The regulation of cell functions electrically using biodegradable polypyrrole–polylactide conductors

Biopolymer hydrogels and synergistic blends for tailored wound healing

Biopolymers have a transformative role in wound repair due to their biocompatibility, ability to stimulate collagen production, and controlled drug and growth factor delivery. This article delves into the biological parameters critical to wound healing emphasizing how combinations of hydrogels with reparative properties can be strategically designed to create matrices that stimulate targeted cellular responses at the wound site to facilitate tissue repair and recovery. Beyond a detailed examination of various biopolymer types and their functionalities in wound dressings acknowledging that the optimal choice depends on the specific wound type and application, this evaluation provides concepts for developing synergistic biopolymer blends to create next-generation dressings with enhanced efficiencies. Furthermore, the incorporation of therapeutic agents such as medications and wound healing accelerators into dressings to enhance their efficacy is examined. These agents often possess desirable properties such as antibacterial activity, antioxidant effects, and the ability to promote collagen synthesis and tissue regeneration. Finally, recent advancements in conductive hydrogels are explored, highlighting their capabilities in treatment and real-time wound monitoring. This comprehensive resource emphasizes the importance of optimizing ingredient efficiency besides assisting researchers in selecting suitable materials for personalized wound dressings, ultimately leading to more sophisticated and effective wound management strategies.

Bioelectronics for electrical stimulation: materials, devices and biomedical applications

Bioelectronics is a hot research topic, yet an important tool, as it facilitates the creation of advanced medical devices that interact with biological systems to effectively diagnose, monitor and treat a broad spectrum of health conditions. Electrical stimulation (ES) is a pivotal technique in bioelectronics, offering a precise, non-pharmacological means to modulate and control biological processes across molecular, cellular, tissue, and organ levels. This method holds the potential to restore or enhance physiological functions compromised by diseases or injuries by integrating sophisticated electrical signals, device interfaces, and designs tailored to specific biological mechanisms. This review explains the mechanisms by which ES influences cellular behaviors, introduces the essential stimulation principles, discusses the performance requirements for optimal ES systems, and highlights the representative applications. From this review, we can realize the potential of ES based bioelectronics in therapy, regenerative medicine and rehabilitation engineering technologies, ranging from tissue engineering to neurological technologies, and the modulation of cardiovascular and cognitive functions. This review underscores the versatility of ES in various biomedical contexts and emphasizes the need to adapt to complex biological and clinical landscapes it addresses.

Electrical stimulation of Schwann cells on electrospun hyaluronic acid carbon nanotube fibers

Neurofibromatosis Type 1 (NF1) is a complex genetic disorder characterized by the development of benign neurofibromas, which can cause significant morbidity in affected individuals. While the molecular mechanisms underlying NF1 pathogenesis have been extensively studied, the development of effective therapeutic strategies remains a challenge. This paper presents the development and validation of a novel biomaterial testing model to enhance our understanding of NF1 pathophysiology, disease mechanisms and evaluate potential therapeutic interventions. Our long-term goal is to develop an invitro model of NF1 to evaluate drug targets. We have developed an in vitro system to test the cellular behavior of NF1 patient derived cells on electroconductive aligned nanofibrous biomaterials with electrical stimulatory cues. We hypothesized that cells cultured on electroconductive biomaterial will undergo morphological changes and variations in cell proliferation that could be further enhanced with the combination of exogenous electrical stimulation (ES). In this study, we developed electrospun Hyaluronic Acid-Carbon Nanotube (HA-CNT) nanofiber scaffolds to mimic the axon's topographical and bioelectrical cues that influence neurofibroma growth and development. The cellular behavior was qualitatively and quantitively analyzed through immunofluorescent stains, Alamar blue assays and ELISA assays. Schwann cells from NF1 patients appear to have lost their ability to respond to electrical stimulation in the development and regeneration range, which was seen through changes in morphology, proliferation and NGF release. Without stimulation, the conductive material enhances NF1 SC behavior. Wild-type SC respond to electrical stimulation with increased cell proliferation and NGF release. Using this system, we can better understand the interaction between axons and SC that lead to tumor formation, homeostasis and regeneration.

Advances in the Use of Conducting Polymers for Healthcare Monitoring

Conducting polymers (CPs) are an innovative class of materials recognized for their high flexibility and biocompatibility, making them an ideal choice for health monitoring applications that require flexibility. They are active in their design. Advances in fabrication technology allow the incorporation of CPs at various levels, by combining diverse CPs monomers with metal particles, 2D materials, carbon nanomaterials, and copolymers through the process of polymerization and mixing. This method produces materials with unique physicochemical properties and is highly customizable. In particular, the development of CPs with expanded surface area and high conductivity has significantly improved the performance of the sensors, providing high sensitivity and flexibility and expanding the range of available options. However, due to the morphological diversity of new materials and thus the variety of characteristics that can be synthesized by combining CPs and other types of functionalities, choosing the right combination for a sensor application is difficult but becomes important. This review focuses on classifying the role of CP and highlights recent advances in sensor design, especially in the field of healthcare monitoring. It also synthesizes the sensing mechanisms and evaluates the performance of CPs on electrochemical surfaces and in the sensor design. Furthermore, the applications that can be revolutionized by CPs will be discussed in detail.

