Injectable hydrogel microspheres with self-renewable hydration layers alleviate osteoarthritis

Cascade targeting selenium nanoparticles-loaded hydrogel microspheres for multifaceted antioxidant defense in osteoarthritis

Selenium (Se) deficiency is a critical factor contributing to the imbalance of redox homeostasis in chondrocytes and the progression of osteoarthritis (OA). However, traditional selenium supplements face challenges such as a narrow therapeutic window and lack of targeting. To address this, we designed hyaluronic acid (HA)-modified selenium nanoparticles (HA-SeNPs) and developed a cascade-targeted delivery system (HA-SeNPs@AHAMA-HMs) based on a nano-micron combined strategy. The system involves loading HA-SeNPs into aldehyde-functionalized hydrogel microspheres prepared via microfluidic technology. Through Schiff base reactions between the aldehyde groups of the microspheres and amino groups of the cartilage, the system selectively adheres to the surface of damaged cartilage, achieving micron-scale targeting while continuously releasing HA-SeNPs. Then, HA-SeNPs achieve nanoscale targeting by binding to CD44, which is highly expressed on OA chondrocyte membranes, via their HA surface. Once taken up by the cells, HA-SeNPs exert their effects by directly scavenging ROS and promoting selenoprotein synthesis through the generation of selenite, forming a multifaceted antioxidant defense system. This effectively alleviates oxidative stress and optimizes mitochondrial function. In vivo and in vitro results demonstrated that this system significantly improved the oxidative phosphorylation pathway associated with mitochondrial function, which markedly reduced joint space narrowing and cartilage matrix degradation, and delayed the progression of OA. In summary, this study suggests that the cascade-targeting hydrogel microspheres designed and constructed based on a nano-micron combined strategy represent a promising prospective approach for precise Se supplementation and OA treatment.

MXene-Based Cartilage-Adhesive Microspheres for Photothermal-Controlled Hydrophobic Drug Release and Mesenchymal Stem Cell Delivery in Osteoarthritis

Intra-articular drug injection is an effective treatment for osteoarthritis (OA). However, the rapid clearance of drugs from the joint cavity results in low drug utilization and suboptimal therapeutic outcomes. This study describes MXene-based cartilage-adhesive microspheres for photothermal-controlled hydrophobic drug release and bone marrow mesenchymal stem cell (BMSC) delivery. Nano cationic amylose (NCA) was obtained by modifying amylose with glycidyltrimethylammonium chloride (GTAC), and hydrophobic drug Kartogenin (KGN) was encapsulated in the hydrophobic helical cavity of NCA through ultrasonic treatment, resulting in nano cationic amylose@KGN complexes (NCA@KGN). HAMA/MXene-NCA@KGN (H/M-NCA@KGN) microspheres were prepared using a microfluidic device. These microspheres exhibited excellent biocompatibility, effectively adhered to the cartilage surface, and carried BMSCs. H/M-NCA@KGN microspheres demonstrated photothermal-controlled release of the hydrophobic drug KGN. Notably, KGN promoted the differentiation of BMSCs into chondrocytes, thereby improving the loss of extracellular matrix in joint cartilage. Additionally, appropriate thermal stimulation induced the expression of heat shock protein 70 (HSP70) in OA chondrocytes, providing a protective effect and delaying the progression of OA. H/M-NCA@KGN microspheres enable controlled hydrophobic drug release and stem cell delivery for potential OA treatment applications.

Injectable Endoplasmin-Loaded Lipid Nanoparticles-Hydrogel Composite for Cartilage Regeneration

BACKGROUND

Endoplasmin (ENPL), a heat shock protein 90 family member, promotes chondrogenic differentiation of stem cells by inhibiting ERK1/2 phosphorylation and inducing endoplasmic reticulum stress. However, its large size limits cellular uptake and therapeutic potential. To overcome this challenge, a cationic lipid nanoparticle (C_LNP) system was designed to deliver ENPL intracellularly, enhancing its effects on human tonsil-derived mesenchymal stem cells (hTMSCs).

METHODS

ENPL-loaded cationic lipid nanoparticles (ENPL_C_LNP) were synthesized to facilitate intracellular ENPL delivery. The delivery efficiency and cytotoxicity were assessed in vitro using hTMSCs. Additionally, ENPL_C_LNPs were incorporated into a hyaluronic acid and chondroitin sulfate-based injectable hydrogel and tested for chondrogenic differentiation potential in a mouse subcutaneous model.

RESULTS

ENPL_C_LNP achieved over 80% intracellular protein delivery efficiency with no cytotoxic effects. Co-cultured hTMSCs exhibited increased glycosaminoglycans (GAGs) and collagen expression over 21 days. In vivo, the hydrogel-embedded ENPL_C_LNP system enabled stable cartilage differentiation, evidenced by abundant cartilage-specific lacuna structures in regenerated tissue.

CONCLUSION

Combining ENPL_C_LNP with an injectable hydrogel scaffold supports chondrogenic differentiation and cartilage regeneration, offering a promising strategy for cartilage tissue engineering.

MXene-Based Photothermal-Responsive Injectable Hydrogel Microsphere Modulates Physicochemical Microenvironment to Alleviate Osteoarthritis

Osteoarthritis (OA) is a physical lubrication microenvironment-inadequate disease accompanied by a sustained chronic chemical inflammation microenvironment and the progression of articular cartilage destruction. Despite the promising OA treatment outcomes observed in the enhancement of lubrication inspired by ball bearings to reduce friction and support loads, the therapeutic effect of near-infrared (NIR) irradiation-based photothermal-responsive controlled release "smart hydrogel microspheres" on OA remains unclear. Here, we prepared MXene/NIPIAM-based photothermal-responsive injectable hydrogel microspheres encapsulating diclofenac sodium using a microfluidic system. Consequently, NIR irradiation-based photothermal-responsive controlled release "smart hydrogel microspheres" demonstrate beneficial therapeutic effects in the treatment of OA by modulating the physical lubrication and chemical chronic inflammation microenvironment, laying the foundation for the application of smart hydrogel microsphere delivery systems loaded with bioactive factors (including agents, cells, and factors) to regulate multiple pathological microenvironments in regenerative medicine.

Microenvironment-sensitive hydrogels as promising drug delivery systems for co-encapsulating microbial homeostasis probiotics and anti-inflammatory drugs to treat periodontitis

Developing and utilizing effective local antimicrobial agents can help treat periodontitis while minimizing the risks associated with systemic antibiotic use. Recent studies have shown that the mucosal adhesion properties of hydrogels can play a potential role in the treatment of periodontitis. The hydrogel can improve the contact and retention time of drugs in the periodontal pocket. Through the adhesion of mucosa, it interacts with the mucin coating surface of epithelium and teeth to form a specific interface force. The hydrogel exhibits strong mucosal adhesion (adhesion strength: 5-6 N/cm2) and prolonged retention in periodontal pockets (≥6 h), enabling sustained drug release through dynamic sol-gel transitions triggered by pH and reactive oxygen species (ROS). This design overcomes the limitations of poor mechanical stability in conventional formulations. The dynamic balance of oral microbiota plays an important role in maintaining oral health. Probiotics, by colonizing the oral cavity, transform the infected site from an environment rich in inflammatory cytokines to a more benign environment, inhibit harmful pathogenic microorganisms, and contribute to overall health. Microenvironment sensitive hydrogels can perform dynamic sol gel transformation in situ, and can accurately control drug release when exposed to various stimuli (such as temperature change, light, pH change, reactive oxygen species, etc.). Oral probiotics and anti-inflammatory drugs are encapsulated in hydrogels to inhibit the proliferation and adhesion of oral pathogens by planting in the mouth and producing metabolites, effectively preventing and treating oral diseases.

Injectable Hydrogels Based on Hyperbranched Polymers for Biomedical Applications

Injectable hydrogels (IHs) have garnered significant attention in biomedical applications due to their minimally invasive nature, adaptability, and high degree of customization. However, traditional design methods of IHs have limitations in addressing complex clinical needs, such as precise regulation of the gelation time and mechanical strength within a wide window. Hyperbranched polymers (HBPs), due to their unique highly branched structures and abundant functional sites, can be easily prepared and functionalized to enable decoupled modulation of mechanical properties of IHs and address the clinical challenges of IHs. Our research group developed a library of HBPs via a dynamically controllable polymerization method and built a series of adjustable, controllable, and responsive IHs based on the resulting HBPs. The prepared IHs fed by HBPs demonstrate an adjustable gelation process, a wide-range tuning of mechanical properties, and responsiveness on demand, which show the capabilities in the various biomedical applications. In this review, we summarize the role of HBPs in the gelation process, mechanical properties, self-healing ability, and responsiveness of IHs. However, achieving IHs through HBPs and extending them to a broad range of biomedical applications are still in its infancy. This review provides an overview of IHs fabricated by a variety of multifunctional HBPs, and their biomedical applications in diverse fields are also presented. Meanwhile, we point out the future development of IHs based on HBPs and their potential challenges.

