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Objective·To construct a self-healing injectable hyaluronic acid (HA)-based hydrogel (HAPD-Cu) and investigate the effects of different copper ions on the properties of the hydrogel and its vasogenic efficacy to evaluate its feasibility for clinical wound healing.Methods·Bisphosphonated hyaluronic acid (HAPD) was prepared via a blue-light mediated thiol-ene click reaction between thiolated hyaluronic acid (HASH) and acrylated bisphosphonate (Ac-PD) in the presence of photoinitiator 2959. Then, HAPD was further interacted with Cu2+ through metal coordination to prepare HAPD-Cu hydrogels with different Cu2+ concentrations, i.e. HAPD-Cu1, HAPD-Cu2, HAPD-Cu3 and HAPD-Cu4. The molecular structures of HASH, Ac-PD, HAPD and HAPD-Cu were verified with 1HNMR and FTIR. Microscopic morphology of HAPD-Cu was observed under SEM. The shear-thinning and self-healing properties of HAPD-Cu were verified by rheometer. The Cu2+ release from HAPD-Cu was determined with ICP. Live-dead staining and CCK-8 assay were applied to evaluate the biocompatibility of HAPD-Cu. The in vitro vasculogenic activity of HAPD-Cu was determined by a tubule-forming assay with human umbilical vein vascular endothelial cells and the in vivo vasculogenic activity of HAPD-Cu was assessed by CD31 tissue staining. A rat wound defect model was established in vitro to evaluate its actual repair effect.Results·The preparation of the materials was demonstrated through chemical qualitative and quantitative analytical means. In vitro studies showed that all HAPD-Cu with a loose porous internal structure exhibited outstanding self-healing, injectability and degradability, with a one-week degradation cycle and abrupt release behavior, which can meet the needs of wound healing cycle. All HAPD-Cu showed good biocompatibility except HAPD-Cu4, due to its high Cu2+ concentrations. Moreover, its angiogenic effect in vitro or in vivo was enhanced with increasing Cu2+ concentrations within the permissible Cu2+ concentration range. In vitro wound model experiments also showed that the HAPD-Cu hydrogel significantly promoted wound healing compared with the control group.Conclusion·HAPD-Cu hydrogel constructed via the metal coordination shows excellent shape plasticity, allowing the filling of defective sites in a minimally invasive form, and the release of Cu2+ greatly facilitates the establishment of early vascular networks, with giant potential for use in the repair of clinically irregular wounds.

Objective·To construct a self-healing injectable hyaluronic acid (HA)-based hydrogel (HAPD-Cu) and investigate the effects of different copper ions on the properties of the hydrogel and its vasogenic efficacy to evaluate its feasibility for clinical wound healing. Methods·Bisphosphonated hyaluronic acid (HAPD) was prepared via a blue-light mediated thiol-ene click reaction between thiolated hyaluronic acid (HASH) and acrylated bisphosphonate (Ac-PD) in the presence of photoinitiator 2959. Then, HAPD was further interacted with Cu2+ through metal coordination to prepare HAPD-Cu hydrogels with different Cu2+ concentrations, i.e. HAPD-Cu1, HAPD-Cu2, HAPD-Cu3 and HAPD-Cu4. The molecular structures of HASH, Ac-PD, HAPD and HAPD-Cu were verified with 1HNMR and FTIR. Microscopic morphology of HAPD-Cu was observed under SEM. The shearthinning and self-healing properties of HAPD-Cu were verified by rheometer. The Cu2+ release from HAPD-Cu was determined with ICP. Live-dead staining and CCK-8 assay were applied to evaluate the biocompatibility of HAPD-Cu. The in vitro vasculogenic activity of HAPD-Cu was determined by a tubule-forming assay with human umbilical vein vascular endothelial cells and the in vivo vasculogenic activity of HAPD-Cu was assessed by CD31 tissue staining. A rat wound defect model was established in vitro to evaluate its actual repair effect. Results·The preparation of the materials was demonstrated through chemical qualitative and quantitative analytical means. In vitro studies showed that all HAPD-Cu with a loose porous internal structure exhibited outstanding self-healing, injectability and degradability, with a one-week degradation cycle and abrupt release behavior, which can meet the needs of wound healing cycle. All HAPD-Cu showed good biocompatibility except HAPD-Cu4, due to its high Cu2+ concentrations. Moreover, its angiogenic effect in vitro or in vivo was enhanced with increasing Cu2+ concentrations within the permissible Cu2+ concentration range. In vitro wound model experiments also showed that the HAPD-Cu hydrogel significantly promoted wound healing compared with the control group. Conclusion·HAPD-Cu hydrogel constructed via the metal coordination shows excellent shape plasticity, allowing the filling of defective sites in a minimally invasive form, and the release of Cu2+ greatly facilitates the establishment of early vascular networks, with giant potential for use in the repair of clinically irregular wounds. [ABSTRACT FROM AUTHOR]

