Injectable, High Specific Surface Area Cryogel Microscaffolds Integrated with Osteoinductive Bioceramic Fibers for Enhanced Bone Regeneration

Injectable hydrogel microsphere orchestrates immune regulation and bone regeneration via sustained release of calcitriol

Repairing bone defects in inflammatory conditions remains a significant clinical challenge. An ideal scaffold material for such situations should enable minimally invasive implantation and integrate capabilities for immunomodulation, anti-infection therapy, and enhanced bone regeneration. In this study, we developed injectable calcitriol@polydopamine@gelatin methacryloyl hydrogel microspheres (CAL@PDA@GMs) using microfluidic technology. This system facilitates the sustained release of calcitriol, which features excellent biocompatibility and biodegradability, promotes osteogenesis, scavenges excessive reactive oxygen species (ROS), and induces the polarization of macrophages from the M1 to M2 phenotype, thereby mitigating lipopolysaccharide (LPS)-induced inflammation. These mechanisms work synergistically to create an optimal immune microenvironment for bone regeneration in inflammatory conditions. RNA sequencing (RNA-Seq) analyses revealed that immunomodulation is achieved by regulating macrophage phenotypes, inhibiting the nuclear transcription factor-kappa B (NF-κB) and ROS signaling pathways, and reducing the secretion of pro-inflammatory cytokines. This study proposes a novel method to enhance tissue regeneration by remediating the damaged tissue microenvironment and presents a potential clinical therapeutic strategy for large-scale bone injuries.

Osteoinductive gelatin-based porous nanocomposite hydrogel for enhanced hemorrhagic bone defect repair

Bone defects with uncontrolled hemorrhage significantly threaten patient survival, and traditional hemostatic agents are insufficient to synergistically treat noncompressible bone bleeding and enhance healing. Thus, developing a multifunctional material with excellent hemostatic and osteogenic performance is highly desirable. Herein, porous methacrylate-modified gelatin (GelMA)/Laponite (LAP) nanocomposite hydrogel (GLNH) via freeze-induced physicochemical cross-linking are readily constructed to treat bone defects with intractable bleeding. Porous GLNH exhibits a remarkable absorption capacity of up to 20 times, along with excellent physiological stability, adjustable pore size, and outstanding shape recovery capacity. In addition, porous GLNH demonstrates excellent biocompatibility and enhances osteogenesis by up-regulating the expression of osteo-specific genes. In a rat skull defect, porous GLNH exhibits favorable hemostatic effect, low inflammation, and improved bone repair. Overall, the multifunctional porous GLNH holds great potential for treating bone defects with intractable bleeding.

Magnesium-gallate MOF integrated conductive cryogel for inflammation regulation and boosting bone regeneration

The regeneration and repair of natural bone is a complex and multifaceted process. Potentially, multifunctional scaffolds that exhibit synergistic effects of various biological activities and align with the dynamic bone healing process, are highly expected to achieve desirable bone repairing outcomes. Bioavailable magnesium (Mg) is an essential element taking part in bone regeneration via promoting angiogenesis and osteogenesis. Polyphenol gallic acid (GA) is an anti-inflammatory molecule that can modulate immune microenvironment. To control their release behaviors, Mg2+ and GA can react with each other to form metal-organic frameworks (MOF), which are then embedded into conductive porous scaffolds made of gelatin cryogel and poly(3,4-ethyldioxyethiophene): polystyrene sulfonate (PEDOT:PSS). In in vitro cell culture, the MOF-integrated conductive scaffold can simultaneously provide sustained supply of Mg2+ and GA to modulate the biological responses of a variety of cells. In in vivo evaluations, it shows remarkably enhanced new bone formation, as compared to groups of only MOF-contained non-conductive scaffold or conductive scaffold without MOF in rat calvarial defect model. In summary, conductive scaffold associated with sustained release of bioactive factors can serve as an effective treatment for inducing neo-bone growth benefiting from the synergistical contributions of diverse bioactive factors.

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.