PEGNB-Heparin-Liposome composite hydrogels for in situ spraying and ultra-fast adhesion: meeting the challenges of endothelial repair of vascular injury

Carotid atherosclerosis is an essential cause of transient cerebral ischemia, stroke, and other cerebrovascular diseases, and carotid endarterectomy (CEA) is currently the most effective treatment for removing plaque and restoring the vascular lumen. However, the CEA disrupts the integrity and functionality of the endothelium and predisposes it to complications such as restenosis and thrombosis. Hydrogels can closely mimic the natural extracellular matrix, allowing a wide tuning of physical and chemical properties. These properties make hydrogels the most promising candidate materials for the repair of vascular injured intima. In this study, a multifunctional intimal repair hydrogel of poly(ethylene glycol)-norbornene (PEGNB)/ Heparin/ Liposome is proposed with the advantages of ultra-rapid adhesion to the wet tissue of the vascular inner wall, maintenance of adhesion stability under continuous erosion by blood flow. The hydrogel was supplemented with poly(vinyl butyral) (PVB) to reduce its swelling rate, and Rapamycin (RAPA) was encapsulated in this study as the drug into the cationic liposomes. This composite multifunctional (PNHB@Lip(RAPA)) hydrogel has exhibited outstanding anti-coagulation properties, markedly suppressed the proliferation and migration of SMCs, and displayed favourable cytocompatibility and blood compatibility. Concurrently, the capacity of the PNHB@Lip(RAPA) hydrogel to stimulate endovascular regeneration and deter restenosis and thrombus formation was validated through carotid intima damage repair experiments. These findings collectively indicate that the PNHB@Lip(RAPA) hydrogel represents a promising material for intimal injury repair, offering innovative insights into intimal repair methodologies. STATEMENT OF SIGNIFICANCE: Carotid atherosclerosis is a leading cause of transient cerebral ischemia, stroke, and cerebrovascular disorders. Although carotid endarterectomy (CEA) effectively removes plaques, it damages endothelial integrity, increasing the risk of restenosis and thrombosis. To address this, we developed PNHB@Lip(RAPA), a multifunctional intimal repair hydrogel composed of PEGNB, heparin, and rapamycin-encapsulated liposomes. This hydrogel rapidly adheres to wet vascular walls, resists blood flow erosion, and exhibits low swelling. The hydrogel demonstrates superior anticoagulation, inhibits smooth muscle cell proliferation and migration, and shows favourable cytocompatibility. Experimental results confirm its ability to promote endovascular regeneration while preventing restenosis and thrombosis. In summary, PNHB@Lip(RAPA) hydrogel is a promising material for intimal repair, offering innovative solutions to improve CEA postoperative outcomes.

Liposomic lubricants suppress acute inflammatory gene regulation in the joint in vivo

Osteoarthritis (OA) is a widespread, debilitating joint disease associated with articular cartilage degradation. It is driven via mechano-inflammatory pathways, whereby catabolic genes in the cartilage-embedded chondrocytes are presumed up-regulated due to increased shear stress arising from friction at the cartilage surface as joints articulate. The enhanced expression of these cartilage-degrading and inflammatory genes leads to tissue degeneration. However, the nature of the stress, and how the cells within the joint respond to it, are poorly understood. Here we show, in a proof of concept study on a mouse model where surgical joint destabilisation has been carried out to induce OA, that the early up-regulation of the matrix metalloproteinase 3 (Mmp3) gene, a member of the matrix-degrading MMP family, and of the interleukin-1 beta (Il1b) gene, a key mediator of inflammatory response, are significantly suppressed when lipid-based lubricants are injected into the joints. We attribute this to the reduction in frictional stress on the chondrocytes due to the lubricant at the cartilage surface. At the same time, Timp1, a compression but not shear-stress sensitive gene, is unaffected by lubricant. Our results demonstrate that cartilage lubrication modulates catabolic gene regulation in OA, shed strong light on the nature of the chondrocytes' response to shear stress, and have clear implications for novel OA treatments. STATEMENT OF SIGNIFICANCE: Osteoarthritis (OA) is a widespread, debilitating joint disease associated with degradation of the articular cartilage, the tissue that covers and protects the joint surfaces as they rotate. Such degradation is due to catabolic enzymes expressed by cartilage-embedded chondrocytes (the only cell type in cartilage) in response to mechanical stress. In this proof-of-concept study in a mouse OA model, we show that reduction of cartilage friction by liposome-based lubricants suppresses the production of the catabolic, OA-related genes in chondrocytes. Our findings provide direct evidence in an animal model that catabolic genes are induced in chondrocytes in a mechanosensitive manner, related to the friction at the cartilage surface, and identify putative novel OA treatments through efficient cartilage lubrication.

Poly-T-Modified Gold Nanorods Suppress Macrophage-Mediated Inflammation for Periodontitis Therapy

Traditional treatments for periodontitis are limited by their inability to adequately modulate the immune response and control inflammation. Recently, nucleic acid-modified nanomaterials have attracted significant attention for their potential in regulating inflammation. Among these, most nanomaterials, such as spherical nucleic acids, tend to exhibit pro-inflammatory effects. In this study, we identified for the first time that poly-T sequence-modified gold nanorods (PTM AuNRs) possess significant anti-inflammatory properties. The PTM AuNRs demonstrated excellent biocompatibility and efficacy in treating ligation-induced periodontitis. PTM AuNRs modulate immune responses by inhibiting the differentiation of pro-inflammatory M1 macrophages and reducing pro-inflammatory cytokine levels through promoting AMPK activation. When administered via local injection, PTM AuNRs effectively suppress inflammatory response and inflammatory cell infiltration, downregulate inflammatory cytokine levels, and mitigate collagen fiber degradation and alveolar bone loss. Together, these findings highlight PTM AuNRs as a promising and innovative therapeutic strategy for periodontitis management.

The preparation of silk fibroin-based hydrogels and their applications in cartilage repair

With the social development, the number of patients with osteoarthritis (OA) is increasing year by year, making it crucial to explore novel therapies and treatments to facilitate cartilage repair. Among these, hydrogels have become a center of conversation as potential cartilage substitutes in view of their swelling capacity, mechanical properties, lubricating performance, and other characteristics similar with that of extracellular matrix of articular cartilage. Therefore, it is of important values to generate multi-functional hydrogels with various bioactive materials for cartilage repair. As a natural fibrous protein known for its wonderful biocompatibility, degradability, as well as mechanical strength, silk fibroin (SF) with collagen-like structure has been widely applied in cartilage repair. Therefore, utilizing SF to construct hydrogels through various crosslinking methods shows greater application potential in cartilage repair and the treatment of OA. Besides having the benefits of both SF and hydrogels, the resulting SF-based hydrogels can further load various drugs, growth factors, stem cells, etc., so as to effectively promote cartilage repair. This review summarized the construction methods of SF-based hydrogels and the research progress in cartilage repair. The future development for SF-based hydrogels in cartilage repair was also discussed, which lay the foundation for further treatment of OA.

Localized Hydrogel Microspheres for Osteoarthritis Treatment: Recruitment and Differentiation of Stem Cells

Osteoarthritis (OA) represents a common degenerative joint disorder marked by progressive cartilage degradation, necessitating innovative therapeutic approaches beyond symptom management. Here, this study introduces a novel strategy leveraging the regenerative capabilities of mesenchymal stem cells (MSCs) by utilizing a bioactive extracellular matrix (ECM) derived from IFN-γ-stimulated MSCs, encapsulated within aldehyde- and methacrylic anhydride-modified hyaluronic acid hydrogel microspheres (AH). This engineered scaffold effectively mimics the native cartilage microenvironment, promoting targeted adhesion and retention at damaged sites via spontaneous Schiff base reactions. Notably, the IFN-γ-ECM@AH microspheres facilitate the localized release of key chemokines, such as CXCL12, enhancing endogenous stem cell recruitment, and bioactive factors (e.g., TGF-βI and TGF-β3) to drive chondrogenic differentiation. Additionally, the scaffold possesses binding sites for cellular integrins, further augmenting the regenerative potential of stem cells. Collectively, the approach presents a dual-action mechanism that supports efficient cartilage repair and regeneration, positioning this engineered microenvironment as a promising therapeutic avenue for OA and potentially other degenerative conditions.

