The design of multifunctional nanocarriers with specific targeting functions for efficient internalization and intracellular transport is still a challenge for contemporary science, aimed at achieving optimal targeting and drug delivery at subcellular level. The project is interdisciplinary and covers various areas of polymer science, biochemistry and biophysics. Its implementation relies on the joint efforts of scientific team from leading centers in the corresponding fields, i.e. Institute of Polymers, Bulgarian Academy of Sciences and the Faculty of Pharmacy, Medical University – Sofia, with complementary knowledge and expertise. The project focuses on synthesis of a series of amphiphilic diblock and triblock copolymers bearing specific functionalities (different types of targeting ligands, cleavable groups, and hydrophobic, nonionic and polycationic moieties). By self-assembly and co-assembly of the copolymers, multifunctional nanosized drug carriers with different structures are being prepared. The drug loaded nanocarriers are designed to overcome various cellular barriers and reach target cell organelle (e.g. mitochondria), where they are expected to release their cargo. The nanocarriers are composed of three main elements with specific functions: (i) a hydrophobic core loaded with active compounds; (ii) a polycationic layer decorated with subcellular targeting ligands and (iii) an outer shell of acid-cleavable hydrophilic polymer chains modified with degradable and cell targeting groups. Detailed investigation of physicochemical and biopharmaceutical properties of the multifunctional nanocarriers and their two-step subcellular targeting, will contribute to the accumulation of knowledge aiming at the development of an efficient anticancer platform for medical application.