Portable biosensor for monitoring cortisol in low-volume perspired human sweat

• Published in: Scientific reports Vol. 7; no. 1; pp. 13312 - 13
• Main Authors: Kinnamon, David, Ghanta, Ramesh, Lin, Kai-Chun, Muthukumar, Sriram, Prasad, Shalini
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 17.10.2017; Nature Publishing Group
• Subjects: 639/166/985; 692/53/2421; 82/1; 9/10; Biosensing Techniques - instrumentation; Biosensing Techniques - methods; Biosensors; Cortisol; Disulfides - chemistry; Electrochemical Techniques - instrumentation; Electrochemical Techniques - methods; Electrochemistry; Electrodes; Hormones; Humanities and Social Sciences; Humans; Hydrocortisone - analysis; Impedance; Instrumentation; Metabolites; Molybdenum - chemistry; Molybdenum disulfide; multidisciplinary; Nanostructures - chemistry; Science; Science (multidisciplinary); Sensors; Spectroscopy; Sweat; Sweat - chemistry
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-017-13684-7

A non-faradaic label-free cortisol biosensor was demonstrated using MoS 2 nanosheets integrated into a nanoporous flexible electrode system. Low volume (1–5 μL) sensing was achieved through use of a novel sensor stack design comprised of vertically aligned metal electrodes confining semi-conductive MoS 2 nanosheets. The MoS 2 nanosheets were surface functionalized with cortisol antibodies towards developing an affinity biosensor specific to the physiological relevant range of cortisol (8.16 to 141.7 ng/mL) in perspired human sweat. Sensing was achieved by measuring impedance changes associated with cortisol binding along the MoS 2 nanosheet interface using electrochemical impedance spectroscopy. The sensor demonstrated a dynamic range from 1–500 ng/mL with a limit of detection of 1 ng/mL. A specificity study was conducted using a metabolite expressed in human sweat, Ethyl Glucuronide. Continuous dosing studies were performed during which the sensor was able to discriminate between four cortisol concentration ranges (0.5, 5, 50, 500 ng/mL) for a 3+ hour duration. Translatability of the sensor was shown with a portable form factor device, demonstrating a comparable dynamic range and limit of detection for the sensor. The device demonstrated a R 2 correlation value of 0.998 when comparing measurements to the reported impedance values of the benchtop instrumentation.