Injectable Hydrogel System Incorporating Black Phosphorus Nanosheets and Tazarotene Drug for Enhanced Vascular and Nerve Regeneration in Spinal Cord Injury Repair

Biomaterial-based strategies: a new era in spinal cord injury treatment

Enhancing neurological recovery and improving the prognosis of spinal cord injury have gained research attention recently. Spinal cord injury is associated with a complex molecular and cellular microenvironment. This complexity has prompted researchers to elucidate the underlying pathophysiological mechanisms and changes and to identify effective treatment strategies. Traditional approaches for spinal cord injury repair include surgery, oral or intravenous medications, and administration of neurotrophic factors; however, the efficacy of these approaches remains inconclusive, and serious adverse reactions continue to be a concern. With advancements in tissue engineering and regenerative medicine, emerging strategies for spinal cord injury repair now involve nanoparticle-based nanodelivery systems, scaffolds, and functional recovery techniques that incorporate biomaterials, bioengineering, stem cell, and growth factors as well as three-dimensional bioprinting. Ideal biomaterial scaffolds should not only provide structural support for neuron migration, adhesion, proliferation, and differentiation but also mimic the mechanical properties of natural spinal cord tissue. Additionally, these scaffolds should facilitate axon growth and neurogenesis by offering adjustable topography and a range of physical and biochemical cues. The three-dimensionally interconnected porous structure and appropriate physicochemical properties enabled by three-dimensional biomimetic printing technology can maximize the potential of biomaterials used for treating spinal cord injury. Therefore, correct selection and application of scaffolds, coupled with successful clinical translation, represent promising clinical objectives to enhance the treatment efficacy for and prognosis of spinal cord injury. This review elucidates the key mechanisms underlying the occurrence of spinal cord injury and regeneration post-injury, including neuroinflammation, oxidative stress, axon regeneration, and angiogenesis. This review also briefly discusses the critical role of nanodelivery systems used for repair and regeneration of injured spinal cord, highlighting the influence of nanoparticles and the factors that affect delivery efficiency. Finally, this review highlights tissue engineering strategies and the application of biomaterial scaffolds for the treatment of spinal cord injury. It discusses various types of scaffolds, their integrations with stem cells or growth factors, and approaches for optimization of scaffold design.

Electric Stimulation Combined with Biomaterials for Repairing Spinal Cord Injury

Spinal cord injury (SCI) is a central nervous system (CNS) disease with a high disability rate, and reconstructing motor function after SCI remains a global challenge. Recent advancements in rehabilitation and regenerative medicine offer new approaches to SCI repair. Electrical stimulation has been shown to alter cell membrane charge distribution, generating action potentials, and affecting cell behavior. This method aids axon regeneration and neurotrophic factor upregulation, crucial for nerve repair. Biomaterials, used as scaffolds or coatings in cell culture and tissue engineering, enhance cell proliferation, migration, differentiation, and tissue regeneration. Electroactive biomaterials combined with electrical stimulation show promise in regenerating nerve, heart, and bone tissues. In this paper, different types of electrical stimulation and biomaterials applied to SCI are described, and the current application and research progress of electrical stimulation combined with biomaterials in the treatment of SCI are described, as well as the future prospects and challenges.

Hypoxia-Driven Neurovascular Impairment Underlies Structural-Functional Dissociation in Diabetic Sudomotor Dysfunction

Sudomotor dysfunction in diabetic patients increases the risk of fissures, infections, and diabetic foot ulcers (DFUs), thereby reducing the quality of life. Despite its clinical importance, the mechanisms underlying this dysfunction remain inadequately elucidated. This study addresses this gap by demonstrating that despite structural integrity, sweat glands (SGs) in diabetic individuals with DFUs, and a murine model of diabetic neuropathy (DN), exhibit functional impairments, as confirmed by histological and functional assays. Integrated transcriptome and proteome analysis revealed significant upregulation of the SG microenvironment in response to hypoxia, highlighting potential underlying pathways involved. In addition, histological staining and tissue clearing techniques provided evidence of impaired neurovascular networks adjacent to SGs. Single-cell RNA sequencing unveiled intricate intercellular communication networks among endothelial cells (ECs), neural cells (NCs), and sweat gland cells (SGCs), emphasizing intricate cellular interactions within the SG microenvironment. Furthermore, an in vitro SGC-NC interaction model (SNIM) was employed to validate the supportive role of NCs in regulating SGC functions, highlighting the neurovascular-SG axis in diabetic pathophysiology. These findings confirm the hypoxia-driven upregulation of the SG microenvironment and underscore the critical role of the neurovascular-SG axis in diabetic pathophysiology, providing insights into potential therapeutic targets for managing diabetic complications and improving patient outcomes.