Modified Carbon Nanotubes Favor Fibroblast Growth by Tuning the Cell Membrane Potential

As is known, carbon nanotubes favor cell growth in vitro, although the underlying mechanisms are not yet fully elucidated. In this study, we explore the hypothesis that electrostatic fields generated at the interface between nonexcitable cells and appropriate scaffold might favor cell growth by tuning their membrane potential. We focused on primary human fibroblasts grown on electrospun polymer fibers (poly(lactic acid)─PLA) with embedded multiwall carbon nanotubes (MWCNTs). The MWCNTs were functionalized with either the p-methoxyphenyl (PhOME) or the p-acetylphenyl (PhCOMe) moiety, both of which allowed uniform dispersion in a solvent, good mixing with PLA and the consequent smooth and homogeneous electrospinning process. The inclusion of the electrically conductive MWCNTs in the insulating PLA matrix resulted in differences in the surface potential of the fibers. Both PLA and PLA/MWCNT fiber samples were found to be biocompatible. The main features of fibroblasts cultured on different substrates were characterized by scanning electron microscopy, immunocytochemistry, Rt-qPCR, and electrophysiology revealing that fibroblasts grown on PLA/MWCNT reached a healthier state as compared to pure PLA. In particular, we observed physiological spreading, attachment, and Vmem of fibroblasts on PLA/MWCNT. Interestingly, the electrical functionalization of the scaffold resulted in a more suitable extracellular environment for the correct biofunctionality of these nonexcitable cells. Finally, numerical simulations were also performed in order to understand the mechanism behind the different cell behavior when grown either on PLA or PLA/MWCNT samples. The results show a clear effect on the cell membrane potential, depending on the underlying substrate.

Electroconductivity, a regenerative engineering approach to reverse rotator cuff muscle degeneration

Muscle degeneration is one the main factors that lead to the high rate of retear after a successful repair of rotator cuff (RC) tears. The current surgical practices have failed to treat patients with chronic massive rotator cuff tears (RCTs). Therefore, regenerative engineering approaches are being studied to address the challenges. Recent studies showed the promising outcomes of electroactive materials (EAMs) on the regeneration of electrically excitable tissues such as skeletal muscle. Here, we review the most important biological mechanism of RC muscle degeneration. Further, the review covers the recent studies on EAMs for muscle regeneration including RC muscle. Finally, we will discuss the future direction toward the application of EAMs for the augmentation of RCTs.

The role of Gel-Ppy-modified nerve conduit on the repair of sciatic nerve defect in rat model

The serious clinical challenge of peripheral nerve injury (PNI) is nerve regeneration. Nerve conduit represents a promising strategy to contribute to nerve regeneration by bridging injured nerve gaps. However, due to a unique microenvironment of nerve tissue, autologous nerves have not been substituted by nerve conduit. Nerve regeneration after nerve conduit implantation depends on many factors, such as conductivity and biocompatibility. Therefore, Gelatin (Gel) with biocompatibility and polypyrrole (Ppy) with conductivity is highly concerned. In this paper, Gel-Ppy modified nerve conduit was fabricated with great biocompatibility and conductivity to evaluate its properties of enhancing nerve regeneration in vivo and in vitro. The proliferation of Schwann cells on Gel-Ppy modified nerve conduit was remarkably increased. Consistent with in vitro results, the Gel-Ppy nerve conduit could contribute to the regeneration of Schwann cell in vivo. The axon diameters and myelin sheath thickness were also enhanced, resulting in the amelioration of muscle atrophy, nerve conduction, and motor function recovery. To explain this interesting phenomenon, western blot results indicated that the Gel-Ppy conduit facilitated nerve regeneration via upregulating the Rap1 pathway to induce neurite outgrowth. Therefore, the above results demonstrated that Gel-Ppy modified nerve conduit could provide an acceptable microenvironment for nerve regeneration and be popularized as a novel therapeutic strategy of PNI.

Revolutionizing Drug Delivery and Therapeutics: The Biomedical Applications of Conductive Polymers and Composites-Based Systems

The first conductive polymers (CPs) were developed during the 1970s as a unique class of organic substances with properties that are electrically and optically comparable to those of inorganic semiconductors and metals while also exhibiting the desirable traits of conventional polymers. CPs have become a subject of intensive research due to their exceptional qualities, such as high mechanical and optical properties, tunable electrical characteristics, ease of synthesis and fabrication, and higher environmental stability than traditional inorganic materials. Although conducting polymers have several limitations in their pure state, coupling with other materials helps overcome these drawbacks. Owing to the fact that various types of tissues are responsive to stimuli and electrical fields has made these smart biomaterials attractive for a range of medical and biological applications. For various applications, including the delivery of drugs, biosensors, biomedical implants, and tissue engineering, electrical CPs and composites have attracted significant interest in both research and industry. These bimodalities can be programmed to respond to both internal and external stimuli. Additionally, these smart biomaterials have the ability to deliver drugs in various concentrations and at an extensive range. This review briefly discusses the commonly used CPs, composites, and their synthesis processes. Further highlights the importance of these materials in drug delivery along with their applicability in various delivery systems.

