Synergistic effects of conductive PVA/PEDOT electrospun scaffolds and electrical stimulation for more effective neural tissue engineering

Conductive and alignment-optimized porous fiber conduits with electrical stimulation for peripheral nerve regeneration

Autologous nerve transplantation (ANT) is currently considered the gold standard for treating long-distance peripheral nerve defects. However, several challenges associated with ANT, such as limited availability of donors, donor site injury, mismatched nerve diameters, and local neuroma formation, remain unresolved. To address these issues comprehensively, we have developed porous poly(lactic-co-glycolic acid) (PLGA) electrospinning fiber nerve guide conduits (NGCs) that are optimized in terms of alignment and conductive coating to facilitate peripheral nerve regeneration (PNR) under electrical stimulation (ES). The physicochemical and biological properties of aligned porous PLGA fibers and poly(3,4-ethylenedioxythiophene):polystyrene sodium sulfonate (PEDOT:PSS) coatings were characterized through assessments of electrical conductivity, surface morphology, mechanical properties, hydrophilicity, and cell proliferation. Material degradation experiments demonstrated the biocompatibility in vivo of electrospinning fiber films with conductive coatings. The conductive NGCs combined with ES effectively facilitated nerve regeneration. The designed porous aligned NGCs with conductive coatings exhibited suitable physicochemical properties and excellent biocompatibility, thereby significantly enhancing PNR when combined with ES. This combination of porous aligned NGCs with conductive coatings and ES holds great promise for applications in the field of PNR.

Conducting polymer scaffolds: a new frontier in bioelectronics and bioengineering

Conducting polymer (CP) scaffolds have emerged as a transformative tool in bioelectronics and bioengineering, advancing the ability to interface with biological systems. Their unique combination of electrical conductivity, tailorability, and biocompatibility surpasses the capabilities of traditional nonconducting scaffolds while granting them access to the realm of bioelectronics. This review examines recent developments in CP scaffolds, focusing on material and device advancements, as well as their interplay with biological systems. We highlight applications for monitoring, tissue stimulation, and drug delivery and discuss perspectives and challenges currently faced for their ultimate translation and clinical implementation.

Machine learning-guided morphological property prediction of 2D electrospun scaffolds: the effect of polymer chemical composition and processing parameters

Among various methods for fabricating polymeric tissue engineering scaffolds, electrospinning stands out as a relatively simple technique widely utilized in research. Numerous studies have delved into understanding how electrospinning processing parameters and specific polymeric solutions affect the physical features of the resulting scaffolds. However, owing to the complexity of these interactions, no definitive approaches have emerged. This study introduces the use of Simplified Molecular Input Line Entry System (SMILES) encoding method to represent materials, coupled with machine learning algorithms, to model the relationships between material properties, electrospinning parameters and scaffolds' physical properties. Here, the scaffolds' fiber diameter and conductivity have been predicted for the first time using this approach. In the classification task, the voting classifier predicted the fibers diameter with a balanced accuracy score of 0.9478. In the regression task, a neural network regressor was architected to learn the relations between parameters and predict the fibers diameter with R2 = 0.723. In the case of fibers conductivity, regressor and classifier models were used for prediction, but the performance fluctuated due to the inadequate information in the published data and the collected dataset. Finally, the model prediction accuracy was validated by experimental electrospinning of a biocompatible polymer (i.e., polyvinyl alcohol and polyvinyl alcohol/polypyrrole). Field-emission scanning electron microscope (FE-SEM) images were used to measure fiber diameter. These results demonstrated the efficacy of the proposed model in predicting the polymer nanofiber diameter and reducing the parameter space prior to the scoping exercises. This data-driven model can be readily extended to the electrospinning of various biopolymers.

Electroconductive Nanofibrous Scaffolds Enable Neuronal Differentiation in Response to Electrical Stimulation without Exogenous Inducing Factors

Among the various biochemical and biophysical inducers for neural regeneration, electrical stimulation (ES) has recently attracted considerable attention as an efficient means to induce neuronal differentiation in tissue engineering approaches. The aim of this in vitro study was to develop a nanofibrous scaffold that enables ES-mediated neuronal differentiation in the absence of exogenous soluble inducers. A nanofibrous scaffold composed of polycaprolactone (PCL), poly-L-lactic acid (PLLA), and single-walled nanotubes (SWNTs) was fabricated via electrospinning and its physicochemical properties were investigated. The cytocompatibility of the electrospun composite with the PC12 cell line and bone marrow-derived mesenchymal stem cells (BMSCs) was investigated. The results showed that the PCL/PLLA/SWNT nanofibrous scaffold did not exhibit cytotoxicity and supported cell attachment, spreading, and proliferation. ES was applied to cells cultured on the nanofibrous scaffolds at different intensities and the expression of the three neural markers (Nestin, Microtubule-associated protein 2, and β tubulin-3) was evaluated using RT-qPCR analysis. The results showed that the highest expression of neural markers could be achieved at an electric field intensity of 200 mV/cm, suggesting that the scaffold in combination with ES can be an efficient tool to accelerate neural differentiation in the absence of exogenous soluble inducers. This has important implications for the regeneration of nerve injuries and may provide insights for further investigations of the mechanisms underlying ES-mediated neuronal commitment.

