Multiwalled carbon nanotube-doxorubicin supramolecular complexes for cancer therapeutics

Multiwalled carbon nanotube aqueous dispersions using block copolymers are able to form supramolecular complexes with the aromatic chromophore and anticancer agent doxorubicin via p–p stacking and enhance its cytotoxic activity. The discovery of novel nanomaterials such as carbon nanotubes (CNTs) capable of traversing the plasma membrane and promoting the cellular uptake of small molecules and macromolecules (e.g. nucleic acids and peptides 2,3) has offered newopportunities for various biological applications. Although most of the existing anticancer drugs are very potent small molecules, their efficacy is constrained not only by their systemic toxicity and narrow therapeutic window but also as a result of drug resistance and limited cellular entry. For this reason the development of efficient delivery systems with the ability to enhance cellular uptake of existing potent drugs is needed. Functionalised CNTs have shown great promise as novel delivery systems especially based on their ability to cross biological barriers independently of the cell type they interact with and the functional group at their surface. In addition, the high aspect ratio of CNTs offers great advantages over existing delivery vectors, as the high surface area provides multiple attachment sites for drug targeting. Pastorin et al. have developed CNT–methotrexate conjugates via covalent linkage for the use of CNTs as multimodal drug delivery systems. Though such conjugates seem promising and are actively explored in our laboratories, the efficiency of drug activity is dependent on the nature of the covalent bond between the CNT and the small molecule. As an alternative strategy, we wanted to explore the hypothesis of any prevalent non-covalent interactions between anticancer drug molecules and CNTs.