Sensitive Detection of Sweat Cortisol Using an Organic Electrochemical Transistor Featuring Nanostructured Poly(3,4-Ethylenedioxythiophene) Derivatives in the Channel Layer.

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 (R2 = 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.

Molecular and nano structures of chiral PEDOT derivatives influence the enantiorecognition of biomolecules. In silico analysis of chiral recognition.

In this study we investigated the synergistic effects of the chirality (molecular structure) and surface morphology (nanostructure) of a newly designed sensing platform for the stereoselective recognition of biomolecules. We synthesized 3,4-ethylenedioxythiophene monomers presenting an OH functional group on the side chain (EDOT-OH) with either R or S chirality and then electropolymerized them in a template-free manner to engineer poly(EDOT-OH) nanotubes and smooth films with R or S chirality. We used a quartz crystal microbalance (QCM) to examine the differential binding of fetal bovine serum, RGD peptide, insulin, and (R)- and (S)-mandelic acid (MA) on these chiral polymeric platforms. All of these biomolecules bound stereoselectively and with greater affinity toward the nanotubes than to the smooth films. The sensitive chiral recognition of (S)- and (R)-MA on the (R)-poly(EDOT-OH) nanotube surface occurred with the highest chiral discrepancy ratio of 1.80. In vitro experiments revealed a greater degree of protein deposition from MCF-7 cells on the chiral nanotube surfaces. We employed ab initio molecular dynamics simulations and density functional theory calculations to investigate the mechanism underlying the sensitive chiral recognition between the chiral sensing platforms and the chiral analyte molecules.

Ultrathin Cell-Membrane-Mimic Phosphorylcholine Polymer Film Coating Enables Large Improvements for In†Vivo Electrochemical Detection.

Resisting biomolecule adsorption onto the surface of brain-implanted microelectrodes is a key issue for in vivo monitoring of neurochemicals. Herein, we demonstrate that an ultrathin cell-membrane-mimic film of ethylenedioxythiophene tailored with zwitterionic phosphorylcholine (EDOT-PC) electropolymerized onto the surface of a carbon fiber microelectrode (CFE) not only resists protein adsorption but also maintains the sensitivity and time response for in vivo monitoring of dopamine (DA). As a consequence, the as-prepared PEDOT-PC/CFEs could be used as a new reliable platform for tracking DA in vivo and would help understand the physiological and pathological functions of DA.

Palladium-catalyzed direct C-H arylations of dioxythiophenes bearing reactive functional groups: a step-economical approach for functional π-conjugated oligoarenes.

A Pd-catalyzed single-step C-H arylation of dioxythiophene derivatives bearing unprotected reactive functional groups (-OH, -COOH, -N3) in a phosphine-free manner has been developed. Various dioxythiopene-based oligoarenes with extended π-conjugation are obtained with good yields (up to 90%). These oligoarenes display suitable optical properties (absorption and emission maxima, quantum yields) and contain reactive functional groups suitable for further conjugations with bioactive molecules. This new methodology is step economical (fewer synthetic steps) and environmentally friendly (no toxic metal-containing by-products) and the oligoarenes synthesized are potentially applicable for bio-labeling, bioimaging, and biosensing.

Nanoscale analysis of a functionalized polythiophene surface by adhesion mapping.

Functionalized ethylenedioxythiophene (EDOT) monomers, hydroxymethyl EDOT (EDOT-OH), and zwitterionic phosphorylcholine EDOT (EDOT-PC) were electropolymerized to prepare the homopolymers poly(EDOT-OH) and poly(EDOT-PC), and mixtures of these monomers were used to produce the copolymer poly(EDOT-OH)-co-poly(EDOT-PC). Force-extension-curve-based atomic force microscopy (AFM) was utilized to analyze the surfaces of the films. The PEDOT-OH film yielded force-extension curves for short stretching, and the PEDOT-PC film yielded curves for long stretching. A dendron-modified AFM tip with anthracene groups tethered at the end resulted in adhesion maps with the highest contrast. The analytical data for the copolymer films correlated with the corresponding monomer composition, and the maps revealed that the average size for the copolymer nanodomains ranged from 10-14 nm. This approach can be applied to studies aimed at understanding the surface structure of other relevant polymers and copolymers at the nanoscale level.

3D bioelectronic interface: capturing circulating tumor cells onto conducting polymer-based micro/nanorod arrays with chemical and topographical control.

