Rehabilitation exercise-driven symbiotic electrical stimulation system accelerating bone regeneration

Force-electric biomaterials and devices for regenerative medicine

There is a growing recognition that force-electric conversion biomaterials and devices can convert mechanical energy into electrical energy without an external power source, thus potentially revolutionizing the use of electrical stimulation in the biomedical field. Based on this, this review explores the application of force-electric biomaterials and devices in the field of regenerative medicine. The article focuses on piezoelectric biomaterials, piezoelectric devices and triboelectric devices, detailing their categorization, mechanisms of electrical generation and methods of improving electrical output performance. Subsequently, different sources of driving force for electroactive biomaterials and devices are explored. Finally, the biological applications of force-electric biomaterials and devices in regenerative medicine are presented, including tissue regeneration, functional modulation of organisms, and electrical stimulation therapy. The aim of this review is to emphasize the role of electrical stimulation generated by force-electric conversion biomaterials and devices on the regulation of bioactive molecules, ion channels and information transfer in living systems, and thus affects the metabolic processes of organisms. In the future, physiological modulation of electrical stimulation based on force-electric conversion is expected to bring important scientific advances in the field of regenerative medicine.

From Mechanoelectric Conversion to Tissue Regeneration: Translational Progress in Piezoelectric Materials

Piezoelectric materials, capable of converting mechanical stimuli into electrical signals, have emerged as promising tools in regenerative medicine due to their potential to stimulate tissue repair. Despite a surge in research on piezoelectric biomaterials, systematic insights to direct their translational optimization remain limited. This review addresses the current landscape by bridging fundamental principles with clinical potential. The biomimetic basis of piezoelectricity, key molecular pathways involved in the synergy between mechanical and electrical stimulation for enhanced tissue regeneration, and critical considerations for material optimization, structural design, and biosafety is discussed. More importantly, the current status and translational quagmire of mechanisms and applications in recent years are explored. A mechanism-driven strategy is proposed for the therapeutic application of piezoelectric biomaterials for tissue repair and identify future directions for accelerated clinical applications.

Bionic Triboelectric Nanogenerator Activates the "mechano-electro-biochemical" Cascade Effect In Situ to Accelerate Critical-Sized Bone Defect Repair

The loss of the intrinsic "mechano-electro-biochemical" cascade effect in critical-sized bone defects (CSBDs) impedes the bone self-healing process. Traditional strategies cannot provide bionic electrical output, thereby failing to sufficiently activate the "mechano-electro-biochemical" cascade effect in situ and limiting the repair efficiency of CSBDs. Here, a bionic, self-adhesive, and biodegradable triboelectric nanogenerator (TENG) called PPCs-TENG using silk-fibroin-derived peptide (Cs)-grafted polydopamine-polyacrylamide (PPCs) as the electrode layer is fabricated. It provides bionic electrical stimulation (bio-ES) in response to the host's motion status. It reestablishes the resting potential during host rest and generates real-time biofeedback action potential during host movement. Further, it activates the "mechano-electro-biochemical" cascade effect for accelerating the repair of CSBDs. The bio-ES generated from PPCs-TENG enriches extracellular osteogenesis-related biochemical factors at the CSBD site. It also activates the intracellular mechanosensitive protein Piezo1, thereby promoting calcium signaling and intracellular mechano-transduction pathways. This activation enhances the proliferation and migration of bone marrow stem cells (BMSCs) and human umbilical vein endothelial cells (HUVECs), and promotes osteogenic differentiation in BMSCs and angiogenesis in HUVECs. In vivo tests demonstrate that PPCs-TENG significantly accelerates the repair of CSBDs in situ.

An Intelligent and Conductive Hydrogel with Multiresponsive and ROS Scavenging Properties for Infection Prevention and Anti-Inflammatory Treatment Assisted by Electrical Stimulation for Diabetic Wound

Diabetic wounds experience a hyperglycemic, hypoxic environment, combined with ongoing oxidative stress and inflammatory imbalances, significantly disrupts normal healing process. Advanced hydrogels have been considered one of the most exciting medical biomaterials for the potential in wounds healing. Herein, a novel conductive hydrogel (HEPP), designed to release nanozyme (PTPPG) in response to its microenvironment, was created to facilitate glucose (Glu) catabolism. Furthermore, the HEPP integrates photodynamic therapy (PDT), photothermal therapy (PTT), and self-cascading reactive oxygen species (ROS) to prevent bacterial infections while ensuring a continuous supply of oxygen (O2) to the wound. The HEPP not only adeptly controls high ROS levels, but also enhances the regulation of inflammation in the wound area via electrical stimulation (ES), thereby promoting healing that is supported by the immune response. Studies conducted in vitro, along with transcriptomic analyses, indicate that ES primarily mitigates inflammation by regulating Interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α). The effects of HEPP combined with ES are primarily connected to their impact on TNF signaling pathways. By reducing the formation of ROS and employing ES to effectively lessen inflammation, this approach offers an innovative method to manage complicated diabetic wounds, ulcers, and a range of inflammatory conditions linked to infections.

Electro- and Magneto-Active Biomaterials for Diabetic Tissue Repair: Advantages and Applications

The diabetic tissue repair process is frequently hindered by persistent inflammation, infection risks, and a compromised tissue microenvironment, which lead to delayed wound healing and significantly impact the quality of life for diabetic patients. Electromagnetic biomaterials offer a promising solution by enabling the intelligent detection of diabetic wounds through electric and magnetic effects, while simultaneously improving the pathological microenvironment by reducing oxidative stress, modulating immune responses, and exhibiting antibacterial action. Additionally, these materials inherently promote tissue regeneration by regulating cellular behavior and facilitating vascular and neural repair. Compared to traditional biomaterials, electromagnetic biomaterials provide advantages such as noninvasiveness, deep tissue penetration, intelligent responsiveness, and multi-stimuli synergy, demonstrating significant potential to overcome the challenges of diabetic tissue repair. This review comprehensively examines the superiority of electromagnetic biomaterials in diabetic tissue repair, elucidates the underlying biological mechanisms, and discusses specific design strategies and applications tailored to the pathological characteristics of diabetic wounds, with a focus on skin wound healing and bone defect repair. By addressing current limitations and pursuing multi-faceted strategies, electromagnetic biomaterials hold significant potential to improve clinical outcomes and enhance the quality of life for diabetic patients.

Recent Progress of Soft and Bioactive Materials in Flexible Bioelectronics

Materials that establish functional, stable interfaces to targeted tissues for long-term monitoring/stimulation equipped with diagnostic/therapeutic capabilities represent breakthroughs in biomedical research and clinical medicine. A fundamental challenge is the mechanical and chemical mismatch between tissues and implants that ultimately results in device failure for corrosion by biofluids and associated foreign body response. Of particular interest is in the development of bioactive materials at the level of chemistry and mechanics for high-performance, minimally invasive function, simultaneously with tissue-like compliance and in vivo biocompatibility. This review summarizes the most recent progress for these purposes, with an emphasis on material properties such as foreign body response, on integration schemes with biological tissues, and on their use as bioelectronic platforms. The article begins with an overview of emerging classes of material platforms for bio-integration with proven utility in live animal models, as high performance and stable interfaces with different form factors. Subsequent sections review various classes of flexible, soft tissue-like materials, ranging from self-healing hydrogel/elastomer to bio-adhesive composites and to bioactive materials. Additional discussions highlight examples of active bioelectronic systems that support electrophysiological mapping, stimulation, and drug delivery as treatments of related diseases, at spatiotemporal resolutions that span from the cellular level to organ-scale dimension. Envisioned applications involve advanced implants for brain, cardiac, and other organ systems, with capabilities of bioactive materials that offer stability for human subjects and live animal models. Results will inspire continuing advancements in functions and benign interfaces to biological systems, thus yielding therapy and diagnostics for human healthcare.

