Philippine Journal of Science
153 (5): 1593-1604, October 2024
ISSN 0031 – 7683
Date Received: 12 Apr 2024
Field-ready Voltammetric Detection of Aqueous Cadmium (II) Ions on Aptamer-modified Inkjet-printed Gold Electrode
Glenn D. Ongayo1,2*, Jiena Lynne R. Pauco1, and Erwin P. Enriquez1
1Department of Chemistry, Ateneo de Manila University, Katipunan, Quezon City 1105 the Philippines 2Department of Chemistry, University of Science and Technology of Southern Philippines, Cagayan de Oro City, Misamis Oriental 9000 the Philippines
*Corresponding authors: glenn.ongayo@ustp.edu.ph
Ongayo G et al. 2024. Field-ready Voltammetric Detection of Aqueous Cadmium (II) Ions on Aptamer-modified Inkjet-printed Gold Electrode. Philipp J Sci 153(5): 1593–1604.
ABSTRACT
In this work, a simple and cost-effective integrated electrode system consisting of aptamermodified inkjet-printed (IJP) gold working electrode and unmodified IJP gold as counter electrode (both printed on polyethylene naphthalate substrate) has been developed for low-cost detection of cadmium (II) ion in water. The technique uses a Cd2+ (Cd-4) aptamer, a singlestranded DNA with 31 nucleotides trapped on the working electrode using the self-assembly monolayer (SAM) technique. The electrochemical detection of Cd2+ is based on the change in redox peaks of [Fe(CN)6]3-/4- as a redox probe in cyclic voltammetry. The change in peak current is caused by a difference in electron transfer rate before and after binding the aptamer with the target ion (Cd2+). The electrochemical properties were further characterized using electrochemical impedance spectroscopy under optimal conditions, revealing changes in the charge transfer resistance upon binding the Cd2+ ion with the aptamer on gold. Detection by CV, the anodic peak currents (Ipa) varied linearly with Cd2+ concentration from 0.1–10 ng/ mL. Saturation of the working electrode’s active surface area was achieved with 10 ng/mL. The regression coefficient was 0.9977, whereas for the Cd2+ aptasensor, the limit of detection (LOD) was 0.5 ng/mL. The developed electrochemical aptasensor showed good sensitivity with a value of 1.94 µA/ng/mL and was partially selective in the presence of interfering divalent ions (Cu2+, Hg2+, Ni2+, and Zn2+). The RSD within the linear detection range (0.1–10 ppb) is 0.28%. The IJP aptasensor has simple and cost-effective compositions, consuming only 0.5 mg of Au loading of ink during the inkjet-printing process. Minimal chemical waste is also produced because the sample volume requirement for the analysis is only 50 µL. The IJP aptasensor has promising potential for rapid and on-site detection of Cd2+ in water samples using a portable CV system.
Keywords: aptamer, cadmium ions, field-ready, gold electrode, inkjet-printed, voltammetric detection