Preparationand Controllable Release Characteristics Of Biodegradable Materials

Experimental method and model analysis were used to study the preparation impactfactors and characteristics of biodegradable materials. The methods of controllable releasedwere also put forward.Solvent evaporation was used to prepare Huperzine A microspheres, and responsesurface analysis was used to judge the preparation methods and preparation conditions.Three factors were analyzed by the Expert-Design software, which were huperzine A:PLGA ratio, PVA concentration, and rotational speed, on the effect of microsphere size.The best conditions were Huperzine A:PLGA ratio=1:15, PVA concentration=1.67%,speed=1200r/min. Under this condition, the average size of microspheres was64.10μm.Infrared spectra showed that Huperzine A has been successfully encapsulated by PLGA.The sizes of microspheres were around150μm-250μm as indicated by SEM analysis. Themicrosphere surface appeared to be microporous.The drug release behavior of the microspheres was studied by measuring thecumulative release rate in the phosphate buffer solution at pH=7.4. It was considered thatthere were three stages in the release process, i.e., the initial burst phase, the stable releasephase, and the post-acceleration release phase. For microspheres made withHuperzineA:PLGA ratio of1:5and1:15, the release trends were basically the same,independent of the PVA concentration and speed. For Huperzine A:PLGA of1:10, therelease trends were significantly different. The speed had certain effect on the release. In asimulated human gastrointestinal tract under conditions of pH changes, microspheresreleased less and slow in acid environment. But when microspheres transited from theacidic to the alkaline environment, a sudden increase in the release was observed, followedby a steady increase.In the reverse thermosensitive gel preparation, the rheology was used to determine theMC+NaCl+PVP substrate. Adding NaCl and PVP into the gel reduced the gelling pointof MC. PVP also effectively improved the gel strength at37℃. Macroeconomic analysis and rheological study showed that adding PVA to the substrate did not affect the geltransition time between36℃-40℃, but it improved the gel strength. The finalMC-NaCl-PVP-PVA system had the composition: MC=0.013g/ml, NaCl=0.097g/ml,PVP=0.013g/ml, PVA=0.010g/ml.The trends of systems of various huperzine A microspheres combined with reversethermosensitive gel sustained-release conditions were the same, using of Huperzine A:PLGA=1:15microspheres. Releasing in PBS for a month, the system release rate was80%with a smooth and continuous drug delivery. Release curve fitted by Higuchi equationand Ritger-Peppas equation illustrated that the drug release was non-Fick diffusion, whichwas drug diffusion and skeleton dissolution synergy. The best fit by zero-order releasekinetics indicates that the system follows non-Fick diffusion and the rate of drug release isnearly constant, and no burst release occurrs. It formed a more long-term drug releasesystem, and more secure and controlled.