Highly porous scaffolds of PEDOT:PSS for bone tissue engineering

Electroconductive gelatin/hyaluronic acid/hydroxyapatite scaffolds for enhanced cell proliferation and osteogenic differentiation in bone tissue engineering

Addressing the challenge of bone tissue regeneration requires creating an optimal microenvironment that promotes both osteogenesis and angiogenesis. Electroconductive scaffolds have emerged as promising solutions for bone regeneration; however, existing conductive polymers often lack biofunctionality and biocompatibility. In this study, we synthesized poly(3,4-ethylenedioxythiophene) nanoparticles (PEDOT NPs) using chemical oxidation polymerization and incorporated them into gelatin/hyaluronic acid/hydroxyapatite (Gel:HA:HAp) scaffolds to develop Gel:HA:HAp:PEDOT-NP scaffolds. Morphological analysis by scanning electron microscopy (SEM) showed a honeycomb-like structure with pores of 228-250 μm in diameter. The addition of the synthesized PEDOT NPs increased the conductive capabilities of the scaffolds to 1 × 10-6 ± 1.3 × 10-7 S/cm. Biological assessment of PEDOT NP scaffolds using human foetal osteoblastic 1.19 cells (hFOB), and human bone marrow-derived mesenchymal stem cells (hBMSCs) revealed enhanced cell proliferation and viability compared to control scaffold without NPs, along with increased osteogenic differentiation, evidenced by higher levels of alkaline phosphatase activity, osteopontin (OPN), alkaline phosphatase (ALP), and osteocalcin (OCN) expression, as observed through immunofluorescence, and enhanced expression of osteogenic-related genes. The conductive scaffold shows interesting mineralization capacity, as shown by Alizarin red and Osteoimage staining. Furthermore, PEDOT-NP scaffolds promoted angiogenesis, as indicated by improved tube formation abilities of human umbilical vein endothelial cells (HUVECs), especially at the higher concentrations of NPs. Overall, our findings demonstrate that the integration of PEDOT NPs scaffold enhances their conductive properties and promotes cell proliferation, osteogenic differentiation, and angiogenesis. Gel:HA:HAp:PEDOT-NP scaffolds exhibit promising potential as efficient biomaterials for bone tissue regeneration, offering a potential engineered platform for clinical applications.

Freeze-Dried Porous Collagen Scaffolds for the Repair of Volumetric Muscle Loss Injuries

Volumetric muscle loss (VML) injuries are characterized by the traumatic loss of skeletal muscle, resulting in permanent damage to both tissue architecture and electrical excitability. To address this challenge, we previously developed a three-dimensional (3D) aligned collagen-glycosaminoglycan (CG) scaffold platform that supported in vitro myotube alignment and maturation. In this work, we assessed the ability of CG scaffolds to facilitate functional muscle recovery in a rat tibialis anterior (TA) model of VML. Functional muscle recovery was assessed following implantation of either nonconductive CG or electrically conductive CG-polypyrrole (PPy) scaffolds at 4, 8, and 12 weeks postinjury by in vivo electrical stimulation of the peroneal nerve. After 12 weeks, scaffold-treated muscles produced maximum isometric torque that was significantly greater than nontreated tissues. Histological analysis further supported these reparative outcomes with evidence of regenerating muscle fibers at the material-tissue interface in scaffold-treated tissues that were not observed in nonrepaired muscles. Scaffold-treated muscles possessed higher numbers of M1 and M2 macrophages at the injury, while conductive CG-PPy scaffold-treated muscles showed significantly higher levels of neovascularization as indicated by the presence of pericytes and endothelial cells, suggesting a persistent wound repair response not observed in nontreated tissues. Finally, only tissues treated with nonconductive CG scaffolds displayed neurofilament staining similar to native muscle, further corroborating isometric contraction data. Together, these findings show that both conductive and nonconductive CG scaffolds can facilitate improved skeletal muscle function and endogenous cellular repair, highlighting their potential use as therapeutics for VML injuries.

Application and progress of 3D printed biomaterials in osteoporosis

Osteoporosis results from a disruption in skeletal homeostasis caused by an imbalance between bone resorption and bone formation. Conventional treatments, such as pharmaceutical drugs and hormone replacement therapy, often yield suboptimal results and are frequently associated with side effects. Recently, biomaterial-based approaches have gained attention as promising alternatives for managing osteoporosis. This review summarizes the current advancements in 3D-printed biomaterials designed for osteoporosis treatment. The benefits of biomaterial-based approaches compared to traditional systemic drug therapies are discussed. These 3D-printed materials can be broadly categorized based on their functionalities, including promoting osteogenesis, reducing inflammation, exhibiting antioxidant properties, and inhibiting osteoclast activity. 3D printing has the advantages of speed, precision, personalization, etc. It is able to satisfy the requirements of irregular geometry, differentiated composition, and multilayered structure of articular osteochondral scaffolds with boundary layer structure. The limitations of existing biomaterials are critically analyzed and future directions for biomaterial-based therapies are considered.

Fast Autograft Generation Using Transferable 3D Keratinocyte Cell Sheet on PEDOT:PSS Composite PDMS Membrane for Enhancing Wound Healing

The application of cell sheet technology for wound healing preserves dense cell tissue and the natural extracellular matrix (ECM), contributing to disease prevention. Despite the effectiveness of autologous and allograft cell sheets for wound healing, conventional cell sheets, although stable, may experience necrosis in their middle layers due to a lack of nutrients or oxygen. To address these issues, a novel approach is proposed to create cell sheets using mechanical and electrical stimulation. This method not only facilitates the transfer of cell sheets but also enhances cell bioactivity. The performance of the proposed membrane, with a mechanically controlled microstructure under electrical stimulation, is validated in both in vitro and in vivo models. The micro-structured membrane allows for diverse electrical stimulation compared to flat membranes, which accelerates the detachment of cell sheets and promotes angiogenesis and re-epithelialization. These findings indicate that the innovative cell sheet technology could significantly enhance rapid wound healing in regenerative medicine.

Primary cilia as antennas for oxygen

Over the past few decades, the primary cilium, an inconspicuous cell organelle, has increasingly become the focus of current research. The primary cilium is a microtubule-based, nonmotile, antenna-like structure that is present in almost all mammalian cells. The ciliary membrane incorporates a large number of receptor molecules, which further characterize this cellular organelle. These include receptors of the Sonic hedgehog (Shh)-, Wnt-, or platelet-derived growth factor (PDGF) signaling pathways. For this reason, as well as due to the fact that extracellular signaling molecules can bind to the ciliary membrane, primary cilia have been named "the antenna of the cell." In addition to their signaling function, the association of ciliary dysfunctions with a variety of diseases, so-called ciliopathies, underscores the importance of this functional cellular structure. Recent studies have also implicated primary cilia in the adaptation to low-oxygen conditions, which are characteristic of ischemia, such as in stroke or myocardial infarction, or tumor entities. The aim of this review is to provide an overview of these multiple facets and to take a closer look at the evolution of an inconspicuous cell organelle to a major player in hypoxia.

From innovation to clinic: Emerging strategies harnessing electrically conductive polymers to enhance electrically stimulated peripheral nerve repair

Peripheral nerve repair (PNR) is a major healthcare challenge due to the limited regenerative capacity of the nervous system, often leading to severe functional impairments. While nerve autografts are the gold standard, their implications are constrained by issues such as donor site morbidity and limited availability, necessitating innovative alternatives like nerve guidance conduits (NGCs). However, the inherently slow nerve growth rate (∼1 mm/day) and prolonged neuroinflammation, delay recovery even with the use of passive (no-conductive) NGCs, resulting in muscle atrophy and loss of locomotor function. Electrical stimulation (ES) has the ability to enhance nerve regeneration rate by modulating the innate bioelectrical microenvironment of nerve tissue while simultaneously fostering a reparative environment through immunoregulation. In this context, electrically conductive polymer (ECP)-based biomaterials offer unique advantages for nerve repair combining their flexibility, akin to traditional plastics, and mixed ionic-electronic conductivity, similar to ionically conductive nerve tissue, as well as their biocompatibility and ease of fabrication. This review focuses on the progress, challenges, and emerging techniques for integrating ECP based NGCs with ES for functional nerve regeneration. It critically evaluates the various approaches using ECP based scaffolds, identifying gaps that have hindered clinical translation. Key challenges discussed include designing effective 3D NGCs with high electroactivity, optimizing ES modules, and better understanding of immunoregulation during nerve repair. The review also explores innovative strategies in material development and wireless, self-powered ES methods. Furthermore, it emphasizes the need for non-invasive ES delivery methods combined with hybrid ECP based neural scaffolds, highlighting future directions for advancing preclinical and clinical translation. Together, ECP based NGCs combined with ES represent a promising avenue for advancing PNR and improving patient outcomes.

