ABSTRACT
Objective To fabricate an anti?tuberculosis controlled drug release coating with Ti?PDA?PEG?PLGA?INH and to investigate its surface characteristics, in vivo and in vitro drug release behavior, and tissue biocompatibility. Methods 4?arm?polyethylene glycol (PEG) was synthesized first. Then cover the surface of titanium (Ti) with a layer of poly dopamine (PDA) by Michael addition reaction. Use porous starch and 4?arm?PEG as a carrier, load with isoniazid (INH), then attach to the surface of titanium by casting or sol?gel dip coating methods, and then cover with a layer of poly lactic?co?glycolic acid (PLGA) by the same method, to fabricate the Ti?PDA?PEG?PLGA?INH composite coating finally. The functional group of 4?arm?PEG was charac?terized by proton nuclear resonance spectroscopy (HNMR). The surface characteristics of Ti?PDA?PEG?PLGA?INH were evaluated by scanning electron microscope (SEM), while drug release behaviors were detected by high performance liquid chromatography (HPLC) and the cumulative release rate was calculated, and carry out the antibacterial performance in vitro. The animal model of femoral condyle bone defect was established in 25 New Zealand white rabbits. Titanium rods covered with PDA?PEG?PLGA?INH coating were implanted into defect area. INH concentrations were detected by HPLC in venous blood, muscle and bone tissue at each time point postoperatively. Another 12 rabbits were randomly divided into experimental group and control group, the experi?mental group was implanted with titanium tablets and titanium rods coated with PDA?PEG?PLGA?INH in the paraspinous muscle and left femoral condyles respectively, while the control group was implanted with a blank sheet of titanium tablets and titanium rods in the same place. Hematoxylin and Eosin Staining were used to observe the biocompatibility of the composite system in vivo at 28 and 56 days postoperatively. Results Ti?PDA?PEG?PLGA?INH controlled drug release coating uniformly distributed on the surface of plates and rods, with translucent form and smooth surface. In vitro INH release kinetics exhibited a short?burst release during the first 8h, and the cumulative release of the INH was about 65%. On the 9th day, the cumulative release of the INH was about 90%, and then the release tended to be flat, and the drug release behavior in vitro continued more than 20d. In vivo release test showed that the concentration of INH in vein blood, muscle and bone tissue around the composite system was increased steadi?ly postoperatively. On about the 28th day, the concentration reached the max. However, the INH concentrations in muscle and bone tissue around the composite system were still higher than the minimum inhibitory concentration (MIC) on the 56th day. The antibacterial test in vitro showed that the titanium tablets coated with PDA?PEG?PLGA?INH formed obvious bacterial inhibition zones. The pathological results indicated that mild inflammatory reaction was seen in the 4th week postoperatively, and the reac?tive capsule formed with loose connective tissue. In the 8th week postoperatively, there's no obvious inflammation occurred, and the reactive capsule became more dense and thicker. Conclusion The study successfully fabricated the Ti?PDA?PEG?PLGA?INH anti?tuberculosis controlled drug release coating, with reasonable release behavior both in vivo and in vitro, effective antibac?terial effect of Mycobacterium tuberculosis in vitro and good tissue biocompatibility, which is a potentially effective drug delivery system for spinal tuberculosis.
ABSTRACT
Adolescent idiopathic scoliosis has a high incidence in orthopedics,researches about its etiology begins early.However,it is still unclear until now.Idiopathic scoliosis trends to a familial aggregation,and its inheritance is diverse,which suggests idiopathic scoliosis can be the result of the interaction of many factors and major genes.It is reported that the inheritance mode of idiopathic scoliosis includes autosomal dominant inheritance,X-linkage dominant inheritance and polygenic inheritance.With the consummate of genome genetic map and the development of genetic technology at recent years,scholars have gained much advancement through the researches in gene screening,candidate gene,gene mutation and animal model.Further study should focus on the accurate site of related genes.
ABSTRACT
[Objective]To establish 3D finite element model of adolescent idiopathic scoliosis.Stress analysis on established 3D finite element model was done to compare the specific quantity of stress among every vertebra.[Method]Under the help of related softwares,3D finite element model was established from CT scan of a adolescent idiopathic scoliosi.A number of points were chosen on the model.Stress analysis was done in normal loading.[Result]Vertebral wedging and stress distribution showed significant regularity.The result was the largest in the apical region,and showed a gradual decrease to the end vertebral.[Conclusion]Relative biomechanical and clinical analysis can be easily conducted on 3D finite element model of scoliosis.It is possible to analyze diversity of stress on different conditions.