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    08 August 2022, Volume 26 Issue 22 Previous Issue   
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    Theaflavin-3-gallate modified nano-hydroxyapatite/polycaprolactone composite porous scaffold in bone defect repair
    Liu Ming, Wang Kai
    2022, 26 (22):  3480-3486.  doi: 10.12307/2022.274
    Abstract ( 492 )   PDF (1155KB) ( 105 )   Save
    BACKGROUND: Theaflavin-3-gallate (TF-3G) can significantly inhibit bone resorption and has obvious effects on preventing osteoporosis, but its application on osteogenesis is rare.
    OBJECTIVE: TF-3G was loaded into nano-hydroxyapatite/polycaprolactone composite scaffold to observe its osteogenic effect.
    METHODS: TF-3G solution of different mass concentrations was prepared. The cytotoxicity of TF-3G was detected by CCK-8 assay. According to cytotoxicity test results, bone marrow mesenchymal stem cells were intervened by TF-3G solution of appropriate mass concentration (0, 0.86, 4.30, 8.60, 17.20, 34.4, 68.8, 86, 106 mg/L). CCK-8 assay was used to detect its proliferative activity during osteogenic differentiation. A certain concentration of TF-3G solution was selected to induce bone marrow mesenchymal stem cells to differentiate towards osteogenic direction, and alkaline phosphatase activity detection and alizarin red staining were performed. Nano-hydroxyapatite/polycaprolactone composite porous scaffold was prepared using selective laser sintering rapid prototyping technology. TF-3G was loaded into nano-hydroxyapatite/polycaprolactone composite porous scaffold by solution impregnation and freeze-drying. A 1.5 cm bone defect was made in the radius of adult New Zealand white rabbits. The blank control group was not implanted with any material. The two experimental groups were implanted with nano-hydroxyapatite/polycaprolactone, and TF-3G/nano-hydroxyapatite/polycaprolactone composite porous scaffold. The imaging examination and histological observation were performed after operation. 
    RESULTS AND CONCLUSION: (1) CCK-8 assay showed that 0.86, 4.30, 8.60 mg/L TF-3G promoted the proliferation of bone marrow mesenchymal stem cells; 17.20, 34.4, 68.8, 86, 106 mg/L TF-3G inhibited the proliferation of bone marrow mesenchymal stem cells; 0.86, 4.30, 8.60 mg/L mass concentration was chosen for osteoinduction experiment. (2) Alkaline phosphatase activity detection and alizarin red staining showed that with the increased mass concentration of TF-3G solution, the bone formation effect was enhanced. (3) Lane-Sandhu X-ray scores at 4 and 12 weeks after operation in the two experimental groups were higher than those in the blank control group (P < 0.05), and the scores were higher in the TF-3G/nano-hydroxyapatite/polycaprolactone group than those in the nano-hydroxyapatite/polycaprolactone group (P < 0.05). (4) At 12 weeks after operation, combined with the results of hematoxylin-eosin staining and Masson staining, Huddleston histological score of the two experimental groups was higher than that of the blank control group (P < 0.05), and the score in the TF-3G/nano-hydroxyapatite/polycaprolactone group was higher than that of the nano-hydroxyapatite/polycaprolactone group (P < 0.05). (5) Results concluded that TF-3G can promote the proliferation and osteogenic differentiation of bone marrow mesenchymal stem cells. Nano-hydroxyapatite/polycaprolactone composite porous scaffold loaded with TF-3G can promote the repair of bone defects.
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    Preparation of modified dextran composite hydrogel with osteogenetic effect and in vitro experiment
    Tang Zhenzhou, Gu Yong, Chen Liang
    2022, 26 (22):  3521-3527.  doi: 10.12307/2022.280
    Abstract ( 488 )   PDF (2263KB) ( 98 )   Save
    BACKGROUND: Dextran hydrogel has become a popular tissue engineering material because of its good biocompatibility and injectability, and is extensively used in the repair of hard and soft tissues. However, in the repair of bone defects, pure dextran hydrogel still has insufficient bone formation ability in osteogenesis.  
    OBJECTIVE: To construct a hydrogel material with dextran and modified mesoporous bioactive glass, characterize the material, and investigate its cell adhesion and bone formation ability in vitro.
    METHODS: The dextran was oxidized and modified by sodium periodate to make it rich in aldehyde groups. After aminating and modifying mesoporous bioactive glass, the aminated mesoporous bioactive glass powder was added to the oxidized dextran solution and mixed evenly. Gelatin solution was added to prepare dextrangel-aminated mesoporous bioactive glass nanoparticles (GelDex-AMBGN) composite hydrogel. The bone marrow mesenchymal stem cells were separately inoculated in the oxidized dextran hydrogel and GelDex-AMBGN composite hydrogel. Simply cultured cells were consisted as controls. The cell biocompatibility was detected by Live/Dead fluorescent staining, scanning electron microscope, and CCK-8 assay. The Osteogenic property was detected by alkaline phosphatase staining, alizarin red staining, and immunofluorescence staining for osteocalcin.  
    RESULTS AND CONCLUSION: (1) Live/Dead fluorescence staining results after co-culture for 3 days displayed that bone marrow mesenchymal stem cells in the two hydrogels grew well, maintained high cell viability, and the cell survival rate was higher than 90%. (2) After co-culture for 3 days, scanning electron microscopy results exhibited that bone marrow mesenchymal stem cells spread well on the surface of the two hydrogels. (3) CCK-8 assay results demonstrated that there was no significant difference in the cell proliferation viability of the three groups at 1, 3, 5, and 7 days after culture (P > 0.05). (4) The alkaline phosphatase staining showed stronger results in the composite hydrogel group compared with the oxidized dextran hydrogel and control groups after co-culture for 7 days. The calcium content after co-culture for 21 days was higher in the composite hydrogel group than that of the oxidized dextran hydrogel and control groups (P < 0.05). The immunofluorescence staining for osteocalcin and calcium content detection after co-culture for 21 days revealed stronger results in the composite hydrogel group compared with the oxidized dextran hydrogel group and the control group. (5) The results indicate that GelDex-AMBGN composite hydrogel has good biocompatibility and the osteogenesis ability.
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    Finite element analysis of functionally graded materials for tibial prosthesis
    Li Zhi, Chen Weiyi, Wang Chenyan, Xiang Changxin, Lan Weiwei, Wang Changjiang, Guo Yuan
    2022, 26 (22):  3543-3549.  doi: 10.12307/2022.283
    Abstract ( 557 )   PDF (977KB) ( 86 )   Save
    BACKGROUND: Excessive wear of the tibial insert and aseptic loosening of the prosthesis were the main reasons for the failure of the knee prosthesis after total knee arthroplasty. Owing to the large variation of mechanical strength between prosthesis and bone, it would lead to stress shielding on bone, and then induce aseptic loosening of prosthesis.
    OBJECTIVE: To analyze the stress response of cancellous bone in proximal tibia after functionally graded materials (FGMs) tibial prosthesis implantation by finite element method.
    METHODS: Two FGMs with different porosity parameters (FGM I and FGM III) were designed using titanium-hydroxyapatite composite. The other was prepared by titanium-ideal bone repairing material and named FGM II. The porosity parameters of FGM I were 0.1, 1 and 1, and the porosity parameters of FGM II and FGM  III  were 0.4, 0 and 1. A three-dimensional finite element model of total knee arthroplasty was established, and the stress distributions of FGM and titanium alloy tibial prostheses were analyzed by Abaqus software under three working conditions of 0° extension, 30° and 60° flexion. 
