Trimanganese Tetroxide Nanozyme protects Cartilage against Degeneration by Reducing Oxidative Stress in Osteoarthritis

Renal-clearable and mitochondria-targeted metal-engineered carbon dot nanozymes for regulating mitochondrial oxidative stress in acute kidney injury

Mitochondrial dysfunction-induced oxidative stress is a key pathogenic factor in acute kidney injury (AKI). Despite this, current mitochondrial-targeted antioxidant therapies have shown limited efficacy in clinical settings. In this study, we introduce a novel renal-clearable and mitochondria-targeted antioxidant nanozyme (TPP@RuCDzyme) designed to precisely modulate mitochondrial oxidative stress and mitigate AKI progression. TPP@RuCDzyme was synthesized by integrating ruthenium-doped carbon dots (CDs) with triphenylphosphine (TPP), a mitochondria-targeting moiety. This nanozyme system exhibits cascade enzyme-like activities, mimicking superoxide dismutase (SOD) and catalase (CAT), to efficiently convert cytotoxic superoxide (O2•-) and hydrogen peroxide (H2O2) into non-toxic water (H2O) and oxygen (O2). This dual-enzyme mimicry effectively alleviates mitochondrial oxidative damage, restores mitochondrial function, and inhibits apoptosis. Compared to RuCDzyme alone, TPP@RuCDzyme demonstrated significantly enhanced efficacy in alleviating glycerol-induced AKI by inhibiting oxidative stress. By leveraging the catalytic activity derived from the integration of CDs and a metallic element, this study presents a promising therapeutic strategy for AKI and other renal diseases associated with mitochondrial dysfunction.

Bioactive phosphorus dendrimers deliver protein/drug to tackle osteoarthritis via cooperative macrophage reprogramming

Reprogramming imbalanced synovial macrophages and shaping an immune microenvironment conducive to bone and cartilage growth is crucial for efficient tackling of osteoarthritis (OA). Herein, we present a co-delivery nanosystem based on generation 2 (G2) hydroxyl-terminated bioactive phosphorus dendrimers (G2-OH24) that were loaded with both catalase (CAT) and quercetin (Que). The created G2-OH24/CAT@Que complexes exhibit a uniformly distributed spherical morphology with a size of 138.8 nm, possess robust stability, and induce macrophage reprogramming toward anti-inflammatory M2 phenotype polarization and antioxidation through cooperative CAT-catalyzed oxygen generation, Que-mediated mitochondrial homeostasis restoration, and inherent immunomodulatory activity of dendrimer. Such macrophage reprogramming leads to chondrocyte apoptosis inhibition and osteogenic differentiation of bone mesenchymal stem cells. Administration of G2-OH24/CAT@Que to an OA mouse model results in attenuation of pathological features such as cartilage degeneration, bone erosion, and synovitis through oxidative stress alleviation and inflammatory factor downregulation in inflamed joints. Excitingly, the G2-OH24/CAT@Que also polarized macrophages in adherent effusion monocytes (AEMs) extracted from joint cavity effusions of OA patients to M2 phenotype and downregulated reactive oxygen species levels in AEMs. This study suggests a promising nanomedicine formulation of phosphorus dendrimer-based co-delivery system to effectively tackle OA through the benefits of full-active ingredients of dendrimer, drug, and protein.

Current Status and Perspectives of Research on Polymer Hydrogels in the Treatment and Protection of Osteoarthritis

Arthritis is a degenerative disease characterized by chronic cartilage degeneration. It affects hundreds of millions of people worldwide and often has serious consequences such as joint pain and swelling, limited mobility, and joint deformity. However, conventional treatments still struggle to achieve satisfactory results. Finding more effective treatments for arthritis remains an important clinical challenge. As hydrogels have a unique 3D spatial mesh structure, significant material interaction ability, adjustable mechanical properties, and good biodegradability, they can provide a suitable cellular or tissue microenvironment, and their potential in scaffolding effect, lubrication, anti-inflammatory effect, or drug or cellular delivery is expected to be a potent therapeutic approach for the treatment of osteoarthritis. In this review, three aspects of hydrogel products for osteoarthritis treatment are comprehensively summarized and discussed, namely, material selection and gel design, exploration of cross-linking mechanisms, and mechanisms of hydrogel therapy for osteoarthritis, and focus on the advantages and limitations of their clinical applications, which point out the direction of the development strategy of innovative products in this field, applied research, and clinical transformation.

Advances in the Treatment of Spinal Cord Injury with Nanozymes

Spinal cord injury (SCI) with increasing incidence can lead to severe disability. The pathological process involves complex mechanisms such as oxidative stress, inflammation, and neuron apoptosis. Current treatment strategies focusing on the relief of oxidative stress and inflammation have achieved good effects, while many problems and challenges remain such as the side effect and short half-life of the therapeutic agents. Nanozymes exhibiting good biocatalytic activities can sustainably scavenge free radicals, inhibit neuroinflammation, and protect the neurons. With high stability in physiological conditions and cost-effectiveness, the nanozymes provide a new strategy for SCI treatment. In this Review, we outline the advances of nanozymes and their enzyme-mimicking activities and highlight the progress in the intervention of SCI-adopting nanozymes. We also propose future directions and clinical translation for the nanozyme strategy against SCI.

Quercetin-primed MSC exosomes synergistically attenuate osteoarthritis progression

BACKGROUND

Osteoarthritis (OA), a degenerative joint disease characterized by cartilage degradation and inflammation, lacks effective disease-modifying therapies. Quercetin, a bioactive flavonoid derived from Traditional Chinese Medicine, exhibits anti-inflammatory and chondroprotective properties but is limited by poor bioavailability. Mesenchymal stem cell-derived exosomes (MSC-Exos) offer a promising strategy for targeted drug delivery and cartilage regeneration.

METHODS

Bone marrow-derived MSC exosomes (Que-Exo) were isolated after preconditioning with quercetin (1µM, 24 h). Their effects were evaluated in IL-1β-stimulated chondrocytes via RT-qPCR, Western blot, transcriptomics, and proteomics. An ACLT-induced OA mouse model received intra-articular injections of Que-Exo, with cartilage integrity assessed by Safranin O staining and OARSI scoring.

