Preparation of functional polyhydroxyalkanoate microspheres and their antibacterial activity and osteogenic effect evaluation / 中国修复重建外科杂志

OBJECTIVE@#To construct polyhydroxyalkanoate (PHA) microspheres loaded with bone morphogenetic protein 2 (BMP-2) and human β-defensin 3 (HBD3), and evaluate the antibacterial activity of microspheres and the effect of promoting osteogenic differentiation, aiming to provide a new option of material for bone tissue engineering.@*METHODS@#The soybean lecithin (SL)-BMP-2 and SL-HBD3 were prepared by SL-mediated introduction of growth factors into polyesters technology, and the functional microsphere (f-PMS) containing BMP-2 and HBD3 were prepared by microfluidic technology, while pure microsphere (p-PMS) was prepared by the same method as the control. The morphology of microspheres was observed by scanning electron microscopy and the water absorption was detected; the release curves of BMP-2 and HBD3 in f-PMS were detected by ELISA kit. The antibacterial effect of microspheres in Staphylococcus aureus and Escherichia coli was tested with the LIVE/DEADTM BacLightTM bacterial staining kit; the biocompatibility of microspheres was tested using Transwell and cell counting kit 8 (CCK-8). The effect of microspheres on osteogenic differentiation was determined by collagen type Ⅰ (COL-1) immunofluorescence staining and alkaline phosphatase (ALP) concentration.@*RESULTS@#In this experiment, the f-PMS and p-PMS were successfully constructed. Morphological characteristics showed that p-PMS surface was rough and distributed with micropores of 1-3 μm, while f-PMS surface was smooth and existed white granular material. There was no significant difference in water absorption between the two groups (P>0.05). The release curves of BMP-2 and HBD3 in the f-PMS and p-PMS were basically the same, showing both early sudden release and late slow release. The antibacterial activity of f-PMS was significantly higher than that of p-PMS in the test that against Staphylococcus aureus and Escherichia coli (P<0.05), but there was no significant difference in biocompatibility between the two groups (P>0.05). The results of osteogenic differentiation of human BMSCs showed that the fluorescence intensity of osteogenic specific protein COL-1 of f-PMS was significantly higher than that in p-PMS, and the activity of ALP in f-PMS was also significantly higher than that in p-PMS (P<0.05).@*CONCLUSION@#The p-PHA have good antibacterial activity and biocompatibility, and can effectively promote the osteogenic differentiation of human BMSCs, which is expected to be applied to bone tissue engineering in the future.

Research progress on medical devices of polyhydroxyalkanoate in orthopedics / 中国修复重建外科杂志

OBJECTIVE@#To review the research progress of natural biomaterial polyhydroxyalkanoate (PHA) in orthopedics.@*METHODS@#The literature concerning PHA devices for bone defects, bone repair, and bone neoplasms, respectively, in recent years was extensively consulted. The three aspects of the advantages of PHA in bone repair, the preparation of PHA medical devices for bone repair and their application in orthopedics were discussed.@*RESULTS@#Due to excellent biodegradability, biocompatibility, and potential osteoinduction, PHA is a kind of good bone repair material. In addition to the traditional PHA medical implants, the use of electrostatic spinning and three-dimensional printing can be designed to various functional PHA medical devices, in order to meet the orthopedic clinical demands, including the bone regeneration, minimally invasive bone tissue repair by injection, antibacterial bone repair, auxiliary establishment of three-dimensional bone tumor model, directed osteogenic differentiation of stem cells, etc.@*CONCLUSION@#At present, PHA is a hotspot of biomaterials for translational medicine in orthopedics. Although they have not completely applied in the clinic, the advantages of repair in bone defects have been gradually reflected in tissue engineering, showing an application prospect in orthopedics.

Performance testing of biodegradable mesh-like microporous balloon combined with calcium phosphate cement for vertebroplasty / 中国组织工程研究

BACKGROUND:Vertebroplasty and kyphoplasty for osteoporotic vertebral compression fractures can result in many complications, such as bone cement leakage and adjacent-level fractures. OBJECTIVE:To verify the possibility of biodegradable mesh-like microporous polymer bal oon for the treatment of osteoporotic vertebral compression fractures. METHODS:Biodegradable mesh-like microporous P(DLLA-CL) bal oons were fabricated by electrospinning technique. Coated bal oons with the same specification was fabricated by coating P(DLLA-CL) onto the same mould. Morphology of the bal oons was observed by scanning electron microscopy. The bal oon leakage was observed by eyes after the injection of water or cement. The initial strength and stiffness were measured by a universal testing machine. The proliferation of MC3T3-E1 cel s on the bal oons was determined by laser confocal microscope and cel counting kit-8 assays. The biodegradation of bal oons in simulated body fluid, porcine pancreatic lipase, and fresh human serum was studied by residual weighing and scanning electron microscopy observation. Burst pressure of bal oons was measured after the bal oon was placed into a hole in the vertebral bone. For the in vitro calcium release tests, the bal oons were fil ed with calcium cement, tied, placed into 6atm ultrapure water, and then the calcium concentration was regularly determined. RESULTS AND CONCLUSION:Mesh-like microporous bal oons presented with good fiber morphology, thickness distribution, and the presence of pores;on the coated bal oon surface, there was absence of specific morphology and porosity. Compared with the coated bal oon, the mesh-like microporous bal oon showed better mechanical properties, liquid permeability and burst pressure, to prevent leakage of bone cement and promote osteoblast adhesion and proliferation. In addition, the degradation of the mesh-like microporous bal oons was more uniform and stable than the coated bal oons, which may increase the calcium concentration in the injured vertebrae and wil be beneficial to the new bone growth and fracture healing.