    RESULTS AND CONCLUSION: (1) The maximum Von Mises stresses of FGM tibial prostheses were significantly lower than those of titanium alloy tibial prosthesis, and the stresses at the contact zone between the cancellous bone and the stem end were significantly reduced in FGM tibial prostheses groups. (2) According to the stress curve and average stress of the cancellous bone of the tibia along different paths, the stresses of the cancellous bone of the proximal tibia were increased in FGM tibial prostheses groups compared with titanium alloy tibial prostheses, under different working conditions. Specifically, FGM I was increased by 5.4%-17.3%; FGM II was increased by 1.0%-13.5%; and FGM III was increased by 1.6%-15.4%. (3) The results illustrated that FGM prostheses could increase the stress on the cancellous bone of the proximal tibia and reduce the stress shielding effect of the proximal tibia. Therefore, the risk of aseptic loosening was decreased and the availability of the prosthesis was prolonged. Specifically, FGM I tibial prosthesis was the best among the three kinds of FGM prostheses. 
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    Tissue engineered cartilage constructed by polyurethane composite chondrocytes
    Han Zhi, Wang Zhimiao, Gaxi Sijia, Lu Qingling, Guo Tao
    2022, 26 (22):  3455-3459.  doi: 10.12307/2022.270
    Abstract ( 429 )   PDF (3371KB) ( 50 )   Save
    BACKGROUND: Polyurethane material, as an excellent non-degradable polymer compound, has good stability and excellent mechanical properties, but the biocompatibility of chondrocytes as a tissue engineering material has not been reported.
    OBJECTIVE: To observe the biocompatibility of compound culture of rabbit knee cartilage with polyurethane.
    METHODS: Rabbit knee chondrocytes were extracted by enzyme digestion method, and were cultured with polyurethane composite material when expanded to the third generation in vitro. The proliferation activity of the composite and simple cultured cells was detected by MTT assay. After 2 and 4 weeks of compound culture, inverted microscope, hematoxylin-eosin staining and scanning electron microscope were utilized to observe the chondrocyte growth. Immunohistochemical staining was applied to observe expression of type II collagen.
    RESULTS AND CONCLUSION: (1) MTT assay showed that the proliferation activity of cells cultured for 6, 8 and 10 days was higher than that of cells cultured only (P < 0.05). (2) The inverted microscope showed that after 2 weeks, the cells were almost all over the surface of the material, and some of the cells melted into the material. After 4 weeks, the surface of the material was covered with cells, and clusters of cells filled the pores of the material. (3) Hematoxylin-eosin staining showed that chondrocytes grew stably and adhered to the wall inside the polyurethane. Scanning electron microscopy showed that chondrocytes clustered inside the polyurethane material. (4) Immunohistochemical staining showed that chondrocyte in the scaffold presented the expression of type II  collagen. (5) It is concluded that polyurethane biological scaffolds have good biocompatibility with chondrocytes and are expected to be ideal tissue-engineered cartilage materials.
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    Calcined bovine bone combined with acellular dermal matrix for maintaining the alveolar ridge in dog
    Li Jing, Qiao Wei, Ren Xiaoqi, Shi Hao, Yang Ting, Ma Shaoying, Su Chengzhong, Li Baoxing, Zhao Yaping
    2022, 26 (22):  3445-3449.  doi: 10.12307/2022.268
    Abstract ( 442 )   PDF (1351KB) ( 63 )   Save
    BACKGROUND: In clinic, guided bone regeneration technology is often used to reconstruct the bone defect. That is, the scaffold material is implanted in the bone defect, and then the biological barrier membrane is used to establish a stable environment to ensure the proliferation of osteoblasts and the formation of blood vessels, which has achieved good results.  
    OBJECTIVE: To observe the osteogenic effect of true bone ceramic combined with acellular dermal matrix in tooth socket filling.
    METHODS:  Bovine cancellous bone was calcined to true bone ceramic. The acellular dermal matrix was prepared from split-thickness skin which the epidermis and cellular components have been extracted. Cytotoxicities of true bone ceramic and acellular dermal matrix were evaluated by MTT assay. The second and fourth premolars on both sides of the mandible were extracted in nine beagle dogs. The true bone ceramic was implanted into the socket and covered with acellular dermal matrix. The buccal and lingual gingivae were separated and sutured to close the extraction wound. At 1, 3, and 6 months after surgery, cone beam CT, X-ray and histology were used to evaluate the new bone formation. The experiment was approved by Drug Safety Evaluation Center in China Institute for Radiation Protection (approval No. CIRP-IACUC-(R)2018081).  
    RESULTS AND CONCLUSION: (1) L929 mouse fibroblasts were cultured with the two extracts for 24 hours. Under the inverted microscope, the cells were in good shape without vacuoles or death. MTT assay results showed that the cell survival rate was above 85%, without obvious cytotoxicity. (2) The results of cone beam CT showed that the relative gray value of the implant site increased gradually with the extension of healing time, and the amount of bone formation in tooth extraction wound increased. (3) The X-ray films showed that at 1 month after the operation, the imaging of the implanted site was uniform without obvious osteogenesis. At 3 months after the operation, there was partial osteogenesis. At 6 months after the operation, the implant site had obvious osteogenesis. (4) Hematoxylin-eosin staining showed that a large number of trabeculae were formed 1 month after operation, and the bone trabeculae was evenly arranged, and the true bone ceramic was partly absorbed. Coarse trabeculae structure with a large amount of cartilage and a small amount of calcined bone remained at 3 months after operation. The tooth extraction wound was nearly healed and mature bone tissue was formed, and the bone unit structure was visible; true bone ceramic could not be seen at 6 months after operation. (5) Results suggest that true bone ceramic combined with acellular dermal matrix show good bone formation for extraction socket filling.
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    Treatment of periodontitis in rats with a novel temperature-sensitive gel with immunomodulatory peptide
    Huang Jie, Ren Jing, Peng Pairan, Mu Yandong
    2022, 26 (22):  3514-3520.  doi: 10.12307/2022.279
    Abstract ( 404 )   PDF (1954KB) ( 46 )   Save
    BACKGROUND: Previous studies showed that immunomodulatory peptide DP7 has good antibacterial activity and immunomodulatory activity in vitro.  
    OBJECTIVE: To investigate the therapeutic effect of a new type of immunoregulatory peptide DP7 temperature-sensitive gel on periodontitis in rats.
    METHODS:  The periodontitis model of right maxillary first molar was established in 8-week-old SD rats, and the 48 successfully modeled rats were divided into 6 groups. Except for the natural healing group without treatment, minocycline hydrochloride was injected into periodontal pocket of positive control group. The periodontal pocket of the rest of the four groups were injected with regulatory peptide DP7 concentration 0% (blank gel), 0.1%, 0.3%, 1% temperature-sensitive gel, once a week for 4 weeks. Four weeks later, the periodontal probing depth and the distance between cementum enamel boundary and alveolar crest were examined; and histological and immunohistochemical staining of the right maxilla was performed.  
    RESULTS AND CONCLUSION: (1) The probing depth and the distance between cementum enamel boundary and alveolar crest in 1% and 0.3% DP7 gel treatment groups were lower than those in positive control group (P < 0.05). (2) Hematoxylin-eosin staining showed that the gingival tissue of 0.1%, 0.3%, 1% DP7 gel groups and positive control group was more complete, and the epithelial pedicle process returned to normal, with the orderly array of fibroblasts and new capillaries, and no obvious osteoclasts were observed. The blank gel treatment group and the natural healing group showed the pathological manifestations of periodontitis. (3) Masson staining showed that a large number of new fibroblasts were orderly arranged in the 0.1%, 0.3%, and 1% DP7 gel groups and the positive control group, and bulging collagen hyperplasia and new capillaries were visible. Osteoid or new bone formation was even observed in the 1% and 0.3% DP7 gel groups. However, the blank gel group and the natural healing group had no obvious collagen fiber proliferation and osteoid formation. (4) Immunohistochemical staining showed that the expression levels of tumor necrosis factor-α and interleukin-1β in 0.3% and 1% DP7 gel groups were not significantly different from those in the positive control group (P > 0.05). The expression levels of interleukin-10, bone morphogenetic protein-2 and osteoblast specific transcription factor 2 in 0.3% and 1% DP7 gel groups were higher than those in the positive control group (P=0.000). The expression levels of interleukin-10, bone morphogenetic protein-2 and osteoblast specific transcription factor 2 in 0.3% DP7 gel group were higher than those in the 1% DP7 gel group (P < 0.05). (5) The results showed that 0.3% and 1% immunoregulatory peptide DP7 gel had favorable therapeutic effect on periodontitis, and 0.3% immunoregulatory peptide DP7 gel had the best therapeutic effect.
