The use of nanoparticles for therapy or diagnostic imaging in living systems must address delivery and binding to the target site as well as clearance from the individual. The research team will focus its efforts on nanometer-scale superparamagnetic iron oxide particles surrounded by non-polymeric biocompatible organic shells consisting of small molecules, tethered to the particle surfaces, which will provide greater mobility and diffusion for the imaging agent compared with particles surrounded by polymeric shells. Kolesnichenko and Zhang will synthesize nanoparticles of magnetite, maghemite and other spinel-structured ferrites with dimensions of 2 - 4 nm, attach various hydroxycarboxylic acids (via the carboxylic acid group) to the nanoparticles and study their stability. The size range of these nanoparticles is particularly interesting because it permits rapid clearance and therefore minimizes toxic effects. Canary and Kirshenbaum will design various peptides and peptidomimetic oligomers for direct attachment to the nanoparticles or to the hydroxy groups of previously immobilized hydroxycarboxylic acids, with the aim regulating solubility, target site localization, and self-assembly.