Concentrically Integrative Bioassembly of a Three-Dimensional Black Phosphorus Nanoscaffold for Restoring Neurogenesis, Angiogenesis, and Immune Homeostasis

Hydrogel system with growth cone-targeted hydroxyapatite nanorods: Regulating calcium signals for peripheral nerve injury repair

Calcium (Ca²⁺) regulation assumes a critical role in the repair course of peripheral nerve injury (PNI). However, effective calcium sources capable of providing sustained Ca²⁺ signals to promote growth cone extension remain limited. Herein, the coupling of biotinylated dextran amine (BDA) to amine-functionalized hydroxyapatite nanorods (nHAP-NH2) remarkably promoted and maintained the extension of growth cones throughout nerve regeneration. Therefore, a newly developed therapeutic system for PNI was constructed based on a hydrogel (Gel) loaded with BDA-nHAP (nHAP-NH2 with surface modification of BDA) and vascular endothelial growth factor (VEGF). The sustained-release BDA-nHAP has the potential to continuously and targetedly increase the Ca2+ levels within the growth cone, and further boost neurite outgrowth by modulating the PI3K-PAK and MAPK signalling pathways. Moreover, VEGF can significantly promote angiogenesis in the early stage of nerve repair, which is critical for optimizing the functional efficacy of BDA-nHAP in enhancing neurogenesis. Thus, this innovative integrated therapeutic system with neurogenesis and angiogenesis capabilities may offer a new solution for achieving high-quality functional recovery from PNI. STATEMENT OF SIGNIFICANCE: For PNI, there remains a scarcity of effective calcium sources capable of providing sustained Ca²⁺ signals within the growth cone to enhance its extension. Herein, a newly developed therapeutic system for PNI was constructed based on a Gel loaded with BDA-nHAP and VEGF. The sustained-release BDA-nHAP has the potential to continuously and targetedly increase the Ca2+ levels within the growth cone, and further boost neurite outgrowth throughout the whole process of nerve regeneration. Moreover, VEGF can significantly promote angiogenesis in the early stage of nerve repair, which is critical for optimizing the functional efficacy of BDA-nHAP in enhancing neurogenesis. Thus, this innovative therapeutic system may offer a new solution for achieving high-quality functional recovery from PNI.

Black phosphorus nanosheets fortified with catalase to enhance Schwann cell responses for neural repair

Peripheral nerve injuries (PNI) present a significant clinical challenge due to the complex cellular and molecular activities that hinder functional recovery. Schwann cells (SCs), the principal glial cells in the peripheral nervous system, play a vital role in neural repair by transitioning into a repairing phenotype capable of supporting axonal regrowth. However, these regenerative properties fade over time, leading to poor clinical outcomes. To address this issue, we engineered a black phosphorus nanosheet (BPNS) functionalized with catalase (BPNS@CAT) to modulate SC activity and enhance nerve regeneration. In vitro experiments demonstrated that BPNS@CAT reduced ROS levels, regulated the angiogenic and immunomodulatory functions of SCs. Mechanistically, we identified that BPNS@CAT activated the JAK/STAT pathway, which is crucial for SC-mediated repair processes. To validate its therapeutic potential, a BPNS@CAT-GelMA/PCL hydrogel scaffold was fabricated and applied in a rat sciatic nerve-crush model. The scaffold enhanced axonal regeneration, restored nerve function, and improved sensory, motor, and emotional behaviors. Our study broadens the range of BPNS applications in SC-based nerve repair and pave the way for future applications of BPNS in translational medicine.

Bioactive Inorganic Materials for Innervated Multi-Tissue Regeneration

Tissue engineering aims to repair damaged tissues with physiological functions recovery. Although several therapeutic strategies are there for tissue regeneration, the functional recovery of regenerated tissues still poses significant challenges due to the lack of concerns of tissue innervation. Design rationale of multifunctional biomaterials with both tissue-induction and neural induction activities shows great potential for functional tissue regeneration. Recently, the research and application of inorganic biomaterials attracts increasing attention in innervated multi-tissue regeneration, such as central nerves, bone, and skin, because of its superior tunable chemical composition, topographical structures, and physiochemical properties. More importantly, inorganic biomaterials are easily combined with other organic materials, biological factors, and external stimuli to enhance their therapeutic effects. This review presents a comprehensive overview of recent advancements of inorganic biomaterials for innervated multi-tissue regeneration. It begins with introducing classification and properties of typical inorganic biomaterials and design rationale of inorganic-based material composites. Then, recent progresses of inorganic biomaterials in regenerating various nerves and nerve-innervated tissues with functional recovery are systematically reviewed. Finally, the existing challenges and future perspectives are proposed. This review may pave the way for the direction of inorganic biomaterials and offers a new strategy for tissue regeneration in combination of innervation.

Prospects of black phosphorus nanosheets in the treatment of peri-implantitis

Peri-implantitis represents an inflammatory condition characterized by the presence of plaque-related soft and hard tissue damage surrounding dental implants, often resulting in progressive alveolar bone loss and, ultimately, implant failure. Black phosphorus (BP), a novel two-dimensional (2D) material that has recently emerged in the biomedical field, has attracted increasing attention due to its unique osteogenic properties and exceptional antibacterial and antioxidant characteristics. Additionally, its outstanding biomedical attributes enhance angiogenesis and nerve regeneration. Compared to other biomaterials, its high specific surface area, high photothermal conversion efficiency, and complete biodegradability make BP a promising candidate for treating infection-related bone defects. This article reviews the biological properties of BP nanosheets (BPNSs) and discusses their potential applications in the context of peri-implantitis, aiming to provide fresh insights for future research and applications of BPNS.

Biofluid-Permeable and Erosion-Resistant Wireless Neural-Electronic Interfaces for Neurohomeostasis Modulation

Neural-electronic interfaces through delivering electroceuticals to lesions and modulating pathological endogenous electrical environments offer exciting opportunities to treat drug-refractory neurological disorders. Such an interface should ideally be compatible with the neural tissue and aggressive biofluid environment. Unfortunately, no interface specifically designed for the biofluid environments is available so far; instead, simply stacking an encapsulation layer on silicon-based substrates makes them susceptible to biofluid leakage, device malfunction, and foreign-body reactions. Here, we developed a biofluid-permeable and erosion-resistant wireless neural-electronic interface (BNEI) that is composed of a flexible 3D interconnected poly(l-lactide) fibrous network with a dense and axially aligned piezoelectrical molecular chain arrangement architecture. The organized molecular chain structure enhances the tortuous pathway and longitudinal piezoelectric coefficient of poly(l-lactide) fibers, improves their water barrier properties, and enables efficient conversion of low-intensity acoustic vibrations transmitted in biofluids into electrical signals, achieving long-term stable and wireless neuromodulation. A 3-month clinical trial demonstrated that the BNEI can effectively accelerate the pathological cascade in peripheral neuropathy for nerve regeneration and transcranially modulate cerebellar-cerebral circuit dynamics, suppressing seizures in temporal lobe epilepsy. The BNEI can be a clinically scalable approach for wireless neuromodulation that is broadly applicable to the modulation of neurohomeostasis in both the peripheral and central nervous systems.