Ultrasound-Responsive Piezoelectric Membrane Promotes Osteoporotic Bone Regeneration via the "Two-Way Regulation" Bone Homeostasis Strategy

The repair of osteoporotic bone defects remains inadequately addressed, primarily due to a disruption in bone homeostasis, characterized by insufficient bone formation and excessive bone resorption. Current research either focuses on promoting bone formation or inhibiting bone resorption, however, the bone repair efficacy of these single-target therapeutic strategies is limited. Herein, a "two-way regulation" bone homeostasis strategy is proposed utilizing piezoelectric composite membranes (DAT/KS), capable of simultaneously regulating osteogenesis and osteoclastogenesis, with high piezoelectric performance, good biocompatibility, and excellent degradability, to promote bone regeneration under osteoporotic conditions. The DAT/KS membrane under ultrasound (US) treatment enables the controlled modulation of piezoelectric stimulation and the release of saikosaponin D (SSD), which promotes osteogenic differentiation while simultaneously inhibiting osteoclast differentiation and function, thereby effectively restoring bone homeostasis and enhancing osteoporotic bone repair. Mechanistic insights reveal the promotion of both canonical and non-canonical Wnt signaling in bone marrow mesenchymal stem cells (BMSCs), which determines their osteogenic differentiation fate, and the downregulation of the NF-κB signaling in bone marrow mononuclear macrophages (BMMs). This study presents optimized sono-piezoelectric biomaterials capable of bidirectionally regulating both osteogenic and osteoclastic differentiation, providing a new potential therapeutic approach for pathological bone injuries.

Hydrogel Containing Bismuth Molybdate Nanosheets with Piezoelectricity and Nanoenzyme Activity for Promoting Osteoblast Responses

The development of piezoelectric biomaterials with the capability to produce electrical signals and scavenge reactive oxygen species (ROS) is a novel strategy for stimulating osteoblast responses and promoting bone regeneration. Herein, tungsten (W), iridium (Ir), and ruthenium (Ru) codoped bismuth molybdate (4(W/Ru/Ir)-BMO) nanosheets with improved piezoelectricity and enzyme-like (CAT-like and SOD-like) activities were constructed by using the hydrothermal method. A composite hydrogel of oxidized sodium alginate/gelatin (OSA/GEL) and 4(W/Ru/Ir)-BMO (OSA/GEL/4-B) was also prepared. Due to the presence of 4(W/Ru/Ir)-BMO, OSA/GEL/4-B exhibited not only piezoelectricity but also enzyme-like activities. Under ultrasound (US), OSA/GEL/4-B generated electrical signals that significantly promoted the proliferation and osteogenic differentiation of bone marrow stromal cells. Furthermore, the piezoelectric effect of OSA/GEL/4-B improved the CAT-like (production of oxygen) and SOD-like (scavenger of ROS) activities. The improved piezoelectricity of 4(W/Ru/Ir)-BMO was attributed to the codoping of W, Ir, and Ru ions, which resulted in lattice distortion and enhanced crystal asymmetry, which produced electrical signals for regulating the osteogenic microenvironment. Moreover, the improvement of enzyme-like activities was attributed to the enhanced piezoelectric effect by the codoping of W, Ir, and Ru ions, which generated a piezoelectric field triggered by US that accelerated electron transfer for alleviating cellular oxidative stress and provided an antioxidant microenvironment for osteoblast responses. This piezoelectric hydrogel may provide a novel pathway for promoting osteogenic differentiation and bone regeneration.

Enhancing Bone Health with Conjugated Linoleic Acid: Mechanisms, Challenges, and Innovative Strategies

Conjugated linoleic acid (CLA) is a bioactive compound known for its anti-inflammatory, anti-carcinogenic, and metabolic effects, with growing interest in its role in supporting bone health. Preclinical studies, particularly those involving the t10c12 isomer, have shown that CLA can enhance bone mineral density (BMD) by enhancing bone formation and reducing bone resorption, indicating its potential as a therapeutic agent to improve bone health. However, clinical trials have yielded inconsistent results, underscoring the difficulty in translating animal model successes to human applications. A major challenge is CLA's low water solubility, poor absorption, and limited bioavailability, which restrict its therapeutic effectiveness. To address these issues, nanoparticle-based delivery systems have been proposed to improve its solubility, stability, and resistance to oxidative damage, thereby enhancing its bioactivity. Recent studies also suggest that electrical stimulation can stimulate bone regeneration by promoting bone cell proliferation, differentiation, and adherence to scaffolds. This review explores the combined use of CLA supplementation and electrical stimulation as a novel approach to improving bone health, particularly in osteoporosis management. By integrating CLA's biological effects with the regenerative potential of electrical stimulation, this multimodal strategy offers a promising method for enhancing bone restoration, with significant implications for clinical applications in bone health.

Closed-loop rehabilitation of upper-limb dyskinesia after stroke: from natural motion to neuronal microfluidics

This review proposes an innovative closed-loop rehabilitation strategy that integrates multiple subdomains of stroke science to address the global challenge of upper-limb dyskinesia post-stroke. Despite advancements in neural remodeling and rehabilitation research, the compartmentalization of subdomains has limited the effectiveness of current rehabilitation strategies. Our approach unites key areas-including the post-stroke brain, upper-limb rehabilitation robotics, motion sensing, metrics, neural microfluidics, and neuroelectronics-into a cohesive framework designed to enhance upper-limb motion rehabilitation outcomes. By leveraging cutting-edge technologies such as lightweight rehabilitation robotics, advanced motion sensing, and neural microfluidic models, this strategy enables real-time monitoring, adaptive interventions, and personalized rehabilitation plans. Furthermore, we explore the potential of closed-loop systems to drive neural plasticity and functional recovery, offering a transformative perspective on stroke rehabilitation. Finally, we discuss future directions, emphasizing the integration of emerging technologies and interdisciplinary collaboration to advance the field. This review highlights the promise of closed-loop strategies in achieving unprecedented integration of subdomains and improving post-stroke upper-limb rehabilitation outcomes.

