  During the past years we have investigated the complexation between
nanocolloids and oppositely charged polymers. The nanocolloids examined were
ionic surfactant micelles and inorganic oxide nanoparticles. For the polymers,
we used homopolyelectrolytes and block copolymers with linear and comb
architectures. In general, the attractive interactions between oppositely
charged species are strong and as such, the simple mixing of solutions
containing dispersed constituents yield to a precipitation, or to a phase
separation. We have developed means to control the electrostatically-driven
attractions and to preserve the stability of the mixed solution. With these
approaches, we designed novel core-shell nanostructures, e.g. as those obtained
with polymers and iron oxide superparamagnetic nanoparticles. In this
presentation, we show that electrostatic complexation can be used to tailor new
functionalized nanoparticles and we provide examples related to biomedical
applications in the domain of contrast agents for Magnetic Resonance Imaging.