Mesoporous Prussian blue nanoparticle neuroconduit for the biological therapy targeting oxidative stress reduction, inflammation inhibition, and nerve regeneration

The applications of nanomaterials in regenerative medicine encompass a broad spectrum. The functional nanomaterials, such as Prussian blue and its derivative nanoparticles, exhibit potent anti-inflammatory and antioxidant properties. By combining it with the corresponding scaffold carrier, the fusion of nanomaterials and biotherapy can be achieved, thereby providing a potential avenue for clinical treatment. The present study demonstrates the fabrication of a Mesoporous Prussian blue nanoparticles (MPBN) functionalized Inverse Opal Film (IOF) neuroconduit for peripheral nerve repair through reverse replication and freeze-drying techniques. The binding of MPBN to the neuroconduit can effectively decreasing reactive oxygen species and inflammatory factors in the vicinity of the residual nerve, thereby providing protective effects on the damaged nerve. Furthermore, comprehensive behavioral, electrophysiological, and pathological analyses unequivocally substantiate the efficacy of MPBN in increasing nerve structure regeneration and ameliorating denervation-induced myopathy. Moreover, MPBN enhances the antioxidant capacity of Schwann cells by activating the AMPK/SIRT1/PGC-1 pathway. The findings suggest that MPBN, a biocompatible nanoparticle, can safeguard damaged nerves by optimizing the microenvironment surrounding nerve cells and augmenting the antioxidant capacity of nerve cells, thereby facilitating nerve regeneration and repair. This also establishes a theoretical foundation for exploring the integration and clinical translation between nanomaterials and biotherapy.

Skeletal interoception and prospective application in biomaterials for bone regeneration

Accumulating research has shed light on the significance of skeletal interoception, in maintaining physiological and metabolic homeostasis related to bone health. This review provides a comprehensive analysis of how skeletal interoception influences bone homeostasis, delving into the complex interplay between the nervous system and skeletal system. One key focus of the review is the role of various factors such as prostaglandin E2 (PGE2) in skeletal health via skeletal interoception. It explores how nerves innervating the bone tissue communicate with the central nervous system to regulate bone remodeling, a process critical for maintaining bone strength and integrity. Additionally, the review highlights the advancements in biomaterials designed to utilize skeletal interoception for enhancing bone regeneration and treatment of bone disorders. These biomaterials, tailored to interact with the body's interoceptive pathways, are positioned at the forefront of innovative treatments for conditions like osteoporosis and fractures. They represent a convergence of bioengineering, neuroscience, and orthopedics, aiming to create more efficient and targeted therapies for bone-related disorders. In conclusion, the review underscores the importance of skeletal interoception in physiological regulation and its potential in developing more effective therapies for bone regeneration. It emphasizes the need for further research to fully understand the mechanisms of skeletal interoception and to harness its therapeutic potential fully.

Microenvironment-responsive nanomedicines: a promising direction for tissue regeneration

Severe tissue defects present formidable challenges to human health, persisting as major contributors to mortality rates. The complex pathological microenvironment, particularly the disrupted immune landscape within these defects, poses substantial hurdles to existing tissue regeneration strategies. However, the emergence of nanobiotechnology has opened a new direction in immunomodulatory nanomedicine, providing encouraging prospects for tissue regeneration and restoration. This review aims to gather recent advances in immunomodulatory nanomedicine to foster tissue regeneration. We begin by elucidating the distinctive features of the local immune microenvironment within defective tissues and its crucial role in tissue regeneration. Subsequently, we explore the design and functional properties of immunomodulatory nanosystems. Finally, we address the challenges and prospects of clinical translation in nanomedicine development, aiming to propose a potent approach to enhance tissue regeneration through synergistic immune modulation and nanomedicine integration.

An injectable thermosensitive pluronic F127 loaded-nanohydroxyapatite / Polydopamine for promoting sciatic nerve repair after crush injury

Peripheral nerve injury (PNI) remains an urgent issue due to its huge financial burden and high rate of disability. Here, an injectable HAP/PDA thermosensitive pluronic F-127 (PF-127) hydrogel is proposed for peripheral nerve repair. We investigated the surface characteristics of HAP/PDA and evaluated biocompatibility, cellular proliferation, differentiation, and apoptosis in vitro. After injecting the hydrogel into the injured site of rats, we recorded the recovery of motor function and judged the degree of nerves through electrophysiological and morphological changes. The hydrogel was found to accelerate the nerve regeneration. Collectively, the HAP/PDA thermosensitive PF-127 hydrogel has potential in promoting sciatic nerve repair.

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.

Advanced nerve regeneration enabled by neural conformal electronic stimulators enhancing mitochondrial transport

Addressing peripheral nerve defects remains a significant challenge in regenerative neurobiology. Autografts emerged as the gold-standard management, however, are hindered by limited availability and potential neuroma formation. Numerous recent studies report the potential of wireless electronic system for nerve defects repair. Unfortunately, few has met clinical needs for inadequate electrode precision, poor nerve entrapment and insufficient bioactivity of the matrix material. Herein, we present an advanced wireless electrical nerve stimulator, based on water-responsive self-curling silk membrane with excellent bioabsorbable and biocompatible properties. We constructed a unique bilayer structure with an oriented pre-stretched inner layer and a general silk membrane as outer layer. After wetting, the simultaneous contraction of inner layer and expansion of outer layer achieved controllable super-contraction from 2D flat surface to 3D structural reconfiguration. It enables shape-adaptive wrapping to cover around nerves, overcomes the technical obstacle of preparing electrodes on the inner wall of the conduit, and prevents electrode breakage caused by material expansion in water. The use of fork capacitor-like metal interface increases the contact points between the metal and the regenerating nerve, solving the challenge of inefficient and rough electrical stimulation methods in the past. Newly developed electronic stimulator is effective in restoring 10 mm rat sciatic nerve defects comparable to autologous grafts. The underlying mechanism involves that electric stimulation enhances anterograde mitochondrial transport to match energy demands. This newly introduced device thereby demonstrated the potential as a viable and efficacious alternative to autografts for enhancing peripheral nerve repair and functional recovery.

Nerve Regeneration Potential of Antioxidant-Modified Black Phosphorus Quantum Dots in Peripheral Nerve Injury

Peripheral nerve injury is a major societal concern. Black phosphorus (BP) has inherent advantages over cell-based therapies in regenerative medicine. However, controlling spontaneous degradation and size-dependent cytotoxicity remains challenging and poses difficulties for clinical translation. In this study, we constructed zero-dimensional BP quantum dots (QDs) modified with antioxidant β-carotene and comprehensively investigated them in Schwann cells (SCs) to elucidate their potential for peripheral nerve repair. In vitro experiments demonstrated that BPQD@β-carotene has an inappreciable toxicity and good biocompatibility, favoring neural regrowth, angiogenesis, and inflammatory regulation of SCs. Furthermore, the PI3K/Akt and Ras/ERK1/2 signaling pathways were activated in SCs at the genetic, protein, and metabolite levels. The BPQD@β-carotene-embedded GelMA/PEGDA scaffold enhanced functional recovery by promoting axon remyelination and regeneration and facilitating intraneural angiogenesis in peripheral nerve injury models of rats and beagle dogs. These results contribute to advancing knowledge of BP nanomaterials in tissue regeneration and show significant potential for application in translational medicine.

Applications of 2D Nanomaterials in Neural Interface

Neural interfaces are crucial conduits between neural tissues and external devices, enabling the recording and modulation of neural activity. However, with increasing demand, simple neural interfaces are no longer adequate to meet the requirements for precision, functionality, and safety. There are three main challenges in fabricating advanced neural interfaces: sensitivity, heat management, and biocompatibility. The electrical, chemical, and optical properties of 2D nanomaterials enhance the sensitivity of various types of neural interfaces, while the newly developed interfaces do not exhibit adverse reactions in terms of heat management and biocompatibility. Additionally, 2D nanomaterials can further improve the functionality of these interfaces, including magnetic resonance imaging (MRI) compatibility, stretchability, and drug delivery. In this review, we examine the recent applications of 2D nanomaterials in neural interfaces, focusing on their contributions to enhancing performance and functionality. Finally, we summarize the advantages and disadvantages of these nanomaterials, analyze the importance of biocompatibility testing for 2D nanomaterials, and propose that improving and developing composite material structures to enhance interface performance will continue to lead the forefront of this field.

