Dopant-Dependent Electrical and Biological Functionality of PEDOT in Bioelectronics

Interface-Mediated Neurogenic Signaling: The Impact of Surface Geometry and Chemistry on Neural Cell Behavior for Regenerative and Brain-Machine Interfacing Applications

Nanomaterial advancements have driven progress in central and peripheral nervous system applications such as tissue regeneration and brain-machine interfacing. Ideally, neural interfaces with native tissue shall seamlessly integrate, a process that is often mediated by the interfacial material properties. Surface topography and material chemistry are significant extracellular stimuli that can influence neural cell behavior to facilitate tissue integration and augment therapeutic outcomes. This review characterizes topographical modifications, including micropillars, microchannels, surface roughness, and porosity, implemented on regenerative scaffolding and brain-machine interfaces. Their impact on neural cell response is summarized through neurogenic outcome and mechanistic analysis. The effects of surface chemistry on neural cell signaling with common interfacing compounds like carbon-based nanomaterials, conductive polymers, and biologically inspired matrices are also reviewed. Finally, the impact of these extracellular mediated neural cues on intracellular signaling cascades is discussed to provide perspective on the manipulation of neuron and neuroglia cell microenvironments to drive therapeutic outcomes.

Dual-Site Biomacromolecule Doped Poly(3, 4-Ethylenedioxythiophene) for Bosting Both Anticoagulant and Electrochemical Performances

Poly(3, 4-ethylenedioxythiophene) (PEDOT) as a new generation of intelligent conductive polymers, is attracting much attention in the field of tissue engineering. However, its water dispersibility, conductivity, and biocompatibility are incompatible, which limit its further development. In this work, biocompatible electrode material of PEDOT doped with sodium sulfonated alginate (SS) which contains two functional groups of sulfonic acid and carboxylic acid per repeat unit of the macromolecule. The as dual-site doping strategy simultaneously boosts anticoagulant and electrochemical performances, for example, good hydrophilicity (water contact angle of 59.40°), well dispersibility (dispersion solution unstratified in 30 days), high conductivity (4.45 S m-1), and enhanced anticoagulant property (extended activated partial thrombin time value of 59.0 s), forming an adjustable PEDOT: biomacromolecule interface; this fills the technical gap of implantable bioelectronics in terms of coagulation and thrombosis risk. At the same time, the assembled all-in-one supercapacitor with anticoagulant properties is prepared by PEDOT: sodium sulfonated alginate as electrode material and sodium alginate hydrogel as electrolyte layer. The dual-site doping strategy provides a new opinion for the design and optimization of functional conductive polymers and its applications in implantable energy storage fields.

PEDOT:Nafion for Highly Efficient Supercapacitors

Supercapacitors offer notable properties as energy storage devices, providing high power density and fast charging and discharging while maintaining a long cycling lifetime. Although poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate) (PEDOT/PSS) has become a gold standard among organic electronics materials, researchers are still investigating ways to further improve its capacitive characteristics. In this work, we introduced Nafion as an alternative polymeric counterion to PSS to form highly capacitive PEDOT/Nafion; its advantageous supercapacitive properties were further improved by treatment with either dimethyl sulfoxide or ethylene glycol. Accordingly, electrochemical characterization of PEDOT/Nafion films revealed their high areal capacitance (22 mF cm-2 at 10 mV/s) and low charge transfer resistance (∼380 Ω), together with excellent volumetric capacitance (74 F cm-3), Coulombic efficiency (99%), and an energy density of 23.1 ± 1.5 mWh cm-3 at a power density of 0.5 W cm-3, resulting from a more effective ion diffusion inside the conductive film, as confirmed by the results of spectroscopic studies. A proof-of-concept symmetric supercapacitor based on PEDOT/Nafion was characterized with a specific capacitance of approximately 15.7 F g-1 and impressive long-term stability (Coulombic efficiency ∼99% and capacitance ∼98.7% after 1000 charging/discharging cycles), overperforming the device based on PEDOT/PSS.

Antibacterial coatings for electroceutical devices based on PEDOT decorated with gold and silver particles

The continuous progression in the field of electrotherapies implies the development of multifunctional materials exhibiting excellent electrochemical performance and biocompatibility, promoting cell adhesion, and possessing antibacterial properties. Since the conditions favouring the adhesion of mammalian cells are similar to conditions favouring the adhesion of bacterial cells, it is necessary to engineer the surface to exhibit selective toxicity, i.e., to kill or inhibit the growth of bacteria without damaging mammalian tissues. The aim of this paper is to introduce a surface modification approach based on a subsequent deposition of silver and gold particles on the surface of a conducting polymer, poly(3,4-ethylenedioxythiophene) (PEDOT). The resulting PEDOT-Au/Ag surface is found to possess optimal wettability, roughness, and surface features making it an excellent platform for cell adhesion. By depositing Ag particles on PEDOT surface decorated with Au particles, it is possible to reduce toxic effects of Ag particles, while maintaining their antibacterial activity. Besides, electroactive and capacitive properties of PEDOT-Au/Ag account for its applicability in various electroceutical therapies.

