A novel sensitive disposable screen-printed electrochemical aptasensor based on gold nanoparticles decorated multilayer Nb4C3Tx for cadmium ion detection

Cadmium ion (Cd²⁺) is one of the most poisonous metallic pollutants, which would lead to many health issues due to it can accumulate in body through food chain and cannot undegradability. Herein, a new disposable screen printed electrochemical aptamer sensor (aptasensor) was designed to detect Cd²⁺ in water environments. Multilayer Nb₄C₃Tx (ML-Nb₄C₃Tx) was firstly modified onto the screen-printed carbon electrode (SPCE) surface as the substrate materials to support large surface area, and later gold nanoparticles (AuNPs) were loaded onto the surface of ML-Nb₄C₃Tx through electrodeposition. Subsequently, the double-stranded DNA including aptamers was self-assembly onto the modified electrode surface by the bond of Au-S. Due to its high specificity towards Cd²⁺, the aptamers tagged with ferrocene would specifically combine with Cd²⁺ to form folded structures, and then leave from the electrode surface. After that, the current changes of electrochemical aptasensor can be detected by square wave voltammetry (SWV). Under the optimized experimental conditions, the proposed aptasensor exhibits a good linear relationship between the current values with the logarithm of Cd²⁺ concentrations from 0 to 1000 μg/L, and its LOD was calculated as 0.08 μg/L (S/N=3). Besides, the electrochemical aptasensor shows high sensitivity, great selectivity, acceptable reproducibility and good stability.