Hyaluronic acid composite hydrogel with enhanced lubrication and controllable drug release for the mitigation of osteoarthritis

Excessive inflammation, overexpressed reactive oxygen species (ROS), degradation of the extracellular matrix, and high friction aggravate osteoarthritis (OA). Intra-articular injection for local drug delivery in the joint cavity enhances drug retention duration for OA treatment. Nevertheless, it remains a challenge to attenuate OA by thoroughly modulating the joint microenvironment, achieving controlled drug release, and enhancing lubrication. This study develops hyaluronic acid (HA) composite hydrogels, infused with gelatin microspheres containing a drug, utilizing dynamic interactions between phenylboronic acid and catechol to modulate the microenvironment by scavenging ROS, facilitating controlled drug release, and improving lubrication to mitigate OA. The composite hydrogels can be injected by intra-articular injection due to the shear-thinning properties, demonstrating broad ROS scavenging capacity and matrix metalloproteinase-9 responsive drug release. Both the in vitro and in vivo experiments prove the protective efficacy of the composite hydrogels against the degradation of cartilage matrix. Additionally, the hydrogels can offer efficient lubrication and effectively attenuate OA. Thus, the injectable HA composite hydrogels demonstrated potential in the management of OA.

LA-peptide Hydrogel-Regulation of macrophage and fibroblast fates and their crosstalk via attenuating TGF-β to promote scarless wound healing

The homeostasis of the wound microenvironment is fundamental for scarless wound healing, while the excessive accumulation of transforming growth factor-beta (TGF-β) in the wound microenvironment always leads to hypertrophic scars (HS) formation by regulating cell fates and crosstalk among various types of cells, such as macrophages and fibroblasts. This study reports that an injectable, self-assembling LA-peptide hydrogel has the potential to facilitate scarless cutaneous wound healing through dynamically adsorbing TGF-β within the wound environment. We found that the released LA peptides led to the suppression of both the PI3K/Akt and TGF-β/Smad2/3 pathways in macrophages and fibroblasts. As expected, the application of LA-peptide hydrogel alleviated the M2 type polarization of macrophages and inhibited fibroblasts activation by adsorbing TGF-β both in vitro and in vivo. Furthermore, designated concentrations of the LA-peptide hydrogel achieved controlled release of LA peptides, enabling dynamic regulation of TGF-β for maintaining microenvironment homeostasis during different phases of wound healing. This contributed to the inhibition of HS formation without delaying wound healing in both a mouse full-thickness skin wound model and a rabbit ear scar model. Overall, the LA-peptide hydrogel provides promising avenues for promoting scarless healing of wounds, exemplifying precision medicine-guided targeting of specific pathogenic molecules, such as TGF-β, and highlighting the significance of dynamic regulation of TGF-β homeostasis in wound microenvironment.

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.

Injectable Hydrogel Technologies for Bone Disease Treatment

Injectable hydrogels represent a highly promising approach for localized drug delivery systems (DDSs) in the management of bone-related conditions such as osteoporosis, osteonecrosis, osteoarthritis, osteomyelitis, and osteosarcoma. Their appeal lies in their biocompatibility, adjustable mechanical properties, and capacity to respond to external stimuli, including pH, temperature, light, redox potential, ionic strength, and enzymatic activity. These features enable enhanced targeted delivery of bioactive agents. This mini-review evaluates the synthesis of injectable hydrogels as well as recent advancements for treating a range of bone disorders, focusing on their mechanisms as localized and sustained DDSs for delivering drugs, nanoparticles, growth factors, and cells (e.g., stem cells). Moreover, it highlights their clinical studies for bone disease treatment. Additionally, it emphasizes the potential synergy between injectable hydrogels and hydrogel-based point-of-care technologies, which are anticipated to play a pivotal role in the future of bone disease therapies. Injectable hydrogels have the potential to transform bone disease treatment by facilitating precise, sustained, and minimally invasive therapeutic delivery. Nevertheless, significant challenges, including long-term biocompatibility, scalability, reproducibility, and precise regulation of drug release kinetics, must be addressed to unlock their clinical potential fully. Addressing these challenges will not only advance bone disease therapy but also open new avenues in regenerative medicine and personalized healthcare.

Straightforward Approach Toward Thermo-Sensitive Hydrogel Coating on Polyethersulfone Membranes with Controlled Drug Delivery for Significant Inhibition of Thrombocytopenia During Hemodialysis

Thrombocytopenia is a potential complication associated with hemodialysis due to the unsatisfactory hemocompatibility of current dialysis membranes, which leads to excessive platelet destruction, accelerates organ failure, and threatens the patients' life safety in severe cases. In the clinical application of hemodialysis, there are a proportion of patients suffer thrombocytopenia. For these patients, heparin combined with tirofiban can be used during dialysis to suppress the occurrence of thrombocytopenia, but the medication requires intravenous injection and continuous infusion. To optimize the application of hemodialysis membranes, a dialysis membrane composed of polyethersulfone (PES) base membrane and a temperature-sensitive hydrogel coating poly (N-acryloyl glycinamide) (PNAGA) is designed, and prepared that can continuously release tirofiban through temperature control to reduce the burden of medication on patients and significantly inhibit the occurrence of thrombocytopenia. The resulting membrane exhibits an encapsulation efficiency of 36.2% (72.4 µg mL-1) for tirofiban, with drug release rates of 54.83% at 37 °C and 31.4% at 4 °C after 1 h. Additionally, the membrane shows excellent hydrophilicity and dialysis performance. It also effectively inhibits platelet adhesion (reduced by 92.3%), activation (reduced by 92.8%) and aggregation, and albumin adsorption (reduced by 84.7%). In summary, the work provides a new solution for the preparation of dialysis membranes that can prevent thrombocytopenia, which has potential applications in the safer hemodialysis membrane manufacturing sector.

Recent development in friction of supramolecular gel lubricant: from mechanisms to applications

Due to the unique self-assembling structure and rheological properties, supramolecular gel lubricants have become the third major type of liquid lubricating materials to supplement the lubricating oils and greases. The molecular structures of gelators applicable to oil-based, water-based and extreme conditions base oils were summarized firstly. Furthermore, this review aims at exploring the relationships between the molecular structures of gelators and the gel-forming, rheological and tribological properties of gel lubricants. Based on the wide application of gel in various lubrication fields, the synergistic lubricating effect between gel lubricants and nanomaterials, films, textured surfaces were analyzed. The design of solid-liquid composite lubrication systems based on gel lubricants and solid lubricants were attempted to be highlighted and revealed. Finally, the perspectives on the development of gel lubricants and corresponding composite lubricating materials were presented.

Liposome-Based Interventions in Knee Osteoarthritis

Osteoarthritis (OA) is the most common degenerative disease of the joints, causing significant disability and socio-economic burden in the aging population. Simultaneously, however, it is a common occurrence in younger individuals, initiated by joint injuries or obesity alongside other factors. Intravenous and oral pharmaceutical OA management have both been associated with systemic adverse effects, thereby resulting in a growing interest in intra-articular (IA) treatment. IA-administered drugs circumvent the requirement for high dosage, offering immediate access to the site of interest while minimizing any unfavorable effects. Nonetheless, IA-injected drugs, administered in their free form, present low retention time in the knee joint raising the need for multiple injection dosage regimens, while their capability to target the cartilage or specific cell populations is limited. Liposomes, due to their unique characteristics and tunable nature, have proven to be excellent candidates for the management of knee OA. This review explores the last decade's research on the efficacy of various IA liposomal formulations, investigating their multifaceted properties as pharmaceutical carriers, lubricating agents, and a basis for combinatorial approaches paving the way to novel treatment solutions for OA.

Super-lubricous polyethylene glycol hydrogel microspheres for use in knee osteoarthritis treatments

Knee osteoarthritis (OA) is characterized by cartilage degeneration and significant reduction in lubrication. One strategy to recover the natural lubrication of the synovial fluid is the injection of hydrogel microspheres. Here, we have fabricated polyethylene glycol (PEG)-based hydrogel microspheres via a modified electrospraying setup. To improve throughout, crosslinking of PEG droplets was delayed until after droplet formation was complete. A custom-synthesized super-lubricious copolymer consisting of adhesive dopamine methacrylate (DMA), zwitterionic sulfobetaine methacrylate (SBMA), and fluorescent rhodamine B was used to dip-coat the PEG microspheres. Super-lubricious PEG microspheres coating reduced coefficient of friction by 57% compared to simulated synovial fluid, indicating beneficial lubrication properties. When injected into C57BL6 mice, PEG microspheres exhibited stability for up to 26 d and did not adversely affect mouse behavior. These super-lubricious PEG microspheres offer great promise to reduce the friction that is a hallmark of progressive OA, potentially mitigating the need for total knee arthroplasty.

