Microfluidic chips for viral RNA extraction & detection

Sensing biomolecules at minute quantities demands laborious and skill-laden laboratory protocols for sample preparation and amplification in order to improve signal-to-noise ratio. Nucleic-acid-based detection of viral particles in whole blood requires separation of viral particles from blood cells followed by extraction, amplification, and detection of viral nucleic acids. Here, three microfluidic chips have been independently shown to be capable of performing each critical step. Separation of viral particles involves a flow-through, shear-type microfilter chip that can handle large volume of blood. The remaining chips, although developed for genomic DNA, have been adopted for extraction and amplification of viral RNA. In the extraction chip, protein coatings around viral particles are chemically broken to liberate viral RNA which can reversibly bind to the chip surface under high-salt conditions. Viral RNA can be eluted out with a low-salt buffer after removal of unwanted debris. In the amplification chip, viral RNA is first transcribed into cDNA and then multiplied exponentially in copies by a continuous, isothermal, enzyme-based technique known as Nucleic Acid Sequence-Based Amplification (NASBA). The amplicons are detected on the same chip using DNA probes conjugated with horse radish peroxide (HRP) for colorimetry