Title: Molecularly imprinted polymer nanostructures by controlled living radical polymerization with multi-iniferters.
Author: Pinar CAKIR
National thesis number: 2012COMP2018
- Molecularly imprinted polymers (MIPs) are synthetic materials with specific recognition properties for target molecules. They are considered an alternative to antibodies and are characterized by a higher chemical and physical stability, better availability and lower cost. Historically, MIPs were synthesized as bulk monoliths that were subsequently broken down mechanically in order to form particles of a size in the micrometer range, with irregular shapes. During the last decade, research has focused on the direct synthesis of spherical MIP micro and nanoparticles, and, more recently, on protein-sized, quasi-soluble MIP nanogels in order to widen the application range of MIPs in the biological field. The main difficulty of synthesizing MIPs with diameters in the low nm region is the low density of the resulting polymer network consisting only of a few polymer chains, which makes it difficult to imprint and maintain a molecular memory. In this thesis, we propose an original approach to the synthesis of quasisoluble MIP nanogels with a size in the low nm range, close to that of real antibodies. The proposed procedure involves a new type of initiator for controlled/living radical polymerization, based on multiple iniferter moieties attached to a dendritic core. This allows for the generation of a higher local radical density, and thus for the synthesis of denser nanogels. By using this strategy, MIP Nanogels of 17 nm size with an appreciable molecular imprinting effect, a good affinity for the target molecule, the chiral drug propranolol, and a good selectivity were obtained. In addition, these multiiniferters were also used for the bottom-up synthesis of thin MIP patterns on silicon wafers, by surface-initiated polymerization. The multi-iniferter was printed on to the surface by soft lithography and chemically attached through its carboxyl-functionalized core, followed by the in-situ synthesis of the MIP. Well defined MIP patterns were obtained, which were characterized by optical emission spectroscopy, Raman spectroscopy, atomic force microscopy, and the specific binding of the target molecule was visualized by fluorescence microscopy. We believe that the synthesis, in solution and at surfaces, of protein-size MIP nanogels with specific recognition properties will provide new opportunities for biosensors and biochips technologies in biomedical applications.