RESULTS

Que-Exo significantly reduced IL-1β-induced pro-inflammatory markers (MMP9 and COX-2) and restored cartilage repair genes (SOX9 and Collagen II) compared to untreated exosomes. Multi-omics analyses revealed activation of PI3K-AKT signaling and glutathione metabolism pathways. In vivo, Que-Exo mitigated cartilage degradation and preserved proteoglycan content.

CONCLUSIONS

Quercetin-preconditioned MSC exosomes synergistically enhance chondroprotection and anti-inflammatory effects, offering a novel therapeutic strategy for OA by combining herbal bioactive compounds with exosome-mediated delivery.

Nanozymes meet hydrogels: Fabrication, progressive applications, and perspectives

Nanozyme, a class of emerging enzyme mimics, is the nanomaterials with enzyme-mimicking activity, which has obtained significant and widespread applications in various fields. However, they still face many challenges in practical applications (e.g., instability and low biocompatibility in the physiological environments), which affect their widespread applications to a certain extent. Hydrogels with superior performances (e.g., the controllable degradability, good biocompatibility, hydrophilic properties, and adjustable physical properties) may provide a promising strategy to make up the existing deficiencies of nanozymes in practical applications. Thus, the sapiential combination of nanozymes with hydrogels endows nanozyme hydrogels with both characteristics of nanozymes and properties of hydrogels, making nanozyme hydrogels become novel multifunctional materials. In this review, we comprehensively summarizes the preparation, properties, and progressive applications of nanozyme hydrogels. First of all, the main design and preparation strategies of nanozyme hydrogels are considerately summarized. Then, the properties of different nanozyme hydrogels are introduced. In addition, sophisticated applications of nanozyme hydrogels in the fields of biosensing, biomedicine applications, and environmental are comprehensively summarized. Most importantly, future obstacles and chances in this emerging field are profoundly proposed. This review will provide a new horizon for the development and future applications of novel nanozyme hydrogels.

Cerium Dioxide Nanoparticles-Based Inspector Enhances Mitochondrial Quality Control to Maintain Chondrocyte Homeostasis in Osteoarthritis Therapy

Imbalanced mitochondrial quality control is strongly linked to the onset and development of osteoarthritis (OA). However, current research primarily focuses on local cartilage repair and phenotype maintenance, lacking a systematic approach to subcellular mitochondrial quality control. To address this, the present study proposes a mitochondrial quality control strategy based on nanozyme hydrogel microspheres ("mitochondrial inspector"), constructed through electrostatic self-assembly, incorporation of dynamic diselenide bonds, and microfluidic technology. The mitochondrial oxidative stress microenvironment is improved by cerium dioxide nanoparticles and combined with metformin to activate autophagy to clear persistently dysfunctional mitochondria, thereby inhibiting OA progression. In vitro results showed that "mitochondrial inspector" not only significantly improved the oxidative stress microenvironment of chondrocytes, but also efficiently scavenged the damaged mitochondria, increased the mitochondrial membrane potential by over 20-fold, and notably improved the mitochondrial function and chondrocyte homeostasis. In a rat OA model, minimally invasive intra-articular injection of the "mitochondrial inspector" effectively regulated mitochondrial quality, alleviated cartilage matrix degradation, reduced osteophyte formation by ≈80%, and reduced the Mankin score for cartilage damage by over 70%. In summary, this study presents a novel nanozyme microsphere-based mitochondrial quality control strategy for the treatment of OA, providing new insights for subcellular therapies for other aging-related diseases.

Intervening with nanozymes in aging-related diseases: Strategies for restoring mitochondrial function

The decline in mitochondrial function has been identified as one of the central pathological mechanisms underlying a variety of aging-related diseases. Nanozymes are nanomaterials with intrinsic enzyme-like properties and are important alternatives to natural enzymes. As emerging biocatalysts, nanozymes exhibit significant potential in mimicking the activity of natural enzymes, enhancing mitochondrial function, and offering novel therapeutic strategies for aging-related conditions. This review provides an overview of various approaches to modulate the catalytic activity of nanozymes, considering factors such as particle size, shape, surface modifications, and constituent elements. It then examines the role of nanozymes in mitigating aging-related diseases by preserving mitochondrial health, with a particular focus on their ability to regulate three critical aspects: mitochondrial energy metabolism, quality control, and antioxidant capacity. By improving mitochondrial energy generation, supporting mitochondrial integrity, and eliminating excess reactive oxygen species (ROS), nanozymes offer new therapeutic possibilities for neurodegenerative diseases, bone-related disorders, and diabetes. Finally, this article discusses the major challenges faced in this field, including issues such as the scalability, biocompatibility, and targeting ability of nanozymes. It also emphasizes that future research should focus on enhancing clinical translation to ensure that nanozymes can play an effective role in practical therapeutic applications.

Microalgae-Derived Extracellular Vesicles Synergize with Herbal Hydrogel for Energy Homeostasis in Osteoarthritis Treatment

Treatment of osteoarthritis (OA) remains challenging owing to its complex pathological microenvironment, which involves reactive oxygen species, chronic inflammation, mitochondrial dysfunction, energy deficiency, and cartilage degeneration. Herein, we report for extracellular vesicles (SP-EVs) derived from the photosynthetic microorganism Spirulina platensis contain antioxidative and ATP-dependent active and metabolic-related compounds for OA treatment. SP-EVs were effectively delivered to chondrocytes, demonstrating the potential for modulating cellular communication and energy homeostasis. To facilitate sustained delivery of SP-EVs, the rhein hydrogel system was used for intra-articular injection (Rh Gel@SP-EVs), which demonstrated pH responsiveness under mildly acidic conditions and synergistic anti-inflammatory effects. Rh Gel@SP-EVs significantly rescued mitochondrial dysfunction by ameliorating inflammation-mediated oxidative stress and restoring the mitochondrial membrane potential in chondrocytes. Improved mitochondrial function facilitates the replenishment of ATP levels, further contributing to the balance of anabolic and catabolic processes within the cartilage matrix, eventually decelerating OA progression. Rh Gel@SP-EVs also modulated the Janus kinase-signal transducer and activator of transcription 3 signaling pathway, implicated in suppressing inflammatory responses. This therapeutic strategy utilized a microalgae-based herbal hydrogel system to modulate the sustained release of SP-EVs, offering an effective approach for treating OA by regulating energy metabolism and anti-inflammatory mechanisms.

