Dual cascade nucleic acid recycling-amplified assembly of hyperbranched DNA nanostructures to construct a novel plasmonic colorimetric biosensing method.

The plasmonic colorimetric biosensors are very favorable for the on-site testing and naked-eye screening of analytes from real samples, but how to realize their highly sensitive assays with simple manipulations is still a great challenge. Herein we designed a target-triggered dual cascade nucleic acid recycling strategy to amplify the assembly of a hyperbranched DNA nanostructure and thus developed a novel kanamycin colorimetric biosensing method. The first cycle arising from the aptamer recognition-triggered strand displacement reaction and its cascade cycle constructed on the catalytic reaction of two nucleases could release an output DNA to trigger the assembly of the DNA nanostructure. Based on the high capture of alkaline phosphatase at this DNA nanostructure to induce the localized surface plasmon resonance change of gold nanobipyramids (Au NBPs), an ultrasensitive colorimetric signal transduction strategy was constructed. Through the measurement of the shift of the characteristic absorption wavelength of Au NBPs, a very wide linear range from 10 fg mL to 1 ng mL and a very low detection limit of 1.4 fg mL were obtained. Meanwhile, the obvious multicolor change of Au NBPs could be used for the visual semi-quantitative analysis of Kana residues. The whole homogeneous assay process well simplified the manipulation and also ensured the excellent repeatability. These excellent performances determine the great potential of the method for future applications.