Nanostructures of PEDOT Derivatives Decorated on the Channel Layer of Organic Electrochemical Transistor Influences the Sensitive Detection of Sweat Cortisol. ^[a]

Nanostructures of conducting polymers are versatile candidate for the development of biosensors. Electrochemical polymerization is a simple and efficient technique to engineer such conducting polymer nanostructures as bioelectronics interface (BEI) platform. This study highlights the influence of functionalized poly (3,4-ethylenedioxythiophene) (PEDOT) nanostructures decorated on the channel layer of an organic electrochemical transistor (OECT) for the detection of sweat cortisol-an adrenocorticosteroid stress hormone. Our design of novel OECT cortisol immunosensor highlight an active channel area decorated by poly(EDOT-COOH-co-EDOT-EG3) nanotube embedded upper layer engineered from two monomers such as EDOT-COOH and EDOT-EG3 by template free electrochemical polymerization and PEDOT: polystyrenesulfonate (PSS) under layer for the sensitive detection of sweat cortisol. The molecular design provides an easy access of antibody conjugation by 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide/N-hydroxysulfosuccinimide (EDC/Sulfo-NHS) coupling chemistry through carboxylic acid side chain and EDOT-EG3 is best known to reduce non-specific binding of biomolecules. The electropolymerization parameters were optimized for channel morphology of the OECT device together with the output characteristics and electrical properties of the device, pH of the electrolyte solution and monomers feed ratios prior to the immobilization of anti-cortisol antibody. Cortisol antibody was covalently attached inside the channel layer by EDC/Sulfo-NHS coupling chemistry. OECT device having channel area without any nanostructures were also engineered to get insight into the influence of nano topology of the channel area for enhanced analyte detection. Cortisol antibody immobilization on the channel layer was confirmed by different spectroscopic techniques such as Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and Quartz Crystal Microbalance (QCM) technique. QCM experiments revealed that the polymer nanotube embedded active channel area of the device displayed enhanced immobilization of cortisol antibody compared to the active channel area without any nanostructures. The real time detection of cortisol ranging from 1fg /mL to 1 µg/mL were investigated by the newly engineered OECT device. The OECT cortisol immunosensor embedded with nanotubes on the channel area showed enhanced detection limit of 0.0088 fg/mL with good linearity (R²=0.9566). In addition, the device displayed excellent selectivity to cortisol with the other structurally similar interfering compounds such as cholesterol, corticosterone, prednisolone and cortisone. Predominant selectivity to cortisol was observed for OECT device with nanotube channel layer compared with the OECT device having channel layer without any nanostructures. Moreover, the newly designed OECT cortisol immunosensor showed rapid response towards 100 ng/ mL cortisol spiked artificial sweat, highlighted the clinical practicality of the novel OECT device towards wearable sensors for future healthcare applications.<br/><br/>References<br/><br/>[a] Aerathupalathu Janardhanan, Jayakrishnan; Chen, Ying-Lin; Liu, Chun-Ting; Tseng, Hsueh-Sheng; Wu, Po-I; She, Jia-Wei; Hsiao, Yu-Sheng and Yu, Hsiao-hua, Sensitive Detection of Sweat Cortisol Using an Organic Electrochemical Transistor Featuring Nanostructured Poly(3,4-Ethylenedioxythiophene) Derivatives in the Channel Layer, <b>2022</b>, <i>Anal. Chem.</i> 94, 7584–7593.