Ginkgetin delays the progression of osteoarthritis by inhibiting the NF-κB and MAPK signaling pathways

BACKGROUND

Osteoarthritis (OA) is considered an advancing chronic degenerative joint disease, leading to severe physical functional impairment of patients. Its development is closely related to increased inflammation and oxidative stress within the joint. Ginkgetin (GK), a natural non-toxic chemical, has proven anti-inflammatory, antioxidant, anti-tumor, and neuroprotective effects.

METHODS

First, this study utilizes network pharmacology to explore the intrinsic connection between GK and OA. In vitro, SW1353 human cartilage cells were stimulated with Tert-butyl hydrogen peroxide (TBHP), and different GK concentrations were pre-treated to evaluate its protective effects. GK's anti-inflammatory and antioxidative effects were comprehensively assessed via MTT assay, western blot, cell immunofluorescence, ELISA, and transcriptome sequencing. Potential underlying mechanisms were also explored. In vivo, OA was induced in rats via anterior cruciate ligament transection (ACLT), and GK's impact on cartilage protection was further assessed via histological analysis and western blot.

RESULTS

Network pharmacology has revealed that GK regulates OA via several key pathways, especially NF-κB, HIF-1, PI3K-AKT, and substances like reactive oxygen species. In vitro experiments showed GK effectively reverses oxidative stress damage from TBHP, inhibits inflammatory factor release, and protects Extracellular matrix (ECM) from degradation. These functions may be achieved via the NF-κB and MAPK signaling pathways. In vivo experiments showed GK significantly reduced proteoglycan loss from ACLT and inhibited matrix metalloproteinase 13 (MMP13) and ADAMTS5 (A disintegrin and metalloproteinase with thrombospondin motifs 5) production, effectively preventing cartilage degeneration in rats.

CONCLUSION

These findings suggest that GK has potential as a therapeutic agent for OA, offering new strategies and directions for OA treatment.

Homogeneous fluorescence immunoassay based on AuNPs (AgNPs) quenching multicolor QDs@hydrogel beads for the simultaneous ultra-sensitive determination of aflatoxin B1 and capsaicinoids in food

A capsaicinoids (CPCs) broad spectrum monoclonal antibody with same recognition ability to capsaicin (CPC), dihydrocapsaicin (DCPC), nordihydrocapsaicin (NDCPC), and N-vanillylnonanamide (NV) is prepared. Chitosan (CS) hydrogel is used as the carrier of multicolor quantum dots (QDs) to prepare fluorescence hydrogel beads, CPCs and aflatoxin B1 (AFB1) antibody are coupled with fluorescence hydrogel beads to prepare signal probes. Using AuNPs (or AgNPs) as fluorescence quenching agent to prepare quenching probes followed forming a fluorescence quenching test system. Based on optimal group of signal and quenching probes, a novel, simple, convenient, and ultra-sensitive homogeneous fluorescence immunoassay for the simultaneous detection of CPCs and AFB1 is constructed. The limit of detection (LOD) of assay for AFB1 and CPC is 0.00064 μg L-1 and 0.00049 μg L-1, respectively. This method can realize the simultaneous rapid detection of AFB1 and CPCs in food, which provides a new strategy for the identification of kitchen waste oil.

Mass production of ultrasmall Mn3O4 nanoparticles for glutathione responsive off-on T 1/T 2 switching magnetic resonance imaging and tumor theranostics

Individual theranostics with an integrated multifunction holds considerable promise for clinical application compared with multicomponent regimes. Mn3O4 nanoparticles with an ultrasmall size (4 nm) and mass production capability were developed with dual function of integrated tumor magnetic resonance imaging (MRI) and therapy. The high valence state of Mn3O4 nanocrystals enables a sensitive reaction with the glutathione (GSH) molecule and favorable decomposition ability, which further induces a unique, favorable, variable T 1 turn-off and T 2 turn-on MRI property. In addition, ultrasmall Mn3O4 nanoparticles reacted with high-level GSH in the tumor microenvironment induces responsive and enhanced variable T 1- and T 2-MRI imaging capability for accurate cancer diagnosis. Moreover, the synthesized ultrasmall Mn3O4 nanoparticles exhibit considerable ferroptosis effect towards tumor cells and excellent in vivo biocompatibility, thus indicating promising effective cancer treatment application. The developed ultrasmall Mn3O4 nanoparticles with integrated dual functions of GSH-responsive variable T 1 and T 2 MRI imaging effects and ferroptosis capability show promising potential as a candidate for tumor theranostics in clinical applications.

LDHzyme-assisted high-performance on-site tracking of levodopa pharmacokinetics for Parkinson's disease management

Parkinson's disease (PD) is a progressive neurodegenerative disorder marked by the loss of dopaminergic neurons and the consequent decline in motor and cognitive functions. The primary therapeutic agent levodopa necessitates precise dosing due to its narrow therapeutic window and complex pharmacokinetics. This study presents the development of a novel CuCoFe-LDHzyme-based sweat sensor for real-time monitoring of levodopa concentration in PD patients. Employing differential pulse voltammetry (DPV) technique, the sensor demonstrates high sensitivity and selectivity, achieving a detection limit of 28.1 nM. The sensor's design allows for non-invasive, continuous monitoring, significantly enhancing patient convenience compared to traditional blood sampling methods. Through pH correction, precise quantification of levodopa in sweat is accomplished, and a strong correlation (Pearson coefficient = 0.833) with blood levodopa levels is established. The pharmacokinetic profile of levodopa is reconstructed in real-time, offering a promising tool for optimizing PD treatment regimens. This study highlights the potential of CuCoFe-LDHzyme sensors to advance personalized treatment strategies, aiming to improve the quality of life for PD patients by providing clinicians with real-time data for medication adjustments.

METTL16 suppresses ferroptosis in cholangiocarcinoma by promoting ATF4 via m6A modification

Background: N6-methyladenosine (m6A) modification is the most common post-transcriptional modifications, which is critical for the metabolism of ferroptosis-related RNAs. Yet, the impact of m6A modification on ferroptosis in cholangiocarcinoma (CC) is far from clear. Methods: Public databases and tissue arrays were applied to explore the clinical relevance of METTL16 in CC. Then, the effects of METTL16 on growth and ferroptosis were studied in vitro and in vivo. Mechanistically, RNA-sequencing, methylated RNA immunoprecipitation, dual-luciferase reporter assays and RNA stability assays were used to identify the METTL16/ATF4 axis in ferroptosis in CC. Results: Clinically, we find that METTL16 is overexpressed and associated with a poor prognosis in patients with CC. Functionally, METTL16 protects against ferroptosis by maintaining mitochondrial homeostasis, including mitochondrial structure, membrane potential and energy products. It also decreases cellular metabolism of Fe2+ and lipid peroxide, thereby promoting cell growth in vitro and in vivo. Mechanistically, ATF4 is a novel target of METTL16 and METTL16 enhances the m6A level and expression of ATF4 mRNA by inhibiting its decay, which further prevented ferroptosis in CC via m6A modification. Conclusions: Our findings highlighted the role of METTL16/ATF4 in ferroptosis, which sheds light on potential therapeutic strategies for CC.

