Radiolabeled gold nanoparticles may function simultaneously as radiotherapy and thermal ablation systems. The gastrin-releasing peptide receptor (GRP-r) is overexpressed in prostate cancer, and Lys(3) -bombesin is a peptide that binds with high affinity to the GRP-r. HIV Tat(49-57) is a cell-penetrating peptide that reaches the DNA. In cancer cells, (177) Lu shows efficient crossfire effect, whereas (99m) Tc that is internalized in the cancer cell nuclei acts as an effective system of targeted radiotherapy because of the biological Auger effect. The aim of this research was to evaluate the in vitro potential of (99m) Tc-labeled and (177) Lu-labeled gold nanoparticles conjugated to Tat(49-57)-Lys(3) -bombesin peptides ((99m) Tc/(177) Lu-AuNP-Tat-BN) as a plasmonic photothermal therapy and targeted radiotherapy system in PC3 prostate cancer cells. Peptides were conjugated to AuNPs (5 nm) by spontaneous reaction with the thiol group of cysteine (Cys). The effect on PC3 cell viability after laser heating of the AuNP-Tat-BN incubated with the cancer cells was conducted using an Nd:YAG laser pulsed for 5 ns at 532 nm (0.65 W/cm(2) ). For the (99m) Tc/(177) Lu-AuNP-Tat-BN to be obtained, the (177) Lu-DOTA-Gly-Gly-Cys and (99m) Tc-HYNIC-octreotide radiopeptides were first prepared and added simultaneously to a solution of AuNP-Tat-BN. (99m) Tc/(177) Lu-AuNP-Tat-BN (20 Bq/cell) was incubated with PC3 cells, and the effect on the cell proliferation was evaluated after 3 days. Fluorescence images of (99m) Tc/(177) Lu-AuNP-Tat-BN internalized in nuclei of PC3 were also obtained. After laser irradiation, the presence of AuNP-Tat-BN caused a significant increase in the temperature of the medium (46.4 vs 39.5 °C of that without AuNP) resulting in a significant decrease in PC3 cell viability down to 1.3%. After treatment with (99m) Tc/(177) Lu-AuNP-Tat-BN, the PC3 cell proliferation was inhibited. The nanosystem exhibited properties suitable for plasmonic photothermal therapy and targeted radiotherapy in the treatment of prostate cancer.

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.

177 Lu-labeled nanoparticles conjugated to biomolecules have been proposed as a new class of theranostic radiopharmaceuticals. The aim of this research was to synthesize 177 Lu-dendrimer(PAMAM-G4)-folate-bombesin with gold nanoparticles (AuNPs) in the dendritic cavity and to evaluate the radiopharmaceutical potential for targeted radiotherapy and the simultaneous detection of folate receptors (FRs) and gastrin-releasing peptide receptors (GRPRs) overexpressed in breast cancer cells. p-SCN-Benzyl-DOTA was conjugated in aqueous-basic medium to the dendrimer. The carboxylate groups of Lys 1 Lys 3 (DOTA)-bombesin and folic acid were activated with HATU and also conjugated to the dendrimer. The conjugate was mixed with 1% HAuCl 4 followed by the addition of NaBH 4 and purified by ultrafiltration. Elemental analysis (EDS), particle size distribution (DLS), TEM analysis, UV-Vis, and infrared and fluorescence spectroscopies were performed. The conjugate was radiolabeled using 177 LuCl 3 or 68 GaCl 3 and analyzed by radio-HPLC. Studies confirmed the dendrimer functionalization with high radiochemical purity (>95%). Fluorescence results demonstrated that the presence of AuNPs in the dendritic cavity confers useful photophysical properties to the radiopharmaceutical for optical imaging. Preliminary binding studies in T47D breast cancer cells showed a specific cell uptake (41.15 ± 2.72%).177 Ludendrimer(AuNP)-folate-bombesin may be useful as an optical and nuclear imaging agent for breast tumors overexpressing GRPR and FRs, as well as for targeted radiotherapy.

The conjugation of peptides to gold nanoparticles (AuNPs) produces biocompatible and stable multimeric systems with target-specific molecular recognition. Peptides based on the cyclic Arg-Gly-Asp (RGD) sequence have been reported as high-affinity agents for the a(n)b(3) integrin. The aim of this research was to prepare a multimeric system of 177 Lu-labeled gold nanoparticles conjugated to c(RGDfK)C (cyclo(Arg-Gly-Asp-Phe-Lys)Cys) and to compare the radiation-absorbed dose with that of 177 Lu-labeled monomeric and dimeric RGD peptides to a(n)b(3) integrin-positive U87MG tumors in mice. DOTA-GGC (1,4,7,10-tetraazacyclododecane-N-N′,N 00 ,N 000 -tetraacetic acid-Gly-Gly-Cys) and c(RGDfK)C peptides were synthesized and conjugated to AuNPs by a spontaneous reaction of the thiol groups. Transmission electron microscopy, ultraviolet-visible, X-ray photoelectron spectroscopy, Raman and far-infrared spectroscopy techniques demonstrated that AuNPs were functionalized with the peptides. For the 177 Lu-AuNP-c(RGDfK)C to be obtained, the 177 Lu-DOTA-GGC radiopeptide was first prepared and added to a solution of AuNPs followed by c(RGDfK)C (25 ml, 5 mM) at 18 C for 15 min. 177 Lu-DOTA-GGC, 177 Lu-DOTA-cRGDfK and 177 Lu-DOTA-E-c(RGDfK) 2 were prepared by adding 177 LuCl 3 (370 MBq) to 5 ml (1 mg/ml) of the DOTA derivative diluted with 50 ml of 1 M acetate buffer pH 5. The mixture was incubated at 90 C in a block heater for 30 min. Radiochemical purity was determined by ultrafiltration and HPLC analyses. Biokinetic studies were accomplished in athymic mice with U87MG-induced tumors. The radiochemical purity for all 177 Lu-RGD derivatives was 96 AE 2%. 177 Lu-absorbed doses per injected activity delivered to U87MG tumors were 0.357 AE 0.052 Gy/MBq (multimer), 0.252 AE 0.027 Gy/MBq (dimer) and 0.102 AE 0.018 Gy/MBq (monomer). 177 Lu-labeled dimeric and multimeric RGD peptides demonstrated properties suitable for targeted radionuclide therapy of tumors expressing a(n)b(3) integrins.

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