The three-dimensional (3D) poly(3,4-ethylenedioxythiophene) (PEDOT)-based bioelectronic interfaces (BEIs) with diverse dimensional micro/nanorod array structures, varied surface chemical pro-perties, high electrical conductivity, reversible chemical redox switching, and high optical transparency are used for capturing circulating tumor cells (CTCs). Such 3D PEDOT-based BEIs can function as an efficient clinical diagonstic and therapeutic platform.

Detection of SARS-CoV-2 Spike Protein Using Micropatterned 3D Poly(3,4-Ethylenedioxythiophene) Nanorods Decorated with Gold Nanoparticles.

The sensitivity and fabrication process of the detection platform are important for developing viral disease diagnosis. Recently, the outbreak of SARS-CoV-2 compelled us to develop a new detection platform to control such diseases in the future. We present an electrochemical-based assay that employs the unique properties of gold nanoparticles (AuNPs) deposited on 3D carboxyl-functionalized poly(3,4-ethylenedioxythiophene) (PEDOTAc) nanorods for specific and sensitive detection of SARS-CoV-2 spike protein (S1). The 3D-shaped PEDOTAc nanorods offer an ample surface area for receptor immobilization grown on indium-tin oxide surfaces through transfer-printing technology. Characterization via electrochemical, fluorescence, X-ray photoelectron spectroscopy, and scanning electron microscopy techniques confirmed the structural and morphological properties of the AuNPs-decorated PEDOTAc. In contrast to antibody-based assays, our platform employs ACE2 receptors for spike protein binding. Differential pulse voltammetry records current responses, showing linear sensitivity from 100 ng to 10 pg/mL of S1. In addition, the SARS-CoV-2 assay (CoVPNs) also exhibited excellent selectivity against nonspecific target proteins (H9N2, IL-6, and Escherichia coli). Furthermore, the developed surface maintained good stability for up to 7 consecutive days without losing performance. The results provide new insight into effective 3D conductive nanostructure formation, which is promising in the development of versatile sensory devices.

Nano-On-Nano: Responsive Nanosubstrate-Mediated Liposome Delivery with High Cellular Uptake Efficiency.

Efficiently delivering liposomal content to cells in a relatively uniform dose and patterned fashion, especially bypassing the degradative endocytosis pathway, is an important technology in cell culture and potentially to tissue engineering that still remains challenging. We developed a "nano-on-nano" platform technology that consists of the following three material features: (1) high density silicon nanopillars to create a pseudo-3-dimensional nanoenvironment for cell culturing, (2) thermoresponsive polymer grafted onto silicon nanopillars to form a responsive nanosubstrate, and (3) immobilized liposomes using a biotin-streptavidin-biotin conjugation. The working principle is that the liposomes are detached for cellular uptake upon thermal stimulation and high local liposome concentration between the cells and substrates drives the cellular uptake with nonendocytic pathways. Cryo-EM images confirms that liposomes are attached to form liposome-warped nanopillars. Upon thermal stimulation, an 8 times higher increase in the liposomal fluorescence intensity is observed compared to the conventional solution-phase liposome delivery, indicating that high local concentration drives liposome uptake with greater efficiency. Moreover, preliminary mechanistic studies reveal that these liposomes are taken up by nonendocytic pathways. The ability of our nano-on-nano delivery system that achieves efficient dose-uniform cellular delivery can open a unique era in cell and tissue engineering by controlling cell behaviors with the delivery of bioactive ingredient-loaded liposomes.

Biguanide- and Oligo(Ethylene Glycol)-Functionalized Poly(3,4-Ethylenedioxythiophene): Electroactive, Antimicrobial, and Antifouling Surface Coatings.

The challenge of infectious diseases remains a critical concern to the global public health. Recently, it is common to encounter touch-screen electronic devices everywhere to access services. The surface of such devices may easily get contaminated by an infected person, which leads to transmission of infectious diseases between individuals. Moreover, the challenge is complicated by surgical infections from implantable biomedical devices. Such problems can be minimized by the use of long-term active antimicrobial surface coatings. We present herein the preparation of novel electroactive antimicrobial surface coatings through the covalent attachment of the biguanide moiety onto 3,4-ethylenedioxythiophene (EDOT). The biguanide-functionalized EDOT (EDOT-BG) was thus electropolymerized on different substrates to give the corresponding poly(EDOT-BG) polymer. The poly(EDOT-BG) polymer showed an excellent bactericidal efficiency (∼92% bacterial death) and excellent biocompatibility with mammalian cells. Furthermore, the antimicrobial EDOT-BG was electro-copolymerized with antifouling tetra ethylene glycol functionalized-EDOT (EDOT-EG4) to give a multifunctional poly(EDOT-EG4-co-EDOT-BG) copolymer. The poly(EDOT-EG4-co-EDOT-BG) copolymer showed excellent resistance to protein adsorption and mammalian/bacterial cell binding without losing its bactericidal efficiency. These novel materials can be applied to domestic and bioelectronic devices to minimize infectious diseases.