Review on electrically conductive smart nerve guide conduit for peripheral nerve regeneration

At present, peripheral nerve injuries (PNIs) are one of the leading causes of substantial impairment around the globe. Complete recovery of nerve function after an injury is challenging. Currently, autologous nerve grafts are being used as a treatment; however, this has several downsides, for example, donor site morbidity, shortage of donor sites, loss of sensation, inflammation, and neuroma development. The most promising alternative is the development of a nerve guide conduit (NGC) to direct the restoration and renewal of neuronal axons from the proximal to the distal end to facilitate nerve regeneration and maximize sensory and functional recovery. Alternatively, the response of nerve cells to electrical stimulation (ES) has a substantial regenerative effect. The incorporation of electrically conductive biomaterials in the fabrication of smart NGCs facilitates the function of ES throughout the active proliferation state. This article overviews the potency of the various categories of electroactive smart biomaterials, including conductive and piezoelectric nanomaterials, piezoelectric polymers, and organic conductive polymers that researchers have employed latterly to fabricate smart NGCs and their potentiality in future clinical application. It also summarizes a comprehensive analysis of the recent research and advancements in the application of ES in the field of NGC.

Conducting polymer-based scaffolds for neuronal tissue engineering

Neuronal tissue engineering has immense potential for treating neurological disorders and facilitating nerve regeneration. Conducting polymers (CPs) have emerged as a promising class of materials owing to their unique electrical conductivity and biocompatibility. CPs, such as poly(3,4-ethylenedioxythiophene) (PEDOT), poly(3-hexylthiophene) (P3HT), polypyrrole (PPy), and polyaniline (PANi), have been extensively explored for their ability to provide electrical cues to neural cells. These polymers are widely used in various forms, including porous scaffolds, hydrogels, and nanofibers, and offer an ideal platform for promoting cell adhesion, differentiation, and axonal outgrowth. CP-based scaffolds can also serve as drug delivery systems, enabling localized and controlled release of neurotrophic factors and therapeutic agents to enhance neural regeneration and repair. CP-based scaffolds have demonstrated improved neural regeneration, both in vitro and in vivo, for treating spinal cord and peripheral nerve injuries. In this review, we discuss synthesis and scaffold processing methods for CPs and their applications in neuronal tissue regeneration. We focused on a detailed literature review of the central and peripheral nervous systems.

PEDOT-Coated PLA Fibers Electrospun from Solutions Incorporating Fe(III)Tosylate in Different Solvents by Vapor-Phase Polymerization for Neural Regeneration

Therapeutic solutions for injuries in the peripheral nervous system are limited and not existing in the case of the central nervous system. The electrical stimulation of cells through a cell-supporting conductive scaffold may contribute to new therapeutic solutions for nerve regeneration. In this work, biocompatible Polylactic acid (PLA) fibrous scaffolds incorporating Fe(III)Tosylate (FeTos) were produced by electrospinning a mixture of PLA/FeTos solutions towards a rotating cylinder, inducing fiber alignment. Fibers were coated with the conductive polymer Poly(3,4 ethylenedioxythiophene) (PEDOT) formed by vapor-phase polymerization of EDOT at 70 °C for 2 h. Different solvents (ETH, DMF and THF) were used as FeTos solvents to investigate the impact on the scaffold's conductivity. Scaffold conductivity was estimated to be as high as 1.50 × 10-1 S/cm when FeTos was dissolved in DMF. In vitro tests were performed to evaluate possible scaffold cytotoxicity, following ISO 10993-5, revealing no cytotoxic effects. Differentiation and growth of cells from the neural cell line SH-SY5Y seeded on the scaffolds were also assessed, with neuritic extensions observed in cells differentiated in neurons with retinoic acid. These extensions tended to follow the preferential alignment of the scaffold fibers.

