| Bone tumors that occur in the bone or bone tissue originated in various components of the tumor, its nature can be divided into benign and malignant. Benign bone tumor treatment by local curettage or resection, if complete resection, the prognosis is good. The main treatment of malignant bone tumor is surgical resection combined with chemotherapy. The incidence of malignant bone tumors in extremities of the extremities was1%, high mortality and high disability make it one of the common diseases that endanger human health. Bone tumor resection not only caused the bone biomechanical defects, destroyed the continuity and integrity of the bone,but unable to completely remove the local tumor cells, which is the local recurrence of hidden trouble. The traditional system of systemic chemotherapy for improve the effect of chemotherapy, effectively kill tumor tissue often need to increase the dose, while large doses of chemotherapeutic drugs will inevitably bring about a series of systemic toxicity, often leads patients cannot tolerate. Therefore, local chemotherapy become a better treatment method, In twentieth Century 70, some scholars put forward the concept of tumor local Sustained-release Chemotherapy.Inspired by this, chemotherapy drugs and bone graft material was prepared by the combination of composite material can achieve the effect of local delivery has become a hot research topic. The development of polymer composite materials has brought the opportunity for it, PLGA is a kind of biodegradable polymer material, which has good biocompatibility and biological degradation, which has advantages of high drug loading, drug release time and degradation time can be adjusted, Beta-TCP also has good biocompatibility, degradation is also very complete, its main component iscomposed of bone calcium, At the same time for the degradation of new bone formation with calcium, phosphorus and other elements, promote the formation of new bone. This experiment will PLGA/ beta-TCP and methotrexate(MTX) composite material made of anti tumor drug, to observe the effect of the material on the bone defect repair in New Zealand white rabbits and the drug release properties of the material.1. MTX/PLGA/ beta-TCP composite materials preparationThe quality of PLGA dissolved into the 10 times the mass of six 1,4two oxygen ring solution, the average is divided into 2 parts, weigh PLGA quality beta-TCP and 2 times the quality of sodium chloride solution were added to 2 solution, second solution was added to the beta-TCP mass of8% MTX powder, fully mix, and fill into the mold, ultra low temperature refrigerator was- 4 degrees, 20 degrees C and 80 degrees C in gradually frozen 2 hours each, remove the dry, salt, once again in a freeze dryer to dry for 48 hours, standby save out into the refrigerator at a temperature of 4DEG C.2. The performance test of MTX/PLGA/ beta-TCP CompositesThe surface and interior of the composite material were porous, and the pore distribution was uniform, the hole and bore hole were penetrated each other, the diameter of the hole was about 160-250μm, the average was 199± 22μm. The porosity of the material was(86± 3)%, with excellent connectivity.The linear fitting equation of MTX in PBS solution is: Y=0.0455X-0.0009(R2=0.9986). This equation can be calculated according to the material drug loading rate is(2.8±0.1)%, encapsulation efficiency is(71.5±3.0)%.The determination of drug release materials were observed for 12 weeks, the observation time point was first, 3, 5, 7, 14, 21, 28, 35, 42, 49,56, 63, 70, 84 days, the results showed that the release process of the material was stable, there was a certain sudden release phenomenon, theaccumulated release of the first 34% days, to fourteenth days accumulated release of 48%.3. Bone defect model establishment, material implantation and animal evaluation of the distal radius in New Zealand white rabbits40 New Zealand white rabbits, were randomly divided into 3 groups,first groups and second groups with 10 rats in each group: 20, third. The radial defect of left anterior limb was produced by surgical operation under general anesthesia, and the length was about 8mm. The first groups did not implant any material, the second group was implanted with PLGA/-TCP material, and the third group was implanted with MTX/PLGA/-TCP composite, the observation time was 12 weeks, the osteogenic evaluation of the implanted material was evaluated by the general situation, imaging observation, histological observation, biomechanical measurement and bone morphometric analysis. The drug release properties of the third groups of experimental animals were evaluated by HPLC, and the concentrations of blood and blood were 4, 8 and 12 weeks after operation.The results showed that: fourth weeks and eighth weeks after operation, 3groups of New Zealand white rabbits underwent left upper limb X-ray examination, were evaluated with Lane-Sandhu score X ray, First groups(blank control group) New Zealand white rabbits bone defect site is still obvious, the score was significantly lower than the other two groups,Second groups of New Zealand white rabbit(PLGA/ beta-TCP Material Group) bone defect site repair faster than third New Zealand white rabbits(MTX/PLGA/ beta-TCP group), the corresponding score is also higher,two kinds of materials that have differences in bone repair effect, which may load and composite material of anti tumor drugs MTX. MTX has some cellular toxicity to the surrounding tissues, and can delay the process of bone repair. Twelfth weeks after operation, X-ray examination again, first groups of bone defects still exist, the second groups and third groups of bone defect in the radius of New Zealand rabbits have been repaired,Lane-Sandhu X- ray score reached bone healing level, that the load of MTX bone repair materials have certain cytotoxicity to the surrounding tissue during prometaphase repair, tissue repair delay, but after the standard time to bone healing, can still reach the level of bone healing. Histological examination revealed twelfth weeks after surgery: second groups and third groups of New Zealand white rabbit bone defect site implant material basic degradation, the new bone tissue only a small amount of material residues,show that the material degradation is good. Bone morphometric results show: Group 2 and group 3 new bone ingrowth rate respectively(90.9 ±1.8)% and(88.7± 2.3)%, far higher than the group 1(10.1±2.2)%, and group 2 and group 3 comparison, there was no significant difference(P >0.05), The biomechanical test of the repair specimens also showed that there were no significant differences in bone strength between the second groups and third groups of bone defects. Peripheral blood concentrations of Third New Zealand rabbits were detected at fourth weeks, eighth weeks and twelfth weeks after surgery, the results showed that the concentrations of peripheral blood were 0.23±0.05μg·ml-1, eighth weeks and twelfth weeks except for fourth weeks, and the concentrations of peripheral blood were not detected. Fourth weeks, eighth weeks, Twelfth weeks after the operation, the material within the muscle tissue around the 10 mm drug concentration detection, The results showed that the concentration of local blood drug was decreased, and the fourth week was 5.27±0.46μg·ml-1, and the eighth week was 2.71±0.54μg·ml-1, and twelfth weeks to0.71±0.18μg·ml-1, The concentration is still much higher than the lowest concentrations of MTX, which indicates that the PLGA/ beta-TCP/MTX material can release MTX effectively at twelfth weeks. |
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