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. 2020 Nov 30;10(12):195.
doi: 10.3390/bios10120195.

Label-Free and Sensitive Determination of Cadmium Ions Using a Ti-Modified Co3O4-Based Electrochemical Aptasensor

Yang Liu  1   2   3 , Dongwei Zhang  1   2   3 , Jina Ding  1   2   3 , Kashif Hayat  1   2   3 , Xijia Yang  1   2   3 , Xuejia Zhan  1   2   3 , Dan Zhang  1   2   3 , Yitong Lu  1   2   3 , Pei Zhou  1   2   3
Affiliations

Label-Free and Sensitive Determination of Cadmium Ions Using a Ti-Modified Co3O4-Based Electrochemical Aptasensor

Yang Liu et al. Biosensors (Basel). .

Abstract

The current work demonstrates an electrochemical aptasensor for sensitive determination of Cd2+ based on the Ti-modified Co3O4 nanoparticles. In this unlabeled system, Ti-modified Co3O4 nanoparticles act as current signal amplifiers modified on the screen-printed carbon electrode (SPCE) surface, while the derivative aptamer of Cd2+ works as a _target recognizer. In addition, the sensing is based on the increase in electrochemical probe thionine current signal due to the binding of aptamer to Cd2+ via specific recognition. In the current study, key parameters, including aptamer concentration, pH, and incubation time were optimized, respectively, to ensure sensing performance. Cyclic voltammetry was used not only to characterize each preparation and optimization step, but also to profile the bindings of aptamer to Cd2+. Under optimal conditions, Cd2+ can be determined in a linear range of 0.20 to 15 ng/mL, with a detection limit of 0.49 ng/mL, significantly below the maximum concentration limit set by the U.S. Environmental Protection Agency. Based on comparative analysis and the results of recovery test with real samples, this simple, label-free but highly selective method has considerable potential and thus can be used as an in-situ environmental monitoring platform for Cd2+ testing.

Keywords: Ti-modified Co3O4; aptamer; cadmium; cyclic voltammetry; electrochemical aptasensor.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Scheme 1
Scheme 1
Schematic view of fabrication and principle of a label-free electrochemical aptasensor used for Cd2+ determination in the current study.
Figure 1
Figure 1
SEM and TEM images of Co3O4 (a,b) and Co2Ti1 (c,d).
Figure 2
Figure 2
(a) XRD patterns and EDS elemental mapping images of (b) Co3O4 and (c) Co2Ti1.
Figure 3
Figure 3
CV of electrode under each assembly procedure from −0.65 to 0.00 V (scan rate: 100 mV/s): (a) bare electrode, (b) electrode modified with Co2Ti1, (c) electrode modified with Co2Ti1/aptamer, (d) electrode modified with Co2Ti1/aptamer/Cd2+.
Figure 4
Figure 4
(a) CV responses to aptasensor upon various concentrations of Cd2+ from a to g: (a) 0.2, (b) 1.0, (c) 3.0, (d) 5.0, (e) 7.5, (f) 10.0, (g) 15.0 ng/mL in detection buffer (pH = 5.5); (b) Calibration plots of ΔI versus concentration of Cd2+.
Figure 5
Figure 5
Selectivity of the aptasensor for Cd2+ determination. The concentrations of interfering ions were 50.0 ng/mL, and Cd2+ concentration was 2.0 ng/mL.
See this image and copyright information in PMC

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