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    Finite element biomechanical analysis of various bone mineral densities on edentulous mandibular four-implant-supported overdentures fixed using Locator attachments
    Wang Yuan, Zhang Yang
    2022, 26 (22):  3492-3497.  doi: 10.12307/2022.276
    Abstract ( 413 )   PDF (1049KB) ( 71 )   Save
    BACKGROUND: The four-implant-supported overdenture is a commonly used treatment for the edentulous mandibular patient, while the bone mineral density affects the biomechanical outcome, the stability of the implant-supported prostheses, and the health of surrounding tissue, thus influences the long-term therapeutic effect.
    OBJECTIVE: To evaluate the influence of bone mineral density on stress distribution of edentulous mandibular four-implant-supported overdentures via Locator attachments through a three-dimensional finite element analysis. 
    METHODS: Four edentulous mandibular male patients without systemic disease, who had worn four-implant-supported overdentures via Locator attachments, were selected to establish three-dimensional finite element models. Four edentulous mandible models (M1, M2, M3, and M4) made of four different bone types (type 1, 2, 3, and 4, corresponding to the order of cancellous bone whose modulus of elasticity is 9.5, 5.5, 1.6, 0.69 GPa) and embedded with four implants in the interforaminal region were established based on cone beam computerized tomography data. The mandibles were restored using four-implant-supported overdentures via Locator attachments. After 3 forces (F1, F2, and F3) of 120 N magnitudes from various directions applied on the right lower first molar, the von Mises stresses on the cortical and cancellous bones and the implants were determined.  
    RESULTS AND CONCLUSION: (1) For the cortical bone or the cancellous bone, stress concentrations were found on the peri-implant area of models (M1, M2, M3, and M4), particularly on the loading side in all the models. The maximum von Mises stress increased progressively for the cortical bone and implants, but decreased progressively for the cancellous bone from type 1 (M1) to type 4 (M4) bones under three loading conditions. (2) For the implant, stress concentrations were found at the necks of implants and at the contact zones between implants and the Locator abutments, especially on the loading side. The highest maximum von Mises stress was found on M4, while the lowest maximum von Mises stress was found on M1. (3) Results indicate that compact bones (types 1 and 2) are the most suitable bones for edentulous mandibular implant-supported overdentures. Poor bone mineral density (type 4 bone) may increase the risk of biological and mechanical failures. 
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    Preparation and properties of graphene oxide/silk fibroin/rifampicin drug-loading microspheres
    Jiang Chaorui, Xu Yan, Xiong Ying, Zhang Xujing
    2022, 26 (22):  3467-3473.  doi: 10.12307/2022.272
    Abstract ( 689 )   PDF (1075KB) ( 45 )   Save
    BACKGROUND:  The cure rate of severe bone tuberculosis is low and long-term medication is needed, but the adverse reaction of oral drugs is large. Quantitative placement of drug-loaded sustained-release microspheres in lesions can not only ensure drug concentration and precise treatment, but also effectively regulate the rate of drug release and reduce adverse reactions.
    OBJECTIVE: To optimize the preparation process of graphene oxide/silk fibroin/rifampicin microspheres.
    METHODS: Graphene oxide/silk fibroin/rifampicin microspheres were prepared by emulsion method. In determining the concentration of silk fibroin 3.5%, water oil ratio 1:6, Span80 and paraffin ratio 1:10, temperature of 50℃, rifampicin and drug carrier solution than 50 mg:1 mL as quantitative premise, the micromorphology, loading rate and encapsulation rate of the drug-loading microspheres were prepared at different stirring speeds (200, 500, 800 r/min), different organic solvents and water phase volume ratio (1:1, 4:1, 6:1) and different solute ratios of graphene oxide solution to silk fibroin solution (0.1%, 0.25%, 0.5%); and the better preparation technology was determined. 
    RESULTS AND CONCLUSION: (1) Scanning electron microscopy showed that the microspheres prepared at 500 r/min were uniform in size and had good pellet-forming property. When the volume ratio of organic solvent to water phase was 4:1, the pellet forming efficiency of microspheres was better. When the solute ratio of graphene oxide solution to silk fibroin solution was 0.1%, the pellet formation rate of microspheres was higher. (2) Comprehensive test results of drug-loading rate and coating rate, coupled with the graphene oxide/silk fibroin microspheres cytotoxicity experiment result, the microspheres were prepared under the condition of the stirring speed 500 r/min, organic solvent and water phase volume ratio of 4:1, graphene oxide solution and fibroin solution solute ratio of 0.1%. Microsphere formation rate was high; the loading rate was 13.5%; the encapsulation rate was 61%. The microspheres could stably release drugs in vitro, and the cumulative release dosage within 96 hours was about 67.3%. Drug release was processed by diffusion and dissolution.
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    Evaluation of thrombosis in thoracic aortic stent system with covered stent and bare stent
    Ma Jing, Zheng Liping, Sun Ji, Yang Xiaoqin, Pu Linyun, Yuan Tun, Liang Jie
    2022, 26 (22):  3474-3479.  doi: 10.12307/2022.273
    Abstract ( 471 )   PDF (1269KB) ( 60 )   Save
    BACKGROUND: The thoracic aortic stent system instruments generally consist of covered stent, bare metal stent and corresponding delivery system. They may trigger more concerns about the safety of thrombosis in clinical practice by reason of the complexity in structure of such instruments. 
    OBJECTIVE: To provide a more rational idea for the design and analysis of premarket safety evaluation of such implantable vascular devices combined with covered stent and bare stent.
    METHODS: Three experimental pigs were selected and implanted with the thoracic aortic stent system. The system includes the thoracic aortic stent system transporter, covered stent and bare stent. The coated stent was inserted into the descending aorta of the experimental pig, and the bare stent was subsequently led in to concatenate the distal end of the covered stent. During the operation, the surface thrombosis of the extracorporeal part of the transporter was observed. Seven days after the surgery, the covered stent, transporter and bare stent were taken out to perform scanning electron microscopy. Meanwhile, the vessels contacted the bare stent and coated stent were separated to process histological observation.
    RESULTS AND CONCLUSION: (1) Gross observation displayed that no thrombosis or thrombosis-related lesions were observed in the important organs of the experimental pigs, and no thrombotic occlusion was observed in the lumen of the blood vessels at the implantation site. (2) Scanning electron microscopy showed that thrombosis of several microns to hundreds of microns could be seen on the surface of the transporter of the coated stent system and the bare stent system, and thrombosis of several microns to hundreds of microns could be seen on the surface of the coated stent, bare stent and the vascular surface contacted with the stent. (3) Histological observation showed intimal hyperplasia at the contact site of the coated stent. Most of the new tissue was composed of fibrin network and a large number of red blood cells. Simultaneously, inflammatory cells were infiltrated inside the tissue, and inflammatory cell aggregation was observed at the edge of a few new tissues, and new small vessels were formed locally in the new tissues. Furthermore, the intima of the vessels at the contact site of the bare stent was proliferated, and the new tissue was mostly composed of necrotic cells, with local aggregation of inflammatory cells. (4) The results revealed that the influence of the implantable instruments used in combination with coated stents and bare stents on the blood vessels after implantation varied with different components. Consequently, it was required to consider the particularity of the composition of the stent itself and evaluate and analyze each component in combination with the way of its clinical usage.
