Preparation and Characterization of Metronidazole-Surface Imprinted Microspheres MIP-PSSS/CPVA for Colon-Specific Drug Delivery System

In this paper, the use of molecular surface imprinted polymers (MIPs) in designing colon-specific drug delivery systems was investigated. MIPs were prepared on crosslinked polyvinyl alcohol microspheres (CPVA) with sodium 4-styrene sulfonate (SSS) as functional monomer, Metronidazole (MTZ) as template and N,N'-Methylene bisacrylamide (MBA) as crosslinking agent by utilizing cerium salt-hydroxyl group redox initiation system, obtaining MTZ molecular surface imprinted microspheres MIP-PSSS/CPVA. The MIP-PSSS/CPVA microspheres were further characterized by scanning electron microscope and batch binding method. Because there is strong electrostatic interactions between MTZ and monomer SSS, the MTZ molecular surface imprinting is quite successful, and the imprinted microspheres MIP-PSSS/CPVA possess high recognition selectivity and excellent combining affinity. The experimental results show that at pH 1, the MIP-PSSS/CPVA microspheres exhibit very strong binding ability for MTZ, and the binding capacity reaches up to 115mg/g. The in vitro release of the MTZ-loaded MIP-PSSS/CPVA is highly pH-dependent and time-delayed. The release behavior shows that the drugs do not release in simulated gastric fluid (pH = 1), the drug release is small while in the simulated small intestinal fluid (pH = 6.8), an abrupt release will be firstly produced and then drug release is sustained and slowed in the simulated colon fluid (pH = 7.4), displaying excellent colon-specific drug delivery behavior.