Experimental results using cell lines to improve the dPCR method for the highly sensitive mutation analysis of simple prepared samples. (A) Encapsulated cells in dPCR droplets. Cells were collected, resuspended in dPCR reaction solution, and mixed with droplet generation oil using the QX200 droplet generator. Scale bars; 200 μm. (B) Cells were burst using pure water. Cells were collected and resuspended in nuclease-free water, which caused an osmotic burst of cells, and genomic DNA was released into the water. The “crude” solution, including gDNA, was used as the dPCR template. Scale bars; 500 μm. (C) The DPCR assay was performed using the two novel DNA preparation methods, without a purification step. KRAS wild-type (Fibroblast; NB1RGB) and KRAS G12C (PDA; MIA PaCa-2) cells were mixed with several dilution series (left panel). The wild-type or G12C mutation in KRAS was detected using the QX200 droplet reader, as compared to the conventional DNA preparation method using commercial purification kits (see details in “Methods”). The KRAS copy number of wild-type or G12C measured by QuantaSoft software (right panel).