Use of purified surface modifiers to prevent particle aggregation during sterilization

A composition comprising nanoparticles having a purified polymeric surfactant as a surface modifier adsorbed on the surface thereof and a cloud point modifier associated therewith, which cloud point modifier is present in an amount sufficient to increase the cloud point of the surface modifier, and a method of making such nanoparticles is described. Preferred purified polymeric surfactants are purified polyalkyleneoxide substituted ethylenediamine surfactants and a preferred cloud point modifier is polyethylene glycol.