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

- AGR2 detection was realized based on HCR for the first time;
- AGR2 detection was realized firstly using the fluorescence quenching of AuNPs;
- A low detection limit of 2.65 pM was obtained for AGR2 detection;
- The sensor is highly specific to AGR2 due to the application of aptamer;
- Satisfactory results were obtained for AGR2 detection in real samples.

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 (HP1 and HP2) that contained the sticky tails were designed, and AGR2 aptamer was used as an initiator for the happen of HCR between HP1 and HP2 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 HP1 and HP2 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 HP1 and HP2 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.