Ultrasound-responsive smart biomaterials for bone tissue engineering

Bone defects resulting from trauma, tumors, or other injuries significantly impact human health and quality of life. However, current treatments for bone defects are constrained by donor shortages and immune rejection. Bone tissue engineering has partially alleviated the limitations of traditional bone repair methods. The development of smart biomaterials that can respond to external stimuli to modulate the biofunctions has become a prominent area of research. Ultrasound technology is regarded as an optimal "remote controller" and "trigger" for bone repair biomaterials. This review reports the comprehensive and systematic overview of ultrasound-responsive bone repair smart biomaterials. It presents the fundamental theories of bone repair, the definition of ultrasound, and its applications. Furthermore, the review summarizes the ultrasound effect mechanisms of biomaterials and their roles in bone repair, including detailed studies on anti-inflammation, immunomodulation, and cell therapy. Finally, the advantages of ultrasound-responsive smart biomaterials and their future prospects in this field are discussed.

Safety and preliminary efficacy of an electrically stimulated implant for mandibular bone regeneration: a pilot study in a large animal model

OBJECTIVES

Large mandibular defects present challenges for bone regeneration. This pilot study evaluates the safety and preliminary efficacy of direct electrical stimulation (ES) on tissue healing in a preclinical model, testing whether ES can enhance bone formation in critical-size mandibular defects.

MATERIALS AND METHODS

Six adult mini pigs with critical-size mandibular defects were used in a split-mouth design. The test group (n = 6) received 0.5 V AC/20 Hz ES for 3 × 45 min daily over three weeks, while the control group (n = 6) had no stimulation. Safety, early bone growth, and soft tissue effects were assessed at three locations: S1 (cancellous bone interface), S2 (middle of the defect), and S3 (pristine dense bone).

RESULTS

The ES group showed no adverse effects, confirming implant safety. The ES group exhibited significantly higher bone formation, particularly in S2 and S3. Enhanced vascularization and immune response, in terms of increased mast cells, were also observed in S2.

CONCLUSIONS

The implant device with ES is safe and promotes bone formation and vascularization in select sub-regions (S2 and S3). However, ES alone may not suffice for complete bone regeneration in critical-sized defects, and further optimization is needed.

CLINICAL RELEVANCE

This study demonstrates the potential of ES to improve bone healing in large mandibular defects, offering insights for clinical use in maxillofacial reconstruction.

Recent Advances in Polyvinylidene Fluoride with Multifunctional Properties in Nanogenerators

Amid the global energy crisis and rising emphasis on sustainability, efficient energy harvesting has become a research priority. Nanogenerators excel in converting abundant mechanical and thermal energy into electricity, offering a promising path for sustainable solutions. Among various nanogenerator's materials, Polyvinylidene fluoride (PVDF), with its distinctive molecular structure, exhibits multifunctional electrical properties including dielectric, piezoelectric and pyroelectric characteristics. These properties combined with its excellent flexibility make PVDF a prime candidate material for nanogenerators. In nanogenerators, this material is capable of efficiently collecting and converting energy. This paper discusses how PVDF's properties are manifested in three types of nanogenerators and compares the performance of these nanogenerators. In addition, strategies to improve the output performance of nanogenerators are demonstrated, including physical and chemical modification of materials, as well as structural optimization strategies such as hybrid structures and external circuits. It also introduces the application of this material in natural and human energy harvesting, as well as its promising prospects in medical technologies and smart home systems. The aim is to promote the use of PVDF in self-powered sensing, energy harvesting and smart monitoring, thereby providing valuable insights for designing more efficient and versatile nanogenerators.

Dual-Gradient Silk-Based Hydrogel for Spatially Targeted Delivery and Osteochondral Regeneration

Contemporary clinical interventions for cartilage injuries focus on symptom management through pharmaceuticals and surgical procedures. Recent research has aimed at developing innovative scaffolds with biochemical elements, yet challenges like inadequate targeted delivery and reduced load-bearing capacity hinder their adoption. Inspired by the spatial gradients of biophysical and biochemical cues in native osteochondral tissues, a silk-based hydrogel that facilitates spontaneous dual-gradient formation, including mechanical gradients and growth factor gradients, for tissue regeneration, is presented. Driven by an electrical field, the hydrogel transitions from stiff to soft along the anode-to-cathode direction, mimicking the anisotropic structure of natural tissues. Simultaneously, incorporated growth factors encapsulated by charged monomers migrate to the cathode region, creating another parallel gradient that enables their sustained release. This design maintains bioactivity and enhances programmable growth factor concentration in the defect environment. In a rabbit model with full-thickness osteochondral defects, the dual-gradient hydrogel demonstrates significant potential for promoting osteochondral regeneration, offering a promising tool for clinical translation.

Natural collagen scaffold with intrinsic piezoelectricity for enhanced bone regeneration

Materials-mediated piezoelectric signals have been widely applied in bone regeneration. Collagen is the most abundant protein in the human body, and native collagen with complete tertiary structure shows efficient piezoelectricity. However, the traditional collagen scaffolds are lack of piezoelectricity due to the destruction of the complete tertiary structure. Here, natural collagen scaffolds with the complete tertiary structure were prepared. Alkali treatment made the collagen scaffold lose piezoelectricity. The collagen with/without piezoelectricity (PiezoCol/NCol) scaffolds both possessed good cytocompatibility and promoted cell adhesion. After being implanted subcutaneously, the NCol scaffold almost did not affect bone regeneration with/without ultrasound treatment. However, under ultrasound treatment, the PiezoCol scaffold promoted the new bone formation with enhanced osteogenic differentiation, angiogenesis, and neural differentiation, meaning that piezoelectricity endows collagen with satisfactory promotion for bone regeneration. Meanwhile, the PiezoCol scaffold can also accelerate bone formation without ultrasound treatment, which should be attributed to the daily exercise-caused weak piezoelectric stimulation. Further, the proteomic analysis revealed the mechanism by which the PiezoCol scaffold promoted bone tissue formation via mainly upregulating the PI3K-Akt signaling pathway. This study provides a new strategy to enhance the osteoinduction of collagen scaffold for bone regeneration by maintaining intrinsic piezoelectricity.

Advances in Electrically Conductive Hydrogels: Performance and Applications

Electrically conductive hydrogels are highly hydrated 3D networks consisting of a hydrophilic polymer skeleton and electrically conductive materials. Conductive hydrogels have excellent mechanical and electrical properties and have further extensive application prospects in biomedical treatment and other fields. Whereas numerous electrically conductive hydrogels have been fabricated, a set of general principles, that can rationally guide the synthesis of conductive hydrogels using different substances and fabrication methods for various application scenarios, remain a central demand of electrically conductive hydrogels. This paper systematically summarizes the processing, performances, and applications of conductive hydrogels, and discusses the challenges and opportunities in this field. In view of the shortcomings of conductive hydrogels in high electrical conductivity, matchable mechanical properties, as well as integrated devices and machines, it is proposed to synergistically design and process conductive hydrogels with applications in complex surroundings. It is believed that this will present a fresh perspective for the research and development of conductive hydrogels, and further expand the application of conductive hydrogels.