Biodegradable Piezoelectric Janus Membrane Enabling Dual Antibacterial and Osteogenic Functions for Periodontitis Therapy

Guided tissue regeneration (GTR) using barrier membranes is a common clinical approach for treating periodontitis-induced alveolar bone loss. However, conventional GTR membranes lack antibacterial and osteoinductive properties, limiting their effectiveness. Piezoelectric materials, which generate electrical outputs under chewing forces, offer antibacterial and bone-regenerative potential due to their oppositely charged surfaces. Inspired by this, a piezoelectric Janus membrane was developed for dual-function GTR therapy. Biodegradable poly(l-lactide) (PLLA) and PLLA/gelatin membranes were electrospun, annealed, and polarized to create the A-P(+)/PG(-) piezoelectric Janus membrane. Notably, in this Janus membrane, the outer surface of the PLLA side (A-P(+)) carries positive charges and is positioned toward the gingival tissue to kill bacteria via charge interactions; the inner surface of the PG side (PG(-)) holds negative charges and faces the alveolar bone defect, promoting bone growth through immunomodulation and enhanced mineralization. In a mouse model of periodontitis, the Janus membrane A-P(+)/PG(-) demonstrated dual functionality, effectively reducing inflammation, inhibiting bone resorption. The bone mineral density of A-P(+)/PG(-) reached 1637 ± 37 mg/cm3 at 8 weeks after surgery, which was superior to commercial collagen membranes lacking antibacterial properties. Overall, this study introduces an innovative approach, leveraging biodegradable piezoelectric PLLA to construct a versatile Janus GTR membrane with enhanced antibacterial and osteogenic activity for periodontitis treatment.

Injectable microgel and micro-granular hydrogels for bone tissue engineering

Injectable microgels, made from both natural and synthetic materials, are promising platforms for the encapsulation of cells or bioactive agents, such as drugs and growth factors, for delivery to injury sites. They can also serve as effective micro-scaffolds in bone tissue engineering (BTE), offering a supportive environment for cell proliferation or differentiation into osteoblasts. Microgels can be injected in the injury sites individually or in the form of aggregated/jammed ones named micro-granular hydrogels. This review focuses on common materials and fabrication techniques for preparing injectable microgels, as well as their characteristics and applications in BTE. These applications include their use as cell carriers, delivery systems for bioactive molecules, micro-granular hydrogels, bio-inks for bioprinting, three-dimensional microarrays, and the formation of microtissues. Furthermore, we discuss the current and potential future applications of microgels in bone tissue regeneration.

Nanomaterials-Based Drug Delivery Systems for Therapeutic Applications in Osteoporosis

The etiology of osteoporosis is rooted in the disruption of the intricate equilibrium between bone formation and bone resorption processes. Nevertheless, the conventional anti-osteoporotic medications and hormonal therapeutic regimens currently employed in clinical practice are associated with a multitude of adverse effects, thereby constraining their overall therapeutic efficacy and potential. Recently, nanomaterials have emerged as a promising alternative due to their minimal side effects, efficient drug delivery, and ability to enhance bone formation, aiding in restoring bone balance. This review delves into the fundamental principles of bone remodeling and the bone microenvironment, as well as current clinical treatment approaches for osteoporosis. It subsequently explores the research status of nanomaterial-based drug delivery systems for osteoporosis treatment, encompassing inorganic nanomaterials, organic nanomaterials, cell-mimicking carriers and exosomes mimics and emerging therapies targeting the osteoporosis microenvironment. Finally, the review discusses the potential of nanomedicine in treating osteoporosis and outlines the future trajectory of this burgeoning field. The aim is to provide a comprehensive reference for the application of nanomaterial-based drug delivery strategies in osteoporosis therapy, thereby fostering further advancements and innovations in this critical area of medical research.

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

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

A Dual-Responsive Fe₃O₄@ZIF-8 Nanoplatform Combining Magnetic Targeting and pH Sensitivity for Low Back Pain Therapy

Low back pain (LBP) resulting from sciatic nerve compression presents major challenges in pain management, as traditional therapies provide only short-term relief and pose risks of systemic toxicity. In this study, an innovative Fe3O4@ZIF-8-RVC (FZR) dual-responsive nanoplatform is introduced that integrates magnetic targeting with pH-sensitive, sustained drug release to overcome these limitations. The FZR nanoplatform encapsulates ropivacaine (RVC) within the ZIF-8-coated Fe3O4 core, enabling precise and prolonged analgesia at the injury site through magnetic guidance and acid-triggered release. In vitro and in vivo assessments indicate that FZR achieves high drug loading, sustained release in acidic environments, and excellent biocompatibility, significantly extending analgesic effects in chronic nerve injury models while minimizing systemic exposure. Behavioral tests and molecular analyses in LBP rat models confirm that FZR effectively suppresses pain-related neuronal activity and central sensitization markers. This dual-responsive nanoplatform FZR offers a safe, long-lasting, and targeted therapeutic approach, holding strong potential for advancing pain relief in LBP and related neuropathic pain conditions.