Gelatin‑sodium alginate composite hydrogel doped with black phosphorus@ZnO heterojunction for cutaneous wound healing with antibacterial, immunomodulatory, and angiogenic properties

Hydrogels with novel antimicrobial properties and accelerated wound healing are of great interest in the field of wound dressings because they not only prevent bacterial infections but also fulfill the essential needs of wound healing. In this study, multifunctional hydrogel dressings consisting of black phosphorus nanosheets(BPNS) surface-modified Zinc oxide (BP@ZnO heterojunction) based on gelatin (Gel), sodium alginate (SA), glutamine transferase (mTG), and calcium ions with a three-dimensional crosslinked network were prepared. The BP@ZnO-Gel/SA hydrogel has excellent mechanical properties, hemocompatibility (hemolysis rate: 3.29 %), swelling rate(832.8 ± 19.2 %), cytocompatibility, photothermal and photodynamic antibacterial properties(Sterilization rate: 96.4 ± 3.3 %). In addition, the hydrogel accelerates wound healing by promoting cell migration, immune regulation and angiogenesis. Thus, this hydrogel achieves the triple effect of antimicrobial, immunomodulation and angiogenesis, and is a tissue engineering strategy with great potential.

Strategies of functionalized GelMA-based bioinks for bone regeneration: Recent advances and future perspectives

Gelatin methacryloyl (GelMA) hydrogels is a widely used bioink because of its good biological properties and tunable physicochemical properties, which has been widely used in a variety of tissue engineering and tissue regeneration. However, pure GelMA is limited by the weak mechanical strength and the lack of continuous osteogenic induction environment, which is difficult to meet the needs of bone repair. Moreover, GelMA hydrogels are unable to respond to complex stimuli and therefore are unable to adapt to physiological and pathological microenvironments. This review focused on the functionalization strategies of GelMA hydrogel based bioinks for bone regeneration. The synthesis process of GelMA hydrogel was described in details, and various functional methods to meet the requirements of bone regeneration, including mechanical strength, porosity, vascularization, osteogenic differentiation, and immunoregulation for patient specific repair, etc. In addition, the response strategies of smart GelMA-based bioinks to external physical stimulation and internal pathological microenvironment stimulation, as well as the functionalization strategies of GelMA hydrogel to achieve both disease treatment and bone regeneration in the presence of various common diseases (such as inflammation, infection, tumor) are also briefly reviewed. Finally, we emphasized the current challenges and possible exploration directions of GelMA-based bioinks for bone regeneration.

Multilevel neurium-mimetic individualized graft via additive manufacturing for efficient tissue repair

Complicated peripheral nerve injuries or defects, especially at branching sites, remain a prominent clinical challenge after the application of different treatment strategies. Current nerve grafts fail to match the expected shape and size for delicate and precise branched nerve repair on a case-by-case basis, and there is a lack of geometrical and microscale regenerative navigation. In this study, we develop a sugar painting-inspired individualized multilevel epi-/peri-/endoneurium-mimetic device (SpinMed) to customize natural cues, featuring a selectively protective outer sheath and an instructive core, to support rapid vascular reconstruction and consequent efficient neurite extension along the defect area. The biomimetic perineurium dictates host-guest crosslinking in which new vessels secrete multimerin 1 binding to the fibroin filler surface as an anchor, contributing to the biological endoneurium that promotes Schwann cell homing and remyelination. SpinMed implantation into rat sciatic nerve defects yields a satisfactory outcome in terms of structural reconstruction, with sensory and locomotive function restoration. We further customize SpinMed grafts based on anatomy and digital imaging, achieving rapid repair of the nerve trunk and branches superior to that achieved by autografts and decellularized grafts in a specific beagle nerve defect model, with reliable biosafety. Overall, this intelligent art-inspired biomimetic design offers a facile way to customize sophisticated high-performance nerve grafts and holds great potential for application in translational regenerative medicine.

Injectable, Electroconductive, Free Radical Scavenging Silk Fibroin/Black Phosphorus/Glycyrrhizic Acid Nanocomposite Hydrogel for Enhancing Spinal Cord Repair

Spinal cord injury (SCI) often leads to a severe permanent disability. A poor inflammatory microenvironment and nerve electric signal conduction block are the main reasons for difficulty in spinal cord nerve regeneration. In this study, black phosphorus (BP) and glycyrrhizic acid (GA) are integrated into methacrylate-modified silk fibroin (SF) to construct a bifunctional injectable hydrogel (SF/BP/GA) with appropriate conductivity and the ability to inhibit inflammation to promote neuronal regeneration after SCI. This work discovers that the SF/BP/GA hydrogel can reduce the oxidative damage mediated by oxygen free radicals, promote the polarization of macrophages toward the anti-inflammatory M2 phenotype, reduce the expression of inflammatory factors, and improve the inflammatory microenvironment. Moreover, it induces neural stem cell (NSC) differentiation and neurosphere formation, restores signal conduction at the SCI site in vivo, and ameliorates motor function in mice with spinal cord hemisection, revealing a significant neural repair effect. An injectable, electroconductive, free-radical-scavenging hydrogel is a promising therapeutic strategy for SCI repair.

Chiral MoS2@BC fibrous membranes selectively promote peripheral nerve regeneration

BACKGROUND

Molybdenum disulfide (MoS2) has excellent physical and chemical properties. Further, chiral MoS2 (CMS) exhibits excellent chiroptical and enantioselective effects, and the enantioselective properties of CMS have been studied for the treatment of neurodegenerative diseases. Intriguingly, left- and right-handed materials have different effects on promoting the differentiation of neural stem cells into neurons. However, the effect of the enantioselectivity of chiral materials on peripheral nerve regeneration remains unclear.

METHODS

In this study, CMS@bacterial cellulose (BC) scaffolds were fabricated using a hydrothermal approach. The CMS@BC films synthesized with L-2-amino-3-phenyl-1-propanol was defined as L-CMS. The CMS@BC films synthesized with D-2-amino-3-phenyl-1-propanol was defined as D-CMS. The biocompatibility of CMS@BC scaffolds and their effect on Schwann cells (SCs) were validated by cellular experiments. In addition, these scaffolds were implanted in rat sciatic nerve defect sites for three months.

RESULTS

These chiral scaffolds displayed high hydrophilicity, good mechanical properties, and low cytotoxicity. Further, we found that the L-CMS scaffolds were superior to the D-CMS scaffolds in promoting SCs proliferation. After three months, the scaffolds showed good biocompatibility in vivo, and the nerve conducting velocities of the L-CMS and D-CMS scaffolds were 51.2 m/s and 26.8 m/s, respectively. The L-CMS scaffolds showed a better regenerative effect than the D-CMS scaffolds. Similarly, the sciatic nerve function index and effects on the motor and electrophysiological functions were higher for the L-CMS scaffolds than the D-CMS scaffolds. Finally, the axon diameter and myelin sheath thickness of the regenerated nerves were improved in the L-CMS group.

CONCLUSION

We found that the CMS@BC can promote peripheral nerve regeneration, and in general, the L-CMS group exhibited superior repair performance. Overall, the findings of this study reveal that CMS@BC can be used as a chiral nanomaterial nerve scaffold for peripheral nerve repair.