Tissue-Adaptable Hydrogel for Mechanically Compliant Bioelectronic Interfaces

A hydrogel with tissue-like softness and ideal biocompatibility has emerged as a promising candidate for bioelectronics, especially in bidirectional bioelectrical transduction and communication. Conformal standardized hydrogel biointerfaces are in urgent demand to bridge electronic devices and irregular tissue surfaces. Herein, we presented a shape-adaptative electroactive hydrogel with tissue-adapted conductivity (≈1.03 S/m) by precisely regulating molecular chains and polymer networks of multisource gelatin at the molecular scale. Local amine-carboxylate electrostatic domains formed by ion interactions between gelatin and sodium citrate significantly enhance the physiological adaptability and regulate the biodegradation period. Benefiting from the reversible fluid-gel transition property, the hydrogel can be in situ gelatinized and establish a dynamic compliance bioelectronic interface with tissues by chemical bonding and the physical topological effect. Further, the mechanical-electrical coupling capacity of the hydrogel interface allows for bioelectrical conduction function reconstruction and electrical stimulation therapy after mechanical bridging at tissue defects to boost tissue regeneration and sensory restoration.

3D printed shape-memory piezoelectric scaffolds with in-situ self-power properties for bone defect repair

Electrical stimulation has been shown to regulate early immunity and late-stage osteogenesis in bone repair. However, achieving in-situ electrical stimulation in the form of self-power in vivo during the initial postoperative stages when the patients have limited mobility remains challenging. In this study, we developed a 3D-printed in-situ self-powered composite scaffold composed of shape memory polyurethane elastomers (SMPU) and polyvinylidene fluoride (PVDF) piezoelectric nanofibers. The composite scaffold demonstrates excellent shape memory performance, allowing for minimally invasive implantation. During the shape memory process, the composite scaffold can provide mechanical force stimulation to PVDF nanofibers to generate charge. Therefore, self-power was achieved through the integration of the shape memory process and piezoelectric effects, and it can be used for in-situ electrical stimulation during the initial postoperative period. Additionally, the composite scaffold can output voltage under continuous mechanical force stimulation, indicating that the patients can apply sustained mechanical force stimulation to the composite scaffold to output voltage through rehabilitation exercises when the patients regain mobility. Both cell experiments and animal studies confirmed that this composite scaffold can effectively regulate the immune microenvironment and enhance osteogenesis. This study successfully achieves in-situ electrical stimulation in the form of self-power by integrating the shape memory process and piezoelectric effects, which is expected to be an effective repair strategy for bone tissue engineering.

3D printed scaffolds with multistage osteogenic activity for bone defect repair

The bone defect repair is a complex process including immune regulation, stem cell osteogenic differentiation and extracellular matrix mineralization. Current bone tissue engineering approaches often fail to adapt throughout the above osteogenic process, resulting in suboptimal repair outcomes. To address this problem, a 3D-printed scaffold with multistage osteogenic activity based on shape-memory elastomer and electroactive material is developed. The scaffold exhibits excellent shape memory performance and can trigger shape recovery by physiological temperature. The physiological temperature-triggered shape-memory behavior makes the scaffold promising for minimally invasive implantation. After electric field polarization, the scaffold's surface carries the negative charge, which can activate the PI3K/Akt signaling pathway to promote the polarization of macrophages to M2 phenotype and activate the FAK/ERK signaling pathway to promote osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs), indicating that the scaffold can effectively participate in immune microenvironment regulation and stem cell osteogenic differentiation. Additionally, the negative charge on the scaffold's surface can attract calcium and phosphate ions, forming a mineralized matrix and promoting late-stage extracellular matrix mineralization by continuously supplying mineralizing ions such as calcium and phosphate. Overall, this study introduces a 3D-printed scaffold with multistage osteogenic activity, offering a promising strategy for bone defect repair.

Research status of biomaterials based on physical signals for bone injury repair

Bone defects repair continues to be a significant challenge facing the world. Biological scaffolds, bioactive molecules, and cells are the three major elements of bone tissue engineering, which have been widely used in bone regeneration therapy, especially with the rise of bioactive molecules in recent years. According to their physical properties, they can be divided into force, magnetic field (MF), electric field (EF), ultrasonic wave, light, heat, etc. However, the transmission of bioactive molecules has obvious shortcomings that hinder the development of the tissue-rearing process. This paper reviews the mechanism of physical signal induction in bone tissue engineering in recent years. It summarizes the application strategies of physical signal in bone tissue engineering, including biomaterial designs, physical signal loading strategies and related pathways. Finally, the ongoing challenges and prospects for the future are discussed.

Piezoelectric Biomaterial with Advanced Design for Tissue Infection Repair

Bacterial infection has become the most dangerous factor in tissue repair, which strongly affects the tissue regeneration efficiency and wellness of patients. Piezoelectric materials exhibit the outstanding advantage of producing electrons without external power supply. The ability of electron enrichment and reactive oxygen species generation through noninvasive stimulations enables piezoelectric materials the potential applications of antibacterial. Many studies have proved the feasibility of piezoelectric materials as a functional addition in antibacterial biomaterial. In fact, numerous piezoelectric materials with ingenious designs are reported to be effective in antibacterial processes. This review summarizes the antibacterial mechanisms of piezoelectric, illuminating their potential in combating bacteria. Recent advancement in the design and construction of piezoelectric biomaterial including defect engineering, heterojunction, synergy with metal and the composite scaffold configuration are thoroughly reviewed. Moreover, the applications and therapeutic effects of piezoelectric materials in common tissues with antibacterial requirements are introduced, such as orthopedics, dental, and wound healing. Finally, the development prospects and points deserving further exploration are listed. This review is expected to provide valuable insight into the relationship between antibacterial processes and piezoelectric materials, further inspiring constructive development in this emerging scientific discipline.

Neuroregulation during Bone Formation and Regeneration: Mechanisms and Strategies

The skeleton is highly innervated by numerous nerve fibers. These nerve fibers, in addition to transmitting information within the bone and mediating bone sensations, play a crucial role in regulating bone tissue formation and regeneration. Traditional bone tissue engineering (BTE) often fails to achieve satisfactory outcomes when dealing with large-scale bone defects, which is frequently related to the lack of effective reconstruction of the neurovascular network. In recent years, increasing research has revealed the critical role of nerves in bone metabolism. Nerve fibers regulate bone cells through neurotransmitters, neuropeptides, and peripheral glial cells. Furthermore, nerves also coordinate with the vascular and immune systems to jointly construct a microenvironment favorable for bone regeneration. As a signaling driver of bone formation, neuroregulation spans the entire process of bone physiological activities from the embryonic formation to postmaturity remodeling and repair. However, there is currently a lack of comprehensive summaries of these regulatory mechanisms. Therefore, this review sketches out the function of nerves during bone formation and regeneration. Then, we elaborate on the mechanisms of neurovascular coupling and neuromodulation of bone immunity. Finally, we discuss several novel strategies for neuro-bone tissue engineering (NBTE) based on neuroregulation of bone, focusing on the coordinated regeneration of nerve and bone tissue.