Injectable Polyhydroxyalkanoate-Nano-Clay Microcarriers Loaded with r-BMSCs Enhance the Repair of Cranial Defects in Rats

Purpose

Successful regeneration of cranial defects necessitates the use of porous bone fillers to facilitate cell proliferation and nutrient diffusion. Open porous microspheres, characterized by their high specific surface area and osteo-inductive properties, offer an optimal microenvironment for cell ingrowth and efficient ossification, potentially accelerating bone regeneration.

Materials and Methods

An in vitro investigation was conducted to assess the physicochemical properties, porosity, and biocompatibility of PHA-nano-clay open porous microspheres. Subsequently, PHA-nano-clay microspheres loaded with rat bone marrow mesenchymal stem cells were implanted into 5 mm cranial defects in rats for a duration of 12 weeks and were evaluated through histological and immunohistochemical analyses.

Results

The incorporation of nano-clay into PHA resulted in improved mechanical properties of the porous scaffolds. Furthermore, cell adhesion, viability, and morphology on the scaffolds were maintained. The PHA-3% nano-clay open porous microspheres effectively enhanced the repair of cranial defects compared to the control group, without recurrence or complications.

Conclusion

Porous PHA-nano-clay microspheres, with their high specific surface area, biodegradability, and osteo-inductive properties, can be utilized as a bone-filling material for improved bone defect repair through cell delivery. In particular, PHA-3% nano-clay open porous microspheres exhibit promising therapeutic potential in the repair of cranial defects.

Controlled release of magnesium ions from PLA microsphere-chitosan hydrogel complex for enhancing osteogenic and angiogenic activities in vitro

Magnesium ions (Mg2+) play an essential role in the metabolism and regeneration of bone tissue. Appropriate amounts of Mg2+ have been shown to promote osteogenic differentiation of bone-derived cells and angiogenesis of endothelial cells. However, the initial burst release of Mg2+ may compromise the osteogenic effect, so the controlled release of Mg2+ is the critical consideration of the magnesium-containing tissue-engineered bone materials. This study proposes a microsphere-hydrogel complex to enhance the sustained-release effect and prolong the release cycle of Mg2+. For the initial release of Mg2+, polylactic acid (PLA) microspheres containing MgO and MgCO3 were fabricated with uniform morphology. Further microspheres were incorporated into the chitosan-based hydrogel to form microsphere- hydrogel complex for extended release. The complex demonstrated effective sustained release of Mg2+ over a period exceeding 28 days. In vitro cell experiments, CS/PLA@MgO-MgCO3 significantly enhanced migration and osteogenic differentiation of MC3T3-E1. Meanwhile, it can facilitate the generation of blood vessels in HUVECs. In conclusion, the magnesium-loaded microsphere-hydrogel complex achieves excellent dual sustained-release properties with an extended-release cycle while enhancing vascularized osteogenic activity in vitro, showing promising prospects for clinical application in bone defect treatment.

Synergy of engineered gelatin methacrylate-based porous microspheres and multicellular assembly to promote osteogenesis and angiogenesis in bone tissue reconstruction

One of the key challenges in bone defects treatment is providing adequate and stable blood supply during new tissue regeneration. Mesenchymal stem cells (MSCs) and endothelial cells (ECs) have great potential to promote osteogenesis and angiogenesis during bone defect repair through paracrine effects, but their therapeutic efficacy depends on effective cellular assembly and delivery. In this work, we developed various microspheres with different pore sizes for multi-cellular delivery to enhance the angiogenic and osteogenic capability via combining microfluidic and gradient freeze-drying techniques. The particle and pore size of fabricated porous gelatin methacrylate (GelMA)-based hydrogel microspheres (PGMS) could be controllable through adjusting the freezing time of hydrogel microspheres, the range of particles and pores size are 150-250 μm and 10-100 μm with different freezing time from 0 min to 30 min. The optimized particle size (200.8 ± 14.2 μm) and pore size (11.2 ± 1.9 μm) were explored to promote cell assemble, adhesion, growth, and proliferation in the PGMS. Furthermore, the co-assembly and delivery of bone marrow mesenchymal stem cells (BMSCs) and human umbilical vein endothelial cells (HUVECs) on the PGMS was achieved and an optimal cellular ratio of BMSCs to HUVECs (20:2) was established for co-culturing of them to achieve optimal paracrine effects, further promoting osteogenic differentiation and angiogenesis. Finally, results from both in vitro and in vivo experiments showed that the developed PGMS with co-assembly of BMSCs to HUVECs contributed to accelerate bone regeneration and vascularization process daringly, exhibited great potential in vascularized bone tissue reconstruction.

