Preparation of ultrafine silica- and PEG-coated magnetite particles

The effect of the molecular weight, reaction temperature and polymer concentration were investigated. The PEG coverage could be controlled by the selection of the polymer; the molecular coverage increased with decrease in polymer molecular weight. A method for synthesising PEG-coated magnetite particles for use in diagnostic imaging is described. Magnetite particles in aqueous conditions were reacted with Si(OR)2R′R′′ (trimethoxysilane-PEG, R=Me; R′=Ome; R′′=PEG). These PEG-coated magnetite particles showed greatly enhanced colloid stability properties with respect to the uncoated particles.