Study Of Superparamagnetic Streptomycin Suifate PLA-PEG Microspheres

The treatment of tuberculosis of bone and joint in children has been a major problem to the children's orthopedic surgeons. At present the treatment of osteoarticular tuberculosis is including debridement surgery, drugs chemotherapy of anti-tuberculosis, nutritional support and so on. And the application of anti-tuberculosis drugs is critical to the treatment. The streptomycin sulfate is one of the clinical anti osteoarticular tuberculosis drugs, its main side effect is significant toxicity to the eighth cranial nerve, liver and kidney, and its clinical application has been greatly limited. In recent years, the targeted drug delivery system of the magnetic microspheres shows great prospect in improving the targeting on the lesion of drugs and reducing their toxic side effects.After the ordinary magnetic microspheres injected into the blood circulation, the microspheres are easily identified and cleared as a foreign body by mononuclear phagocyte system (MPS), it will significantly reduce the concentration of drugs to their lesions. In current research, the main strategy is to prepare the stealh magnetic microsphere system via surface modification of microspheres to avoid mononuclear phagocyte cells. In this study, we use poly (d,l-lactic acid)-co-poly (ethylene glycol) (PLA-PEG) which can prevent the phagocytosis of MPS to prepare the magnetic microsphere carrier. Using streptomycin sulfate as the model drug, the superparamagnetic streptomycin sulfate PLA-PEG microspheres (spSPM) with the stealth capabilities were prepared, their featrues wre detcted, and the vitro susceptibility test of superparamagnetic streptomycin sulfate PLA-PEG microspheres were carried out.In this paper, we used chemical coprecipitation which was a more mature method to prepare superparamagnetic chitosan Fe3O4 nanoparticles (spCFN), then using transmission electron microscopy to detect the particles size, vibration sample magnetometer to measure magnetic properties of the nanoparticles, atomic force microscope (AFM) to measure they composition preliminary. The size distribution of the spCFN was between 20 and 30 nm, which had perfect superparamagnetism. The results detected by the AFM showed that the Fe atoms in Fe3O4 and the nitrogen atoms of free aminos in chitosan may have adopted in -NH-Fe- covalent bond. Then spSPM were prepared by the method of multiple emulsion - solvent evaporation method (W / O / W), and the average particle size of these microspheres was 2.467μm. In this paper, we study the encapsulation rate and drug loading rate of these microspheres by the HPLC method which was established to detect the streptomycin sulfate. The magnetic inductions of these microspheres were studied by using the external static magnetic field magnetic. Using the average particle size of the microspheres, magnetic induction, and encapsulation rate of this microspheres to investigate the time of ultrasonic emulsification, the speed of homogenizer and homogenization time, the volume ratio of the aqueous phase to the oil phase, the concentration of PVA in internal and external aqueous phase, which were great factors in the preparation process of spSPM. In this research a better method was found as follows: the concentration of PVA in internal and external aqueous were 1.5% and 0.5%, the volume ratio of the aqueous phase to the oil phase was 1:4, the volume ratio of the multiple emulsion to the external aqueous was 1:20, the time of ultrasonic emulsification was 90 s, the time of homogenization was 90s and the speed of homogenizer was 24 kr/min.In this paper, the release laws in vitro of were studied by using the oscillating magnetic field generator prepared by ourselves. Every 24hours sampled the solution, using the oscillating magnetic field generator to interfering 30 min, to detect the concentration of streptomycin sulfate in SBF by the HPLC, after calculating the release rate, stripping curves were prepared. The results show that the spSPM interfered by the oscillating magnetic field had significant higher release rate compared with spSPM without oscillating magnetic field at each time point. Besides, the release rate of spSPM without oscillating magnetic field was higher than the rate of streptomycin sulfate PLA-PEG microspheres (SPM). This experiment also studied the stability of spSPM in different temperatures. The results showed that the appearance, the drug loading and the magnetic induction of these magnetic microspheres can be stable reserved at -30℃3 months later.The drug susceptibility tests of streptomycin sulfate which were absolute concentration method based on L-J mediums in vitro against Mycobacterium tuberculosis were taken. It was studied whether the efficacy of streptomycin sulfate in the magnetic microspheres had been declined during the prescription and preparation process of this experiment. The drug susceptible culture mediums of mycobacterium tuberculosis were made by the streptomycin sulfate in the release liquid of spSPM, compared with the culture mediums made by streptomycin sulfate only. The results showed that the growth of 15 strains of Mycobacterium tuberculosis in high and low concentrations of streptomycin sulfate culture mediums of experimental group and the control group of of Mycobacterium tuberculosis had inhibited both. The growths of Mycobacterium tuberculosis in high and low concentrations of streptomycin sulfate culture mediums were compared by M-H test, P> 0.05. Compared the experimental group and control group of high and low concentrations of streptomycin sulfate medium on the antibacterial efficacy of Mycobacterium tuberculosis had no significant difference. The resistance rates of experimental group and control group of 15 strains Mycobacterium tuberculosis were 73.33% and 80.00%, compared by Fisher exact test, P> 0.05.And the efficacy of streptomycin sulfate in the magnetic microspheres had not been declined during the prescription and preparation process of this experiment.In this study, the spSPM had complete and uniform appearance, the average partical size of these microspheres was 2.467μm, showed well superparamagnetic in vitro targeting test. The oscillating magnetic field could significantly increase the release of streptomycin sulfate in vitro dissolution experiments. Human type of Mycobacterium tuberculosis in vitro drug sensitivity tests also showed that the spSPM had well antibacterial activities to Mycobacterium tuberculosis.