Coupling of optical characterization with particle and network synthesis for biomedical applications

Polymeric microspheres containing a magnetic core have been used in cancer therapy for biophysical targeting of antitumor agents and in magnetic resonance imaging as contrasting agents. For the Human Genome Project, deoxyribose nucleic acid (DNA) capillary electrophoresis has become the most widely used analytical technique where a key component is the design of an effective separation medium. The synthesis and optical characterization of polymeric coated superparamagnetic nanoparticles and of (self-assembled) polymer networks by means of a range of physical techniques, including laser light scattering and laser-induced fluorescence detection, are presented. (1) Polymeric microspheres with a superparamagnetic core. A water-in-oil microemulsion approach has been used successfully to synthesize the superparamagnetic core and the polymeric microsphere in one continuous step. The synthesis permits us to control the magnetic nanoparticle size and the thickness of the hydrogel, ranging from 80 to 320 nm. Magnetite concentration in the microspheres, calculated by vibrating-sample magnetometry, was found to be up to 3.3 wt %. The internal structure of the microspheres, as observed by atomic force microscopy, confirmed a core-shell model. (2) Development of new separation media for DNA capillary electrophoresis. Block copolymers in selective solvents can self-assemble to form supramolecular structures in solution. The nanostructures can be characterized in the dilute concentration regime by means of laser light scattering. At semidilute concentrations, the mesh size, the supramolecular structure, and the surface morphology can be investigated by means of small angle x-ray scattering and atomic force microscopy. The structural knowledge and the information on chain dynamics can then be correlated with electrophoresis using laser-induced fluorescence detection to provide a deeper understanding for the development of new separation media.