Collagen-based materials, renowned for their biocompatibility and minimal immunogenicity, serve as exemplary substrates in a myriad of biomedical applications. Collagen-based micro/nanogels, in particular, are valued for their increased surface area, tunable degradation rates, and ability to facilitate targeted drug delivery, making them instrumental in advanced therapeutics and tissue engineering endeavors. Although extensive reviews on micro/nanogels exist, they tend to cover a wide range of biomaterials and lack a specific focus on collagen-based materials. The current review offers an in-depth look into the manufacturing technologies, drug release mechanisms, and biomedical applications of collagen-based micro/nanogels to address this gap. First, we provide an overview of the synthetic strategies that allow the precise control of the size, shape, and mechanical strength of these collagen-based micro/nanogels by controlling the degree of cross-linking of the materials. These properties are crucial for their performance in biomedical applications. We then highlight the environmental responsiveness of these collagen-based micro/nanogels, particularly their sensitivity to enzymes and pH, which enables controlled drug release under various pathological conditions. The discussion then expands to include their applications in cancer therapy, antimicrobial treatments, bone tissue repair, and imaging diagnosis, emphasizing their versatility and potential in these critical areas. The challenges and future perspectives of collagen-based micro/nanogels in the field are discussed at the end of the review, with an emphasis on the translation to clinical practice. This comprehensive review serves as a valuable resource for researchers, clinicians, and scientists alike, providing insights into the current state and future directions of collagen-based micro/nanogel research and development.
Collagen/chemistry* ; Drug Delivery Systems/methods* ; Humans ; Tissue Engineering/methods* ; Animals ; Biocompatible Materials/chemistry*

OBJECTIVE: To summarize the research progress of bioactive scaffolds in the repair and regeneration of osteoporotic bone defects. METHODS: Recent literature on bioactive scaffolds for the repair of osteoporotic bone defects was reviewed to summarize various types of bioactive scaffolds and their associated repair methods. RESULTS: The application of bioactive scaffolds provides a new idea for the repair and regeneration of osteoporotic bone defects. For example, calcium phosphate ceramics scaffolds, hydrogel scaffolds, three-dimensional (3D)-printed biological scaffolds, metal scaffolds, as well as polymer material scaffolds and bone organoids, have all demonstrated good bone repair-promoting effects. However, in the pathological bone microenvironment of osteoporosis, the function of single-material scaffolds to promote bone regeneration is insufficient. Therefore, the design of bioactive scaffolds must consider multiple factors, including material biocompatibility, mechanical properties, bioactivity, bone conductivity, and osteogenic induction. Furthermore, physical and chemical surface modifications, along with advanced biotechnological approaches, can help to improve the osteogenic microenvironment and promote the differentiation of bone cells. CONCLUSION With advancements in technology, the synergistic application of 3D bioprinting, bone organoids technologies, and advanced biotechnologies holds promise for providing more efficient bioactive scaffolds for the repair and regeneration of osteoporotic bone defects.
Humans ; Tissue Scaffolds/chemistry* ; Bone Regeneration ; Osteoporosis/therapy* ; Tissue Engineering/methods* ; Biocompatible Materials/chemistry* ; Printing, Three-Dimensional ; Calcium Phosphates/chemistry* ; Osteogenesis ; Ceramics ; Cell Differentiation ; Hydrogels ; Bioprinting ; Bone and Bones

OBJECTIVE: To summarize the latest research progress of graphene and its derivatives (GDs) in bone repair. METHODS: The relevant research literature at home and abroad in recent years was extensively accessed. The properties of GDs in bone repair materials, including mechanical properties, electrical conductivity, and antibacterial properties, were systematically summarized, and the unique advantages of GDs in material preparation, functionalization, and application, as well as the contributions and challenges to bone tissue engineering, were discussed. RESULTS: The application of GDs in bone repair materials has broad prospects, and the functionalization and modification technology effectively improve the osteogenic activity and material properties of GDs. GDs can induce osteogenic differentiation of stem cells through specific signaling pathways and promote osteogenic activity through immunomodulatory mechanisms. In addition, the parameters of GDs have significant effects on the cytotoxicity and degradation behavior. CONCLUSION GDs has great potential in the field of bone repair because of its excellent physical and chemical properties and biological properties. However, the cytotoxicity, biodegradability, and functionalization strategies of GDs still need to be further studied in order to achieve a wider application in the field of bone tissue engineering.
Graphite/pharmacology* ; Tissue Engineering/methods* ; Humans ; Osteogenesis/drug effects* ; Biocompatible Materials/pharmacology* ; Bone Regeneration ; Tissue Scaffolds/chemistry* ; Cell Differentiation ; Bone and Bones ; Bone Substitutes/chemistry* ; Animals