Bone filling mesh container repairs vertebral compression fractures：biomechanical changes / 中国组织工程研究

BACKGROUND:Percutaneous vertebroplasty and percutaneous kyphoplasty have become the mainstream clinical methods for the treatment of vertebral compression fractures. However, both of them have several shortcomings such as bone cement leakage, spinal stenosis, nerve compression, pulmonary embolism and other issues. OBJECTIVE:To verify the possibility of bone filing mesh container prepared by polyethylene terephthalate for the treatment of vertebral compression fractures. METHODS:The biological properties of bone filing mesh container were examined according to GB/T16886. After sample aging test, the tensile properties of the aged samples and the fresh prepared samples were compared. The expansion and bone cement leakage were evaluated by injecting bone cement into the bone filing mesh container and measuring the pressure. The initial strength and stiffness of the fresh pig vertebrae with calcium phosphate cement injection or with bone filing mesh container filed with calcium phosphate cement were compared. The in vivo bone tissue growth was periodicaly observed after the lumbar vertebra of 4-month-old pigs was implanted with the bone filing mesh container that was then ful of bone cement. RESULTS AND CONCLUSION: The bone filing mesh container had good biocompatibility. Bone filing mesh containers after 2-year storage had the same tensile strength to the fresh bone filing mesh containers. At ambient conditions, after bone cement injection, bone filing mesh containers could be expanded at 5-10 atm and therefore could play the role of uplift; at 7-10 atm, bone cement could leak out from the bone filing mesh container and enter into the interspace between surrounding bone tissues, thus playing the role of adhesion and fixation. The vertebrae after bone cement injection with or without bone filing mesh containers had the same initial strength and stiffness and exhibited bigger initial strength and stiffness than untreated vertebrae. Thein vivo animal experiments proved that bone filing mesh container had no obvious effect on the vertebrae. These findings indicate that the bone filing mesh container can be used to restore the height and strength of the fractured vertebrae. Moreover, it may eliminate bone cement leakage and therefore increase the surgery safety.

Calcium phosphate bone cement and biodegradable mesh-like microporous balloon for vertebroplasty / 中国组织工程研究

BACKGROUND:In vitro experiments have demonstrated that the biodegradable mesh-like microporous baloon made of macromolecular materials has obvious advantage of anti-leakage, which is capable of maintaining calcium homeostasis, has no inhibitory effects on cel growth and on microscopic interdigitation formation between new bone and bone cement. OBJECTIVE:To evaluate the therapeutic effects of biodegradable mesh-like microporous baloon with calcium bone cement on vertebral fractures based on animal experiments. METHODS:The fracture model was established in 48 New Zealand rabbits, in which a bone dril was introduced after successful puncture at sites near left low extremity of the femur. These rabbit models were randomized into two groups: experimental group with calcium phosphate bone cement and biodegradable mesh-like microporous baloon and control group only with calcium phosphate bone cement. Clinical parameters such as blood cel count, biochemistry, and CT/X ray were examined at 1, 3 and 6 months after implantation of the baloon and bone cement. After that, the specimens were fixed for pathological analysis. RESULTS AND CONCLUSION:The operation was performed under general anesthesia with no eventful infusion of bone cement. The expansion of baloon was satisfactory without definite extravasation of bone cement in the experimental group. In the control group, cement diffusion was found with pulmonary embolism occurring in three New Zealand rabbits. No statistical significance for blood cel counts and biochemistry was found between pre- and postoperation or between two groups. The materials in the two groups had favorable biocompatibility with injured bones without obvious immunological response. In the experimental group, the baloon wal was thinned and partial bone tissues grew into the cement at 1 month; at 3 months, a large amount of bone tissues grew into the cement and cement volume diminished; at 6 months, the baloon disappeared and only a smal amount of cement left in the bone tissues. In the control group, it was difficult to determine when the cement degraded. The biodegradable mesh-like microporous baloon combined with calcium bone cement is superior to bone cement alone in the management of vertebral fractures.

Vertebral bodies implanted with biodegradable reticulated balloon and calcium phosphate cement:Changes in the vertebral biomechanics / 中国组织工程研究

BACKGROUND:It has become a focus to look for new vertebral body fil ing materials which have the biomechanical property, biological activity and low cement leakage rate. OBJECTIVE:To investigate the biomechanical characters and cement leakage rate of the vertebral bodies implanted with biodegradable reticulated bal oon and calcium phosphate. METHODS:Thirty-two vertebral bodies from pigs were randomly divided to four groups. For A group, 2.5-3.0 mL polymethacrylate cement was injected into the body through a unilateral thoracic pedicle pathway;for B group, 2.5-3.0 mL calcium phosphate cement were injected by the same protocol;for C group, the biodegradable reticulated bal oons fil ed with 2.5-3.0 mL calcium phosphate cement were implanted;D group, including normal vertebral bodies, was designed as controls. Leakage of bone cement was observed in each group. The load-shift curves were recorded by an electronic universal testing machine (SCHENCK RSA-250). RESULTS AND CONCLUSION:The stiffness and strength of A group were significantly higher than those of D group (P0.05). Cement leakage rate of C group was lower than that of A or B group (P<0.05). Vertebral bodies implanted with biodegradable reticulated bal oons may lead to similar biomechanical characters as the normal vertebral bodies and reduce the cement leakage rate.