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. 2019 Sep 26;5(9):FSO416.
doi: 10.2144/fsoa-2019-0061.

CortiWatch: watch-based cortisol tracker

Paul Rice  1 , Sayali Upasham  1 , Badrinath Jagannath  1 , Roshan Manuel  1 , Madhavi Pali  1 , Shalini Prasad  1
Affiliations

CortiWatch: watch-based cortisol tracker

Paul Rice et al. Future Sci OA. .

Abstract

Sweat-based analytics have recently caught the attention of researchers and medical professionals alike because they do not require professionally trained personnel or invasive collection techniques to obtain a sample. The following presents a small form-factor biosensor for reporting physiological ranges of cortisol present in ambient sweat (8-151 ng/ml). This device obtains cortisol measurements through low volumes of unstimulated sweat from the user's wrist. We designed a potentiostatic circuit on a printed circuit board to perform electrochemical testing techniques. The detection modality developed for quantifying sensor response to varying cortisol concentrations is a current based electrochemical technique, chronoamperometry (CA). From the results, the sensor can detect cortisol in the physiologically relevant ranges of cortisol; thus, the sensor is a noninvasive, label free, cost-effective solution for tracking cortisol levels for circadian diagnostics.

Keywords: chronoamperometry; circadian cycle; cortisol; portable watch.

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Conflict of interest statement

Financial & competing interests disclosure S Prasad has a significant interest in Enlisense LLC, a company that may have a commercial interest in the results of this research and technology. The potential individual conflict of interest has been reviewed and managed by The University of Texas at Dallas and played no role in the study design; in the collection, analysis and interpretation of data; in the writing of the report, or in the decision to submit the report for publication. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed. No writing assistance was utilized in the production of this manuscript.

Figures

Figure 1.
Figure 1.. CortiWatch electrode design and functionalization chemistry.
(A) Picture of the CortiWatch sensor displayed next to a penny for size reference. Electrochemistry schematic of the electrode functionalization. (B) FTIR spectrum displaying absorbance peaks related to linker and capture probe (antibody) group for CortiWatch platform. CE: Counter electrode; FTIR: Fourier transform infrared spectroscopy; RE: Reference electrode; WE: Working electrode.
Figure 2.
Figure 2.. CortiWatch Device render and block diagram.
(A) Device rendering displaying different components inside the CortiWatch. (B) Block diagram of the circuit used in CortiWatch. ADC: Analog to digital converter; ARM: Advanced RISC Machine; DAC: Digital to analog converter; DC: Direct current; PGA: Programmable gain amplifier; RISC: Reduced instruction set computing.
Figure 3.
Figure 3.. Benchtop sensing response for cortisol.
(A) Chronoamperogram for cortisol doses ranging from 1 pg/ml to 100 ng/ml in synthetic sweat pH 6 performed on benchtop. (B) Extracted negative chronoamperogram for benchtop cortisol studies displaying dose dependent changes. (C) Extracted chronoamperometry current peaks for cortisol doses in synthetic sweat for test performed on CortiWatch. SS: Synthetic sweat.
Figure 4.
Figure 4.. Sensor response validation.
Validation of sensor's cortisol response using (A) ELISA and (B) Electrochemical Impedance spectroscopy for varying cortisol dose concentrations. EIS: Electrochemical impedance spectroscopy.
Figure 5.
Figure 5.. On-body testing using CortiWatch.
(A) Wearable case design for CortiWatch placed on human subject during trials. (B) Real-time circadian profile for human participant generated using CortiWatch for a 9 h time period.
See this image and copyright information in PMC

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