One-Pot Synthesis of Bi2 S3 /TiO2 /rGO Heterostructure with Red Light-Driven Photovoltaic Effect for Remote Electrotherapy-Assisted Wound Repair

The past decades have witnessed the rational design of novel functional nanomaterials and the potential to revolutionize many applications. With the increasing focus on electronic biological processes, novel photovoltaic nanomaterials are highly expectable for empowering new therapeutic strategies such as establishing a link between endogenous electric field (EEF) and electrotherapy. Compared to traditional invasive stimulation, the light-initiating strategy has the advantages of non-invasion, non-power supply, and precise controllability. Whereas, common photoactivated materials require short-wavelength light excitation accompanied by poor tissue penetration and biohazard. Herein, by the construction of p-n heterostructured Bi₂ S₃ /TiO₂ /rGO (BTG) nanoparticles, broadener light absorption and higher light conversion than regular UV excitation are realized. Simultaneously, the photoelectric performance of BTG heterostructure, as well as the synergistic effect of Bi₂ S₃ morphology, are revealed. Besides, the rationally designed biomimetic hydrogel matrix consisting of collagen and hyaluronic acid provides appropriate bioactivity, interface adhesion, mechanical matching, and electron transfer. Therefore, the photovoltaic BTG-loaded matrix provides a platform of light-driven electrical stimulation, coupling the EEF to modulate the electrophysiological and regeneration microenvironment. The implementation of photoelectric stimulation holds broad prospects for non-drug therapy and electrical-related biological process modulation including osseointegration, nerve regeneration, electronic skin, and wound healing.

Biodegradable and Electrically Conductive Melanin-Poly (3-Hydroxybutyrate) 3D Fibrous Scaffolds for Neural Tissue Engineering Applications

Due to the severity of peripheral nerve injuries (PNI) and spinal cord injuries (SCI), treatment options for patients are limited. In this context, biomaterials designed to promote regeneration and reinstate the lost function are being explored. Such biomaterials should be able to mimic the biological, chemical, and physical cues of the extracellular matrix for maximum effectiveness as therapeutic agents. Development of biomaterials with desirable physical, chemical, and electrical properties, however, has proven challenging. Here a novel biomaterial formulation achieved by blending the pigment melanin and the natural polymer Poly-3-hydroxybutyrate (PHB) is proposed. Physio-chemical measurements of electrospun fibers reveal a feature rich surface nano-topography, a semiconducting-nature, and brain-tissue-like poroviscoelastic properties. Resulting fibers improve cell adhesion and growth of mouse sensory and motor neurons, without any observable toxicity. Further, the presence of polar functional groups positively affect the kinetics of fibers degradation at a pH (≈7.4) comparable to that of body fluids. Thus, melanin-PHB blended scaffolds are found to be physio-chemically, electrically, and biologically compatible with neural tissues and could be used as a regenerative modality for neural tissue injuries. A biomaterial for scaffolds intended to promote regeneration of nerve tissue after injury is developed. This biomaterial, obtained by mixing the pigment melanin and the natural polymer PHB, is biodegradable, electrically conductive, and beneficial to the growth of motor and sensory neurons. Thus, it is believed that this biomaterial can be used in the context of healthcare applications.

Electroconductive biomaterials for cardiac tissue engineering

Myocardial infarction (MI) is still the leading cause of mortality worldwide. The success of cell-based therapies and tissue engineering strategies for treatment of injured myocardium have been notably hindered due to the limitations associated with the selection of a proper cell source, lack of engraftment of engineered tissues and biomaterials with the host myocardium, limited vascularity, as well as immaturity of the injected cells. The first-generation approaches in cardiac tissue engineering (cTE) have mainly relied on the use of desired cells (e.g., stem cells) along with non-conductive natural or synthetic biomaterials for in vitro construction and maturation of functional cardiac tissues, followed by testing the efficacy of the engineered tissues in vivo. However, to better recapitulate the native characteristics and conductivity of the cardiac muscle, recent approaches have utilized electroconductive biomaterials or nanomaterial components within engineered cardiac tissues. This review article will cover the recent advancements in the use of electrically conductive biomaterials in cTE. The specific emphasis will be placed on the use of different types of nanomaterials such as gold nanoparticles (GNPs), silicon-derived nanomaterials, carbon-based nanomaterials (CBNs), as well as electroconductive polymers (ECPs) for engineering of functional and electrically conductive cardiac tissues. We will also cover the recent progress in the use of engineered electroconductive tissues for in vivo cardiac regeneration applications. We will discuss the opportunities and challenges of each approach and provide our perspectives on potential avenues for enhanced cTE. STATEMENT OF SIGNIFICANCE: Myocardial infarction (MI) is still the primary cause of death worldwide. Over the past decade, electroconductive biomaterials have increasingly been applied in the field of cardiac tissue engineering. This review article provides the readers with the leading advances in the in vitro applications of electroconductive biomaterials for cTE along with an in-depth discussion of injectable/transplantable electroconductive biomaterials and their delivery methods for in vivo MI treatment. The article also discusses the knowledge gaps in the field and offers possible novel avenues for improved cardiac tissue engineering.