Cryogels Composites: Recent Improvement in Bone Tissue Engineering

Autogenous bone grafts have long been considered the optimal choice for bone reconstruction due to their excellent biocompatibility and osteogenic properties. However, their limited availability and associated donor site morbidity have led to exploration of alternative bone substitutes. Cryogels, with their interconnected porosity, shape recovery, and enhanced mass transport capabilities, have emerged as a promising polymer-based solution. By incorporating bioactive glasses and nanofillers, cryogel composites offer bioactivity, cost-efficiency, and easy cell integration. This approach not only enhances bone regeneration but also underscores the broader role of nanotechnology in regenerative medicine. This mini-review discusses the advancement of organic-inorganic composites, focusing on biopolymeric cryogels and inorganic elements for reinforcement. We highlight how cryogels can be integrated into minimally invasive procedures, reducing patient distress and complications, and advanced 3D-printing techniques that enable further customization of these materials to mimic bone tissue architecture, offering potential for patient-specific treatments.

Dual cross-linked polyurethane-alginate biomimetic hydrogel for elastic gradient simulation in osteochondral structures: Microenvironment modulation and tissue regeneration

The distinctive composition and functions of osteochondral structures result in constrained regeneration. Insufficient healing processes may precipitate the emergence of tissue growth disorders or excessive subchondral bone formation, which can culminate in the deterioration and failure of osteochondral tissue repair. To overcome these limitations, materials designed for osteochondral repair must provide region-specific modulation of the microenvironment and mechanical compatibility. To address these challenges, we propose a method to create continuous hydrogels with distinct structural and functional properties by a precise cross-linking method. We have developed an innovative polyurethane enriched with dimethylglyoxime, facilitating the coordinated loading and precise release of Zn2+. This strategy enables the meticulous control of alginate cross-linking, resulting in an elastic gradient hydrogel that closely resembles the osteochondral interface. The SeSe within the hydrogel effectively modulates the inflammatory microenvironment and fosters the M2 polarization of macrophages. The hydrogel's lower layer is designed to rapidly release Zn2+, thereby enhancing bone regeneration. The upper layer is intended to prevent bone overgrowth and stimulate chondrogenic differentiation. This dual-layer strategy allows targeted stimuli to each region, promoting the seamless integration of neoosteochondral tissue. Our study demonstrates the potential of this stratified hydrogel in achieving uniform and smooth osteochondral tissue regeneration.

An Andrias davidianus derived composite hydrogel with enhanced antibacterial and bone repair properties for osteomyelitis treatment

Effective antibacterial therapy while accelerating the repair of bone defects is crucial for the treatment of osteomyelitis. Inspired by the protective mechanism of Andrias davidianus, we constructed an antibacterial hydrogel scaffold with excellent rigidity and long-term slow-release activity. While retaining the toughness of the skin secretion of Andrias davidianus (SSAD), the rigidity of the hydrogel material is increased by incorporating hydroxyapatite to meet the demands of bone-defect-filling materials. It also exerted antibacterial effects via the slow-release of vancomycin from local osteomyelitis lesions. Notably, the hydrogel can also carry a high stable recombinant miR-214-3p inhibitor (MSA-anti214). By the delivery of nano vector polyvinylamine, the long-term slow-release of MSA-anti214 is achieved to promote bone repair, making this composite hydrogel a potential SSAD-based osteomyelitis alleviator (SOA). In vitro and vivo results verified that the SOA effectively eliminated Staphylococcus aureus and repaired bone defects, ultimately mitigating the progression of osteomyelitis. This composite hydrogel extends the economic application prospects of A. davidianus and has provided new insights for the treatment of osteomyelitis. The study also explored new insights for the bone filling materials of bone defection and other skeletal system diseases.