Wound healing performance of electrospun PVA/70S30C bioactive glass/Ag nanoparticles mats decorated with curcumin: In vitro and in vivo investigations

Biocompatible fibrous scaffold containing polyvinyl alcohol (PVA), 70S30C bioactive glass (BG), silver (Ag) nanoparticles and curcumin (Cur) was fabricated through electrospinning method. Scanning electron microscope (SEM) and Field emission scanning electron microscopy (FESEM) were employed to investigate the morphological characteristics of the scaffolds. In addition, biodegradability, hydrophilicity, and contact angle were studied as criteria for evaluating physical properties of the scaffolds. Tensile strength was reported to be 0.971 ± 0.093 MPa. Also, the viability of fibroblasts after 7 days of cell culture was 93.58 ± 1.36 %. The antibacterial activity against Escherichia coli and Staphylococcus aureus bacteria was illustrated using inhibition zones of 13.12 ± 0.69 and 14.21 ± 1.37 mm, respectively. Histological results revealed that tissue regeneration after 14 days of surgery was much higher for the dressing group compared to the blank group. According to the obtained results, the authors introduce the PVA-BG-Ag-Cur scaffold as a promising candidate for skin tissue engineering applications.

Biomimetic alginate-based electroconductive nanofibrous scaffolds for bone tissue engineering application

Novel electrically conductive nanofibrous scaffolds were designed and fabricated through the grafting of aniline monomer onto a phenylamine-functionalized alginate (Alg-NH2) followed by electrospinning with poly(vinyl alcohol) (PVA). Performance of the prepared scaffolds in bone tissue engineering (TE) were studied in terms of physicochemical (e.g., conductivity, electroactivity, morphology, hydrophilicity, water uptake, and mechanical) and biological (cytocompatibility, in vitro biodegradability, cells attachment and proliferation, hemolysis, and protein adsorption) properties. The contact angles of the scaffolds with water drop were obtained about 50 to 60° that confirmed their excellent hydrophilicities for TE applications. Three dimensional (3D), inter-connected and uniform porous structures of the scaffolds without any bead formation was confirmed by scanning electron microscopy (SEM). Electrical conductivities of the fabricated scaffolds were obtained as 1.5 × 10-3 and 2.7 × 10-3 Scm-1. MTT assay results revealed that the scaffolds have acceptable cytocompatibilities and can enhance the cells adhesion as well as proliferation, which approved their potential for TE applications. Hemolysis rate of the developed scaffolds were quantified <2 % even at high concentration (200 μgmL-1) of samples that approved their hemocompatibilities. The scaffolds were also exhibited acceptable protein adsorption capacities (65 and 68 μgmg-1). As numerous experimental results, the developed scaffolds have acceptable potential for bone TE.

Novel Electroactive Mineralized Polyacrylonitrile/PEDOT:PSS Electrospun Nanofibers for Bone Repair Applications

Bone defect repair remains a critical challenge in current orthopedic clinical practice, as the available therapeutic strategies only offer suboptimal outcomes. Therefore, bone tissue engineering (BTE) approaches, involving the development of biomimetic implantable scaffolds combined with osteoprogenitor cells and native-like physical stimuli, are gaining widespread interest. Electrical stimulation (ES)-based therapies have been found to actively promote bone growth and osteogenesis in both in vivo and in vitro settings. Thus, the combination of electroactive scaffolds comprising conductive biomaterials and ES holds significant promise in improving the effectiveness of BTE for clinical applications. The aim of this study was to develop electroconductive polyacrylonitrile/poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PAN/PEDOT:PSS) nanofibers via electrospinning, which are capable of emulating the native tissue's fibrous extracellular matrix (ECM) and providing a platform for the delivery of exogenous ES. The resulting nanofibers were successfully functionalized with apatite-like structures to mimic the inorganic phase of the bone ECM. The conductive electrospun scaffolds presented nanoscale fiber diameters akin to those of collagen fibrils and displayed bone-like conductivity. PEDOT:PSS incorporation was shown to significantly promote scaffold mineralization in vitro. The mineralized electroconductive nanofibers demonstrated improved biological performance as observed by the significantly enhanced proliferation of both human osteoblast-like MG-63 cells and human bone marrow-derived mesenchymal stem/stromal cells (hBM-MSCs). Moreover, mineralized PAN/PEDOT:PSS nanofibers up-regulated bone marker genes expression levels of hBM-MSCs undergoing osteogenic differentiation, highlighting their potential as electroactive biomimetic BTE scaffolds for innovative bone defect repair strategies.

Tuning of Morphological and Antibacterial Properties of Poly(3,4-ethylenedioxythiophene):Peroxodisulfate by Methyl Violet

This study demonstrates a one-step synthesis of poly(3,4-ethylenedioxythiophene) (PEDOT) in the presence of the methyl violet (MV) dye. The structural properties of PEDOT:peroxodisulfate were studied using Raman and MALDI-TOF spectroscopies. The use of the MV dye in the polymerization process resulted in a change in the typical irregular morphology of PEDOT:peroxodisulfate, leading to the formation of spherical patterns. SEM and TEM analyses revealed that increasing the dye concentration can produce larger spherical aggregates probably due to the hydrophobic and π-π interactions. These larger aggregates hindered the charge transport and reduced the electrical conductivity. Interestingly, at higher dye concentrations (0.05 and 0.075 M), the PEDOT:peroxodisulfate/MV films exhibited significantly improved antibacterial activity against Staphylococcus aureus and Escherichia coli. Furthermore, the PEDOT:peroxodisulfate films with the incorporated MV dye exhibited a well-defined and repeatable redox behavior. The remarkable amalgamation of their optical, electrochemical and antibacterial properties provides the PEDOT:peroxodisulfate/MV materials with an immensely diverse spectrum of applications, including in optical sensors and medical devices.