Electrical Stimulation and Cellular Behaviors in Electric Field in Biomedical Research

Research on the cellular response to electrical stimulation (ES) and its mechanisms focusing on potential clinic applications has been quietly intensified recently. However, the unconventional nature of this methodology has fertilized a great variety of techniques that make the interpretation and comparison of experimental outcomes complicated. This work reviews more than a hundred publications identified mostly from Medline, categorizes the techniques, and comments on their merits and weaknesses. Electrode-based ES, conductive substrate-mediated ES, and noninvasive stimulation are the three principal categories used in biomedical research and clinic. ES has been found to enhance cell proliferation, growth, migration, and stem cell differentiation, showing an important potential in manipulating cellular activities in both normal and pathological conditions. However, inappropriate parameters or setup can have negative effects. The complexity of the delivered electric signals depends on how they are generated and in what form. It is also difficult to equate one set of parameters with another. Mechanistic studies are rare and badly needed. Even so, ES in combination with advanced materials and nanotechnology is developing a strong footing in biomedical research and regenerative medicine.

Conductive Biomaterials as Bioactive Wound Dressing for Wound Healing and Skin Tissue Engineering

Conductive biomaterials based on conductive polymers, carbon nanomaterials, or conductive inorganic nanomaterials demonstrate great potential in wound healing and skin tissue engineering, owing to the similar conductivity to human skin, good antioxidant and antibacterial activities, electrically controlled drug delivery, and photothermal effect. However, a review highlights the design and application of conductive biomaterials for wound healing and skin tissue engineering is lacking. In this review, the design and fabrication methods of conductive biomaterials with various structural forms including film, nanofiber, membrane, hydrogel, sponge, foam, and acellular dermal matrix for applications in wound healing and skin tissue engineering and the corresponding mechanism in promoting the healing process were summarized. The approaches that conductive biomaterials realize their great value in healing wounds via three main strategies (electrotherapy, wound dressing, and wound assessment) were reviewed. The application of conductive biomaterials as wound dressing when facing different wounds including acute wound and chronic wound (infected wound and diabetic wound) and for wound monitoring is discussed in detail. The challenges and perspectives in designing and developing multifunctional conductive biomaterials are proposed as well.

Surface functionalized bioceramics coated on metallic implants for biomedical and anticorrosion performance - a review

In modern days, the usage of trauma fixation devices has significantly increased due to sports injury, age-related issues, accidents, and revision surgery purposes. Numerous materials such as stainless steel, titanium, Co-Cr alloy, polymers, and ceramics have been used to replace the missing or defective parts of the human body. After implantation, body fluids (Na⁺, K⁺, and Cl^-), protein, and blood cells interact with the surface of metallic implants, which favours the release of ions from the metallic surface to surrounding body tissues, leading to a hypersensitive reaction. Body pH, temperature, and interaction of immune cells also cause metal ion leaching and lose host cell interaction and effective mineralization for better durability. Moreover, microbial invasion is another important crisis, which produces extracellular compounds onto the biomaterial surface through which it escapes from the antimicrobial agents. To enhance the performance of materials by improving mechanical, corrosion resistance, antimicrobial, and biocompatibility properties, surface modification is a prerequisite method in which chemical vapour deposition (CVD), physical vapour deposition (PVD), sol-gel method, and electrochemical deposition are generally involved. The properties of bioceramics such as chemical inertness, bioactivity, biocompatibility, and corrosion protection make them most suitable for the surface functionalization of metallic implants. To the best of our knowledge, very limited literature is available to discuss the interaction of body proteins, pH, and temperature onto bioceramic coatings. Hence, the present review focuses on the corrosion behaviour of different ceramic composite coating materials with different conditions. This review initially briefs the properties and surface chemistry of metal implants and the need for surface modifications by different deposition techniques. Further, mechanical, cytotoxicity, antimicrobial property, and electrochemical behaviour of ceramics and metal nitride coatings are discussed. Finally, future perspectives of coatings are outlined for biomedical applications.

Redox Polymers for Tissue Engineering

This review will focus on the targeted design, synthesis and application of redox polymers for use in regenerative medicine and tissue engineering. We define redox polymers to encompass a variety of polymeric materials, from the multifunctional conjugated conducting polymers to graphene and its derivatives, and have been adopted for use in the engineering of several types of stimulus responsive tissues. We will review the fundamental properties of organic conducting polymers (OCPs) and graphene, and how their properties are being tailored to enhance material - biological interfacing. We will highlight the recent development of high-resolution 3D fabrication processes suitable for biomaterials, and how the fabrication of intricate scaffolds at biologically relevant scales is providing exciting opportunities for the application of redox polymers for both in-vitro and in-vivo tissue engineering. We will discuss the application of OCPs in the controlled delivery of bioactive compounds, and the electrical and mechanical stimulation of cells to drive behaviour and processes towards the generation of specific functional tissue. We will highlight the relatively recent advances in the use of graphene and the exploitation of its physicochemical and electrical properties in tissue engineering. Finally, we will look forward at the future of organic conductors in tissue engineering applications, and where the combination of materials development and fabrication processes will next unite to provide future breakthroughs.

Conductive Materials for Healing Wounds: Their Incorporation in Electroactive Wound Dressings, Characterization, and Perspectives

The use of conductive materials to promote the activity of electrically responsive cells is an effective means of accelerating wound healing. This article focuses on recent advancements in conductive materials, with emphasis on overviewing their incorporation with non-conducting polymers to fabricate electroactive wound dressings. The characteristics of these electroactive dressings are deliberated, and the mechanisms on how they accelerate the wound healing process are discussed. Potential directions for the future development of electroactive wound dressings and their potential in monitoring the course of wound healing in vivo concomitantly are also proposed.

