Fluorogenic RNA Aptamer‐Based Amplification and Transcription Strategy for Label‐free Sensing of Methyltransferase Activity in Complex Matrixes

Abstract DNA methyltransferase is significant in cellular activities and gene expression, and its aberrant expression is closely linked to various cancers during initiation and progression. Currently, there is a great demand for reliable and label‐free techniques for DNA methyltransferase evaluation in tumor diagnosis and cancer therapy. Herein, a low‐background fluorescent RNA aptamer‐based sensing approach for label‐free quantification of cytosine‐guanine (CpG) dinucleotides methyltransferase (M.SssI) is reported. The fluorogenic light‐up RNA aptamers‐based strategy exhibits high selectivity via restriction endonuclease, padlock‐based recognition, and RNA transcription. By combining rolling circle amplification (RCA), and RNA transcription with fluorescence response of RNA aptamers of Spinach‐dye compound, the proposed platform exhibited efficiently ultrahigh sensitivity toward M.SssI. Eventually, the detection can be achieved in a linear range of 0.02–100 U mL −1 with a detection limit of 1.6 × 10 −3 U mL −1 . Owing to these superior features, the method is further applied in serum samples spiked M.SssI, which delivers a recovery ranging from 92.0 to 107.0% and a relative standard deviation <7.0%, providing a promising and practical tool for determining M.SssI in complex biological matrices.