Production of Blended Poly(acrylonitrile): Poly(ethylenedioxythiophene):Poly(styrene sulfonate) Electrospun Fibers for Neural Applications

This study describes, for the first time, the successful incorporation of poly(ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) in Poly(acrylonitrile) (PAN) fibers. While electroconductive PEDOT:PSS is extremely challenging to electrospun into fibers. Therefore, PAN, a polymer easy to electrospun, was chosen as a carrier due to its biocompatibility and tunable chemical stability when cross-linked, particularly using strong acids. PAN:PEDOT:PSS blends, prepared from PEDOT:PSS Clevios PH1000, were electrospun into fibers (PH1000) with a diameter of 515 ± 120 nm, which after being thermally annealed (PH1000 24H) and treated with heated sulfuric acid (PH1000 H₂SO₄), resulted in fibers with diameters of 437 ± 109 and 940 ± 210 nm, respectively. The fibers obtained over the stepwise process were characterized through infra-red/Raman spectroscopy and cyclic voltammetry. The final fiber meshes showed enhanced electroconductivity (3.2 × 10^-3 S cm^-1, four-points-assay). Fiber meshes biocompatibility was evaluated using fibroblasts and neural stem cells (NSCs) following, respectively, the ISO10993 guidelines and standard adhesion/proliferation assay. NSCs cultured on PH1000 H₂SO₄ fibers presented normal morphology and high proliferation rates (0.37 day^-1 vs. 0.16 day^-1 for culture plate), indicating high biocompatibility for NSCs. Still, the low initial NSC adhesion of 7% calls for improving seeding methodologies. PAN:PEDOT:PSS fibers, here successful produced for the first time, have potential applications in neural tissue engineering and soft electronics.

Transcriptomic and in vivo approaches introduced human iPSC-derived microvesicles for skin rejuvenation

The skin undergoes the formation of fine lines and wrinkles through the aging process; also, burns, trauma, and other similar circumstances give rise to various forms of skin ulcers. Induced pluripotent stem cells (iPSCs) have become promising candidates for skin healing and rejuvenation due to not stimulating inflammatory responses, low probability of immune rejection, high metabolic activity, good large-scale production capacity and potentials for personalized medicine. iPSCs can secrete microvesicles (MVs) containing RNA and proteins responsible for the normal repairing process of the skin. This study aimed to evaluate the possibility, safety and effectiveness of applying iPSCs-derived MVs for skin tissue engineering and rejuvenation applications. The possibility was assessed using the evaluation of the mRNA content of iPSC-derived MVs and the behavior of fibroblasts after MV treatment. Investigating the effect of microvesicle on stemness potential of mesenchymal stem cells was performed for safety concerns. In vivo evaluation of MVs was done in order to investigate related immune response, re-epithelialization and blood vessel formation to measure effectiveness. Shedding MVs were round in shape distributed in the range from 100 to 1000 nm in diameter and positive for AQP3, COL2A, FGF2, ITGB, and SEPTIN4 mRNAs. After treating dermal fibroblasts with iPSC-derived MVs, the expressions of collagens Iα1 and III transcripts (as the main fibrous extracellular matrix (ECM) proteins) were upregulated. Meanwhile, the survival and proliferation of MV treated fibroblasts did not change significantly. Evaluation of stemness markers in MV treated MSCs showed negligible alteration. In line with in vitro results, histomorphometry and histopathology findings also confirmed the helpful effect of MVs in skin regeneration in the rat burn wound models. Conducting more investigations on hiPSCs-derived MVs may lead to produce more efficient and safer biopharmaceutics for skin regeneration in the pharmaceutical market.