Multifunctional Biodegradable Conductive Hydrogel Regulating Microenvironment for Stem Cell Therapy Enhances the Nerve Tissue Repair

The nerve guidance conduits incorporated with stem cells, which can differentiate into the Schwann cells (SCs) to facilitate myelination, shows great promise for repairing the severe peripheral nerve injury. The innovation of advanced hydrogel materials encapsulating stem cells, is highly demanded for generating supportive scaffolds and adaptive microenvironment for nerve regeneration. Herein, this work demonstrates a novel strategy in regulating regenerative microenvironment for peripheral nerve repair with a biodegradable conductive hydrogel scaffold, which can offer multifunctional capabilities in immune regulation, enhancing angiogenesis, driving SCs differentiation, and promoting axon regrowth. The biodegradable conductive hydrogel is constructed by incorporation of polydopamine-modified silicon phosphorus (SiP@PDA) nanosheets into a mixture of methacryloyl gelatin and decellularized extracellular matrix (GelMA/ECM). The biomimetic electrical microenvironment performs an efficacious strategy to facilitate macrophage polarization toward a pro-healing phenotype (M2), meanwhile the conductive hydrogel supports vascularization in regenerated tissue through sustained Si element release. Furthermore, the MSCs 3D-cultured in GelMA/ECM-SiP@PDA conductive hydrogel exhibits significantly increased expression of genes associated with SC-like cell differentiation, thus facilitating the myelination and axonal regeneration. Collectively, both the in vitro and in vivo studies demonstrates that the rationally designed biodegradable multifunctional hydrogel significantly enhances nerve tissues repair.

Progress in the development of piezoelectric biomaterials for tissue remodeling

Piezoelectric biomaterials have demonstrated significant potential in the past few decades to heal damaged tissue and restore cellular functionalities. Herein, we discuss the role of bioelectricity in tissue remodeling and explore ways to mimic such tissue-like properties in synthetic biomaterials. In the past decade, biomedical engineers have adopted emerging functional biomaterials-based tissue engineering approaches using innovative bioelectronic stimulation protocols based on dynamic stimuli to direct cellular activation, proliferation, and differentiation on engineered biomaterial constructs. The primary focus of this review is to discuss the concepts of piezoelectric energy harvesting, piezoelectric materials, and their application in soft (skin and neural) and hard (dental and bone) tissue regeneration. While discussing the prospective applications as an engineered tissue, an important distinction has been made between piezoceramics, piezopolymers, and their composites. The superiority of piezopolymers over piezoceramics to circumvent issues such as stiffness mismatch, biocompatibility, and biodegradability are highlighted. We aim to provide a comprehensive review of the field and identify opportunities for the future to develop clinically relevant and state-of-the-art biomaterials for personalized and remote health care.

Black Phosphorus-Based Dynamic Self-Healing Hydrogel to Integrate Demineralized Bone Matrix and Noggin-Targeting siRNA for Synergistic Osteogenesis

Although a demineralized bone matrix (DBM) is often used as an alternative to an autologous bone graft, its clinical application is still hampered by easy dispersion of DBM particles and insufficient osteoinductivity in the defect site. Herein, we designed a self-healing hydrogel for DBM that can rapidly restore its structural integrity after damage based on amino-rich black phosphorus (BP) nanosheets and aldehyde-functionalized hyaluronic acid (AHA). Given the increased expression of bone morphogenetic protein (BMP) antagonists by DBM stimulation, the osteogenic potency of DBM in the hydrogel carrier was further enhanced by abrogating the BMP antagonism. The BP/AHA hydrogel provided dynamic polymer-nanosheet networks that combine injectability, modability, and physical stability with high DBM loading, where the BP nanosheets served as osteogenic cross-linkers to promote biomineralization and deliver siRNA to suppress undesirable expression of BMP antagonist noggin by DBM. As a result, the BP/AHA hydrogel integrated with DBM and noggin-targeting siRNA synergistically promoted osteogenic differentiation of mesenchymal stem cells by enhancing BMP/Smad signaling. This work demonstrates a promising strategy to improve the efficacy of bone regeneration using bone graft.

Advances in electroactive bioscaffolds for repairing spinal cord injury

Spinal cord injury (SCI) is a devastating neurological disorder, leading to loss of motor or somatosensory function, which is the most challenging worldwide medical problem. Re-establishment of intact neural circuits is the basis of spinal cord regeneration. Considering the crucial role of electrical signals in the nervous system, electroactive bioscaffolds have been widely developed for SCI repair. They can produce conductive pathways and a pro-regenerative microenvironment at the lesion site similar to that of the natural spinal cord, leading to neuronal regeneration and axonal growth, and functionally reactivating the damaged neural circuits. In this review, we first demonstrate the pathophysiological characteristics induced by SCI. Then, the crucial role of electrical signals in SCI repair is introduced. Based on a comprehensive analysis of these characteristics, recent advances in the electroactive bioscaffolds for SCI repair are summarized, focusing on both the conductive bioscaffolds and piezoelectric bioscaffolds, used independently or in combination with external electronic stimulation. Finally, thoughts on challenges and opportunities that may shape the future of bioscaffolds in SCI repair are concluded.

Black phosphorus, an advanced versatile nanoparticles of antitumor, antibacterial and bone regeneration for OS therapy

Osteosarcoma (OS) is the most common primary malignant bone tumor. In the clinic, usual strategies for OS treatment include surgery, chemotherapy, and radiation. However, all of these therapies have complications that cannot be ignored. Therefore, the search for better OS treatments is urgent. Black phosphorus (BP), a rising star of 2D inorganic nanoparticles, has shown excellent results in OS therapy due to its outstanding photothermal, photodynamic, biodegradable and biocompatible properties. This review aims to present current advances in the use of BP nanoparticles in OS therapy, including the synthesis of BP nanoparticles, properties of BP nanoparticles, types of BP nanoparticles, and modification strategies for BP nanoparticles. In addition, we have discussed comprehensively the application of BP in OS therapy, including single, dual, and multimodal synergistic OS therapies, as well as studies about bone regeneration and antibacterial properties. Finally, we have summarized the conclusions, limitations and perspectives of BP nanoparticles for OS therapy.

Improving osseointegration and antimicrobial properties of titanium implants with black phosphorus nanosheets-hydroxyapatite composite coatings for vascularized bone regeneration

For decades, titanium implants have shown impressive advantages in bone repair. However, the preparation of implants with excellent antimicrobial properties as well as better osseointegration ability remains difficult for clinical application. In this study, black phosphorus nanosheets (BPNSs) were doped into hydroxyapatite (HA) coatings using electrophoretic deposition. The coatings' surface morphology, roughness, water contact angle, photothermal properties, and antibacterial properties were investigated. The BP/HA coating exhibited a surface roughness of 59.1 nm, providing an ideal substrate for cell attachment and growth. The water contact angle on the BP/HA coating was measured to be approximately 8.55°, indicating its hydrophilic nature. The BPNSs demonstrated efficient photothermal conversion, with a temperature increase of 42.2°C under laser irradiation. The BP/HA composite coating exhibited a significant reduction in bacterial growth, with inhibition rates of 95.6% and 96.1% against Staphylococcus aureus and Escherichia coli. In addition, the cytocompatibility of the composite coating was evaluated by cell adhesion, CCK8 and AM/PI staining; the effect of the composite coating in promoting angiogenesis was assessed by scratch assay, transwell assay, and protein blotting; and the osteoinductivity of the composite coating was evaluated by alkaline phosphatase assay, alizarin red staining, and Western blot. The results showed that the BP/HA composite coating exhibited superior performance in promoting biological functions such as cell proliferation and adhesion, antibacterial activity, osteogenic differentiation, and angiogenesis, and had potential applications in vascularized bone regeneration.