OBJECTIVE: To evaluate the effect of biodegradable magnesium alloy materials in promoting tendon-bone healing during rotator cuff tear repair and to investigate their potential underlying biological mechanisms. METHODS: Forty-eight 8-week-old Sprague Dawley rats were taken and randomly divided into groups A, B, and C. Rotator cuff tear models were created and repaired using magnesium alloy sutures in group A and Vicryl Plus 4-0 absorbable sutures in group B, while only subcutaneous incisions and sutures were performed in group C. Organ samples of groups A and B were taken for HE staining at 1 and 2 weeks after operation to evaluate the safety of magnesium alloy, and specimens from the supraspinatus tendon and proximal humerus were harvested at 2, 4, 8, and 12 weeks after operation. The specimens were observed macroscopically at 4 and 12 weeks after operation. Biomechanical tests were performed at 4, 8, and 12 weeks to test the ultimate load and stiffness of the healing sites in groups A and B. At 2, 4, and 12 weeks, the specimens were subjected to the following tests: Micro-CT to evaluate the formation of bone tunnels in groups A and B, HE staining and Masson staining to observe the regeneration of fibrocartilage at the tendon-bone interface after decalcification and sectioning, and Goldner trichrome staining to evaluate the calcification. Immunohistochemical staining was performed to detect the expressions of angiogenic factors, including vascular endothelial growth factor (VEGF) and bone morphogenetic protein 2 (BMP-2), as well as osteogenic factors at the tendon-bone interface. Additionally, immunofluorescence staining was used to examine the expressions of Arginase 1 and Integrin beta-2 to assess M1 and M2 macrophage polarization at the tendon-bone interface. The role of the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) signaling pathway in tendon-bone healing was further analyzed using real-time fluorescence quantitative PCR. RESULTS: Analysis of visceral sections revealed that magnesium ions released during the degradation of magnesium alloys did not cause significant toxic effects on organs such as the heart, liver, spleen, lungs, and kidneys, indicating good biosafety. Histological analysis further demonstrated that fibrocartilage regeneration at the tendon-bone interface in group A occurred earlier, and the amount of fibrocartilage was significantly greater compared to group B, suggesting a positive effect of magnesium alloy material on tendon-bone interface repair. Additionally, Micro-CT analysis results revealed that bone tunnel formation occurred more rapidly in group A compared to group B, further supporting the beneficial effect of magnesium alloy on bone healing. Biomechanical testing showed that the ultimate load in group A was consistently higher than in group B, and the stiffness of group A was also greater than that of group B at 4 weeks, indicating stronger tissue-carrying capacity following tendon-bone interface repair and highlighting the potential of magnesium alloy in enhancing tendon-bone healing. Immunohistochemical staining results indicated that the expressions of VEGF and BMP-2 were significantly upregulated during the early stages of healing, suggesting that magnesium alloy effectively promoted angiogenesis and bone formation, thereby accelerating the tendon-bone healing process. Immunofluorescence staining further revealed that magnesium ions exerted significant anti-inflammatory effects by regulating macrophage polarization, promoting their shift toward the M2 phenotype. Real-time fluorescence quantitative PCR results demonstrated that magnesium ions could facilitate tendon-bone healing by modulating the PI3K/AKT signaling pathway. CONCLUSION Biodegradable magnesium alloy material accelerated fibrocartilage regeneration and calcification at the tendon-bone interface in rat rotator cuff tear repair by regulating the PI3K/AKT signaling pathway, thereby significantly enhancing tendon-bone healing.
Animals ; Rotator Cuff Injuries/metabolism* ; Rats, Sprague-Dawley ; Signal Transduction ; Wound Healing/drug effects* ; Alloys/pharmacology* ; Rats ; Proto-Oncogene Proteins c-akt/metabolism* ; Rotator Cuff/metabolism* ; Macrophages/metabolism* ; Magnesium/pharmacology* ; Phosphatidylinositol 3-Kinases/metabolism* ; Vascular Endothelial Growth Factor A/metabolism* ; Male ; Biocompatible Materials ; Bone Morphogenetic Protein 2/metabolism*