An intra articular injectable Mitocelle recovers dysfunctional mitochondria in cellular organelle disorders

Mitochondrial dysfunction increases ROS production and is closely related to many degenerative cellular organelle diseases. The NOX4-p22phox axis is a major contributor to ROS production and its dysregulation is expected to disrupt mitochondrial function. However, the field lacks a competitive inhibitor of the NOX4-p22phox interaction. Here, we created a povidone micelle-based Prussian blue nanozyme that we named "Mitocelle" to target the NOX4-p22phox axis, and characterized its impact on the major degenerative cellular organelle disease, osteoarthritis (OA). Mitocelle is composed of FDA-approved and biocompatible materials, has a regular spherical shape, and is approximately 88 nm in diameter. Mitocelle competitively inhibits the NOX4-p22phox interaction, and its uptake by chondrocytes can protect against mitochondrial malfunction. Upon intra-articular injection to an OA mouse model, Mitocelle shows long-term stability, effective uptake into the cartilage matrix, and the ability to attenuate joint degradation. Collectively, our findings suggest that Mitocelle, which functions as a competitive inhibitor of NOX4-p22phox, may be suitable for translational research as a therapeutic for OA and cellular organelle diseases related to dysfunctional mitochondria.

Lubricating and Dual-Responsive Injectable Hydrogels Formulated From ZIF-8 Facilitate Osteoarthritis Treatment by Remodeling the Microenvironment

Osteoarthritis (OA) is a progressively developing condition primarily characterized by the deterioration of articular cartilage and the proliferation of bone, along with ongoing inflammation. Although the precise pathogenesis remains somewhat elusive, restoring the homeostatic balance of the intra-articular microenvironment is crucial for the management of OA. Intra-articular injection of medication is one of the most direct and effective treatment methods; however, most injectable drugs used for osteoarthritis treatment, due to their rapid breakdown, quick release, poor biological activity, and frequent injections, leading to increased risk of infection and suboptimal therapeutic outcomes. In this study, a lubricating and dual-responsive injectable hydrogel based on zeolitic imidazolate frameworks-8 (ZIF-8) impregnated with Quercetin (Que) is designed, which can facilitate OA treatment by remodeling the microenvironment. The prepared injectable nanocomposite hydrogel (MH/CCM@ZIF-8@Que) exhibits pH and reactive oxygen species (ROS) responsiveness, alongside a controllable release of bioactive substances to modulate the microenvironment of bone tissue, thereby mitigating synovitis and the degeneration of cartilage matrix, while simultaneously facilitating cartilage repair. This developed thermosensitive injectable hydrogel, which effectively balances lubrication with the controlled release of bioactive substances, represents a highly promising therapeutic approach for osteoarthritis.

The recent research progress in the application of the nanozyme-hydrogel composite system for drug delivery

Hydrogels, comprising 3D hydrophilic polymer networks, have emerged as promising biomaterial candidates for emulating the structure of biological tissues and delivering drugs through topical administration with good biocompatibility. Nanozymes can catalyze endogenous biomolecules, thereby initiating or inhibiting in vivo biological processes. A nanozyme-hydrogel composite inherits the biological functions of hydrogels and nanozymes, where the nanozyme serves as the catalytic core and the hydrogel forms the structural scaffold. Moreover, the composite can concentrate nanozymes in targeted lesions and catalyze the binding of a specific group of substrates, resulting in pathological microenvironment remodeling and drug-penetrating barrier impairment. The composite also shields nanozymes to prevent burst release during catalytic production and reduce related toxicity. Currently, the application of these composites has been extended to antibacterial, anti-inflammatory, anticancer, and tissue repair applications. In this review, we elucidate the preparation methods for nanozyme-hydrogel composites, provide compelling evidence of their advantages in drug delivery and provide a comprehensive overview of their biological application.

Ultra-small platinum nano-enzymatic spray with ROS scavenging and anti-inflammatory properties for photoaging treatment

Photoaging induced by ultraviolet (UV) results in oxidative stress and inflammation. Noble metal nanozymes have strong antioxidant and anti-inflammatory capacity, which are expected to eliminate the excessive reactive oxygen species (ROS) and inflammatory factors in the photoaged skin. Hence, we have synthesized ultrasmall platinum nanoparticles coated with polyvinylpyrrolidone (Pt NPs) with a diameter of nearly 5 nm for photoaging treatment. Thanks to multi-enzymatic capacities (catalase, peroxidase, and superoxide dismutase) of Pt NPs, they can effectively protect fibroblasts from UV-induced ROS attack, relieve fibroblasts from UV-induced cell cycle arrest, downregulate matrix metalloproteinases (MMPs) to regenerate type I collagen, and inhibit M1 macrophage polarization to decrease the expression of inflammatory factors. For photoaged mice treatment, we employ the concept of routine spray skincare and encapsulate Pt NPs solution in a spray bottle. In combination with roller needle, following Pt NPs nano-enzymatic spray given, UV-induced photoaged mice display reduced wrinkle formation in the collagen-depleted dermal tissue of mice and more youthful performance in both appearance and organizational structure. Consequently, multi-enzymatic functions of Pt NPs nano-spray offers a promising avenue for anti-photoaging therapy, providing potential benefits in both preventative and restorative skincare applications.

