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Droplet Digital
™
PCR Applications Guide | 3
Fig. 1.4. The droplets created by the QX200 droplet generator are uniform in size and volume.
Droplet Generation
Before droplet generation, ddPCR reactions are prepared in a similar manner as real-time
PCR reactions that use TaqMan hydrolysis probes labeled with FAM and HEX (or VIC)
reporter fluorophores, or an intercalating dye such as EvaGreen.
ddPCR must be performed with the proprietary reagents developed specifically for droplet
generation by Bio-Rad. Reagent mixes include the ddPCR supermix for probes and
QX200 ddPCR EvaGreen supermix to partition DNA, and the one-step RT-ddPCR kit
for probes to partition RNA.
Samples are placed into a QX100 or QX200 droplet generator, which uses specially
developed reagents and microfluidics to partition each sample into 20,000 nanoliter-sized
droplets. As shown in Figure 1.3, target and background DNA are distributed randomly
into the droplets during the partitioning process.
Target of interest
Background DNA
Fig. 1.3. In ddPCR, a single PCR sample is partitioned into 20,000 droplets.
Droplet generation produces uniform droplets for the sample, enabling precise target
quantification (Figure 1.4).
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Droplets
Sample
Droplet Digital
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PCR