OBJECTIVE: To review clinical application and research progress of different types of intelligent responsive hydrogels in repairing articular cartilage injury. METHODS: The animal experiments and clinical studies of different types of intelligent responsive hydrogels for repairing articular cartilage injury were summarized by reviewing relevant literature at home and abroad. RESULTS: The intrinsic regenerative capacity of articular cartilage following injury is limited. Intelligent responsive hydrogels, including those that are temperature-sensitive, light-sensitive, enzyme-responsive, pH-sensitive, and other stimuli-responsive hydrogels, can undergo phase transitions in response to specific stimuli, thereby achieving optimal functionality. These hydrogels can fill the injured cartilage area, promote the proliferation and differentiation of chondrocytes, and expedite the repair of the damaged site. With advancements in cartilage tissue engineering materials research, intelligent responsive hydrogels offer a novel approach and promising potential for the treatment of cartilage injuries. CONCLUSION Intelligent responsive hydrogel is a kind of flexible, controllable, efficient, and stable polymer, which has similar structure and functional properties to articular cartilage, and has become one of the important biomaterials for cartilage repair. However, there is still a lack of unified treatment standards and simple and efficient preparation technology.
Hydrogels/therapeutic use* ; Cartilage, Articular/injuries* ; Tissue Engineering/methods* ; Humans ; Animals ; Chondrocytes/cytology* ; Biocompatible Materials/chemistry* ; Tissue Scaffolds/chemistry*

OBJECTIVE: To review the research progress of strontium (Sr) modified β-tricalcium phosphate composite biomaterials (SrTCP) promoting osteogenesis through immune regulation, and provides reference and theoretical support for the further development and research of SrTCP bone repair materials in bone tissue engineering in the future. METHODS: The literature about SrTCP promoting osteogenesis through immune regulation at home and abroad in recent years was extensively reviewed, and the preparation methods, immune mechanism and application of promoting osteogenesis were summarized and analyzed. RESULTS: The preparation methods of SrTCP include solid-state reaction sintering method, solution combustion quenching method, direct doping method, ion substitution method, etc. SrTCP has immune regulatory effects, which can play an immune regulatory role in inducing macrophage polarization, inducing angiogenesis and anti oxidative stress to promote osteogenesis. CONCLUSION At present, studies have shown that SrTCP can promote bone defect repair through immune regulation. Subsequent studies can start from the control of the optimal repair concentration and release rate of Sr, and further clarify the specific mechanism of SrTCP in promoting angiogenesis and anti oxidative stress, which is helpful to develop new materials for bone defect repair.
Calcium Phosphates/pharmacology* ; Strontium/pharmacology* ; Biocompatible Materials/pharmacology* ; Humans ; Osteogenesis/drug effects* ; Tissue Engineering/methods* ; Bone Substitutes/pharmacology* ; Bone Regeneration/drug effects* ; Animals ; Tissue Scaffolds/chemistry* ; Neovascularization, Physiologic/drug effects* ; Macrophages/immunology*