Natural Polyphenol Delivered Methylprednisolone Achieve Targeted Enrichment for Acute Spinal Cord Injury Therapy

The strong anti-inflammatory effect of methylprednisolone (MP) is a necessary treatment for various severe cases including acute spinal cord injury (SCI). However, concerns have been raised regarding adverse effects from MP, which also severely limits its clinical application. Natural polyphenols, due to their rich phenolic hydroxyl chemical properties, can form dynamic structures without additional modification, achieving targeted enrichment and drug release at the disease lesion, making them a highly promising carrier. Considering the clinical application challenges of MP, a natural polyphenolic platform is employed for targeted and efficient delivery of MP, reducing its systemic side effects. Both in vitro and SCI models demonstrated polyphenols have multiple advantages as carriers for delivering MP: (1) Achieved maximum enrichment at the injured site in 2 h post-administration, which met the desires of early treatment for diseases; (2) Traceless release of MP; (3) Reducing its side effects; (4) Endowed treatment system with new antioxidative properties, which is also an aspect that needs to be addressed for diseases treatment. This study highlighted a promising prospect of the robust delivery system based on natural polyphenols can successfully overcome the barrier of MP treatment, providing the possibility for its widespread clinical application.

The effect of copper and vitamin D on osteoarthritis outcomes: A Mendelian randomization study

This study aimed to explore the causal relationship between trace elements and osteoarthritis (OA). The results showed a relatively weak association between copper and OA, while vitamin D showed a significant positive association with OA. Mendelian randomization (MR) analysis was used to investigate the causal relationship between copper and vitamin D and OA. A variety of MR methods including inverse variance weighting, weighted median, MR-Egger, simple model, and multi-text mixed model were analyzed to confirm the consistency of these results. Sensitivity analysis further confirmed the reliability of these causal relationships and excluded the interference of pleiotropy. These findings add to the understanding of the potential role of micronutrients in the prevention and treatment of OA and support the idea of vitamin D as a potential therapy for the prevention and treatment of OA. Future studies should further explore the specific biological mechanisms of these trace elements and the differences in their effects in different populations in order to develop more effective treatment strategies to reduce the health burden of degenerative joint diseases.

Ultrasmall Prussian Blue Nanozyme Attenuates Osteoarthritis by Scavenging Reactive Oxygen Species and Regulating Macrophage Phenotype

Osteoarthritis (OA) is a degenerative joint disease characterized by obscure etiology and unsatisfactory therapeutic outcomes, making the development of new efficient therapies urgent. Superfluous reactive oxygen species (ROS) have historically been considered one of the crucial factors inducing the pathological progression of OA. Ultrasmall Prussian blue nanoparticles (USPBNPs), approximately sub-5 nm in size, are developed by regulating the configuration of polyvinylpyrrolidone chains. USPBNPs display an excellent ROS eliminating capacity and catalase-like activity, capable of decomposing hydrogen peroxide (H2O2) into O2. The anti-inflammatory mechanism of USPBNPs can be attributed to repolarizing macrophages from pro-inflammatory M1 to anti-inflammatory M2 phenotype by decreasing the ROS levels accompanied by O2 improvement. Additionally, USPBNPs exhibit an exciting therapeutic efficiency against OA, comparable to that of hydrocortisone in vivo. This study not only develops a new therapeutic agent for OA but also offers an estimable insight into the application of the nanozyme.

The biomedical applications of nanozymes in orthopaedics based on regulating reactive oxygen species

Nanozymes, a category of nanomaterials with enzyme-like activity, have garnered growing interest in various biomedical contexts. Notably, nanozymes that are capable of regulating reactive oxygen species levels by emulating antioxidant or prooxidant enzymes within cells hold significant therapeutic potential for a range of disorders. Herein, we overview the catalytic mechanisms of four exemplary nanozymes within the orthopedic domain. Subsequently, we emphasize recent groundbreaking advancements in nanozyme applications in orthopaedics, encompassing osteoarthritis, osteoporosis, intervertebral disc degeneration, bone defects, spinal cord injury, gout, rheumatoid arthritis, osteosarcoma and bone infection. Furthermore, we discuss the emerging area's future prospects and several noteworthy challenges in biomedical application. This review not only fosters the ongoing development of nanozyme research but also fosters the emergence of more potent nanozymes for the treatment of orthopaedical diseases in the future.

Microenvironment-sensitive nanozymes for tissue regeneration

Tissue defect is one of the significant challenges encountered in clinical practice. Nanomaterials, including nanoparticles, nanofibers, and metal-organic frameworks, have demonstrated an extensive potential in tissue regeneration, offering a promising avenue for future clinical applications. Nonetheless, the intricate landscape of the inflammatory tissue microenvironment has engendered challenges to the efficacy of nanomaterial-based therapies. This quandary has spurred researchers to pivot towards advanced nanotechnological remedies for overcoming these therapeutic constraints. Among these solutions, microenvironment-sensitive nanozymes have emerged as a compelling instrument with the capacity to reshape the tissue microenvironment and enhance the intricate process of tissue regeneration. In this review, we summarize the microenvironmental characteristics of damaged tissues, offer insights into the rationale guiding the design and engineering of microenvironment-sensitive nanozymes, and explore the underlying mechanisms that underpin these nanozymes' responsiveness. This analysis includes their roles in orchestrating cellular signaling, modulating immune responses, and promoting the delicate process of tissue remodeling. Furthermore, we discuss the diverse applications of microenvironment-sensitive nanozymes in tissue regeneration, including bone, soft tissue, and cartilage regeneration. Finally, we shed our sights on envisioning the forthcoming milestones in this field, prospecting a future where microenvironment-sensitive nanozymes contribute significantly to the development of tissue regeneration and improved clinical outcomes.

Stem cell recruitment polypeptide hydrogel microcarriers with exosome delivery for osteoarthritis treatment

With the accelerated aging tendency, osteoarthritis (OA) has become an intractable global public health challenge. Stem cells and their derivative exosome (Exo) have shown great potential in OA treatment. Research in this area tends to develop functional microcarriers for stem cell and Exo delivery to improve the therapeutic effect. Herein, we develop a novel system of Exo-encapsulated stem cell-recruitment hydrogel microcarriers from liquid nitrogen-assisted microfluidic electrospray for OA treatment. Benefited from the advanced droplet generation capability of microfluidics and mild cryogelation procedure, the resultant particles show uniform size dispersion and excellent biocompatibility. Moreover, acryloylated stem cell recruitment peptides SKPPGTSS are directly crosslinked within the particles by ultraviolet irradiation, thus simplifying the peptide coupling process and preventing its premature release. The SKPPGTSS-modified particles can recruit endogenous stem cells to promote cartilage repair and the released Exo from the particles further enhances the cartilage repair performance through synergistic effects. These features suggest that the proposed hydrogel microcarrier delivery system is a promising candidate for OA treatment.

