Designed diblock hairpin probes for the nonenzymatic and label-free detection of nucleic acid

The detection of nucleic acid sequences is of great importance in a variety of fields. An ultrasensitive DNA sensing platform is constructed using elaborately designed diblock hairpin probes (DHPs) that are composed of hairpin and poly-adenine blocks. The introduction of an initiator DNA target triggers the catalytic assembly of probes DHP1, DHP2 and DHP3 to fabricate numerous poly-adenine-tailed branched DNA junctions, which significantly amplify the signal of the target-DNA-recognizing event without any enzyme. Coupled to a gold nanoparticle-based colorimetric assay, the amplified recognition signal can be quantitatively detected or visually read with the naked eye. The combination of the high-efficiency target-catalyzed DHP assembly and sensitive gold-based colorimetric assay offers an ultrasensitive detection of DNA with a detection limit of 0.1 pM and a dynamic range from 0.01 to 5 pM. The proposed sensing platform can discriminate even single-base mutations. Moreover, the sensing platform can be expanded to detect pollutant-degrading-bacteria-specific DNA sequences. The proposed sensing system should offer an alternative approach for the detection of nucleic acids in the fields of microbiology, biogeochemistry, and environmental sciences.