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 the azide precursor (2) in 150 &#181;l absolute ethanol (Figure 1). 
		NOTE: A detailed synthetic procedure for the azide precursor (2) was reported in the previous paper22.</li>
		<li>Dissolve 1 mg chloramine T in 20 &#181;l of 1x phosphate buffer saline (pH = 7.4).</li>
		<li>Dissolve 2 mg sodium metabisulfite in 20 &#181;l H2O.</li>
	</ol>
	</li>
	<li>Preparation of the cartridge
	<ol>
		<li>Wash the tC18 cartridge with 10 ml absolute ethanol followed by 10 ml H2O. Do not dry the matrix of the cartridge with air.</li>
	</ol>
	</li>
</ol>
2. Radiosynthesis of the 125I-labeled Azide Prosthetic Group
<ol>
	<li>Radioiodination reaction of the precursor
	<ol>
		<li>Add the azide precursor solution (1 mg in 150 &#181;l of absolute ethanol) and acetic acid (10 &#181;l) to a 1.5 ml microcentrifuge tube.</li>
		<li>Add 150 MBq of [125I]NaI in 0.1 M NaOH (50 &#181;l) to the reaction mixture.</li>
		<li>Add a chloramine T solution (1 mg in 20 &#181;l of 1x phosphate buffer saline) and close the microcentrifuge tube containing reaction mixture.</li>
		<li>Incubate the reaction mixture at room temperature for 15 min until the radioiodination reaction is completed.</li>
		<li>Add a sodium metabisulfite solution (2 mg in 20 &#181;l H2O) to the reaction mixture to quench the radioiodination reaction.</li>
		<li>Withdraw 0.2 &#181;l of the crude product and then dilute it with 100 &#181;l of solution (H2O/CH3CN, 1:1) for HPLC analysis. 
		NOTE: For all HPLC experiments, use 0.1% formic acid containing H2O (solvent A) and 0.1% formic acid containing acetonitrile (solvent B) as eluents.</li>
		<li>Analyze the diluted crude product by using a reverse-phase analytical radio-HPLC (C18 reverse-phase column; flow rate: 1 ml/min; eluent gradient: 20% solvent B for 0-2 min, 20-80% solvent B for 2-22 min, 80-100% solvent B for 22-23 min, and 100% solvent B for 23-28 min; retention time: 16.4 min) (Figure 2).</li>
	</ol>
	</li>
	<li>Purification of the crude product with a preparative HPLC 
	NOTE: Provide enough lead shielding around HPLC parts such as the injector, column, detector, collection vials, and the container in which the effluent is collected.
	<ol>
		<li>Withdraw the entire reaction mixture into an HPLC vial. Rinse the reaction tube with acetonitrile (0.5 ml) and add the rinse into the same injection vial. Dilute the collected solution with H2O (1 ml).</li>
		<li>Inject the crude product onto a preparative radio-HPLC (C18 reverse-phase column; flow rate: 10 ml/min; eluent gradient: 20% solvent B for 0-2 min, 20-80% solvent B for 2-22 min, 80-100% solvent B for 22-23 min, and 100% solvent B for 23-28 min).</li>
		<li>Collect the radioactive peak representing the 125I-labeled azide (1) (tR under these HPLC conditions is 17.8-18.8 min) in a glass test tube (Figure 2).</li>
		<li>Measure the radiochemical yield of the fraction using a radioactivity dose calibrator according to the manufacturer&#39;s protocol.</li>
		<li>Inject the purified product onto an analytical radio-HPLC using the same HPLC conditions for determining the radiochemical purity of the product.</li>
	</ol>
	</li>
	<li>Solid phase extraction of the product
	<ol>
		<li>Dilute the fraction containing the desired product (1) with 40 ml pure H2O.</li>
		<li>Add the diluted solution into a preconditioned tC18 cartridge.</li>
		<li>Wash the cartridge with an additional 15 ml H2O.</li>