[Advances in the Application of Nanozymes in Joint Disease Therapy]

Nanozymes are nanoscale materials with enzyme-mimicking catalytic properties. Nanozymes can mimic the mechanism of natural enzyme molecules. By means of advanced chemical synthesis technology, the size, shape, and surface characteristics of nanozymes can be accurately regulated, and their catalytic properties can be customized according to the specific need. Nanozymes can mimic the function of natural enzymes, including catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx), to scavenge reactive oxygen species (ROS). Reported findings have shown that nanozymes have the advantages of excellent stability, low cost, and adjustable catalytic activity, thereby showing great potential and broad prospects in the application of disease treatment. Herein, we reviewed the advances in the application of nanozymes in the treatment of joint diseases. The common clinical manifestations of joint diseases include joint pain, swelling, stiffness, and limited mobility. In severe cases, joint diseases may lead to joint destruction, deformity, and functional damage, entailing crippling socioeconomic burdens. ROS is a product of oxidative stress. Increased ROS in the joints can induce macrophage M1 type polarization, which in turn induces and aggravates arthritis. Therefore, the key to the treatment of joint diseases lies in ROS scavenging and increasing oxygen (O2) content. Nanozymes have demonstrated promising application potential in the treatment of joint diseases, including rheumatoid arthritis, osteoarthritis, and gouty arthritis. However, how to ensure their biosafety, reduce the toxicity, and increase enzyme activity remains the main challenge in current research. Precise control of the chemical composition, size, shape, and surface modification of nanomaterials is the main development direction for the future.

Nano-enzyme hydrogels for cartilage repair effectiveness based on ternary strategy therapy

Designing artificial nano-enzymes for scavenging reactive oxygen species (ROS) in chondrocytes (CHOs) is considered the most feasible pathway for the treatment of osteoarthritis (OA). However, the accumulation of ROS due to the amount of nano-enzymatic catalytic site exposure and insufficient oxygen supply seriously threatens the clinical application of this therapy. Although metal-organic framework (MOF) immobilization of artificial nano-enzymes to enhance active site exposure has been extensively studied, artificial nano-enzymes/MOFs for ROS scavenging in OA treatment are still lacking. In this study, a biocompatible lubricating hydrogel-loaded iron-doped zeolitic imidazolate framework-8 (Fe/ZIF-8/Gel) centrase was engineered to scavenge endogenous overexpressed ROS synergistically generating dissolved oxygen and enhancing sustained lubrication for CHOs as a ternary artificial nano-enzyme. This property enabled the nano-enzymatic hydrogels to mitigate OA hypoxia and inhibit oxidative stress damage successfully. Ternary strategy-based therapies show excellent cartilage repair in vivo. The experimental results suggest that nano-enzyme-enhanced lubricating hydrogels are a potentially effective OA treatment and a novel strategy.

Lithium Promotes Osteogenesis via Rab11a-Facilitated Exosomal Wnt10a Secretion and β-Catenin Signaling Activation

Both bone mesenchymal stem cells (BMSCs) and their exosomes suggest promising therapeutic tools for bone regeneration. Lithium has been reported to regulate BMSC function and engineer exosomes to improve bone regeneration in patients with glucocorticoid-induced osteonecrosis of the femoral head. However, the mechanisms by which lithium promotes osteogenesis have not been elucidated. Here, we demonstrated that lithium promotes the osteogenesis of BMSCs via lithium-induced increases in the secretion of exosomal Wnt10a to activate Wnt/β-catenin signaling, whose secretion is correlated with enhanced MARK2 activation to increase the trafficking of the Rab11a and Rab11FIP1 complexes together with exosomal Wnt10a to the plasma membrane. Then, we compared the proosteogenic effects of exosomes derived from lithium-treated or untreated BMSCs (Li-Exo or Con-Exo) both in vitro and in vivo. We found that, compared with Con-Exo, Li-Exo had superior abilities to promote the uptake and osteogenic differentiation of BMSCs. To optimize the in vivo application of these hydrogels, we fabricated Li-Exo-functionalized gelatin methacrylate (GelMA) hydrogels, which are more effective at promoting osteogenesis and bone repair than Con-Exo. Collectively, these findings demonstrate the mechanism by which lithium promotes osteogenesis and the great promise of lithium for engineering BMSCs and their exosomes for bone regeneration, warranting further exploration in clinical practice.

Kirigami triboelectric spider fibroin microneedle patches for comprehensive joint management

Joint injuries are among the leading causes of disability. Present concentrations were focused on oral drugs and surgical treatment, which brings severe and unnecessary difficulties for patients. Smart patches with high flexibility and intelligent drug control-release capacity are greatly desirable for efficient joint management. Herein, we present a novel kirigami spider fibroin-based microneedle triboelectric nanogenerator (KSM-TENG) patch with distinctive features for comprehensive joint management. The microneedle patch consists of two parts: the superfine tips and the flexible backing base, which endow it with great mechanical strength to penetrate the skin and enough flexibility to fit different bends. Besides, the spider fibroin-based MNs served as a positive triboelectric material to generate electrical stimulation, thereby forcing drug release from needles within 720 min. Especially, kirigami structures could also transform the flat patch into three dimensions, which could impart the patch with flexible properties to accommodate the complicated processes produced by joint motion. Benefiting from these traits, the KSM-TENG patch presents excellent performance in inhibiting the inflammatory response and promoting wound healing in mice models. The results indicated that the mice possessed only 2% wound area and the paw thickness was reduced from 10.5 mm to 6.2 mm after treatment with the KSM-TENG patch, which further demonstrates the therapeutic effect of joints in vivo. Thus, it is believed that the proposed novel KSM-TENG patch is valuable in the field of comprehensive treatments and personalized clinical applications.

