Preparation And Evaluation Of Koumine-loaded Sustained-Release Porous Microspheres

Koumine is a major alkaloidal constituent of Gelsemium elegans Benth..Our previous study showed that koumine had significant pharmacological effects for chronic pain and rheumatoid arthritis with low toxicity,which indicated that koumine has a great pharmaceutical potential.Therefore,an oral koumine-loaded sustained-release preparation were developed in order to meet the needs of long-term treatment,and decrease the fluctuation of the plasma concentration.In this paper,koumine-loaded sustained-release porous poly lactic-co-glycolic acid（PLGA）microspheres were prepared by optimizing the formulation and the technological parameter in the light of its morphology,particle size,capsulation efficiency,drug loading and release profile in vitro.The preliminary stability of the microspheres were also investigated via influence factors test and acceleratation test.1 Preparation of koumine-loaded sustained-release porous microspheresKoumine-loaded sustained-release porous microspheres were prepared using modified W₁/O/W₂ emulsification solvent evaporation method.The results showed that molar ratio 50:50,viscosity 0.18 dL·g^-1,222 mg/mL of PLGA,10 mg of koumine;3%NH₄HCO₃ as porogen;5%polyethylene glycol-4000（PEG-4000）as inner aqueous phase emulsifier;2%polyvinyl alcohol（PVA）as outer aqueous phase emulsifier were chosen to be the optimized formulation.In addition,100 W of colostrum emulsification power and 1400 r/min of multiple emulsion stir speed were also chosen to prepare the microspheres.2 Characteristic of koumine-loaded sustained-release porous microspheresKoumine-loaded sustained-release porous microspheres were white loose powder with good dispersibility.Differential scanning calorimetry（DSC）and fourier transform infrared spectrometer（FTIR）showed that koumine was successfully encapsulated in PLGA rather than adsorbed on the surface of microspheres.Electron microscope scanning showed that many small holes distributed on the surface and the shell of microspheres,which the interior was hollow.In addition,particle size was measured by optical microscope and the diameter was 31.28±7.78μm;encapsulation efficiency and drug loading were detected by ultra performance liquid chromatography（UPLC）and they were 74.19%±0.63%and 3.13%±0.1%respectively,the reproducibility of preparation of the microspheres was fine in this study.3 In vitro release of koumine-loaded sustained-release porous microspheresWe found that the koumine release from microspheres in 0.5 hours was 23.77%but it was up to 87.01%in 24 hours in vitro,the sustained release effect is well.The release profile of koumine-loaded sustained-release porous microspheres,which fitted with Ritger-Pappas equation,suggested that it may be described as diffusion.4 Preliminary stability study of koumine-loaded sustained-release porous micro-spheresPreliminary stability experiment showed that there was no significant change when the microspheres was at 4500Lx of light,75%relative humidity,room temperature and 4℃for 10 days.On the contrary,the microspheres were aggregated and adhered with a obvious changed release profile at 40℃and 90%relative humidity for 10 days.Besides,the appearance and release profile of microspheres were significantly changed at 30℃and 75%relative humidity for 1 month.The results indicated that the koumine-loaded sustained-release porous microspheres were unstable at high humidity and high temperature,and they should be stored under room temperature（25℃）,sealed and dried conditions.In summary,the preparation parameter of the sustained-release porous microsphere was successfully established,and provide the experimental basis for the pilot production.The microspheres basically conformed to quality requirements and showed a sustained-release pattern in phosphate buffer of pH6.8.Preliminary stability experiment results indicated that the microspheres were unstable at high humidity and high temperature,and they should be stored under room temperature（25℃）,sealed and dried conditions.