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.

Caution: The oxidized form of radioactive iodine is quite volatile and must be handled with adequate lead shields and lead vials. All radiochemical steps should be carried out in a well-ventilated charcoal-filtered hood, and the experimental procedures need to be monitored by radioactivity detection devices.
1. Preparation of Chemicals and the Reverse Phase Cartridge for the Synthesis of the 125I-labeled Azide
<ol>
	<li>Preparation of reagents in solution
	<ol>
		<li>Dissolve 1 mg of ...

<ol>
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In general, the observed radiochemical yield of the purified 125I-labeled azide (1) was 75 &#177; 10% (n = 8). The radiolabeling was accomplished with 50-150 MBq of radioactivity, and the radiochemical results are quite consistent. If [125I]NaI (t1/2 = 59.4 d) that underwent radioactive decay for more than a month was used in the radioiodination reaction, the radiochemical yield of 1 was observed to be slightly decreased (53-65%). Therefore, it i...

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.

<table border="0" cellpadding="0" cellspacing="0" width="683">
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		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">Chloramine T trihydrate</td>
			<td style="width:101px;">Sigma</td>
			<td style="width:160px;">402869</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:255px;">[125I]NaI in aq. NaOH</td>
			<td style="width:101px;">Perkin-Elmer</td>
			<td style="width:160px;">NEZ033A010MC</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">Sodium metabisulfite&#160;</td>
			<td style="width:101px;">Sigma</td>
			<td style="width:160px;">S9000</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">Formic acid</td>
			<td style="width:101px;">Sigma</td>
			<td style="width:160px;">251364</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;">Sep-Pak tC18 plus cartridge</td>
			<td style="width:101px;">Waters</td>
			<td>WAT036800</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">Dimethyl sulfoxide&#160;</td>
			<td style="width:101px;">Sigma</td>
			<td style="width:160px;">D2650</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">Acetone</td>
			<td style="width:101px;">Sigma</td>
			<td style="width:160px;">650501</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">Ethanol</td>
			<td style="width:101px;">Sigma</td>
			<td style="width:160px;">459844</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">Gold(III) chloride trihydrate</td>
			<td style="width:101px;">Sigma</td>
			<td style="width:160px;">520918</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">Tween 20&#160;</td>
			<td style="width:101px;">Sigma</td>
			<td style="width:160px;">P1379</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">DBCO PEG SH (MW 5000)</td>
			<td style="width:101px;">NANOCS</td>
			<td style="width:160px;">PG2-DBTH-5k</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:255px;">TLC silica gel 60 F254</td>
			<td style="width:101px;">Merck</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">Analytical HPLC</td>
			<td style="width:101px;">Agilent</td>
			<td style="width:160px;">1290 Infinity</td>
			<td>Model number</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">Preparative HPLC</td>
			<td style="width:101px;">Agilent</td>
			<td style="width:160px;">1260 Infinity</td>
			<td>Model number</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">Analytical C18 reverse-phase column</td>
			<td style="width:101px;">Agilent</td>
			<td style="width:160px;">Zorbax Eclipse XDB-C18</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Preparative C18 reverse-phase column</td>
			<td style="width:101px;">Agilent</td>
			<td style="width:160px;">PrepHT XDB-C18</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">Radio TLC scanner</td>
			<td style="width:101px;">Bioscan</td>
			<td style="width:160px;">AR-2000</td>
			<td>Model number</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:255px;">Radioisotope dose calibrator</td>
			<td style="width:101px;">Capintec, Inc</td>
			<td style="width:160px;">CRC -25R dose calibrator</td>
			<td>Model number</td>
		</tr>
	</tbody>
</table>

an optimized protocol for the efficient radiolabeling of gold nanoparticles by using a 125i-labeled azide prosthetic group

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 &plusmn; 10%, n = 8) and excellent radiochemical purity (&gt;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.

The radioiodination reaction of the stannylated precursor (2) was carried out using 150 MBq of [125I]NaI, acetic acid, and chloramine T at room temperature for 15 min to provide the radiolabeled product (1). After preparative HPLC purification of the crude mixture, the desired product was obtained with 75 &#177; 10% (n = 8) of radiochemical yield. Analytical HPLC revealed that the radiochemical purity of the 125I-labeled product was ...

Watch this Scientific Journal Video about An Optimized Protocol for the Efficient Radiolabeling of Gold Nanoparticles by Using a 125I-labeled Azide Prosthetic Group at JoVE.com

An Optimized Protocol for the Efficient Radiolabeling of Gold Nanoparticles by Using a 125I-labeled Azide Prosthetic Group

A detailed procedure for the synthesis of a 125I-labeled azide and the radiolabeling of dibenzocyclooctyne (DBCO)-group-conjugated, 13-nm-sized gold nanoparticles using a copper-free click reaction is described.

An Optimized Protocol for the Efficient Radiolabeling of Gold Nanoparticles by Using a 125I-labeled Azide Prosthetic Group

Here, we demonstrate a detailed protocol for the radiosynthesis of a 125I-labeled azide prosthetic group and its application to the efficient ...

