the invention relates to nanoparticles of polyoxyethylenated derivatives , having a size of less than 1 micrometer , for the administration of pharmaceutically - or cosmetically - active ingredients . the inventive nanoparticles comprise a biodegradable polymer , a polyoxyethylene - derived block copolymer and at least one pharmaceutically - or cosmetically - active ingredient . the invention further relates to the method of obtaining the aforementioned nanoparticles and to compositions containing same .