Hybridization chain reaction coupled with the fluorescence quenching of gold nanoparticles for sensitive cancer protein detection

An ultrasensitive and enzyme-free sensing platform was designed for sensitive detection of anterior gradient homolog 2 (AGR2) based on the fluorescence quenching of gold nanoparticles (AuNPs) coupled with hybridization chain reaction (HCR) amplification. To construct the sensor, two fluorophore labeled hairpin probes (HP 1 and HP 2 ) that contained the sticky tails were designed, and AGR2 aptamer was used as an initiator for the happen of HCR between HP 1 and HP 2 to form a long nicked dsDNA duplex. Such DNA duplex could not adsorb onto the surface of AuNPs, and a strong fluorescence signal appeared due to the label of HP 1 and HP 2 with fluorophore. In the presence of AGR2, AGR2 aptamer would specifically recognize with it and accordingly could not trigger the happen of HCR. As a result, the sticky tails of HP 1 and HP 2 would adsorb onto the surface of AuNPs to bring the fluorophore into the close proximity of the AuNPs, and lead to the quenching of the fluorescence signal. By using such method, AGR2 could be sensitively detected in the range of 5.0   pM–1.0   nM based on monitoring the decrease of the fluorescence signal. Importantly, the assay could realize the detection of AGR2 effectively in diluted human serum samples.