Doxorubicin Encapsulation in D-α-Tocopherol Succinate-Functionalized β-Cyclodextrin Enhances Intracellular Retention and Cytotoxicity in a Chemoresistant T-ALL Model

Abstract

Therapeutic resistance remains a major limitation in T-cell acute lymphoblastic leukemia (T-ALL) and can reduce the efficacy of chemotherapeutic agents, including doxorubicin (DOXO). Since intracellular drug accumulation and retention are important determinants of DOXO activity, we evaluated whether its encapsulation in a β-cyclodextrin (β-CD)-based carrier could improve its intracellular behavior in resistant leukemia cells. β-CD was functionalized with D-α-tocopherol succinate (TOCO), characterized by FTIR and 1H NMR, and subsequently used for DOXO encapsulation. The selected β-CD-TOCO formulation exhibited a hydrodynamic diameter of approximately 100 nm, a PDI below 0.4, and a ζ-potential near −20 mV. DOXO encapsulation efficiency increased from 8.76 ± 0.41% in non-functionalized β-CD to 11.54 ± 0.51% after TOCO functionalization, while loading capacity increased from 1.06 ± 0.04% to 1.15 ± 0.05%. The biological effects of the formulation were examined in Jurkat cells as a chemoresistant T-ALL model. Encapsulation did not prevent DOXO incorporation into the cells but increased its intracellular retention and modified its subcellular distribution. In particular, encapsulated DOXO showed greater nuclear accumulation, with a nucleus-to-cytosol fluorescence ratio of 2.58 compared with 1.02 for free DOXO. The increased intracellular persistence of DOXO was accompanied by reduced metabolic activity, increased Annexin V labeling, and greater cytotoxicity than that produced by the free drug. These results show that β-CD-mediated encapsulation can modify the intracellular disposition of DOXO and increase its activity in chemoresistant T-ALL cells. The β-CD-TOCO system therefore provides a basis for further evaluation of DOXO delivery in additional models of resistant lymphoid leukemia.