Nanoscale Reaction Systems

The work presented in this thesis describes the use of polystyrene nanoparticles as model surfaces for bioanalytical work. Nanoparticles constitute convenient platforms for the attachment of bioactive agents, and receptor coated particles offer high local concentration of binding sites for specific ligands with minimal steric hindrance. However, it is not only the amount of bound protein that matters, the proteins must also be immobilized at the surface in such ways that they fully retain their activity, while at the same time protecting the surface from unspecific uptake of undesired components. The present work relates to the controlled immobilization of multiple types of active biomolecules onto nanoparticle surfaces to make them multifunctional. The surface expansion offered by the nanoparticles, in combination with the closeness between the reactants co-immobilized on the same particle, enables coupled reactions to be carried at a higher rate than otherwise possible. Thus, particle-decorated surfaces of this kind are highly suitable for miniaturized bioanalytical systems. Sensitive microarray systems are under development, including lectin-coated nanoparticles for glycoprotein mapping and a diagnostic device for Point-of-Care testing with a nanoparticle-based detection system. The full evaluation of protein attachment to nanoparticles requires precise analytical techniques for particle characterization, both in bare and coated form. The mass-sensitive SdFFF technique occupies a prominent position for particle characterization, as it offers both accurate determination of particle size and a quantification of adsorbed layers on small particles, whether of synthetic or biopolymeric nature. Here, this analytical technique is developed to precisely characterize nanoparticles that are sequentially coated with different layers, each rendering the particles a specific functionality. The thesis demonstrates how precise mass uptakes can be determined for each specific layer, and how control over the exact surface composition of the modified particles can be established for optimization of biological activity