Molybdenum disulfide@5-carboxyfluorescein-probe biosensor for unamplified specific fragment detection in long nucleic acids based on magnetic composite probe-actuated deblocking of secondary structure.

Secondary structures in long circulating tumor nucleic acids have potential obstacles for specific location point hybridized detection of gene fragments. The exploration of biosensing strategies requires selectively changing the nucleic acids conformation and inducing signal switching. Herein, a self-assembled magnetic composite probe (MCP) was fabricated by the hybridization reaction of Linker DNA and a “Y”-junction-DNA nanostructure on the surface of magnetic beads, contributing to the capture, secondary structure unlocking, and enrichment of the PML/RARα DNA “L” subtype. Then, by integrating the MCP-actuated reactor, a one-step “off–on” signal switching MoS2@FAM-probe biosensing method was developed for the efficient detection of the PML/RARα DNA “L” subtype. The proposed biosensor was capable of detecting 100 bases PML/RARα DNA “L” subtype with a wide linear range of 1 pM to 200 nM and a limit of detection down to 0.223 pM without signal amplification. In addition, the biosensing method was successfully applied for the detection of target in serum samples. It is worth pointing out that this simple biosensing strategy could enable long nucleic acids fragments with secondary structures from ctDNA and ctRNA to be quantitatively assayed based on direct hybridization.