The present invention relates to a nano-sized drug delivery structure for delayed and controlled diffusion of at least one drug active, in particular into an aqueous medium, said drug delivery structure comprising at least one support material; one multilayered structure overlaying and/or surrounding at least partially said support material and comprising at least two layers of oppositely charged materials; and one drug active agent immobilized on one or more material(s) of one or more inner layer(s) of the said multilayered structure. The invention also relates to a process for preparing the nano-sized drug delivery structure, to the use of said structure in a pharmaceutical composition and to such a pharmaceutical composition