A signal amplification by QDs used for ferrocene-labeled sandwich aptasensor for determination of Hg2+ in water samples

In this paper, the design of a novel sandwich-type electrochemical aptasensor was reported for an ultrasensitive mercury ion (Hg²⁺) detection in water samples, which labeled with two-labeled aptamer (Apt) sequences. The used Apts were Apt1 and Apt2 as the capture and signal probe, respectively. The Apt1 probe was immobilized on the poly(4-aminobenzoic acid) (p-ABA) and quantum dots (QDs) film as the platform, as well as the Apt2 reporter was labeled with ferrocene. In the presence of Hg²⁺, the strong coordination complex has been formed between the specific thymine of the Apt1, Hg²⁺, as well as the thymine of the Apt as T–Hg²⁺–T adduct. The QDs and p-ABA were applied for increasing the conductivity of platform and suitable binding of the recognition elements. Under the optimized conditions, the constructed aptasensor illustrated either a wide linear relationship between the logarithm of Hg²⁺ concentration and current, from 0.05 to 100 nM and also an excellent low limit of detection of 0.01 nM. The quality of carefully choosing, an excellent stability and specificity sensitivity of the designed aptasensor, was investigated by spiked tap water samples as real sample. Moreover, the aptasensor exhibits the good reproducibility as well as has high selectivity for the other cations. The recoveries of the Hg²⁺ assay of the tap water samples were acquired satisfactorily which imply the generated aptasensor can use Hg²⁺ measurement in the real laboratories.