		<li>Elute the product (1) trapped in the cartridge with 2 ml acetone into a 10-ml glass vial that is protected by a lead shield. Measure the radioactivity of the eluted product using a radioactivity dose calibrator according to the manufacturer&#39;s protocol. 
		NOTE: Dimethyl sulfoxide (DMSO) or absolute ethanol can also be used for elution of the product from the cartridge. Approximately 5-10% of the radioactivity normally sticks to the cartridge, and the remaining radiolabeled product cannot be fully eluted by using excess amounts of organic solvent.</li>
		<li>Evaporate the acetone with a stream of nitrogen or argon gas.</li>
		<li>Dissolve the residue with DMSO (100-200 &#181;l) for the next radiolabeling step.</li>
	</ol>
	</li>
</ol>
3. Synthesis of DBCO-group-conjugated Gold Nanoparticles
<ol>
	<li>Surface modification of 13-nm-sized gold nanoparticles with DBCO-group-containing polyethylene glycol
	<ol>
		<li>Prepare sodium-citrate-stabilized gold nanoparticles (3) (average size = 13 nm) according to a previous report24.</li>
		<li>Add an aqueous solution of Tween 20 (1 mM, 1.5 ml) to the citrate-stabilized gold nanoparticles (10 nM, 15 ml). Shake the solution for 20 min on an orbital shaker.</li>
		<li>Add an aqueous solution of DBCO-group-containing polyethylene glycol thiol (average molecular weight = 5,000, 100 &#956;M, 1.5 ml). Shake the solution for 2 hr on an orbital shaker.</li>
	</ol>
	</li>
	<li>Purification of the DBCO-group-modified gold nanoparticles
	<ol>
		<li>Purify the DBCO-group-modified gold nanoparticles (4) by successive centrifugation (11,400 x g, 15 min x 3).</li>
		<li>Decant the supernatant and add pure water for resuspension of the gold nanoparticle pellets.</li>
	</ol>
	</li>
</ol>
4. Radiolabeling of DBCO-group-modified Gold Nanoparticles via the Copper-free Click Reaction
<ol>
	<li>Synthesis of 125I-labeled gold nanoparticles using the 125I-labeled azide (1)
	<ol>
		<li>Prepare a concentrated solution of DBCO-group-modified gold nanoparticles by using centrifugation (11,400 x g, 15 min), and adjust the concentration of the gold nanoparticles to 2 &#181;M.</li>
		<li>Add 4.1 MBq of the 125I-labeled azide (1) in DMSO (5 &#181;l) to a suspension of gold nanoparticles (4) (2 &#956;M, 50 &#181;l).</li>
		<li>Incubate the resulting reaction mixture at 40 &#176;C for 60 min.</li>
		<li>Withdraw an aliquot (0.2 &#181;l) from the crude product and apply it onto a silica-coated thin-layer chromatography (TLC) plate.</li>
		<li>Develop the TLC plate using ethyl acetate as a mobile phase.</li>
		<li>Place the TLC plate on a radio-TLC scanner and run the scanner to monitor the radiolabeling reaction (Figure 3) according to the manufacturer&#39;s protocol.</li>
	</ol>
	</li>
	<li>Purification of the crude product
	<ol>
		<li>Purify the reaction mixture containing the 125I-labeled gold nanoparticles (4) by centrifugation (11,400 x g, 15 min).</li>
		<li>Decant the supernatant and add pure water for resuspension of the gold nanoparticle pellets.</li>
		<li>Withdraw an aliquot (0.2 &#181;l) from the purified product and apply it onto a silica-coated TLC plate.</li>
		<li>Develop the TLC plate using ethyl acetate as the mobile phase.</li>
		<li>Place the TLC plate on a radio-TLC scanner and run the scanner to determine the radiochemical yield and radiochemical purity of the 125I-labeled gold nanoparticles (4) (Figure 3) according to the manufacturer&#39;s protocol.</li>
	</ol>
	</li>
</ol>

