Dual-Signal Readout of DNA Methylation Status Based on the Assembly of a Supersandwich Electrochemical Biosensor without Enzymatic Reaction

A highly sensitive and selective biosensing system was designed to analyze DNA methylation using a dual-signal readout technique in combination with the signal amplification of supersandwich DNA structure. Through the ingenious design of target-triggered cascade of hybridization chain reaction, one target DNA could initiate the formation of supersandwich structure with multiple signal probes. As a result, one-to-multiple amplification effect was achieved, which conferred high sensitivity to target molecular recognition. Based on probe 1 labeled with ferrocene and probe 2 modified with methylene blue, the target DNA was clearly recognized by two electrochemical signals at independent potentials, which was helpful for the acquisition of more accurate detection results. Taking advantage of bisulfite conversion, the methylation status of cytosine (C) was changed to nucleic acid sequence status, which facilitated the hybridization-based detection without enzymatic reaction. Consequently, the methylated DNA was detected at the femtomolar level with satisfactory analytical parameters. The proposed system was effectively used to assess methylated DNA in human blood serum samples, illuminating the possibility of the sensing platform for applications in disease diagnosis and biochemistry research.