Electroactive Hydrogels Research Articles

Hydrogel-Integrated Multimodal Response as a Wearable and Implantable Bidirectional Interface for Biosensor and Therapeutic Electrostimulation.

A hydrogel that fuses long-term biologic integration, multimodal responsiveness, and therapeutic functions has received increasing interest as a wearable and implantable sensor but still faces great challenges as an all-in-one sensor by itself. Multiple bonding with stimuli response in a biocompatible hydrogel lights up the field of soft hydrogel interfaces suitable for both wearable and implantable applications. Given that, we proposed a strategy of combining chemical cross-linking and stimuli-responsive physical interactions to construct a biocompatible multifunctional hydrogel. In this hydrogel system, ureidopyrimidinone/tyramine (Upy/Tyr) difunctionalization of gelatin provides abundant dynamic physical interactions and stable covalent cross-linking; meanwhile, Tyr-doped poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) acts as a conductive filler to establish electrical percolation networks through enzymatic chemical cross-linking. Thus, the hydrogel is characterized with improved conductivity, conformal biointegration features (i.e., high stretchability, rapid self-healing, and excellent tissue adhesion), and multistimuli-responsive conductivity (i.e., temperature and urea). On the basis of these excellent performances, the prepared multifunctional hydrogel enables multimodal wearable sensing integration that can simultaneously track both physicochemical and electrophysiological attributes (i.e., motion, temperature, and urea), providing a more comprehensive monitoring of human health than current wearable monitors. In addition, the electroactive hydrogel here can serve as a bidirectional neural interface for both neural recording and therapeutic electrostimulation, bringing more opportunities for nonsurgical diagnosis and treatment of diseases.

Electroactive injectable hydrogel based on oxidized sodium alginate and carboxymethyl chitosan for wound healing

Electroactive hydrogel is of great significance in restoring wound currents, promoting cell proliferation, and accelerating the wound healing process. However, the poor dispersity and underlying toxicity of electronic conductive fillers and high concentration of ionic conductors in traditional electroactive hydrogel limited its application in medical care. Herein, an electroactive oxidized sodium alginate/carboxymethyl chitosan/silver nanoparticles (OSA/CMCS/AgNPs) hydrogel was constructed with no additional conductive fillers or synthesized conductive polymers being added, in which the dynamic imine bonds were rapidly formed between aldehyde groups in OSA and amino groups in CMCS, and AgNPs were further in situ formed by UV irradiation. The electroactive hydrogel exhibited the injectable property, strong self-healing ability, excellent biocompatibility, and high antibacterial activities. Moreover, the electroactive hydrogel can significantly promote the proliferation of L929 cells under electrical stimulation. Furthermore, the electroactive hydrogel was proved to significantly accelerate the wound healing process in the full-thickness skin defect model, exhibiting anti-inflammation, promoting the fibroblasts proliferation, angiogenesis, and collagen deposition under electrical stimulation. In summary, the current work explored a novel strategy to construct the polysaccharides-based electroactive hydrogel with good biocompatibility and multi-functions, which is promising to be used in deep wound treatment.

Bioadhesive and electroactive hydrogels for flexible bioelectronics and supercapacitors enabled by a redox-active core-shell PEDOT@PZIF-71 system.

Stretchable and conductive hydrogels are rapidly emerging as new generation candidates for wearable devices. However, the poor electroactivity and bioadhesiveness of traditional conductive hydrogels has limited their applications. Herein, a mussel-inspired strategy is proposed to prepare a specific core-shell redox-active system, consisting of a polydopamine (PDA) modified zeolitic imidazolate framework 71 (ZIF-71) core, and a poly 3,4-ethylenedioxythiopene (PEDOT) shell. Owing to the abundant catechol groups, PEDOT can be assembled on the surface of ZIF-71 to create a redox-active system. The core-shell nanoparticles could act as a redox-active nanofiller to develop a conductive polyacrylamide (PAM) hydrogel with energy-storage properties. The core-shell PEDOT@PZIF-71 system provides a mussel-inspired environment in the hydrogel matrix and endows the hydrogel with stretchability and adhesiveness. The hydrogel can be applied as a functional electrode for both bioelectronics and supercapacitors. Moreover, this hydrogel exhibits favorable biocompatibility and can be implanted in vivo for biosignal measurement without causing inflammation. This redox-active core-shell PEDOT@PZIF-71 system provides a promising strategy for the design of hydrogel-based wearable electronic devices.