Engineering the interfaces of 3D-printed polylactic acid scaffolds with bioactive molecules for bone tissue engineering

3D-printed tissue engineering scaffolds have emerged as a substitute to overcome the challenges faced in the reconstruction of bone. The prime objective of the study is to explore the feasibility of plasma-coated 3D-printed PLA scaffolds for bone tissue engineering. By engineering interfaces of these scaffolds with functional molecules, the surface properties can be controlled to ensure better interactions with the cells. To pursue this goal, the surface of these scaffolds was initially coated with polyoxazoline and then functionalized using L-Tryptophan. Hierarchical porous structures composed of meticulously ordered and well-connected pores were evident from the morphological analysis. The surface chemical characterisation revealed successful immobilisation of L-tryptophan on coated samples. The wettability of these scaffolds was favourable for cell adhesion and migration. They exhibited good mechanical properties, cytocompatibility and promoted the proliferation of osteosarcoma bone cells (MG-63). These results show the potential of bio-interface engineering in tailoring the surface properties of scaffolds in bone tissue engineering.

Cell-free biodegradable electroactive scaffold for urinary bladder tissue regeneration

Tissue engineering heavily relies on cell-seeded scaffolds to support the complex biological and mechanical requirements of a target organ. However, in addition to safety and efficacy, translation of tissue engineering technology will depend on manufacturability, affordability, and ease of adoption. Therefore, there is a need to develop scalable biomaterial scaffolds with sufficient bioactivity to eliminate the need for exogenous cell seeding. Herein, we describe implementation of an electroactive biodegradable elastomer for urinary bladder tissue engineering. To create an electrically conductive and mechanically robust scaffold to support bladder tissue regeneration, we develop a functionalization method wherein the hydrophobic conductive polymer poly(3,4-ethylenedioxythiophene) (PEDOT) is polymerized in situ within a similarly hydrophobic citrate-based elastomer poly(octamethylene-citrate-co-octanol) (POCO) film. We demonstrate the efficacy of this scaffold for bladder augmentation in primarily female athymic rats, comparing PEDOT-POCO scaffolds to mesenchymal stromal cell-seeded POCO scaffolds. PEDOT-POCO recovers bladder function and anatomical structure comparably to the cell-seeded POCO scaffolds and significantly better than non-cell-seeded POCO scaffolds. This manuscript reports a functionalization method that confers electroactivity to a biodegradable elastic scaffold, facilitating the successful restoration of anatomical and physiological function of an organ.

Bone metabolism associated with annual antler regeneration: a deer insight into osteoporosis reversal

Osteoporosis, a metabolic disorder, remains challenging to treat due to limited understanding of its underlying mechanism. The annual cycle of "cyclic physiological osteoporosis (CPO)" and its full reversal in male deer represents a unique natural model for studying this condition. Deer antlers, weighing up to 25 kg/pair, derive over 60% of their mineral contents from deer skeleton during mineralization. Based on the literature, we propose to divide CPO and its reversal into two phases: Phase I (approximately 115 days): from hard antler casting to the end of antler linear growth, marked by simultaneous robust antler ossification and CPO development; and Phase II (up to 165 days): from end of Phase I to the onset of antler skin shedding, characterized by complete antler mineralization and CPO reversal. This review analyzes the paradoxical occurrence of robust antler ossification and skeleton CPO within the same endocrine microenvironment during phase I; total antler mineralization and full reversal of deer skeleton CPO in phase II. Furthermore, we will discuss potential insights for osteoporosis treatment using deer materials from the period of Phase II. Our goal is to identify novel substances and therapies that could be applied in clinical setting to effectively treat osteoporosis.

Materials for 3D printing in healthcare sector: A review

Additive Manufacturing (AM) encompasses various techniques creating intricate components from digital models. The aim of incorporating 3D printing (3DP) in the healthcare sector is to transform patient care by providing personalized solutions, improving medical procedures, fostering research and development, and ultimately optimizing the efficiency and effectiveness of healthcare delivery. This review delves into the historical beginnings of AM's 9 integration into medical contexts exploring various categories of AM methodologies and their roles within the medical sector. This survey also dives into the issue of material requirements and challenges specific to AM's medical applications. Emphasis is placed on how AM processes directly enhance human well-being. The primary focus of this paper is to highlight the evolution and incentives for cross-disciplinary AM applications, particularly in the realm of healthcare by considering their principle, materials and applications. It is designed for a diverse audience, including manufacturing professionals and researchers, seeking insights into this transformative technology's medical dimensions.

Conductive Microgel Annealed Scaffolds Enhance Myogenic Potential of Myoblastic Cells

Conductive biomaterials may capture native or exogenous bioelectric signaling, but incorporation of conductive moieties is limited by cytotoxicity, poor injectability, or insufficient stimulation. Microgel annealed scaffolds are promising as hydrogel-based materials due to their inherent void space that facilitates cell migration and proliferation better than nanoporous bulk hydrogels. Conductive microgels are generated from poly(ethylene) glycol (PEG and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT: PSS) to explore the interplay of void volume and conductivity on myogenic differentiation. PEDOT: PSS increases microgel conductivity two-fold while maintaining stiffness, annealing strength, and viability of associated myoblastic cells. C2C12 myoblasts exhibit increases in the late-stage differentiation marker myosin heavy chain as a function of both porosity and conductivity. Myogenin, an earlier marker, is influenced only by porosity. Human skeletal muscle-derived cells exhibit increased Myod1, insulin like growth factor-1, and insulin-like growth factor binding protein 2 at earlier time points on conductive microgel scaffolds compared to non-conductive scaffolds. They also secrete more vascular endothelial growth factor at early time points and express factors that led to macrophage polarization patterns observe during muscle repair. These data indicate that conductivity aids myogenic differentiation of myogenic cell lines and primary cells, motivating the need for future translational studies to promote muscle repair.

Freeze-dried porous collagen scaffolds for the repair of volumetric muscle loss injuries

Volumetric muscle loss (VML) injuries are characterized by the traumatic loss of skeletal muscle resulting in permanent damage to both tissue architecture and electrical excitability. To address this challenge, we previously developed a 3D aligned collagen-glycosaminoglycan (CG) scaffold platform that supported in vitro myotube alignment and maturation. In this work, we assessed the ability of CG scaffolds to facilitate functional muscle recovery in a rat tibialis anterior (TA) model of VML. Functional muscle recovery was assessed following implantation of either non-conductive CG or electrically conductive CG-polypyrrole (PPy) scaffolds at 4, 8, and 12 weeks post-injury by in vivo electrical stimulation of the peroneal nerve. After 12 weeks, scaffold-treated muscles produced maximum isometric torque that was significantly greater than non-treated tissues. Histological analysis further supported these reparative outcomes with evidence of regenerating muscle fibers at the material-tissue interface in scaffold-treated tissues that was not observed in non-repaired muscles. Scaffold-treated muscles possessed higher numbers of M1 and M2 macrophages at the injury while conductive CG-PPy scaffold-treated muscles showed significantly higher levels of neovascularization as indicated by the presence of pericytes and endothelial cells, suggesting a persistent wound repair response not observed in non-treated tissues. Finally, only tissues treated with non-conductive CG scaffolds displayed neurofilament staining similar to native muscle, further corroborating isometric contraction data. Together, these findings show that CG scaffolds can facilitate improved skeletal muscle function and endogenous cellular repair, highlighting their potential use as therapeutics for VML injuries.