<ol>
	<li>Jewett, J. C., Bertozzi, C. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cu-free+Click+Cycloaddition+Reactions+in+Chemical+Biology.">Cu-free Click Cycloaddition Reactions in Chemical Biology.</a> Chem. Soc. Rev. 39, 1272-1279 (2010).</li><li>Debets, M. F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bioconjugation+with+Strained+Alkenes+and+Alkyne.">Bioconjugation with Strained Alkenes and Alkyne.</a> Acc. Chem. Res. 44, 805-815 (2011).</li><li>Sletten, E. M., Bertozzi, C. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=From+Mechanism+to+Mouse:+A+Tale+of+Two+Bioorthogonal+Reactions.">From Mechanism to Mouse: A Tale of Two Bioorthogonal Reactions.</a> Acc. Chem. Res. 44, 666-676 (2011).</li><li>Koo, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bioorthogonal+Cu-Free+Click+Chemistry+in+vivo+for+Tumor-Targeted+Delivery+of+Nanoparticles.">Bioorthogonal Cu-Free Click Chemistry in vivo for Tumor-Targeted Delivery of Nanoparticles.</a> Angew. Chem. Int. Ed. 51, 11836-11840 (2012).</li><li>Chang, P. V., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Copper-Free+Click+Chemistry+in+Living+Animals.">Copper-Free Click Chemistry in Living Animals.</a> Proc. Natl. Acad. Sci. U. S. A. 107, 1821-1826 (2010).</li><li>Bostic, H. E., Smith, M. D., Poloukhtine, A. A., Popik, V. V., Best, M. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Membrane+Labeling+and+Immobilization+via+copper-free+Click+Chemistry.">Membrane Labeling and Immobilization via copper-free Click Chemistry.</a> Chem. Commun. 48, 1431-1433 (2012).</li><li>Someya, T., Ando, A., Kimoto, M., Hirao, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Site-Specific+Labeling+of+RNA+by+Combining+Genetic+Alphabet+Expansion+Transcription+and+Copper-Free+Click+Chemistry.">Site-Specific Labeling of RNA by Combining Genetic Alphabet Expansion Transcription and Copper-Free Click Chemistry.</a> Nucl. Acids Res. 43, 6665-6676 (2015).</li><li>Lee, S. B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mesoporous+Silica+Nanoparticle+Pretargeting+for+PET+Imaging+Based+on+a+Rapid+Bioorthogonal+Reaction+in+a+Living+Body.">Mesoporous Silica Nanoparticle Pretargeting for PET Imaging Based on a Rapid Bioorthogonal Reaction in a Living Body.</a> Angew. Chem. Int. Ed. 52, 10549-10552 (2013).</li><li>Sachin, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=F-18+Labeling+Protocol+of+Peptides+Based+on+Chemically+Orthogonal+Strain-Promoted+Cycloaddition+under+Physiologically+Friendly+Reaction+Conditions.">F-18 Labeling Protocol of Peptides Based on Chemically Orthogonal Strain-Promoted Cycloaddition under Physiologically Friendly Reaction Conditions.</a> Bioconjugate Chem. 23, 1680-1686 (2012).</li><li>Evans, H. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Copper-Free+Click+-+A+Promising+Tool+for+Pre-targeted+PET+Imaging.">Copper-Free Click - A Promising Tool for Pre-targeted PET Imaging.</a> Chem. Commun. 48, 991-993 (2012).</li><li>Campbell-Verduyn, L. S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Strain-Promoted+Copper-Free+&amp;#34;Click&amp;#34;+Chemistry+for+18F+Radiolabeling+of+Bombesin.">Strain-Promoted Copper-Free &amp;#34;Click&amp;#34; Chemistry for 18F Radiolabeling of Bombesin.</a> Angew. Chem. Int. Ed. 50, 11117-11120 (2011).</li><li>Arumugam, S., Chin, J., Schirrmacher, R., Popik, V. V., Kostikov, A. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=18F]Azadibenzocyclooctyne+([18F]ADIBO):+A+Biocompatible+Radioactive+Labeling+Synthon+for+Peptides+using+Catalyst+Free+[3+2]+Cycloaddition.">18F]Azadibenzocyclooctyne ([18F]ADIBO): A Biocompatible Radioactive Labeling Synthon for Peptides using Catalyst Free [3+2] Cycloaddition.</a> Bioorg. Med. Chem. Lett. 21, 6987-6991 (2011).</li><li>Bouvet, V., Wuest, M., Wuest, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Copper-Free+Click+Chemistry+with+the+Short-Lived+Positron+Emitter+Fluorine-18.">Copper-Free Click Chemistry with the Short-Lived Positron Emitter Fluorine-18.