All-Small-Molecule Supramolecular Hydrogel Combining Self-Delivery and ROS-Responsive Release for Inhibiting Tumor Growth and Postoperative Recurrence

Supramolecular hydrogels show unprecedented advantages and have attracted widespread attention in biomedical sciences. However, it is challenging for bioactive star molecules, such as celastrol, to meet ideal formation conditions. Here, we report a dynamic covalent method to construct a dihydrol-type celastrol-phenylenediboronic acid-guanosine (DHcelPBG) supramolecular hydrogel. The DHcelPBG hydrogel can effectively accelerate 4T1 cell apoptosis by modulating the PI3K/Akt signaling pathway. Especially, the DHcelPBG hydrogel can serve as a self-delivery platform for reactive oxygen species (ROS)-facilitated self-release. An excessive ROS-containing tumor microenvironment can promote the obtained DHcelPBG hydrogel to kill more 4T1 tumor cells. Meanwhile, the hydrogel also exhibits distinguished degradability and biocompatibility. Subsequently, the orthotopic 4T1 tumor model results further demonstrate that the DHcelPBG hydrogel remarkably inhibits tumor growth and does not damage healthy tissue. In the postoperative recurrence 4T1 tumor model, the DHcelPBG hydrogel also effectively prevents postoperative tumor recurrence and lung metastasis without causing adverse side effects, resulting in an extended lifetime. The DHcelPBG hydrogel also exhibits distinguished degradability and biocompatibility. The DHcelPBG hydrogel integrates ROS-responsiveness, localized self-delivery, and antitumor activity into one system for breast cancer treatment with fewer side effects, showing great potential for clinical transformation in cancer therapy.

Bioactive Zn-V-Si-Ca Glass Nanoparticle Hydrogel Microneedles with Antimicrobial and Antioxidant Properties for Bone Regeneration in Diabetic Periodontitis

Periodontitis is a chronic inflammatory condition affecting the periodontal tissue. This condition worsens in diabetic patients due to oxidative stress and inflammation. Herein, we investigated a treatment using bioactive Zn-V-Si-Ca glass nanoparticle hydrogel microneedles. The microneedles contain bioactive glass nanoparticles codoped with zinc and vanadium ions. They also include gallic acid and oxidized methacrylated hyaluronic acid. These microneedles address bacterial dysbiosis and oxidative stress in diabetic periodontitis. They provide antibacterial and antioxidant effects. The microneedles deliver therapeutic agents directly into the gingival tissue. This enhances drug retention and absorption by penetrating the mucosal barrier. In vitro studies demonstrated biocompatibility, excellent antioxidant properties, and acceptable mechanical properties. Meanwhile, the microneedle patches demonstrated antibacterial properties effective against a Gram-negative periodontal pathogen as well as a Gram-positive oral bacterium. In vivo experiments were performed using a diabetic rat model with periodontitis. Results showed significant improvement in alveolar bone regeneration. The hydrogel modulated the inflammatory microenvironment effectively. Ribonucleic acid sequencing revealed downregulation of JAK-STAT and NF-κB inflammation signaling pathways. This work presents a distinctive approach to suppressing the inflammatory response and modulate immune responses for the purpose of treating diabetic periodontitis early.

Nanodrugs Targeting Key Factors of Ferroptosis Regulation for Enhanced Treatment of Osteoarthritis

Osteoarthritis (OA) is a globally prevalent degenerative joint disease. Recent studies highlight the role of ferroptosis in OA progression. Targeting ferroptosis regulation presents a promising therapeutic strategy for OA; however, current research primarily focuses on single targets associated with ferroptosis. In this study, a reactive oxygen species (ROS)-responsive nanoparticle is developed by linking deferasirox (DEF) and pterostilbene (PTE) with thioketal and incorporating cerium ions (Ce), creating Ce@D&P nanoparticles (NPs), which offer multitarget regulation of ferroptosis. The characteristics of Ce@D&P NPs are evaluated and their therapeutic effects on IL-1β-stimulated chondrocytes are verified. Results show that Ce@D&P NPs reduce ROS levels, mitigate inflammation, chelate iron to inhibit ferroptosis, and balance extracellular matrix (ECM) metabolism in chondrocytes. Mechanistically, transcriptomics and metabolomics analyses suggest that Ce@D&P NPs exerted their effects by regulating oxidative stress and lipid metabolism in chondrocytes. To better treat destabilization of the medial meniscus (DMM)-induced OA in mice, Ce@D&P NPs via intra-articular injection are delivered. The results show that Ce@D&P NPs alleviate cartilage matrix damage and slow OA progression. Overall, the findings indicate that Ce@D&P NPs represent a promising multitarget drug delivery system, and Ce@D&P NPs may be an effective strategy for OA treatment.

Injectable Chondroitin Sulfate Microspheres with Gallic Acid-Magnesium MOF for Anti-Inflammatory and Cartilage Degeneration Alleviation in Osteoarthritis Treatment

Inflammation and cartilage degeneration are critical challenges in osteoarthritis (OA) treatment. Achieving sustained drug efficacy while mitigating the adverse effects of inflammation and reactive oxygen species remains a significant challenge. This study synthesizes a gallic acid-magnesium (GA-Mg) metal-organic framework (MOF) as a drug carrier for puerarin (PA). The PA-loaded GA-Mg MOF (pGM) is encapsulated within chondroitin sulfate methacrylate, forming monodisperse hybrid microspheres (CM@pGM) under ultraviolet light using microfluidic technology. The pGM is physically confined within the microspheres through a network of structural obstructions and noncovalent interactions. During degradation, GA and Mg2+ ions release from pGM, improving the inflammatory microenvironment of the articular cavity and mitigating oxidative stress. The sustained release of Mg2+ and PA supports chondrocyte anabolism and facilitates cartilage repair. In vitro studies confirm that injectable microspheres extend the drug release period to over 2 weeks. In vivo experiments demonstrate that CM@pGM significantly reduces osteophyte formation, alleviates degenerative changes in articular cartilage, and delays OA progression. In conclusion, CM@pGM, as a drug delivery platform that ameliorates the inflammatory microenvironment, alleviates oxidative stress, and promotes cartilage repair, holds significant potential for OA treatment.

MSCs-EVs harboring OA immune memory reprogram macrophage phenotype via modulation of the mt-ND3/NADH-CoQ axis for OA treatment

BACKGROUND

Osteoarthritis (OA) is a prevalent degenerative joint disease and current therapies are insufficient to halt its progression. Mesenchymal stem cells-derived extracellular vesicles (MSCs-EVs) offer promising therapeutic potential for OA treatment, and their efficacy can be enhanced through strategic engineering approaches.

METHODS

Inspired by the immune memory of the adaptive immune system, we developed an engineered strategy to impart OA-specific immune memory to MSCs-EVs. Using Luminex technology, inflammatory factors (IFN-γ, IL-6, and TNF-α), which mimic the OA inflammatory microenvironment, were identified and used to prime MSCs, generating immune memory-bearing MSCs-EVs (iEVs). Proteomic analysis and complementary experiments were conducted to evaluate iEVs' effects on macrophage phenotypic reprogramming.

RESULTS

iEVs, particularly IL-6-EV, exhibited potent immunoregulatory functions along with the ability to modulate mitochondrial metabolism. Both in vitro and in vivo, IL-6-EV significantly reprogrammed macrophages towards the M2 subtype, effectively suppressing articular inflammation and OA progression. Mechanistic studies revealed that IL-6-EV facilitated M2 polarization by regulating mitochondrial oxidative phosphorylation via the mt-ND3/NADH-CoQ axis.

CONCLUSION

This study introduces a strategy to enhance MSCs-EVs' therapeutic efficacy in OA. Multi-omics analysis and biological validation demonstrate its potential, providing new insights for MSCs-EVs' future application in OA and other clinical conditions.

Lubrication for Osteoarthritis: From Single-Function to Multifunctional Lubricants

Osteoarthritis (OA) is a common degenerative joint disease that progressively destroys articular cartilage, leading to increased joint friction and severe pain. Therefore, OA can be treated by restoring the lubricating properties of cartilage. In this study, recent advances in lubricants for the treatment of OA are reviewed for both single-function and multifunctional lubricants. Single-function lubricants mainly include glycosaminoglycans, lubricin, and phospholipids, whereas multifunctional lubricants are composed of lubricating and anti-inflammatory bifunctional hydrogels, stem cell-loaded lubricating hydrogels, and drug-loaded lubricating nanoparticles. This review emphasizes the importance of restoring joint lubrication capacity for the treatment of OA and explores the structural features, lubrication properties, and role of these lubricants in modulating intracellular inflammatory responses and metabolism. Current challenges and future research directions in this field are also discussed, with the aim of providing a scientific basis and new ideas for the clinical treatment of OA.