Emerging 2D Nanomaterials-Integrated Hydrogels: Advancements in Designing Theragenerative Materials for Bone Regeneration and Disease Therapy

This review highlights recent advancements in the synthesis, processing, properties, and applications of 2D-material integrated hydrogels, with a focus on their performance in bone-related applications. Various synthesis methods and types of 2D nanomaterials, including graphene, graphene oxide, transition metal dichalcogenides, black phosphorus, and MXene are discussed, along with strategies for their incorporation into hydrogel matrices. These composite hydrogels exhibit tunable mechanical properties, high surface area, strong near-infrared (NIR) photon absorption and controlled release capabilities, making them suitable for a range of regeneration and therapeutic applications. In cancer therapy, 2D-material-based hydrogels show promise for photothermal and photodynamic therapies, and drug delivery (chemotherapy). The photothermal properties of these materials enable selective tumor ablation upon NIR irradiation, while their high drug-loading capacity facilitates targeted and controlled release of chemotherapeutic agents. Additionally, 2D-materials -infused hydrogels exhibit potent antibacterial activity, making them effective against multidrug-resistant infections and disruption of biofilm generated on implant surface. Moreover, their synergistic therapy approach combines multiple treatment modalities such as photothermal, chemo, and immunotherapy to enhance therapeutic outcomes. In bio-imaging, these materials serve as versatile contrast agents and imaging probes, enabling their real-time monitoring during tumor imaging. Furthermore, in bone regeneration, most 2D-materials incorporated hydrogels promote osteogenesis and tissue regeneration, offering potential solutions for bone defects repair. Overall, the integration of 2D materials into hydrogels presents a promising platform for developing multifunctional theragenerative biomaterials.

Straightforward Production Methods for Diverse Porous PEDOT:PSS Structures and Their Characterization

Porous conductive polymer structures, in particular Poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) structures, are gaining in importance due to their versatile fields of application as sensors, hydrogels, or supercapacitors, to name just a few. Moreover, (porous) conducting polymers have become of interest for wearable and smart textile applications due to their biocompatibility, which enables applications with direct skin contact. Therefore, there is a huge need to investigate distinct, straightforward, and textile-compatible production methods for the fabrication of porous PEDOT:PSS structures. Here, we present novel and uncomplicated approaches to producing diverse porous PEDOT:PSS structures and characterize them thoroughly in terms of porosity, electrical resistance, and their overall appearance. Production methods comprise the incorporation of micro cellulose, the usage of a blowing agent, creating a sponge-like structure, and spraying onto a porous base substrate. This results in the fabrication of various porous structures, ranging from thin and slightly porous to thick and highly porous. Depending on the application, these structures can be modified and integrated into electronic components or wearables to serve as porous electrodes, sensors, or other functional devices.

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.

An injectable polyacrylamide/chitosan-based hydrogel with highly adhesive, stretchable and electroconductive properties loaded with irbesartan for treatment of myocardial ischemia-reperfusion injury

Myocardial ischemia-reperfusion injury (MIRI) significantly contributes to the high incidence of complications and mortality associated with acute myocardial infarction. Recently, injectable electroconductive hydrogels (IECHs) have emerged as promising tools for replicating the mechanical, electroconductive, and physiological characteristics of cardiac tissue. Herein, we aimed to develop a novel IECH by incorporating irbesartan as a drug delivery system (DDS) for cardiac repair. Our approach involved merging a conductive poly-thiophene derivative (PEDOT: PSS) with an injectable dual-network adhesive hydrogel (DNAH) comprising a catechol-branched polyacrylamide network and a chitosan-hyaluronic acid covalent network. The resulting P-DNAH hydrogel, benefitting from a high conducting polymer content, a chemically crosslinked network, a robust dissipative matrix, and dynamic oxidation of catechol to quinone exhibited superior mechanical strength, desirable conductivity, and robust wet-adhesiveness. In vitro experiments with the P-DNAH hydrogel carrying irbesartan (P-DNAH-I) demonstrated excellent biocompatibility by cck-8 kit on H9C2 cells and a rapid initial release of irbesartan. Upon injection into the infarcted hearts of MIRI mouse models, the P-DNAH-I hydrogel effectively inhibited the inflammatory response and reduced the infarct size. In conclusion, our results suggest that the P-DNAH hydrogel, possessing suitable mechanical properties and electroconductivity, serves as an ideal IECH for DDS, delivering irbesartan to promote heart repair.

S100b treatment overcomes RAGE signaling deficits in myoblasts on advanced glycation end-product cross-linked collagen and promotes myogenic differentiation

Advanced glycation end-products (AGEs) stochastically accrue in skeletal muscle and on collagen over an individual's lifespan, stiffening the muscle and modifying the stem cell (MuSC) microenvironment while promoting proinflammatory, antiregenerative signaling via the receptor for advanced glycation end-products (RAGEs). In the present study, a novel in vitro model was developed of this phenomenon by cross linking a 3-D collagen scaffold with AGEs and investigating how myoblasts responded to such an environment. Briefly, collagen scaffolds were incubated with d-ribose (0, 25, 40, 100, or 250 mM) for 5 days at 37°C. C2C12 immortalized mouse myoblasts were grown on the scaffolds for 6 days in growth conditions for proliferation, and 12 days for differentiation and fusion. Human primary myoblasts were also used to confirm the C2C12 data. AGEs aberrantly extended the DNA production stage of C2C12s (but not in human primary myoblasts) which is known to delay differentiation in myogenesis, and this effect was prevented by RAGE inhibition. Furthermore, the differentiation and fusion of myoblasts were disrupted by AGEs, which were associated with reductions in integrins and suppression of RAGE. The addition of S100b (RAGE agonist) recovered the differentiation and fusion of myoblasts, and the addition of RAGE inhibitors (FPS-ZM1 and Azeliragon) inhibited the differentiation and fusion of myoblasts. Our results provide novel insights into the role of the AGE-RAGE axis in skeletal muscle aging, and future work is warranted on the potential application of S100b as a proregenerative factor in aged skeletal muscle.NEW & NOTEWORTHY Collagen cross-linked by advanced glycation end-products (AGEs) induced myoblast proliferation but prevented differentiation, myotube formation, and RAGE upregulation. RAGE inhibition occluded AGE-induced myoblast proliferation, while the delivery of S100b, a RAGE ligand, recovered fusion deficits.

Synergy between 3D-extruded electroconductive scaffolds and electrical stimulation to improve bone tissue engineering strategies

In this work, we propose a simple, reliable, and versatile strategy to create 3D electroconductive scaffolds suitable for bone tissue engineering (TE) applications with electrical stimulation (ES). The proposed scaffolds are made of 3D-extruded poly(ε-caprolactone) (PCL), subjected to alkaline treatment, and of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS), anchored to PCL with one of two different crosslinkers: (3-glycidyloxypropyl)trimethoxysilane (GOPS) and divinyl sulfone (DVS). Both cross-linkers allowed the formation of a homogenous and continuous coating of PEDOT:PSS to PCL. We show that these PEDOT:PSS coatings are electroconductive (11.3-20.1 S cm-1), stable (up to 21 days in saline solution), and allow the immobilization of gelatin (Gel) to further improve bioactivity. In vitro mineralization of the corresponding 3D conductive scaffolds was greatly enhanced (GOPS(NaOH)-Gel - 3.1 fold, DVS(NaOH)-Gel - 2.0 fold) and cell colonization and proliferation were the highest for the DVS(NaOH)-Gel scaffold. In silico modelling of ES application in DVS(NaOH)-Gel scaffolds indicates that the electrical field distribution is homogeneous, which reduces the probability of formation of faradaic products. Osteogenic differentiation of human bone marrow derived mesenchymal stem/stromal cells (hBM-MSCs) was performed under ES. Importantly, our results clearly demonstrated a synergistic effect of scaffold electroconductivity and ES on the enhancement of MSC osteogenic differentiation, particularly on cell-secreted calcium deposition and the upregulation of osteogenic gene markers such as COL I, OC and CACNA1C. These scaffolds hold promise for future clinical applications, including manufacturing of personalized bone TE grafts for transplantation with enhanced maturation/functionality or bioelectronic devices.

Bioactive Conjugated Polymer-Based Biodegradable 3D Bionic Scaffolds for Facilitating Bone Defect Repair

Bone defect regeneration is one of the great clinical challenges. Suitable bioactive composite scaffolds with high biocompatibility, robust new-bone formation capability and degradability are still required. This work designs and synthesizes an unprecedented bioactive conjugated polymer PT-C3 -NH2 , demonstrating low cytotoxicity, cell proliferation/migration-promoting effect, as well as inducing cell differentiation, namely regulating angiogenesis and osteogenesis to MC3T3-E1 cells. PT-C3 -NH2 is incorporated into polylactic acid-glycolic acid (PLGA) scaffolds, which is decorated with caffeic acid (CA)-modified gelatin (Gel), aiming to improve the surface water-wettability of PLGA and also facilitate to the linkage of conjugated polymer through catechol chemistry. A 3D composite scaffold PLGA@GC-PT is then generated. This scaffold demonstrates excellent bionic structures with pore size of 50-300 µm and feasible biodegradation ability. Moreover, it also exhibites robust osteogenic effect to promote osteoblast proliferation and differentiation in vitro, thus enabling the rapid regeneration of bone defects in vivo. Overall, this study provides a new bioactive factor and feasible fabrication approach of biomimetic scaffold for bone regeneration.

