Controlled Release of Doxorubicin from the Drug Delivery Formulation Composed of Single-Walled Carbon Nanotubes and Congo Red: A Molecular Dynamics Study and Dynamic Light Scattering Analysis.

The controlled delivery and release of drug molecules at specific targets increases the therapeutic efficacy of treatment. This paper presents a triple complex which is a new potential drug delivery system. Triple complex contains single-walled carbon nanotubes, Congo red, and doxorubicin. Nanotubes are built of a folded graphene layer providing a large surface for binding Congo red via "face-to-face" stacking which markedly increases the binding capacity of the carrier. Congo red is a compound that self-associates to form supramolecular ribbon-like structures, which are able to bind some drugs by intercalation. The nanotube-Congo red complex can bind the model drug doxorubicin. Thus, a new triple carrier system was obtained. The aim of this paper is to present studies on the controlled release of a model anticancer drug from a triple carrier system through pH changes. The specific aim of the study was to model the structure of the obtained experimental systems and to compare the changes in the average energy of interaction between its components induced by pH changes. The studies also aimed to compare the intensity of pH-dependent changes in hydrodynamic diameters of individual components of the triple carrier system. The effect of pH changes on the stability of the analyzed systems was examined using the molecular modeling method and dynamic light scattering. The decrease in pH influenced the structure and stability of the analyzed triple systems and ensured efficient drug release. The changes in hydrodynamic diameters of the obtained fractions were examined with the use of dynamic light scattering and were confirmed by computer simulation methods. The formulation presented in this paper shows potential for a therapeutic application owing to its high drug binding capacity and pH-dependent release. This ensures prolonged local action of the drug. The results reveal that the studied complex fulfills the basic requirements for its potential use as drug carrier, thus reducing side effects and enhancing pharmacological efficacy of drugs.