Nonlinear chemo-electro-mechanical interaction of electroactive hydrogels under environmental stimuli: Formulation and finite element computation

Nonlinear chemo-electro-mechanical interaction of electroactive hydrogels under environmental stimuli: Formulation and finite element computation

Left Ventricular Geometry and Angiogenesis Improvement in Rat Chronic Ischemic Cardiomyopathy following Injection of Encapsulated Mesenchymal Stem Cells.

Injection of hydrogel and cells into myocardial infarction (MI) patients is one of the emerging treatment techniques, however, it has some limitations such as a lack of electromechanical properties and neovascularization. We investigated the therapeutic potential of new electroactive hydrogel [reduced graphene oxide (rGO)/Alginate (ALG)] encapsulated human bone marrow mesenchymal stem cells (BMSCs). The experimental study involved ligating the left anterior descending coronary artery (LAD) in rat models of chronic ischemic cardiomyopathy. Echocardiograms were analyzed at 4 and 8 weeks after MI treatment. In the eighth week after injection in the heart, the rats were sacrificed. Histological and immunohistochemical analyses were performed using Hematoxylin and Eosin (H and E) staining, Masson's trichrome staining and anti-CD31 antibody to analyze tissue structure and detect neovascularization. In comparison to the control and other treatment groups, MSCs encapsulated in rGO-ALG showed significant improvements in fractional shortening (FS), ejection fraction (EF), wall thickness and internal diameters (P<0.05). The morphological observation showed several small blood vessels formed around the transplantation site in all treated groups especially in the MSC-ALG-rGO group 8 weeks after the transplantation. Also, Masson's trichrome staining indicated an increased amount of collagen fibers in rGO-ALG-MSC. Microvessel density was significantly higher using MSC-ALG-rGO compared to controls (P<0.01). This study demonstrates that intramyocardial injection of rGO/ALG, a bio-electroactive hydrogel, is safe for increasing LV function, neovascularization, and adjusting electrical characteristics following MI. The results confirm ALG promising capability as a natural therapeutic for cardiac regeneration.

Carboxymethyl Chitosan and Gelatin Hydrogel Scaffolds Incorporated with Conductive PEDOT Nanoparticles for Improved Neural Stem Cell Proliferation and Neuronal Differentiation

Tissue engineering scaffolds provide biological and physiochemical cures to guide tissue recovery, and electrical signals through the electroactive materials possess tremendous potential to modulate the cell fate. In this study, a novel electroactive hydrogel scaffold was fabricated by assembling poly(3,4-ethylenedioxythiophene) (PEDOT) nanoparticles on a carboxymethyl chitosan/gelatin (CMCS/Gel) composite hydrogel surface via in situ chemical polymerization. The chemical structure, morphology, conductivity, porosity, swelling rate, in vitro biodegradation, and mechanical properties of the prepared hydrogel samples were characterized. The adhesion, proliferation, and differentiation of neural stem cells (NSCs) on conductive hydrogels were investigated. The CMCS/Gel-PEDOT hydrogels exhibited high porosity, excellent water absorption, improved thermal stability, and adequate biodegradability. Importantly, the mechanical properties of the prepared hydrogels were similar to those of brain tissue, with electrical conductivity up to (1.52 ± 0.15) × 10-3 S/cm. Compared to the CMCS/Gel hydrogel, the incorporation of PEDOT nanoparticles significantly improved the adhesion of NSCs, and supported long-term cell growth and proliferation in a three-dimensional (3D) microenvironment. In addition, under the differentiation condition, the conductive hydrogel also significantly enhanced neuronal differentiation with the up-regulation of β-tubulin III expression. These results suggest that CMCS/Gel-PEDOT hydrogels may be an attractive conductive substrate for further studies on neural tissue repair and regeneration.

Electrochemically Enhanced Delivery of Pemetrexed from Electroactive Hydrogels.

