Digital microfluidics: a future technology in the newborn screening laboratory?

Expansion of newborn screening for inherited metabolic disorders using tandem mass spectrometry has generated interest in screening for other treatable conditions, including lysosomal storage diseases. Limitations to expansion include labor and equipment costs. We describe a cost-effective new platform that reduces the time to result reporting and can perform multiplexing assays requiring different platforms. Immunoassays and enzyme activity assays currently used in newborn screening have been translated to a disposable microchip programmed to dispense, transport, mix, wash, and incubate individual microdroplets from specimens, including dried blood spot extracts, and reagents all under software control. The specimen and reagents consumed are approximately 1% of those required by equivalent bench assays. In addition to immunologic and enzymatic assays, DNA amplification, amplicon detection, and sequencing have been demonstrated using the same microchips and control equipment. Recently, the multiplexing of 4 different enzyme activities has also been demonstrated with negligible cross-contamination. We review assays relevant to newborn screening.

Development of a digital microfluidic platform for point of care testing

Point of care testing is playing an increasingly important role in improving the clinical outcome in health care management. The salient features of a point of care device are rapid results, integrated sample preparation and processing, small sample volumes, portability, multifunctionality and low cost. In this paper, we demonstrate some of these salient features utilizing an electrowetting-based Digital Microfluidic platform. We demonstrate the performance of magnetic bead-based immunoassays (cardiac troponin I) on a digital microfluidic cartridge in less than 8 minutes using whole blood samples. Using the same microfluidic cartridge, a 40-cycle real-time polymerase chain reaction was performed within 12 minutes by shuttling a droplet between two thermal zones. We further demonstrate, on the same cartridge, the capability to perform sample preparation for bacterial infectious disease pathogen, methicillin-resistant Staphylococcus aureus and for human genomic DNA using magnetic beads. In addition to rapid results and integrated sample preparation, electrowetting-based digital microfluidic instruments are highly portable because fluid pumping is performed electronically. All the digital microfluidic chips presented here were fabricated on printed circuit boards utilizing mass production techniques that keep the cost of the chip low. Due to the modularity and scalability afforded by digital microfluidics, multifunctional testing capability, such as combinations within and between immunoassays, DNA amplification, and enzymatic assays, can be brought to the point of care at a relatively low cost because a single chip can be configured in software for different assays required along the path of care.