Smart Thermoresponsive Electrospun Nanofibers with On-Demand Release of Carbon Quantum Dots for Cellular Uptake.

Developing a smart responsive surface for on-demand delivery of organic, inorganic, and biological cargo in vitro cellular uptake is always in constant demand. Herein, we present carbon quantum dot (CQD)-loaded (poly(N-isopropylacrylamide) (PNIPAAm)/poly(methyl methacrylate (PMMA)) blend nanofiber sheets having a thermoresponsive nature. As a model cargo, fluorescent CQDs are used for the demonstration of the on-demand delivery mechanism. In addition, a thermoresponsive nature is produced by the PNIPAAm polymer in the nanofiber matrix while the PMMA polymer provides extra stability and firmness to the nanofibers against the sudden dissolution of the nanofibers in aqueous media. The synthesis of CQDs and their loading into a blend nanofiber matrix are confirmed using fluorescence spectrophotometry, transmission electron microscopy, and fluorescence microscopy. The morphologies and diameters of the nanofibers are analyzed by scanning electron microscopy. Burst effect analysis proves that 30% (w/w) PNIPAAm-containing nanofibers possess the highest stability with the least dissolution in aqueous media. Thermoresponsiveness of the nanofibers is further confirmed through water contact angle measurements. Quantitative fluorescence results show that more than 80% of loaded CQDs can be released upon thermal stimulation. The fluorescence micrographs reveal that the blend nanofiber sheets can effectively improve the cellular uptake of CQDs by simply increasing the local concentrations via applying thermal stimulation as the released mechanism.

Coupling Lipid Labeling and Click Chemistry Enables Isolation of Extracellular Vesicles for Noninvasive Detection of Oncogenic Gene Alterations.

Well-preserved molecular cargo in circulating extracellular vesicles (EVs) offers an ideal material for detecting oncogenic gene alterations in cancer patients, providing a noninvasive diagnostic solution for detection of disease status and monitoring treatment response. Therefore, technologies that conveniently isolate EVs with sufficient efficiency are desperately needed. Here, a lipid labeling and click chemistry-based EV capture platform ("Click Beads"), which is ideal for EV message ribonucleic acid (mRNA) assays due to its efficient, convenient, and rapid purification of EVs, enabling downstream molecular quantification using reverse transcription digital polymerase chain reaction (RT-dPCR) is described and demonstrated. Ewing sarcoma protein (EWS) gene rearrangements and kirsten rat sarcoma viral oncogene homolog (KRAS) gene mutation status are detected and quantified using EVs isolated by Click Beads and matched with those identified in biopsy specimens from Ewing sarcoma or pancreatic cancer patients. Moreover, the quantification of gene alterations can be used for monitoring treatment responses and disease progression.

Hybrid "Kill and Release" Antibacterial Cellulose Papers Obtained via Surface-Initiated Atom Transfer Radical Polymerization.

Infectious diseases triggered by bacteria cause a severe risk to human health. To counter this issue, surfaces coated with antibacterial materials have been widely used in daily life to kill these bacteria. The substrates enabled with a hybrid kill and release strategy can be employed not only to kill the bacteria but also to wash them using external stimuli (temperature, pH, etc.). Utilizing this concept, we develop thermoresponsive antibacterial-cellulose papers to exhibit hybrid kill and release properties. Thermoresponsive copolymers [p(NIPAAm-co-AEMA)] are grafted on cellulose papers using a surface-initiated atom transfer radical polymerization approach for bacterial debris release. Later for antibacterial properties, silver nanoparticles (AgNPs) are immobilized on thermoresponsive copolymer-grafted cellulose papers using electrostatic interactions. We confirm the thermoresponsive copolymer grafting and AgNP coating by attenuated total reflection Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy. Thermoresponsiveness and reusability of the modified cellulose papers are confirmed through water contact angle measurements. The interaction potency between AgNPs and modified cellulose is validated by inductively coupled plasma atomic emission spectroscopy analysis. Gram-negative bacteria Escherichia coli (E. coli DH5-α) is used to demonstrate antibacterial hybrid kill and release performance. Agar-diffusion testing demonstrates the antibacterial nature of the modified cellulose papers. The fluorescence micrograph reveals that modified cellulose papers can effectively release almost all the dead bacterial debris from their surfaces after thermal stimulus wash. The modified cellulose paper surfaces are expected to have wide applications in the field of exploring more antibacterial and smart surfaces.

