| This thesis aimed to prepare poly(lactic-co-glycolic acid)(PLGA) microspheres containing sinomenine hydrochloride(SM) using an oil-in-oil(O/O) solvent evaporation method. The microspheres were also combined with PLGA-PEG-PLGA thermosensitive in situ gel to treat rheumatoid arthritis by intra-articular injection. The sinomenine-PLGA microspheres-thermosensitive in situ gel had a one-month release period. Compared to other traditional dosage-forms, the prepared microspheres showed advantages of slow drug release to the focus, reduced dosing frequency, enhanced bioavailability and reduced the side effects.Some properties of SM such as the stability of SM against acidity, alkalinity, oxidization, high temperature, high humidity and light, the n-Octanol-water partition constant,the solubility of SM in various kinds of solvents and the differential scanning calorimetry analysis on the drug, were detected. Analytical method of determination for the content and release rate of SM in vitro by HPLC was established. The results showed that the drug remained stable when exposed to acidity, oxidization, high temperature, high humidity and light. The solubility test results showed that SM was easily soluble in PBS dissolution medium(101.38mg/m L), soluble in water(95.45mg/m L), slightly soluble in acetonitrile(3.36mg/m L) and almost insoluble in liquid paraffin(concentration could not be detected). We can know from the determination of oil/water partition coefficient that with the increase of p H, the oil-water partition coefficient of drugs became greater. Finally,the HPLC method had high sensitivity and good reproducibility which was suitable for the detection of SM.Through pre-formulation research and preliminary experiments, concrete steps for an oil-in-oil emulsion solvent evaporation method were established along with the microspheres quality evaluation index. Factors that had an influence on average particle size, drug loading and releasing rate were investigated. Using an orthogonal test with the critical process factors the procedure was optimized. The in vitro drug release behavior of the microspheres prepared with this optimized method was then investigated. The microspheres were analyzed using scanning electron microscopy, microscope and differential scanning calorimetry analysis. The optimum method was found to be: 10000 g/mol of PLGA molecular weight, 1:5 weight ratio of SM to PLGA, 20 mg/m L of PLGA concentration, 1% span80 concentration in the internal phase, 750 rpm/min of emulsification speed,10 min of emulsification time, 500 rpm/min of solvent evaporation speed, 6 hours of solvent evaporation and 25℃ of solvent evaporation temperature. Microspheres prepared at these settings had good dispersion, a full rounded form and smooth surface without holes. The average particle size and average drug loading were 5.36 μm and 5.19% respectively. In vitro release tests showed that the microspheres can slowly release for a month with release rate of 3.54% in 0.5 h, 19.0% in 24 h, with no burst in the late period. The release behavior of the microspheres followed the Korsmeyer-Perppas model, which means microspheres released its drug mainly by dispersal mode. Differential scanning calorimetry analysis results showed that, no drug peak but just PLGA peak was found in the absorption spectrum of SM-PLGA-MS.Lastly, the PLGA-PEG-PLGA triblock copolymer was chosen as the thermosensitive in situ gel material. The appropriate gel concentration was screened out and its properties were investigated. The differences of the in vitro release behavior between SM 、SM-PLGA-MS 、 SM-thermosensitive in situ gel and SM-PLGA sustained release microsphere-thermosensitive in situ gel were compared. Test results showed that when the mass concentration of gel was 20%, its gelling temperature was 32℃ with good capability to gel in vitro. It took three days for the gel to become hydrosol totally. In vitro release results showed that under the same operating conditions, SM took 1.5 hours in dissolution medium to release drug completely, which shows little inhibition of drug release from the dialysis bag. However, it took 3 days for the SM- thermosensitive in situ gel to release drug completely because the gel required more time to become hydrogel so that the framework of the gel can no longer be the barrier for drug releasing. In vitro release curve of SM-PLGA sustained release microsphere was similar to that of SM-PLGA sustained release microsphere-thermosensitive in situ gel and both can released completely within a month.In conclusion, the SM-PLGA-MS prepared using this oil-in-oil emulsion solvent evaporation method had advantages of high drug loading, low initial burst and slowly drug release in vitro for a month, which reached the design objective. This method shows much potential for application for intra-articular injections for the treatment of rheumatoid arthritis. |
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