Tribology in Nature: Inspirations for Advanced Lubrication Materials

Friction-induced energy consumption is a significant global concern, driving researchers to explore advanced lubrication materials. In nature, lubrication is vital for the life cycle of animals, plants, and humans, playing key roles in movement, predation, and decomposition. After billions of years of evolution, natural lubrication exhibits remarkable professionalism, high efficiency, durability, and intelligence, offering valuable insights for designing advanced lubrication materials. This review focuses on the lubrication mechanisms of natural organisms and significant advancements in biomimetic soft matter lubrication materials. It begins by summarizing common biological lubrication behaviors and their underlying mechanisms, followed by current design strategies for biomimetic soft matter lubrication materials. The review then outlines the development and performance of these materials based on different mechanisms and strategies. Finally, it discusses potential research directions and prospects for soft matter lubrication materials. This review will be a valuable resource for advancing research in biomimetic lubrication materials.

Microenvironment-Responsive Hydrogels Comprising Engineering Zeolitic Imidazolate Framework-8-Anchored Parathyroid Hormone-Related Peptide-1 for Osteoarthritis Therapy

Intra-articular drug injections are effective for osteoarthritis (OA), but challenges such as the complex microenvironment and rapid drug diffusion require frequent injections. Herein, we propose a biofunctional hydrogel-based strategy for prolonged drug delivery and microenvironment remodeling. We propose a strategy to functionalize zeolitic imidazolate framework-8 with tannic acid (TA-ZIF), anchor PTH-related peptide-1 (PTHrP-1) within this framework (TA-ZIF@P1) and incorporate a phenylboronic acid-modified gelatin-based hydrogel (GP hydrogel) drug delivery system (GP@TA-ZIF@P1, GPTP hydrogel) with responsive release properties that respond to the pathological microenvironments of OA. The GPTP hydrogel facilitated controlled, sustained release of PTHrP-1 via dynamic boronic esters, with in vitro and in vivo studies showing continuous release for over 28 days. It not only promotes chondrocyte proliferation but also exhibits significant cytoprotective effects under hyperactive ROS and IL-1β-induced conditions. Notably, transcriptome sequencing confirms that the GPTP hydrogel facilitates both chondrocyte proliferation and chondrogenesis under inflammatory conditions by deactivating Wnt/β-Catenin signaling pathways and enhancing the PI3K/AKT signaling pathway. Additionally, the GPTP hydrogel delays the catabolic metabolism of cartilage explants from mice in inflammatory environments. In a surgical model of mouse OA, we show that the intra-articular injection of GPTP hydrogels reduced periarticular bone remodeling and promoted the production of glycosaminoglycans while offering chondroprotection against cartilage degeneration. To sum up, this pioneering research on PTHrP-1 as a treatment for OA, combined with the GPTP hydrogel system, offers valuable insights and a paradigm for the controlled and sustained release of PTHrP-1, representing a significant advancement in OA treatment strategies.

Recent applications of stimulus-responsive smart hydrogels for osteoarthritis therapy

Osteoarthritis is one of the most common degenerative joint diseases, which seriously affects the life of middle-aged and elderly people. Traditional treatments such as surgical treatment and systemic medication, often do not achieve the expected or optimal results, which leads to severe trauma and a variety of side effects. Therefore, there is an urgent need to develop novel therapeutic options to overcome these problems. Hydrogels are widely used in biomedical tissue repairing as a platform for loading drugs, proteins and stem cells. In recent years, smart-responsive hydrogels have achieved excellent results as novel drug delivery systems in the treatment of osteoarthritis. This review focuses on the recent advances of endogenous stimuli (including enzymes, pH, reactive oxygen species and temperature, etc.) responsive hydrogels and exogenous stimuli (including light, shear, ultrasound and magnetism, etc.) responsive hydrogels in osteoarthritis treatment. Finally, the current limitations of application and future prospects of smart responsive hydrogels are summarized.

Chondrocyte-targeted bilirubin/rapamycin carrier-free nanoparticles alleviate oxidative stress and modulate autophagy for osteoarthritis therapy

Osteoarthritis (OA) is a prevalent chronic disease, characterized by the destruction of joint cartilage and synovitis, affects over 7 % of people worldwide. Disease-modifying treatments for OA still face significant challenges. Chondrocytes, as the exclusive cellular component of articular cartilage, play a pivotal role in synthesizing the intricate matrix of cartilage, thereby assuming a critical responsibility in facilitating its renewal and repair processes. However, oxidative stress within chondrocytes and subsequent apoptotic cell death plays significant roles in the progression of OA. Therefore, targeting apoptosis inhibition and mitigation of oxidative stress in chondrocytes represents a promising therapeutic strategy for OA. This study develops a type II collagen-targeting peptide (WYRGRLC) modified bilirubin/rapamycin carrier-free nanoparticle (PP/BRRP) and evaluate its therapeutic potential for OA. The PP/BRRP system exhibits remarkable chondrocyte-targeting ability, enabling the rupture of highly oxidized chondrocytes and subsequent release of bilirubin and rapamycin. This dual payload effectively scavenges reactive oxygen species, triggers autophagy, and suppresses the mTOR pathway, thereby augmenting anti-inflammatory and anti-apoptotic effects. The in vivo experiments further validate the retention and therapeutic efficacy of PP/BRRP in rat joints affected by OA. Overall, PP/BRRP exhibits significant potential for intervention and treatment of OA.

Injectable and self-healing carboxymethyl chitosan/carboxymethyl cellulose/marine snail peptide hydrogel for infected wound healing

Treatment of bacterial infected full-thickness wounds remains a great challenge in clinic. Herein, a HYP hydrogel was prepared using carboxymethyl chitosan, dialdehyde carboxymethyl cellulose, and marine snail peptide (Tyr-Ile-Ala-Glu-Asp-Ala-Glu-Arg) as starting materials. The marine snail peptide with good antioxidant activity could remove the reactive oxygen species in wound sites, thereby alleviating the excessive inflammatory response. The dynamic Schiff-base bonds endowed HYP with good injectable and self-healing abilities. HYP exhibited suitable gelation time, good rheological properties, and unique porosity structure, which were conducive to wound healing. In vitro biological studies indicated that HYP showed good biocompatibility, low hemolysis ratio, and improved antibacterial and antioxidant activities. In vivo study revealed that HYP could promote wound healing in a bacterial infected full-thickness skin defect rat model. The wound tissues showed reduced number of inflammatory cells, newly formed hair follicles, and obvious collagen deposition. The expression of inflammatory and angiogenesis related biomarkers (IL-6, IL-10, CD31, and α-SMA) significantly improved. Therefore, HYP hydrogel showed great application prospect as a wound dressing for bacterial infected wound.

In Situ Proefferocytosis Microspheres as Macrophage Polarity Converters Accelerate Osteoarthritis Treatment

Efferocytosis in macrophages typically engages an anti-inflammatory positive feedback regulatory mechanism. In osteoarthritis (OA), characterized by imbalanced inflammatory homeostasis, the proinflammatory state of macrophages in the immune microenvironment can be reversed through enhanced efferocytosis. This study develops an in situ proefferocytosis hydrogel microsphere (macrophage polarity converter, H-C@IL) for OA treatment. Immunoliposomes (IL), CD16/32 antibody-modified clodronate liposomes, are initially prepared using the Re-emulsion method. Then, the IL is loaded into CCL19-modified HAMA microspheres through microfluidic technology. In vitro, H-C@IL can specifically recruit M0 and M1 macrophages via CCL19, induce apoptosis in M1 macrophages through secondary targeting with IL, and provide "Find/Eat-me" signals to enhance in situ efferocytosis. Additionally, it promotes macrophage polarization toward the M2 phenotype. In vivo, behavioral, imaging, and histological analyses demonstrate that H-C@IL effectively facilitates macrophage polarization toward M2, inhibits inflammation, and promotes cartilage regeneration. Mechanistically, H-C@IL enhances efferocytosis by activating proteins such as PROS1 and TIMD4 in M0 macrophages. Concurrently, signaling pathways, including PQLC2-Arg-Rac1 and Pbx1/IL-10, are activated to drive the polarization of macrophages from M0 to M2. In summary, H-C@IL promotes M0 macrophage efferocytosis in situ, facilitates macrophage polarization toward M2, restores inflammatory homeostasis, and promotes cartilage regeneration, offering a comprehensive treatment strategy for OA.

Injectable Self-Assembling Procyanidin Nanospheres for Effective Osteoarthritis Treatment

Background

Osteoarthritis (OA), a prevalent joint disease, causes immense suffering to thousands of patients, impairing their mobility and diminishing their quality of life. Current treatment methods primarily rely on analgesics or anti-inflammatory drugs to alleviate symptoms but fail to achieve the desired therapeutic outcome.