Black Phosphorus Nanosheet-Based Composite Biomaterials for the Enhanced Repair of Infectious Bone Defects

Infectious bone defects pose significant challenges in orthopedic practice, marked by persistent bacterial infection and ongoing inflammatory responses. Recent advancements in bone tissue engineering have led to the development of biomaterials with both antibacterial properties and the ability to promote bone regeneration, offering new solutions to these complex issues. Black phosphorus nanosheets (BPNS), a unique two-dimensional material, demonstrate exceptional biocompatibility, bioactivity, and antibacterial properties. Their combination of osteogenic, antibacterial, and anti-inflammatory effects positions BPNS as an ideal candidate for addressing bone defects complicated by infection. This Review explores the potential of BPNS-based composite biomaterials in repairing infectious bone defects, discussing their molecular mechanisms for antibacterial activity, including intrinsic antibacterial properties, photothermal therapy (PTT), photodynamic therapy (PDT), and drug delivery. The application of BPNS in treating infectious bone defects, through hydrogels, scaffolds, coatings, and fibers, is also discussed. The Review emphasizes the transformative role of BPNS in bone tissue engineering and advocates for continued research and development in this promising field.

Bioactive Peptide Hydrogel Scaffold with High Fluidity, Thermosensitivity, and Neurotropism in 3D Spatial Structure for Promoted Repair of Spinal Cord Injury

Spinal cord injury (SCI) has been considered a clinically challenging disease that is characterized by local disturbance of the microenvironment, which inhibits post-injury neural regeneration. The simulation of a microenvironment conducive to the regeneration of spinal cord is beneficial for SCI repair. In this study, bioactive composite hydrogels are developed that mimic the regenerative microenvironment of spinal cord for enhanced SCI repair. The fabricated composite hydrogels (CRP) based on chitosan (CS), RADA16 nanofibers, and nerve-promoted peptide (PPFLMLLKGSTR) exhibit excellent injectability, superior biodegradability and biocompatibility. In addition, the CRP hydrogels can form quickly (a few minutes) by mixing three components at human body temperature, showing high potential as a biomimetic matrix for in situ repair of SCI. The in vitro studies demonstrate that the CRP hydrogels can not only promote the proliferation and migration of bone marrow mesenchymal stem cells but also induce the proliferation and differentiation of neural stem cells (NSCs) into neurons. Meanwhile, the hydrogels reveal the efficiency of protecting neurons and promoting axonal growth. Furthermore, the in vivo tests prove that the CRP hydrogels can reduce post-SCI inflammatory responses, inhibit reactive astrocyte over-proliferation, and promote the migration, proliferation, and differentiation of endogenous NSCs, which agree well with the in vitro results. The pre-clinical test demonstrates that the CRP hydrogels restore the motor function in completely transected spinal cord rats, and the SCI repair mechanism may involve the activation of the PI3K/AKT/mTOR pathway. It is believed that the strategies shown in this work will be valuable for the design and synthesis of novel hydrogels for biomedical and tissue engineering applications.

Tissue-Adaptive BSA Hydrogel with Dual Release of PTX and bFGF Promotes Spinal Cord Injury Repair via Glial Scar Inhibition and Axon Regeneration

Spinal cord injury (SCI) is a severe clinical disease usually accompanied by activated glial scar, neuronal axon rupture, and disabled motor function. To mimic the microenvironment of the SCI injury site, a hydrogel system with a comparable mechanical property to the spinal cord is desirable. Therefore, a novel elastic bovine serum albumin (BSA) hydrogel is fabricated with excellent adhesive, injectable, and biocompatible properties. The hydrogel is used to deliver paclitaxel (PTX) together with basic fibroblast growth factor (bFGF) to inhibit glial scar formation as well as promote axon regeneration and motor function for SCI repair. Due to the specific interaction of BSA with both drugs, bFGF, and PTX can be controllably released from the hydrogel system to achieve an effective concentration at the wound site during the SCI regeneration process. Moreover, benefiting from the combination of PTX and bFGF, this bFGF/PTX@BSA system significantly aided axon repair by promoting the elongation of axons across the glial scar with reduced reactive astrocyte secretion. In addition, remarkable anti-apoptosis of nerve cells is evident with the bFGF/PTX@BSA system. Subsequently, this multi-functionalized drug system significantly improved the motor function of the rats after SCI. These results reveal that bFGF/PTX@BSA is an ideal functionalized material for nerve repair in SCI.

Hydrogel-based therapeutic strategies for spinal cord injury repair: Recent advances and future prospects

Spinal cord injury (SCI) is a debilitating condition that can result in significant functional impairment and loss of quality of life. There is a growing interest in developing new therapies for SCI, and hydrogel-based multimodal therapeutic strategies have emerged as a promising approach. They offer several advantages for SCI repair, including biocompatibility, tunable mechanical properties, low immunogenicity, and the ability to deliver therapeutic agents. This article provides an overview of the recent advances in hydrogel-based therapy strategies for SCI repair, particularly within the past three years. We summarize the SCI hydrogels with varied characteristics such as phase-change hydrogels, self-healing hydrogel, oriented fibers hydrogel, and self-assembled microspheres hydrogel, as well as different functional hydrogels such as conductive hydrogels, stimuli-responsive hydrogels, adhesive hydrogel, antioxidant hydrogel, sustained-release hydrogel, etc. The composition, preparation, and therapeutic effect of these hydrogels are briefly discussed and comprehensively evaluated. In the end, the future development of hydrogels in SCI repair is prospected to inspire more researchers to invest in this promising field.

