoresis and signals measured by fluorescence in either endpoint or kinetic modes. The Mobility Shift Assay technology is designed for in vitro enzyme assays used in the drug discovery process. Even GPCR assays have been recently adapted to the Labchip format by utilizing the b-galactosidase enzyme fragment complementation technology commercialized by DiscoveRx as Pathhunter™.”

    Dr. Singh says one of the big advantages of the technology is that it allows multiple read-outs from the same microtiter well without using any ancillary reagent or terminating the reaction. “Other technologies often use different methods for different drug discovery targets. Because the microfluidics technology only needs nanoliters of sample, obtaining multiple read outs is possible. Also since assays are separation-based, the quality exceeds what is obtained in homogenous, well-based assays. High Z´ values, fewer false positives and negatives, as well as analytical quality reproducibility provide a high degree of reliability and accuracy.”

    A rapid and accurate diagnosis is critical for decision-making during a medical crisis or for devising appropriate treatments. Needing only small volumes and offering rapid turn-around times, microfluidic technologies are leading the pack for point-of-care-diagnostics.

    Biosite has developed protein array technologies that contain microcapillaries for controlling the flow of fluids in immunoassay processes. The protein array format uses several different microcapillary designs to control the contact of sample with reagents and to direct the flow of fluid throughout the protein array. For example, after a blood sample is added to the array, a special internal filter separates cells from plasma. Next a capillary directs the sample into a chamber that contains dried immunoassay reagents.

    After an incubation time that is determined by another microcapillary element of the array, the sample next flows down a capillary path and interacts with an antibody array. The interactions are detected in the company’s Triage® Meters that scan the array device with a laser diode.

    The field of microfluidics continues to grow and mature. Significant developments are emerging that promise to make microfluidics into an enabling technology that will become an essential tool in product development.

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