Polyvinyl Alcohol Nanofibers Blends as Drug Delivery System in Tissue Regeneration

Nanofibers have shown promising clinical results in the process of tissue regeneration since they provide a similar structure to the extracellular matrix of different tissues, high surface-to-volume ratio and porosity, flexibility, and gas permeation, offering topographical features that stimulate cell adhesion and proliferation. Electrospinning is one of the most used techniques for manufacturing nanomaterials due to its simplicity and low cost. In this review, we highlight the use of nanofibers produced with polyvinyl alcohol and polymeric associations (PVA/blends) as a matrix for release capable of modifying the pharmacokinetic profile of different active ingredients in the regeneration of connective, epithelial, muscular, and nervous tissues. Articles were selected by three independent reviewers by analyzing the databases, such as Web of Science, PubMed, Science Direct, and Google Scholar (last 10 years). Descriptors used were "nanofibers", "poly (vinyl alcohol)", "muscle tissue", "connective tissue", "epithelial tissue", and "neural tissue engineering". The guiding question was: How do different compositions of polyvinyl alcohol polymeric nanofibers modify the pharmacokinetics of active ingredients in different tissue regeneration processes? The results demonstrated the versatility of the production of PVA nanofibers by solution blow technique with different actives (lipo/hydrophilic) and with pore sizes varying between 60 and 450 nm depending on the polymers used in the mixture, which influences the drug release that can be controlled for hours or days. The tissue regeneration showed better cellular organization and greater cell proliferation compared to the treatment with the control group, regardless of the tissue analyzed. We highlight that, among all blends, the combinations PVA/PCL and PVA/CS showed good compatibility and slow degradation, indicating their use in prolonged times of biodegradation, thus benefiting tissue regeneration in bone and cartilage connective tissues, acting as a physical barrier that results in guided regeneration, and preventing the invasion of cells from other tissues with increased proliferation rate.

Overview of Electrospinning for Tissue Engineering Applications

Tissue engineering (TE) is an emerging field of study that incorporates the principles of biology, medicine, and engineering for designing biological substitutes to maintain, restore, or improve tissue functions with the goal of avoiding organ transplantation. Amongst the various scaffolding techniques, electrospinning is one of the most widely used techniques to synthesise a nanofibrous scaffold. Electrospinning as a potential tissue engineering scaffolding technique has attracted a great deal of interest and has been widely discussed in many studies. The high surface-to-volume ratio of nanofibres, coupled with their ability to fabricate scaffolds that may mimic extracellular matrices, facilitates cell migration, proliferation, adhesion, and differentiation. These are all very desirable properties for TE applications. However, despite its widespread use and distinct advantages, electrospun scaffolds suffer from two major practical limitations: poor cell penetration and poor load-bearing applications. Furthermore, electrospun scaffolds have low mechanical strength. Several solutions have been offered by various research groups to overcome these limitations. This review provides an overview of the electrospinning techniques used to synthesise nanofibres for TE applications. In addition, we describe current research on nanofibre fabrication and characterisation, including the main limitations of electrospinning and some possible solutions to overcome these limitations.

Recent progress in the manipulation of biochemical and biophysical cues for engineering functional tissues

Tissue engineering (TE) is currently considered a cutting-edge discipline that offers the potential for developing treatments for health conditions that negatively affect the quality of life. This interdisciplinary field typically involves the combination of cells, scaffolds, and appropriate induction factors for the regeneration and repair of damaged tissue. Cell fate decisions, such as survival, proliferation, or differentiation, critically depend on various biochemical and biophysical factors provided by the extracellular environment during developmental, physiological, and pathological processes. Therefore, understanding the mechanisms of action of these factors is critical to accurately mimic the complex architecture of the extracellular environment of living tissues and improve the efficiency of TE approaches. In this review, we recapitulate the effects that biochemical and biophysical induction factors have on various aspects of cell fate. While the role of biochemical factors, such as growth factors, small molecules, extracellular matrix (ECM) components, and cytokines, has been extensively studied in the context of TE applications, it is only recently that we have begun to understand the effects of biophysical signals such as surface topography, mechanical, and electrical signals. These biophysical cues could provide a more robust set of stimuli to manipulate cell signaling pathways during the formation of the engineered tissue. Furthermore, the simultaneous application of different types of signals appears to elicit synergistic responses that are likely to improve functional outcomes, which could help translate results into successful clinical therapies in the future.

Methods of poly(3,4)-ethylenedioxithiophene (PEDOT) electrodeposition on metal electrodes for neural stimulation and recording

Conductive polymers are of great interest in the field of neural electrodes because of their potential to improve the interfacial properties of electrodes. In particular, the conductive polymer poly (3,4)-ethylenedioxithiophene (PEDOT) has been widely studied for neural applications.Objective:This review compares methods for electrodeposition of PEDOT on metal neural electrodes, and analyses the effects of deposition methods on morphology and electrochemical performance.Approach:Electrochemical performances were analysed against several deposition method choices, including deposition charge density and co-ion, and correlations were explained to morphological and structural arguments as well as characterisation methods choices.Main results:Coating thickness and charge storage capacity are positively correlated with PEDOT electrodeposition charge density. We also show that PEDOT coated electrode impedance at 1 kHz, the only consistently reported impedance quantity, is strongly dependent upon electrode radius across a wide range of studies, because PEDOT coatings reduces the reactance of the complex impedance, conferring a more resistive behaviour to electrodes (at 1 kHz) dominated by the solution resistance and electrode geometry. This review also summarises how PEDOT co-ion choice affects coating structure and morphology and shows that co-ions notably influence the charge injection limit but have a limited influence on charge storage capacity and impedance. Finally we discuss the possible influence of characterisation methods to assess the robustness of comparisons between published results using different methods of characterisation.Significance:This review aims to serve as a common basis for researchers working with PEDOT by showing the effects of deposition methods on electrochemical performance, and aims to set a standard for accurate and uniform reporting of methods.