BACKGROUND: Injectable hydrogel has a broad application prospect and unique therapeutic plasticity in the treatment of severe spinal cord injury. OBJECTIVE: To review the research progress of injectable hydrogels in spinal cord injury. METHODS: PubMed, Web of Science, Embase, CNKI, Wanfang, VIP, and China Biomedical Literature Database were searched. The key words were “spinal cord injury, spinal fracture, injectable hydrogel” in Chinese and “spinal cord trauma, myelopathy, traumatic, injuries, spinal cord, spinal cord injury, spinal cord transection, spinal cord laceration, post-traumatic myelopathy, spinal cord contusion, injectable hydrogel” in English. The related studies of injectable hydrogel in the treatment of spinal cord injury were screened. RESULTS AND CONCLUSION: Injectable hydrogel can be injected in animal and cell experiments to repair spinal cord injury. Injectable hydrogel has the characteristics of fewer traumas and can fit irregular defects. Injectable hydrogel with electrical conductivity and temperature sensitivity has a good repair function for spinal cord injury in terms of physical and chemical properties. Injectable hydrogel with stem cells or neurotrophic factors is beneficial to nerve regeneration and repair of local microenvironment of spinal cord injury. Injectable composite hydrogels have a bright future in clinical application. [ABSTRACT FROM AUTHOR]

BACKGROUND: Injectable sodium alginate hydrogel can repair bone defects by non-invasive or minimally invasive methods, but the mechanical properties are poor and polyethylene glycol-based hydrogel has elasticity. The composite of materials is expected to improve the mechanical properties and cellular biocompatibility of hydrogel scaffolds. OBJECTIVE: To investigate the physical and chemical properties of glucolactone-sodium alginate/β-tricalcium phosphate-polyethylene glycol hydrogel and its effect on the proliferation and differentiation of murine bone marrow mesenchymal stem cells. METHODS: Gluconolactone as cross-linking agent was set to prepare glucolactone-sodium alginate/β-tricalcium phosphate-polyethylene glycol hydrogel (concentrations of cross-linking agent were 5, 10, and 20 g/L, respectively, which were marked as groups A, B, and C) and glucolactone-sodium alginate/ β-tricalcium phosphate hydrogel (concentration of cross-linking agent was 10 g/L, which was marked as group D). The morphology, mechanical properties, and gelation time of hydrogels in the four groups were characterized. Rat bone marrow mesenchymal stem cells were co-cultured with four groups of hydrogels. The proliferation of cells was detected by CCK-8 assay. Cell survival was observed by Live/Dead fluorescence staining. Osteogenic differentiation was detected by immunocytochemical staining of type I collagen. RESULTS AND CONCLUSION: (1) The filamentous structure similar to adhesion was observed by scanning electron microscope in the groups A, B and C. The pore size distribution of group A was uneven. The pore size of group B was uniform and the porosity was high. The group C had high porosity but different pore sizes. The group D had uneven pore size distribution and low porosity. (2) Physicochemical properties: The compressive stress in group B was higher than that in group D (P < 0.05). With the increase of gluconolactone concentration, the compressive stress of hydrogel in groups A, B and C increased (P < 0.05). The macroscopic performance of hydrogel after 50% compression showed that there were larger cracks in group D and only smaller cracks in group B after compression. The gelation time of groups A, B and C shortened with the increase of gluconolactone concentration, and the gelation time of group B was slightly longer than that of group D (P < 0.05). (3) CCK-8 assay showed that the cell proliferation rate of groups A and B was higher than that of group C (P < 0.05), and that of group B was higher than that of group D (P < 0.05). Live/Dead staining showed that the cell survival rate of each group was higher, but the number of dead cells was more in group C than that in the other three groups. (4) Immunocytochemical staining showed that the cells in groups A, B, and D were polygonal, and the cells in group C were partially round. The green fluorescence intensity in group B was higher than that in the other three groups, and the morphology of the cytoskeleton and microfilaments and the number of cells were also better than those in the other three groups. (5) The results show that the glucolactone-sodium alginate/β-tricalcium phosphate-polyethylene glycol hydrogel has perfect mechanical properties and stability; hydrogel prepared with 10 g/L gluconolactone can effectively promote the proliferation and differentiation of murine bone marrow mesenchymal stem cells. [ABSTRACT FROM AUTHOR]