Self-Cleaning Cotton Obtained after Grafting Thermoresponsive Poly(N-vinylcaprolactam) through Surface-Initiated Atom Transfer Radical Polymerization.

Although the performance of smart textiles would be enhanced if they could display self-cleaning ability toward various kinds of contamination, the procedures that have been used previously to impart the self-cleaning potential to these functional fabrics (solvent casting, dip coating, spin coating, surface crosslinking) have typically been expensive and/or limited by uncontrollable polymer thicknesses and morphologies. In this paper, we demonstrate the use of atomic transfer radical polymerization for the surface-initiated grafting of poly(N-vinylcaprolactam), a thermoresponsive polymer, onto cotton. We confirmed the thermoresponsiveness and reusability of the resulting fabric through water contact angle measurements and various surface characterization techniques (scanning electron microscopy, atomic force microscopy, Fourier transform infrared spectroscopy). Finally, we validated the self-cleaning performance of the fabric by washing away an immobilized fluorescent protein in deionized water under thermal stimulus. Fluorescence micrographs revealed that, after the fifth wash cycle, the fabric surface had undergone efficient self-cleaning of the stain, making it an effective self-cleaning material. This approach appears to have potential for application in the fields of smart textiles, responsive substrates, and functional fabrics.

Mechanotactic Activation of TGF-ß by PEDOT Artificial Microenvironments Triggers Epithelial to Mesenchymal Transition.

Epithelial to mesenchymal transition (EMT) is integral for cells to acquire metastatic properties, and ample evidence links it to bioorganic framework of the tumor microenvironment (TME). Hydroxymethyl-functionalized 3,4-ethylenedioxythiophene polymer (PEDOT-OH) enables construction of diverse nanotopography size and morphologies and is therefore exploited to engineer organic artificial microenvironments bearing nanodots from 300 to 1000 nm in diameter to understand spatiotemporal EMT regulation by biophysical components of the TME. MCF-7 breast cancer cells are cultured on these artificial microenvironments, and temporal regulation of cellular morphology and EMT markers is investigated. The results show that upon physical stimulation, cells on 300 nm artificial microenvironments advance to EMT and display a decreased extracellular matrix (ECM) protein secretion. In contrast, cells on 500 nm artificial microenvironments are trapped in EMT-imbalance. Interestingly, cells on 1000 nm artificial microenvironments resemble those on control surfaces. Upon further investigation, it is found that EMT induction is triggered via transforming growth factor ß (TGF-ß) and ECM cleaving protein, matrix metalloproteinease-9. Immunostaining EMT proteins highlighted that EMT induction is achieved through attenuation of cell-cell and cell-microenvironment adhesions. The physical stimulation-induced TGF-ß perturbation can have a profound impact on the understanding of tumor-promoting signaling cascades originated by cellular microenvironment.

Synthesis of MOF525/PEDOT Composites as Microelectrodes for Electrochemical Sensing of Dopamine.

Dopamine (DA) is an important neurotransmitter responsible for the functions and activities of multiple systems in human. Electrochemical detection of DA has the advantages of fast analysis and cost-effectiveness, while a regular electrode probe is restricted to laboratory use because the probe size is too large to be suitable for an in vivo or in vitro analysis. In this study, we have developed porphyrin-based metal organic framework (MOF525) and poly(3,4-ethylenedioxythiophene) (PEDOT)-based composites to modify microelectrode for DA detection. Two types of PEDOT monomers with different functional groups were investigated in this study. By varying the monomer ratios, electrolyte concentrations, and electropolymerization temperature, it was found that the PEDOT monomer containing carboxylic group facilitated the formation of regular morphology during the electropolymerization process. The uniform morphology of the PEDOT promoted the electron transmission efficiency in the same direction, while the MOF525 provided a large reactive surface area for electrocatalysis of DA. Thus, the MOF525/PEDOT composite improved the sensitivity-to-noise ratio of DA signaling, where the sensitivity reached 11 nA/µM in a good linear range of 4-100 µM. In addition, porphyrin-based MOF could also increase the selectivity to DA against other common clinical interferences, such as ascorbic acid and uric acid. The as-synthesized microelectrode modified with MOF525/PEDOT in this study exhibited great potential in real time analysis.

Tunable Protein/Cell Binding and Interaction with Neurite Outgrowth of Low-Impedance Zwitterionic PEDOTs.

