Ultrasensitive Electrochemical Biosensor for DNA Methylation Detection Based on Fe-MOF/PANI and Catalytic Hairpin Assembly Cascade Reaction

DNA methylation, as an important epigenetic modification, is closely related to gene expression regulation and cancer development. This study developed a new electrochemical biosensor for ultrasensitive detection of DNA methylation based on the combination of Fe/metal-organic framework (MOF)/polymer polyaniline (PANI) composite materials and catalytic hairpin assembly (CHA) cascade reaction. The Fe/MOF/PANI/S1, as the signal probe, significantly improved the conductivity and stability by doping conductive PANI into Fe/MOF. The sensor used DNAzyme to catalyze methylated DNA to trigger the CHA cascade reaction, and thus several cross-shaped CHA products were achieved. The capture probe was modified on the surface of the Au electrode to hybridize with CHA products. Thus, the binding sites were exposed to enable large amounts of Fe-MOF/PANI/S1 signal probes to bind effectively, and the electrochemical signals were generated. The sensor could produce measurable electrochemical responses in the presence of methylated DNA, with the limit of detection as low as 0.58 fM. It showed excellent specificity, repeatability (RSD = 2.23%), and stability (over 90% signal retention after 20 days). In addition, it showed high recovery in human serum samples, verifying its potential for practical applications. This will pave a new way for the rapid and sensitive detection of DNA methylation.