</a> Org. Biomol. Chem. 9, 7393-7399 (2011).</li><li>Satpati, D., Bauer, N., Hausner, S. H., Sutcliffe, J. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synthesis+of+[64Cu]DOTA-ADIBON3-Ala-PEG28-A20FMDV2+via+Copper-Free+Click+Chemistry+for+PET+Imaging+of+Integrin+&#945;v&#946;6.">Synthesis of [64Cu]DOTA-ADIBON3-Ala-PEG28-A20FMDV2 via Copper-Free Click Chemistry for PET Imaging of Integrin &#945;v&#946;6.</a> J. Radioanal. Nucl. Chem. 302, 765-771 (2014).</li><li>Lee, D. E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Facile+Method+To+Radiolabel+Glycol+Chitosan+Nanoparticles+with+64Cu+via+Copper-Free+Click+Chemistry+for+MicroPET+Imaging.">Facile Method To Radiolabel Glycol Chitosan Nanoparticles with 64Cu via Copper-Free Click Chemistry for MicroPET Imaging.</a> Mol. Pharmaceutics. 10, 2190-2198 (2013).</li><li>Zeng, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=64Cu+Core-Labeled+Nanoparticles+with+High+Specific+Activity+via+Metal-Free+Click+Chemistry.">64Cu Core-Labeled Nanoparticles with High Specific Activity via Metal-Free Click Chemistry.</a> ACS Nano. 6, 5209-5219 (2012).</li><li>Jeon, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Radiosynthesis+and+in+vivo+Evaluation+of+[125I]2-4(iodophenethyl)-2-Methylmalonic+Acid+as+a+Potential+Radiotracer+for+Detection+of+Apoptosis.">Radiosynthesis and in vivo Evaluation of [125I]2-4(iodophenethyl)-2-Methylmalonic Acid as a Potential Radiotracer for Detection of Apoptosis.</a> J. Radioanal. Nucl. Chem. 308, 23-29 (2016).</li><li>Adam, M. J., Wilbur, D. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Radiohalogens+for+Imaging+and+Therapy.">Radiohalogens for Imaging and Therapy.</a> Chem. Soc. Rev. 34, 153-163 (2005).</li><li>Jeon, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Radiosynthesis+of+123I-Labeld+Hesperetin+for+Biodistribution+Study+of+Orally+Administered+Hesperetin.">Radiosynthesis of 123I-Labeld Hesperetin for Biodistribution Study of Orally Administered Hesperetin.</a> J. Radioanal. Nucl. Chem. 306, 437-443 (2015).</li><li>Kil, K. E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+[123I]IPEB+and+[123I]IMPEB+as+SPECT+Radioligands+for+Metabotropic+Glutamate+Receptor+Subtype.">Development of [123I]IPEB and [123I]IMPEB as SPECT Radioligands for Metabotropic Glutamate Receptor Subtype.</a> ACS Med. Chem. Lett. 5, 652-656 (2014).</li><li>Chen, M. K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Utility+of+I-123+Pretherapy+Scan+in+I-131+Radioiodine+Therapy+for+Thyroid+Cancer.">The Utility of I-123 Pretherapy Scan in I-131 Radioiodine Therapy for Thyroid Cancer.</a> Thyroid. 22, 304-309 (2012).</li><li>Jeon, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Efficient+Method+for+Iodine+Radioisotope+Labeling+of+Cyclooctyne-Containing+Molecules+using+Strain-Promoted+Copper-Free+Click+Reaction.">Efficient Method for Iodine Radioisotope Labeling of Cyclooctyne-Containing Molecules using Strain-Promoted Copper-Free Click Reaction.</a> Bioorg. Med. Chem. 23, 3303-3308 (2015).</li><li>Choi, M. H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synthesis+and+Evaluation+of+an+125I-Labeled+Azide+Prosthetic+Group+for+Efficient+and+Bioorthogonal+Radiolabeling+of+Cyclooctyne-Group+Containing+Molecules+using+Copper-Free+Click+Reaction.">Synthesis and Evaluation of an 125I-Labeled Azide Prosthetic Group for Efficient and Bioorthogonal Radiolabeling of Cyclooctyne-Group Containing Molecules using Copper-Free Click Reaction.</a> Bioorg. Med. Chem. Lett. 26, 875-878 (2016).</li><li>Kim, Y. H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tumor+Targeting+and+Imaging+Using+Cyclic+RGD-PEGylated+Gold+Nanoparticle+Probes+with+Directly+Conjugated+Iodine-125.">Tumor Targeting and Imaging Using Cyclic RGD-PEGylated Gold Nanoparticle Probes with Directly Conjugated Iodine-125.</a> Small. 7, 2052-2060 (2011).</li></ol>

