Abstract
This study examines the use of a conductive carbon fiber to construct a flexible biosensing platform for monitoring biomarkers in sweat. Cortisol was chosen as a model analyte. Functionalization of the conductive carbon yarn (CCY) with ellipsoidal Fe2O3 has been performed to immobilize the antibodies specific to cortisol. 1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) and N-Hydroxysuccinimide (NHS) chemistry has been used to immobilize the antibodies onto the Fe2O3 modified CCY. Crystallinity, structure, morphology, flexibility, surface area, and elemental analysis were studied using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, Field emission scanning electron microscopy with energy dispersive X-ray spectroscopy (FE-SEM/EDS) and Brunauer–Emmett–Teller (BET) analysis. Mechanical properties of the fiber such as tensile strength, young’s modulus have also been investigated. Under optimal parameters, the fabric sensor exhibited a good linearity (r2 = 0.998) for wide a linear range from 1 fg to 1 μg with a detection limit of 0.005 fg/mL for the sensitive detection of cortisol. Repeatability, reliability, reproducibility, and anti-interference properties of the current sensor have been investigated. Detection of cortisol levels in human sweat samples has also been investigated and the results were validated with commercial chemiluminescence immunoassay (CLIA) method.
Highlights
Analysis of biomarker levels in sweat is increasingly important as it would give real time information about human performance, health and wellbeing
For Fe2O3/conductive carbon yarn (CCY), the signature patterns for carbon yarn at 25.9° (002) and several new diffraction peaks at 24.2°, 33.2°, 35.86°, 40.96° and 54.13°corresponding to (012), (104), (110), (113) and (116) planes, respectively were observed which are consistent with the standard X-ray diffraction (XRD) patterns of rhombohedral α-Fe2O3 (JCPDS No 84-0309)
In order to investigate the interaction between Fe2O3 and CCY, the Fourier transform infrared spectroscopy (FT-IR) spectrum has been performed
Summary
Analysis of biomarker levels in sweat is increasingly important as it would give real time information about human performance, health and wellbeing. Methods used to detect cortisol includes, fluorescence assay calorimetric[13], High performance liquid chromatography (HPLC)[14], reverse phase chromatography[15], enzyme linked immunosorbent assays (ELISA)[16,17], competitive protein-binding assays[18,19] and surface plasmon resonance biosensor (SPR)[20] They suffer from long detection time, lengthy sample preparation time and analysis, low sensitivity and cost. Novel electrochemical immunosensor, aptamer sensor and imprinted sensor[21,22] method has been developed to detect cortisol owing to their fast analysis speed, high sensitivity, and low cost[7,23,24] These sensors involve the use of traditional Au metallic disk, glassy carbon electrode (GCE), metal electrodes, metallic fibers or printed electrodes. A novel design of the structure with Fe2O3 nanostructure coated on flexible carbon yarn substrate is highly desirable to achieve the flexible binder free electrode with high electrochemically sensing performance[36]
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