Dynamics of Nanocomposite Hydrogel Alignment during 3D Printing to Develop Tissue Engineering Technology

Taking inspiration from spider silk protein spinning, we developed a method to produce tough filaments using extrusion-based 3D bioprinting and salting-out of the protein. To enhance both stiffness and ductility, we have designed a blend of partially crystalline, thermally sensitive natural polymer gelatin and viscoelastic G-polymer networks, mimicking the components of spider silk. Additionally, we have incorporated inorganic nanoparticles as a rheological modifier to fine-tune the 3D printing properties. This self-healing nanocomposite hydrogel exhibits exceptional mechanical properties, biocompatibility, shear thinning behavior, and a well-controlled gelation mechanism for 3D printing.

Electroactive 4D Porous Scaffold Based on Conducting Polymer as a Responsive and Dynamic In Vitro Cell Culture Platform

In vivo, cells reside in a 3D porous and dynamic microenvironment. It provides biochemical and biophysical cues that regulate cell behavior in physiological and pathological processes. In the context of fundamental cell biology research, tissue engineering, and cell-based drug screening systems, a challenge is to develop relevant in vitro models that could integrate the dynamic properties of the cell microenvironment. Taking advantage of the promising high internal phase emulsion templating, we here designed a polyHIPE scaffold with a wide interconnected porosity and functionalized its internal 3D surface with a thin layer of electroactive conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) to turn it into a 4D electroresponsive scaffold. The resulting scaffold was cytocompatible with fibroblasts, supported cellular infiltration, and hosted cells, which display a 3D spreading morphology. It demonstrated robust actuation in ion- and protein-rich complex culture media, and its electroresponsiveness was not altered by fibroblast colonization. Thanks to customized electrochemical stimulation setups, the electromechanical response of the polyHIPE/PEDOT scaffolds was characterized in situ under a confocal microscope and showed 10% reversible volume variations. Finally, the setups were used to monitor in real time and in situ fibroblasts cultured into the polyHIPE/PEDOT scaffold during several cycles of electromechanical stimuli. Thus, we demonstrated the proof of concept of this tunable scaffold as a tool for future 4D cell culture and mechanobiology studies.

Integrated evaluation of biomechanical and biological properties of the biomimetic structural bone scaffold: Biomechanics, simulation analysis, and osteogenesis

A porous structure is essential for bone implants because it increases the bone ingrowth space and improves mechanical and biological properties. The biomimetically designed porous Voronoi scaffold can reconstruct the structure and function of cancellous bone; however, its comprehensive properties need to be investigated further. In this study, algorithms based on scaling factors were used to design the Voronoi scaffolds. Classic approaches, such as computer-aided design and the implicit surface method, have been used to design Diamond, Gyroid, and I-WP scaffolds as controls. All scaffolds were prepared by selective laser melting of titanium alloys and three-dimensional printing. Mechanical tests, finite element analysis, and in vitro and in vivo experiments were performed to investigate the biomechanical, cytologic, and osteogenic performance of the scaffolds, while computational fluid dynamics simulations were used to explore the underlying mechanisms. Diamond scaffolds have a better loading capacity, and the mechanical behaviors and fluid flow of Voronoi scaffolds are similar to those of the human trabecular bone. Cells showed more proliferation and distribution on the Diamond and Voronoi scaffolds and exhibited evident differentiation on Gyroid and Voronoi scaffolds. Bone formation was apparent on the inner part of the Gyroid, the outer part of the I-WP, and the entire Diamond and Voronoi scaffolds. The hydrodynamic properties and stimulus response of cells influenced by the porous structure account for the varied biological performance of the scaffolds. The Voronoi scaffolds with bionic mechanical behavior and an appropriate hydrodynamic response exhibit evident cell growth and osteogenesis, making them preferable for porous structural bone implants.

The effect of graphene and graphene oxide induced reactive oxygen species on polycaprolactone scaffolds for bone cancer applications

Bone cancer remains a critical healthcare problem. Among current clinical treatments, tumour resection is the most common strategy. It is usually effective but may present several limitations such as multiple operations, long hospital time, and the potential recurrence caused by the incomplete removal of cancer cells. To address these limitations, three-dimensional (3D) scaffolds fabricated through additive manufacturing have been researched for both bone cancer treatment and post-treatment rehabilitation. Polycaprolactone (PCL)-based scaffolds play an important role in bone regeneration, serving as a physical substrate to fill the defect site, recruiting cells, and promoting cell proliferation and differentiation, ultimately leading to the regeneration of the bone tissue without multiple surgical applications. Multiple advanced materials have been incorporated during the fabrication process to improve certain functions and/or modulate biological performances. Graphene-based nanomaterials, particularly graphene (G) and graphene oxide (GO), have been investigated both in vitro and in vivo, significantly improving the scaffold's physical, chemical, and biological properties, which strongly depend on the material type and concentration. A unique targeted inhibition effect on cancer cells was also discovered. However, limited research has been conducted on utilising graphene-based nanomaterials for both bone regeneration and bone cancer treatment, and there is no systematic study into the material- and dose-dependent effects, as well as the working mechanism on 3D scaffolds to realise these functions. This paper addresses these limitations by designing and fabricating PCL-based scaffolds containing different concentrations of G and GO and assessing their biological behaviour correlating it to the reactive oxygen species (ROS) release level. Results suggest that the ROS release from the scaffolds is a dominant mechanism that affects the biological behaviour of the scaffolds. ROS release also contributes to the inhibition effect on bone cancer due to healthy cells and cancer cells responding differently to ROS, and the osteogenesis results also present a certain correlation with ROS. These observations revealed a new route for realising bone cancer treatment and subsequent new bone regeneration, using a single dual-functional 3D scaffold.

Cell-free biodegradable electroactive scaffold for urinary bladder regeneration

Tissue engineering heavily relies on cell-seeded scaffolds to support the complex biological and mechanical requirements of a target organ. However, in addition to safety and efficacy, translation of tissue engineering technology will depend on manufacturability, affordability, and ease of adoption. Therefore, there is a need to develop scalable biomaterial scaffolds with sufficient bioactivity to eliminate the need for exogenous cell seeding. Herein, we describe synthesis, characterization, and implementation of an electroactive biodegradable elastomer for urinary bladder tissue engineering. To create an electrically conductive and mechanically robust scaffold to support bladder tissue regeneration, we developed a phase-compatible functionalization method wherein the hydrophobic conductive polymer poly(3,4-ethylenedioxythiophene) (PEDOT) was polymerized in situ within a similarly hydrophobic citrate-based elastomer poly(octamethylene-citrate-co-octanol) (POCO) film. We demonstrate the efficacy of this film as a scaffold for bladder augmentation in athymic rats, comparing PEDOT-POCO scaffolds to mesenchymal stromal cell-seeded POCO scaffolds. PEDOT-POCO recovered bladder function and anatomical structure comparably to the cell-seeded POCO scaffolds and significantly better than non-cell seeded POCO scaffolds. This manuscript reports: (1) a new phase-compatible functionalization method that confers electroactivity to a biodegradable elastic scaffold, and (2) the successful restoration of the anatomy and function of an organ using a cell-free electroactive scaffold.

eSoil: A low-power bioelectronic growth scaffold that enhances crop seedling growth

Active hydroponic substrates that stimulate on demand the plant growth have not been demonstrated so far. Here, we developed the eSoil, a low-power bioelectronic growth scaffold that can provide electrical stimulation to the plants' root system and growth environment in hydroponics settings. eSoil's active material is an organic mixed ionic electronic conductor while its main structural component is cellulose, the most abundant biopolymer. We demonstrate that barley seedlings that are widely used for fodder grow within the eSoil with the root system integrated within its porous matrix. Simply by polarizing the eSoil, seedling growth is accelerated resulting in increase of dry weight on average by 50% after 15 d of growth. The effect is evident both on root and shoot development and occurs during the growth period after the stimulation. The stimulated plants reduce and assimilate NO3- more efficiently than controls, a finding that may have implications on minimizing fertilizer use. However, more studies are required to provide a mechanistic understanding of the physical and biological processes involved. eSoil opens the pathway for the development of active hydroponic scaffolds that may increase crop yield in a sustainable manner.