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    Construction of tissue-engineered urine outflow tract using adipose stem cells and expanded polytetrafluoroethylene for canine urinary diversion
    Liu Junwei, Yang Sixing, Xiong Yunhe, Song Chao, Liao Wenbiao, Meng Lingchao, Li De, Song Qianlin, He Ziqi, Li Bin
    2022, 26 (22):  3487-3491.  doi: 10.12307/2022.275
    Abstract ( 392 )   PDF (872KB) ( 58 )   Save
    BACKGROUND: Tissue engineering technology was used to construct and form tissue engineering, tubes which can significantly reduce the incidence of various perioperative complications with good anti-urine leakage performance in vitro.  
    OBJECTIVE: To evaluate the feasibility of using adipose stem cells and expanded polytetrafluoroethylene to construct tissue-engineered urine outflow tract in vitro for canine urinary diversion surgery.
    METHODS: In the experimental group, adipose stem cells were isolated and cultured from four female beagles, and then differentiated into urothelial cells in vitro for 14 days. The differentiated cells were implanted on the inner surface of expanded polytetrafluoroethylene tubes to form a tissue-engineered urinary diversion device. Bladders were removed from dogs (only 1.0 cm × 1.0 cm of trigonometric area was retained), and both ends of the tissue engineered urinary diversion device were anastomosed with trigonometric area and abdominal wall respectively to complete the urinary diversion operation. The samples were collected at 1, 2, 4 and 8 weeks postoperatively. The control group (two dogs) underwent urinary diversion with expanded polytetrafluoroethylene engineered tube, and samples were collected 8 weeks after operation. The animal experiment was approved by laboratory animal ethics committee of Renmin Hospital of Wuhan University (approval No. WDRM(Fu)20180810).  
    RESULTS AND CONCLUSION: (1) There were different degrees of adhesion between the two groups of implanted tissue-engineered urinary diversion devices and the abdominal wall or intestinal wall. Two dogs of the experimental group had mild hydronephrosis, and no serious complications such as urinary exosmosis or infection. One dog in the control group developed severe urinary fistula and died 7 weeks after operation. The tissue-engineered urinary diversion device of the other dog was covered with stones. (2) Hematoxylin-eosin staining showed that thin epithelial cells with loose intercellular connections began to grow continuously in the outflow tract lumen of the experimental group 1 week after operation. At 2 weeks postoperatively, the intercellular connections became dense and the number of epithelial cells increased. Four weeks after operation, the cells began to accumulate and thicken, and gradually changed into a multi-layer structure. The entire lumen was covered by the epidermis, and neovascularization was observed 8 weeks after surgery. (3) The results showed that it was feasible to construct tissue-engineered urine outflow tract together with expanded polytetrafluoroethylene after adipose stem cells were differentiated into urothelial cells for urinary diversion in beagles. The inner cavity of outflow tract could form a tightly connected urothelial cortex with the function of draining urine and preventing urinary extravasation.
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    Cell co-culture and in vivo biocompatibility of poly(L-lactic caprolactone)/silk fibroin small-diameter artificial blood vessels
    Liu Yue, Jiang Ziyi, Li Jingjing, Meng Kai, Zhao Huijing
    2022, 26 (22):  3505-3513.  doi: 10.12307/2022.278
    Abstract ( 481 )   PDF (1896KB) ( 132 )   Save
    BACKGROUND: The autologous bypass grafting is the best surgical scheme. However, the source of autologous blood vessels is limited, which is far from meeting the huge clinical needs. Therefore, the research and development of small-diameter artificial blood vessels are of great significance. However, small-diameter artificial blood vessels have not been truly applied in clinical practice due to the problems of easy thrombosis and intimal hyperplasia. 
    OBJECTIVE: To explore the growth of human umbilical vein endothelial cells and vascular smooth muscle cells on poly(L-lactic caprolactone)/silk fibroin electrospun membrane, the patency, histocompatibility and degradability of poly(L-lactic caprolactone)/silk fibroin small-diameter artificial blood vessels in rats.
    METHODS: Electrospinning technology was used to prepare poly(L-lactic caprolactone)/silk fibroin small-caliber artificial blood vessels. Vascular endothelial growth factors were loaded on the artificial blood vessel, and heparin was finally loaded on the artificial blood vessel. Human umbilical vein endothelial cells and vascular smooth muscle cells were respectively seeded on artificial blood vessels loaded and unloaded with vascular endothelial growth factor. The growth of cells on artificial blood vessels was analyzed by confocal laser scanning microscope, scanning electron microscope, and MTT assay. Transwell membrane in cell chamber was replaced with poly(L-lactic caprolactone)/silk fibroin electrospun membrane. Human umbilical vein endothelial cells and vascular smooth muscle cells were inoculated on poly(L-lactic caprolactone)/silk fibroin material for cell co-culture. The growth of cells on poly(L-lactic caprolactone)/silk fibroin materials was analyzed by confocal laser scanning microscope, scanning electron microscope, and MTT assay. The artificial blood vessel loaded with vascular endothelial growth factor and heparin was implanted into the rat carotid artery. The patency, histocompatibility, and degradability of the artificial blood vessel were detected.
    RESULTS AND CONCLUSION: (1) Cells separately seeded on artificial blood vessels: Confocal laser scanning microscope, scanning electron microscope, and MTT assay showed that the number of human umbilical vein endothelial cells seeded on the artificial blood vessel loaded with vascular endothelial growth factor was more than that of the artificial blood vessel without vascular endothelial growth factor. The number of vascular smooth muscle cells loaded with and without vascular endothelial growth factor was basically the same. (2) Two kinds of cells seeded together on the artificial blood vessel: Confocal laser scanning microscope, scanning electron microscope, and MTT assay showed the number of cells in co-culture was larger than that of single cells in non-co-culture environment, but less than the sum of the number of two single cells. (3) Implantation experiments in animals: The laser Doppler perfusion imaging showed that the blood flow velocity decreased at 1 day after implantation of the artificial blood vessel, and then gradually decreased, until the third week it had not been surveyed. Histological and immunohistochemical staining exhibited inflammatory cells appeared on the third day after implantation of artificial blood vessel, and disappeared one week later. At the third week, blood flow was observed in the sample, and a uniform endodermis and new angiogenesis were formed on the inner wall of the sample. Scanning electron microscopy showed that the fibers were basically broken at the 6th week of implantation of the artificial blood vessel, and the fibers became thinner. At the 4th week, the retention strength of artificial blood vessel suture decreased to 42.2% of the original data. (4) These findings suggest that poly(L-lactic caprolactone)/silk fibroin small-diameter artificial blood vessels have good cytocompatibility and histocompatibility, but the patency and degradability need to be improved. 
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    Mechanical properties of silk fibroin/type I collagen/hydroxyapatite scaffolds based on low-temperature 3D printing
    Meng Lulu, Liu Hao, Liu Han, Zhang Jun, Li Ruixin, Gao Lilan
    2022, 26 (22):  3550-3555.  doi: 10.12307/2022.304
    Abstract ( 500 )   PDF (818KB) ( 47 )   Save
    BACKGROUND: With the rapid development of 3D printing technology in tissue engineering, a variety of scaffold materials prepared by 3D printing are widely used in mandibular defect repair. 3D printing technology brings new possibilities for mandibular defect repair. 
    OBJECTIVE: The 3D bionic bone scaffold material was constructed by low-temperature 3D printing technology, and the internal structure of the scaffold was precisely controlled, and the mechanical properties of the scaffold were analyzed.
