Engineering DNA tetrahedron as a sensing surface of lateral flow test strips and ratiometric visual detection of exosomal microRNA-150–5p

Abstract

We here report that DNA tetrahedral probe-based sensing surfaces are capable of efficiently capturing gold nanoparticles (AuNPs) on lateral flow test strips, and we have developed a ratiometric biosensor for exosomal microRNAs by integrating a tetrahedral probe and a catalytic hairpin assembly (CHA). DNA tetrahedrons were devised with barcodes and labeled with biotin as capture probes on the test and control lines of the strip. The CHA system consists of two hairpin substrates that can form stable duplexes via a programmable assembly reaction triggered by exosomal miRNAs. The duplexes hybridized with barcoded tetrahedra via complementary sequences and bound to streptavidin-modified AuNPs (SA-AuNPs) via biotin. Thus, a red line was observed on the test line owing to the immobilized SA-AuNPs. The remaining SA-AuNPs were captured by using a biotinylated tetrahedron on the control line. Because the barcoded and biotinylated tetrahedra consume SA-AuNPs simultaneously, a stronger signal in the test line results in a weaker signal in the control line, thus forming a ratiometric result. Tetrahedral probes avoid movement along with sample flow on sensing zones like single-stranded probes. The strip can have a detection limit of 58.90 fM with high selectivity due to the use of ratiometric color changing response, CHA signal amplification and tetrahedral capture probes. This system is able to rapidly detect exosomal microRNA-150–5p and may have a potential utility in point-of-care diagnosis of incipient diabetic nephropathy.