NIR-enhanced Pt single atom/g-C3N4 nanozymes as SOD/CAT mimics to rescue ATP energy crisis by regulating oxidative phosphorylation pathway for delaying osteoarthritis progression

Osteoarthritis (OA) progresses due to the excessive generation of reactive oxygen and nitrogen species (ROS/RNS) and abnormal ATP energy metabolism related to the oxidative phosphorylation pathway in the mitochondria. Highly active single-atom nanozymes (SAzymes) can help regulate the redox balance and have shown their potential in the treatment of inflammatory diseases. In this study, we innovatively utilised ligand-mediated strategies to chelate Pt4+ with modified g-C3N4 by π-π interaction to prepare g-C3N4-loaded Pt single-atom (Pt SA/C3N4) nanozymes that serve as superoxide dismutase (SOD)/catalase (CAT) mimics to scavenge ROS/RNS and regulate mitochondrial ATP production, ultimately delaying the progression of OA. Pt SA/C3N4 exhibited a high loading of Pt single atoms (2.45 wt%), with an excellent photothermal conversion efficiency (54.71%), resulting in tunable catalytic activities under near-infrared light (NIR) irradiation. Interestingly, the Pt-N6 active centres in Pt SA/C3N4 formed electron capture sites for electron holes, in which g-C3N4 regulated the d-band centre of Pt, and the N-rich sites transferred electrons to Pt, leading to the enhanced adsorption of free radicals and thus higher SOD- and CAT-like activities compared with pure g-C3N4 and g-C3N4-loaded Pt nanoparticles (Pt NPs/C3N4). Based on the use of H2O2-induced chondrocytes to simulate ROS-injured cartilage invitro and an OA joint model invivo, the results showed that Pt SA/C3N4 could reduce oxidative stress-induced damage, protect mitochondrial function, inhibit inflammation progression, and rebuild the OA microenvironment, thereby delaying the progression of OA. In particular, under NIR light irradiation, Pt SA/C3N4 could help reverse the oxidative stress-induced joint cartilage damage, bringing it closer to the state of the normal cartilage. Mechanistically, Pt SA/C3N4 regulated the expression of mitochondrial respiratory chain complexes, mainly NDUFV2 of complex 1 and MT-ATP6 of ATP synthase, to reduce ROS/RNS and promote ATP production. This study provides novel insights into the design of artificial nanozymes for treating oxidative stress-induced inflammatory diseases.

Mesoporous MOFs with ROS scavenging capacity for the alleviation of inflammation through inhibiting stimulator of interferon genes to promote diabetic wound healing

Excessive production of reactive oxygen species (ROS) and inflammation are the key problems that impede diabetic wound healing. In particular, dressings with ROS scavenging capacity play a crucial role in the process of chronic wound healing. Herein, Zr-based large-pore mesoporous metal-organic frameworks (mesoMOFs) were successfully developed for the construction of spatially organized cascade bioreactors. Natural superoxide dismutase (SOD) and an artificial enzyme were spatially organized in these hierarchical mesoMOFs, forming a cascade antioxidant defense system, and presenting efficient intracellular and extracellular ROS scavenging performance. In vivo experiments demonstrated that the SOD@HMUiO-MnTCPP nanoparticles (S@M@H NPs) significantly accelerated diabetic wound healing. Transcriptomic and western blot results further indicated that the nanocomposite could inhibit fibroblast senescence and ferroptosis as well as the stimulator of interferon genes (STING) signaling pathway activation in macrophages mediated by mitochondrial oxidative stress through ROS elimination. Thus, the biomimetic multi-enzyme cascade catalytic system with spatial ordering demonstrated a high potential for diabetic wound healing, where senescence, ferroptosis, and STING signaling pathways may be potential targets.

Anti-Stress and Anti-ROS Effects of MnOx-Functionalized Thermosensitive Nanohydrogel Protect BMSCs for Intervertebral Disc Degeneration Repair

Stem cell transplantation is proven to be a promising strategy for intervertebral disc degeneration (IDD) repair. However, replicative senescence of bone marrow-derived mesenchymal stem cells (BMSCs), shear damage during direct injection, mechanical stress, and the reactive oxygen species (ROS)-rich microenvironment in degenerative intervertebral discs (IVDs) cause significant cellular damage and limit the therapeutic efficacy. Here, an injectable manganese oxide (MnOx)-functionalized thermosensitive nanohydrogel is proposed for BMSC transplantation for IDD therapy. The MnOx-functionalized thermosensitive nanohydrogel not only successfully protects BMSCs from shear force and mechanical stress before and after injection, but also repairs the harsh high-ROS environment in degenerative IVDs, thus effectively increasing the viability of BMSCs and resident nucleus pulposus cells (NPCs). The MnOx-functionalized thermosensitive nanohydrogel provides mechanical protection for stem cells and helps to remove endogenous ROS, providing a promising stem cell delivery platform for the treatment of IDD.

Using Cu-Based Metal-Organic Framework as a Comprehensive and Powerful Antioxidant Nanozyme for Efficient Osteoarthritis Treatment

Developing nanozymes with effective reactive oxygen species (ROS) scavenging ability is a promising approach for osteoarthritis (OA) treatment. Nonetheless, numerous nanozymes lie in their relatively low antioxidant activity. In certain circumstances, some of these nanozymes may even instigate ROS production to cause side effects. To address these challenges, a copper-based metal-organic framework (Cu MOF) nanozyme is designed and applied for OA treatment. Cu MOF exhibits comprehensive and powerful activities (i.e., SOD-like, CAT-like, and •OH scavenging activities) while negligible pro-oxidant activities (POD- and OXD-like activities). Collectively, Cu MOF nanozyme is more effective at scavenging various types of ROS than other Cu-based antioxidants, such as commercial CuO and Cu single-atom nanozyme. Density functional theory calculations also confirm the origin of its outstanding enzyme-like activities. In vitro and in vivo results demonstrate that Cu MOF nanozyme exhibits an excellent ability to decrease intracellular ROS levels and relieve hypoxic microenvironment of synovial macrophages. As a result, Cu MOF nanozyme can modulate the polarization of macrophages from pro-inflammatory M1 to anti-inflammatory M2 subtype, and inhibit the degradation of cartilage matrix for efficient OA treatment. The excellent biocompatibility and protective properties of Cu MOF nanozyme make it a valuable asset in treating ROS-related ailments beyond OA.