OBJECTIVE: To review and summarize the research progress on repairing segmental bone defects using three-dimensional (3D)-printed bone scaffolds combined with vascularized tissue flaps in recent years. METHODS: Relevant literature was reviewed to summarize the application of 3D printing technology in artificial bone scaffolds made from different biomaterials, as well as methods for repairing segmental bone defects by combining these scaffolds with various vascularized tissue flaps. RESULTS: The combination of 3D-printed artificial bone scaffolds with different vascularized tissue flaps has provided new strategies for repairing segmental bone defects. 3D-printed artificial bone scaffolds include 3D-printed polymer scaffolds, bio-ceramic scaffolds, and metal scaffolds. When these scaffolds of different materials are combined with vascularized tissue flaps ( e.g., omental flaps, fascial flaps, periosteal flaps, muscular flaps, and bone flaps), they provide blood supply to the inorganic artificial bone scaffolds. After implantation into the defect site, the scaffolds not only achieve structural filling and mechanical support for the bone defect area, but also promote osteogenesis and vascular regeneration. Additionally, the mechanical properties, porous structure, and biocompatibility of the 3D-printed scaffold materials are key factors influencing their osteogenic efficiency. Furthermore, loading the scaffolds with active components such as osteogenic cells and growth factors can synergistically enhance bone defect healing and vascularization processes. CONCLUSION The repair of segmental bone defects using 3D-printed artificial bone scaffolds combined with vascularized tissue flap transplantation integrates material science technologies with surgical therapeutic approaches, which will significantly improve the clinical treatment outcomes of segmental bone defect repair.
Printing, Three-Dimensional ; Tissue Scaffolds ; Humans ; Surgical Flaps/blood supply* ; Tissue Engineering/methods* ; Plastic Surgery Procedures/methods* ; Bone and Bones/surgery* ; Biocompatible Materials ; Bone Regeneration ; Bone Transplantation/methods* ; Bone Substitutes ; Osteogenesis

OBJECTIVE: To review the research progress on silk fibroin (SF)-nerve guidance conduits (NGCs) for peripheral nerve injury (PNI) repair. METHODS: To review the recent literature on PNI and SF-NGCs, expound the concepts and treatment strategies of PNI, and summarize the construction of SF-NGCs and its application in PNI repair. RESULTS: Autologous nerve transplantation remains the "gold standard" for treating severe PNI. However, it's clinical applications are constrained by the limitations of limited donors and donor area damage. Natural SF exhibits good biocompatibility, low immunogenicity, and excellent physicochemical properties, making it an ideal candidate for the construction of NGCs. SF-NGCs constructed using different technologies have been found to have better biocompatibility and bioactivity. Their configurations can facilitate nerve regeneration by enhancing regenerative guidance and axonal extension. Besides, the adhesion, proliferation and differentiation of neurons and Schwann cells related to PNI repair can be effectively promote by NGCs. This accelerates the speed of nerve regeneration and improves the efficiency of repair. In addition, SF-NGCs can be used as regenerative scaffolds to provide biological templates for nerve repair. CONCLUSION The biodegradable natural SF has been extensively studied and demonstrated promising application prospects in the field of NGCs. It might be an effective and viable alternative to the "gold standard" for PNI treatment.
Fibroins/chemistry* ; Peripheral Nerve Injuries/therapy* ; Nerve Regeneration ; Tissue Scaffolds/chemistry* ; Humans ; Guided Tissue Regeneration/methods* ; Biocompatible Materials ; Animals ; Tissue Engineering/methods* ; Schwann Cells/cytology* ; Peripheral Nerves ; Neurons/cytology*

OBJECTIVE: To review recent research progress in the use of auxiliary components of nerve conduits for the treatment of peripheral nerve injuries. METHODS: An extensive review of recent domestic and international literature was conducted to evaluate the role of auxiliary components in nerve conduits for peripheral nerve repair, with a focus on their effects and underlying mechanisms. RESULTS: By incorporating auxiliary components such as bioactive molecules, therapeutic cells, and their derivatives, nerve conduits can create a more biomimetic regenerative microenvironment. This is achieved by providing neurotrophic support, modulating the immune microenvironment, improving blood and oxygen supply, and offering directional guidance for nerve regeneration. Consequently, the nerve conduit is transformed from a simple physical scaffold into an active, bio-functional repair system, which enhances the effectiveness for PNI. CONCLUSION While nerve conduits augmented with auxiliary components demonstrate improved effectiveness, further advancements are required in drug delivery systems and the integration of cellular components. Moreover, most current studies are based on animal or in vitro experiments. Randomized controlled clinical trials are necessary to validate their clinical effectiveness.
Peripheral Nerve Injuries/surgery* ; Nerve Regeneration ; Humans ; Tissue Scaffolds ; Animals ; Guided Tissue Regeneration/methods* ; Tissue Engineering/methods* ; Biocompatible Materials ; Peripheral Nerves ; Drug Delivery Systems