Methods

To better realize therapeutic effects of OA, procyanidins (PAs), as a type of plant flavonoids with strong antioxidant and anti-inflammatory activities, were designed to self-assembly with well-dispersible Pluronic F127 (PF127) through the hydrogen-bond interaction to present an injectable, biocompatibility PA nanospheres.

Results

These nanospheres significantly increased the cell viability in mouse L929 fibroblasts and ADTC5 chondrocytes compared with unassembled PAs. In addition, the self-assembling PAs/PF127 nanospheres enhanced the protein expression of collagen (COL1A1 and COL3A1) in fibroblasts, and the expression of glycosaminoglycan and COL2A1 was also higher than unassembled PAs in chondrocytes, this heralded the potential to achieve OA repair strategies at the cellular level. In an enzymolysis model of rat OA, PAs/PF127 nanospheres significantly reduce joint space swelling in the early stages of cartilage destruction and accelerate the formation of subchondral bone and cartilaginous surface.

Implication

This study offers valuable insights into the preparation of novel PA nanospheres for effective repair of OA.

Metal ion-crosslinking multifunctional hydrogel microspheres with inflammatory immune regulation for cartilage regeneration

Introduction

Osteoarthritis (OA) is a degenerative disease of the joints characterized by cartilage degradation and synovial inflammation. Due to the complex pathogenesis of OA, multifaceted therapies that modulate inflammatory and immune microenvironmental disturbances while promoting cartilage regeneration are key to control the progression of OA.

Methods

Herein, a multifunctional nanoparticle (DIC/Mg-PDA NPs) was constructed successfully by the metal chelation effect between Mg2+ and catecholamine bond from dopamine, followed by the amidation with diclofenac (DIC), which was then prepared into an injectable hydrogel microsphere (DIC/Mg-PDA@HM) with immune-regulating and cartilage-repairing abilities through microfluidic technology for the treatment of osteoarthritis.

Results and discussion

The sustained release of Mg2+ from the composite hydrogel microspheres achieved inflammatory immune regulation by converting macrophages from M1 to M2 and promoted cartilage regeneration through the differentiation of BMSCs. Moreover, the enhanced release of DIC and polydopamine (PDA) effectively downregulated inflammatory factors, and finally achieved OA therapy. In addition, in vivo MRI and tissue section staining of OA model proved the significant efficacy of the hydrogel microspheres on OA. In conclusion, these novel hydrogel microspheres demonstrated a promising prospect for multidisciplinary repairing of OA.

Downregulation of the PI3K/AKT/mTOR/MMP-13 pathway for promoting interface healing via lubricating microspheres

Interface friction impedes tissue healing and stimulates interface cells to produce matrix metalloproteinases (MMPs); however, the precise mechanisms underlying matrix degradation, and the formation of fibrous scars remain unclear. This research involved the development of interface lubricating microspheres that inhibit the PI3K/AKT/mTOR signaling pathway in tenocytes. This inhibition significantly decreased MMP-13 expression and increased COL-1 production, thereby facilitating interface repair and regeneration. In vitro experiments demonstrated that interface friction activates the PI3K/AKT/mTOR/MMP-13 signaling pathway, while the use of interface lubricating microspheres reduced friction by 78 %, resulting in a threefold decrease in MMP-13 expression through pathway inhibition. Animal studies showed that the application of interface lubricating microspheres reduced friction at the tendon-bone interface, mitigating MMP-13-mediated matrix degradation and effectively reducing fibrous scar formation (as evidenced by decreased α-SMA expression), thus promoting interface healing following ACLR surgery in rats. Consequently, this study suggests that interface friction can trigger the PI3K/AKT/mTOR signaling pathway in tenocytes, leading to increased MMP-13 expression, matrix degradation, and fibrous scar formation. The use of interface lubricating microspheres can enhance interface healing by inhibiting this pathway, offering strategies for improving interface healing and minimizing fibrous scar formation. STATEMENT OF SIGNIFICANCE: Interface healing plays a crucial role following tendon-bone surgeries, yet it is often hindered by challenges such as interface friction and scar formation. In this study, we propose a combined approach in which lubricating microspheres and an anti-matrix degradation drug are used to enhance interface healing. We fabricated novel lubricating microspheres that exhibit outstanding biocompatibility and degradability; these microspheres serve as lubricants for the tendon-bone interface and facilitate the delivery of doxycycline to reduce excessive matrix metalloproteinase (MMP) secretion. The experimental results demonstrated that this method could enhance tendon-bone interface healing in rats, resulting in increased bone formation and higher histological scores than those of the control group. This study represents a preliminary effort to integrate lubrication and anti-matrix degradation in interface healing, potentially offering new insights into the mechanism between interface friction and fibrous scar healing, while promoting interface healing by reducing interfacial friction.

Therapeutic Controlled Release Strategies for Human Osteoarthritis

Osteoarthritis is a progressive, irreversible debilitating whole joint disease that affects millions of people worldwide. Despite the availability of various options (non-pharmacological and pharmacological treatments and therapy, orthobiologics, and surgical interventions), none of them can definitively cure osteoarthritis in patients. Strategies based on the controlled release of therapeutic compounds via biocompatible materials may provide powerful tools to enhance the spatiotemporal delivery, expression, and activities of the candidate agents as a means to durably manage the pathological progression of osteoarthritis in the affected joints upon convenient intra-articular (injectable) delivery while reducing their clearance, dissemination, or side effects. The goal of this review is to describe the current knowledge and advancements of controlled release to treat osteoarthritis, from basic principles to applications in vivo using therapeutic recombinant molecules and drugs and more innovatively gene sequences, providing a degree of confidence to manage the disease in patients in a close future.

Macrophage Membrane-Biomimetic Multi-Layered Nanoparticles Targeting Synovial Angiogenesis for Osteoarthritis Therapy

Osteoarthritis (OA) is an inflammatory and progressive joint disease characterized by angiogenesis-mediated sustained, chronic, and low-grade synovitis. Anti-angiogenesis is emerging as a strategy for attenuating OA progression, but is often compromised by poor targeted drug delivery and immune clearance. Recent studies have identified macrophages formed a "protective barrier" in the lining layer (LL) of synovium, which blocked the communication of joint cavity and sublining layer (SL) of synovium. Inspired by natural mimicry, macrophage membrane-camouflaged drug delivery is explored to avoid immune clearance. Based on the single cell RNA sequencing, the CD34+ synovial cells are identified as "sentinel cells" for synovium angiogenesis. Consequently, CD34 antibody-modified macrophage membrane is constructed to target new angiogenesis. Hence, a biomimetic multi-layered nanoparticle (NP) is developed that incorporates axitinib-loaded poly(lactic-co-glycolic) acid (PLGA) with CD34 antibody modified macrophage membrane (Atb@NP@Raw@CD34) to specifically deliver axitinib (Atb) to the SL and sustain inhibiting angiogenesis without immune elimination. It is found that the Atb@NP@Raw@CD34 can pass through macrophage "barrier", specifically targeting CD34+ cells, continuously releasing Atb and anti-angiogenesis in OA synovitis. Furthermore, in vivo data demonstrated that Atb@NP@Raw@CD34 can attenuate joint degeneration by inhibiting synovium angiogenesis-mediated synovitis. In conclusion, local injection of Atb@NP@Raw@CD34 presents a promising approach for clinically impeding OA progression.

Building of CuO2@Cu-TA@DSF/DHA Nanoparticle Targets MAPK Pathway to Achieve Synergetic Chemotherapy and Chemodynamic for Pancreatic Cancer Cells

Background/Objectives: With the increase of reactive oxygen species (ROS) production, cancer cells can avoid cell death and damage by up-regulating antioxidant programs. Therefore, it will be more effective to induce cell death by using targeted strategies to further improve ROS levels and drugs that inhibit antioxidant programs. Methods: Considering that dihydroartemisinin (DHA) can cause oxidative damage to protein, DNA, or lipids by producing excessive ROS, while, disulfiram (DSF) can inhibit glutathione (GSH) levels and achieve the therapeutic effect by inhibiting antioxidant system and amplifying oxidative stress, they were co-loaded onto the copper peroxide nanoparticles (CuO2) coated with copper tannic acid (Cu-TA), to build a drug delivery system of CuO2@Cu-TA@DSF/DHA nanoparticles (CCTDD NPs). In response to the tumor microenvironment, DHA interacts with copper ion (Cu2+) to produce ROS, and a double (diethylthiocarbamate)-copper (II) (CuET) is generated by the complexation of DSF and Cu2+, which consumes GSH and inhibits antioxidant system. Meanwhile, utilizing the Fenton-like effect induced by the multi-copper mode can achieve ROS storm, activate the MAPK pathway, and achieve chemotherapy (CT) and chemodynamic (CDT). Results: Taking pancreatic cancer cell lines PANC-1 and BxPC-3 as the research objects, cell line experiments in vitro proved that CCTDD NPs exhibit efficient cytotoxicity on cancer cells. Conclusions: The CCTDD NPs show great potential in resisting pancreatic cancer cells and provides a simple strategy for designing powerful metal matrix composites.

