Electrochemical DNA sensor for inorganic mercury(II) ion at attomolar level in dairy product using Cu(II)-anchored metal-organic framework as mimetic catalyst

A sensitive and practical electrochemical DNA sensor is developed for evaluating attomolar mercury ion (Hg2+) in dairy product. Herein, the porous graphene oxide/gold nanoparticles (GO@Au) hybrids are exploited to construct high-conductive sensing interface. And importantly, Cu(II)-anchored metal-organic frameworks (MOFs) are prepared to design favorable signal probes for enzyme-free catalytic amplification. The results demonstrate that Cu(II)-anchored MOFs show excellent catalytic activity to glucose oxidation and offer an alternative mimetic catalyst to amplify the electrochemical signal. This approach attains an ultrasensitive assay of Hg2+ ranging from 0.10 aM to 100 nM with detection limit of 0.001 aM. Moreover, benefiting from thymine-Hg2+-thymine (T-Hg2+-T) coordination chemistry, the strategy exhibits good anti-jamming capability to distinguish Hg2+ from complex media, and thus could be applied for direct and rapid monitoring of Hg2+ in dairy product. The proposed sensor provides a valuable protocol with simple preparation, easy regeneration, high sensitivity and selectivity, indicating a promising prospect for on-site assessing quality deterioration in dairy product polluted with Hg2+.