Low-Intensity Pulsed Ultrasound Responsive Scaffold Promotes Intramembranous and Endochondral Ossification via Ultrasonic, Thermal, and Electrical Stimulation

Multiple physical stimuli are expected to produce a synergistic effect to promote bone tissue regeneration. Low-intensity pulsed ultrasound (LIPUS) has been clinically used in bone repair for the mechanical stimulation that it provides. In addition, LIPUS can also excite the biomaterials to generate other physical stimuli such as thermal or electrical stimuli. In this study, a scaffold based on decellularized adipose tissue (DAT) is established by incorporating polydopamine-modified multilayer black phosphorus nanosheets (pDA-mBP@DAT). Their effect on bone repair under LIPUS stimulation and the potential mechanisms are further investigated. This scaffold possesses piezoelectric properties and generates a mild thermogenic stimulus when stimulated by LIPUS. With superior properties, this scaffold is demonstrated to have good cytocompatibility in vitro and in vivo. Simultaneously, LIPUS promotes cell attachment, migration, and osteogenic differentiation in the pDA-mBP@DAT scaffold. Furthermore, the combined use of pDA-mBP@DAT and LIPUS significantly affects the regenerative effect in rat models of critical-sized calvarial defects. The possible mechanisms include promoting osteogenesis and neovascularization and activating the Piezo1. This study presents insight into speeding up bone regeneration by the synergistic combination of LIPUS and pDA-mBP@DAT scaffolds.

Study on Recovery Strategy of Hearing Loss & SGN Regeneration Under Physical Regulation

The World Health Organization (WHO) reports that by 2050, nearly 2.5 billion people are expected to have some degree of hearing loss (HL) and at least 700 million will need hearing rehabilitation. Therefore, there is an urgent need to develop treatment strategies for HL. At present, the main treatment strategies for HL are hearing aids and cochlear implants (CIs), which cannot achieve a radical cure for HL. Relevant studies have shown that the most fundamental treatment strategy for sensorineural hearing loss (SNHL) is to regenerate hair cells and spiral ganglion neurons (SGNs) through stem cells to repair the structure and function of cochlea. In addition, physical stimulation strategies, such as electricity, light, and magnetism have also been used to promote SGN regeneration. This review systematically introduces the classification, principle and latest progress of the existing hearing treatment strategies and summarizes the advantages and disadvantages of each strategy. The research progress of physical regulation mechanism is discussed in detail. Finally, the problems in HL repair strategies are summarized and the future development direction is prospected, which could provide new ideas and technologies for the optimization of hearing treatment strategies and the research of SGN repair and regeneration through physical regulation.

Periosteum-bone inspired hierarchical scaffold with endogenous piezoelectricity for neuro-vascularized bone regeneration

The development of scaffolds for repairing critical-sized bone defects heavily relies on establishing a neuro-vascularized network for proper penetration of nerves and blood vessels. Despite significant advancements in using artificial bone-like scaffolds infused with various agents, challenges remain. Natural bone tissue consists of a porous bone matrix surrounded by a neuro-vascularized periosteum, with unique piezoelectric properties essential for bone growth. Drawing inspiration from this assembly, we developed a periosteum-bone-mimicking bilayer scaffold with piezoelectric properties for regeneration of critical-sized bone defects. The periosteum-like layer of this scaffold features a double network hydrogel composed of chelated alginate, gelatin methacrylate, and sintered whitlockite nanoparticles, emulating the viscoelastic and piezoelectric properties of the natural periosteum. The bone-like layer is composed of a porous structure of chitosan and bioactive hydroxyapatite created through a biomineralization process. Unlike conventional bone-like scaffolds, this bioinspired bilayer scaffold significantly enhances osteogenesis, angiogenesis, and neurogenesis combined with low-intensity pulsed ultrasound-assisted piezoelectric stimulation. Such a scheme enhances neuro-vascularized bone regeneration in vivo. The results suggest that the bilayer scaffold could serve as an effective self-powered electrical stimulator to expedite bone regeneration under dynamic physical stimulation.

Mild Hyperthermia Accelerates Bone Repair by Dynamically Regulating iNOS/Arg1 Balance in the Early Stage

Mild hyperthermia therapy has garnered interest as an adjunctive treatment for bone repair. However, its optimal timing, duration, and underlying mechanisms remain unclear. In this study, how mild hyperthermia supports bone repair during the early stages is assesed. These findings reveal that mild hyperthermia accelerates bone regeneration by dynamically regulating inducible nitric oxide synthase/arginase 1 (iNOS/Arg1) balance. This process involves macrophage polarization to the M1 phenotype through iNOS activation, followed by a rapid transition to the M2 phenotype through Arg1 activation after 3 days of sustained mild hyperthermia. RNA-Seq reveals that a single day of mild hyperthermia induced immune alterations aligned with the early inflammatory phase of bone repair, characterized by osteoclast activation, cell recruitment, and neovascularization, thereby preparing for the transition to the repair phase. Experiments involving subcutaneous abscesses, subcutaneous embedding, and critical cranial bone defects further confirm that early mild hyperthermia treatment dynamically regulates macrophage phenotypes. This regulation enhances early antibacterial activity, promotes angiogenesis, and facilitates the transition from inflammation to repair, ultimately accelerating bone-defect repair. This study is the first to elucidate the dual temporal effects of early mild hyperthermia on immune regulation, offering insights into the optimal timing and duration of photothermal therapy following bone repair surgery.

Anisotropic conductive eutectogels for strain sensing and triboelectric nanogeneration in extreme environments

Conductive hydrogels have attracted widespread attention for their promising application prospects in portable and flexible electronic devices. However, hydrogels commonly suffer from problems such as solvent volatilization and freezing at low temperatures. Inspired by tissues such as human muscles, tendons, and ligaments, this study proposes a facile method to produce anisotropic conductive strong and tough eutectogels through directional freezing integrated with solvent substitution (DFSS) strategy. Eutectogels with anisotropic characteristics exhibit a highly anisotropic structure, conferring distinctive anisotropic mechanical properties and electrical conductivity. The prepared anisotropic PVA-M-DES eutectogels exhibit excellent mechanical properties (high strength of 6.31 MPa, high toughness of 20.75 MJ m-3, elastic modulus of 2.36 MPa, and fracture strain of 596%), high conductivity (0.17 S m-1), excellent anti-freezing and anti-drying properties. Environment-tolerant anisotropic PVA-M-DES eutectogels can be assembled into strain sensor and triboelectric nanogenerator to achieve real-time monitoring of various human motions and have potential applications in wearable electronics, personal healthcare, energy harvesting, and human-machine interfaces.

Hierarchy Reproduction: Multiphasic Strategies for Tendon/Ligament-Bone Junction Repair

Tendon/ligament-bone junctions (T/LBJs) are susceptible to damage during exercise, resulting in anterior cruciate ligament rupture or rotator cuff tear; however, their intricate hierarchical structure hinders self-regeneration. Multiphasic strategies have been explored to fuel heterogeneous tissue regeneration and integration. This review summarizes current multiphasic approaches for rejuvenating functional gradients in T/LBJ healing. Synthetic, natural, and organism-derived materials are available for in vivo validation. Both discrete and gradient layouts serve as sources of inspiration for organizing specific cues, based on the theories of biomaterial topology, biochemistry, mechanobiology, and in situ delivery therapy, which form interconnected network within the design. Novel engineering can be constructed by electrospinning, 3-dimensional printing, bioprinting, textiling, and other techniques. Despite these efforts being limited at present stage, multiphasic scaffolds show great potential for precise reproduction of native T/LBJs and offer promising solutions for clinical dilemmas.