On Multicell-Interaction Chip: In Situ Observing the Interactions between the Astrocytes with Lysosomal Dysfunction and BBB Cells

Lysosomes in astrocytes play vital roles in toxic protein degradation in the brain. Lysosomal dysfunction can lead to abnormal protein deposits, which further induce damage to neurons and the blood-brain barrier (BBB), and thereby affect the interaction between the nervous and vascular systems. Therefore, investigating the interactions between astrocytes with lysosomal dysfunction and BBB cells is of significant importance. However, the lack of effective in vitro models hinders the study of this complex system. Herein, an 8-well arrayed microfence multicell interculture chip (AMMIC) with a hydrophilically optimized surface is introduced for investigating the interactions between astrocytes and BBB cells. Then, a novel lysosome-targeted photosensitizer, IVQ-2Br, is synthesized for inducing controllable oxidative stress damage in the lysosomes of astrocytes. By the combination of the 8-well AMMIC and IVQ-2Br, a model for studying the interactions between astrocytes with lysosomal dysfunction and BBB cells has been constructed. Particularly, severe secondary injuries to BBB cells brought about by oxidative stress, including alterations in cell morphology and activity as well as notable DNA damage, are in situ observed on the 8-well AMMIC. The mediators involved in this oxidative stress injury-mediated intercellular communication are validated to be reactive oxygen species (ROS) and exosomes. This work not only presents an in vitro modeling method for studying cell-cell interactions but also demonstrates the potential of in vitro models constructed through the integration of complex microfluidic chip techniques and photosensitizers for advancing biomedical research.

Injectable bioadhesive hydrogel as a local nanomedicine depot for targeted regulation of inflammation and ferroptosis in rheumatoid arthritis

Medicine intervention is the major clinical treatment used to relieve the symptoms and delay the progression of rheumatoid arthritis (RA), but is limited by its poor targeted delivery and short therapeutic duration. Herein, we developed an injectable and bioadhesive gelatin-based (Gel) hydrogel as a local depot of leonurine (Leon)-loaded and folate-functionalized polydopamine (FA-PDA@Leon) nanoparticles for anti-inflammation and chondroprotection in RA. The nanoparticles could protect Leon and facilitate its entry into the M1 phenotype macrophage for intracellular delivery of Leon, while the hydrogel tightly adhered to the tissues in the joint cavity and prolonged the retention of FA-PDA@Leon nanoparticles, thus achieving higher availability and therapeutic efficiency of Leon. In vitro and in vivo experiments demonstrated that the Gel/FA-PDA@Leon hydrogel could strongly suppress the inflammatory response by down-regulating the JAK2/STAT3 signaling pathway in macrophages and protect the chondrocytes from ferritinophagy/ferroptosis. This contributed to maintaining the structural integrity of articular cartilage and accelerating the joint functional recovery. This work provides an effective and convenient strategy to achieve higher bioavailability and long-lasting therapeutic duration of medicine intervention in arthritis diseases.

Enhanced therapeutic potential of a self-healing hyaluronic acid hydrogel for early intervention in osteoarthritis

Osteoarthritis (OA) is characterized by symptoms such as abnormal lubrication function of synovial fluid and heightened friction on the cartilage surface in its early stages, prior to evident cartilage damage. Current early intervention strategies employing lubricated hydrogels to shield cartilage from friction often overlook the significance of hydrogel-cartilage adhesion and enhancement of the cartilage extracellular matrix (ECM). Herein, we constructed a hydrogel based on dihydrazide-modified hyaluronic acid (HA) (AHA) and catechol-conjugated aldehyde-modified HA (CHA), which not only adheres to the cartilage surface as an effective lubricant but also improves the extracellular environment of chondrocytes in OA. Material characterization experiments on AHA/CHA hydrogels with varying concentrations validated their exceptional self-healing capabilities, superior injectability and viscoelasticity, sustained adhesion strength to cartilage, and a low friction coefficient. Chondrocytes exhibited robust adhesion and proliferation on the AHA/CHA hydrogel surface, with the upregulation of cartilage matrix protein expression. Intra-articular injection of AHA/CHA hydrogels was performed following destabilization of the medial meniscus (DMM) surgery in mice to assess its protective effect on cartilage. The AHA/CHA hydrogel effectively attenuated the degree of cartilage wear, facilitated chondrocytes' anabolic metabolism, and restored the ECM of cartilage. Therefore, the AHA/CHA hydrogel emerges as a promising therapeutic approach in clinical practices of OA treatment.

Bone and Joint-on-Chip Platforms: Construction Strategies and Applications

Organ-on-a-chip, also known as "tissue chip," is an advanced platform based on microfluidic systems for constructing miniature organ models in vitro. They can replicate the complex physiological and pathological responses of human organs. In recent years, the development of bone and joint-on-chip platforms aims to simulate the complex physiological and pathological processes occurring in human bones and joints, including cell-cell interactions, the interplay of various biochemical factors, the effects of mechanical stimuli, and the intricate connections between multiple organs. In the future, bone and joint-on-chip platforms will integrate the advantages of multiple disciplines, bringing more possibilities for exploring disease mechanisms, drug screening, and personalized medicine. This review explores the construction and application of Organ-on-a-chip technology in bone and joint disease research, proposes a modular construction concept, and discusses the new opportunities and future challenges in the construction and application of bone and joint-on-chip platforms.

Janus-Structured Microgel Barrier with Tissue Adhesive and Hemostatic Characteristics for Efficient Prevention of Postoperative Adhesion

Postoperative adhesion (POA) is a common and serious complication following various types of surgery. Current physical barriers either have a short residence time at the surgical site with a low tissue attachment capacity or are prone to undesired adhesion formation owing to the double-sided adhesive property, which limits the POA prevention efficacy of the barriers. In this study, Janus-structured microgels (Janus-MGs) with asymmetric tissue adhesion capabilities are fabricated using a novel bio-friendly gas-shearing microfluidic platform. The anti-adhesive side of Janus-MGs, which consists of alginate, hyaluronic acid, and derivatives, endows the material with separation, lubrication, and adhesion prevention properties. The adhesive side provided Janus-MGs with tissue attachment and retention capability through catechol-based adhesion, thereby enhancing the in situ adhesion prevention effect. In addition, Janus-MGs significantly reduced blood loss and shortened the hemostatic time in rats, further reducing adhesion formation. Three commonly used rat POA models with different tissue structures and motion patterns are established in this study, namely peritoneal adhesion, intrauterine adhesion, and peritendinous adhesion models, and the results showed that Janus-MGs effectively prevented the occurrence of POA in all the models. The fabrication of Janus-MGs offers a reliable strategy and a promising paradigm for preventing POA following diverse surgical procedures.

Damascenone inhibits osteoclastogenesis by epigenetically modulating Nrf2-mediated ROS scavenge and counteracts OVX-induced osteoporosis

BACKGROUND

Bone formation and resorption regulate bone homeostasis. Excessive osteoclastogenesis enhances bone resorption and causes osteoporosis. Although medicines targeting osteoclast have been developed, these drugs have several side effects. Natural compounds have advantages in safety and efficiency, making them potential candidates for osteoporosis treatment.

PURPOSE

This study aims to elucidate the role of damascenone (Dama) in osteoclastogenesis and osteoporosis.

STUDY DESIGN AND METHODS

To demonstrate the effect of Dama on osteoclast differentiation and function, we performed multiple in vitro experiments including TRAP staining, F-actin staining, bone slice resorption assay, real-time PCR, and western bolt. Further, ROS detection, network pharmacology, microscale thermophoresis assay, and ChIP assay were conducted to elucidate the underlying molecular mechanism. Finally, the in vivo effects of Dama were verified using an ovariectomy induced osteoporosis mice model.

RESULTS

Dama inhibited RANKL-induced osteoclast differentiation and bone resorptive function in vitro. The expression of osteoclast-related genes and activation of MAPKs and NF-κB signaling in osteoclast were also attenuated by Dama. Meanwhile, Dama reduced intracellular ROS level via up-regulating Nrf2 expression. Network pharmacology demonstrated that HDAC2 is the potential direct target of Dama. Dama inhibited HDAC2 function and increased H3K27ac level of Nrf2, which induced Nrf2 expression and activated ROS scavenging enzymes. Inhibiting NRF2 or activating HDAC2 attenuated the effect of Dama on osteoclastogenesis. Finally, Dama injection suppressed in vivo osteoclastogenesis and ameliorated bone loss induced by OVX.

