Un protocollo ottimizzato per la radiomarcatura efficiente di oro nanoparticelle utilizzando un<sup> 125</sup> Azide gruppo I-etichettati protesico
Summary
Una procedura dettagliata per la sintesi di un azide 125 I-etichettati e la radiomarcatura di dibenzocyclooctyne (DBCO) -gruppo-coniugati, nanoparticelle d'oro 13-nm dimensioni utilizzando una reazione click senza il rame è descritto.
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
Representative Results
Discussion
In generale, la resa radiochimica osservato del purificato 125 azide I-marcato (1) è stato 75 ± 10% (n = 8). La radiomarcatura è stata compiuta con 50-150 MBq di radioattività, ed i risultati radiochimiche sono abbastanza coerenti. Se [125 I] NaI (t 1/2 = 59,4 d) sottoposto decadimento radioattivo per più di un mese è stato utilizzato nella reazione radioiodination, la resa radiochimica 1 è stata osservata essere leggermente diminuita (53…
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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