A fluorescence polarization assay for nucleic acid based on the amplification of hybridization chain reaction and nanoparticles

An amplified fluorescence polarization (FP) assay based on hybridization chain reaction (HCR) and nanoparticles was developed for the detection of nucleic acid. In this work, the target nucleic acid could trigger the autonomous cross-opening the biotin-modified hairpin probe H1 and fluorescein-labeled hairpin probe H2 to form long fluorescent nicked double-strand polymers (dsDNA). Thus the FP value was increased because the rotation rate of fluorescein slowed down by the formation long HCR products with a larger molecular mass. After then introduction of streptavidin-coated the SiO2 nanoparticles (SA-SiNPs), the HCR-produced dsDNA products and SA-SiNPs were combined via the interactions of biotin and streptavidin, generating much larger fluorescent complexes. Thus, a further amplified FP signal was obtained. Under optimized conditions, the developed method exhibits a linear response to nucleic acid in the concentration range of 0-2.5 nM, and the limit of detection is 35 pM. Moreover, the FP assay also showed high precision, pronounced specificity and the applicability in complicated human serum matrix.