Theoretical analysis of the electrochemical systems used for the application of direct current/voltage stimuli on cell cultures

Endogenous electric fields drive many essential functions relating to cell proliferation, motion, differentiation and tissue development. They are usually mimicked in vitro by using electrochemical systems to apply direct current or voltage stimuli to cell cultures. The many studies devoted to this topic have given rise to a wide variety of experimental systems, whose results are often difficult to compare. Here, these systems are analysed from an electrochemical standpoint to help harmonize protocols and facilitate optimal understanding of the data produced. The theoretical analysis of single-electrode systems shows the necessity of measuring the Nernst potential of the electrode and of discussing the results on this basis rather than using the value of the potential gradient. The paper then emphasizes the great complexity that can arise when high cell voltage is applied to a single electrode, because of the possible occurrence of anode and cathode sites. An analysis of two-electrode systems leads to the advice to change experimental practices by applying current instead of voltage. It also suggests that the values of electric fields reported so far may have been considerably overestimated in macro-sized devices. It would consequently be wise to revisit this area by testing considerably lower electric field values.

Promotion of the osteogenic activity of an antibacterial polyaniline coating by electrical stimulation

Electrical stimulation (ES) exhibits a positive role in promoting the cell activity of osteoblasts. Conducting polymers have the advantages of biocompatibility, good environmental stability and easy synthesis, which have been widely used as charge carriers for electrical stimulation; moreover, considering clinical applications, biomaterial-related infection is an important issue that needs to be solved. Thus, conducting polymers with both antibacterial and osteogenic properties are highly demanded for effect repair. However, it remains a challenge to combine these two characteristics efficiently in a simple way. Herein, an Ag-loaded poly(amide-amine) dendrimer was prepared by a simple chemical reduction procedure, which acted as a dopant for the polymerization of polyaniline (PANI) on biomedical titanium (Ti) sheets. The obtained PANI coating showed outstanding antibacterial properties against Gram-negative (E. coli) and Gram-positive (S. aureus) microbes with a 1000-fold increase when compared with that of pure Ti. In addition, note that the polymer coating together with ES facilitated the proliferation and differentiation of MC3T3. The alkaline phosphatase (ALP) activity and intracellular calcium content of the cells showed a 19.09% and 24.02% increase, respectively, when compared with the case of electrically stimulated Ti after 12 days. Moreover, the existence of PAMAM facilitated mineralization. The strategy developed herein is simple and can be easily manipulated, which shows potential applications in the coating of implants for hard tissue repair.

Enabling biodegradable functional biomaterials for the management of neurological disorders

An increasing number of patients are being diagnosed with neurological diseases, but are rarely cured because of the lack of curative therapeutic approaches. This situation creates an urgent clinical need to develop effective diagnosis and treatment strategies for repair and regeneration of injured or diseased neural tissues. In this regard, biodegradable functional biomaterials provide promising solutions to meet this demand owing to their unique responsiveness to external stimulation fields, which enable neuro-imaging, neuro-sensing, specific targeting, hyperthermia treatment, controlled drug delivery, and nerve regeneration. This review discusses recent progress in the research and development of biodegradable functional biomaterials including electroactive biomaterials, magnetic materials and photoactive biomaterials for the management of neurological disorders with emphasis on their applications in bioimaging (photoacoustic imaging, MRI and fluorescence imaging), biosensing (electrochemical sensing, magnetic sensing and opical sensing), and therapy strategies (drug delivery, hyperthermia treatment, and tissue engineering). It is expected that this review will provide an insightful discussion on the roles of biodegradable functional biomaterials in the diagnosis and treatment of neurological diseases, and lead to innovations for the design and development of the next generation biodegradable functional biomaterials.

A Mussel-Inspired Persistent ROS-Scavenging, Electroactive, and Osteoinductive Scaffold Based on Electrochemical-Driven In Situ Nanoassembly

Conductive polymers are promising for bone regeneration because they can regulate cell behavior through electrical stimulation; moreover, they are antioxidative agents that can be used to protect cells and tissues from damage originating from reactive oxygen species (ROS). However, conductive polymers lack affinity to cells and osteoinductivity, which limits their application in tissue engineering. Herein, an electroactive, cell affinitive, persistent ROS-scavenging, and osteoinductive porous Ti scaffold is prepared by the on-surface in situ assembly of a polypyrrole-polydopamine-hydroxyapatite (PPy-PDA-HA) film through a layer-by-layer pulse electrodeposition (LBL-PED) method. During LBL-PED, the PPy-PDA nanoparticles (NPs) and HA NPs are in situ synthesized and uniformly coated on a porous scaffold from inside to outside. PDA is entangled with and doped into PPy to enhance the ROS scavenging rate of the scaffold and realize repeatable, efficient ROS scavenging over a long period of time. HA and electrical stimulation synergistically promote osteogenic cell differentiation on PPy-PDA-HA films. Ultimately, the PPy-PDA-HA porous scaffold provides excellent bone regeneration through the synergistic effects of electroactivity, cell affinity, and antioxidative activity of the PPy-PDA NPs and the osteoinductivity of HA NPs. This study provides a new strategy for functionalizing porous scaffolds that show great promise as implants for tissue regeneration.