Functional antimicrobial peptide-loaded 3D scaffolds for infected bone defect treatment with AI and multidimensional printing

Infection is the most prevalent complication of fractures, particularly in open fractures, and often leads to severe consequences. The emergence of bacterial resistance has significantly exacerbated the burden of infection in clinical practice, making infection control a significant treatment challenge for infectious bone defects. The implantation of a structural stent is necessary to treat large bone defects despite the increased risk of infection. Therefore, there is a need for the development of novel antibacterial therapies. The advancement in antibacterial biomaterials and new antimicrobial drugs offers fresh perspectives on antibacterial treatment. Although antimicrobial 3D scaffolds are currently under intense research focus, relying solely on material properties or antibiotic action remains insufficient. Antimicrobial peptides (AMPs) are one of the most promising new antibacterial therapy approaches. This review discusses the underlying mechanisms behind infectious bone defects and presents research findings on antimicrobial peptides, specifically emphasizing their mechanisms and optimization strategies. We also explore the potential prospects of utilizing antimicrobial peptides in treating infectious bone defects. Furthermore, we propose that artificial intelligence (AI) algorithms can be utilized for predicting the pharmacokinetic properties of AMPs, including absorption, distribution, metabolism, and excretion, and by combining information from genomics, proteomics, metabolomics, and clinical studies with computational models driven by machine learning algorithms, scientists can gain a comprehensive understanding of AMPs' mechanisms of action, therapeutic potential, and optimizing treatment strategies tailored to individual patients, and through interdisciplinary collaborations between computer scientists, biologists, and clinicians, the full potential of AI in accelerating the discovery and development of novel AMPs will be realized. Besides, with the continuous advancements in 3D/4D/5D/6D technology and its integration into bone scaffold materials, we anticipate remarkable progress in the field of regenerative medicine. This review summarizes relevant research on the optimal future for the treatment of infectious bone defects, provides guidance for future novel treatment strategies combining multi-dimensional printing with new antimicrobial agents, and provides a novel and effective solution to the current challenges in the field of bone regeneration.

Advanced Piezoelectric Materials, Devices, and Systems for Orthopedic Medicine

Harnessing the robust electromechanical couplings, piezoelectric materials not only enable efficient bio-energy harvesting, physiological sensing and actuating but also open enormous opportunities for therapeutic treatments through surface polarization directly interacting with electroactive cells, tissues, and organs. Known for its highly oriented and hierarchical structure, collagen in natural bones produces local electrical signals to stimulate osteoblasts and promote bone formation, inspiring the application of piezoelectric materials in orthopedic medicine. Recent studies showed that piezoelectricity can impact microenvironments by regulating molecular sensors including ion channels, cytoskeletal elements, cell adhesion proteins, and other signaling pathways. This review thus focuses on discussing the pioneering applications of piezoelectricity in the diagnosis and treatment of orthopedic diseases, aiming to offer valuable insights for advancing next-generation medical technologies. Beginning with an introduction to the principles of piezoelectricity and various piezoelectric materials, this review paper delves into the mechanisms through which piezoelectric materials accelerated osteogenesis. A comprehensive overview of piezoelectric materials, devices, and systems enhancing bone tissue repair, alleviating inflammation at infection sites, and monitoring bone health is then provided, respectively. Finally, the major challenges faced by applications of piezoelectricity in orthopedic conditions are thoroughly discussed, along with a critical outlook on future development trends.

Biomimetic Mineralized Organic–Inorganic Hybrid Scaffolds From Microfluidic 3D Printing for Bone Repair

Bone defect is a common clinical orthopedic disease. The trend in this field is to develop tissue engineering scaffolds with appropriately designed components and structures for bone repair. Herein, inspired by the organic and inorganic components of bone matrix and the natural biomineralization mechanism, a MgSiO3@Fe3O4 nanoparticle composite polycaprolactone (PCL) hybrid mineralized scaffold for bone repair is developed by microfluidic 3D printing. The incorporation of MgSiO3@Fe3O4 within the PCL scaffold can effectively improve the bioactivity. In addition, a biomimetic mineralized layer is prepared on the surface of the scaffold, which endowed it with unique microstructural characteristics, enhanced cell adhesion and osteogenic activity, and thus improved the bone repair performance. Owing to these advantages, both in vivo and in vitro experiments have demonstrated that the designed scaffold has outstanding biocompatibility and bone repair performance. These features indicate that the organic–inorganic biomineralized hybrid scaffold can be a potential bone graft substitute for clinical bone repair.

Electrical Stimulation Therapy - Dedicated to the Perfect Plastic Repair

Tissue repair and reconstruction are a clinical difficulty. Bioelectricity has been identified as a critical factor in supporting tissue and cell viability during the repair process, presenting substantial potential for clinical application. This review delves into various sources of electrical stimulation and identifies appropriate electrode materials for clinical use. It also highlights the biological mechanisms of electrical stimulation at both the subcellular and cellular levels, elucidating how these interactions facilitate the repair and regeneration processes across different organs. Moreover, specific electrode materials and stimulation sources are outlined, detailing their impact on cellular activity. The future development trends are projected from two perspectives: the optimization of equipment performance and the fulfillment of clinical demands, focusing on the feasibility, safety, and cost-effectiveness of technologies.

Low Voltage-Enhanced Mechano-Bactericidal Biopatch

Mechano-bactericidal strategies represent a safe and sustainable method for preventing microbial contamination in the postantibiotic era. However, their effectiveness against Gram-positive bacteria (≤55%) is still limited due to the thick peptidoglycan layer in their cell walls. Herein, an intelligent biomimetic nanopillared biopatch is developed. It is assisted by low-voltage (8 V) electrical stimulation from TENG and significantly enhances antibacterial efficacy (>99%) against three types of stubborn Gram-positive bacteria. These collaborative antibacterial behaviors are solely based on purely physical actions, thus avoiding the risk of triggering bacterial resistance. Moreover, the slight mechanical energy generated by human physiological activities is converted into a power source, exhibiting energy-efficient, eco-friendly, and sustainable features. The conductive hydrogel in the biopatch can also act as an intelligent temperature sensor, monitoring, and real-time assessment of wound conditions. This intelligent biopatch holds immense potential for efficient healing and safe management of both acute and chronic wound infections.

Advanced Dielectric Materials for Triboelectric Nanogenerators: Principles, Methods, and Applications

Triboelectric nanogenerator (TENG) manifests distinct advantages such as multiple structural selectivity, diverse selection of materials, environmental adaptability, low cost, and remarkable conversion efficiency, which becomes a promising technology for micro-nano energy harvesting and self-powered sensing. Tribo-dielectric materials are the fundamental and core components for high-performance TENGs. In particular, the charge generation, dissipation, storage, migration of the dielectrics, and dynamic equilibrium behaviors determine the overall performance. Herein, a comprehensive summary is presented to elucidate the dielectric charge transport mechanism and tribo-dielectric material modification principle toward high-performance TENGs. The contact electrification and charge transport mechanism of dielectric materials is started first, followed by introducing the basic principle and dielectric materials of TENGs. Subsequently, modification mechanisms and strategies for high-performance tribo-dielectric materials are highlighted regarding physical/chemical, surface/bulk, dielectric coupling, and structure optimization. Furthermore, representative applications of dielectric materials based TENGs as power sources, self-powered sensors are demonstrated. The existing challenges and promising potential opportunities for advanced tribo-dielectric materials are outlined, guiding the design, fabrication, and applications of tribo-dielectric materials.

