Summary

Um protocolo otimizado para a radiomarcação eficiente de nanopartículas de ouro usando um<sup> 125</sup> Marcado com Eu Azida grupo prostético

Published: October 10, 2016
doi:

Summary

Um procedimento pormenorizado para a síntese de uma azida marcado com 125I e a radiomarcação de dibenzocyclooctyne (DBCO) -Grupo-conjugados, nanopartículas de ouro de 13 nm de tamanho, utilizando uma reacção de clique sem cobre é descrito.

Abstract

Here, we demonstrate a detailed protocol for the radiosynthesis of a 125I-labeled azide prosthetic group and its application to the efficient radiolabeling of DBCO-group-functionalized gold nanoparticles using a copper-free click reaction. Radioiodination of the stannylated precursor (2) was carried out by using [125I]NaI and chloramine T as an oxidant at room temperature for 15 min. After HPLC purification of the crude product, the purified 125I-labeled azide (1) was obtained with high radiochemical yield (75 ± 10%, n = 8) and excellent radiochemical purity (>99%). For the synthesis of radiolabeled 13-nm-sized gold nanoparticles, the DBCO-functionalized gold nanoparticles (3) were prepared by using a thiolated polyethylene glycol polymer. A copper-free click reaction between 1 and 3 gave the 125I-labeled gold nanoparticles (4) with more than 95% of radiochemical yield as determined by radio-thin-layer chromatography (radio-TLC). These results clearly indicate that the present radiolabeling method using a strain-promoted copper-free click reaction will be useful for the efficient and convenient radiolabeling of DBCO-group-containing nanomaterials.

Introduction

The strain-promoted copper-free click reaction between azides and cyclooctynes has been extensively applied to the efficient bioorthogonal labeling of a wide range of biomolecules, nanomaterials, and living subjects1-7. Due to the excellent site-specificity and rapid reaction rate of this conjugation reaction, it has also been used to synthesize radiolabeled tracers. A few 18F-labeled azide or DBCO prosthetic groups have been prepared for in vitro labeling of various cancers targeting peptides and antibodies, as well as for in vivo pre-targeted imaging of tumors8-13. In addition to these examples, the same conjugation reaction was applied to the metal-radioisotope-labeling of nanomaterials for positron emission tomography (PET) imaging studies14-16.

For several decades, radioactive iodines have been used for biomedical research and clinical trials through PET imaging (124I), single-photon emission computed tomography (SPECT) imaging (123I, 125I), and thyroid cancer treatment (131I)17-21. Therefore, an efficient method for radioactive iodine labeling is fundamentally important for various investigations, including molecular imaging studies, analysis of organ distribution of biomolecules, biomarker identification, and drug development. A copper-free click reaction strategy could be used in radioactive iodine labeling. However, this application has not been investigated as extensively as 18F-labeled biomolecules22-23. Here, we will provide a step-by-step protocol for the synthesis of an 125I-labeled azide for radiolabeling of DBCO-group-derived molecules. The procedures in the present report will include radioiodination of the stannylated precursor, purification steps with HPLC, and solid phase extraction. We also demonstrate efficient radiolabeling of DBCO-group-modified 13-nm-sized gold nanoparticles using the 125I-labeled azide. The detailed protocol in this report will help synthetic chemists understand a new radiolabeling methodology for the synthesis of radiolabeled products.

Protocol

Cuidado: A forma oxidada de iodo radioativo é bastante volátil e devem ser manuseados com escudos de chumbo adequados e frascos de chumbo. Todos os passos radioquímica deve ser levada a cabo em uma capa filtrou-carvão bem ventilado, e os procedimentos experimentais devem ser monitorizadas por meio de dispositivos de detecção de radioactividade. 1. Preparação dos produtos químicos e o cartucho de fase reversa para a síntese da azida 125 I-rotulados Preparação de reagentes…

Representative Results

A reacção de radioiodação do precursor estanilado (2) foi realizado utilizando 150 MBq de [125I] NaI, ácido acético, e cloramina T à temperatura ambiente durante 15 min para proporcionar o produto marcado radioactivamente (1). Depois de purificação por HPLC preparativa da mistura em bruto, o produto desejado foi obtido com 75 ± 10% (n = 8) de rendimento radioquímico. HPLC analica revelou que a pureza radioquímica do produto marcado…

Discussion

Em geral, o rendimento radioquímico observada da azida 125 purificada marcada com I (1) foi de 75 ± 10% (n = 8). A marcação radioactiva foi feita com 50-150 MBq de radioactividade, e os resultados são bastante consistente radioquímica. Se [125I] NaI (T 1/2 = 59,4 d) que foram submetidos a decaimento radioactivo durante mais de um mês foi utilizado na reacção de radioiodação, observou-se o rendimento radioquímico de 1 a ser ligeiramen…

Divulgazioni

The authors have nothing to disclose.

Acknowledgements

This work was supported by grants from the National Research Foundation of Korea, funded by the government of the Republic of Korea, (Grant nos. 2012M2B2B1055245 and 2012M2A2A6011335) and by the RI-Biomics Center of Korea Atomic Energy Research Institute.

Materials

Chloramine T trihydrate Sigma 402869
[125I]NaI in aq. NaOH Perkin-Elmer NEZ033A010MC
Sodium metabisulfite  Sigma S9000
Formic acid Sigma 251364
Sep-Pak tC18 plus cartridge Waters WAT036800
Dimethyl sulfoxide  Sigma D2650
Acetone Sigma 650501
Ethanol Sigma 459844
Gold(III) chloride trihydrate Sigma 520918
Tween 20  Sigma P1379
DBCO PEG SH (MW 5000) NANOCS PG2-DBTH-5k
TLC silica gel 60 F254 Merck
Analytical HPLC Agilent 1290 Infinity Model number
Preparative HPLC Agilent 1260 Infinity Model number
Analytical C18 reverse-phase column Agilent Zorbax Eclipse XDB-C18
Preparative C18 reverse-phase column Agilent PrepHT XDB-C18
Radio TLC scanner Bioscan AR-2000 Model number
Radioisotope dose calibrator Capintec, Inc CRC -25R dose calibrator Model number

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Citazione di questo articolo
Jeon, J., Shim, H. E., Mushtaq, S., Choi, M. H., Park, S. H., Choi, D. S., Jang, B. An Optimized Protocol for the Efficient Radiolabeling of Gold Nanoparticles by Using a 125I-labeled Azide Prosthetic Group. J. Vis. Exp. (116), e54759, doi:10.3791/54759 (2016).

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