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. 2022 Oct 26;12(11):2593.
doi: 10.3390/diagnostics12112593.

Graphene-Based Sensor for the Detection of Cortisol for Stress Level Monitoring and Diagnostics

Affiliations

Graphene-Based Sensor for the Detection of Cortisol for Stress Level Monitoring and Diagnostics

Alexei Zubarev et al. Diagnostics (Basel). .

Abstract

In this work, we study the sensing properties of multi-layer graphene combined with pyrrole in order to elaborate low-cost, high-sensitive material for cortisol detection. Graphene nanoplatelets and pyrrole were dispersed in a solution containing 1M HNO3 by using a powerful ultrasound probe for 10 min, then centrifuged for 30 min at 4000 rpm; polymerization was performed by cyclic voltammetry. The graphene-pyrrole composite was tested to ultra-low levels of cortisol in artificial saliva, consistent to the levels excreted in human salivary samples. The composite was further investigated by Raman spectroscopy and we modeled the interaction between the sensitive layer and cortisol using MarvinBeans software. It shows a good sensitivity for salivary values of cortisol cyclic voltammetry being able to detect a level down to 0.5 ng/mL cortisol.

Keywords: cortisol; cyclic voltammetry; electrochemical sensors; graphene-based sensing materials; graphene/pyrrole.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Electropolymerization results for the graphene–pyrrole composite: (a) the voltammogram of each of the 20 cycles of the polymerization procedure; (b) the total charge exchanged in the polymerization process as function of the number of cycles.
Figure 2
Figure 2
Electrochemical behavior of the composite in artificial saliva: (a) variation of the current-voltage characteristics at different scanning rates; (b) anodic/cathodic potential as function of the square root of the scanning rate; (c) anodic/cathodic peak intensity as function of the square root of the scanning rate; (d) total charge vs. the square root of the scanning speed.
Figure 2
Figure 2
Electrochemical behavior of the composite in artificial saliva: (a) variation of the current-voltage characteristics at different scanning rates; (b) anodic/cathodic potential as function of the square root of the scanning rate; (c) anodic/cathodic peak intensity as function of the square root of the scanning rate; (d) total charge vs. the square root of the scanning speed.
Figure 3
Figure 3
Electrochemical results for the detection of cortisol in artificial saliva with the composite material: (a) the cyclic voltammograms for the six concentrations of hydrocortisone in artificial saliva; (b) the variation of the anodic/cathodic potential with the concentration of the cortisol samples; (c) anodic/cathodic peak intensity variation as function of the cortisol concentration; (d) the charge transfer for the anodic/cathodic processes as function of the different cortisol concentrations.
Figure 4
Figure 4
Raman spectrum of the composite compared to the Raman spectra of the constituents. The arrows indicate the low intensity peaks at 1386 and 1476 cm−1 associated with pyrrole.
Figure 5
Figure 5
Modeling of the reaction between the graphene–pyrrole composite and cortisol with MarvinBean®.

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