(364f) Star Shaped Molecularly Imprinted Polymer Working as a Drug Carrier

Liquid membrane is a separating process using extraction between immiscible liquids with recognitive carrier. In the forward extraction, the target molecule in one aqueous phase binds with carrier in the organic phase. In the backward extraction, the carrier release the target into the another aqueous phase. This process enables highly selective separation. Continuous process is also applicable. However synthesis of selective and organic-soluble carrier is very difficult. Therefore we designed novel liquid membrane process using star shaped molecularly imprinted polymer (MIP) as a carrier.

Star polymer is colloidal particle which has “arm” domain for high affinity with solvent and crosslinked “core'' domain. We designed a star polymer whose core is imprinted by template. In this work, the star shaped MIP of L-phenylalanine (L-PA) was synthesized using living radical polymerization. The ability of the polymer as a carrier was estimated by bulk liquid membrane method.

Living radical polymerization of methyl methacrylate (MMA) was allowed to occur by using initiator of benzyl diethyldithiocarbamate under ultraviolet (UV) irradiation. The arm polymer was obtained after reprecipitation in large amount of dimethyl ether. The star shaped MIP was synthesized through photo-copolymerization of acrylamide, N,N'-methylenebisacrylamide, and methacrylic acid with PA as a template by the living polyMMA as a initiator in emulsified solvent of chloroform and water　(Fig.1). The Star MIP was repricipitated in methanol. The prepared polymer is referred to as Star MIP. The diameter of the Star MIP was determined approximately 200 nm by light scattering spectroscopy. Star Non MIP was also synthesized by the same procedure in the absence of template. The synthesized polymers were prepared as a stable colloid in chloroform.

The transport ability for PA of the Star MIP and Star Non MIP was estimated by bulk liquid membranes using U-shaped glass tube (Fig.2). Three phases for the aqueous source of the L-PA, chloroformic liquid membrane with the star polymer, and the aqueous receiver of L-PA were formed in the tube. Time courses of L-PA concentration in the source phase and the receiving phase were observed.

As the result, the L-PA concentrations in the receiving phase increased dramatically in the experiment with the Star MIP during 120hr operation of the liquid membrane experiment (Fig.3). Contrastively, L-PA was not detected at all in the receiving phase of the experiment with Star Non MIP or none.

Those results strongly suggest that the star-shaped molecularly imprinted polymer can work as a carrier of the liquid membrane process. However the slow transport may indicate that this Star MIP is suitable for in vivo drug carrier rather than industrial separation process.