Dry powder of biocompatible polymeric nanoparticles that will form an aggregate that retains the shape when exposed to a physiological medium or other medium with a higher ionic strength, obtainable by a process that comprises: a) polymerizing an effective amount of: one monomer or two or more monomers selected from the group consisting of: a 2-alkenoic acid, a hydroxy alkyl 2-alkenoate (2C-4C), a dihydroxy alkyl 2-alkenoate (2C-4C), a hydroxy alkoxy-2-alkenoate (2C -4C) (2C-4C) alkyl, a (1C-4C) alkoxy-2-alkenoate (2C-4C) alkoxy (2C-4C) alkyl, or a vicinyl epoxy (1C-4C) alkyl 2-alkenoate, in a polar liquid or a mixture of two or more miscible liquids, at least one of which is polar, and an effective amount of a surfactant to produce a suspension of a plurality of polymeric nanoparticles in which the polymeric nanoparticles have an average diameter less than 1 x 10-6 m ± 15%； and b) removing the liquid (s) from the suspension by a procedure comprising spray drying or lyophilization to prevent aggregation and so that the amount of liquid (s) remaining in the dry powder is less than 10% ± 15% by weight where the percentage is based on the total weight of the dry powder.Polvo seco de nanopartículas poliméricas biocompatibles que formará un agregado que retiene la forma al exponerlo a un medio fisiológico u otro medio de fuerza iónica superior, obtenible mediante un procedimiento que comprende: a) polimerizar una cantidad eficaz de: un monómero o dos o más monómeros seleccionados de entre el grupo que consiste en: un ácido 2- alquenoico, un 2-alquenoato de hidroxi alquilo (2C-4C), un 2-alquenoato de dihidroxi alquilo (2C-4C), un 2-alquenoato de hidroxi alcoxi (2C-4C) alquilo (2C-4C), un 2-alquenoato de alcoxi (1C-4C) alcoxi (2C-4C) alquilo (2C-4C), o un 2-alquenoato de vicinil epoxi alquilo (1C-4C), en un líquido polar o una mezcla de dos o más líquidos miscibles, por lo menos uno de los cuales es polar, y una cantidad eficaz de un tensioactivo para producir una suspensi
