Nano-Micro Letters

Noninvasive Label-Free Detection of Cortisol and Lactate Using Graphene Embedded Screen-Printed Electrode

Satish K. Tuteja1, Connor Ormsby1, Suresh Neethirajan1,*

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Nano-Micro Lett. (2018) 10: 41

First Online: 23 January 2018 (Article)


*Corresponding author. E-mail: sneethir@uoguelph.ca




Fig. 5 a SEM analysis of dual SPE before electrodeposition. b SEM analysis of SPE afterelectroreduction. c High magnification SEM images of electrodeposited e-RGO over the dual SPE. d TEM image of e-RGO. e, f AFM image of e-RGO

A sensitive and specific immunosensor for the detection of the hormones cortisol and lactate in human or animal biological fluids, such as sweat and saliva, was devised using the label-free electrochemical chronoamperometric technique. By using these fluids instead of blood, the biosensor becomes non-invasive and is less stressful to the end-user, who may be a small child or a farm animal. Electro-reduced graphene oxide (e-RGO) was used as a synergistic platform for signal amplification and template for bioconjugation for the sensing mechanism on a screen-printed electrode. The cortisol and lactate antibodies were bioconjugated to the e-RGO using covalent carbodiimide chemistry. Label-free electrochemical chronoamperometric detection was used to analyze the response to the desired bio-molecules over the wide detection range. A detection limit of 0.1 ng mL-1 for cortisol and 0.1 mM for lactate were established and a correlation between concentration and current was observed. A portable, handheld potentiostat assembled with Bluetooth communication and battery operation enables the developed system for point-of-care applications. A sandwich like structure to contain the sensing mechanisms as a prototype were designed to secure the biosensor to skin and use capillary action to draw sweat or other fluids towards the sensing mechanism. Overall, the immunosensor shows remarkable specificity, sensitivity as well as the non-invasive and point-of-care capabilities, allows the biosensor to be used as a versatile sensing platform in both developed and developing countries.



Graphene; Immunosensor; Electrochemical; Screen-printed electrodes; Cortisol sensor

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