OBJECTIVE: To investigate the antioxidant and osteogenic induction capabilities of calcium phosphate nanoflowers (hereinafter referred to as nanoflowers) in vitro at different concentrations. METHODS: Nanoflowers were prepared using gelatin, tripolyphosphate, and calcium chloride. Their morphology, microstructure, elemental composition and distribution, diameter, and molecular constitution were characterized using scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and energy-dispersive spectroscopy. Femurs and tibias were harvested from twelve 4-week-old Sprague Dawley rats, and bone marrow mesenchymal stem cells (BMSCs) were isolated and cultured using the whole bone marrow adherent method, followed by passaging. The third passage cells were identified as stem cells by flow cytometry and then co-cultured with nanoflowers at concentrations of 0, 0.4, 0.8, 1.2, 1.6, 2.0, 2.4, 2.8, 3.2, and 3.6 mg/mL. Cell counting kit 8 (CCK-8) assay was performed to screen for the optimal concentration that demonstrated the best cell viability, which was subsequently used as the experimental concentration for further studies. After co-culturing BMSCs with the screened concentration of nanoflowers, the biocompatibility of the nanoflowers was verified through live/dead cell staining, scratch assay, and cytoskeleton staining. The antioxidant capacity was assessed by using reactive oxygen species (ROS) fluorescence staining. The in vitro osteoinductive ability was evaluated via alkaline phosphatase (ALP) staining, alizarin red staining, and immunofluorescence staining of osteocalcin (OCN) and Runt-related transcription factor 2 (RUNX2). All the above indicators were compared with the control group of normally cultured BMSCs without the addition of nanoflowers. RESULTS: Scanning electron microscopy revealed that the prepared nanoflowers exhibited a flower-like structure; transmission electron microscopy scans discovered that the nanoflowers possessed a multi-layered structure, and high-magnification images displayed continuous atomic arrangements, with the nanoflower diameter measuring (2.00±0.25) μm; energy-dispersive spectroscopy indicated that the nanoflowers contained elements such as C, N, O, P, and Ca, which were uniformly distributed across the flower region; Fourier transform infrared spectroscopy analyzed the absorption peaks of each component, demonstrating the successful preparation of the nanoflowers. Through CCK-8 screening, the concentrations of 0.8, 1.2, and 1.6 mg/mL were selected for subsequent experiments. The live/dead cell staining showed that nanoflowers at different concentrations exhibited good cell compatibility, with the 1.2 mg/mL concentration being the best (P<0.05). The scratch assay results indicated that the cell migration ability in the 1.2 mg/mL group was superior to the other groups (P<0.05). The cytoskeleton staining revealed that the cell morphology was well-extended in all concentration groups, with no significant difference compared to the control group. The ROS fluorescence staining demonstrated that the ROS fluorescence in all concentration groups decreased compared to the control group after lipopolysaccharide induction (P<0.05), with the 1.2 mg/mL group showing the weakest fluorescence. The ALP staining showed blue-purple nodular deposits around the cells in all groups, with the 1.2 mg/mL group being significantly more prominent. The alizarin red staining displayed orange-red mineralized nodules around the cells in all groups, with the 1.2 mg/mL group having more and denser nodules. The immunofluorescence staining revealed that the expressions of RUNX2 and OCN proteins in all concentration groups increased compared to the control group, with the 1.2 mg/mL group showing the strongest protein expression (P<0.05). CONCLUSION The study successfully prepares nanoflowers, among which the 1.2 mg/mL nanoflowers exhibits excellent cell compatibility, antioxidant properties, and osteogenic induction capability, demonstrating their potential as an artificial bone substitute material.
Animals ; Osteogenesis/drug effects* ; Mesenchymal Stem Cells/drug effects* ; Calcium Phosphates/pharmacology* ; Rats, Sprague-Dawley ; Rats ; Antioxidants/chemistry* ; Cells, Cultured ; Cell Differentiation/drug effects* ; Nanostructures/chemistry* ; Tissue Engineering/methods* ; Bone Marrow Cells/cytology* ; Coculture Techniques ; Tissue Scaffolds/chemistry* ; Male ; Biocompatible Materials/chemistry* ; Cell Survival ; Core Binding Factor Alpha 1 Subunit/metabolism* ; Cell Proliferation