Electroactive hydrogels based on derivatives of polyethyleneglycol (PEG), chitosan and polypyrrole were prepared via a combination of photopolymerization and oxidative chemical polymerization, and optionally doped with anions (e.g., lignin, drugs, etc.). The products were analyzed with a variety of techniques, including: FT-IR, UV-Vis, 1H NMR (solution state), 13C NMR (solid state), XRD, TGA, SEM, swelling ratios and rheology. The conductive gels swell ca. 8 times less than the non-conductive gels due to the presence of the interpenetrating network (IPN) of polypyrrole and lignin. A rheological study showed that the non-conductive gels are soft (G' 0.35 kPa, G″ 0.02 kPa) with properties analogous to brain tissue, whereas the conductive gels are significantly stronger (G' 30 kPa, G″ 19 kPa) analogous to breast tissue due to the presence of the IPN of polypyrrole and lignin. The potential of these biomaterials to be used for biomedical applications was validated in vitro by cell culture studies (assessing adhesion and proliferation of fibroblasts) and drug delivery studies (electrochemically loading the FDA-approved chemotherapeutic pemetrexed and measuring passive and stimulated release); indeed, the application of electrical stimulus enhanced the release of PEM from gels by ca. 10-15% relative to the passive release control experiment for each application of electrical stimulation over a short period analogous to the duration of stimulation applied for electrochemotherapy. It is foreseeable that such materials could be integrated in electrochemotherapeutic medical devices, e.g., electrode arrays or plates currently used in the clinic.

Chondroitin/polypyrrole nanocomposite hydrogels for the accurate release of 5‐fluorouracil by electrical stimulation

AbstractThe development of electro‐stimulated drug release devices is an innovative approach to attain the drug delivery in accurate doses at target sites in a programmed manner. In this work, novel electroactive nanocomposite hydrogels were prepared by encapsulating green‐synthesized polypyrrole (PPy) colloids within chondroitin sulfate (CS) networks during the self‐crosslinking of CS via N‐ethyl‐N′‐(3‐dimethylaminopropyl) carbodiimide chemistry. The structural and morphological properties of CS/PPy hydrogels were studied by Fourier‐transformed infrared spectroscopy, scanning electron microscopy, and swelling kinetic measurements. The chemotherapeutic agent 5‐fluorouracil (5‐FU) was loaded into CS/PPy samples by hydrogel swelling method, or alternatively, by pre‐incubating the drug in polymer mixture before crosslinking. Different electrical stimulations can be used to switch ON and accurately tune the 5‐FU delivery from GG/PPy hydrogels. A single pulse potential of 5 V switched on the drug delivery up to 90% from nanocomposite hydrogel, in contrast to the low 5‐FU amount released in a passive form (&lt; 20%). PPy electroactive behavior played a determining role as the main driving force in 5‐FU release activation. Cytotoxicity of hydrogels with and without 5‐FU was examined in normal and cancer cells. Considering the high cytotoxicity of 5‐FU, the ON/OFF 5‐FU release patterns evidenced the potential of CS/PPy hydrogels for electrically controlled drug delivery in implantable or transdermal drug release devices.

Piezoresistive MXene/Silk fibroin nanocomposite hydrogel for accelerating bone regeneration by Re-establishing electrical microenvironment.

The electrical microenvironment plays an important role in bone repair. However, the underlying mechanism by which electrical stimulation (ES) promotes bone regeneration remains unclear, limiting the design of bone microenvironment–specific electroactive materials. Herein, by simple co-incubation in aqueous suspensions at physiological temperatures, biocompatible regenerated silk fibroin (RSF) is found to assemble into nanofibrils with a β-sheet structure on MXene nanosheets, which has been reported to inhibit the restacking and oxidation of MXene. An electroactive hydrogel based on RSF and bioencapsulated MXene is thus prepared to promote efficient bone regeneration. This MXene/RSF hydrogel also acts as a piezoresistive pressure transducer, which can potentially be utilized to monitor the electrophysiological microenvironment. RNA sequencing is performed to explore the underlying mechanisms, which can activate Ca2+/CALM signaling in favor of the direct osteogenesis process. ES is found to facilitate indirect osteogenesis by promoting the polarization of M2 macrophages, as well as stimulating the neogenesis and migration of endotheliocytes. Consistent improvements in bone regeneration and angiogenesis are observed with MXene/RSF hydrogels under ES in vivo. Collectively, the MXene/RSF hydrogel provides a distinctive and promising strategy for promoting direct osteogenesis, regulating immune microenvironment and neovascularization under ES, leading to re-establish electrical microenvironment for bone regeneration.

