Dual enzyme-free amplification strategy for ultra-sensitive fluorescent detection of bisphenol A in water

An ultra-sensitive strategy for bisphenol A (BPA) detection based on dual enzyme-free strategies: hybridization chain reaction (HCR) and enzyme-strand recycling reaction has been developed. The BPA aptamer can form hairpins structure by the partly self-complementary sequence. In the presence of BPA, the released BPA aptamer sequence can trigger the HCR between two hairpins to from a long nicked double-helix DNA. The tails of hairpins on the duplex DNA were closely enough to hybridize with molecular beacon (MB) on the gold nanoparticles (AuNPs) to circularly cleave the loop of MB, leading to a "turn-on" fluorescent signal. This method exhibited high sensitivity for BPA detection in a linear rang from 0.2 to 1000 pM with 0.05 pM of limit of detection. Moreover, it was successfully used for BPA detection in real water samples. Importantly, this method was simple without complex enzymatic procedure and high cost, showing a promising future for on-site detection of BPA in practical application.