Molecularly Imprinted Hydrogel Microspheres In Response To Sustained Drug Delivery

In recent years, polymeric hydrogels have attracted increasing attention, because of the excellent hydrophilic properties and favorable biocompatibility. Oral sustained and controlled release preparations have developed rapidly, because of their convenient application and better compliance. Swollen hydrogels in semi-solid state, can delay the drug release. In this study, hydroxypropyl methylcellulose (HPMC),as raw material, was used in the preparation of hydrogel microspheres, and the microspheres were applied to the sustained and controlled release of theophylline.Firstly, the HPMC hydrogel microspheres were prepared via inverse phase suspension polymerization, using divinylsulfone (DVS) as crosslinker, and cyclohexane as solvent. The effects of concentration of HPMC, agitation speed, the amounts of catalyst and suspension agent on the stability of the suspension system and the size of hydrogel microspheres were studied. Then the effect of porosity on swelling degree, swelling behavior were also studied and the condition of water in hydrogels was characterized by DSC.Secondly, the hydrogel microspheres prepared was applied to drug release. The drug loading and release behavior of theophylline in hydrogel microspheres was studied. The results show that the hydrogel microspheres have a drug loading up to 9%, and can sustain the theophylline release for more than 15 hours.Finally, the molecularly imprinted polymeric microspheres (MIPMs) were prepared by using theophylline as printing molecule. The drug loading and the release behavior of theophylline in MIPMs were studied. Then the effect of the amount of printing molecule and crosslinker on the release behavior were also studied. The results show that the molecular imprinting technique can increase the hydrogel microsphere drug loading and release time. The MIPMs'drug loading is up to 18%, which is twice as that of non-imprinted hydrogels. In addition, by adjusting the amount of template and crosslinker, MIPMs can successfully achieve sustained release. Among them, the samples (theophylline / HPMC, 6%; DVS / HPMC, 20%) achieve zero-order release of theophylline in 22 hours, meeting the requirements of controlled release.