Preface

Due to recent pandemic, 2022 8th International Conference on Applied Materials and Manufacturing Technology (ICAMMT 2022) was held virtually online on April 15th-17th, 2022. The decision to hold the virtual conference was made in compliance with many restrictions and regulations that were imposed by countries around the globe. Such restrictions were made to minimize the risk of people contracting or spreading the COVID-19 through physical contact. There were 160 individuals who attended this online conference, represented many countries.ICAMMT 2022 is to bring together innovative academics and industrial experts in the field of Manufacturing Technology and Applied Materials to a common forum. The primary goal of the conference is to promote research and developmental activities in manufacturing technology and engineering materials, and another goal is to promote scientific information interchange between researchers, developers, engineers, students, and practitioners working all around the world. The conference will be held every year to make it an ideal platform for people to share views and experiences in Manufacturing Technology, Intelligent Manufacturing and Applied Materials and related areas.During the conference, the conference model was divided into three sessions, including oral presentations, keynote speeches, and online Q&A discussion. In the first part, some scholars, whose submissions were selected as the excellent papers, were given about 5-10 minutes to perform their oral presentations one by one. Then in the second part, keynote speakers were each allocated 30-45 minutes to hold their speeches.In the second part, we invited four professors as our keynote speakers. Prof. Yajun Liu, South China University of Technology, China. His research interest is in the areas of Mechanical system signal testing, analysis, characterization, control and performance optimization. The second keynote speakers, Prof. Honggang Dong, School of Materials Science and Engineering, Dalian University of Technology, China. His research area is Refilled friction stir spot welding of aluminum alloy to galvanized steel sheets. Prof. Weiwei Zhao, Wuhan University of Technology, China. His research area includes Characterization of mechanical and mechanical properties of polymer hydrogels, research and development of biomimetic electroactive hydrogels, and applications of polymer materials in microfluidic devices and biomedicine. Lastly, we were glad to invite Prof. Md. Akhtaruzzaman, Solar Energy Research Institute (SERI) of The National University of Malaysia as our finale keynote speakers. He studied on the design and synthesis of new organic heterocyclic compounds for EL device application. Their insightful speeches had triggered heated discussion in the third session of the conference. Every participant praised this conference for disseminating useful and insightful knowledge.The proceedings are a compilation of the accepted papers and represent an interesting outcome of the conference. Topics include but are not limited to the following areas: New Materials and Advanced Materials, Advanced Design Technology, Manufacturing Systems and Automation and other related topics. All the papers have been through rigorous review and process to meet the requirements of international publication standard.We would like to acknowledge all of those who supported ICAMMT 2022. The help and contribution of each individual and institution was instrumental in the success of the conference. In particular, we would like to thank the organizing committee for its valuable inputs in shaping the conference program and reviewing the submitted papers.The Committee of ICAMMT 2022List of Committee member is available in this Pdf.

Modeling and experimental investigation of electromechanical properties of scleral tissue; a CEM model using an anisotropic hyperelastic constitutive relation.

The sclera is a soft tissue primarily consisting of collagen fibers, elastin, and proteoglycans. The proteoglycans are composed of a core protein and negatively chargedglycosaminoglycan side chains. The fixed electric charges inside the scleral extracellular matrix play a key role in its swelling and are expected to cause the tissue to deform in response to an electric field. However, the electroactive response of the sclera has not yet been investigated. The present work experimentally demonstrates that sclera behaves similar to an anionic electrosensitive hydrogel and develops a chemo-electro-mechanical(CEM) mathematical framework for its electromechanical response. In the numerical model, a hyperelastic constitutive law with distributed collagen fibers is used to capture the nonlinear mechanical properties of the sclera, and the coupled Poisson-Nernst-Planck equations represent the distribution of mobile ions throughout the domain. After calibrating the proposed numerical CEMmodel against the experimental measurements, we employ it to investigate the effects of different parameters on the scleral electromechanical response including the voltage and fixed charge density. The experimental and numerical findings of the present study confirm that sclera behaves as an electroactive hydrogel and provide new insight into the mechanical response of this ocular tissue.

