DNA self-assembly for signal enhancement in nucleic acids biosensors

Some of the possible perspective advantages of the uptake of nucleic acids biosensor technology are already within reach, still, the sometimes limited sensitivity can seriously inhibit the application of biosensor-based methods when these could be useful towards detection of nucleic acids variants present only at a very low concentration. We have adapted and succeeded at using the hybridization chain reaction (HCR)[1] towards enhancing the signal due to the specific recognition and binding of soluble nucleic acids to a surface-bound probe. The enhancement strategy consists in a triggered supramolecular polymerization of DNA sequences or nanostructures at the location of specific nucleic acids recognition. We have showed that the method can be used towards the detection of an arbitrary DNA target through proper design of the sequences of the components[2]. Preliminary experimental evidence shows a significant enhancement of the signal, which could prove useful in some applications. We also proved that HCR can have single-nucleotide sensitivity for the detection and signal enhancement. We have recently worked at the extension of HCR towards the detection of circulating miRNA targets, biomarkers of considerable interest for diagnostics. We have showed that HCR reagents can be designed to distinguish between closely-related miRNA targets, as it would be needed in diagnostics. Modifications of the HCR design can yield hyperbranched or target-recycling assembly and thus significantly increase the detection signal. We have preliminary results on a branched HCR design that could be compatible with surface-bound biosensors implementation (electrochemical, fluorescence, luminescence, SPR). We showed sensitivity to single-nucleotide mismatch and proved that the sensing strategy could be applicable to the detection of nucleic acids from pathogens or of circulating miRNA.