    METHODS: Under the same volume, by changing the interlacing angle of the printed scaffold wire harness and the wire harness, low-temperature 3D printing technology was used to print silk fibroin/type I collagen/hydroxyapatite scaffolds with different angles (30°, 45°, 90°) and polycaprolactone/hydroxyapatite scaffolds (a total of 6 sets of scaffolds). The uniaxial compression mechanics experiment was loaded to 6 groups of scaffolds at a compression rate of 0.5%/s, compressed to 30% strain to observe the relationship between stress and strain. The stress relaxation experiment was applied to the three printing angles of silk fibroin/collagen I/hydroxyapatite scaffolds at a compression rate of 0.5%/s at 10%, 20%, and 30% strain, and the relaxation retention time was 3 hours to observe the relationship between stress and time. In the creep experiment, the silk fibroin/collagen I/hydroxyapatite scaffold with an angle of 90° was compressed and printed at a constant pressure of 2.5, 3.75, and 5 kPa, and the creep retention time was 3 hours to observe the relationship between strain and time.
    RESULTS AND CONCLUSION: (1) Uniaxial compression mechanics experiment: The mechanical properties of 3D printed silk fibroin/type I collagen/hydroxyapatite scaffold and polycaprolactone/hydroxyapatite scaffold compression showed that the 90° scaffold had higher Young’s modulus than the 30° and 45° scaffolds under the same compression strain. (2) Stress relaxation experiment: When the compression rate, compression strain and compression angle were constant, the stress of silk fibroin/type I collagen/hydroxyapatite scaffold decreased rapidly with the extension of relaxation time, then slowly decreased. With the extension of relaxation time, the stress of the scaffold decreased rapidly in the beginning time (within 1 600 seconds), and in the later period (3 700 seconds). When the compression rate and compression strain were kept constant, the initial and stable stress values of silk fibroin/type I collagen/hydroxyapatite scaffolds with 90° printing angle were higher than those of scaffolds with 30° and 45° printing angle. When the compression rate and compression angle were constant, the initial and stable stress values of silk fibroin/type I collagen/hydroxyapatite scaffolds increased with the increase of compression strain. (3) Creep test: With the extension of creep time, the strain of 90° silk fibroin/type I collagen / hydroxyapatite scaffolds increased rapidly in the initial stage (within 500 seconds), then increased slowly, and finally leveled off. The strain range of the scaffolds was 35% to 55% at 2.5 kPa, and 43% to 57% at 3.75 kPa. The strain of the scaffold ranged from 45% to 57% under 5 kPa. 
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    Preparation and imaging experiment of a new type of safe near-infrared luminescent nanoparticles
    Xu Xinzhi, Zhang Yue, Jin Ying, Jin Chunxiang
    2022, 26 (22):  3450-3454.  doi: 10.12307/2022.269
    Abstract ( 468 )   PDF (1023KB) ( 119 )   Save
    BACKGROUND: Near-infrared luminescent carbon dots have tissue penetration that blue-green luminescent carbon dots do not have. They are ideal imaging agents. However, they are easily degraded in the body and cannot reach target tissues. This experiment combines them with nanoparticles, and it can reach the target through the circulatory system to achieve the purpose of real-time imaging. 
    OBJECTIVE: To prepare mesoporous organosilica nanocapsules-carbon nanodots (MON-CDs) with imaging capability and high safety.
    METHODS:  Utilizing the micelle/precursor co-template assembly strategy, using traditional tetraethoxysilane and bis[3-(triethoxysilyl)propyl]tetrasulfide) as the material, cetyltrimethylammonium chloride as the stencil agent, and triethanolamine as the alkaline catalyst, mesoporous organosilica nanoparticle (MON) was successfully prepared and carbon dots were added to the entire system to prepare MON-CDs. Transmission electron microscope and fluorescence spectrometer were applied to detect the structure, morphology and fluorescence intensity of nanoparticles. Photoacoustic image system and scanning laser confocal microscope were utilized to verify imaging ability, and in vivo photoacoustic imaging in mice was proven. CCK-8 was used to test the biosafety of MON-CDs solutions of different mass concentrations.  
    RESULTS AND CONCLUSION: (1) The transmission electron microscope showed that the particle size of MON-CDs was (50.0±4.6) nm, which was spherical, uniform in size, and had good dispersibility. The pores were clearly visible and the carbon dots were mixed in it. Fluorescence detection showed that the carbon dots and mesoporous organic-inorganic hybrid silica nanoparticles were successfully connected. (2) CCK-8 detection showed that when the mass concentration of MON-CDs solution was within 200 mg/L, there was no obvious cytotoxicity. (3) Scanning laser confocal microscope showed that when MON-CDs were incubated with MCF-7 cells for 1 hour, the nanoparticles had already been taken up by cells, and most of them were concentrated near the cell membrane. When the CDs were incubated for 2 hours, the amount of nanoparticles accumulated into the cells increased, and the nanoparticles were mainly distributed in the cytoplasm. In addition, the uptake of nanoparticles occurred in most of the cells. (4) Photoacoustic imaging showed that with the proliferation of MON-CDs solution mass concentration, the in vitro photoacoustic signal intensity increased. At 6 hours after MON-CDs solution injection via tail vein, photoacoustic signals were observed at the tumor tissues of breast cancer mice. (5) The results showed that MON-CDs have good biosafety and possess near-infrared luminescence, and demonstrate good imaging capabilities under photoacoustic imager and laser confocal microscope.
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    Potential of bacterial nanocellulose/polydopamine composite tubes as small-diameter artificial blood vessel
    Liu Liang, Hu Gaoquan, Wei Zhao, Chen Lin, Hong Feng
    2022, 26 (22):  3535-3542.  doi: 10.12307/2022.282
    Abstract ( 555 )   PDF (1619KB) ( 168 )   Save
    BACKGROUND: There is a lack of small-caliber artificial blood vessels (< 6 mm) in clinical application. 
    OBJECTIVE: To explore the potential of bacterial nanocellulose/polydopamine (BNC/PDA) composite tubes for small-caliber artificial blood vessels. 
    METHODS: Bacterial nanocellulose small-caliber artificial blood vessel was prepared through an external silicone tube reactor, and the purified cellulose tube was immersed in dopamine solutions of different mass concentrations (0.1, 0.5, 1.0, 1.5, 2.0 g/L) for self polymerization reaction. After preparation of BNC/PDA composite tubes, the microstructure, infrared spectrum, density, water holding capacity, water permeability, burst and suture strength, axial mechanical properties, and blood and cell compatibility of the bacterial nanocellulose tube and BNC/PDA composite tubes were characterized. 
    RESULTS AND CONCLUSION: (1) The field emission scanning electron microscope showed that the inner surface of all tubes was a 3D network structure built by nanofibers, with uniform fiber distribution and compact structure. With the increase of dopamine mass concentration, the fiber diameter of artificial blood vessels increased. (2) As the mass concentration of dopamine increased, the density, burst and suture strength and axial mechanical properties of artificial blood vessels increased, and the water penetration and water holding capacity decreased. (3) The hemolysis rate and platelet adhesion test results showed that the hemolysis rate of the bacterial nanocellulose tube and the BNC/PDA composite tubes were both non-hemolytic grades. The composite tube adhered to platelets less than the bacterial nanocellulose tube. The whole blood coagulation test results showed that the composite tubes had stronger blood coagulation performance than the bacterial nanocellulose tube. (4) CCK-8 experiment results showed that compared with simple bacterial nanocellulose, the BNC/PDA-0.1 composite tubes could promote the proliferation of human umbilical vein endothelial cells; the other four composite tubes inhibited cell proliferation; and BNC/PDA-1.5 and BNC/PDA-2.0 composite tube showed obvious cytotoxicity. The results of calcein fluorescence staining showed that the cells on the surface of the simple bacterial nanocellulose, BNC/PDA-0.1, BNC/PDA-0.5, and BNC/PDA-1.0 composite tubes could continue to proliferate, among which the number of cells on the surface of the BNC/PDA-0.1 composite tubes was more than that on simple bacterial nanocellulose. (5) The results show that the BNC/PDA composite tubes have certain potential to be used in small-caliber artificial blood vessels, and it can be further grafted with active macromolecules to achieve functionalization.