Smart carboxymethyl cellulose/polythiophene hydrogel for electrically driven soft actuators: Physical and thermal properties and electroactive performances

AbstractNovel electroactive hydrogels were fabricated from carboxymethyl cellulose (CMC) biopolymer incorporated with conductive polythiophene (PTh). The PTh particles dispersed uniformly in the CMC matrix providing higher mechanical properties and thermal stability. The formulation CMC/PTh6 (6%wt PTh) gave the highest tensile strength and elongation at break (0.9456 ± 0.0017 MPa and 123.0398 ± 7.0606%, respectively). The bending response of the hydrogels under an applied electric field was studied in terms of bending angle and bending sensitivity. Under an electric field strength of 100 V mm−1, CMC/PTh10 (10%wt PTh) showed the highest bending angle (52.245 ± 6.054°) while neat CMC gave the lowest bending angle (33.753 ± 8.116°). The bending behavior upon the application of an electric field of the CMC/PTh hydrogels occurs from the polarization of Na+ and H+ in the CMC matrix and S+ in PTh.

Self‐actuating multilayer scaffold for skeletal muscle tissue engineering

AbstractElectroactive polymers (EAP) can alter and change their shape when subjected to an electric field, they have been investigated for a variety of purposes including smart drug delivery and artificial muscles. However, approaches to design electroactive hydrogel structures can be hindered by low polymeric conductivity, which then requires high electrical input to induce movement and results in low cellular viability. Our purpose in this study, was to reduce the input voltage required for movement by layering electroactive PEGDA:Acrylic acid (PEGDA:AA) with poly(ethylene glycol) diacrylate (PEGDA) modified with a conductive nanocomposite of colloidal poly(3,4 ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) and graphene oxide (GO). In this study PEDOT:PSS/GO was a flexible electrode that stimulated the PEGDA:AA. The multilayered hydrogel was evaluated for angular movement, electrical properties, and biocompatibility with C2C12 myoblast cells. The data showed that increasing the PEDOT:PSS/GO in the hydrogel decreased the conductivity, potentially due to the presence of GO. The addition of PEDOT:PSS/GO increased scaffold movement compared with PEGDA:AA alone when stimulated at 1 V. Fewer scaffolds displayed significantly more movement with increased voltage, but the 10% PEDOT:PSS/GO group experienced more movement at each tested voltage. C2C12 cells on the 10% PEDOT:PSS/GO were more metabolically active than cells on scaffolds with increased concentrations of PEDOT:PSS/GO. This work is an initial step in creating biocompatible scaffolds capable of actuation for tissue engineering.

Piezoelectric Hydrogel for Prophylaxis and Early Treatment of Pressure Injuries/Pressure Ulcers.

Pressure injuries/pressure ulcers (PIs/PUs) are a critical global healthcare issue and represent a considerable burden on healthcare resources. Prevention of PIs/PUs is the least costly approach and minimizes the patient suffering compared with treatment. Besides, sustained tissue load alleviation and microenvironment management are the most crucial properties for dressings in PI/PU prevention. Hydrogel dressings have attracted a lot of attention to prevent PIs/PUs because of their unique mechanical properties and ability to manage the microenvironment of skin. However, auxiliary prophylaxis and early treatment of PIs/PUs remain a challenge and an acute clinical demand. Here, we report on an electroactive hydrogel with large stretchability (∼380%) and skinlike ductility, and Young's modulus (0.48 ± 0.03 MPa) matches that of human skin (0.5-1.95 MPa). The hydrogel displayed piezoelectric properties and mechanical-electric response stability and sensitivity. Our results indicated that the hydrogel was able to promote in vitro angiogenesis under piezoelectric stimulation and exhibited biocompatibility, which has the potential for forming fine vessels at the damaged sites of PIs/PUs. Furthermore, finite element analysis and pressure dispersion experiments demonstrated that the hydrogel was suitable for preventing PIs/PUs by redistributing force, reducing tissue distortion, and maintaining the microenvironment for skin. This work offers a new strategy for designing and evaluating the dressing for prophylaxis and the early treatment of PIs/PUs.

3D-Printed Electroactive Hydrogel Architectures with Sub-100µm Resolution Promote Myoblast Viability.