Fabrication of a Biocompatible Liquid Crystal Graphene Oxide-Gold Nanorods Electro- and Photoactive Interface for Cell Stimulation

For decades, electrode-tissue interfaces are pursued to establish electrical stimulation as a reliable means to control neuronal cells behavior. However, spreading of electrical currents in tissues limits its spatial precision. Thus, optical cues, such as near-infrared (NIR) light, are explored as alternatives. Presently, NIR stimulation requires higher energy input than electrical methods despite introduction of light absorbers, e.g., gold nanoparticles. As potential solution, NIR and electrical costimulation are proposed but with limited interfaces capable of sustaining this stimulation technique. Here, a novel electroactive nanocomposite with photoactive properties in the NIR range is constructed by N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride/N-hydroxysulfosuccinimide sodium (EDC)/NHS conjugation of liquid crystal graphene oxide (LCGO) to protein-coated gold nanorods (AuNR). The liquid crystal graphene oxide-gold nanorod nanocomposite (LCGO-AuNR) is fabricated into a hydrophilic electrode-coating via drop-casting, making it appropriate for versatile electrode-tissue interface fabrication. UV-vis spectrophotometry results demonstrate that LCGO-AuNR presents an absorbance peak at 798 nm (NIR range). Cyclic voltammetry measurements further confirm its electroactive capacitive properties. Furthermore, LCGO-AuNR coating supports cell adhesion, proliferation, and differentiation of NG108-15 neuronal cells. This biocompatible interface is anticipated, with ideal electrical and optical properties for NIR and electrical costimulation, to enable further development of the technique for energy-efficient and precise neuronal cell modulation.

Electroactive biomaterials: Vehicles for controlled delivery of therapeutic agents for drug delivery and tissue regeneration

Electrical stimulation for delivery of biochemical agents such as genes, proteins and RNA molecules amongst others, holds great potential for controlled therapeutic delivery and in promoting tissue regeneration. Electroactive biomaterials have the capability of delivering these agents in a localized, controlled, responsive and efficient manner. These systems have also been combined for the delivery of both physical and biochemical cues and can be programmed to achieve enhanced effects on healing by establishing control over the microenvironment. This review focuses on current state-of-the-art research in electroactive-based materials towards the delivery of drugs and other therapeutic signalling agents for wound care treatment. Future directions and current challenges for developing effective electroactive approach based therapies for wound care are discussed.

Self-Assembled Biomolecular 1D Nanostructures for Aqueous Sodium-Ion Battery

Aqueous sodium-ion battery of low cost, inherent safety, and environmental benignity holds substantial promise for new-generation energy storage applications. However, the narrow potential window of water and the enlarged ionic radius because of hydration restrict the selection of electrode materials used in the aqueous electrolyte. Here, inspired by the efficient redox reaction of biomolecules during cellular energy metabolism, a proof of concept is proposed that the redox-active biomolecule alizarin can act as a novel electrode material for the aqueous sodium-ion battery. It is demonstrated that the specific capacity of the self-assembled alizarin nanowires can reach as high as 233.1 mA h g^-1, surpassing the majority of anodes ever utilized in the aqueous sodium-ion batteries. Paired with biocompatible and biodegradable polypyrrole, this full battery system shows excellent sodium storage ability and flexibility, indicating its potential applications in wearable electronics and biointegrated devices. It is also shown that the electrochemical properties of electrodes can be tailored by manipulating naturally occurring 9,10-anthroquinones with various substituent groups, which broadens application prospect of biomolecules in aqueous sodium-ion batteries.

Electrically conductive MEH-PPV:PCL electrospun nanofibres for electrical stimulation of rat PC12 pheochromocytoma cells

Electrically conductive, porous, mechanically strong and bioactive electrospun MEH-PPV:PCL nanofibres with blended and core-sheath formulations for enhanced neurite formation and neurite outgrowth.

Mediation of cellular osteogenic differentiation through daily stimulation time based on polypyrrole planar electrodes

In electrical stimulation (ES), daily stimulation time means the interacting duration with cells per day, and is a vital factor for mediating cellular function. In the present study, the effect of stimulation time on osteogenic differentiation of MC3T3-E1 cells was investigated under ES on polypyrrole (Ppy) planar interdigitated electrodes (IDE). The results demonstrated that only a suitable daily stimulation time supported to obviously upregulate the expression of ALP protein and osteogenesis-related genes (ALP, Col-I, Runx2 and OCN), while a short or long daily stimulation time showed no significant outcomes. These might be attributed to the mechanism that an ES induced transient change in intracellular calcium ion concentration, which was responsible for activating calcium ion signaling pathway to enhance cellular osteogenic differentiation. A shorter daily time could lead to insufficient duration for the transient change in intracellular calcium ion concentration, and a longer daily time could give rise to cellular fatigue with no transient change. This work therefore provides new insights into the fundamental understanding of cell responses to ES and will have an impact on further designing materials to mediate cell behaviors.

A critical review on the prospect of polyaniline-grafted biodegradable nanocomposite

Among the various electrically conducting polymers, polyaniline (PANI) has gained attentions due to its unique properties and doping chemistry. A number of electrically conducting biodegradable polymers has been synthesized by incorporating a biodegradable content of cellulose, chitin, chitosan, etc. in the matrix of PANI. The hybrid materials are also employed as photocatalysts, antibacterial agents, sensors, fuel cells and as materials in biomedical applications. Furthermore, these biodegradable and biocompatible conducting polymers are employed in tissue engineering, dental implants and targeted drug delivery. This review presents state of the art of PANI based biodegradable polymers along with their synthesis routes and unique applications in diverse fields. In future, the synthesis of PANI-grafted biodegradable nanocomposite material is expected to open innovative ways for their outstanding applications.