Recent advancements in microspheres mediated targeted delivery for therapeutic interventions in osteoarthritis

Osteoarthritis (OA), affecting around 240 million people globally is a major threat. Currently, available drugs only treat the symptoms of OA; they cannot reverse the disease's progression. The delivery of drugs to afflicted joints is challenging because of poor vasculature of articular cartilage results in their less bioavailability and quick elimination from the joints. Recently approved drugs such as KGN and IL-1 receptor antagonists also encounter challenges because of inadequate formulations. Therefore, microspheres could be a potential player for the intervention of OA owing to its excellent physicochemical properties. This review primarily focuses on microspheres of distinct biomaterials acting as cargo for drugs and biologicals via different delivery routes in the effective management of OA. Microspheres can improve the efficacy of therapeutics by targeting strategies at specific body locations. This review also highlights clinical trials conducted in the last few decades.

Propelling Minimally Invasive Tissue Regeneration With Next-Era Injectable Pre-Formed Scaffolds

The growing aging population, with its associated chronic diseases, underscores the urgency for effective tissue regeneration strategies. Biomaterials play a pivotal role in the realm of tissue reconstruction and regeneration, with a distinct shift toward minimally invasive (MI) treatments. This transition, fueled by engineered biomaterials, steers away from invasive surgical procedures to embrace approaches offering reduced trauma, accelerated recovery, and cost-effectiveness. In the realm of MI tissue repair and cargo delivery, various techniques are explored. While in situ polymerization is prominent, it is not without its challenges. This narrative review explores diverse biomaterials, fabrication methods, and biofunctionalization for injectable pre-formed scaffolds, focusing on their unique advantages. The injectable pre-formed scaffolds, exhibiting compressibility, controlled injection, and maintained mechanical integrity, emerge as promising alternative solutions to in situ polymerization challenges. The conclusion of this review emphasizes the importance of interdisciplinary design facilitated by synergizing fields of materials science, advanced 3D biomanufacturing, mechanobiological studies, and innovative approaches for effective MI tissue regeneration.

Diatomite-incorporated hierarchical scaffolds for osteochondral regeneration

Osteochondral regeneration involves the highly challenging and complex reconstruction of cartilage and subchondral bone. Silicon (Si) ions play a crucial role in bone development. Current research on Si ions mainly focuses on bone repair, by using silicate bioceramics with complex ion compositions. However, it is unclear whether the Si ions have important effect on cartilage regeneration. Developing a scaffold that solely releases Si ions to simultaneously promote subchondral bone repair and stimulate cartilage regeneration is critically important. Diatomite (DE) is a natural diatomaceous sediment that can stably release Si ions, known for its abundant availability, low cost, and environmental friendliness. Herein, a hierarchical osteochondral repair scaffold is uniquely designed by incorporating gradient DE into GelMA hydrogel. The adding DE microparticles provides a specific Si source for controlled Si ions release, which not only promotes osteogenic differentiation of rBMSCs (rabbit bone marrow mesenchymal stem cells) but also enhances proliferation and maturation of chondrocytes. Moreover, DE-incorporated hierarchical scaffolds significantly promoted the regeneration of cartilage and subchondral bone. The study suggests the significant role of Si ions in promoting cartilage regeneration and solidifies their foundational role in enhancing bone repair. Furthermore, it offers an economic and eco-friendly strategy for developing high value-added osteochondral regenerative bioscaffolds from low-value ocean natural materials.

Expression, characterization, and application of human-like recombinant gelatin

Gelatin is a product obtained through partial hydrolysis and thermal denaturation of collagen, belonging to natural biopeptides. With irreplaceable biological functions in the field of biomedical science and tissue engineering, it has been widely applied. The amino acid sequence of recombinant human-like gelatin was constructed through a newly designed hexamer composed of six protein monomer sequences in series, with the minimum repeating unit being the characteristic Gly-X-Y sequence found in type III human collagen α1 chain. The nucleotide sequence was subsequently inserted into the genome of Pichia pastoris to enable soluble secretion expression of recombinant gelatin. At the shake flask fermentation level, the yield of recombinant gelatin is up to 0.057 g/L, and its purity can rise up to 95% through affinity purification. It was confirmed in the molecular weight determination and amino acid analysis that the amino acid composition of the obtained recombinant gelatin is identical to that of the theoretically designed. Furthermore, scanning electron microscopy revealed that the freeze-dried recombinant gelatin hydrogel exhibited a porous structure. After culturing cells continuously within these gelatin microspheres for two days followed by fluorescence staining and observation through confocal laser scanning microscopy, it was observed that cells clustered together within the gelatin matrix, exhibiting three-dimensional growth characteristics while maintaining good viability. This research presents promising prospects for developing recombinant gelatin as a biomedical material.