3D-printed hydrogel scaffolds functionalized with conductive polymers have demonstrated significant potential in regenerative applications for their structural tunability, physiochemical compatibility, and electroactivity. Controllably generating conductive hydrogels with fine features, however, has proven challenging. Here, micro-continuous liquid interface production (μCLIP) method is utilized to 3D print poly(2-hydroxyethyl methacrylate) (pHEMA) hydrogels. With a unique in-situ polymerization approach, a sulfonated monomer is first incorporated into the hydrogel matrix and subsequently polymerized into a conjugated polyelectrolyte, poly(4-(2,3-dihydro-thieno[3,4-b][1,4]dioxin-2-ylmethoxy)-butane-1 sulfonic acid sodium salt (PEDOT-S). Rod structures are fabricated at different crosslinking levels to investigate PEDOT-S incorporation and its effect on bulk hydrogel electronic and mechanical properties. After demonstrating that PEDOT-S does not significantly compromise the structures of the bulk material, pHEMA scaffolds are fabricated via μCLIP with features smaller than 100µm. Scaffold characterization confirms PEDOT-S incorporation bolstered conductivity while lowering overall modulus. Finally, C2C12 myoblasts are seeded on PEDOT-pHEMA structures to verify cytocompatibility and the potential of this material in future regenerative applications. PEDOT-pHEMA scaffolds promote increased cell viability relative to their non-conductive counterparts and differentially influence cell organization. Taken together, this study presents a promising new approach for fabricating complex conductive hydrogel structures for regenerative applications.

Thermosensitive chitosan/poly(N-isopropyl acrylamide) nanoparticles embedded in aniline pentamer/silk fibroin/polyacrylamide as an electroactive injectable hydrogel for healing critical-sized calvarial bone defect in aging rat model

Thermosensitive nanoparticles with phase transition abilities have been considered as suitable materials in biomedical fields, especially drug delivery systems. Moreover, electroactive injectable hydrogels supporting bone regeneration of the elderly will highly be desired in bone tissue engineering applications. Herein, thermosensitive nanoparticles were fabricated using chitosan/poly(N-isopropyl acrylamide) for simvastatin acid delivery. The nanoparticles were incorporated into electroactive injectable hydrogels based on aniline pentamer/silk fibroin/polyacrylamide containing vitamin C. The nanoparticles had thermosensitive properties as simvastatin acid had higher release rates at 37 than 23 °C without significant burst release. The hydrogels also revealed an appropriate gelation time, stable mechanical and rheological characteristics, high water absorbency, and proper biodegradability. In vitro studies indicated that the hydrogel was biocompatible and nontoxic, especially those containing drugs. Implantation of the hydrogels containing both simvastatin acid and vitamin C into the critical calvarial bone defect of the aged rat also demonstrated significant enhancement of bone healing after 4 and 8 weeks post-implantation. We found that the electroactive injectable hydrogels containing thermosensitive nanoparticles exhibited great potential for treating bone defects in the elderly rats

Electrical stimulation induced by a piezo-driven triboelectric nanogenerator and electroactive hydrogel composite, accelerate wound repair

Among the numerous types of chronic skin wounds, the treatment of diabetic foot ulcers (DFU) remains a major challenge, in view of its etiology. The high rates of amputation even with the best therapeutic regimens suggest the urgent need for newer approaches. Despite improvement in wound healing with electrical stimulation (ES), it is rarely used in therapy. The advent of wearable devices has renewed interest in this modality of therapy. Whereas such devices focus on ES alone, herein we demonstrate an interactive wound dressing that is capable of providing both ES and an optimal environment for faster healing. The composite dressing containing a conducting hydrogel component constructed with carbonized polydopamine/polydopamine/ polyacrylamide and paired with electroactive electrospun poly(vinylidene fluoride) (PVDF) membrane was capable of generating electrical impulses in response to biomechanical activities. The adhesive and stretchable hydrogel, imparted a moist wound environment apart from protection from bacteria and served as an electrode to direct the electrical impulses generated by the PVDF membrane to the underlying wound due to triboelectrification. The robust mechanical strength of the hydrogel could support physical activities such as walking, stretching etc. The biocompatible dressing encouraged cell growth and migration. The potential of the dressing to improve healing was confirmed in an excisional skin wound model. Evidence of improved re-epithelialization, vascularization and remodeling in wounds covered with the dressing indicated the importance of providing both electrical stimulation and optimal wound environment for faster healing. The proposed approach of using a triboelectric nanogenerator and a conducting hydrogel could aid in the repair of hard-to-heal wounds, such as diabetic foot ulcers.

