Centrifugal Microfluidic Integration of 4-Plex ddPCR Demonstrated by the Quantification of Cancer-Associated Point Mutations

• Main Authors: Franziska Schlenker, Elena Kipf, Nadine Borst, Nils Paust, Roland Zengerle, Felix von Stetten, Peter Juelg, Tobias Hutzenlaub
• Format: Article
• Language: English
• Published: MDPI AG 2021-01-01
• Series: Processes
• Subjects: microfluidics; digital droplet polymerase chain reaction (ddPCR); multiplexing; centrifugal step emulsification; droplet stability; droplet fluorescence evaluation
• Online Access: https://www.mdpi.com/2227-9717/9/1/97

We present the centrifugal microfluidic implementation of a four-plex digital droplet polymerase chain reaction (ddPCR). The platform features 12 identical ddPCR units on a LabDisk cartridge, each capable of generating droplets with a diameter of 82.7 ± 9 µm. By investigating different oil–surfactant concentrations, we identified a robust process for droplet generation and stabilization. We observed high droplet stability during thermocycling and endpoint fluorescence imaging, as is required for ddPCRs. Furthermore, we introduce an automated process for four-color fluorescence imaging using a commercial cell analysis microscope, including a customized software pipeline for ddPCR image evaluation. The applicability of ddPCRs is demonstrated by the quantification of three cancer-associated <i>KRAS</i> point mutations (G12D, G12V and G12A) in a diagnostically relevant wild type DNA background. The four-plex assay showed high sensitivity (3.5–35 mutant DNA copies in 15,000 wild type DNA copies) and linear performance (R² = 0.99) across all targets in the LabDisk.