Stimuli-responsive Biomaterials for Tissue Engineering Applications

The use of ''smart materials,'' or ''stimulus responsive'' materials, has proven useful in a variety of fields, including tissue engineering and medication delivery. Many factors, including temperature, pH, redox state, light, and magnetic fields, are being studied for their potential to affect a material's properties, interactions, structure, and/or dimensions. New tissue engineering and drug delivery methods are made possible by the ability of living systems to respond to both external stimuli and their own internal signals) for example, materials composed of stimuliresponsive polymers that self assemble or undergo phase transitions or morphology transformation. The researcher examines the potential of smart materials as controlled drug release vehicles in tissue engineering, aiming to enable the localized regeneration of injured tissue by delivering precisely dosed drugs at precisely timed intervals.

Combining Step-Growth and Chain-Growth Polymerizations in One Pot: Light-Induced Fabrication of Conductive Nanoporous PEDOT-PCL Scaffold

A novel method based on light-induced fabrication of a poly (3,4-ethylenedioxythiophene)-polycaprolactone (PEDOT-PCL) scaffold using phenacyl bromide (PAB) as a single-component photoinitiator is presented. HBr released from the step-growth polymerization of EDOT is utilized as an in situ catalyst for the chain-growth polymerization of ε-caprolactone. Detailed investigations disclose the formation of a self-assembled nanoporous electroconductive scaffold (1.2 mS cm-1 ). Fluorescence emission spectra of the fabricated scaffold exhibit a mixed solvatochromic behavior, indicating specific interactions between the self-assembled scaffold and solvents with varying polarities, as evidenced by transmission electron microscopy (TEM). Moreover, the same light-induced technique can also be applied for bulk photopolymerization showcasing the versatility and wide-ranging scope of the originated method. In brief, this study introduces a novel approach for light-induced polymerization reactions that is merging step-growth and chain-growth mechanisms. This innovative approach is promising to facilitate in situ polymerization of monomers possessing diverse functionalities.

Synergy of Nanotopography and Electrical Conductivity of PEDOT/PSS for Enhanced Neuronal Development

Biomaterials able to promote neuronal development and neurite outgrowth are highly desired in neural tissue engineering for the repair of damaged or disrupted neural tissue and restoring the axonal connection. For this purpose, the use of either electroactive or micro- and nanostructured materials has been separately investigated. Here, the use of a nanomodulated conductive poly(3,4-ethylendioxithiophene) poly(styrenesulfonate) (PEDOT/PSS) substrate that exhibits instructive topographical and electrical cues at the same time was investigated for the first time. In particular, thin films featuring grooves with sizes comparable with those of neuronal neurites (NanoPEDOT) were fabricated by electrochemical polymerization of PEDOT/PSS on a nanomodulated polycarbonate template. The ability of NanoPEDOT to support neuronal development and direct neurite outgrowth was demonstrated by assessing cell viability and proliferation, expression of neuronal markers, average neurite length, and direction of neuroblastoma N2A cells induced to differentiate on this novel support. In addition to the beneficial effect of the nanogrooved topography, a 30% increase was shown in the average length of neurites when differentiating cells were subjected to an electrical stimulation of a few microamperes for 6 h. The results reported here suggest a favorable effect on the neuronal development of the synergistic combination of nanotopography and electrical stimulation, supporting the use of NanoPEDOT in neural tissue engineering to promote physical and functional reconnection of impaired neural networks.

Electrochemical Detection of Dopamine Release from Living Neurons Using Graphene Oxide-Incorporated Polypyrrole/Gold Nanocluster Hybrid Nanopattern Arrays

Stem-cell-based therapeutics have shown immense potential in treating various diseases that are currently incurable. In particular, partial recovery of Parkinson's disease, which occurs due to massive loss or abnormal functionality of dopaminergic (DAnergic) neurons, through the engraftment of stem-cell-derived neurons ex vivo is reported. However, precise assessment of the functionality and maturity of DAnergic neurons is still challenging for their enhanced clinical efficacy. Here, a novel conductive cell cultivation platform, a graphene oxide (GO)-incorporated metallic polymer nanopillar array (GOMPON), that can electrochemically detect dopamine (DA) exocytosis from living DAnergic neurons, is reported. In the cell-free configuration, the linear range is 0.5-100 µm, with a limit of detection of 33.4 nm. Owing to its excellent biocompatibility, a model DAnergic neuron (SH-SY5Y cell) can be cultivated and differentiated on the platform while their DA release can be quantitatively measured in a real-time and nondestructive manner. Finally, it is showed that the functionality of the DAnergic neurons derived from stem cells can be precisely assessed via electrochemical detection of their DA exocytosis. The developed GOMPON is highly promising for a wide range of applications, including real-time monitoring of stem cell differentiation into neuronal lineages, evaluating differentiation protocols, and finding practical stem cell therapies.

Enthesis maturation in engineered ligaments is differentially driven by loads that mimic slow growth elongation and rapid cyclic muscle movement

Entheses are complex attachments that translate load between elastic-ligaments and stiff-bone via organizational and compositional gradients. Neither natural healing, repair, nor engineered replacements restore these gradients, contributing to high re-tear rates. Previously, we developed a culture system which guides ligament fibroblasts in high-density collagen gels to develop early postnatal-like entheses, however further maturation is needed. Mechanical cues, including slow growth elongation and cyclic muscle activity, are critical to enthesis development in vivo but these cues have not been widely explored in engineered entheses and their individual contribution to maturation is largely unknown. Our objective here was to investigate how slow stretch, mimicking ACL growth rates, and intermittent cyclic loading, mimicking muscle activity, individually drive enthesis maturation in our system so to shed light on the cues governing enthesis development, while further developing our tissue engineered replacements. Interestingly, we found these loads differentially drive organizational maturation, with slow stretch driving improvements in the interface/enthesis region, and cyclic load improving the ligament region. However, despite differentially affecting organization, both loads produced improvements to interface mechanics and zonal composition. This study provides insight into how mechanical cues differentially affect enthesis development, while producing some of the most organized engineered enthesis to date. STATEMENT OF SIGNIFICANCE: Entheses attach ligaments to bone and are critical to load transfer; however, entheses do not regenerate with repair or replacement, contributing to high re-tear rates. Mechanical cues are critical to enthesis development in vivo but their individual contribution to maturation is largely unknown and they have not been widely explored in engineered replacements. Here, using a novel culture system, we provide new insight into how slow stretch, mimicking ACL growth rates, and intermittent cyclic loading, mimicking muscle activity, differentially affect enthesis maturation in engineered ligament-to-bone tissues, ultimately producing some of the most organized entheses to date. This system is a promising platform to explore cues regulating enthesis formation so to produce functional engineered replacements and better drive regeneration following repair.

3D printing microporous scaffolds from modular bioinks containing sacrificial, cell-encapsulating microgels

Microgel-based biomaterials have inherent porosity and are often extrudable, making them well-suited for 3D bioprinting applications. Cells are commonly introduced into these granular inks post-printing using cell infiltration. However, due to slow cell migration speeds, this strategy struggles to achieve depth-independent cell distributions within thick 3D printed geometries. To address this, we leverage granular ink modularity by combining two microgels with distinct functions: (1) structural, UV-crosslinkable microgels made from gelatin methacryloyl (GelMA) and (2) sacrificial, cell-laden microgels made from oxidized alginate (AlgOx). We hypothesize that encapsulating cells within sacrificial AlgOx microgels would enable the simultaneous introduction of void space and release of cells at depths unachievable through cell infiltration alone. Blending the microgels in different ratios produces a family of highly printable GelMA : AlgOx microgel inks with void fractions ranging from 0.03 to 0.35. As expected, void fraction influences the morphology of human umbilical vein endothelial cells (HUVEC) within GelMA : AlgOx inks. Crucially, void fraction does not alter the ideal HUVEC distribution seen throughout the depth of 3D printed samples. This work presents a strategy for fabricating constructs with tunable porosity and depth-independent cell distribution, highlighting the promise of microgel-based inks for 3D bioprinting.

