A Multimodal Theranostic System Prepared from High-Density Lipoprotein Carrier of Doxorubicin and ¹⁷⁷Lu

Abstract

Recently, it was demonstrated that doxorubicin (Dox.HCl), a chemotherapeutic agent, could be photoactivated by Cerenkov radiation (CR). The objective of the present work was to develop a multimodal chemotherapy-radiotherapy-photodynamic therapeutic system based on reconstituted high-density lipoprotein (rHDL) loaded with Dox.HCl and 177Lu-DOTA. 177Lu acts as a therapeutic radionuclide and CR source. The system can be visualized by nuclear imaging. Fluorescence microscopy showed that rHDL-Dox specifically recognized cancer cells (T47D) that are positive for SR-B1 receptors. Encapsulated Dox.HCl was released into the cells and produced reactive oxygen species when irradiated with a 450-nm laser (photodynamic effect). The same effect occurred when Dox.HCl was irradiated by 177Lu CR. Through in vitro experiments, it was confirmed that the addition of 177Lu-DOTA to the rHDL-Dox nanosystem did not affect the specific recognition of SR-B1 receptors expressed in cells, or the cellular internalization of 177Lu-DOTA. The toxicity induced by the rHDL-Dox/177Lu nanosystem in cell lines with high (T47D and PC3), poor (H9C2) and almost-zero (human fibroblasts (FB)) expression of SR-B1 was evaluated in vitro and confirmed the synergy of the combined chemotherapy-radiotherapy-photodynamic therapeutic effect; this induced toxicity was proportional to the expression of the SR-B1 receptor on the surface of the cells used. The HDL-Dox/177Lu nanosystem experienced uptake by tumor cells and the liver-both tissues with high expression of SR-B1 receptors-but not by the heart. 177Lu CR offered the possibility of imparting photodynamic therapy where laser light could not reach.

Photoactivation of Chemotherapeutic Agents with Cerenkov Radiation for Chemo-Photodynamic Therapy

“…The ABMA is widely used to estimate the formation of 1 O 2, 6 , 13 while the DCPIP is an electron acceptor used to estimate the presence of O 2 *– . 13 , 18 , 19 …”

“…For the detection of ROS, the reagents 9,10-anthracenediyl-bis­(methylene) dimalonic acid (ABMA) and 2,6-dichlorophenolindophenol (DCPIP) were used. The ABMA is widely used to estimate the formation of 1 O 2, , while the DCPIP is an electron acceptor used to estimate the presence of O 2 *– . ,, …”

“…9,14 Fluorodeoxyglucose labeled with 18 F ( 18 F-FDG) is a radiopharmaceutical (RF) widely used clinically for the diagnosis of tumors by nuclear imaging due to its high accumulation in tumor cells compared to healthy cells. Due to the nuclear characteristics of 18 F (97% β + emission of 635 keV of energy), 18 F-FDG has also been used to produce a photodynamic effect in the presence of different PSs. 8−10,12−14 PS features are crucial in PDT.…”

“…Recent studies show that doxorubicin (DOX) produces ROS when irradiated with a 450 nm laser light and with CR from 18 F-FDG. 13 This evidence suggests that it is possible to use 18 F-FDG as a CR source to produce a photodynamic effect with other chemotherapeutic agents commonly used that present the same characteristics as PS. show some PS characteristics.…”

“…show some PS characteristics. 16,17 Both molecules show high tropism toward tumor cells and have absorption, excitation, and emission spectra 16,17 in the region of the Cerenkov spectrum, so it is possible that they can be excited by CR from of 18 F-FDG and produce ROS. In this way, the cytotoxicity induced by both chemotherapeutic agents could be increased by using the combined effect of CMT+ PDT.…”