US Patent 7541017 Amine polymer-modified nanoparticulate carriers

The invention relates to a composition comprising a colloid which is stable under physiological pH and ionic strength, said colloid comprising particles having a silica core and a shell: a) wherein said shell comprises a cross-linked poly(ethylene)imine polymer having amine functionalities; b) wherein the particles have a volume-weighted mean particle size diameter of less than 200 nm, and c) wherein greater than 50% of said polymer in the colloid is bound to the core surfaces, wherein the polymer having amine functionalities has an average molecular weight less than 100,000 g/mol, the composition has a H of between 6 and 8; and d) wherein the colloid contains between 300 and 6000 .μmol amine-monomer/g core particles.