The authors have nothing to disclose.

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">
	<colgroup>
		<col />
		<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 ...

an-optimized-protocol-for-efficient-radiolabeling-gold-nanoparticles

Research

JoVE Journal

Chemistry

8.1K Views.  Korea Atomic Energy Research Institute. 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.

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

Stabilizing Hepatocellular Phenotype Using Optimized Synthetic Surfaces

Currently, one of the major limitations in cell biology is maintaining differentiated cell phenotype. Biological matrices are commonly used for culturing and maintaining primary and pluripotent stem cell derived hepatocytes. While biological matrices are useful, they permit short term culture of hepatocytes, limiting their widespread application. We have attempted to overcome the limitations using a synthetic polymer coating. Polymers represent one of the broadest classes of biomaterials and possess a wide range of mechanical, physical and chemical properties, which can be fine-tuned for purpose. Importantly, such materials can be scaled to quality assured standards and display batch-to-batch consistency. This is essential if cells are to be expanded for high through-put screening in the pharmaceutical testing industry or for cellular based therapy. Polyurethanes (PUs) are one group of materials that have shown promise in cell culture. Our recent progress in optimizing a polyurethane coated surface, for long-term culture of human hepatocytes displaying stable phenotype, is presented and discussed.

This article will focus on developing polymer coated surfaces for long-term, stable culture of stem cell derived human hepatocytes.

Currently, one of the major limitations in cell biology is maintaining differentiated cell phenotype. Biological matrices are commonly used for culturing ...

A Simple Method for the Size Controlled Synthesis of Stable Oligomeric Clusters of Gold Nanoparticles under Ambient Conditions

Reducing dilute aqueous HAuCl4 with sodium thiocyanate (NaSCN) under alkaline conditions produces 2 to 3 nm diameter nanoparticles. Stable grape-like oligomeric clusters of these yellow nanoparticles of narrow size distribution are synthesized under ambient conditions via two methods. The delay-time method controls the number of subunits in the oligoclusters by varying the time between the addition of HAuCl4 to alkaline solution and the subsequent addition of reducing agent, NaSCN. The yellow oligoclusters produced range in size from ~3 to ~25 nm. This size range can be further extended by an add-on method utilizing hydroxylated gold chloride (Na+[Au(OH4-x)Clx]-) to auto-catalytically increase the number of subunits in the as-synthesized oligocluster nanoparticles, providing a total range of 3 nm to 70 nm. The crude oligocluster preparations display narrow size distributions and do not require further fractionation for most purposes. The oligoclusters formed can be concentrated &#62;300 fold without aggregation and the crude reaction mixtures remain stable for weeks without further processing. Because these oligomeric clusters can be concentrated before derivatization they allow expensive derivatizing agents to be used economically. In addition, we present two models by which predictions of particle size can be made with great accuracy.

