Cd-Aptamer Electrochemical Biosensor Based on AuNPs/CS Modified Glass Carbon Electrode

An ultrasensitive aptamer electrochemical biosensor based on glass carbon electrode (GCE) modified with chitosan (CS), gold nanoparticles (AuNPs) and aptamer has been successfully constructed and used to detect cadmium ions (Cd2+). The poly-(diallyl dimethyl ammonium chloride) (PDDA) was applied to neutralize Cd-aptamer via electrostatic interaction. The presence of Cd2+ would trigger Cd-aptamer conformation change causing the Cd/Cd-aptamer complex to adsorb more electrochemical signal indicator [Ru(NH3)6]3+ instead of PDDA. Through differential pulse voltammetry (DPV) detection, the peak current increased along with the increase in concentration of Cd2+, and the linear ranges were from 0.001 nM to 100 nM (1.124 × 10–13 g/mL to 1.124 × 10–8 g/mL) with the detection limit as low as 0.04995 pM (5.614 ×10–15 g/mL). The proposed biosensor exhibited good stability, high sensitivity and selectivity towards Cd2+. Furthermore, this Cd-aptamer biosensor was demonstrated in testing Cd2+ in tap water samples with satisfactory results.