Hyperbranched polymer mediated size-controlled synthesis of gadolinium phosphate nanoparticles: colloidal properties and particle size-dependence on MRI relaxivity

Hyperbranched polymers based on the poly(amidoamine), HyPAM, were used to synthesize gadolinium phosphate nanowires under mild conditions. Control of the average particle size was obtained by adjusting polymer concentration. Proton relaxivity measurements reveal an optimum particle size, reaching relaxivity values as high as 55 +/- 9 mM(-1) s(-1) for r(1) and 67 +/- 11 mM(-1) s(-1) for r(2). The colloidal stability of these hybrid systems were optimized through the use of functionalized core-shell polymers containing PEG segments and C18-PEG segments, structures which also offer the possibility of imparting additional function into the polymer-particle hybrids.