Capacitive-Coupling-Responsive Hydrogel Scaffolds Offering Wireless In Situ Electrical Stimulation Promotes Nerve Regeneration

Electrical stimulation (ES) has shown beneficial effects in repairing injured tissues. However, current ES techniques that use tissue-traversing leads and bulky external power suppliers have significant limitations in translational medicine. Hence, exploring noninvasive in vivo ES to provide controllable electrical cues in tissue engineering is an imminent necessity. Herein, a conductive hydrogel with in situ electrical generation capability as a biodegradable regeneration scaffold and wireless ES platform for spinal cord injury (SCI) repair is demonstrated. When a soft insulated metal plate is placed on top of the injury site as a wireless power transmitter, the conductive hydrogel implanted at the injury site can serve as a wireless power receiver, and the capacitive coupling between the receiver and transmitter can generate an alternating current in the hydrogel scaffold owing to electrostatic induction effect. In a complete transection model of SCI rats, the implanted conductive hydrogels with capacitive-coupling in situ ES enhance functional recovery and neural tissue repair by promoting remyelination, accelerating axon regeneration, and facilitating endogenous neural stem cell differentiation. This facile wireless-powered electroactive-hydrogel strategy thus offers on-demand in vivo ES with an adjustable timeline, duration, and strength and holds great promise in translational medicine.

Advances in the Application of Black Phosphorus-Based Composite Biomedical Materials in the Field of Tissue Engineering

Black Phosphorus (BP) is a new semiconductor material with excellent biocompatibility, degradability, and optical and electrophysical properties. A growing number of studies show that BP has high potential applications in the biomedical field. This article aims to systematically review the research progress of BP composite medical materials in the field of tissue engineering, mining BP in bone regeneration, skin repair, nerve repair, inflammation, treatment methods, and the application mechanism. Furthermore, the paper discusses the shortcomings and future recommendations related to the development of BP. These shortcomings include stability, photothermal conversion capacity, preparation process, and other related issues. However, despite these challenges, the utilization of BP-based medical materials holds immense promise in revolutionizing the field of tissue repair.

Injectable ultrasound-powered bone-adhesive nanocomposite hydrogel for electrically accelerated irregular bone defect healing

The treatment of critical-size bone defects with irregular shapes remains a major challenge in the field of orthopedics. Bone implants with adaptability to complex morphological bone defects, bone-adhesive properties, and potent osteogenic capacity are necessary. Here, a shape-adaptive, highly bone-adhesive, and ultrasound-powered injectable nanocomposite hydrogel is developed via dynamic covalent crosslinking of amine-modified piezoelectric nanoparticles and biopolymer hydrogel networks for electrically accelerated bone healing. Depending on the inorganic-organic interaction between the amino-modified piezoelectric nanoparticles and the bio-adhesive hydrogel network, the bone adhesive strength of the prepared hydrogel exhibited an approximately 3-fold increase. In response to ultrasound radiation, the nanocomposite hydrogel could generate a controllable electrical output (-41.16 to 61.82 mV) to enhance the osteogenic effect in vitro and in vivo significantly. Rat critical-size calvarial defect repair validates accelerated bone healing. In addition, bioinformatics analysis reveals that the ultrasound-responsive nanocomposite hydrogel enhanced the osteogenic differentiation of bone mesenchymal stem cells by increasing calcium ion influx and up-regulating the PI3K/AKT and MEK/ERK signaling pathways. Overall, the present work reveals a novel wireless ultrasound-powered bone-adhesive nanocomposite hydrogel that broadens the therapeutic horizons for irregular bone defects.

Black Phosphorus Accelerates Bone Regeneration Based on Immunoregulation

A fundamental understanding of inflammation and tissue healing suggests that the precise regulation of the inflammatory phase, both in terms of location and timing, is crucial for bone regeneration. However, achieving the activation of early inflammation without causing chronic inflammation while facilitating quick inflammation regression to promote bone regeneration continues to pose challenges. This study reveals that black phosphorus (BP) accelerates bone regeneration by building an osteogenic immunological microenvironment. BP amplifies the acute pro-inflammatory response and promotes the secretion of anti-inflammatory factors to accelerate inflammation regression and tissue regeneration. Mechanistically, BP creates an osteoimmune-friendly microenvironment by stimulating macrophages to express interleukin 33 (IL-33), amplifying the inflammatory response at an early stage, and promoting the regression of inflammation. In addition, BP-mediated IL-33 expression directly promotes osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs), which further facilitates bone repair. To the knowledge, this is the first study to reveal the immunomodulatory potential of BP in bone regeneration through the regulation of both early-stage inflammatory responses and later-stage inflammation resolution, along with the associated molecular mechanisms. This discovery serves as a foundation for the clinical use of BP and is an efficient approach for managing the immune microenvironment during bone regeneration.

MXene and Xene: promising frontier beyond graphene in tissue engineering and regenerative medicine

The emergence of 2D nanomaterials (2D NMs), which was initiated by the isolation of graphene (G) in 2004, revolutionized various biomedical applications, including bioimaging and -sensing, drug delivery, and tissue engineering, owing to their unique physicochemical and biological properties. Building on the success of G, a novel class of monoelemental 2D NMs, known as Xenes, has recently emerged, offering distinct advantages in the fields of tissue engineering and regenerative medicine. In this review, we focus on the comparison of G and Xene materials for use in fabricating tissue engineering scaffolds. After a brief introduction to the basic physicochemical properties of these materials, recent representative studies are classified in terms of the engineered tissue, i.e., bone, cartilage, neural, muscle, and skin tissues. We analyze several methods of improving the clinical potential of Xene-laden scaffolds using state-of-the-art fabrication technologies and innovative biomaterials. Despite the considerable advantages of Xene materials, critical concerns, such as biocompatibility, biodistribution and regulatory challenges, should be considered. This review and collaborative efforts should advance the field of Xene-based tissue engineering and enable innovative, effective solutions for use in future tissue regeneration.

Ultrasonic neural regulation over two-dimensional graphene analog biomaterials: Enhanced PC12 cell differentiation under diverse ultrasond excitation

Two-dimensional (2D) biomaterials, with unique planar topology and quantum effect, have been widely recognized as a versatile nanoplatform for bioimaging, drug delivery and tissue engineering. However, during the complex application of nerve repair, in which inflammatory microenvironment control is imperative, the gentle manipulation and trigger of 2D biomaterials with inclusion and diversity is still challenging. Herein, inspired by the emerging clinical progress of ultrasound neuromodulation, we systematically studied ultrasound-excited 2D graphene analogues (graphene, graphene oxide, reduced graphene oxide (rGO) and carbon nitride) to explore their feasibility, accessibility, and adjustability for ultrasound-induced nerve repair in vitro. Quantitative observation of cell differentiation morphology demonstrates that PC12 cells added with rGO show the best compatibility and differentiation performance under the general ultrasound mode (0.5 w/cm2, 2 min/day) compared with graphene, graphene oxide and carbon nitride. Furthermore, the general condition can be improved by using a higher intensity of 0.7 w/cm2, but it cannot go up further. Later, ultrasonic frequency and duty cycle conditions were investigated to demonstrate the unique and remarkable inclusion and diversity of ultrasound over conventional electrical and surgical means. The pulse waveform with power of 1 MHz and duty cycle of 50 % may be even better, while the 3 MHz and 100 % duty cycle may not work. Overall, various graphene analog materials can be regarded as biosafe and accessible in both fundamental research and clinical ultrasound therapy, even for radiologists without material backgrounds. The enormous potential of diverse and personalized 2D biomaterials-based therapies can be expected to provide a new mode of ultrasound neuromodulation.

