In this study, we examined 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. The OECT device featured a bilayer channel confined by a PEDOT:polystyrenesulfonate (PSS) underlayer and a nanostructure-decorated upper layer engineered from the monomers EDOT-COOH and EDOT-EG3 through template-free electrochemical polymerization. This molecular design allowed antibody conjugation using 1-ethyl-3-(3-dimethylaminopropyl)­carbodiimide/N-hydroxysulfosuccinimide coupling through the carboxylic acid side chain, with EDOT-EG3 known to minimize nonspecific binding of biomolecules. We also engineered an OECT device having a channel area without any nanostructures to gain insight into the effect of the nanostructures on cortisol sensing. Our new nanostructure-embedded OECT device facilitated real-time detection of cortisol at concentrations ranging from 1 fg/mL to 1 μg/mL with a detection limit of 0.0088 fg/mL with good linearity (R 2 = 0.9566), in addition to excellent selectivity toward cortisol among other structurally similar interfering compounds and high stability and reproducibility. With its rapid response for the detection of 100 ng/mL cortisol-spiked artificial sweat, this nanostructure-decorated OECT device has potential clinical practicality and utility in wearable sensors for future healthcare applications.

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Although conductive bioelectronic interfaces (BEIs) can allow neural cell culturing while providing electrical stimulation (ES) to the nervous system, there are few simple approaches for the preparation of conductive BEIs with topographical features designed for cell manipulation. In this study, we developed a facile method for fabricating microwrinkled poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) films through spin-coating onto pre-elongated polydimethylsiloxane substrates. The microwrinkles of our PEDOT:PSS films pre-elongated by 20 and 40% had average widths of 6.47 ± 1.49 and 5.39 ± 1.53 μm, respectively. These microwrinkled PEDOT:PSS films promoted the directional ordering of neurite outgrowth of PC12 cells and displayed favorable biocompatibility and outstanding electrochemical properties for long-term ES treatment. When using this BEI platform, the level of PC12 gene expression of Neun was enhanced significantly after 5 days of culturing in differentiation media and under ES, in line with the decreased expression of early phase markers. Therefore, such readily fabricated microwrinkled PEDOT:PSS films are promising candidates for use as BEIs for tissue regenerative medicine.

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