The overall goal of this protocol is to provide an efficient and rapid synthetic method for radioactive iodine labeled gold nano particles using the strain promoted copper free click reaction. This method can help answer key questions in the radiochemistry field such as the synthesis of radio isotope labeled about three years as well as regular imaging probes for pad or spec imaging studies. The main advantage of this technique is that one to five iodine labeled with golden particles can be efficiently synthesized the using of azide prosthetic group with excellent radiochemical yield and radiochemical purity.Visual demonstration of this method is critical as the radio evaluation steps are difficult to learn. Since such procedures require a suitable facility and handle radio labeling experience. Along with the study, radio student Ha Eun Shim will be demonstrating the procedure.To perform the radio iodination reaction, add a precursor solution to a 1.5 mL tube. Add 10 microliters of acetic acid to the precursor solution at room temperature. Then add 150 mega bekarel of iodine 125 in 50 microliters, 0.1 molar sodium hydroxide to the reaction mixture.Add a chloramine T solution and close the microcentrifuge tube containing the reaction mixture. Incubate the reaction mixture at room temperature for fifteen minutes until the radio iodination reaction is complete. Then add a sodium metabisulfite solution to the reaction mixture to quench the radio iodination reaction.Withdraw 0.2 microliters of the crude product and then dilute it with 100 microliters of 50%aceto nitryl in water for high performance liquid chromatography, or HPLC analysis. Analyze the diluted crude product by using a reversed phase analytical radio HPLC. Transfer the entire reaction mixture to an HPLC vial.Rinse the reaction tube with 0.5 mL of aceto nitryl and add the rinse into the same injection vial. Dilute the collected solution with one mL of water. To purify the crude product with reparative HPLC, inject the crude product onto a preparative radio HPLC.Collect the radioactive peak representing the iodine 125 labeled azide in a glass test tube. Measure the radio chemical yield of the fraction using a radioactivity dose calibrator according to the manufacturer's protocol. Then inject the purified product onto an analytical radio HPLC using the same HPLC conditions for determining the radio chemical purity of the product.To perform solid phase extraction of the product, dilute the fraction containing the desired product with 40 mL of pure water. Add the diluted solution into a preconditioned TC18 cartridge. Wash the cartridge with an additional 15 mL of water.Elute the product trapped in the cartridge with 2 mL of acetone into a 10 mL glass vial that is protected by a lead shield. Measure the radioactivity of the eluted product using radioactivity dose calibrator according to the manufacturer's protocol. After evaporating the acetone dissolve the residue with 100 to 200 microliters of DMSO for the next radio labeling step.Perform the synthesis of DBCO group modified gold nanoparticles as described in the text protocol. Prepare a concentrated solution of the DBCO group modified gold nanoparticles by using centrifugation. And adjust the concentration of the gold nano particles to two micro molar.Add 4.1 mega bekarel of iodine 125 labeled azide in 5 microliters of DMSO to a suspension of 50 microliters of 2 micro molar gold nanoparticles. Incubate the resulting reaction mixture at 40 degrees Celsius for 60 minutes. Withdraw a 0.2 microliter alloquot from the crude product and apply it onto a silica coded thin layer chromatography or TLC plate.Develop the TLC plate using ethyl acetate as a mobile phase. Place the TLC plate on a radio TLC scanner and run the scanner to monitor the radio labeling reaction according to the manufacturer's protocol. Purify the reaction mixture containing the iodine 125 labeled gold nanoparticles by centrifugation.Decant the supernatant and add pure water for resuspension of the gold nanoparticle pellets. Withdraw a 0.2 microliter alloquot from the purified product and apply it onto a silica coated TLC plate. Develop the TLC plate using ethyl acetate as the mobile phase.Place the TLC plate on a radio TLC scanner and run the scanner to determine the radiochemical yield and radiochemical purity of the iodine 125 labeled gold nanoparticles, according to the manufacturer's protocol. Representative results of the iodine 125 labeled azide prosthetic group are shown here. A 75%radiochemical yield was determined by using a radioactivity dose calibrator.The analytical radio HPLC result shows excellent radiochemical purity of the product. Representative results of the iodine 125 labeled gold nanoparticle are shown here. Radio TLC analysis presents that both radiochemical yield and purity of the purified gold nano particle were more than 95%Once mastered this technique can be done in three hours if it is performed properly.The implications of this technique extended toward preparation of various molecular probes for nuclear imaging therapeutic purposes because the labeling chemistry in the present method is highly efficient and straightforward. Don't forget that working with radioactive iodine can be extremely hazardous and the precautions such as lighter bricks or lighter shoes should always be taken while performing this procedure.

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8.1K vistas.  Korea Atomic Energy Research Institute. The overall goal of this protocol is to provide an efficient and rapid synthetic method for radioactive iodine labeled gold nano particles using the strain promoted copper free click reaction. This method can help answer key questions in the radiochemistry field such as the synthesis of radio isotope labeled about three years as well as regular imaging probes for pad or spec imaging studies. The main advantage of this technique is that one to five iodine labeled with golden particles can be e...