Fluorescent biosensor for detecting activity of DNA transmethylase and preparation method of fluorescent biosensor

The invention relates to the technical field of biosensors, in particular to a fluorescent biosensor for detecting the activity of DNA transmethylase based on the catalytic hairpin self-assembling. Based on the specific identification of a methylated target object and nucleic acid probe, a three-way circuit structure is formed continuously by utilizing the catalytic hairpin self-assembling, a trigger is circularly amplified, the tail end of the three-way circuit is combined with a signal probe comprising a fluorescent group by virtue of complementary pairing of basic groups, finally a cleavagesite (AP site) of endonuclease IV is used for implementing the positioning cut, and the fluorescent group is released to generate a fluorescent signal of a given intensity. The sensor has the advantages of high detection speed, low detection limit, high specificity and the like, overcomes the defects for detecting the methylation of the DNA at present, and realizes the rapid and accurate quantitative detection for the me