Droplet-based digital PCR (ddPCR) and its applications

As a new generation absolute quantitive PCR technique, droplet-based digital PCR (ddPCR) provides the benefits of high sensitivity, precision, and reproducibility. A low-cost, portable, and simple-to-use ddPCR device has emerged as a research hotspot because of the rising demand for point-of-care (POC) detection and clinical diagnosis. Due to its integration and miniaturization properties, microfluidic technology has been used in various ddPCR processes. In this review, we present new theories and methods for the four primary ddPCR processes: droplet production, signal amplification, signal detection, and signal quantification. Integrated microfluidic ddPCR platforms are also introduced. Subsequently, we summarize the applications of ddPCR in liquid biopsy, noninvasive prenatal testing, pathogens detection, and genetically modified organism analysis. At last, the existing challenges and prospects of ddPCR are discussed.