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PEDOT-S quenches the fluorescent dye Nile Red in the P-S@dioct:DOPC structures. a) When the P-S@dioct:DOPC structures are prepared together with Nile Red, the fluorescence is significantly decreased compared with reference DOPC liposomes stained with Nile Red but without PEDOT-S@dioctyl-ammonium. b) The fluorescence decay of Nile Red is quicker (multiexponential) for P-S@dioct:DOPC structures than the monoexponential decay for Nile Red in DOPC liposomes (τ = 3.5 ns), which indicates quenching. Excitation wavelength was 550 nm in a) and 500 nm in b).
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Electrical interfaces between biological cells and man-made electrical devices exist in many forms, but it remains a challenge to bridge the different mechanical and chemical environments of electronic conductors (metals, semiconductors) and biosystems. Here we demonstrate soft electrical interfaces, by integrating the metallic polymer PEDOT-S into...
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... 48,49 . In lipid environments, Nile Red emits light with a maximum at about 630 nm and changes of its fluorescence due to the presence of PEDOT-S was analyzed. With an excitation wavelength of 550 nm, we observed a strong reduction of fluorescence in Nile Red-stained liposomes that were prepared together with PEDOT-S@dioctylammo- nium complexes (Fig. 4a). We also measured the lifetime of the fluorescence using excitation at 500 nm, and noted a change from a monoexponential decay (τ = 3.5 ns) to a faster multiexponential decay, in agreement with the reduced quantum yield of fluorescence (Fig. 4b). The fast quenching observed may be caused by excitation quenching of the Nile Red emission ...
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... in Nile Red-stained liposomes that were prepared together with PEDOT-S@dioctylammo- nium complexes (Fig. 4a). We also measured the lifetime of the fluorescence using excitation at 500 nm, and noted a change from a monoexponential decay (τ = 3.5 ns) to a faster multiexponential decay, in agreement with the reduced quantum yield of fluorescence (Fig. 4b). The fast quenching observed may be caused by excitation quenching of the Nile Red emission by interaction with the metallic PEDOT-S at short distance 50 or by the Förster resonance energy transfer mechanism. The short distance required between Nile Red and PEDOT-S for both these mechanisms means that PEDOT-S has to be closely ...
Citations
... Herein we employ poly(4-(2,3-dihydrothieno[3,4b]-[1,4]dioxin-2-yl-methoxy)-1-butanesulfonic acid (PEDOT-S) 56,57 as a conductive polymer to functionalize hybrids between gelatin and lysozyme protein nanofibrils (LPNF). PEDOT-S has been investigated as a functionalization agent for PNFs, 53−55 DNA, 58 and liposomes 59 to prepare electrically conductive hybrids materials. ...
Gelatin is an excellent gelling agent and is widely employed for hydrogel formation. Because of the poor mechanical properties of gelatin when dry, gelatin-aerogels are comparatively rare. Herein we demonstrate that protein nanofibrils can be employed to improve the mechanical properties of gelatin aerogels, and the materials can moreover be functionalized with a an electrically conductive polyelectrolyte resulting in formation of an elastic electrically conductive aerogel that can be employed as a piezoresistive pressure sensor. The aerogel sensor shows a good linear relationship in a wide pressure range (1.8–300 kPa) with a sensitivity of 1.8 kPa–1. This work presents a convenient way to produce electrically conductive elastic aerogels from low-cost protein precursors.
... Moreover, the use of both monoalkylated and dialkylated ammonium counterions also enabled evaluation of the effect of counterion steric hindrance on the electrochemical performance of the two polymers. Starting from PEDOT-S, PEDOT-S:(Nonyl)-NH 3 and PEDOT-S:(Oct) 2 NH 2 were obtained by a counterion exchange-precipitation method, 212 in which precipitation of the counterion exchanged materials provided a kinetic driving force to shift the equilibrium reaction toward the products. Following counterion exchange, the resulting polymers were no longer water-soluble but could instead be processed effectively through the use of organic solvent mixtures. ...
Electronically interfacing with the nervous system for the purposes of health diagnostics and therapy, sports performance monitoring, or device control has been a subject of intense academic and industrial research for decades. This trend has only increased in recent years, with numerous high-profile research initiatives and commercial endeavors. An important research theme has emerged as a result, which is the incorporation of semiconducting polymers in various devices that communicate with the nervous system─from wearable brain-monitoring caps to penetrating implantable microelectrodes. This has been driven by the potential of this broad class of materials to improve the electrical and mechanical properties of the tissue-device interface, along with possibilities for increased biocompatibility. In this review we first begin with a tutorial on neural interfacing, by reviewing the basics of nervous system function, device physics, and neuroelectrophysiological techniques and their demands, and finally we give a brief perspective on how material improvements can address current deficiencies in this system. The second part is a detailed review of past work on semiconducting polymers, covering electrical properties, structure, synthesis, and processing.
... Previous studies on self-doped CPEs have shown their impact on the opening of voltage-gated K ion channels. 351 However, to date, it is unknown whether such an effect would exist for K channels in bacteria. ...
