<p>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&#xa0;M, and their detection limits are 59.8&#xa0;pM of Pb²⁺ and Cd²⁺ of 146.2&#xa0;pM; LOQ are 93.7&#xa0;pM of Pb²⁺ and 164.8&#xa0;pM of Cd²⁺, respectively.</p>