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

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

GelMA-based bioactive hydrogel scaffolds with multiple bone defect repair functions: therapeutic strategies and recent advances

Currently, the clinical treatment of critical bone defects attributed to various causes remains a great challenge, and repairing these defects with synthetic bone substitutes is the most common strategy. In general, tissue engineering materials that mimic the structural, mechanical and biological properties of natural bone have been extensively applied to fill bone defects and promote in situ bone regeneration. Hydrogels with extracellular matrix (ECM)-like properties are common tissue engineering materials, among which methacrylate-based gelatin (GelMA) hydrogels are widely used because of their tunable mechanical properties, excellent photocrosslinking capability and good biocompatibility. Owing to their lack of osteogenic activity, however, GelMA hydrogels are combined with other types of materials with osteogenic activities to improve the osteogenic capability of the current composites. There are three main aspects to consider when enhancing the bone regenerative performance of composite materials: osteoconductivity, vascularization and osteoinduction. Bioceramics, bioglass, biomimetic scaffolds, inorganic ions, bionic periosteum, growth factors and two-dimensional (2D) nanomaterials have been applied in various combinations to achieve enhanced osteogenic and bone regeneration activities. Three-dimensional (3D)-bioprinted scaffolds are a popular research topic in bone tissue engineering (BTE), and printed and customized scaffolds are suitable for restoring large irregular bone defects due to their shape and structural tunability, enhanced mechanical properties, and good biocompatibility. Herein, the recent progress in research on GelMA-based composite hydrogel scaffolds as multifunctional platforms for restoring critical bone defects in plastic or orthopedic clinics is systematically reviewed and summarized. These strategies pave the way for the design of biomimetic bone substitutes for effective bone reconstruction with good biosafety. This review provides novel insights into the development and current trends of research on GelMA-based hydrogels as effective bone tissue engineering (BTE) scaffolds for correcting bone defects, and these contents are summarized and emphasized from various perspectives (osteoconductivity, vascularization, osteoinduction and 3D-bioprinting). In addition, advantages and deficiencies of GelMA-based bone substitutes used for bone regeneration are put forward, and corresponding improvement measures are presented prior to their clinical application in near future (created with BioRender.com).

Microenvironment Restruction of Emerging 2D Materials and their Roles in Therapeutic and Diagnostic Nano-Bio-Platforms

Engineering advanced therapeutic and diagnostic nano-bio-platforms (NBPFs) have emerged as rapidly-developed pathways against a wide range of challenges in antitumor, antipathogen, tissue regeneration, bioimaging, and biosensing applications. Emerged 2D materials have attracted extensive scientific interest as fundamental building blocks or nanostructures among material scientists, chemists, biologists, and doctors due to their advantageous physicochemical and biological properties. This timely review provides a comprehensive summary of creating advanced NBPFs via emerging 2D materials (2D-NBPFs) with unique insights into the corresponding molecularly restructured microenvironments and biofunctionalities. First, it is focused on an up-to-date overview of the synthetic strategies for designing 2D-NBPFs with a cross-comparison of their advantages and disadvantages. After that, the recent key achievements are summarized in tuning the biofunctionalities of 2D-NBPFs via molecularly programmed microenvironments, including physiological stability, biocompatibility, bio-adhesiveness, specific binding to pathogens, broad-spectrum pathogen inhibitors, stimuli-responsive systems, and enzyme-mimetics. Moreover, the representative therapeutic and diagnostic applications of 2D-NBPFs are also discussed with detailed disclosure of their critical design principles and parameters. Finally, current challenges and future research directions are also discussed. Overall, this review will provide cutting-edge and multidisciplinary guidance for accelerating future developments and therapeutic/diagnostic applications of 2D-NBPFs.

Composite Nanocoatings of Biomedical Magnesium Alloy Implants: Advantages, Mechanisms, and Design Strategies

The rapid degradation of magnesium (Mg) alloy implants erodes mechanical performance and interfacial bioactivity, thereby limiting their clinical utility. Surface modification is among the solutions to improve corrosion resistance and bioefficacy of Mg alloys. Novel composite coatings that incorporate nanostructures create new opportunities for their expanded use. Particle size dominance and impermeability may increase corrosion resistance and thereby prolong implant service time. Nanoparticles with specific biological effects may be released into the peri-implant microenvironment during the degradation of coatings to promote healing. Composite nanocoatings provide nanoscale surfaces to promote cell adhesion and proliferation. Nanoparticles may activate cellular signaling pathways, while those with porous or core-shell structures may carry antibacterial or immunomodulatory drugs. Composite nanocoatings may promote vascular reendothelialization and osteogenesis, attenuate inflammation, and inhibit bacterial growth, thus increasing their applicability in complex clinical microenvironments such as those of atherosclerosis and open fractures. This review combines the physicochemical properties and biological efficiency of Mg-based alloy biomedical implants to summarize the advantages of composite nanocoatings, analyzes their mechanisms of action, and proposes design and construction strategies, with the purpose of providing a reference for promoting the clinical application of Mg alloy implants and to further the design of nanocoatings.

Piezocatalytic Medicine: An Emerging Frontier using Piezoelectric Materials for Biomedical Applications

Emerging piezocatalysts have demonstrated their remarkable application potential in diverse medical fields. In addition to their ultrahigh catalytic activities, their inherent and unique charge-carrier-releasing properties can be used to initiate various redox catalytic reactions, displaying bright prospects for future medical applications. Triggered by mechanical energy, piezocatalytic materials can release electrons/holes, catalyze redox reactions of substrates, or intervene in biological processes to promote the production of effector molecules for medical purposes, such as decontamination, sterilization, and therapy. Such a medical application of piezocatalysis is termed as piezocatalytic medicine (PCM) herein. To pioneer novel medical technologies, especially therapeutic modalities, this review provides an overview of the state-of-the-art research progress in piezocatalytic medicine. First, the principle of piezocatalysis and the preparation methodologies of piezoelectric materials are introduced. Then, a comprehensive summary of the medical applications of piezocatalytic materials in tumor treatment, antisepsis, organic degradation, tissue repair and regeneration, and biosensing is provided. Finally, the main challenges and future perspectives in piezocatalytic medicine are discussed and proposed, expecting to fuel the development of this emerging scientific discipline.

Cytotoxicity Induced by Black Phosphorus Nanosheets in Vascular Endothelial Cells via Oxidative Stress and Apoptosis Activation

Black phosphorus (BP), an emerging two-dimensional material with unique optical, thermoelectric, and mechanical properties, has been proposed as bioactive material for tissue engineering. However, its toxic effects on physiological systems remain obscure. The present study investigated the cytotoxicity of BP to vascular endothelial cells. BP nanosheets (BPNSs) with a diameter of 230 nm were fabricated via a classical liquid-phase exfoliation method. Human umbilical vein endothelial cells (HUVECs) were used to determine the cytotoxicity induced by BPNSs (0.31-80 μg/mL). When the concentrations were over 2.5 μg/mL, BPNSs adversely affected the cytoskeleton and cell migration. Furthermore, BPNSs caused mitochondrial dysfunction and generated excessive intercellular reactive oxygen species (ROS) at tested concentrations after 24 h. BPNSs could influence the expression of apoptosis-related genes, including the P53 and BCL-2 family, resulting in the apoptosis of HUVECs. Therefore, the viability and function of HUVECs were adversely influenced by the concentration of BPNSs over 2.5 μg/mL. These findings provide significant information for the potential applications of BP in tissue engineering.

