A novel microfluidic chip-based digital PCR method for enhanced sensitivity in the early diagnosis of colorectal cancer via mSEPT9

Background: To enhance the sensitivity of plasma methylated Septin9 gene (mSEPT9) detection in colorectal cancer (CRC) screening, we developed a microfluidic chip -based digital PCR (dPCR) method suitable for lowconcentration samples, aiming to apply it for mSEPT9 detection in CRC diagnosis. Methods: Our microfluidic chip -based dPCR method utilized specific primers and probes with locked nucleic acids (LNAs) modifications for mSEPT9 detection. We evaluated its performance, including detection limit, specificity, and linear range, comparing it with a commercial qPCR reagent kit using the same samples (95 CRC, 23 nonCRC). Results: The LNAs-modified dPCR method showed a linear range of 100-104 copies/mu L and a detection limit of 100 copies/mu L. Clinical testing revealed that our dPCR method exhibited a sensitivity of 82.11 % and specificity of 95.65 % for CRC diagnosis, outperforming the commercial qPCR kit (sensitivity: 58.95 %, specificity: 91.30 %), particularly in Stage I with a diagnostic sensitivity of 90.91 %. Combining mSEPT9 and carcinoembryonic antigen (CEA) improved diagnostic sensitivity to 91.49 %. Conclusions: Our accurate microfluidic chip -based dPCR method, especially in combination with CEA, holds promise for effective CRC screening and timely interventions, offering enhanced mSEPT9 quantification over conventional qPCR.