Nanocomposite Bioprinting for Tissue Engineering Applications

Bioprinting aims to provide new avenues for regenerating damaged human tissues through the controlled printing of live cells and biocompatible materials that can function therapeutically. Polymeric hydrogels are commonly investigated ink materials for 3D and 4D bioprinting applications, as they can contain intrinsic properties relative to those of the native tissue extracellular matrix and can be printed to produce scaffolds of hierarchical organization. The incorporation of nanoscale material additives, such as nanoparticles, to the bulk of inks, has allowed for significant tunability of the mechanical, biological, structural, and physicochemical material properties during and after printing. The modulatory and biological effects of nanoparticles as bioink additives can derive from their shape, size, surface chemistry, concentration, and/or material source, making many configurations of nanoparticle additives of high interest to be thoroughly investigated for the improved design of bioactive tissue engineering constructs. This paper aims to review the incorporation of nanoparticles, as well as other nanoscale additive materials, to printable bioinks for tissue engineering applications, specifically bone, cartilage, dental, and cardiovascular tissues. An overview of the various bioinks and their classifications will be discussed with emphasis on cellular and mechanical material interactions, as well the various bioink formulation methodologies for 3D and 4D bioprinting techniques. The current advances and limitations within the field will be highlighted.

Fabrication Methods of Electroactive Scaffold-Based Conducting Polymers for Tissue Engineering Application: A Review

Conductive scaffolds, defined as scaffold systems capable of carrying electric current, have been extensively researched for tissue engineering applications. Conducting polymers (CPs) as components of conductive scaffolds was introduced to improve morphology or cell attachment, conductivity, tissue growth, and healing rate, all of which are beneficial for cardiac, muscle, nerve, and bone tissue management. Conductive scaffolds have become an alternative for tissue replacement, and repair, as well as to compensate for the global organ shortage for transplantation. Previous researchers have presented a wide range of fabrication methods for conductive scaffolds. This review highlights the most recent advances in developing conductive scaffolds, with the aim to trigger more theoretical and experimental work to address the challenges and prospects of these new fabrication techniques in medical sciences.

Nanocomposite pectin fibers incorporating folic acid-decorated carbon quantum dots

Pectin has recently attracted increasing attention as an alternative biomaterial commonly used in biomedical and pharmaceutical fields. It shows several promising properties, including good biocompatibility, health benefits, nontoxicity, and biodegradation. In this research, novel nanocomposite fibers composed of folic acid-decorated carbon dots (CDs) in pectin/PEO matrix were fabricated using the electrospinning technique, which was never reported previously. Nitrogen-doped and nitrogen, sulfur-doped CDs were synthesized with average diameters of 2.74 nm and 2.17 nm using the one-step hydrothermal method, studied regarding their physicochemical, optical, and biocompatibility properties. The relative Quantum yields of N-CDs and N, S doped CDs were measured to be 54.7 % and 30.2 %, respectively. Nanocomposite fibers containing CDs were prepared, and their morphology, physicochemical properties, conductivity, drug release behavior, and cell viability were characterized. The results indicated that CDs improve fibrous scaffolds' tensile strength from 13.74 to 35.22 MPa while maintaining comparable extensibility. Furthermore, by incorporation of CDs in the prepared fibers conductivity enhanced from 8.69 × 10^-9 S·m^-1 to 1.36 × 10^-4 S·m^-1. The nanocomposite fibrous scaffold was also biocompatible with controlled drug release over 212 h, potentially promising tissue regeneration.

Protein by-products: Composition, extraction, and biomedical applications

Significant upsurge in animal by-products such as skin, bones, wool, hides, feathers, and fats has become a global challenge and, if not properly disposed of, can spread contamination and viral diseases. Animal by-products are rich in proteins, which can be used as nutritional, pharmacologically functional ingredients, and biomedical materials. Therefore, recycling these abundant and renewable by-products and extracting high value-added components from them is a sustainable approach to reclaim animal by-products while addressing scarce landfill resources. This article appraises the most recent studies conducted in the last five years on animal-derived proteins' separation and biomedical application. The effort encompasses an introduction about the composition, an overview of the extraction and purification methods, and the broad range of biomedical applications of these ensuing proteins.