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    Fabrication and safety evaluation of collagen sponge
    Liu Chaoyuan, Gao Tianfang, Huang Wei
    2022, 26 (22):  3460-3466.  doi: 10.12307/2022.271
    Abstract ( 820 )   PDF (1513KB) ( 74 )   Save
    BACKGROUND: Collagen could be extracted from the animal, and the collagen sponge could be fabricated by vacuum freeze-drying technology, which is used in clinical hemostasis. Besides, it would be degraded in vivo. However, there are some concerns about collagen biomaterials, owing to the potential risk of carrying viruses and immune rejection. The biological safety of collagen hemostatic sponge was achieved by removing the terminated peptide and inactivating the virus. 
    OBJECTIVE: To investigate the immunogenicity and the validity of virus inactivation of collagen hemostatic sponge in commercial process.
    METHODS:  The collagen was extracted from bovine tendons through acid-enzymatic hydrolysis. After the vacuum freeze-drying technology, the porous collagen hemostatic sponge was prepared. The immunogenicity was investigated by insert 1 or 4 pieces of collagen sponge in Wistar rats subcutaneously. The physical sign, blood routine examination, T lymphocyte proliferation, and immunoglobulin content were examined at 1, 4, 8 and 12 weeks. Pseudorabies virus, vesicular stomatitis virus, porcine parvovirus and porcine encephalomyocarditis virus were chose as indicator virus to investigate the validity of virus  inactivation by three batches of crushed bovine tendons.
    RESULTS AND CONCLUSION: (1) The collagen sponge was extracted and fabricated by freeze-drying technology in clean workshop in commercial process. The irradiation sterilization was conducted after the whole process of packaging of the collagen sponge. (2) After inserting 1 or 4 pieces of collagen sponge, the physiological signs, routine blood tests, NK cell killing activity, T lymphocyte proliferation, and immunoglobulin content of the rats were found to be normal. (3) There was no detectable virus, which could reduce the titer of these four kinds of indicator virus by more than four logs, after the acid-enzymatic process of collagen sponge. In addition, sensitive cells inoculation and blind cultivation for three generations were performed on the virus titer samples that could not be detected, and the results showed no cytopathic effect. (4) Immunogenicity and virus inactivation test results showed that the prepared collagen hemostatic sponge had good biological safety which could be used in clinical hemostasis.
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    Mechanical properties and biocompatibility of porous ZnO/hydroxyapatite composites with different porosities
    Meng Zengdong, Zhu Bin, Zhang Yanan, Luo Lilin, Zhang Yuqin
    2022, 26 (22):  3498-3504.  doi: 10.12307/2022.277
    Abstract ( 440 )   PDF (1428KB) ( 56 )   Save
    BACKGROUND: Earlier studies have found that adding zinc oxide to nano-hydroxyapatite and making it porous can significantly improve the apatite-forming ability and simultaneously have good biocompatibility, but the increase in porosity will lead to the deterioration of mechanical properties.
    OBJECTIVE: To observe the changes in the microstructure, pore characteristics, mechanical properties, in vitro mineralization and degradation properties of porous zinc oxide/hydroxyapatite composites under different porosities, as well as the cell compatibility of the composites under suitable porosity.
    METHODS: The porosity of the composite material was controlled by changing the added amount of pore former (medical grade ammonium bicarbonate). Porous zinc oxide/hydroxyapatite composite materials with different porosities (42%, 51%, 62%) were prepared by spark plasma sintering technology to study the microstructure, pore characteristics, mechanical properties, in vitro mineralization and degradation properties of three kinds of composite materials. Rabbit bone marrow mesenchymal stem cells were inoculated on the surface of porous zinc oxide/hydroxyapatite composite material with appropriate porosity, and cell adhesion and proliferation were observed. 
    RESULTS AND CONCLUSION:  (1) Scanning electron microscopy showed that with the increase of porosity, the number of pores in the composite material increased significantly; the through-hole structure increased; and microcracks appeared on the surface. The pore size of the composite material was between 0-500 μm. With the increase of porosity, compressive strength and elastic modulus of the composite were reduced; the compressive strength decreased from 148 MPa to 56 MPa; the elastic modulus decreased from 6.5 GPa to 3.5 GPa. (3) In vitro degradation and mineralization experiments showed that with improved composite surface porosity, bone apatite deposition species increased, and the degradation rate was accelerated. (4) Based on the above experimental results, the composite material with the porosity of 42% was selected to be co-cultured with rabbit bone marrow mesenchymal stem cells. The direct contact culture experiment showed that the cells grew and adhered well on the surface of the composite material and inside the void; the composite material extract CCK-8 assay showed that with the extension of culture time, rabbit bone marrow mesenchymal stem cells proliferated rapidly. (5) The results showed that the porous zinc oxide/hydroxyapatite composite material with the porosity of 42% had good mechanical properties, degradation properties and biocompatibility.
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    Silk fibroin/nano hydroxyapatite composite combined with icariin can promote the proliferation and differentiation of bone marrow mesenchymal stem cells into nucleus pulposus like cells
    Guo Xiaopeng, Liu Yingsong, Shang Hui
    2022, 26 (22):  3528-3534.  doi: 10.12307/2022.281
    Abstract ( 479 )   PDF (1411KB) ( 70 )   Save
    BACKGROUND: In recent years, using tissue engineering technology to repair intervertebral disc degeneration has become a research hotspot in the field of spinal surgery.  
    OBJECTIVE: To compare the effect of silk fibroin/nano hydroxyapatite composite material combined with icariin and silk fibroin/nano hydroxyapatite composite in the repair of intervertebral disc degeneration.
    METHODS:  Silk fibroin/nano hydroxyapatite hydrogel was prepared by physical blending and porogen. The hydrogel was directly physically mixed with icariin to prepare a hydrogel containing icariin (10 mmol/L). Animal models of intervertebral disc degeneration in New Zealand white rabbits were established by nucleus pulposus aspiration method. Thirty-six rabbits were randomly divided into 3 groups, with 12 in each group. The model group was injected with PBS using microinjector into intervertebral disc. The control group was injected with silk fibroin/hydroxyapatite hydrogel and bone marrow mesenchymal stem cell suspension. The experimental group was injected with fibroin/hydroxyapatite hydrogel containing icariin and bone marrow mesenchymal stem cell suspension. The normal group (n=12) was not modeled and did not receive any treatment. X-ray and MRI examinations were performed 4, 8, and 12 weeks after surgery. Histology (hematoxylin-eosin staining and toluidine blue staining), RT-PCR detection (type II collagen, proteoglycan, Sox9 mRNA), and western blot assay (type II collagen, proteoglycan, Sox9 protein expression) were performed 12 weeks after surgery.  
    RESULTS AND CONCLUSION: (1) X-ray films showed that the height of the intervertebral disc in the model group gradually decreased at 4, 8, and 12 weeks after the operation, while the height of the intervertebral disc in the control group and the experimental group increased gradually. Among them, the rabbit disc height in the experimental group recovered better than the control group. (2) MRI demonstrated that at 4, 8, and 12 weeks after surgery, the T2 weighted image signal value of the rabbit intervertebral disc in the model group gradually decreased, and gradually increased inthe control group and the experimental group, of which the experimental group increased more significantly. (3) Hematoxylin-eosin staining showed that the nucleus pulposus tissue of the model group was obviously damaged, and the number of nucleus pulposus cells was remarkably reduced; the control group was less complete with a small amount of nucleus pulposus-like cell proliferation in the central nucleus pulposus. In the experimental group, nucleus pulposus tissue was intact, and a large number of nucleus pulposus-like cell proliferation could be seen in the central nucleus pulposus. (4) Toluidine blue staining showed that the nucleus pulposus of the model group was not stained, moderately stained in the control group, and deeply stained in the experimental group. (5) RT-PCR and western blot assay showed that the expression levels of type II collagen, proteoglycan and Sox9 in the model group were lower than those in the normal group (P < 0.05). The expression levels of type II collagen, proteoglycan and Sox9 in the control and experimental groups were higher than those of the model group (P < 0.05). The expression levels of type II collagen, proteoglycan and Sox9 in the experimental group were higher than those in the control group (P < 0.05). (6) The results have shown that the silk fibroin/hydroxyapatite hydrogel combined with icariin can promote the proliferation and differentiation of bone marrow mesenchymal stem cells into nucleus pulposus like cells, increase the synthesis of cell matrix and promote the repair of degenerative intervertebral disc.
