Molecularly imprinted nanoparticles for bio-sensing applications. (R-4344)

The development of biosensors for the detection of biologically relevant molecules in effect-relevant concentrations in a fast, cost effective and reliable way is highly demanded in the field of medical diagnostics as well as in food- and environmental safety. Biosensors based on the molecular recognition principle have been successfully employed for various types of target molecules and typical recognition processes are e.g. the antibody-antigen- and enzyme-substrate interactions. Typically, the receptor molecules are immobilized on a suitable platform material and the recognition of the target molecules is translated to a concentration-dependent signal via electronic or optical read-out techniques. A limitation to the concept is imposed by the fact that there are target molecules for which natural receptors either do not exist or exhibit insufficient specificity and physical or chemical stability. Hence, a compelling alternative is to develop so-called 'synthetic' or 'biomimetic' receptors. An especially promising approach towards these receptors is based on molecularly imprinted polymers (MIPs). MIPs have nanocavities that are complementary in size, shape and arrangement of functional groups to the target molecule which makes these cavities capable of rebinding the target molecule with a high specificity (figure (1)). Molecular imprinting using bulk- and suspension polymerization is already well established including also at the host institute. In contrast, the use of molecularly imprinted polymer nanoparticles is expected to offer specific advantages over bulk- and suspension polymerized MIPs. Bulk-polymerized MIPs need to be mechanically crushed and sieved, resulting in irregular, micron-sized particles. Suspension polymerization provides monodisperse, sphere-shaped particles, but still at the micron size. Nanoparticle MIPs, however, should not only have the regular (spherical) shape but also a tremendously enhanced interfacial area and short diffusion paths to extract or to rebind target molecules. Also, for MIPs, usually monomers are used (~ 10 - 20 %) containing a functional group that can interact with the template molecules in combination with a crosslinking monomer (~ 80 - 90 %), being often structurally similar to the functional monomers. Although the concept of MIP synthesis seems fairly straight forward, optimization of MIP formulation components is challenging. One has to choose the appropriate functional monomer with respect to the template/target molecule together with an appropriate crosslinker and the quality of the final MIP depends also on the concentration ratios of the individual components. Alternatively, a high performance MIP was realized using bulk polymerized MIPs made with a single crosslinking monomer: N,O-bisMethacryloyl ethanolamine (NOBE). With that concept, a simplified route to design MIPs was developed where the need for additional functional monomers and empirical optimization of the relative ratios of functional monomers, crosslinkers, and template in the formulation was eliminated. Apart from the bulk-polymerized NOBE MIPs, also micron sized particles obtained by precipitation polymerization have been reported. However, imprinted nanoparticles (< 250 nm) made of single crosslinking monomers have not been documented yet and represent the central goal within this project proposal. The most versatile method to achieve the goal of imprinted nanoparticles is the miniemulsion technique. This route is suitable for the preparation of MIPs based on methacrylate monomers and crosslinkers, but single crosslinking monomers have not yet been utilized in this context.

Keywords:nanoparticles and -clusters

Disciplines:Ceramic and glass materials, Materials science and engineering, Semiconductor materials