Fast three-dimensional DNA walker based on space double-confinement catalytic hairpin assembly for ultrasensitive homogeneous electrochemiluminescence detection of sonic hedgehog

DNA walkers have been widely used to build biosensing systems. However, their moving efficiency was limited, which has hindered practical applications. Here, we for the first time integrated localized CHA with nanoscale AuNPs scaffolds to achieve space double-confined catalytic hairpin assembly (SDCHA) for developing a fast three-dimensional DNA walker. Driven by spatially proximal displacement, the walker possessed a high walking speed, which was about 8 times, 9 times and 23 times faster than LCHA, CHA-AuNPs and conventional CHA, respectively. Moreover, the walking time was about 1.4–8.3 times shorter than most recently reported DNA walkers and space-confined strand displacement reactions. By further integrating it with magnetic probes and g-C3N4 nanosheets, an ultrasensitive and enzyme-free homogeneous electrochemiluminescence (Ho-ECL) aptasensor was firstly constructed for sonic hedgehog (SHh) detection. Profiting from this tailored integration, the Ho-ECL aptasensor avoided multiple interferences from complex milieu as well as tedious procedures of electrode modifying and washing, showing good signal stability, repeatability and reliability. It was also proved to achieve ultrasensitive SHh detection with the detection limit as low as 13.5 fM, superior to previous research on SHh detection. This work might broaden ideas for the construction of fast DNA walkers and facile Ho-ECL bioanalytical methods for clinical diagnosis.