A sensitive aptamer electrochemical biosensor (aptamer/(AuNPs/CS)2/GCE) based on glass carbon electrode (GCE) modified with chitosan (CS), gold nanoparticles (AuNPs) and Cd-aptamer for the detection of cadmium ions (Cd2+) in tap water samples has been successfully developed. Herein, CS was used to immobilize AuNPs on electrode and to improve electronic transmission between Cd2+ and aptamer/(AuNPs/CS)2/GCE. AuNPs were used to immobilize aptamers as well as enhance electron transfer reaction to improve the ability of test analysis. Aptamers were used to identify targets cadmium ions for further improving analytical performance of the biosensors, and 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 Cd2+/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). As a result, the proposed aptamer 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.

Aptamer electrochemical biosensor for cadmium ions detection

2019 Spring National Meeting

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