Graphdiyne-loaded polycaprolactone nanofiber scaffold for peripheral nerve regeneration

Graphdiyne (GDY) is a kind of nanomaterial from the graphene carbon family with excellent physical and chemical properties. Despite some applications in medical engineering, GDY has not been used as an electroactive scaffold for tissue regeneration because of its unclear in vitro and in vivo biosafety profiles. Here, a conductive GDY nanomaterial-loaded polycaprolactone (PCL) scaffold was prepared by electrospinning technique. For the first time, the biocompatibility of GDY-based scaffold was assessed at the cellular and animal levels in a peripheral nerve injury (PNI) model. The findings indicated that the conductive three-dimensional (3D) GDY/PCL nerve guide conduits (NGCs) could significantly improve the proliferation, adhesion and glial expression of Schwann cells (SCs). The conduits were implanted into a rat 10-mm sciatic nerve defect model for 3 months in vivo. The toxicity of scaffolds to the organs was negligible, while the GDY/PCL NGCs significantly promoted myelination and axonal growth by upregulating the expression levels of SC marker (S100 β protein), Myelin basic protein (MBP), and axon regeneration marker (β3-tubulin protein (Tuj1) and neurofilament protein 200 (NF200)). In addition, upregulation of vascular factor expression in GDY/PCL NGC group suggested the potential role in angiogenesis to improve nerve repair by GDY nanomaterials. Our findings provide new perspectives on biocompatibility and effectiveness of GDY nanomaterial scaffold in peripheral nerve regeneration for preclinical application.

Piezoelectric Nanomaterials Activated by Ultrasound in Disease Treatment

Electric stimulation has been used in changing the morphology, status, membrane permeability, and life cycle of cells to treat certain diseases such as trauma, degenerative disease, tumor, and infection. To minimize the side effects of invasive electric stimulation, recent studies attempt to apply ultrasound to control the piezoelectric effect of nano piezoelectric material. This method not only generates an electric field but also utilizes the benefits of ultrasound such as non-invasive and mechanical effects. In this review, important elements in the system, piezoelectricity nanomaterial and ultrasound, are first analyzed. Then, we summarize recent studies categorized into five kinds, nervous system diseases treatment, musculoskeletal tissues treatment, cancer treatment, anti-bacteria therapy, and others, to prove two main mechanics under activated piezoelectricity: one is biological change on a cellular level, the other is a piezo-chemical reaction. However, there are still technical problems to be solved and regulation processes to be completed before widespread use. The core problems include how to accurately measure piezoelectricity properties, how to concisely control electricity release through complex energy transfer processes, and a deeper understanding of related bioeffects. If these problems are conquered in the future, piezoelectric nanomaterials activated by ultrasound will provide a new pathway and realize application in disease treatment.

Biomaterials based on hyaluronic acid, collagen and peptides for three-dimensional cell culture and their application in stem cell differentiation

In recent decades, three-dimensional (3D) cell culture technologies have been developed rapidly in the field of tissue engineering and regeneration, and have shown unique advantages and great prospects in the differentiation of stem cells. Herein, the article reviews the progress and advantages of 3D cell culture technologies in the field of stem cell differentiation. Firstly, 3D cell culture technologies are divided into two main categories: scaffoldless and scaffolds. Secondly, the effects of hydrogels scaffolds and porous scaffolds on stem cell differentiation in the scaffold category were mainly reviewed. Among them, hydrogels scaffolds are divided into natural hydrogels and synthetic hydrogels. Natural materials include polysaccharides, proteins, and their derivatives, focusing on hyaluronic acid, collagen and polypeptides. Synthetic materials mainly include polyethylene glycol (PEG), polyacrylic acid (PAA), polyvinyl alcohol (PVA), etc. In addition, since the preparation techniques have a large impact on the properties of porous scaffolds, several techniques for preparing porous scaffolds based on different macromolecular materials are reviewed. Finally, the future prospects and challenges of 3D cell culture in the field of stem cell differentiation are reviewed. This review will provide a useful guideline for the selection of materials and techniques for 3D cell culture in stem cell differentiation.

Multifunctional inorganic biomaterials: New weapons targeting osteosarcoma

Osteosarcoma is the malignant tumor with the highest incidence rate among primary bone tumors and with a high mortality rate. The anti-osteosarcoma materials are the cross field between material science and medicine, having a wide range of application prospects. Among them, biological materials, such as compounds from black phosphorous, magnesium, zinc, copper, silver, etc., becoming highly valued in the biological materials field as well as in orthopedics due to their good biocompatibility, similar mechanical properties with biological bones, good biodegradation effect, and active antibacterial and anti-tumor effects. This article gives a comprehensive review of the research progress of anti-osteosarcoma biomaterials.

Photosensitive and Conductive Hydrogel Induced Innerved Bone Regeneration for Infected Bone Defect Repair

Repairing infected bone defects is a challenge in the field of orthopedics because of the limited self-healing capacity of bone tissue and the susceptibility of refractory materials to bacterial activity. Innervation is the initiating factor for bone regeneration and plays a key regulatory role in subsequent vascularization, ossification, and mineralization processes. Infection leads to necrosis of local nerve fibers, impeding the repair of infected bone defects. Herein, a biomaterial that can induce skeletal-associated neural network reconstruction and bone regeneration with high antibacterial activity is proposed for the treatment of infected bone defects. A photosensitive conductive hydrogel is prepared by incorporating magnesium-modified black phosphorus (BP@Mg) into gelatin methacrylate (GelMA). The near-infrared irradiation-based photothermal and photodynamic treatment of black phosphorus endows it with strong antibacterial activity, improving the inflammatory microenvironment and reducing bacteria-induced bone tissue damage. The conductive nanosheets and bioactive ions released from BP@Mg synergistically improve the migration and secretion of Schwann cells, promote neurite outgrowth, and facilitate innerved bone regeneration. In an infected skull defect model, the GelMA-BP@Mg hydrogel shows efficient antibacterial activity and promotes bone and CGRP⁺ nerve fiber regeneration. The phototherapy conductive hydrogel provides a novel strategy based on skeletal-associated innervation for infected bone defect repair.

Modified black phosphorus quantum dots promotes spinal cord injury repair by targeting the AKT signaling pathway

Spinal cord injury (SCI) is a serious refractory disease of the central nervous system (CNS), which mostly caused by high-energy trauma. Existing interventions such as hormone shock and surgery are insufficient options, which relate to the secondary inflammation and neuronal dysfunction. Hydrogel with neuron-protective behaviors attracts tremendous attention, and black phosphorus quantum dots (BPQDs) encapsulating with Epigallocatechin-3-gallate (EGCG) hydrogels (E@BP) is designed for inflammatory modulation and SCI treatment in this study. E@BP displays good stability, biocompatibility and safety profiles. E@BP incubation alleviates lipopolysaccharide (LPS)-induced inflammation of primary neurons and enhances neuronal regeneration in vitro. Furthermore, E@BP reconstructs structural versus functional integrity of spinal cord tracts, which promotes recovery of motor neuron function in SCI rats after transplantation. Importantly, E@BP restarts the cell cycle and induces nerve regeneration. Moreover, E@BP diminishes local inflammation of SCI tissues, characterized by reducing accumulation of astrocyte, microglia, macrophages, and oligodendrocytes. Indeed, a common underlying mechanism of E@BP regulating neural regenerative and inflammatory responses is to promote the phosphorylation of key proteins related to AKT signaling pathway. Together, E@BP probably repairs SCI by reducing inflammation and promoting neuronal regeneration via the AKT signaling pathway.

Construction of a Band-Aid Like Cardiac Patch for Myocardial Infarction with Controllable H2 S Release

Excessive or persistent inflammation incites cardiomyocytes necrosis by generating reactive oxygen species in myocardial infarction (MI). Hydrogen sulfide (H2 S), a gaseous signal molecule, can quickly permeate cells and tissues, growing concerned for its cardioprotective effects. However, short resident time and strong side effects greatly restrict its application. Herein, a complex scaffold (AAB) is first developed to slowly release H2 S for myocardial protection by integrating alginate modified with 2-aminopyridine-5-thiocarboxamide (H2 S donor) into albumin electrospun fibers. Next, a band-aid like patch is constructed based on AAB (center) and nanocomposite scaffold which comprises albumin scaffold and black phosphorus nanosheets (BPNSs). With near-infrared laser (808 nm), thermal energy generated by BPNSs can locally change the molecular structure of fibrous scaffold, thereby attaching patch to the myocardium. In this study, it is also demonstrated that AAB can enhance regenerative M2 macrophage and attenuate inflammatory polarization of macrophages via reduction in intracellular ROS. Eventually, this engineered cardiac patch can relieve inflammation and promote angiogenesis after MI, and thereby recover heart function, providing a promising therapeutic strategy for MI treatment.