Neuronal differentiation of mesenchymal stem cells by polyvinyl alcohol/Gelatin/crocin and beta-carotene

BACKGROUND

Nerve tissues are important in coordinating the motions and movements of the body. Nerve tissue repair and regeneration is a slow process that might take a long time and cost a lot of money. As a result, tissue engineering was employed to treat nerve tissue lesions. The aim of this study was to investigate the proliferation of C6 cells and human mesenchymal stem cells derived bone marrow (hBMMSCs) differentiate into neuronal-like cells on the polyvinyl alcohol/gelatin/crocin (PVA/Gel/Cro) nanofiber scaffolds in vitro.

METHODS

PVA/Gel scaffolds containing crocin in three concentrations (1%, 3%, and 5%) were prepared by the electrospinning method. The human bone marrow-derived mesenchymal stem cells (hBMSCs) differentiation on the PVA/Gel/Cro 5% that induced by beta-carotene (βC), was analyzed during 10 days. Morphology of differentiated cells on the scaffolds was taken by scanning electron microscope (SEM). The expression of the neural cell markers was studied by quantitative reverse transcription- polymerase chain reaction (qRT-PCR) and immunocytochemistry (ICC).

RESULTS

MTT results of C6 cells culture on the scaffolds showed that proliferation and metabolic activity on PVA/Gel scaffold containing crocin 5% (PVA/Gel/Cro 5%) are significantly more than the other concentrations (P = 0.01). MSC differentiation to nerve-like cells was approved by MAP-2 expression at the mRNA level and NESTIN and MAP-2 at the protein level.

CONCLUSIONS

These results suggested that PVA/Gel/Cro 5% and βC could lead to hBMSCs differentiation to neural cells.

Mimicking Native Heart Tissue Physiology and Pathology in Silk Fibroin Constructs through a Perfusion-Based Dynamic Mechanical Stimulation Microdevice

In vitro cardiomyocyte (CM) maturation is an imperative step to replicate native heart tissue-like structures as cardiac tissue grafts or as drug screening platforms. CMs are known to interpret biophysical cues such as stiffness, topography, external mechanical stimulation or dynamic perfusion load through mechanotransduction and change their behavior, organization, and maturation. In this regard, a silk-based cardiac tissue (CT) coupled with a dynamic perfusion-based mechanical stimulation platform (DMM) for achieving maturation and functionality in vitro is tried to be delivered. Silk fibroin (SF) is used to fabricate lamellar scaffolds to provide native tissue-like anisotropic architecture and is found to be nonimmunogenic and biocompatible allowing cardiomyocyte attachment and growth in vitro. Further, the scaffolds display excellent mechanical properties by their ability to undergo cyclic compressions without any deformation when places in the DMM. Gradient compression strains (5% to 20%), mimicking the native physiological and pathological conditions, are applied to the cardiomyocyte culture seeded on lamellar silk scaffolds in the DMM. A strain-dependent difference in cardiomyocyte maturation, gene expression, sarcomere elongation, and extracellular matrix formation is observed. These silk-based CTs matured in the DMM can open up several avenues toward the development of host-specific grafts and in vitro models for drug screening.

Organic Bioelectronics for In Vitro Systems

Bioelectronics have made strides in improving clinical diagnostics and precision medicine. The potential of bioelectronics for bidirectional interfacing with biology through continuous, label-free monitoring on one side and precise control of biological activity on the other has extended their application scope to in vitro systems. The advent of microfluidics and the considerable advances in reliability and complexity of in vitro models promise to eventually significantly reduce or replace animal studies, currently the gold standard in drug discovery and toxicology testing. Bioelectronics are anticipated to play a major role in this transition offering a much needed technology to push forward the drug discovery paradigm. Organic electronic materials, notably conjugated polymers, having demonstrated technological maturity in fields such as solar cells and light emitting diodes given their outstanding characteristics and versatility in processing, are the obvious route forward for bioelectronics due to their biomimetic nature, among other merits. This review highlights the advances in conjugated polymers for interfacing with biological tissue in vitro, aiming ultimately to develop next generation in vitro systems. We showcase in vitro interfacing across multiple length scales, involving biological models of varying complexity, from cell components to complex 3D cell cultures. The state of the art, the possibilities, and the challenges of conjugated polymers toward clinical translation of in vitro systems are also discussed throughout.