... Most lipid molecules have relative permittivity values around 1-3. 39 Lipid doping could produce more conductive lipid bilayers, and researchers have shown that organic semiconducting materials or conductive polymers can be doped into lipid bilayer membranes, resulting in higher relative permittivity values; 36,42,43 two such examples include conjugating oligo-electrolytes into microbial membranes and inserting PEDOT-S into supported lipid membranes. 44, 45 An alternative approach for modulating the permittivity of the inner lipid region is to include a thin film of water in-between lipid layers, as carried out by Schibel et al. 46 This approach would enable the realization of the lipid composition lipid(1, 80, 1), thus maximizing gating efficiency. ...
Carbon nanotube porins (CNTPs) are biomimetic membrane channels that demonstrate excellent biocompatibility and unique water and ion transport properties. Gating transport in CNTPs with external voltage could increase control over ion flow and selectivity. Herein, we used continuum modeling to probe the parameters that enable and further affect CNTP gating efficiency, including the size and composition of the supporting lipid membrane, slip flow in the carbon nanotube, and the intrinsic electronic properties of the nanotube. Our results show that the optimal gated CNTP device consists of a semiconducting CNTP inserted into a small membrane patch containing an internally conductive layer. Moreover, we demonstrate that the ionic transport modulated by gate voltages is controlled by the charge distribution along the CNTP under the external gate electric potential. The theoretical understanding developed in this study offers valuable guidance for the design of gated CNTP devices for nanofluidic studies, novel biomimetic membranes, and cellular interfaces in the future.
n‐Type organic electrochemical transistors (OECTs) are fundamental building blocks of biosensors and complementary circuits along with p‐type. Yet, their development has been lagging behind their p‐type counterparts since first emergence in 2016. The key component of an OECT is the channel material, which is an organic mixed ionic‐electronic conductor (OMIEC), that dictates the function and performance of the OECT via interactions with electrolyte ions. OMIECs of OECTs are benchmarked by the product of charge‐carrier mobility (μ) and volumetric capacitance (C*), μC*. Significant progress is made for the development of novel n‐type OMIECs, with best μC* now reaching 180 F cm⁻¹ V⁻¹ s⁻¹. This review elucidates such material development progress of n‐type OMIECs with emphases on the underlying molecular design strategies and structure‐property relationships. Furthermore, the operational stability of channel materials and the applications of n‐type OECTs are also discussed to offer readers a comprehensive view of the field. Finally, current limitations are discussed along with outlook.
Conjugated polymers are enabling the development of flexible bioelectronics, largely driven by their organic nature which facilitates modification and tuning to suit a variety of applications. As organic semiconductors, conjugated polymers require a dopant to exhibit electrical conductivity, which in physiological conditions can result in dopant loss and thereby deterioration in electronic properties. To overcome this challenge, “self‐doped” and self‐acid‐doped conjugated polymers having ionised pendant groups covalently bound to their backbone are being developed. The ionised group in a “self‐doped” polymer behaves as the counterion that mainatins electroneutrality, while an external dopant is required to induce charge transfer. The ionised group in a self‐acid‐doped polymer induces charge transfer and behaves as the counterion balancing the charges. Despite their doping processes being different, the two terms, self‐doped and self‐acid‐doped, are often used interchangeably in the literature. This review highlights the differences in the doping mechanisms of self‐doped and self‐acid‐doped polymers, and proposes that the term “self‐doped” should be replaced by “self‐compensated”, while reserving the term self‐acid‐doped for polymers that are intrinsically doped without the need of an external dopant. This is followed by a summary of examples of self‐acid‐doping in bioelectronics, highlighting their stability in the conductive state under physiological conditions.
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Recent studies willingly agree that conducting polymers (CPs) are attractive materials for biomedical engineering purposes, mainly because of their unique physicochemical characteristics combining electrical conductivity and high biocompatibility. Nevertheless, the applicability of CPs is restricted by their limited stability under physiological conditions, associated with a decrease in electrical conductivity upon dedoping. Accordingly, modifying chemical structure of CPs to exhibit a self-doping effect seems to be an appealing approach aimed to enhance their functionality. The aim of this review is to provide a current state-of-the-art in the research concerning self-doped CPs, particularly those with potential biomedical applications. After presenting a library of available structure modifications, we describe their physicochemical characteristics, focusing on achievable conductivities, electrochemical, optical and mechanical behaviour, as well as biological properties. To highlight high applicability of self-doped CPs in biomedical engineering, we elaborate on biomedical areas benefiting most from using this type of conducting materials.
The ongoing SARS-CoV-2 pandemic has emphasized the importance of technologies to rapidly detect emerging pathogens and understand their interactions with hosts. Platforms based on the combination of biological recognition and electrochemical signal transduction, generally termed bioelectrochemical platforms, offer unique opportunities to both sense and study pathogens. Improved bio-based materials have enabled enhanced control over the biotic-abiotic interface in these systems. These improvements have generated platforms with the capability to elucidate biological function rather than simply detect targets. This advantage is a key feature of recent bioelectrochemical platforms applied to infectious disease. Here, we describe developments in materials for bioelectrochemical platforms to study and detect emerging pathogens. The incorporation of host membrane material into electrochemical devices has provided unparalleled insights into the interaction between viruses and host cells, and new capture methods have enabled the specific detection of bacterial pathogens, such as those that cause secondary infections with SARS-CoV-2. As these devices continue to improve through the merging of hi-tech materials and biomaterials, the scalability and commercial viability of these devices will similarly improve.
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