Preparation And Sustained Release Properties Of Polymethyl Methacrylate Drug-loaded Microcapsules

The research and application of microcapsule technology has made great progress.There are so many different kinds of core material,which mainly divided into oil-soluble and water-soluble.Methods of encapsulating water-soluble substances include single coagulation method,complex coagulation method,and double emulsion solvent evaporation method.First of all,in this experiment microcapsules containing water were prepared with poly(methyl methacrylate)(PMMA)as shell by in-situ polymerization directly adding monomer and initiator in inverse emulsion system.We discussed the influence of core-shell mass ratio,volume ratio of oil phase to water,methacrylic acid(MAA)and crosslinking agent allyl methacrylate(AMA)on the properties of microcapsules.These work lay the foundation for the subsequent encapsulating of water soluble substances.After that,taking theophylline as a drug model,the drug loaded microcapsules with sustained and controlled release functionwere prepared,to extend the application of the system in the sustained and controlled release of soluble-drugs.We explored the influence of the amount of crosslinking agent,MAA,the molecular weight and content of polyethylene glycol(PEG)on microcapsule morphology,drug loading and release properties.The drug release process was simulated by mathematical model,and the drug release kinetics were studied.The morphologies,core-shell structure,particle size distribution,encapsulation efficiency,drug loading and release properties of the microcapsules were characterized by scanning electron microscopy(SEM),transmission electron microscope(TEM),laser scattering particle size distribution analyzer(LSPSDA),differential scanning calorimetry(DSC),thermal gravimetric analysis(TG)and ultraviolet-visible spectrophotometer(UV).The conclusions are presented as follows:1.Microcapsules with water as core were successfully prepared,the irregular spherical microcapsules had a core-shell structure,and the distribution of particle size was in 0.5-1.5 ?m,the optimum conditions for the preparation of microcapsules were determined as the oil water phase volume ratio was 10:1,and the mass ratio of the core wall was 1:1.The addition of crosslinking agent and methacrylic acid can improve the encapsulation efficiency significantly.The maximum encapsulation efficiency was 59.4%.2.Drug loaded microcapsules were successfully prepared with theophylline as a model drug.The optimal content of the drug was 10 mg/mL.The morphology,encapsulation efficiency,drug loading and release property of microcapsules were affected by the amount of crosslinking agent,and the morphology was the most regular when the amount of crosslinking agent was 0.1 g.With the increase of the amount of crosslinking agent,the drug loading and encapsulation efficiency were increased and then decreased,the drug loading and encapsulation efficiency was maximum.When the amount of crosslinking agent was 0.3 g,the drug loading was 0.49%,and the encapsulation efficiency was 48.83%.With the increase of the amount of crosslinking agent the release rate of the drug became more slowly,and the cumulative release amount was decreased.Microcapsules had slow release effect and pH response,and the release rate was the fastest under pH5.0 condition.3.The addition of MAA was helpful to increase the drug loading and encapsulation efficiency.The encapsulation efficiency of the three groups was increased by 3.85%,5.96%,2.70%,respectively.The addition of MAA could also accelerate the drug release,but it was limited by the amount of crosslinking agent.The role of MAA in promoting the release decreased with the increase of the amount of crosslinking agent.4.By adding PEG-200,PEG-400,PEG-600,the morphology of the microcapsules was more regular,and drug loading and encapsulation efficiency were increased.However,with the increase of the amount of PEG,the morphology of the microcapsules became irregular,and the drug loading and encapsulation efficiency were decreased.The cumulative release of microcapsules adding PEG-200,PEG-400,PEG-600 was 81.27%,74.97%,68.68%in 240 hours respectively,while the microcapsules without adding PEG was 63.54%.The addition of PEG can accelerate the release of drugs,and the promotion of PEG with small molecular weight was better.With the increase of the amount of PEG,the cumulative release was 70.74%,63.95%,58.43%respectively,and the more amount of PEG added,the more helpful to the drug release.5.Mathematical model fitting results showed that,Ritger-Peppas model was the most suitable.The release kinetics of drug loaded microcapsules was followed Fick diffusion mechanism under pH5.0 condition.