Ferrous/Ferric Ions Crosslinked Type II Collagen Multifunctional Hydrogel for Advanced Osteoarthritis Treatment

Osteoarthritis (OA) is a highly prevalent and intricate degenerative joint disease affecting an estimated 500 million individuals worldwide. Collagen-based hydrogels have sparked immense interest in cartilage tissue engineering, but substantial challenges persist in developing biocompatible and robust crosslinking strategies, as well as improving their effectiveness against the multifaceted nature of OA. Herein, a novel discovery wherein the simple incorporation of ferrous/ferric ions enables efficient dynamic crosslinking of type II collagen, leading to the development of injectable, self-healing hydrogels with 3D interconnected porous nanostructures, is unveiled. The ferrous/ferric ions crosslinked type II collagen hydrogels demonstrate exceptional physical properties, such as significantly enhanced mechanical strength, minimal swelling ratios, and remarkable resistance to degradation, while also exhibiting extraordinary biocompatibility and bioactivity, effectively promoting cell proliferation, adhesion, and chondrogenic differentiation. Additionally, the hydrogels reveal potent anti-inflammatory effects by upregulating anti-inflammatory cytokines while downregulating pro-inflammatory cytokines. In a rat model of cartilage defects, these hydrogels exhibit impressive efficacy, substantially accelerating cartilage tissue regeneration through enhanced collagen deposition and increased proteoglycan secretion. The innovative discovery of the multifunctional role of ferrous/ferric ions in endowing type II collagen hydrogels with a myriad of beneficial properties presents exciting prospects for developing advanced biomaterials with potential applications in OA.

Organic-inorganic composite hydrogels: compositions, properties, and applications in regenerative medicine

Hydrogels, formed from crosslinked hydrophilic macromolecules, provide a three-dimensional microenvironment that mimics the extracellular matrix. They served as scaffold materials in regenerative medicine with an ever-growing demand. However, hydrogels composed of only organic components may not fully meet the performance and functionalization requirements for various tissue defects. Composite hydrogels, containing inorganic components, have attracted tremendous attention due to their unique compositions and properties. Rigid inorganic particles, rods, fibers, etc., can form organic-inorganic composite hydrogels through physical interaction and chemical bonding with polymer chains, which can not only adjust strength and modulus, but also act as carriers of bioactive components, enhancing the properties and biological functions of the composite hydrogels. Notably, incorporating environmental or stimulus-responsive inorganic particles imparts smartness to hydrogels, hence providing a flexible diagnostic platform for in vitro cell culture and in vivo tissue regeneration. In this review, we discuss and compare a set of materials currently used for developing organic-inorganic composite hydrogels, including the modification strategies for organic and inorganic components and their unique contributions to regenerative medicine. Specific emphasis is placed on the interactions between the organic or inorganic components and the biological functions introduced by the inorganic components. The advantages of these composite hydrogels indicate their potential to offer adaptable and intelligent therapeutic solutions for diverse tissue repair demands within the realm of regenerative medicine.

Construction of Mn-N-C nanoparticles with multienzyme-like properties and photothermal performance for the effective treatment of bacterial infections

In this work, we successfully constructed Mn-coordinated nitrogen-carbon nanoparticles (Mn-N-C NPs) exhibiting multienzyme-like activities. In a bacterial infectious microenvironment, the POD-like and OXD-like activities of Mn-N-C NPs could synergistically trigger the generation of ROS (˙OH and O2˙-), causing oxidative damage to the bacterial cell membrane for killing bacteria. Alternatively, in neutral or weak alkaline normal tissues, the excessive O2˙- could be converted into O2 and H2O2via the SOD-like ability of Mn-N-C NPs, and subsequently their CAT-like activity catalyzed excess H2O2 into H2O and O2 for protecting normal cells through the antioxidant defense. Mn-N-C NPs also possessed a good NIR-photothermal performance, which could enhance their POD-like and OXD-like activities. Furthermore, Mn-N-C NPs could facilitate the GSH oxidation process and disrupt the intrinsic balance in the bacterial protection microenvironment with the assistance of H2O2, which is beneficial for rapid bacterial death. Undoubtedly, the Mn-N-C NPs + H2O2 system showed the highest antibacterial activity when irradiated with an 808 nm laser, destroying the bacterial membrane and causing the efflux of proteins. Moreover, the Mn-N-C NPs + H2O2 system was immune to the development of bacterial resistance and could efficiently disrupt the formation of a bacterial biofilm with negligible cytotoxicity and low hemolysis ratio. Finally, Mn-N-C NPs exhibited an excellent antibacterial performance in vivo and could accelerate wound healing without cellular inflammation production. Therefore, due to their significant therapeutic effects, Mn-N-C NPs show great potential in fighting antibiotic-resistant bacteria.

Paroxetine Attenuates Chondrocyte Pyroptosis and Inhibits Osteoclast Formation by Inhibiting NF-κB Pathway Activation to Delay Osteoarthritis Progression

Background

Osteoarthritis (OA), a common chronic joint disease, is characterized by cartilage degeneration and subchondral bone reconstruction. NF-κB signaling pathway-activated inflammation and NLRP3-induced pyroptosis play essential roles in the development of OA. In this study, we examine whether paroxetine can inhibit pyroptosis and reduce osteoclast formation, thereby delaying the destruction of knee joints.

Methods

We employed high-density cultures, along with quantitative polymerase chain reactions and Western blotting techniques, to investigate the effects of paroxetine on extracellular matrix synthesis and degradation. The expression levels of NF-κB and pyroptosis-related signaling pathway proteins were examined by Western blotting and immunofluorescence. Furthermore, the impact of paroxetine on RANKL-induced osteoclast formation was evaluated through TRAP staining and F-actin ring fluorescence detection. To investigate the role of paroxetine in vivo, we constructed a mouse model with destabilization of the medial meniscus (DMM) surgery. Safranin O-Fast Green staining, Hematoxylin-Eosin staining, and immunohistochemistry were conducted to observe the extent of knee joint cartilage deformation. In addition, TRAP staining was used to observe the formation of osteoclasts in the subchondral bone.

Results

In the in vitro experiments with ATDC5, paroxetine treatment attenuated IL-1β-induced activation of the pyroptosis-related pathway and suppressed extracellular matrix catabolism by inhibiting the NF-kB signaling pathway. In addition, paroxetine treatment decreased the expression of RANKL-induced osteoclast marker genes and reduced osteoclast formation. In animal experiments conducted in vivo, mice treated with paroxetine exhibited thicker knee cartilage with a smoother surface compared to the DMM group. Additionally, the formation of osteoclasts in the subchondral bone was reduced in the paroxetine-treated mice. Further analysis revealed that paroxetine treatment played a role in preserving the balance of the extracellular matrix and delaying knee joint degeneration.

Conclusion

Paroxetine can inhibit pyroptosis and reduce osteoclast formation via inhibiting the NF-κB signaling pathway, suggesting that it may have therapeutic effects in patients with OA.