CONCLUSION

Dama attenuates osteoclastogenesis by epigenetically modulating Nrf2 expression and ROS scavenge. This study provides evidence for Dama being a potential treatment for osteoporosis.

Bioinspired injectable hydrogels for bone regeneration

The effective regeneration of bone/cartilage defects remains a significant clinical challenge, causing irreversible damage to millions annually.Conventional therapies such as autologous or artificial bone grafting often yield unsatisfactory outcomes, emphasizing the urgent need for innovative treatment methods. Biomaterial-based strategies, including hydrogels and active scaffolds, have shown potential in promoting bone/cartilage regeneration. Among them, injectable hydrogels have garnered substantial attention in recent years on account of their minimal invasiveness, shape adaptation, and controlled spatiotemporal release. This review systematically discusses the synthesis of injectable hydrogels, bioinspired approaches-covering microenvironment, structural, compositional, and bioactive component-inspired strategies-and their applications in various bone/cartilage disease models, highlighting bone/cartilage regeneration from an innovative perspective of bioinspired design. Taken together, bioinspired injectable hydrogels offer promising and feasible solutions for promoting bone/cartilage regeneration, ultimately laying the foundations for clinical applications. Furthermore, insights into further prospective directions for AI in injectable hydrogels screening and organoid construction are provided.

The Assembly of Miniaturized Droplets toward Functional Architectures

Recent explorations of bioengineering have generated new concepts and strategies for the processing of soft and functional materials. Droplet assembly techniques can address problems in the construction of extremely soft architectures by expanding the manufacturing capabilities using droplets containing liquid or hydrogels including weak hydrogels. This Perspective sets out to provide a brief overview of this growing field, and discusses the challenges and opportunities ahead. The study highlights the recent key advances of materials and architectures from hitherto effective droplet-assembly technologies, as well as the applications in biomedical and bioengineering fields from artificial tissues to bioreactors. It is envisaged that these assembled architectures, as nature-inspired models, will stimulate the discovery of biomaterials and miniaturized platforms for interdisciplinary research in health, biotechnology, and sustainability.

Rapidly molded sodium alginate/soy protein adhesive hydrogel with 808-nm laser inhibition of infected wounds

Infected wounds produce pus and heal slowly. To address this issue, we developed a rapid-setting SP/SA@BP-C hydrogel by combining sodium alginate (SA) and soy protein (SP) with black phosphorus (BP) grafted with clarithromycin (Cla) and incorporating Ca2+ for chelation. This hydrogel dressing exhibits excellent photothermal (PT) and photodynamic (PD) bacteriostatic effects without biotoxicity, making it suitable for treating infected wounds. Characterization confirmed its successful fabrication, and the bacteriostatic effect demonstrated over 99 % efficacy through the synergistic effects of PT, PD, and Cla. Cellular studies indicated nontoxicity and a promoting effect on cell proliferation (121.6 %). In the mouse-infected wound model, the hydrogel led to complete healing in 12 days, with good recovery of the skin's superficial dermal layer and appendages. Consequently, SP/SA@BP-C is a natural hydrogel dressing with promising properties.

Polysaccharide nanosystems for osteoarthritis therapy: Mechanisms, combinations, and future directions

Osteoarthritis (OA) represents a chronic degenerative joint ailment characterized by the gradual breakdown of cartilage, inflicting substantial physical and economic burdens, especially among the elderly. Given the incomplete understanding of OA's pathogenesis, there is an increasing need to develop targeted therapeutic strategies and preventive measures. Conventional pharmaceutical interventions, such as non-steroidal anti-inflammatory drugs, steroids, and opioids, though effective, are often accompanied by notable adverse effects, thus emphasizing the urgency in seeking safer and more efficient therapeutic alternatives. The rapid evolution of nanotechnology has opened the door to various nanosystems for drug delivery, offering a promising avenue to mitigate these side effects. Of particular interest, recent research has shed light on the significant potential of polysaccharide-based nanosystems in the context of OA therapy, demonstrating their capability to counter inflammation, oxidative stress, regulate chondrocyte metabolism and proliferation, and protect cartilage. Therefore, in this review, we provide an in-depth examination of the role of polysaccharide nanosystems in OA, focusing on summarizing these findings based on different mechanisms of action. Furthermore, this review explores the application of combined polysaccharide nanosystems in OA, aiming to establish a foundation for the utilization of novel drug delivery nanoplatforms in OA treatment, ultimately expanding therapeutic options for this debilitating condition.

Biomedical Applications and Nutritional Value of Specific Food-Derived Polysaccharide-Based Hydrogels

Food-derived polysaccharide-based hydrogels (FPBHs), which are composed of polysaccharides derived from food sources exhibit great potential for biomedical applications. The FPBHs possess a wide range of biological activities and can be utilized in the treatment of various clinical diseases. However, the majority of research efforts have predominantly focused on nonspecific polysaccharides derived from various sources (most plants, animals, and microorganisms), whereas the exploration of hydrogels originating from specific polysaccharides with distinct bioactivity extracted from natural food sources remains limited. In this review, a comprehensive search was conducted across 3 major databases (PubMed, Web of Science, and Medline) until October 24, 2024 to include 32 studies that employed FPBHs for biomedical applications. This review provides an overview of hydrogels based on specific food-derived polysaccharides by summarizing their types, sources, molecular weight, monosaccharide composition, and biological activities. The crosslinking strategies employed in the fabrication of FPBHs were demonstrated. The attributes and characteristics of FPBHs were delined, including their physical, chemical, and functional properties. Of particular note, the review highlights in vivo and in vitro studies exploring the biomedical applications of FPBHs and delve into the nutritional value of specific food-derived polysaccharides. The challenges encountered in basic research involving FPBHs were enumerated as well as limitation in their clinical practice. Finally, the potential market outlook for FPBHs in the future was also discussed.

Precise Clearance of Intracellular MRSA via Internally and Externally Mediated Bioorthogonal Activation of Micro/Nano Hydrogel Microspheres

Traditional high-dose antibiotic treatments of intracellular methicillin-resistant staphylococcus aureus (MRSA) are highly inefficient and associated with a high rate of infection relapse. As an effective antibacterial technology, sonodynamic therapy (SDT) may be able to break the dilemma. However, indiscriminate reactive oxygen species (ROS) release leads to potential side effects. This study incorporates Staphylococcal Protein A antibody-modified Cu2+/tetracarboxyphenylporphyrin nanoparticles (Cu(II)NS-SPA) into hydrogel microspheres (HAMA@Cu(II)NS-SPA) to achieve precise eradication of intracellular bacteria. This eradication is under bioorthogonal activation mediated by bacillithiol (BSH) (internally) and ultrasound (US) (externally). To specify, the US responsiveness of Cu(II)NS-SPA is restored when it is reduced to Cu(I)NS-SPA by the BSH secreted characteristically by intracellular MRSA, thus forming a bioorthogonal activation with the external US, which confines ROS production within the infected MΦ. Under external US activation at 2 W cm-2, over 95% of intracellular MRSA can be cleared. In vivo, a single injection of HAMA@Cu(II)NS-SPA achieves up to two weeks of antibacterial sonodynamic therapy, reducing pro-inflammatory factor expression by 90%, and peri-implant bone trabeculae numbers exceed the control group by five times. In summary, these micro/nano hydrogel microspheres mediated by internal and external bioorthogonal activation can precisely eliminate intracellular MRSA, effectively treating multi-drug resistant intracellular bacterial infections.

Lymphocyte-Derived Engineered Apoptotic Bodies with Inflammation Regulation and Cartilage Affinity for Osteoarthritis Therapy

Apoptotic bodies as plentiful extracellular vesicles generated from apoptotic cells play a central role in signal transduction and homeostasis regulation and simultaneously switch death to regeneration to a certain extent. Herein, we designed engineered apoptotic bodies derived from T cells to have the capacity of inflammation regulation and cartilage affinity. The engineered apoptotic bodies as a natural anti-inflammation factor were encapsulated into lubricating hydrogel microspheres to achieve an injectable microsphere complex for the treatment of osteoarthritis (OA). In the above therapeutic system, the engineered apoptotic bodies acted as a biochemical cue to regulate the inflammatory microenvironment and promote chondrocyte cartilage homeostasis, whereas the lubricating hydrogel microspheres served as a biophysical stimulation to effectively reduce the friction of the cartilage surface, restore the cartilage stress, and control the slow delivery of the encapsulated engineered apoptotic bodies by friction degradation. Consequently, the current work creates an injectable and multifunctional therapeutic microsphere to advance cartilage remodeling and OA therapy.