Lab-on-a-Chip Promises Biochemical Diagnostics

Lab-on-a-chip technologies are attractive as they require fewer reagents, have lower detection limits, allow for parallel analyses, and can have a smaller footprint.

Miniaturized laboratory-on-chip systems promise rapid, sensitive, and multiplexed detection of biological samples for medical diagnostics, and high-throughput screening.

Scientists at the University of Illinois (Urbana, IL USA) used microfabrication techniques and incorporated a unique design of transistor-based heating, for further advancing the use of silicon transistor and electronics into chemistry and biology for point-of-care diagnostics.

The approach performs localized heating of individual subnanoliter droplets that can allow for new applications that require parallel, time-and space-multiplex reactions on a single integrated circuit. Within miniaturized laboratory-on-chips, static and dynamic droplets of fluids in different immiscible media have been used as individual vessels to perform biochemical reactions and confine the products.

By using microfabrication techniques and incorporating the unique design of transistor-based heating with individual reaction volumes, “laboratory-on-a-chip” technologies can be scaled down to “laboratory-on-a-transistor” technologies as sensor/heater hybrids that could be used for point-of-care diagnostics.

Rashid Bashir, PhD, a professor at the University of Illinois said, “We have demonstrated that single stranded DNA (ssDNA) probe molecules can be placed on heaters in solution, dried, and then rehydrated by ssDNA target molecules in droplets for hybridization and detection. This platform enables many applications in droplets including hybridization of low copy number DNA molecules, lysing of single cells, interrogation of ligand-receptor interactions, and rapid temperature cycling for amplification of DNA molecules. Notably, our miniaturized heater could also function as dual heater/sensor elements, as these silicon-on-insulator nanowire or nanoribbon structures have been used to detect DNA, proteins, pH, and pyrophosphates.”

The authors concluded that the technique they described to heat subnanoliter droplets-in-air for visualization of DNA denaturation with resolution down to single base mismatches has application to current DNA microarray technologies. The study was published on February 11, 2013, in the journal Proceedings of the National Academy of Science of the United States of America (PNAS).

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University of Illinois