Emerging Piezoelectric Metamaterials for Biomedical Applications

Emerging piezoelectric metamaterials hold immense promise for biomedical applications by merging the intrinsic electrical properties of piezoelectricity with the precise architecture of metamaterials. This review provides a comprehensive overview of various piezoelectric materials- such as molecular crystals, ceramics, and polymers-known for their exceptional piezoelectric performance and biocompatibility. We explore the advanced engineering approaches, including molecular design, supramolecular packing, and 3D assembly, which enable the customization of piezoelectric properties for targeted biomedical applications. Particular attention is given to the pivotal role of metamaterial structuring in the development of 0D spheres, 1D fibers and tubes, 2D films, and 3D scaffolds. Key biomedical applications, including tissue engineering, drug delivery, wound healing, and biosensing, are discussed through illustrative examples. Finally, the article addresses critical challenges and future directions, aiming to drive further innovations in piezoelectric biomaterials for next-generation healthcare technologies.

Implantable Self-Powered Systems for Electrical Stimulation Medical Devices

With the integration of bioelectronics and materials science, implantable self-powered systems for electrical stimulation medical devices have emerged as an innovative therapeutic approach, garnering significant attention in medical research. These devices achieve self-powering through integrated energy conversion modules, such as triboelectric nanogenerators (TENGs) and piezoelectric nanogenerators (PENGs), significantly enhancing the portability and long-term efficacy of therapeutic equipment. This review delves into the design strategies and clinical applications of implantable self-powered systems, encompassing the design and optimization of energy harvesting modules, the selection and fabrication of adaptable electrode materials, innovations in systematic design strategies, and the extensive utilization of implantable self-powered systems in biological therapies, including the treatment of neurological disorders, tissue regeneration engineering, drug delivery, and tumor therapy. Through a comprehensive analysis of the latest research progress, technical challenges, and future directions in these areas, this paper aims to provide valuable insights and inspiration for further research and clinical applications of implantable self-powered systems.

3D-Printed Shape Memory and Piezoelectric Bifunctional Thermoplastic Polyurethane/Polyvinylidene Fluoride Porous Composite Scaffold for Bone Regeneration

Physical stimulations such as mechanical and electric stimulation can continuously work on bone defect locations to maintain and enhance cell activity, and it has become a hotspot for research in the field of bone repair. Herein, bifunctional porous composite scaffolds with shape memory and piezoelectric functions were fabricated using thermoplastic polyurethane (TPU) and poly(vinylidene fluoride) through triply periodic minimal surfaces design and selective laser sintering technology. Thereinto, the shape fixity ratio and recovery ratio of the composite scaffold reached 98.6% and 81.2%, respectively, showing excellent shape memory functions. More importantly, its piezoelectric coefficient (d33 = 2.47 pC/N) is close to the piezoelectric constant of bone tissue (d33 = 0.7-2.3 pC/N), and the voltage released during the compression process can reach 0.5 V. Furthermore, cyclic compression experiments showed that the strength of composite scaffold was up to 8.3 times compared with the TPU scaffold. Besides, the composite scaffold showed excellent cytocompatibility. In conclusion, the composite scaffold is expected to continuously generate mechanical and electric stimulation due to shape memory and piezoelectric function, respectively, which provide an effective strategy for bone repair.

Augmenting osteoporotic bone regeneration through a hydrogel-based rejuvenating microenvironment

Osteoporotic bone defects pose a significant challenge for bone regeneration as they exhibit impaired healing capacity and delayed healing period. To address this issue, this study introduces a hydrogel that creates a rejuvenating microenvironment, thereby facilitating efficient bone repair during the initial two weeks following bone defect surgery. The hydrogel, named GelHFS, was created through host-guest polymerization of gelatin and acrylated β-cyclodextrin. Incorporation of the human fetal mesenchymal stem cell secretome (HFS) formed GelHFS hydrogel aimed at mimicking a rejuvenated stem cell niche. Our results demonstrated that GelHFS hydrogel promotes cell stellate spreading and osteogenic differentiation via integrin β1-induced focal adhesion pathway. Implantation of GelHFS hydrogel in an osteoporotic bone defect rat model recruited endogenous integrin β1-expressing cells and enhanced new bone formation and bone strength. Our findings reveal that GelHFS hydrogel provides a rejuvenating niche for endogenous MSCs and enhances bone regeneration in osteoporotic bone defect. These findings highlight the potential of GelHFS hydrogel as an effective therapeutic strategy for addressing challenging bone healing such as osteoporotic bone regeneration.

Unleashing the Potential of Electroactive Hybrid Biomaterials and Self-Powered Systems for Bone Therapeutics

The incidence of large bone defects caused by traumatic injury is increasing worldwide, and the tissue regeneration process requires a long recovery time due to limited self-healing capability. Endogenous bioelectrical phenomena have been well recognized as critical biophysical factors in bone remodeling and regeneration. Inspired by bioelectricity, electrical stimulation has been widely considered an external intervention to induce the osteogenic lineage of cells and enhance the synthesis of the extracellular matrix, thereby accelerating bone regeneration. With ongoing advances in biomaterials and energy-harvesting techniques, electroactive biomaterials and self-powered systems have been considered biomimetic approaches to ensure functional recovery by recapitulating the natural electrophysiological microenvironment of healthy bone tissue. In this review, we first introduce the role of bioelectricity and the endogenous electric field in bone tissue and summarize different techniques to electrically stimulate cells and tissue. Next, we highlight the latest progress in exploring electroactive hybrid biomaterials as well as self-powered systems such as triboelectric and piezoelectric-based nanogenerators and photovoltaic cell-based devices and their implementation in bone tissue engineering. Finally, we emphasize the significance of simulating the target tissue's electrophysiological microenvironment and propose the opportunities and challenges faced by electroactive hybrid biomaterials and self-powered bioelectronics for bone repair strategies.

Extending Dynamic Blind Interaction: Microgap Discharge-Induced Flexible Virtual Electrotactile Braille

Braille is an essential implement for the blind to communicate with outside, but traditional Braille is limited to a paper-based format that cannot directly provide real-time word information. In this work, a flexible virtual electrotactile Braille is proposed that can benefit the blind from blocked interaction. The Braille interface, S-shaped wires and a sphere electrode with a textile fingerstall integrated by silicone, offers flexibility and simultaneously generates the microgap through textile cracks, which achieves virtual electrotactile sensation by electrostatic discharge. Powered by a high-voltage triboelectric generator of 10.2 kV designed through the charge accumulation and induction strategy, the electrotactile stimulation is realized with a microgap discharge of only 40 μA current induced on the finger. A dynamic electrotactile Braille is finally assembled, controlled by a programmable relay array. The strategies of short circuit and voice reminder are employed, so that the recognition of dynamic Braille letters is realized with spatiotemporal electrotactile stimulation and high recognition accuracy. This virtual electrotactile Braille brings convenience for the blind to access the information world and illustrates its applications to promote virtual electrotactility in this special community.