The Application of Black Phosphorus Nanomaterials in Bone Tissue Engineering

Recently, research on and the application of nanomaterials such as graphene, carbon nanotubes, and metal-organic frameworks has become increasingly popular in tissue engineering. In 2014, a two-dimensional sheet of black phosphorus (BP) was isolated from massive BP crystals. Since then, BP has attracted significant attention as an emerging nanomaterial. BP possesses many advantages such as light responsiveness, electrical conductivity, degradability, and good biocompatibility. Thus, it has broad prospects in biomedical applications. Moreover, BP is composed of phosphorus, which is a key bone tissue component with good biocompatibility and osteogenic repair ability. Thereby, BP exhibits excellent advantages for application in bone tissue engineering. In this review, the structure and the physical and chemical properties of BP are described. In addition, the current applications of BP in bone tissue engineering are reviewed to aid the future research and application of BP.

Energy-Supporting Enzyme-Mimic Nanoscaffold Facilitates Tendon Regeneration Based on a Mitochondrial Protection and Microenvironment Remodeling Strategy

Tendon injury is a tricky and prevalent motor system disease, leading to compromised daily activity and disability. Insufficient regenerative capability and dysregulation of immune microenvironment are the leading causes of functional loss. First, this work identifies persistent oxidative stress and mitochondrial impairment in the regional tendon tissues postinjury. Therefore, a smart scaffold incorporating the enzyme mimicry nanoparticle-ceria nanozyme (CeNPs) into the nanofiber bundle scaffold (NBS@CeO) with porous, anisotropic, and enhanced mechanical properties is designed to innovatively explore a targeted energy-supporting repair strategy by rescuing mitochondrial function and remodeling the microenvironment favoring endogenous regeneration. The integrated CeNPs scavenge excessive reactive oxygen species (ROS), stabilize the mitochondria membrane potential (ΔΨm), and ATP synthesis of tendon-derived stem cells (TDSCs) under oxidative stress. In a rat Achilles tendon defect model, NBS@CeO reduces oxidative damage and accelerates structural regeneration of collagen fibers, manifesting as recovering mechanical properties and motor function. Furthermore, NBS@CeO mediates the rebalance of endogenous regenerative signaling and dysregulated immune microenvironment by alleviating senescence and apoptosis of TDSCs, downregulating the secretion of senescence-associated secretory phenotype (SASP), and inducing macrophage M2 polarization. This innovative strategy highlights the role of NBS@CeO in tendon repair and thus provides a potential therapeutic approach for promoting tendon regeneration.

Graphdiyne-Related Materials in Biomedical Applications and Their Potential in Peripheral Nerve Tissue Engineering

Graphdiyne (GDY) is a new member of the family of carbon-based nanomaterials with hybridized carbon atoms of sp and sp², including α, β, γ, and (6,6,12)-GDY, which differ in their percentage of acetylene bonds. The unique structure of GDY provides many attractive features, such as uniformly distributed pores, highly π-conjugated structure, high thermal stability, low toxicity, biodegradability, large specific surface area, tunable electrical conductivity, and remarkable thermal conductivity. Therefore, GDY is widely used in energy storage, catalysis, and energy fields, in addition to biomedical fields, such as biosensing, cancer therapy, drug delivery, radiation protection, and tissue engineering. In this review, we first discuss the synthesis of GDY with different shapes, including nanotubes, nanowires, nanowalls, and nanosheets. Second, we present the research progress in the biomedical field in recent years, along with the biodegradability and biocompatibility of GDY based on the existing literature. Subsequently, we present recent research results on the use of nanomaterials in peripheral nerve regeneration (PNR). Based on the wide application of nanomaterials in PNR and the remarkable properties of GDY, we predict the prospects and current challenges of GDY-based materials for PNR.

Biofeedback electrostimulation for bionic and long-lasting neural modulation

Invasive electrical stimulation (iES) is prone to cause neural stimulus-inertia owing to its excessive accumulation of exogenous charges, thereby resulting in many side effects and even failure of nerve regeneration and functional recovery. Here, a wearable neural iES system is well designed and built for bionic and long-lasting neural modulation. It can automatically yield biomimetic pulsed electrical signals under the driven of respiratory motion. These electrical signals are full of unique physiological synchronization can give biofeedback to respiratory behaviors, self-adjusting with different physiological states of the living body, and thus realizing a dynamic and biological self-matched modulation of voltage-gated calcium channels on the cell membrane. Abundant cellular and animal experimental evidence confirm an effective elimination of neural stimulus-inertia by these bioelectrical signals. An unprecedented nerve regeneration and motor functional reconstruction are achieved in long-segmental peripheral nerve defects, which is equal to the gold standard of nerve repair -- autograft. The wearable neural iES system provides an advanced platform to overcome the common neural stimulus-inertia and gives a broad avenue for personalized iES therapy of nerve injury and neurodegenerative diseases.

Designing wereable neural invasive electrical stimulation system remains a challenge. Here, researchers provide an effective technology platform for the elimination of tricky neural stimulus-inertia using bionic electronic modulation, which is a significant step forward for long-lasting treatment of nervous system diseases.

Research trends in biomedical applications of two-dimensional nanomaterials over the last decade - A bibliometric analysis

Two-dimensional (2D) nanomaterials with versatile properties have been widely applied in the field of biomedicine. Despite various studies having reviewed the development of biomedical 2D nanomaterials, there is a lack of a study that objectively summarizes and analyzes the research trend of this important field. Here, we employ a series of bibliometric methods to identify the development of the 2D nanomaterial-related biomedical field during the past 10 years from a holistic point of view. First, the annual publication/citation growth, country/institute/author distribution, referenced sources, and research hotspots are identified. Thereafter, based on the objectively identified research hotspots, the contributions of 2D nanomaterials to the various biomedical subfields, including those of biosensing, imaging/therapy, antibacterial treatment, and tissue engineering are carefully explored, by considering the intrinsic properties of the nanomaterials. Finally, prospects and challenges have been discussed to shed light on the future development and clinical translation of 2D nanomaterials. This review provides a novel perspective to identify and further promote the development of 2D nanomaterials in biomedical research.

Bacterial cellulose-based composites for nerve tissue engineering

Nerve injuries and neurodegenerative disorders are very serious and costly medical challenges. Damaged nerve tissue may not be able to heal and regain its function, and scar tissue may restrict nerve cell regeneration. In recent years, new electroactive biomaterials have attracted widespread attention in the neural tissue engineering field. Bacterial cellulose (BC) due to its unique properties such as good mechanical properties, high water retention, biocompatibility, high crystallinity, large surface area, high purity, very fine network, and inability to absorb in the human body due to cellulase deficiency, can be considered a promising treatment for neurological injuries and disorders that require long-term support. However, BC lacks electrical activity, but can significantly improve the nerve regeneration rate by combining with conductive structures. Electrical stimulation has been shown to be an effective means of increasing the rate and accuracy of nerve regeneration. Many factors, such as the intensity and pattern of electrical current, have positive effects on cellular activity, including cell adhesion, proliferation, migration and differentiation, and cell-cell/tissue/molecule/drug interaction. This study discusses the importance and essential role of BC-based biomaterials in neural tissue regeneration and the effects of electrical stimulation on cellular behaviors.