QX200 Droplet Digital PCR System (ddPCR) represents the second-generation of digital PCR system, which provides absolute quantification of target DNA or RNA molecules using EvaGreen or TaqMan Hydrolysis Probes. The instrument consists of two basic instruments, the QX200 Droplet Generator (fig. 1a) and the QX200 Droplet Reader (fig. 1b), and two accessories - PX1 PCR Plate Sealer (fig.1c) and C1000 Touch Thermal Cycler with 96–Deep Well Reaction Module (1d) . PX1 PCR Plate Sealer includes plate support block that holds 96-well and 384-well plates, sealing frame, power cord. C1000 Touch Thermal Cycler contains C1000 Touch Thermal Cycler chassis, 96–deep well reaction module and USB flash drive.
Fig. 1. Components of QX200 Droplet Digital PCR System
a) QX200 Droplet Generator
b) QX200 Droplet Reader
c) PX1 PCR Plate Sealer
d) C1000 Touch Thermal Cycler
In brief, the principle of this techniqoe is partition PCR reaction mix into thousands of nanoliter-sized droplets . PCR reaction is running in each droplet and droplets are are read well by well as they are streamed single file past a two-color optical detection system in a serial manner. Up to 96 samples can be processed per run. The PCR-positive and PCR-negative droplets are counted to provide absolute quantification of target in digital form (fig.2). In addition, amplified products can be extracted from droplets and subjected to sequencing or cloning.
Fig. 2. Schematic workflow of ddPCR