▎ 摘　　要

NOVELTY - Use of methylated DNA is claimed as a marker for early cancer diagnosis and preparing tumor treatment targeted medicine, where the methylated DNA comprises a 35 base pair sequence (SEQ ID NO: 3) fully defined in the specification. USE - The methylated DNA is used as a marker for preparing kit or DNA sensor for early cancer diagnosis and tumor treatment targeted medicine (claimed). ADVANTAGE - The methylated DNA combines the triple-helical nucleic acid structure with electrochemical technology to construct a simple, stable, and highly specific DNA methylation site analysis technology, detects maximum of 7 DNA methylation sites, which is more than the existing methods and provides new technical means for the early clinical diagnosis of genetic disorder diseases and tumors and the selection of demethylation targeted treatment options. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following: DNA biosensor prepared using methylated DNA. (1) kit comprises the base pair sequence of SEQ ID NO: 3; (2) method for analyzing DNA methylation sites of methylated DNA, involves (a) using gold nanoparticles (AuNPs)-reduced graphene oxide (rGO) complex material for modifying the gold electrode, (b) designing capture probes, auxiliary probes and target sequences of different methylation sites, (c) performing DNA hybridization induces signal amplification of gold nanoparticle aggregation, (d) preparing anti-5-methylcytosine antibody capable of specifically recognizing methylation sites, (e) optimizing the most suitable experimental conditions for electrochemical sensor analysis technology, (f) performing electrochemical detection and (g) detecting methylated DNA in serum; and