Zwitterionic poly(3,4-ethylenedioxythiophene) (PEDOT) is an effective electronic material for bioelectronics because it exhibits efficient electrical trade-off and diminishes immune response. To promote the use of zwitterionic PEDOTs in bioelectronic devices, especially for cell alignment control and close electrocoupling, features such as tunable interaction of PEDOTs with proteins/cells and spatially modulating cell behavior are required. However, there is a lack of reliable methods to assemble zwitterionic EDOTs with other functionalized EDOT materials, having different polarities and oxidation potentials, to prepare PEDOTs with the aforementioned surface properties. In this study, we have developed a surfactant-assisted electropolymerization to assemble phosphorylcholine (PC)-functionalized EDOT with other functionalized EDOTs. By adjusting compositions, the interaction of PEDOT copolymers with proteins/cells can be finely tuned; the composition adjustment has an ignorable influence on the impedance of the copolymers. We also demonstrate that the cell-repulsive force generated from PC can spatially guide the neurite outgrowth to form a neuron network at single-cell resolution and greatly enhance the neurite outgrowth by 179%, which is significantly more distinctive than the reported topography effect. We expect that the derived tunable protein/cell interaction and the PC-induced repulsive guidance for the neurite outgrowth can make low-impedance zwitterionic PEDOTs more useful in bioelectronics.

Purification of HCC-specific extracellular vesicles on nanosubstrates for early HCC detection by digital scoring.

We report a covalent chemistry-based hepatocellular carcinoma (HCC)-specific extracellular vesicle (EV) purification system for early detection of HCC by performing digital scoring on the purified EVs. Earlier detection of HCC creates more opportunities for curative therapeutic interventions. EVs are present in circulation at relatively early stages of disease, providing potential opportunities for HCC early detection. We develop an HCC EV purification system (i.e., EV Click Chips) by synergistically integrating covalent chemistry-mediated EV capture/release, multimarker antibody cocktails, nanostructured substrates, and microfluidic chaotic mixers. We then explore the translational potential of EV Click Chips using 158 plasma samples of HCC patients and control cohorts. The purified HCC EVs are subjected to reverse-transcription droplet digital PCR for quantification of 10 HCC-specific mRNA markers and computation of digital scoring. The HCC EV-derived molecular signatures exhibit great potential for noninvasive early detection of HCC from at-risk cirrhotic patients with an area under receiver operator characteristic curve of 0.93 (95% CI, 0.86 to 1.00; sensitivity = 94.4%, specificity = 88.5%).

Electric-field-assisted growth of functionalized poly(3,4-ethylenedioxythiophene) nanowires for label-free protein detection.

The construction of functionalized poly(3,4-ethylenedioxythiophene) (PEDOT) nanowire devices for label-free protein detection is reported. Direct growth/assembly of PEDOT nanowires with carboxylic acid side-chain functional groups (poly(EDOT-COOH)) across the electrode junction is achieved by using an electric-field-assisted method. These functionalized PEDOT nanowire devices show typical depletion-mode p-type field-effect transistor (FET) properties. Upon conjugation with a protein-binding aptamer, the PEDOT nanowire FET devices are used for label-free electronic detection of a target protein of interest. The binding of a positively charged protein causes a substantial decrease in current flow, attributed to the specific interaction between target protein molecules and aptamer-conjugated polymer chains.

Magnetic PEDOT hollow capsules with single holes.

We demonstrate magnetic capsules with high uptake capacity by combining single-hole hydroxyl-functionalized PEDOT hollow spheres and Fe(3)O(4) nanoparticles; potential applications include pollutant removal and controlled drug delivery.

Deprotonation-Induced Conductivity Shift of Polyethylenedioxythiophenes in Aqueous Solutions: The Effects of Side-Chain Length and Polymer Composition.

Deprotonation-induced conductivity shift of poly(3,4-ethylenedixoythiophene)s (PEDOTs) in aqueous solutions is a promising platform for chemical or biological sensor due to its large signal output and minimum effect from material morphology. Carboxylic acid group functionalized poly(Cn-EDOT-COOH)s are synthesized and electrodeposited on microelectrodes. The microelectrodes are utilized to study the effect of carboxylic acid side-chain length on the conductivity curve profiles in aqueous buffer with different pH. The conductivity shifts due to the buffer pH are effected by the length of the carboxylic acid side-chains. The shifts can be explained by the carboxylic acid dissociation property (pKa) at the solid-liquid interface, self-doping effect, and effective conjugation length. Conductivity profiles of poly(EDOT-OH-co-C2-EDOT-COOH) copolymers are also studied. The shifts show linear relationship with the feed monomer composition used in electrochemical polymerization.