Proton Transport Across Collagen Fibrils and Scaffolds: The Role of Hydroxyproline

Collagen is one of the most studied proteins due to its fundamental role in creating fibrillar structures and supporting tissues in our bodies. Accordingly, collagen is also one of the most used proteins for making tissue-engineered scaffolds for various types of tissues. To date, the high abundance of hydroxyproline (Hyp) within collagen is commonly ascribed to the structure and stability of collagen. Here, we hypothesize a new role for the presence of Hyp within collagen, which is to support proton transport (PT) across collagen fibrils. For this purpose, we explore here three different collagen-based hydrogels: the first is prepared by the self-assembly of natural collagen fibrils, and the second and third are based on covalently linking between collagen via either a self-coupling method or with an additional cross-linker. Following the formation of the hydrogel, we introduce here a two-step reaction, involving (1) attaching methanesulfonyl to the -OH group of Hyp, followed by (2) removing the methanesulfonyl, thus reverting Hyp to proline (Pro). We explore the PT efficiency at each step of the reaction using electrical measurements and show that adding the methanesulfonyl group vastly enhances PT, while reverting Hyp to Pro significantly reduces PT efficiency (compared with the initial point) with different efficiencies for the various collagen-based hydrogels. The role of Hyp in supporting the PT can assist in our understanding of the physiological roles of collagen. Furthermore, the capacity to modulate conductivity across collagen is very important to the use of collagen in regenerative medicine.

Advancements in tailoring PEDOT: PSS properties for bioelectronic applications: A comprehensive review

In the field of bioelectronics, the demand for biocompatible, stable, and electroactive materials for functional biological interfaces, sensors, and stimulators, is drastically increasing. Conductive polymers (CPs) are synthetic materials, which are gaining increasing interest mainly due to their outstanding electrical, chemical, mechanical, and optical properties. Since its discovery in the late 1980s, the CP Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonic acid) (PEDOT:PSS) has become extremely attractive, being considered as one of the most capable organic electrode materials for several bioelectronic applications in the field of tissue engineering and regenerative medicine. Main examples refer to thin, flexible films, electrodes, hydrogels, scaffolds, and biosensors. Within this context, the authors contend that PEDOT:PSS properties should be customized to encompass: i) biocompatibility, ii) conductivity, iii) stability in wet environment, iv) adhesion to the substrate, and, when necessary, v) (bio-)degradability. However, consolidating all these properties into a single functional solution is not always straightforward. Therefore, the objective of this review paper is to present various methods for acquiring and improving PEDOT:PSS properties, with the primary focus on ensuring its biocompatibility, and simultaneously addressing the other functional features. The last section highlights a collection of designated studies, with a particular emphasis on PEDOT:PSS/carbon filler composites due to their exceptional characteristics.

Bioactive and electrically conductive GelMA-BG-MWCNT nanocomposite hydrogel bone biomaterials

Natural bone is a complex organic-inorganic composite tissue that possesses endogenous electrically conductive properties in response to mechanical forces. Mimicking these unique properties collectively in a single synthetic biomaterial has so far remained a formidable task. In this study, we report a synthesis strategy that comprised gelatin methacryloyl (GelMA), sol-gel derived tertiary bioactive glass (BG), and uniformly dispersed multiwall carbon nanotubes (MWCNTs) to create nanocomposite hydrogels that mimic the organic-inorganic composition of bone. Using this strategy, biomaterials that are electrically conductive and possess electro-mechanical properties similar to endogenous bone were prepared without affecting their biocompatibility. Nanocomposite hydrogel biomaterials were biodegradable and promoted biomineralization, and supported multipotent mesenchymal progenitor cell (10T1/2) cell interactions and differentiation into an osteogenic lineage. To the best of our knowledge, this work presents the first study to functionally characterize suitable electro-mechanical responses in nanocomposite hydrogels, a key process that occurs in the natural bone to drive its repair and regeneration. Overall, the results demonstrated GelMA-BG-MWCNT nanocomposite hydrogels have the potential to become promising bioactive biomaterials for use in bone repair and regeneration.

Accelerated Engineering of Optimized Functional Composite Hydrogels via High-Throughput Experimentation

The Materials Genome Initiative (MGI) seeks to accelerate the discovery and engineering of advanced materials via high-throughput experimentation (HTE), which is a challenging task, given the common trade-off between design for optimal processability vs performance. Here, we report a HTE method based on automated formulation, synthesis, and multiproperty characterization of bulk soft materials in well plate formats that enables accelerated engineering of functional composite hydrogels with optimized properties for processability and performance. The method facilitates rapid high-throughput screening of hydrogel composition-property relations for multiple properties in well plate formats. The feasibility and utility of the method were demonstrated by application to several functional composite hydrogel systems, including alginate/poly(N-isopropylacrylamide) (PNIPAM) and poly(ethylene glycol) dimethacrylate (PEGDMA)/poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) hydrogels. The HTE method was leveraged to identify formulations of conductive PEGDMA/PEDOT:PSS composite hydrogels for optimized performance and processability in three-dimensional (3D) printing. This work provides an advance in experimental methods based on automated dispensing, mixing, and sensing for the accelerated engineering of soft functional materials.

Human Mesenchymal Stem Cells and Innovative Scaffolds for Bone Tissue Engineering Applications

Stem cell-based therapy is a significant topic in regenerative medicine, with a predominant role being played by human mesenchymal stem cells (hMSCs). The hMSCs have been shown to be suitable in regenerative medicine for the treatment of bone tissue. In the last few years, the average lifespan of our population has gradually increased. The need of biocompatible materials, which exhibit high performances, such as efficiency in bone regeneration, has been highlighted by aging. Current studies emphasize the benefit of using biomimetic biomaterials, also known as scaffolds, for bone grafts to speed up bone repair at the fracture site. For the healing of injured bone and bone regeneration, regenerative medicine techniques utilizing a combination of these biomaterials, together with cells and bioactive substances, have drawn a great interest. Cell therapy, based on the use of hMSCs, alongside materials for the healing of damaged bone, has obtained promising results. In this work, several aspects of cell biology, tissue engineering, and biomaterials applied to bone healing/regrowth will be considered. In addition, the role of hMSCs in these fields and recent progress in clinical applications are discussed. Impact Statement The restoration of large bone defects is both a challenging clinical issue and a socioeconomic problem on a global scale. Different therapeutic approaches have been proposed for human mesenchymal stem cells (hMSCs), considering their paracrine effect and potential differentiation into osteoblasts. However, different limitations are still to be overcome in using hMSCs as a therapeutic opportunity in bone fracture repair, including hMSC administration methods. To identify a suitable hMSC delivery system, new strategies have been proposed using innovative biomaterials. This review provides an update of the literature on hMSC/scaffold clinical applications for the management of bone fractures.

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

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

3D organic bioelectronics for electrical monitoring of human adult stem cells

Three-dimensional in vitro stem cell models have enabled a fundamental understanding of cues that direct stem cell fate. While sophisticated 3D tissues can be generated, technology that can accurately monitor these complex models in a high-throughput and non-invasive manner is not well adapted. Here we show the development of 3D bioelectronic devices based on the electroactive polymer poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate)-(PEDOT:PSS) and their use for non-invasive, electrical monitoring of stem cell growth. We show that the electrical, mechanical and wetting properties as well as the pore size/architecture of 3D PEDOT:PSS scaffolds can be fine-tuned simply by changing the processing crosslinker additive. We present a comprehensive characterization of both 2D PEDOT:PSS thin films of controlled thicknesses, and 3D porous PEDOT:PSS structures made by the freeze-drying technique. By slicing the bulky scaffolds we generate homogeneous, porous 250 μm thick PEDOT:PSS slices, constituting biocompatible 3D constructs able to support stem cell cultures. These multifunctional slices are attached on indium-tin oxide substrates (ITO) with the help of an electrically active adhesion layer, enabling 3D bioelectronic devices with a characteristic and reproducible, frequency dependent impedance response. This response changes drastically when human adipose derived stem cells (hADSCs) grow within the porous PEDOT:PSS network as revealed by fluorescence microscopy. The increase of cell population within the PEDOT:PSS porous network impedes the charge flow at the interface between PEDOT:PSS and ITO, enabling the interface resistance (R1) to be used as a figure of merit to monitor the proliferation of stem cells. The non-invasive monitoring of stem cell growth allows for the subsequent differentiation 3D stem cell cultures into neuron like cells, as verified by immunofluorescence and RT-qPCR measurements. The strategy of controlling important properties of 3D PEDOT:PSS structures simply by altering processing parameters can be applied for development of a number of stem cell in vitro models as well as stem cell differentiation pathways. We believe the results presented here will advance 3D bioelectronic technology for both fundamental understanding of in vitro stem cell cultures as well as the development of personalized therapies.

