Molecular imprinting is an emerging technique for the preparation of synthetic polymers with high selectivity for a predetermined ligand. The most widely used method for preparing molecularly imprinted polymers is by bulk polymerization, followed by grinding to particles. These particles are irregular, polydisperse and usually include a large portion of wasted fine particulate material (estimated 70%). Extensive sieving and sedimentation is required to achieve a more narrow size distribution and to remove fine particles, making the method time and labour consuming. Methods for preparation MIPs in beaded form have been recently reviewed1, 2. They include: suspension polymerization in liquid perfluorocarbon 3 and mineral oil 4, multi-step swelling 5, 6 and grafting polymerization directly to a suitable support 7, 8. The synthesis of MIP in the form of spherical particles has numerous advantages in terms of the process and performance in their final applications.

In this study, uniform spherical molecularly imprinted polymer beads were prepared via controlled suspension polymerization in a spiral-shaped microchannel using mineral oil and perfluorocarbon liquid as continuous phases. Monodisperse droplets containing the monomers, template, initiator, and porogenic solvent were introduced into the microchannel, and particles of uniform size were produced by subsequent U.V. polymerization, quickly and without wasting polymer materials. The droplet/particle size was varied flexibly by changing the flow conditions in the microfluidic device. The diameter of the resulting products typically had a coefficient of variation (CV) below 2%. The specific binding sites that were created during the imprinting process were analysed via radioligand binding analysis. The molecularly imprinted microspheres produced in the liquid perfluorocarbon continuous phase had a higher binding capacity compared to the particles produced in the mineral oil continuous phase. The successful imprinting against a model compound using two very different continuous phases demonstrates the generality of this current simple approach.

Keywords: Molecularly imprinted polymers, microsystem.

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