Figure 4. Droplet-based detection of nucleic acid biomarkers.

(A) Droplet-based digital PCR was used to screen for mutations in the KRAS oncogene. (Reproduced from (Pekin et al., 2011) with permission of The Royal Society of Chemistry). TaqMan probes specific for the wild-type and mutant genes were encapsulated in droplets that contain at most one haploid genome. The emulsion was then thermocycled off-chip, and reinjected for fluorescence detection. By optically coding droplet groups, parallel analysis of six mutations in KRAS were detected simultaneously using this platform. (B) An integrated platform for viral RNA detection using RT-PCR was developed, where 70 pL droplets containing MS2 virions and RT-PCR reagents were immobilized in microfluidic channels. An integrated thermal cycler provided temperatures necessary for reverse transcription and PCR, and a CCD camera was used for fluorescence detection. (Reprinted with permission from (Beer et al., 2008). Copyright 2007 American Chemical Society.) (C) Loop-mediated isothermal amplification was demonstrated for detection and quantification of N. gonorrhoeae gDNA down to 600 copies per μL. Critically, the assay was conducted in continuous-flow in an integrated platform that facilitated digitization of targets, on-chip incubation, and detection. (Reproduced from (Rane, TD; Chen, L; Zec, HC; Wang, 2014) with permission of The Royal Society of Chemistry).