Near-infrared light-sensitive micelles for enhanced intracellular drug delivery

Near-infrared light-sensitive polymeric micelles were prepared for the enhanced intracellular delivery of doxorubicin (DOX). The micelles were prepared from dextran-graft-(2-diazo-1,2-naphthoquinone) (Dex-DNQ) amphiphilic copolymers which were synthesized by modification of hydrophilic dextran with hydrophobic DNQ molecules. The hydrophobic DNQ molecule is an attractive photo-trigger group because its UV/NIR-induced Wolff rearrangement can result in a drastic change into a hydrophilic 3-indenecarboxylic acid (3-IC) molecule with pKa of 4.5. Thus, under UV or NIR irradiation, Dex-DNQ micelles will rapidly release encapsulated drugs due to the micelle dissociation. DOX was chosen as an anticancer drug to be encapsulated into the Dex-DNQ micelle with the loading efficiency and content of 60% and 24%, respectively. In vitro cell viability studies, the micelles exhibited higher intracellular DOX release under NIR irradiation at 808 nm, which resulted in significant growth inhibition of HepG2 cancer cells. Fluorescence microscopy and flow cytometry further proved the enhanced intracellular drug release behaviour of DOX-loaded Dex-DNQ micelles under NIR irradiation. We are convinced that this smart drug nanocarrier is potentially useful for cancer chemotherapy.