Microfluidic Instrumentation for Biomolecular Diagnosis
In recent years, digital polymerase chain reaction (PCR) and digital enzyme-linked immunosorbent assay (ELISA) platforms have revolutionized detection technologies for absolute quantification of biomolecules. In contrast to the conventional biological and chemical assays conducted in large volumes such as in tubes and on plates, the basic principle of digital quantification of molecules is to divide the sample uniformly into a large quantity of small compartments. By doing so, an individual molecule is confined in a small volume in which the signal can be amplified and concentrated for detection. Compartmentalization technology that ensures the isolation of molecules in each compartment is the core to the success of digital quantification, which can be exquisitely achieved using uniform water-in-oil emulsions by droplet-based microfluidics.
We can combine the droplet manipulation and fluorescence based detection techniques for high-throughput and highly sensitive analysis of droplet content. Using an integrated droplet microfluidic platform, we demonstrated on-chip droplet-based digital PCR for absolute quantification of rare genes with a wide dynamic range (Biomicrofluidics, 2018). We extended the standard ELISA with our droplet digital PCR techniques to droplet-based single-exosome-counting enzyme-linked immunoassay for identifying membrane protein biomarkers and digital quantification of the target exosomes (Nano Letters, 2018).