Mussel inspired 3D elastomer enabled rapid calvarial bone regeneration through recruiting more osteoprogenitors from the dura mater

Currently, the successful healing of critical-sized calvarial bone defects remains a considerable challenge. The immune response plays a key role in regulating bone regeneration after material grafting. Previous studies mainly focused on the relationship between macrophages and bone marrow mesenchymal stem cells (BMSCs), while dural cells were recently found to play a vital role in the calvarial bone healing. In this study, a series of 3D elastomers with different proportions of polycaprolactone (PCL) and poly(glycerol sebacate) (PGS) were fabricated, which were further supplemented with polydopamine (PDA) coating. The physicochemical properties of the PCL/PGS and PCL/PGS/PDA grafts were measured, and then they were implanted as filling materials for 8 mm calvarial bone defects. The results showed that a matched and effective PDA interface formed on a well-proportioned elastomer, which effectively modulated the polarization of M2 macrophages and promoted the recruitment of dural cells to achieve full-thickness bone repair through both intramembranous and endochondral ossification. Single-cell RNA sequencing analysis revealed the predominance of dural cells during bone healing and their close relationship with macrophages. The findings illustrated that the crosstalk between dural cells and macrophages determined the vertical full-thickness bone repair for the first time, which may be the new target for designing bone grafts for calvarial bone healing.

Bioactive ceramic-based materials: beneficial properties and potential applications in dental repair and regeneration

Bioactive ceramics, primarily consisting of bioactive glasses, glass-ceramics, calcium orthophosphate ceramics, calcium silicate ceramics and calcium carbonate ceramics, have received great attention in the past decades given their biocompatible nature and excellent bioactivity in stimulating cell proliferation, differentiation and tissue regeneration. Recent studies have tried to combine bioactive ceramics with bioactive ions, polymers, bioactive proteins and other chemicals to improve their mechanical and biological properties, thus rendering them more valid in tissue engineering scaffolds. This review presents the beneficial properties and potential applications of bioactive ceramic-based materials in dentistry, particularly in the repair and regeneration of dental hard tissue, pulp-dentin complex, periodontal tissue and bone tissue. Moreover, greater insights into the mechanisms of bioactive ceramics and the development of ceramic-based materials are provided.

Surface functionalization of calcium magnesium phosphate cements with alginate sodium for enhanced bone regeneration via TRPM7/PI3K/Akt signaling pathway

Although calcium‑magnesium phosphate cements (CMPCs) have been widely applied to treating critical-size bone defects, their repair efficiency is unsatisfactory owing to their weak surface bioactivity and uncontrolled ion release. In this study, we lyophilized alginate sodium (AS) as a coating onto HAp/K-struvite (H@KSv) to develop AS/HAp/K-struvite (AH@KSv), which promotes bone regeneration. The compressive strength and hydrophilicity of AH@KSv significantly improved, leading to enhanced cell adhesion in vitro. Importantly, the SA coating enables continuous ions release of Mg2+ and Ca2+, finally leading to enhanced osteogenesis in vitro/vivo and different patterns of new bone ingrowth in vivo. Furthermore, these composites increased the expression levels of biomarkers of the TRPM7/PI3K/Akt signaling pathway via an equilibrium effect of Mg2+ to Ca2+. In conclusion, our study provides novel insights into the mechanisms of Mg-based biomaterials for bone regeneration.

Injectable Nano-Micro Composites with Anti-bacterial and Osteogenic Capabilities for Minimally Invasive Treatment of Osteomyelitis