Time-dependent effect of electrical stimulation on osteogenic differentiation of bone mesenchymal stromal cells cultured on conductive nanofibers

Bone tissue engineering using bone mesenchymal stromal cells (BMSCs) is a multidisciplinary strategy that requires biodegradable scaffold, cell, various promoting cues to work simultaneously. Electrical stimulation (ES) is known able to promote osteogenic differentiation of BMSCs, but it is interesting to know how can it play the strongest promotion effect. To strengthen local ES on BMSCs, parallel-aligned conductive nanofibers were electrospun from the mixtures of poly(L-lactide) (PLLA) and multi-walled carbon nanotubes (MWCNTs), and used for cell culture. Osteogenic differentiation of BMSCs was conducted by applying ES (direct current, 1.5 V, 1.5 h/day) perpendicular to the fiber direction during the day 1-7, day 8-14, or day 15-21 period of the osteoinductive culture. In comparison with ES-free groups, bone-related markers and genes were found significantly up-regulated when ES was applied on BMSCs growing on nanofibers having higher conductivity. When the ES was applied at the earlier stage of osteoinductive culture, the promotion effect on osteogenic differentiation would be stronger. In the presence of a BMP blocker, the down-regulated expressions of bone-related genes were able to be slightly recovered by ES, especially when the ES was applied at the beginning of osteoinductive culture (i.e. day 1-7). The promotion effect generated by ES in the early stage was found sustainable to later stages of differentiation, while those ES applied at later stages of differentiation should have missed the optimal point. In other words, later ES was not so necessary in inducing the osteogenic differentiation of BMSCs. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 3369-3383, 2017.

Topographical and Electrical Stimulation of Neuronal Cells through Microwrinkled Conducting Polymer Biointerfaces

The development of smart biointerfaces combining multiple functions is crucial for triggering a variety of cellular responses. In this work, wrinkled organic interfaces based on the conducting polymer poly(3,4-ethylene dioxythiophene) doped with poly(styrene sulfonate) are developed with the aim to simultaneously convey electrical and topographical stimuli to cultured cells. The surface wrinkling of thin films on heat-shrink polymer sheets allows for rapid patterning of self-assembled anisotropic topographies characterized by micro/sub-microscale aligned wrinkles. The developed interfaces prove to support the growth and differentiation of neural cells (SH-SY5Y, human neuroblastoma) and are remarkably effective in promoting axonal guidance, by guiding and stimulating the neurite growth in differentiating cells. Electrical stimulation with biphasic pulses delivered through the conductive wrinkled interface is found to further promote the neurite growth, demonstrating the suitability of such interfaces as platforms for conveying multiple stimuli to cells and tissues.

Composite electrospun nanofibers of reduced graphene oxide grafted with poly(3-dodecylthiophene) and poly(3-thiophene ethanol) and blended with polycaprolactone

In this paper, an effective method was employed for preparation of nanofibers using conducting polymer-functionalized reduced graphene oxide (rGO). First, graphene oxide (GO) was obtained from graphite by Hommer method. GO was reduced to rGO by NaBH₄ and covalently functionalized with a 3-thiophene acetic acid (TAA) by an esterification reaction to reach 3-thiophene acetic acid-functionalized reduced graphene oxide macromonomer (rGO-f-TAAM). Afterward, rGO-f-TAAM was copolymerized with 3-dodecylthiophene (3DDT) and 3-thiophene ethanol (3TEt) to yield rGO-f-TAA-co-PDDT (rGO-g-PDDT) and rGO-f-TAA-co-P3TEt (rGO-g-PTEt), which were confirmed by Fourier transform infrared spectra. The grafted materials depicted better electrochemical properties and superior solubilities in organic solvents compared to GO and rGO. The soluble rGO-g-PDDT and rGO-g-PTEt composites blended with polycaprolactone were fabricated by electrospinning, and then cytotoxicity, hydrophilicity, biodegradability and mechanical properties were investigated. The grafted rGO composites exhibited a good electroactivity behavior, mainly because of the enhanced electrochemical performance. The electrospun nanofibers underwent degradation about 7 wt% after 40 days, and the fabricated scaffolds were not able to induce cytotoxicity in mouse osteoblast MC3T3-E1 cells. The soluble conducting composites developed in this study are utilizable in the fabrication of nanofibers with tissue engineering application.

Electroactive BaTiO3 nanoparticle-functionalized fibrous scaffolds enhance osteogenic differentiation of mesenchymal stem cells