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.

Biophysical Electrical and Mechanical Stimulations for Promoting Chondrogenesis of Stem Cells on PEDOT:PSS Conductive Polymer Scaffolds

The investigation of the effects of electrical and mechanical stimulations on chondrogenesis in tissue engineering scaffolds is essential for realizing successful cartilage repair and regeneration. The aim of articular cartilage tissue engineering is to enhance the function of damaged or diseased articular cartilage, which has limited regenerative capacity. Studies have shown that electrical stimulation (ES) promotes mesenchymal stem cell (MSC) chondrogenesis, while mechanical stimulation (MS) enhances the chondrogenic differentiation capacity of MSCs. Therefore, understanding the impact of these stimuli on chondrogenesis is crucial for researchers to develop more effective tissue engineering strategies for cartilage repair and regeneration. This study focuses on the preparation of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) conductive polymer (CP) scaffolds using the freeze-drying method. The scaffolds were fabricated with varying concentrations (0, 1, 3, and 10 wt %) of (3-glycidyloxypropyl) trimethoxysilane (GOPS) as a crosslinker and an additive to tailor the scaffold properties. To gain a comprehensive understanding of the material characteristics and the phase aggregation phenomenon of PEDOT:PSS scaffolds, the researchers performed theoretical calculations of solubility parameters and surface energies of PSS, PSS-GOPS, and PEDOT polymers, as well as conducted material analyses. Additionally, the study investigated the potential of promoting chondrogenic differentiation of human adipose stem cells by applying external ES or MS on a PEDOT:PSS CP scaffold. Compared to the group without stimulation, the group that underwent stimulation exhibited significantly up-regulated expression levels of chondrogenic characteristic genes, such as SOX9 and COL2A1. Moreover, the immunofluorescence staining images exhibited a more vigorous fluorescence intensity of SOX9 and COL II proteins that was consistent with the trend of the gene expression results. In the MS experiment, the strain excitation exerted on the scaffold was simulated and transformed into stress. The simulated stress response showed that the peak gradually decreased with time and approached a constant value, with the negative value of stress representing the generation of tensile stress. This stress response quantification could aid researchers in determining specific MS conditions for various materials in tissue engineering, and the applied stress conditions could be further optimized. Overall, these findings are significant contributions to future research on cartilage repair and biophysical ES/MS in tissue engineering.

Conductive microgel annealed scaffolds enhance myogenic potential of myoblastic cells

Bioelectricity is an understudied phenomenon to guide tissue homeostasis and regeneration. Conductive biomaterials may capture native or exogenous bioelectric signaling, but incorporation of conductive moieties is limited by cytotoxicity, poor injectability, or insufficient stimulation. Microgel annealed scaffolds are promising as hydrogel-based materials due to their inherent void space that facilitates cell migration and proliferation better than nanoporous bulk hydrogels. We generated conductive microgels from poly(ethylene) glycol and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) to explore the interplay of void volume and conductivity on myogenic differentiation. PEDOT:PSS increased microgel conductivity over 2-fold while maintaining stiffness, annealing strength, and viability of associated myoblastic cells. C2C12 myoblasts exhibited increases in the late-stage differentiation marker myosin heavy chain as a function of both porosity and conductivity. Myogenin, an earlier marker, was influenced only by porosity. Human skeletal muscle derived cells exhibited increased Myod1 , IGF-1, and IGFBP-2 at earlier timepoints on conductive microgel scaffolds compared to non-conductive scaffolds. They also secreted higher levels of VEGF at early timepoints and expressed factors that led to macrophage polarization patterns observed during muscle repair. These data indicate that conductivity aids myogenic differentiation of myogenic cell lines and primary cells, motivating the need for future translational studies to promote muscle repair.

Deep eutectic solvent-assisted fabrication of bioinspired 3D carbon-calcium phosphate scaffolds for bone tissue engineering

Tissue engineering is a burgeoning field focused on repairing damaged tissues through the combination of bodily cells with highly porous scaffold biomaterials, which serve as templates for tissue regeneration, thus facilitating the growth of new tissue. Carbon materials, constituting an emerging class of superior materials, are currently experiencing remarkable scientific and technological advancements. Consequently, the development of novel 3D carbon-based composite materials has become significant for biomedicine. There is an urgent need for the development of hybrids that will combine the unique bioactivity of ceramics with the performance of carbonaceous materials. Considering these requirements, herein, we propose a straightforward method of producing a 3D carbon-based scaffold that resembles the structural features of spongin, even on the nanometric level of their hierarchical organization. The modification of spongin with calcium phosphate was achieved in a deep eutectic solvent (choline chloride : urea, 1 : 2). The holistic characterization of the scaffolds confirms their remarkable structural features (i.e., porosity, connectivity), along with the biocompatibility of α-tricalcium phosphate (α-TCP), rendering them a promising candidate for stem cell-based tissue-engineering. Culturing human bone marrow mesenchymal stem cells (hMSC) on the surface of the biomimetic scaffold further verifies its growth-facilitating properties, promoting the differentiation of these cells in the osteogenesis direction. ALP activity was significantly higher in osteogenic medium compared to proliferation, indicating the differentiation of hMSC towards osteoblasts. However, no significant difference between C and C-αTCP in the same medium type was observed.

Soft Self-Assembled Mechanoelectrical Transducer Films from Conductive Microgel Waterborne Dispersions

The present study aims in the developing of new soft transducers based on sophisticated stimuli-responsive microgels that exhibit spontaneous self-assembly forming cohesive films with conductive and mechanoelectrical properties. For that, oligo(ethylene glycol)-based stimuli-responsive microgels have been synthesized using bio-inspired catechol cross-linkers by one-step batch precipitation polymerization in aqueous media. Then, 3,4-ethylene dioxyyhiophene (EDOT) has been directly polymerized onto stimuli-responsive microgels using catechol groups as the unique dopant. PEDOT location is dependent on the cross-linking density of microgel particles and EDOT amount used. Moreover, the spontaneous cohesive film formation ability of the waterborne dispersion after evaporation at soft application temperature is demonstrated. The films obtained present conductivity and enhanced mechanoelectrical properties triggered by simple finger compression. Both properties are function of the cross-linking density of the microgel seed particles and PEDOT amount incorporated. In addition, to obtain maximum electrical potential generated and the possibility to amplify it, several films in series were demonstrated to be efficient. The present material can be a potential candidate for biomedical, cosmetic, and bioelectronic applications.

Ultrasound-controlled nano oxygen carriers enhancing cell viability in 3D GelMA hydrogel for the treatment of myocardial infarction

Heart failure is a critical and ultimate phase of cardiovascular ailment that leads to a considerable incidence of disability and mortality. Among various factors contributing to heart failure, myocardial infarction is one of the most frequent and significant causes, which is still difficult to manage effectively. An innovative therapeutic strategy, namely a 3D bio-printed cardiac patch, has recently emerged as a promising approach to substitute damaged cardiomyocytes in a localized infarct region. Nevertheless, the efficacy of this treatment primarily relies on the long-term viability of the transplanted cells. In this study, we aimed to construct acoustically sensitive nano oxygen carriers to improve cell survival inside the bio-3D printed patch. In this study, we initially created nanodroplets capable of phase transition triggered by ultrasound and integrated them into GelMA (Gelatin Methacryloyl) hydrogels, which were then employed for 3D bioprinting. After adding nanodroplets and ultrasonic irradiation, numerous pores appeared inside the hydrogel with improved permeability. We further encapsulated hemoglobin into nanodroplets (ND-Hb) to construct oxygen carriers. Results of in vitro experiments showed the highest cell survival within the patch of ND-Hb irradiated by the low-intensity pulsed ultrasound (LIPUS) group. The genomic analysis discovered that the increased survival of seeded cells within the patch might be related to the protection of mitochondrial function owing to the improved hypoxic state. Eventually, in vivo studies revealed that the LIPUS+ND-Hb group had improved cardiac function and increased revascularization after myocardial infarction. To summarize, our study successfully improved the permeability of the hydrogel in a non-invasive and efficient manner, facilitating the exchange of substances in the cardiac patch. Moreover, ultrasound-controlled oxygen release augmented the viability of the transplanted cells and expedited the repair of infarcted tissues.