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    Research hotspots of magnesium alloy biomaterials in an in vivo animal
    Guo Yangyan, Yu Zhengwen, Zhang Jian
    2022, 26 (22):  3556-3565.  doi: 10.12307/2022.285
    Abstract ( 484 )   PDF (937KB) ( 147 )   Save
    BACKGROUND:  As a new generation of biodegradable materials, magnesium alloy has good mechanical properties, biocompatibility, and degradability, which is one of the research hotspots in the field of biomaterials. 
    OJECTIVE: To summarize current status and problems of magnesium alloy biomaterials in animals in recent years. 
    METHODS: The articles were searched by using the databases of PubMed and CNKI. The key words were “metal biomaterials, degradable metals, magnesium alloy materials, magnesium-based implants, vascular stents, animal experiment, corrosion rate, biosafety” in Chinese and in English. As a result, 70 articles were applied after reading and analyzing the titles and abstracts of the articles published between January 2016 and June 2021.
    RESULTS AND CONCLUSION: (1) The safety and degradation rate of magnesium alloy are the main influencing factors for its clinical application as a biodegradable biomedical material. (2) Magnesium alloy has great potential in internal fixation of fracture, repair of bone defect after bone tumor operation, ligament fixation and coronary artery stenosis as vascular stent. Magnesium alloy has excellent histocompatibility and no potential safety hazard in short-term application, but there is still no long-term biosafety research result. (3) The magnesium alloy stent can support blood vessels in the early stage of vascular lesion. After the normal function of the blood vessels in this part is restored, the stent is absorbed and metabolized by the body. When the vascular stenosis and obstruction occur again, the magnesium alloy stent can be implanted again to achieve the purpose of repeated repair. (4) At present, magnesium alloy has become a hot material in the field of medical device research, but the current research results are only obtained in animal experiments or small-sample clinical trials. (5) At present, researchers have basically reached a consensus that magnesium alloy alloying, surface treatment and preparation of composite materials can effectively solve its safety problems and the defects of fast degradation rate. However, previous studies have shown that there is still a lack of standardized reference standards for animal selection, implant preparation, and evaluation methods in magnesium alloy experiments. (6) Therefore, it is necessary to perfect and formulate relevant reference standards for magnesium alloy experiments in the future for the development of rigorous and good preclinical research, which will also provide strong theoretical support for the effectiveness and safety evaluation of magnesium alloy materials.
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    Nanoparticles: a novel strategy for the treatment of ischemic stroke
    Xiakeerzhati•Xiaohalati, Wang Xiaobei, Wang Lin
    2022, 26 (22):  3566-3572.  doi: 10.12307/2022.286
    Abstract ( 739 )   PDF (751KB) ( 116 )   Save
    BACKGROUND: As a class of nano-scaled biomaterials, nanoparticles have exhibited outstanding performances in promoting neural stem cells proliferation and differentiation, delivering therapeutic molecules and drugs, and scavenging excessive radical oxygen species.
    OBJECTIVE: To summarize the properties of nanoparticles for the treatment of ischemic stroke, and to analyze their therapeutic effects and related treatment mechanism on the pathological process of ischemic stroke.
    METHODS: The author searched the relevant articles collected by PubMed, Wanfang, and China National Knowledge Infrastructure database from January 2000 to December 2020. The key words were “ischemic stroke, nanomaterials, nanoparticles, nanozyme” in English, and “ischemic stroke or cerebral infarction, nanoparticles, nanozyme” in Chinese. Based on the inclusion and exclusion criteria, 79 articles were finally selected for review.
    RESULTS AND CONCLUSION: Nanoparticles have made great progress in the treatment of ischemic stroke. A large number of studies have shown that (1) nanoparticles can be used as a drug delivery system to deliver neuroprotective drugs and molecules and to achieve targeted drug delivery across the blood-brain barrier. (2) Nanoparticles can promote brain tissue regeneration through their inherent anti-oxidation properties. (3) Nanoparticle combined with stem cell therapy can improve the efficacy of endogenous neurogenesis and exogenous stem cell transplantation. However, a very little proportion of studies have focused on this field, and meanwhile lacking a systematic design standard and optimal formulation of nanoparticles for ischemic stroke treatment. In the future, it is necessary to further explore the disease mechanism of ischemic stroke and fully understand the interaction between nanoparticles and biological systems, thereby designing a brain-targeted nanoparticle therapy system to promote its clinical application.
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    Hydrogel-based adipose tissue engineering strategies for vascularization
    Wu Shuhan, Zhu Xulong, Bai Lu, Zhang Feifei, Lin Guangshuai, Li Jiang, Du Jia, Li Jianhui
    2022, 26 (22):  3573-3579.  doi: 10.12307/2022.287
    Abstract ( 498 )   PDF (934KB) ( 57 )   Save
    BACKGROUND: At present, the construction of engineered adipose tissue through seed cells, scaffold materials and extracellular microenvironment is one of the most potential directions for use in soft-tissue defect reconstructions. However, graft resorption attributed to lack of effective vascular network and blood supply is a major limitation for wider application of adipose tissue engineering. 
    OBJECTIVE: To review the related research on how to establish a blood vessel network and effective engineered adipose tissue vascularization based on hydrogel scaffold. 
    METHODS: The computer was used to search for articles on CNKI, Wanfang, and PubMed databases from January 2010 to June 2020. The search terms were “tissue engineering, adipose tissue, adipose-derived stem cell, hydrogel, vascularization” in Chinese and English. Relevant articles were summarized and finally 88 articles were included to analyze the results. 
    RESULTS AND CONCLUSION: There are four main vascularization strategies for tissue engineered fat constructed with hydrogel materials: Tissue engineering chamber model; adipose-derived stem cells co-cultured with vascular endothelial cells; hydrogel scaffolds loaded with cytokines; application of suitable hydrogel scaffold with angiogenic properties. Therefore, the application of hydrogel materials to establish highly biomimetic adipose tissue units, combined with effective vascularization techniques, will further improve the efficiency of soft tissues repair and reconstruction.
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    Application of polycaprolactone modified biological barrier membrane in bone tissue engineering
    Lu Haiping, Lang Xuemei, Zhang Cheng, Ju Songli, Zhang Yi, Wang Xin
    2022, 26 (22):  3580-3585.  doi: 10.12307/2022.288
    Abstract ( 440 )   PDF (960KB) ( 100 )   Save
    BACKGROUND: The use of polycaprolactone barrier membrane can prevent the surrounding fast-growing fibrous tissue and epithelial tissue from entering the bone defect thus enhancing bone regeneration process. In addition, the osteogenic modification of the polycaprolactone barrier membrane has been explored by researchers.
    OBJECTIVE: To summarize the modification strategies of polycaprolactone barrier membrane, and look forward to new osteogenesis strategies.
    METHODS: CNKI, Wanfang, VIP, and PubMed databases were searched with key words of “polycaprolactone membrane, osteogenesis, bone substitute material, natural polymer, artificial polymer, metal ion, growth factor, stem cell” in both Chinese and English for articles regarding polycaprolactone barrier membrane published from January 2000 to February 2021.   
