Target-induced activation of dual DNAzyme recycling amplifications for sensitive electrochemical fat mass and obesity-associated protein assay

The fat mass and obesity-associated protein (FTO) is vital for modulating dynamic reversible process of N6-methyladenosine (m 6 A) level in the nucleus and the abnormal expression of FTO correlates with generation and development of Alzheimer's disease, obesity and several cancers. The sensitive detection of FTO is therefore of significance for diagnosis of FTO-related diseases. In this work, on the basis of the demethylation enzyme capability of FTO and the dual Mg 2+ -dependent DNAzyme recycled signal magnification strategy, establishment of a highly sensitive electrochemical FTO biosensor is described. The target FTO molecules catalyze the demethylation of m 6 A-modifed sequences to form effective cleavage substrates for the MboI endonuclease, leading to the release of active DNAzyme sequences to trigger subsequent dual DNAzyme recycling cycles. Many methylene blue-tagged ssDNA sequences can thus be yielded via the DNAzyme amplifications and captured on the sensor electrode to generate highly amplified currents for detecting FTO in range of 0.04 pM to 10   nM with 6.11 fM detection limit. Additionally, the sensor demonstrates high selectivity and is able to be used for detecting cell lysate FTO, showing its potential for the diagnosis and study of FTO-related diseases for various application purposes.