It has been proven that the surface topographic cues of fiber arrangement can induce osteogenic differentiation of mesenchymal stem cells. However, this effect alone is weak and insufficient to meet the needs of regenerative medicine. In this work, electroactivity concept was introduced to enhance the osteoinductivity of fibrous scaffolds. The randomly oriented and aligned electroactive fibrous scaffolds of poly-(l-lactic acid) (PLLA) with incorporation of ferroelectric ceramic BaTiO₃ (BTO) nanoparticles (NPs) were fabricated by electrospinning. Physicochemical properties, including fiber morphology, microstructure, composition, thermal stability, surface roughness, and surface wettability, of these fibrous scaffolds were studied. The dielectric properties of the scaffolds were evaluated. The results showed that the randomly oriented BTO/PLLA composite fibrous scaffolds had the highest dielectric permittivity of 1.19, which is of the same order of magnitude as the natural bone. The combined effects of fiber orientation and electrical activity on the osteogenic responses of bone marrow mesenchymal stem cells (BM-MSCs) were specifically investigated. Randomly oriented composite fibrous scaffolds significantly promoted polygonal spreading and encouraged early osteogenic differentiation in BM-MSCs, whereas aligned composite fibrous scaffolds promoted cell elongation and discouraged osteogenic differentiation. These results evidenced that randomly fiber orientation and biomimetic electric activity have combining effects on osteogenic differentiation of BM-MSCs. Our findings indicate that coupling effects of multi-physical properties should be paid more attention to mimic the microenvironment for enhancing osteogenic differentiation of BM-MSCs.

Fabrication and characterization of conductive poly (3,4-ethylenedioxythiophene) doped with hyaluronic acid/poly (l-lactic acid) composite film for biomedical application

Poly 3,4-ethylenedioxythiophene (PEDOT), a polythiophene derivative, has been proved to be modified by chemical process as biocompatible conductive polymer for biomedical applications. In this study, novel hyaluronic acid (HA)-doped PEDOT nanoparticles were synthesized by the method of chemical oxidative polymerization, then conductive PEDOT-HA/poly(l-lactic acid) (PLLA) composite films were prepared. The physicochemical characteristics and biocompatibility of films were further investigated. FTIR, Raman and EDX analysis demonstrated that HA was successfully doped into PEDOT particles. Cyclic voltammograms indicated PEDOT-HA particles had favorable electrochemical stability. PEDOT-HA/PLLA films showed lower surface contact angle and faster degradation degree compared with PLLA films. Moreover, the cytotoxicity test of PEDOT-HA/PLLA films showed that neuron-like pheochromocytoma (PC12) cells adhered and spread well on the surface of PEDOT-HA/PLLA films and cell viability denoted by MTT assay had a significant increase. PEDOT-HA/PLLA films modified with laminin (LN) also exhibited an efficiently elongated cell morphology observed by fluorescent microscope and metallographic microscope. Furthermore, PEDOT-HA/PLLA films were subjected to different current intensity to elucidate the effect of electrical stimulation (ES) on neurite outgrowth of PC12 cells. ES (0.5 mA, 2 h) significantly promoted neurite outgrowth with an average value length of 122 ± 5 μm and enhanced the mRNA expression of growth-associated protein (GAP43) and synaptophysin (SYP) in PC12 cells when compared with other ES groups. These results suggest that PEDOT-HA/PLLA film combined with ES are conducive to cell growth and neurite outgrowth, indicating the conductive PEDOT-HA/PLLA film may be an attractive candidate with ES for enhancing nerve regeneration in nerve tissue engineering.

Aligned Nanofibers from Polypyrrole/Graphene as Electrodes for Regeneration of Optic Nerve via Electrical Stimulation

The damage of optic nerve will cause permanent visual field loss and irreversible ocular diseases, such as glaucoma. The damage of optic nerve is mainly derived from the atrophy, apoptosis or death of retinal ganglion cells (RGCs). Though some progress has been achieved on electronic retinal implants that can electrically stimulate undamaged parts of RGCs or retina to transfer signals, stimulated self-repair/regeneration of RGCs has not been realized yet. The key challenge for development of electrically stimulated regeneration of RGCs is the selection of stimulation electrodes with a sufficient safe charge injection limit (Q(inj), i.e., electrochemical capacitance). Most traditional electrodes tend to have low Q(inj) values. Herein, we synthesized polypyrrole functionalized graphene (PPy-G) via a facile but efficient polymerization-enhanced ball milling method for the first time. This technique could not only efficiently introduce electron-acceptor nitrogen to enhance capacitance, but also remain a conductive platform-the π-π conjugated carbon plane for charge transportation. PPy-G based aligned nanofibers were subsequently fabricated for guided growth and electrical stimulation (ES) of RGCs. Significantly enhanced viability, neurite outgrowth and antiaging ability of RGCs were observed after ES, suggesting possibilities for regeneration of optic nerve via ES on the suitable nanoelectrodes.

Mechanistic contribution of electroconductive hydroxyapatite–titanium disilicide composite on the alignment and proliferation of cells

We elucidate here the mechanistic contribution of a novel electroconductive hydroxyapatite-20 wt.% titanium disilicide (HA–TiSi2) composite system in favorably modulating osteoblast functions in relation to the monolithic HA. The higher electrical conductivity of HA–TiSi2 (σDC ∼ 67.117 ± 3.57 S/m) in comparison to glass sample effectively guided the electroactive myoblast, leading to their significant alignment and proliferation. This favorable behavior is attributed to the formation of small electrochemical cells between HA and TiSi2 phase, which produce a small electric field, directing the electroactive myoblast to migrate and grow in a particular direction. In contrast, no impact of TiSi2 on osteoblast function was observed because of their inability to respond to small electric field. However, the in vitro bioactivity in simulated body fluid indicated the nucleation and growth of apatite crystals. Moreover, in the context of load-bearing capability, the presence of 20 wt.% TiSi2 in HA led to increase in the fracture toughness by ∼100%. This study underscores the effectiveness of HA–TiSi2 in favorably modulating the cellular activity, myoblast in particular.