Enzyme-free Triple Cycles Triggered In-Situ Generation of Nanospheres on DNA Planar Tripod for Sensitive Photoelectrochemical Biosensor

In this work, the non-sensitizer participated photoactive 3D DNA nanospheres in-situ generated on rigid planar DNA tripod was proposed for constructing a novel photoelectrochemical (PEC) biosensor to realize the ultra sensitive detection of miRNA-141. First, the slight targets could be efficiently converted into numerous output DNAs through the enzyme-free triple cycles, which thus opened the hairpin at apex of planar DNA tripod on electrode to trigger the rolling cycle amplification (RCA) for in-situ producing 3D DNA nanospheres with loading of plentiful positively charged photoactive species perylene derivative (PDA(+)). Impressively, the unique rigid planar DNA tripod could not only adjust the distance among each hairpin on vertexes for simply enhancing the hybridization efficiency toward output DNA with effective improvement in the generation of 3D DNA nano spheres, but also endow the highly efficient decoration of PDA(+) approximated to electrode that beneficial to fast electron transport, thereby simply acquiring a low background and extremely high PEC signal without the need of sensitizers for improving detection sensitivity. As a result, the proposed approach showed a detection range from 0.1 fM to 100 pM for miRNA-141, providing a new and efficient strategy to construct sensitive PEC biosensor for potential application in early disease diagnosis and monitoring.