Synthesis and Characterization of Molecularly Imprinted Polymeric Microspheres for L-Methyldopa and Its Application to Drug Delivery System

The molecularly imprinted polymeric microspheres (MIPMs) for L-methyldopa (LMD) were synthesized by precipitation polymerization. The influences of synthetic conditions such as polymerization temperature, the amount of initiator (AIBN) and the property of template on the morphologies and diameter sizes of MIPMs were investigated in details. The results indicated that the morphologies of MIPMs were evidently affected by the polymerization temperature and the amount of AIBN. The diameters of MIPMs were decreased with increasing the polymerization temperature but increased with increasing the amount of AIBN, while the influences of template on the diameters of microspheres are not visible. The resultant MIPMs was characterized by scanning electronic microscopy (SEM), IR analysis, BET adsorption test and Scatchard analysis as well as the controlled release test in mimetic gastric juice (pH = 1). The IR analyses proved that the polymerization effects really occurred. The BET adsorption test indicated that the adsorption amount of MIPMs to LMD was as three times as that of non-imprinted microspheres (NIPMs). The controlled release test indicated that the release ratio of LMD on NIPMs was linearly increased with increasing time, which suggests that the release process is completely controlled by diffusion. Meanwhile, the release ratio of LMD on MIPMs was curvedly increased with increasing time, which indicates that the release process is controlled by both diffusion and the imprinting effect. And the release time was prolonged. The results indicate that the MIPMs released the LMD for 10 h while the NIPMs for only 5 h in the mimetic gastric juice. Therefore, the resultant MIPMs of LMD looks forward to being used as the materials for DDS.