Title: Hierarchically structured molecularly imprinted nanomaterials as recognition elements in biochips.
Author: Ana LINARES
National thesis number: 2010COMP1862
- Molecularly imprinted polymers (MIPs) are tailor-made synthetic receptors that are able to specifically recognize a given target molecule. They are synthesized using the target molecule or a derivative thereof as a molecular template around which functional and crosslinking monomers are arranged and co-polymerized to form a cast-like shell. After polymerization and removal of the template, three-dimensional binding sites complementary to the target molecule in size, shape, and position of functional groups are exposed and their conformation is preserved by the crosslinked structure. Thus, a molecular memory is imprinted on the polymer, which is now capable of selectively rebinding the target. MIPs are able to mimic thebiological interactions that take place between antigens and antibodies, an enzyme and its substrate or between a hormone and its receptor. Hence, they are proposed as recognition elements in sensors and biochips as possible substitutes for biomolecules. In order to construct integrated systems containing the recognition element and the transducer part, suitable interfacing and patterning methods are required. The work of this thesis focuses on the deposition and patterning of MIPs onto flat surfaces for their further integration in a sensing device. Three-main techniques have been studied for this purpose: nanomolding, microscope projection photolithography (MPP) and near-field photolithography by evanescent waves (PEW). Nanomolding on sacrificial nanoporous alumina generated films composed of parallel, surfacebound nanofilaments with high aspect ratio, containing surface molecular imprints for either a small molecule, fluorescein, or for the protein myoglobin. These MIPs were able to specifically recognize their targets over other molecules with similar structures. When MPP was used to synthesize these nanostructured MIP films and a pattern was projected onto the surface for polymerization, regular arrays of MIP dots composed of nanofilaments were obtained. These showed an increase in capacity and thus in signal intensity, together with less non-specific binding compared to plain dots generated by the same technique where the MIP precursors were polymerized on a flat surface. Finally, using PEW, molecularly imprinted ultrathin microdots with thicknesses in the range of tens of nanometers were obtained in a controlled manner, exhibiting good recognition properties towards their target, the fluorescent amino acid derivative dansyl-L phenylalanine, as revealed by fluorescence microscopy. We believe that this work paves the road to a better integration of molecularly imprinted polymers into sensing technology.!