825 Chemistry: Bulgarian Journal of Science Education Volume 24 Number 6, 2015 Природните науки в образованието 90th Anniversary of the Department of Physical Chemistry of the University of Sofia Юбилей: 90 години на Катедрата по физикохимия на Софийския университет COMPLEX SYSTEMS FOR DRUG TRANSPORT ACROSS CELL MEMBRANES Nikoleta Ivanova, Yana Tsoneva, Nina Ilkova, Anela Ivanova University of Sofia Abstract. Targeted drug delivery to specific tissues or cell compartments in the human organism is an advantageous route to overcoming multidrug resistance or reducing undesired side effects of pharmaceutics. Efficient specific targeting requires associating the drug with a carrier molecule. A multitude of compounds and assemblies have been tested as transporting moieties. This review summarizes the various classes of nanocarrier constructs, which have been proposed for transferring a class of potent chemotherapeutic agents, namely, anthracycline antibiotics through cell membranes. The building principles of the delivery systems are outlined and their pros and cons are discussed. Wherever available, the results from molecular simulations are presented. Special attention is paid to peptide-based systems in general and to a special type of peptides in particular – the cell-penetrating peptides, which may be used as building blocks of new systems for targeted drug delivery. Keywords: drug delivery systems, anthracycline antibiotics, doxorubicin, cell- penetrating peptides, nanoparticles, biodegradable polymers