Synthesis of Ultrasmall Superparamagnetic Iron Oxides Using Reduced Polysaccharides

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Abstract
Investigation into the effect of the reducing sugar of dextran on formation and stability of dextran-coated ultrasmall superparamagnetic iron oxides (USPIO) has demonstrated that reduction of the terminal reducing sugar can have a significant effect on particle size, coating stability, and magnetic properties. Four aspects of polysaccharide-coated USPIO particle synthesis were investigated: (i) the effect reduction of the terminal polysaccharide sugar has upon polysaccharide usage, particle size, stability, and magnetic susceptibility; (ii) the effect an exogenous reducing sugar can have upon particle synthesis; (iii) the effect the molecular weight of the reduced polysaccharide has on particle synthesis; and (iv) the effectiveness of reduced and native dextrans in stabilizing a preformed magnetic sol. For low molecular weight dextrans (MW 20,000 x 10(-6) cgs). Similar results were obtained with a 12 kDa pullulan. The effect of polysaccharide molecular weight on particle size was studied, wherein higher molecular weight reduced dextrans produced larger particles. The effectiveness of the reduced and native dextrans in stabilizing a preformed magnetic sol was compared. Reduced dextrans were found to be superior for stabilizing the magnetic sol. The observed effects of reduction of the terminal sugar in dextran compared with the native dextran were modeled using the Langmuir adsorption isotherm. A good fit of experimental data with this model was found.

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