TetraWalk-PEC · Tetrahedral DNA Nanodevice with Entropy-Driven Amplification for Singlet Oxygen-Based Ratiometric Photoelectrochemical microRNA Biosensing

DNA, owing to its intrinsic programmability and molecular recognition ability, has emerged as a highly promising material for the development of next-generation biosensors. Rationally engineered nucleic acid nanostructures provide unique advantages in terms of hybridization efficiency, specificity, and sensitivity, enabling transformative diagnostic applications. In this project, a robust, split-mode, singlet oxygen (1O2)-based photoelectrochemical (PEC) biosensor for the ultrasensitive detection and quantification of the cancer biomarker miR-21 has been proposed. The core of the strategy relies on an entropy-driven tetrahedral DNA (EDTD) amplifier integrated with superparamagnetic nanostructures. The well-defined geometry and rigidity of DNA tetrahedra enhance structural stability, enabling precise spatial orientation and efficient recognition of target miRs, thereby improving hybridization efficiency and assay sensitivity. Superparamagnetic Fe3O4@SiO2 particles functionalized with type II photosensitizers and DNA nanostructures serve as the foundation for a split-mode PEC system, providing excellent selectivity, reproducibility, and magnetic manipulability. Notably, the enzyme- and hairpin-free EDTD amplifier eliminates the complications associated with pseudoknots or kissing loops in conventional hairpin-based systems, thereby reducing background noise and enhancing detection sensitivity. The proposed PEC biosensor combines the advantages of efficient electrode fabrication, operational stability, and reproducibility, while maintaining a rapid, low-cost, and user-friendly workflow suitable for POC testing. This innovative 1O2-driven PEC platform holds immense potential in diagnostics and can be broadly extended to a wide range of miRs assays in complex biological samples. By integrating photochemistry, electrochemistry, and DNA engineering, the project aims to deliver impactful advances in precision cancer diagnostics and translational healthcare technologies.