A double signal amplification strategy for sensitive detection of Hg²⁺ based on exonuclease III and PCR

A double signal amplification method was developed for sensitive detection of Hg²⁺ based on exonuclease III (Exo III) and Polymerase Chain Reaction (PCR). In the presence of Hg²⁺, the ineffective primers could bind with helper DNA to form dsDNA by T-Hg(II)-T mismatch for the first signal amplification. Then, the ineffective primers were digested by Exo III to effective primers which initiate PCR reaction for the second signal amplification. This conversion from ineffective to effective primers for triggering PCR reaction has not been reported for the detection of Hg²⁺. Through the double signal amplification strategy, the sensitivity of this proposed method was significantly improved with the limit of detection 1.46 nM. With the specific T-Hg(II)-T recognition, the selectivity of this new method was satisfactory. And the recoveries were between 92.3 % and 109.0 %. These results suggested that the proposed method was reliable to detect Hg²⁺ in water samples.