Black phosphorus for bone regeneration: Mechanisms involved and influencing factors

BP has shown good potential for promoting bone regeneration. However, the understanding of the mechanisms of BP-enhanced bone regeneration is still limited. This review first summarizes the recent advances in applications of BP in bone regeneration. We further highlight the possibility that BP enhances bone regeneration by regulating the behavior of mesenchymal stem cells (MSCs), osteoblasts, vascular endothelial cells (VECs), and macrophages, mainly through the regulation of cytoskeletal remodeling, energy metabolism, oxidation resistance and surface adsorption properties, etc. In addition, moderating the physicochemical properties of BP (i.e., shape, size, and surface charge) can alter the effects of BP on bone regeneration. This review reveals the underlying mechanisms of BP-enhanced bone regeneration and provides strategies for further material design of BP-based materials for bone regeneration.

Self-Adhesive and Self-Sustainable Bioelectronic Patch for Physiological Feedback Electronic Modulation of Soft Organs

Bionic electrical stimulation (Bio-ES) aims to achieve personalized therapy and proprioceptive adaptation by mimicking natural neural signatures of the body, while current Bio-ES devices are reliant on complex sensing and computational simulation systems, thus often limited by the low-fidelity of simulated electrical signals, and failure of interface information interaction due to the mechanical mismatch between soft tissues and rigid electrodes. Here, the study presents a flexible and ultrathin self-sustainable bioelectronic patch (Bio-patch), which can self-adhere to the lesion area of organs and generate bionic electrical signals synchronized vagal nerve envelope in situ to implement Bio-ES. It allows adaptive adjustment of intensity, frequency, and waveform of the Bio-ES to fully meet personalized needs of tissue regeneration based on real-time feedback from the vagal neural controlled organs. With this foundation, the Bio-patch can effectively intervene with excessive fibrosis and microvascular stasis during the natural healing process by regulating the polarization time of macrophages, promoting the reconstruction of the tissue-engineered structure, and accelerating the repair of damaged liver and kidney. This work develops a practical approach to realize biomimetic electronic modulation of the growth and development of soft organs only using a multifunctional Bio-patch, which establishes a new paradigm for precise bioelectronic medicine.

Bioelectronics for electrical stimulation: materials, devices and biomedical applications

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

Effect of Silicon Nitride Coating on Titanium Surface: Biocompatibility and Antibacterial Properties

In recent years, with the advent of a super-aged society, lifelong dental care has gained increasing emphasis, and implant therapy for patients with an edentulous jaw has become a significant option. However, for implant therapy to be suitable for elderly patients with reduced regenerative and immunological capabilities, higher osteoconductive and antimicrobial properties are required on the implant surfaces. Silicon nitride, a non-oxide ceramic known for its excellent mechanical properties and biocompatibility, has demonstrated high potential for inducing hard tissue differentiation and exhibiting antibacterial properties. In this study, silicon nitride was deposited on pure titanium metal surfaces and evaluated for its biocompatibility and antibacterial properties. The findings indicate that silicon nitride improves the hydrophilicity of the material surface, enhancing the initial adhesion of rat bone marrow cells and promoting hard tissue differentiation. Additionally, the antibacterial properties were assessed using Staphylococcus aureus, revealing that the silicon nitride-coated surfaces exhibited significant antibacterial activity. Importantly, no cytotoxicity was observed, suggesting that silicon nitride-coated titanium could serve as a novel implant material.

Accelerated Bone Healing via Electrical Stimulation

Piezoelectric effect produces an electrical signal when stress is applied to the bone. When the integrity of the bone is destroyed, the biopotential within the defect site is reduced and several physiological responses are initiated to facilitate healing. During the healing of the bone defect, the bioelectric potential returns to normal levels. Treatment of fractures that exceed innate regenerative capacity or exhibit delayed healing requires surgical intervention for bone reconstruction. For bone defects that cannot heal on their own, exogenous electric fields are used to assist in treatment. This paper reviews the effects of exogenous electrical stimulation on bone healing, including osteogenesis, angiogenesis, reduction in inflammation and effects on the peripheral nervous system. This paper also reviews novel electrical stimulation methods, such as small power supplies and nanogenerators, that have emerged in recent years. Finally, the challenges and future trends of using electrical stimulation therapy for accelerating bone healing are discussed.

Methods to accelerate fracture healing - a narrative review from a clinical perspective

Bone regeneration is a complex pathophysiological process determined by molecular, cellular, and biomechanical factors, including immune cells and growth factors. Fracture healing usually takes several weeks to months, during which patients are frequently immobilized and unable to work. As immobilization is associated with negative health and socioeconomic effects, it would be desirable if fracture healing could be accelerated and the healing time shortened. However, interventions for this purpose are not yet part of current clinical treatment guidelines, and there has never been a comprehensive review specifically on this topic. Therefore, this narrative review provides an overview of the available clinical evidence on methods that accelerate fracture healing, with a focus on clinical applicability in healthy patients without bone disease. The most promising methods identified are the application of axial micromovement, electromagnetic stimulation with electromagnetic fields and direct electric currents, as well as the administration of growth factors and parathyroid hormone. Some interventions have been shown to reduce the healing time by up to 20 to 30%, potentially equivalent to several weeks. As a combination of methods could decrease the healing time even further than one method alone, especially if their mechanisms of action differ, clinical studies in human patients are needed to assess the individual and combined effects on healing progress. Studies are also necessary to determine the ideal settings for the interventions, i.e., optimal frequencies, intensities, and exposure times throughout the separate healing phases. More clinical research is also desirable to create an evidence base for clinical guidelines. To make it easier to conduct these investigations, the development of new methods that allow better quantification of fracture-healing progress and speed in human patients is needed.

Recent Progress in Implantable Drug Delivery Systems

In recent years, tremendous effort is devoted to developing platforms, such as implantable drug delivery systems (IDDSs), with temporally and spatially controlled drug release capabilities and improved adherence. IDDSs have multiple advantages: i) the timing and location of drug delivery can be controlled by patients using specific stimuli (light, sound, electricity, magnetism, etc.). Some intelligent "closed-loop" IDDS can even realize self-management without human participation. ii) IDDSs enable continuous and stable delivery of drugs over a long period (months to years) and iii) to administer drugs directly to the lesion, thereby helping reduce dosage and side effects. iv) IDDSs enable personalized drug delivery according to patient needs. The high demand for such systems has prompted scientists to make efforts to develop intelligent IDDS. In this review, several common stimulus-responsive mechanisms including endogenous (e.g., pH, reactive oxygen species, proteins, etc.) and exogenous stimuli (e.g., light, sound, electricity, magnetism, etc.), are given in detail. Besides, several types of IDDS reported in recent years are reviewed, including various stimulus-responsive systems based on the above mechanisms, radio frequency-controlled IDDS, "closed-loop" IDDS, self-powered IDDS, etc. Finally, the advantages and disadvantages of various IDDS, bottleneck problems, and possible solutions are analyzed to provide directions for subsequent research.