The present invention provides a system presenting site-specific accumulation through a ligand that specifically targets a receptor overexpressed on the surface of specific cells within a target organ, like, for example, tumor cells and/or vascular cells of tumor blood vessels. Moreover, this invention provides a method where, upon internalization of the previous-mentioned system by the target cells, triggered release at a high rate of the associated agent takes place, permitting efficient intracellular delivery and, thus, increased concentration of the transported cargo at the target site. Overall, this invention provides a method for the diagnosis, prevention and treatment of human diseases and disorders.