A chitosan-based light-curing hydrogel dressing for accelerated healing of infected wounds

Bacterial infections, excessive reactive oxygen species (ROS) accumulation and a persistent inflammatory response severely impede the wound healing process. In this study, we developed a novel multifunctional hydrogel dressing (LCPN) based on lipoic acid modified chitosan (LAMC), polypyrrole nanoparticles (PPy NPs) and nicotinamide mononucleotide (NMN) for accelerated healing of infected wounds. The synthesized LCPN hydrogel has several properties. Modification of lipoic acid significantly enhances the water solubility of chitosan making it easier to dissolve and absorb wound secretions. Interestingly, owing to the breaking and restructuring of disulfide bonds, LCPN hydrogel can be quickly bonded under UV light without relying on photoinitiators. In addition, the incorporation of PPy NPs not only enhances the electrical conductivity of LCPN hydrogel, but also confers photothermal antimicrobial capability to LCPN hydrogel. More importantly, the sustained release of NMN in LCPN hydrogel can significantly enhance cell proliferation, migration and antioxidant capacity, which is conducive to accelerated wound healing. In vitro and in vivo experiments have shown that LCPN hydrogel has excellent biocompatibility and the ability to promote wound healing. Therefore, the prepared multifunctional hydrogel is expected to be used as a novel dressing to accelerate wound healing.

The Porous SilMA Hydrogel Scaffolds Carrying Dual-Sensitive Paclitaxel Nanoparticles Promote Neuronal Differentiation for Spinal Cord Injury Repair

BACKGROUND

In the intricate pathological milieu post-spinal cord injury (SCI), neural stem cells (NSCs) frequently differentiate into astrocytes rather than neurons, significantly limiting nerve repair. Hence, the utilization of biocompatible hydrogel scaffolds in conjunction with exogenous factors to foster the differentiation of NSCs into neurons has the potential for SCI repair.

METHODS

In this study, we engineered a 3D-printed porous SilMA hydrogel scaffold (SM) supplemented with pH-/temperature-responsive paclitaxel nanoparticles (PTX-NPs). We analyzed the biocompatibility of a specific concentration of PTX-NPs and its effect on NSC differentiation. We also established an SCI model to explore the ability of composite scaffolds for in vivo nerve repair.

RESULTS

The physical adsorption of an optimal PTX-NPs dosage can simultaneously achieve pH/temperature-responsive release and commendable biocompatibility, primarily reflected in cell viability, morphology, and proliferation. An appropriate PTX-NPs concentration can steer NSC differentiation towards neurons over astrocytes, a phenomenon that is also efficacious in simulated injury settings. Immunoblotting analysis confirmed that PTX-NPs-induced NSC differentiation occurred via the MAPK/ERK signaling cascade. The repair of hemisected SCI in rats demonstrated that the composite scaffold augmented neuronal regeneration at the injury site, curtailed astrocyte and fibrotic scar production, and enhanced motor function recovery in rat hind limbs.

CONCLUSION

The scaffold's porous architecture serves as a cellular and drug carrier, providing a favorable microenvironment for nerve regeneration. These findings corroborate that this strategy amplifies neuronal expression within the injury milieu, significantly aiding in SCI repair.

Hydrogels for Neural Regeneration: Exploring New Horizons

Nerve injury can significantly impair motor, sensory, and autonomic functions. Understanding nerve degeneration, particularly Wallerian degeneration, and the mechanisms of nerve regeneration is crucial for developing effective treatments. This manuscript reviews the use of advanced hydrogels that have been researched to enhance nerve regeneration. Hydrogels, due to their biocompatibility, tunable properties, and ability to create a supportive microenvironment, are being explored for their effectiveness in nerve repair. Various types of hydrogels, such as chitosan-, alginate-, collagen-, hyaluronic acid-, and peptide-based hydrogels, are discussed for their roles in promoting axonal growth, functional recovery, and myelination. Advanced formulations incorporating growth factors, bioactive molecules, and stem cells show significant promise in overcoming the limitations of traditional therapies. Despite these advancements, challenges in achieving robust and reliable nerve regeneration remain, necessitating ongoing research to optimize hydrogel-based interventions for neural regeneration.

Injectable Hydrogels for Nervous Tissue Repair-A Brief Review

The repair of nervous tissue is a critical research field in tissue engineering because of the degenerative process in the injured nervous system. In this review, we summarize the progress of injectable hydrogels using in vitro and in vivo studies for the regeneration and repair of nervous tissue. Traditional treatments have not been favorable for patients, as they are invasive and inefficient; therefore, injectable hydrogels are promising for the treatment of damaged tissue. This review will contribute to a better understanding of injectable hydrogels as potential scaffolds and drug delivery system for neural tissue engineering applications.