    RESULTS AND CONCLUSION: The first problem to be solved for polycaprolactone is to reduce the hydrophobicity when combining with other materials. At present, many methods have been developed as connecting bridges to make polycaprolactone more compatible with other materials, such as dopamine, heparin, and collagen. However, the combination of polycaprolactone with different materials requires diverse conditions, and new hydrophobicity modification methods still need to be explored. In addition, polycaprolactone material and its modification strategies have been widely studied. The research of the incorporation of polycaprolactone with bone substitute material, natural polymer and artificial polymer has achieved pleasing results. Nevertheless, due to the limitation of osteogenesis of composite materials, new osteogenic materials still need to be developed. Presently, there are some substances (such as exosomes and extracellular matrix) that have been verified to exhibit superior osteogenic ability for many kinds of tissues, such as peripheral nerve regeneration and vascular regeneration. The incorporation of polycaprolactone with those active substances is expected to develop into new regeneration strategies for tissue engineering. 
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    Theoretical research and technical application of bone repair materials in the treatment of calcaneal fractures
    Tian Chong, Gao Bo, Yu Hongwei, Wang Pei
    2022, 26 (22):  3586-3591.  doi: 10.12307/2022.289
    Abstract ( 469 )   PDF (811KB) ( 36 )   Save
    BACKGROUND: With the development of medical biotechnology, various artificial bone substitutes have appeared, providing a broader prospect for the future clinical treatment of calcaneal fractures.
    OBJECTIVE: To summarize the methods and progress of different bone repair materials in the treatment of calcaneal fractures.
    METHODS: The first author used computer to search CNKI database and PubMed database. Search terms were “calcaneus fracture, autologous bone, allogenic bone, artificial bone” in Chinese and English used in the title and abstract. The articles related to the material characteristics, biocompatibility and application effects of the search terms were selected, and the articles in the same field recently or published in authoritative journals were selected. 
    RESULTS AND CONCLUSION:  Autologous bone is the first choice for clinical repair of bone defects, but there are problems such as limited supply, donor site complications, and secondary trauma. Later, allogenic bone, calcium phosphate, calcium sulfate, and Kirschner wire, steel plate, and hollow screws as internal fixation materials have achieved satisfactory results. With the development of biotechnology, on the basis of previous work, bone materials containing bone morphogenetic protein, platelet-rich plasma, and bone marrow aspiration concentrate have been applied in clinical practice, and satisfactory results have been achieved. At present, the bone graft materials used in the nonunion of calcaneal fractures can achieve relatively satisfactory results. The application of bone morphogenetic protein, platelet-rich plasma, and bone marrow aspiration concentrate can achieve better results. Simultaneously, with the development of biotechnology, various new composite bone graft materials will become the mainstream for the treatment of bone nonunion in the future.
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    Materials of interbody fusion cage: advantages and focus of clinical application
    Jin Herong, Cui Jingbin, Shao Cang
    2022, 26 (22):  3592-3597.  doi: 10.12307/2022.290
    Abstract ( 570 )   PDF (776KB) ( 66 )   Save
    BACKGROUND: Interbody fusion cage has become an indispensable implant in spinal surgery. With the development of materials science and 3D printing technology, the application prospects of different materials need to be studied.
    OBJECTIVE: To analyze in detail and prospect the materials of interbody fusion cage in combination with the latest clinical data and the research and development of new materials.
    METHODS: The first author searched CNKI, VIP, PubMed, Elsevier and other databases from January 1989 to December 2020 by computer, focusing on the current clinical application of interbody fusion cage materials in spinal surgery with key words of “Interbody fusion cage, Biocompatibility, Orthopedic implants, Spinal surgery, 3D printing interbody fusion cage, Biodegradable materials, PEEK fusion cage, Silicon nitride fusion cage” in English and Chinese. 
    RESULTS AND CONCLUSION: There are a variety of interbody fusion cages, including metal materials, polymer materials, inorganic non-metal materials and composite materials. Currently, PEEK and its composite materials are commonly used in clinic. Other materials have new clinical data. With the development of 3D printing technology and the emergence of new materials for 3D printing, metal porous titanium alloy fusion cage has been highly evaluated in clinic. In addition, the filling materials in the cage hole gradually developed from autogenous bone and allogeneic bone to absorbable artificial bone and recombinant bone morphogenetic protein. 
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    Measures to reduce the leakage rate of bone cement during vertebral augmentation
    Yang Liu, Du Jianwei
    2022, 26 (22):  3598-3601.  doi: 10.12307/2022.291
    Abstract ( 359 )   PDF (648KB) ( 51 )   Save
    BACKGROUND: At present, vertebral augmentation has become the prior choice for the treatment of osteoporotic vertebral compression fractures. How to reduce the leakage rate of intraoperative bone cement has attracted the attention of clinical workers.
    OBJECTIVE: To review the current clinical research on reducing the leakage rate of bone cement in terms of surgical methods and bone cement factors.
    METHODS: PubMed, Wanfang, and CNKI databases were searched for articles about bone cement leakage during vertebral augmentation published from 1987 to 2021 with the key words of “cement leakage, vertebral augmentation, osteoporotic vertebral compression fractures” in Chinese and English. The articles which were irrelevant and repetitive were excluded, and 43 articles were reserved for review.
    RESULTS AND CONCLUSION: Vertebral augmentation surgery has various surgical methods. Percutaneous vertebroplasty and kyphoplasty are the two most common methods. Kyphoplasty can reduce the leakage rate of bone cement. The factors of bone cement itself, such as the type of bone cement, viscosity and injection volume, can also affect the leakage rate of bone cement. The clinical consequence of bone cement leakage is related to the type of leakage, and the most common is paravertebral leakage; and the most serious complication is intraspinal leakage. With the deepening of research, clinical workers have innovated many technologies to deal with bone cement leakage, but the effect is not obvious. Robot assisted vertebroplasty is a technology worthy of clinical practice. It is believed that with the continuous update and development of technology, the problem of bone cement leakage will be effectively solved.
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    Angiogenesis induced by bone bioscaffold materials
    Li Duchenhui, Tian Ai, Tang Zhenglong
    2022, 26 (22):  3602-3608.  doi: 10.12307/2022.292
    Abstract ( 580 )   PDF (729KB) ( 81 )   Save
    BACKGROUND: The vascular network induced by the bioscaffold material is essential for cell survival and new bone formation. In recent years, scholars of bone tissue engineering have paid more attention to the influence of different scaffold materials on angiogenesis during bone regeneration.
    OBJECTIVE: To describe the characteristics of bone scaffold materials that can promote angiogenesis and their role in promoting vascularization. 
    METHODS: The first author used “osteogenesis, biomaterials, bone defect, angiogenesis, vascularization” as the English search terms, and used “osteogenic differentiation, biomaterials, bone defect, angiogenesis, vascularization” as the Chinese search terms to search relevant articles published from 2016 to 2020 in the PubMed and CNKI databases. After screening and summarizing, the authors finally chose 82 relevant articles for review.
    RESULTS AND CONCLUSION: The early establishment of the vascular network after the implantation of scaffold materials can provide sufficient nutrients and transport metabolites, while the slow formation of local vascular network that leads to insufficient blood supply will delay osteogenesis or even fail to form new bones. Researchers modified the scaffold materials by various methods, such as the change of the physical and chemical properties of the implanted scaffold materials, the loaded sustained-release system with growth factor, and the combination of trace elements or simulation of periosteal structure, to promote early angiogenesis in the process of osteogenesis. However, due to limitations of the current manufacturing technology and the lack of relevant basic research, studies about bioscaffold materials focused on the change of a single factor. In the future, with the improvement of manufacturing technology, the research and development of more new biomaterials will produce bioscaffold materials that integrate porous, micro-nano and multi-level surface morphologies. Meanwhile, with the precise study of the secretion and release of various growth factors during osteogenesis, as well as the precise grasp of the slow-release and controlled-release systems, the angiogenesis-promoting effect of bioscaffold materials will be further improved.
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