A review on advances in the applications of spider silk in biomedical issues

Spider silk, as one of the hardest natural and biocompatible substances with extraordinary strength and flexibility, have become an ideal option in various areas of science and have made their path onto the biomedical industry. Despite its growing popularity, the difficulties in the extraction of silks from spiders and farming them have made it unaffordable and almost impossible for industrial scale. Biotechnology helped production of spider silks recombinantly in different hosts and obtaining diverse morphologies out of them based on different processing and assembly procedures. Herein, the characteristics of these morphologies and their advantages and disadvantages are summarized. A detailed view about applications of recombinant silks in skin regeneration and cartilage, tendon, bone, teeth, cardiovascular, and neural tissues engineering are brought out, where there is a need for strong scaffolds to support cell growth. Likewise, spider silk proteins have applications as conduit constructs, medical sutures, and 3D printer bioinks. Other characteristics of spider silks, such as low immunogenicity, hydrophobicity, homogeneity, and adjustability, have attracted much attention in drug and gene delivery. Finally, the challenges and obstacles ahead for industrializing the production of spider silk proteins in sufficient quantities in biomedicine, along with solutions to overcome these barriers, are discussed.

Conductive Polymeric-Based Electroactive Scaffolds for Tissue Engineering Applications: Current Progress and Challenges from Biomaterials and Manufacturing Perspectives

The practice of combining external stimulation therapy alongside stimuli-responsive bio-scaffolds has shown massive potential for tissue engineering applications. One promising example is the combination of electrical stimulation (ES) and electroactive scaffolds because ES could enhance cell adhesion and proliferation as well as modulating cellular specialization. Even though electroactive scaffolds have the potential to revolutionize the field of tissue engineering due to their ability to distribute ES directly to the target tissues, the development of effective electroactive scaffolds with specific properties remains a major issue in their practical uses. Conductive polymers (CPs) offer ease of modification that allows for tailoring the scaffold's various properties, making them an attractive option for conductive component in electroactive scaffolds. This review provides an up-to-date narrative of the progress of CPs-based electroactive scaffolds and the challenge of their use in various tissue engineering applications from biomaterials perspectives. The general issues with CP-based scaffolds relevant to its application as electroactive scaffolds were discussed, followed by a more specific discussion in their applications for specific tissues, including bone, nerve, skin, skeletal muscle and cardiac muscle scaffolds. Furthermore, this review also highlighted the importance of the manufacturing process relative to the scaffold's performance, with particular emphasis on additive manufacturing, and various strategies to overcome the CPs' limitations in the development of electroactive scaffolds.

Use of electroconductive biomaterials for engineering tissues by 3D printing and 3D bioprinting

Existing methods of engineering alternatives to restore or replace damaged or lost tissues are not satisfactory due to the lack of suitable constructs that can fit precisely, function properly and integrate into host tissues. Recently, three-dimensional (3D) bioprinting approaches have been developed to enable the fabrication of pre-programmed synthetic tissue constructs that have precise geometries and controlled cellular composition and spatial distribution. New bioinks with electroconductive properties have the potential to influence cellular fates and function for directed healing of different tissue types including bone, heart and nervous tissue with the possibility of improved outcomes. In the present paper, we review the use of electroconductive biomaterials for the engineering of tissues via 3D printing and 3D bioprinting. Despite significant advances, there remain challenges to effective tissue replacement and we address these challenges and describe new approaches to advanced tissue engineering.

Conducting polymers: a comprehensive review on recent advances in synthesis, properties and applications

Conducting polymers are extensively studied due to their outstanding properties, including tunable electrical property, optical and high mechanical properties, easy synthesis and effortless fabrication and high environmental stability over conventional inorganic materials. Although conducting polymers have a lot of limitations in their pristine form, hybridization with other materials overcomes these limitations. The synergetic effects of conducting polymer composites give them wide applications in electrical, electronics and optoelectronic fields. An in-depth analysis of composites of conducting polymers with carbonaceous materials, metal oxides, transition metals and transition metal dichalcogenides etc. is used to study them effectively. Here in this review we seek to describe the transport models which help to explain the conduction mechanism, relevant synthesis approaches, and physical properties, including electrical, optical and mechanical properties. Recent developments in their applications in the fields of energy storage, photocatalysis, anti-corrosion coatings, biomedical applications and sensing applications are also explained. Structural properties play an important role in the performance of the composites.

A bioprinted composite hydrogel with controlled shear stress on cells

In recent decades, three dimensional (3D) bio-printing technology has found widespread use in tissue engineering applications. The aim of this study is to scrutinize different parameters of the bioprinter - with the help of simulation software - to print a hydrogel so much so that avoid high amounts of shear stress which is detrimental for cell viability and cell proliferation. Rheology analysis was done on several hydrogels composed of different percentages of components: alginate, collagen, and gelatin. The results have led to the combination of percentages collagen:alginate:gelatin (1:4:8)% as the best condition which makes sol-gel transition at room temperature possible. The results have shown the highest diffusion rate and cell viability for the cross-linked sample with 1.5% CaCl₂ for the duration of 1 h. Finally, we have succeeded in printing the hydrogel that is mechanically strong with suitable degradation rate and cell viability.