The effective management of osteomyelitis remains extremely challenging due to the difficulty associated with treating bone defects, the high probability of recurrence, the requirement of secondary surgery or multiple surgeries, and the difficulty in eradicating infections caused by methicillin-resistant Staphylococcus aureus (MRSA). Hence, smart biodegradable biomaterials that provide effective and precise local anti-infection effects and can promote the repair of bone defects are actively being developed. Here, a novel nano-micro composite is fabricated by combining calcium phosphate (CaP) nanosheets with drug-loaded GelMA microspheres via microfluidic technology. The microspheres are covalently linked with vancomycin (Van) through an oligonucleotide (oligo) linker using an EDC/NHS carboxyl activator. Accordingly, a smart nano-micro composite called "CaP@MS-Oligo-Van" is synthesized. The porous CaP@MS-Oligo-Van composites can target and capture bacteria. They can also release Van in response to the presence of bacterial micrococcal nuclease and Ca2+, exerting additional antibacterial effects and inhibiting the inflammatory response. Finally, the released CaP nanosheets can promote bone tissue repair. Overall, the findings show that a rapid, targeted drug release system based on CaP@MS-Oligo-Van can effectively target bone tissue infections. Hence, this agent holds potential in the clinical treatment of osteomyelitis caused by MRSA.

Double-layered microneedle patch loaded with bioinspired nano-vaccine for melanoma treatment and wound healing

Malignant melanoma is a challenging problem worldwide, because the remaining tumor cells and extensive skin defects following surgical resection are difficult to treat. Biomaterial-mediated immunotherapy has emerged as a superior strategy for anti-tumor applications in recent years. Herein, a unique double-layer MNP was developed to address the problem of malignant melanoma. Hydroxyapatite (HAP) and short-chain peptides from tumor cells were self-assembled to prepare the bioinspired nano-vaccine, and then they were loaded onto the microneedle tips of methacrylated gelatin (GelMA)-based MNP. The products (dubbed HVMN) demonstrated relatively good biocompatibility and immune activity, inhibiting the proliferation and inducing apoptosis of malignant melanoma in a B16 cell-bearing model of C57BL/6 mice, and promoting skin tissue regeneration in a full thickness skin defect model of SD rats in 15 days. The putative molecular pathways were examined preliminarily. In conclusion, this research will develop a competitive microneedle patch with dual anti-tumor and pro-regenerative properties for the postoperative treatment of malignant melanoma.

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.

MnO2 Decorated Metal-Organic Framework-Based Hydrogel Relieving Tumor Hypoxia for Enhanced Photodynamic Therapy

Photodynamic therapy (PDT) has emerged as a promising cancer treatment modality; however, its therapeutic efficacy is greatly limited by tumor hypoxia. In this study, a metal-organic framework (MOF)-based hydrogel (MOF Gel) system that synergistically combines PDT with the supply of oxygen is designed. Porphyrin-based Zr-MOF nanoparticles are synthesized as the photosensitizer. MnO2 is decorated onto the surface of the MOF, which can effectively convert H₂O₂ into oxygen. Simultaneously, the incorporation of MnO2 -decorated MOF (MnP NPs) into a chitosan hydrogel (MnP Gel) serves to enhance its stability and retention at the tumor site. The results show that this integrated approach significantly improves tumor inhibition efficiency by relieving tumor hypoxia and enhancing PDT. Overall, the findings underscore the potential for employing nano-MOF-based hydrogel systems as promising agents for cancer therapy, thus advancing the application of multifunctional MOFs in cancer treatment.

Integrated Piezoelectric/Conductive Composite Cryogel Creates Electroactive Microenvironment for Enhanced Bone Regeneration

Natural bone tissue possesses inherent electrophysiological characteristics, displaying conductivity and piezoelectricity simultaneously; hence, the reconstruction of local electrical microenvironment at defect site provides an effective strategy to enhance osteogenesis. Herein, a composite cryogel-type scaffold (referred to as Gel-PD-CMBT) is developed for bone regeneration, utilizing gelatin (Gel) in combination with a conductive poly(ethylene dioxythiophene)/polystyrene sulfonate matrix and Ca/Mn co-doped barium titanate (CMBT) nanofibers as the piezoelectric filler. The incorporation of these components results in the formation of an integrated piezoelectric/conductive network within the scaffold, facilitating charge migration and yielding a conductivity of 0.59 S cm-1 . This conductive scaffold creates a promising electroactive microenvironment, which is capable of up-regulating biological responses. Furthermore, the interconnected porous structure of the Gel-PD-CMBT scaffold not only provides mechanical stability but also offered ample space for cellular and tissue ingrowth. This Gel-PD-CMBT scaffold demonstrates a greater capacity to promote cellular osteogenic differentiation in vitro and neo-bone formation in vivo. In summary, the Gel-PD-CMBT scaffold, with its integrated piezoelectricity and conductivity, effectively restores the local electroactive microenvironment, offering an ideal platform for the regeneration of electrophysiological bone tissue.