Nanocomposite hydrogels of gellan gum and polypyrrole for electro-stimulated ibuprofen release application

The development of stimuli-responsive release systems as functional platforms for controlled drug delivery is a valuable contribution to modern-day medical practice. In this work, novel electroactive nanocomposite hydrogels were prepared by encapsulating green-synthesized polypyrrole (PPy) colloids within bioamine-crosslinked gellan gum (GG) networks. The structural, physicochemical, and morphological properties of GG/PPy hydrogels were studied by Fourier transform infrared spectroscopy, thermogravimetry, rheological analysis, scanning electron microscopy, and swelling kinetic measurements. The hydrogels exhibited an interconnected porous structure with undefined boundaries. Viscoelastic properties and swelling behavior of materials were dependent on their filler content. In vitro ibuprofen (IBP) release studies from hydrogels were carried out without and under different electrical stimulations. The IBP release kinetic from GG/PPy hydrogels was remarkably activated by electrical stimuli. A unique pulse potential of 5 V increased the drug delivery up to 63% from nanocomposite hydrogel, in contrast to the low IBP amount released in a passive form (10%). The PPy reduction played a determining role as the main driving force in drug release activation. The tuning release profiles evidenced the potential of materials for electrically controlled drug delivery in implantable or transdermal drug release devices.

Electroactive calcium-alginate/polycaprolactone/reduced graphene oxide nanohybrid hydrogels for skeletal muscle tissue engineering

Graphene derivatives such as reduced graphene oxide (rGO) are used as components of novel biomaterials for their unique electrical properties. Electrical conductivity is a crucial factor for muscle cells, which are electrically active. This study reports the development of a new type of semi-interpenetrated polymer network based on two biodegradable FDA-approved biomaterials, sodium alginate (SA) and polycaprolactone (PCL), with Ca2+ ions as SA crosslinker. Several drawbacks such as the low cell adhesion of SA and weak structural stability can be improved with the incorporation of PCL. Furthermore, this study demonstrates how this semi-IPN can be engineered with rGO nanosheets (0.5% and 2% wt/wt rGO nanosheets) to produce electroactive nanohybrid composite biomaterials. The study focuses on the microstructure and the enhancement of physical and biological properties of these advanced materials, including water sorption, surface wettability, thermal behavior and thermal degradation, mechanical properties, electrical conductivity, cell adhesion and myogenic differentiation. The results suggest the formation of a complex nano-network with different interactions between the components: bonds between SA chains induced by Ca2+ ions (egg-box model), links between rGO nanosheets and SA chains as well as between rGO nanosheets themselves through Ca2+ ions, and strong hydrogen bonding between rGO nanosheets and SA chains. The incorporation of rGO significantly increases the electrical conductivity of the nanohybrid hydrogels, with values in the range of muscle tissue. In vitro cultures with C2C12 murine myoblasts revealed that the conductive nanohybrid hydrogels are not cytotoxic and can greatly enhance myoblast adhesion and myogenic differentiation. These results indicate that these novel electroactive nanohybrid hydrogels have great potential for biomedical applications related to the regeneration of electroactive tissues, particularly in skeletal muscle tissue engineering.

MXene (Ti3C2Tx)-Embedded Nanocomposite Hydrogels for Biomedical Applications: A Review.

Polymeric nanocomposites have been outstanding functional materials and have garnered immense attention as sustainable materials to address multi-disciplinary problems. MXenes have emerged as a newer class of 2D materials that produce metallic conductivity upon interaction with hydrophilic species, and their delamination affords monolayer nanoplatelets of a thickness of about one nm and a side size in the micrometer range. Delaminated MXene has a high aspect ratio, making it an alluring nanofiller for multifunctional polymer nanocomposites. Herein, we have classified and discussed the structure, properties and application of major polysaccharide-based electroactive hydrogels (hyaluronic acid (HA), alginate sodium (SA), chitosan (CS) and cellulose) in biomedical applications, starting with the brief historical account of MXene’s development followed by successive discussions on the synthesis methods, structures and properties of nanocomposites encompassing polysaccharides and MXenes, including their biomedical applications, cytotoxicity and biocompatibility aspects. Finally, the MXenes and their utility in the biomedical arena is deliberated with an eye on potential opportunities and challenges anticipated for them in the future, thus promoting their multifaceted applications.