Chondroitin sulfate (ChS), a kind of natural polysaccharide, is the sulfated glycosaminoglycan which is widely distributed in the extracellular matrix and on the surface of animal cells. ChS possesses various biological activities, such as promoting cartilage growth, regulating growth factors and accelerating wound healing. As a novel biomaterial, in recent years, ChS-based injectable hydrogels have attracted much attention due to their biocompatibility, biodegradability combined with their unique bioactivity, particularly, their applications in the fields of tissue engineering, drug delivery, cell therapy and so on. The gelation systems gelation mechanisms and modification methods of ChS-based injectable hydrogels are reviewed. Herein, the formation methods of the three dimensional network structure in ChS-based injectable hydrogels are mainly introduced, involving physical thermo-induced gelation, chemical crosslinking through Schiff ’s base formation, click chemical reaction, formation of amide bonds and photo-crosslinking and enzyme-catalyzed crosslinking, etc. These developed precursor polymer systems, the corresponding crosslinking methods and mechanisms have been illustrated in detail. In addition, the methods about regulating gelation time, mechanical properties and tissue adhesion are also discussed. The reported strategies can be summarized as the combination of two or more crosslinking methods, adjusting the constitute of the gelation systems and forming composite hydrogels, etc. Finally, future development of ChS-based injectable hydrogels as biomaterials is prospected. We propose that more feasible injectable hydrogel systems with suitable properties will be developed in the future. Furthermore, the relationships among the chemical structure of ChS, the gelation behavior and biological functions should be studied further. In addition, because of the excellent bioactivity of ChS, ChS-based injectable hydrogels applied in other biomedical fields should be explored. [ABSTRACT FROM AUTHOR]

Poly(sarcosine-co-glutamate hydrazide) (P(Sar-co-GH)) with good water solubility and hydrazide group and oxidized sodium alginate (OSA) with aldehyde group were designed and prepared. Under mild conditions, hydrogels composed of P(Sar-co-GH), OSA and carboxymethyl chitosan (CMC) could be prepared based on acylhydrazone bonds formed between P(Sar-co-GH) and OSA and imine bonds formed between CMC and OSA. The structure and mechanical properties of the hydrogels were characterized by FT-IR and rotational rheometer. Results show that the mechanical properties of hydrogels can be adjusted from 840 Pa to 5 690 Pa by changing the content of P(Sar-co-GH) and CMC. The double dynamic chemical bond hydrogel can be injected by the 23 G needle and also exhibit the self-healing behavior within 12 h. Moreover, the hydrogels can undergo repeated gel-sol transition under the regulation of triethylamine(TEA) and hydrochloric acid(HCl). In vitro cytotoxicity and cell culture experiments demonstrate that copolymer and hydrogel extract are nontoxic to mouse embryonic cells（ NIH/3T3） and can support NIH/3T3 growth and proliferation. Overall, a new hydrogel based on polypeptide and polysaccharide is developed by dual dynamic covalent bond, which endows the material with injectability, self-healing properties and pH responsiveness and has great potential in biomedical field. [ABSTRACT FROM AUTHOR]

BACKGROUND: Due to no vascular structure or nerve tissue, cartilage tissue lacks the intrinsic ability of self-repair and regeneration. Therefore, the repair of cartilage defect in clinic remains a challenge. OBJECTIVE: To prepare a thermo-sensitive injectable bioactive hydrogel used for cartilage tissue engineering. METHODS: Agarose/gelatin/hyaluronic acid hydrogel was prepared by mixing 0.4% agarose, 10% gelatin and 10 g/L hyaluronic acid solution. Then 0, 10, 20, and 30 g/L cartilage extracellular matrix particles were added into the hydrogel respectively to prepare four kinds of thermo-sensitive injectable bioactive hydrogels, for further scanning electron microscope, transmission electron microscope, equilibrium swelling ratio, biomechanical strength and degradation rate. The thermo-sensitive injectable bioactive hydrogel containing 20 g/L cartilage extracellular matrix was co-cultured with chondrocyte-bone marrow mesenchymal stem cells for 1, 3, and 7 days, and the cytocompatibility was assessed by live/dead fluorescence double staining. RESULTS AND CONCLUSION: (1) Scanning electron microscope showed that all four hydrogels had good three-dimensional grid structure and large pore size. Transmission electron microscope showed that extracellular matrix particles were evenly distributed in the hydrogels, and the particle size was mainly in the range of 50-200 nm. (2) With the extracellular matrix particle concentration increasing, the equilibrium swelling rate of the hydrogel was decreased. (3) The degradation rate in vitro in the four groups of hydrogels containing 0, 10, 20, and 30 g/L extracellular matrix particles immersed in PBS for 4 weeks was 42.32%, 67.36%, 89.05% and 99.47%, respectively. (4) When the concentration of extracellular matrix particles was added at 0-20 g/L, the biomechanical strength of the hydrogel was gradually increased. (5) Within 7 days after culture, chondrocytes-bone marrow mesenchymal stem cells were uniformly distributed and grew in the hydrogel and proliferated continuously, with the cell survival rate of above 90%. (6) These results showed that the agarose/gelatin/hyaluronic acid hydrogel modified with extracellular matrix particles is a good medical biomaterial that can be used for cartilage tissue engineering. [ABSTRACT FROM AUTHOR]