A novel disposable dual-sensing platform based on DNA-aptamer amplified with gold nanoparticles/Nb4C3-MXene for simultaneous detection of lead and cadmium

Herein, we designed a special screen-printing carbon electrode system with two independent zones to realize the immobilization of two kinds of aptamers on electrode surface. Nb4C3-MXene is a remarkable member from MX3 MXene with many excellent properties. In this study, Nb4C3-MXene nanosheets were firstly modified onto the screen-printing carbon electrode surface as the substrate materials to offer big surface area and then gold nanoparticles were loaded onto the surface of Nb4C3-MXene nanosheets through electrodeposition. Afterward, the aptamer-containing double-stranded DNA was spontaneously assembled onto the modified electrode surface through the Au–S bond. Owing to high affinity of aptamers towards the heavy metal ions (Cd2+ and Pb2+ in this case), the aptamers tagged with methylene blue and ferrocene would specifically bond with heavy metal ions to form folded structures and competed off from the electrode surface, and then the change of electrochemical signals can be detected by square wave voltammetry. The aptasensor exhibits a good linear response towards Cd2+ and Pb2+ from 1 × 10−10 to 1 × 10−7 M, and their detection limits are 59.8 pM of Pb2+ and Cd2+ of 146.2 pM; LOQ are 93.7 pM of Pb2+ and 164.8 pM of Cd2+, respectively.