Biodegradable Scaffolds for Vascular Regeneration Based on Electrospun Poly(L-Lactide-co-Glycolide)/Poly(Isosorbide Sebacate) Fibers

Vascular regeneration is a complex process, additionally limited by the low regeneration potential of blood vessels. Hence, current research is focused on the design of artificial materials that combine biocompatibility with a certain rate of biodegradability and mechanical robustness. In this paper, we have introduced a scaffold material made of poly(L-lactide-co-glycolide)/poly(isosorbide sebacate) (PLGA/PISEB) fibers fabricated in the course of an electrospinning process, and confirmed its biocompatibility towards human umbilical vein endothelial cells (HUVEC). The resulting material was characterized by a bimodal distribution of fiber diameters, with the median of 1.25 µm and 4.75 µm. Genotyping of HUVEC cells collected after 48 h of incubations on the surface of PLGA/PISEB scaffolds showed a potentially pro-angiogenic expression profile, as well as anti-inflammatory effects of this material. Over the course of a 12-week-long hydrolytic degradation process, PLGA/PISEB fibers were found to swell and disintegrate, resulting in the formation of highly developed structures resembling seaweeds. It is expected that the change in the scaffold structure should have a positive effect on blood vessel regeneration, by allowing cells to penetrate the scaffold and grow within a 3D structure of PLGA/PISEB, as well as stabilizing newly-formed endothelium during hydrolytic expansion.

Conducting Polymers as Versatile Tools for the Electrochemical Detection of Cancer Biomarkers

The detection of cancer biomarkers has recently become an established method for the early diagnosis of cancer. The sensitive analysis of specific biomarkers can also be clinically applied for the determination of response to treatment and monitoring of disease progression. Because of the ultra-low concentration of cancer biomarkers in body fluids, diagnostic tools need to be highly sensitive and specific. Conducting polymers (CPs) are particularly known to exhibit numerous features that enable them to serve as excellent materials for the immobilization of biomolecules and the facilitation of electron transfer. Their large surface area, porosity, and the presence of functional groups provide CPs with binding sites suitable for capturing biomarkers, in addition to their sensitive and easy detection. The aim of this review is to present a comprehensive summary of the available electrochemical biosensors based on CPs and their composites for the ultrasensitive detection of selected cancer biomarkers. We have categorized the study based on different types of targeted biomarkers such as DNAs, miRNAs, proteins, enzymes, neurotransmitters and whole cancer cells. The sensitivity of their detection is enhanced by the presence of CPs, providing a limit of detection as low as 0.5 fM (for miRNA) and 10 cells (for the detection of cancer cells). The methods of multiplex biomarker detection and cell capture are indicated as the most promising category, since they furnish more accurate and reliable results. Ultimately, we discuss the available CP-based electrochemical sensors and promising approaches for facilitating cancer diagnosis and treatment.

Strategies for interface issues and challenges of neural electrodes

Neural electrodes, as a bridge for bidirectional communication between the body and external devices, are crucial means for detecting and controlling nerve activity. The electrodes play a vital role in monitoring the state of neural systems or influencing it to treat disease or restore functions. To achieve high-resolution, safe and long-term stable nerve recording and stimulation, a neural electrode with excellent electrochemical performance (e.g., impedance, charge storage capacity, charge injection limit), and good biocompatibility and stability is required. Here, the charge transfer process in the tissues, the electrode-tissue interfaces and the electrode materials are discussed respectively. Subsequently, the latest research methods and strategies for improving the electrochemical performance and biocompatibility of neural electrodes are reviewed. Finally, the challenges in the development of neural electrodes are proposed. It is expected that the development of neural electrodes will offer new opportunities for the evolution of neural prosthesis, bioelectronic medicine, brain science, and so on.

Recent advances in the aqueous applications of PEDOT

Water is ubiquitous in life - from making up the majority of the Earth's surface (by area) to over half of the human body (by weight). It stands to reason that materials are likely to contact water at some point during their lifetime. In the specific case of sensors however, there is a need to consider materials that display stable function while immersed in aqueous applications. This mini-review will discuss the most recent advances (2018 to 2021) in the application of the conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) in aqueous environments. At its heart, the use of PEDOT in aqueous applications relies on nanoscale understanding and/or nanoengineered structures and properties. This enables their use in water-based settings such as within the human body or buried in agricultural soils.

Guidelines for a Morphometric Analysis of Prokaryotic and Eukaryotic Cells by Scanning Electron Microscopy

The invention of a scanning electron microscopy (SEM) pushed the imaging methods and allowed for the observation of cell details with a high resolution. Currently, SEM appears as an extremely useful tool to analyse the morphology of biological samples. The aim of this paper is to provide a set of guidelines for using SEM to analyse morphology of prokaryotic and eukaryotic cells, taking as model cases Escherichia coli bacteria and B-35 rat neuroblastoma cells. Herein, we discuss the necessity of a careful sample preparation and provide an optimised protocol that allows to observe the details of cell ultrastructure (≥ 50 nm) with a minimum processing effort. Highlighting the versatility of morphometric descriptors, we present the most informative parameters and couple them with molecular processes. In this way, we indicate the wide range of information that can be collected through SEM imaging of biological materials that makes SEM a convenient screening method to detect cell pathology.