Mussel-inspired polydopamine decorated silane modified-electroconductive gelatin-PEDOT:PSS scaffolds for bone regeneration

This study seeks to simulate both the chemistry and piezoelectricity of bone by synthesizing electroconductive silane-modified gelatin-poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) scaffolds using the freeze drying technique. In order to enhance hydrophilicity, cell interaction, and biomineralization, the scaffolds were functionalized with polydopamine (PDA) inspired by mussels. Physicochemical, electrical, and mechanical analyses were conducted on the scaffolds, as well as in vitro evaluations using the osteosarcoma cell line MG-63. It was found that scaffolds had interconnected porous structures, so the PDA layer formation reduced the size of pores while maintaining scaffold uniformity. PDA functionalization reduced the electrical resistance of the constructs while improving their hydrophilicity, compressive strength, and modulus. As a result of the PDA functionalization and the use of silane coupling agents, higher stability and durability were achieved as well as an improvement in biomineralization capability after being soaked in SBF solution for a month. Additionally, the PDA coating enabled the constructs to enhance viability, adhesion, and proliferation of MG-63 cells, as well as to express alkaline phosphatase and deposit HA, indicating that scaffolds can be used for bone regeneration. Therefore, the PDA-coated scaffolds developed in this study and the non-toxic performance of PEDOT:PSS present a promising approach for further in vitro and in vivo studies.

Electroconductive agarose hydrogels modulate mesenchymal stromal cell adhesion and spreading through protein adsorption

Electrically conductive biomaterials direct cell behavior by capitalizing on the effect of bioelectricity in tissue homeostasis and healing. Many studies have leveraged conductive biomaterials to influence cells and improve tissue healing, even in the absence of external stimulation. However, most studies using electroactive materials neglect characterizing how the inclusion of conductive additives affects the material's mechanical properties, and the interplay between substrate electrical and mechanical properties on cell behavior is poorly understood. Furthermore, mechanisms dictating how electrically conductive materials affect cell behavior in the absence of external stimulation are not explicit. In this study, we developed a mechanically and electrically tunable conductive hydrogel using agarose and the conductive polymer PEDOT:PSS. Under certain conditions, we observed that the hydrogel physical and electrical properties were decoupled. We then seeded human mesenchymal stromal cells (MSCs) onto the hydrogels and observed enhanced adhesion and spreading of MSCs on conductive substrates, regardless of the hydrogel mechanical properties, and despite the gels having no cell-binding sites. To explain this observation, we measured protein interaction with the gels and found that charged proteins adsorbed significantly more to conductive hydrogels. These data demonstrate that conductivity promotes cell adhesion, likely by facilitating increased adsorption of proteins associated with cell binding, providing a better understanding of the mechanism of action of electrically conductive materials.

Conductive fibers for biomedical applications

Bioelectricity has been stated as a key factor in regulating cell activity and tissue function in electroactive tissues. Thus, various biomedical electronic constructs have been developed to interfere with cell behaviors to promote tissue regeneration, or to interface with cells or tissue/organ surfaces to acquire physiological status via electrical signals. Benefiting from the outstanding advantages of flexibility, structural diversity, customizable mechanical properties, and tunable distribution of conductive components, conductive fibers are able to avoid the damage-inducing mechanical mismatch between the construct and the biological environment, in return to ensure stable functioning of such constructs during physiological deformation. Herein, this review starts by presenting current fabrication technologies of conductive fibers including wet spinning, microfluidic spinning, electrospinning and 3D printing as well as surface modification on fibers and fiber assemblies. To provide an update on the biomedical applications of conductive fibers and fiber assemblies, we further elaborate conductive fibrous constructs utilized in tissue engineering and regeneration, implantable healthcare bioelectronics, and wearable healthcare bioelectronics. To conclude, current challenges and future perspectives of biomedical electronic constructs built by conductive fibers are discussed.

Evaluation of Polymeric Particles for Modular Tissue Cultures in Developmental Engineering

Developmental engineering (DE) aims to culture mammalian cells on corresponding modular scaffolds (scale: micron to millimeter), then assemble these into functional tissues imitating natural developmental biology processes. This research intended to investigate the influences of polymeric particles on modular tissue cultures. When poly(methyl methacrylate) (PMMA), poly(lactic acid) (PLA) and polystyrene (PS) particles (diameter: 5-100 µm) were fabricated and submerged in culture medium in tissue culture plastics (TCPs) for modular tissue cultures, the majority of adjacent PMMA, some PLA but no PS particles aggregated. Human dermal fibroblasts (HDFs) could be directly seeded onto large (diameter: 30-100 µm) PMMA particles, but not small (diameter: 5-20 µm) PMMA, nor all the PLA and PS particles. During tissue cultures, HDFs migrated from the TCPs surfaces onto all the particles, while the clustered PMMA or PLA particles were colonized by HDFs into modular tissues with varying sizes. Further comparisons revealed that HDFs utilized the same cell bridging and stacking strategies to colonize single or clustered polymeric particles, and the finely controlled open pores, corners and gaps on 3D-printed PLA discs. These observed cell-scaffold interactions, which were then used to evaluate the adaptation of microcarrier-based cell expansion technologies for modular tissue manufacturing in DE.

3D-Printed conductive polymeric scaffolds with direct current electrical stimulation for enhanced bone regeneration

Various methods have been used to treat bone defects caused by genetic disorders, injury, or disease. Yet, there is still great need to develop alternative approaches to repair damaged bone tissue. Bones naturally exhibit piezoelectric potential, or the ability to convert mechanical stresses into electrical impulses. This phenomenon has been utilized clinically to enhance bone regeneration in conjunction with electrical stimulation (ES) therapies; however, oftentimes with critical-sized bone defects, the bioelectric potential at the site of injury is compromised, resulting in less desirable outcomes. In the present study, the potential of a 3D-printed conductive polymer blend to enhance bone formation through restoration of the bioelectrical microenvironment was evaluated. A commercially available 3D printer was used to create circular, thin-film scaffolds consisting of either polylactide (PLA) or a conductive PLA (CPLA) composite. Preosteoblast cells were seeded onto the scaffolds and subjected to direct current ES via a purpose-built cell culture chamber. It was found that CPLA scaffolds had no adverse effects on cell viability, proliferation or differentiation when compared with control scaffolds. The addition of ES, however, resulted in a significant increase in the expression of osteocalcin, a protein indicative of osteoblast maturation, after 14 days of culture. Furthermore, xylenol orange staining also showed the presence of increased mineralized calcium nodules in cultures undergoing stimulation. This study demonstrates the potential for low-cost, conductive scaffolding materials to support cell viability and enhance in vitro mineralization in conjunction with ES.

Bone Deterioration in Response to Chronic High-Altitude Hypoxia Is Attenuated by a Pulsed Electromagnetic Field Via the Primary Cilium/HIF-1α Axis

Chronic high-altitude hypoxia induces irreversible abnormalities in various organisms. Emerging evidence indicates that hypobaric hypoxia markedly suppresses bone mass and bone strength. However, few effective means have been identified to prevent such bone deficits. Here, we assessed the potential of pulsed electromagnetic fields (PEMFs) to noninvasively resist bone deterioration induced by hypobaric hypoxia. We observed that exogenous PEMF treatment at 15 Hz and 20 Gauss (Gs) improved the cancellous and cortical bone mass, bone microstructure, and skeletal mechano-properties in rats subjected to chronic exposure of hypobaric hypoxia simulating an altitude of 4500 m for 6 weeks by primarily modulating osteoblasts and osteoblast-mediated bone-forming activity. Moreover, our results showed that whereas PEMF stimulated the functional activity of primary osteoblasts in hypoxic culture in vitro, it had negligible effects on osteoclasts and osteocytes exposed to hypoxia. Mechanistically, the primary cilium was found to function as the major electromagnetic sensor in osteoblasts exposed to hypoxia. The polycystins PC-1/PC-2 complex was identified as the primary calcium channel in the primary cilium of hypoxia-exposed osteoblastic cells responsible for the detection of external PEMF signals, and thereby translated these biophysical signals into intracellular biochemical events involving significant increase in the intracellular soluble adenylyl cyclase (sAC) expression and subsequent elevation of cyclic adenosine monophosphate (cAMP) concentration. The second messenger cAMP inhibited the transcription of oxygen homeostasis-related hypoxia-inducible factor 1-alpha (HIF-1α), and thus enhanced osteoblast differentiation and improved bone phenotype. Overall, the present study not only advances our understanding of bone physiology at high altitudes, but more importantly, proposes effective means to ameliorate high altitude-induced bone loss in a noninvasive and cost-effective manner. © 2023 American Society for Bone and Mineral Research (ASBMR).