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Mahany, Nathan Bryce

Chemistry

2009

MS

Clinically approved magnetic resonance imaging contrast agents alter the relaxation rates of water molecules and thereby causing some degree of contrast. The combination of these imaging agents with further diagnostic or treatment functionalities has the potential to revolutionize the field of medicine. Most contrast agents consist of either chelated paramagnetic ions or colloidal superparamagnetic crystals. Although these compounds are limited in their adaptability, incorporation within or on silica or silica coated iron oxide nanoparticles present an ideal scaffold for the optimization of their magnetic relaxational properties. By chelating or incorporating large amounts of paramagnetic or superparamagnetic compounds on or within the silica particle, the rotational correlation time increases and the relaxivity increases.
Either solid or mesoporous silica can be synthesized sufficiently small for biological uses (diameter <150 nm) and a variety of strategies for synthesis and incorporation of the magnetic components have been published. The silica coating also enables the incorporation of secondary functionalities such as fluorescence imaging, targeting, drug delivery and hyperthermia treatment. The effects of polymer coating on biocompatibility and toxicity of the particles are also considered. Herein, the current progress in the area of magnetic silica nanopartic1e optimization and multifunctional design is presented. This is followed by a review of current approaches to polymer assisted particle biocompatibility and cell targeting.