We describe a simple method for producing highly stable oligomeric clusters of gold nanoparticles via the reduction of chloroauric acid (HAuCl4) with sodium thiocyanate (NaSCN). The oligoclusters have a narrow size distribution and can be produced with a wide range of sizes and surface coats.

Reducing dilute aqueous HAuCl4 with sodium thiocyanate (NaSCN) under alkaline conditions produces 2 to 3 nm diameter nanoparticles. Stable grape-like ...

A Protocol for the Production of Gliadin-cyanoacrylate Nanoparticles for Hydrophilic Coating

This article presents a protocol for the production of protein-based nanoparticles that changes the hydrophobic surface to hydrophilic by a simple spray coating. These nanoparticles are produced by the polymerization reaction of alkyl cyanoacrylate on the surface of cereal protein (gliadin) molecules. Alkyl cyanoacrylate is a monomer that instantly polymerizes at RT when it is applied to the surface of materials. Its polymerization reaction is initiated by the trace amounts of weakly basic or nucleophilic species on the surface, including moisture. Once polymerized, the polymerized alkyl cyanoacrylates show a strong affinity with the object materials because nitrile groups are in the backbone of poly (alkyl cyanoacrylate). Proteins also work as initiator for this polymerization because they contain amine groups that can initiate the polymerization of cyanoacrylate. If aggregated protein is used as an initiator, protein aggregate is surrounded by the hydrophobic poly(alkyl cyanoacrylate) chains after the polymerization reaction of alkyl cyanoacrylate. By controlling the experimental condition, particles in the nanometer range are produced. The produced nanoparticles readily adsorb to the surface of most materials including glass, metals, plastics, wood, leather, and fabrics. When the surface of a material is sprayed with the produced nanoparticle suspension and rinsed with water, the micellar structure of nanoparticle changes its conformation, and the hydrophilic proteins are exposed to the air. As a result, the nanoparticle-coated surface changes to hydrophilic.

This article presents a protocol for the production of protein-based nanoparticles that changes the hydrophobic surface to hydrophilic. The produced nanoparticle is an assembly of gliadin-cyanoacrylate diblock copolymers. Spray coating with the produced nanoparticle changes the surface of target material to a hydrophilic surface.

This article presents a protocol for the production of protein-based nanoparticles that changes the hydrophobic surface to hydrophilic by a simple spray ...

A Simple and Efficient Protocol for the Catalytic Insertion Polymerization of Functional Norbornenes

Norbornene can be polymerized by a variety of mechanisms, including insertion polymerization whereby the double bond is polymerized and the bicyclic nature of the monomer is conserved. The resulting polymer, polynorbornene, has a very high glass transition temperature, Tg, and interesting optical and electrical properties. However, the polymerization of functional norbornenes by this mechanism is complicated by the fact that the endo substituted norbornene monomer has, in general, a very low reactivity. Furthermore, the separation of the endo substituted monomer from the exo monomer is a tedious task. Here, we present a simple protocol for the polymerization of substituted norbornenes (endo:exo ca. 80:20) bearing either a carboxylic acid or a pendant double bond. The process does not require that both isomers be separated, and proceeds with low catalyst loadings (0.01 to 0.02 mol%). The polymer bearing pendant double bonds can be further transformed in high yield, to afford a polymer bearing pendant epoxy groups. These simple procedures can be applied to prepare polynorbornenes with a variety of functional groups, such as esters, alcohols, imides, double bonds, carboxylic acids, bromo-alkyls, aldehydes and anhydrides.

We describe the catalytic insertion polymerization of 5-norbornene-2-carboxylic acid and 5-vinyl-2-norbornene to form functional polymers with a very high glass transition temperature.

Norbornene can be polymerized by a variety of mechanisms, including insertion polymerization whereby the double bond is polymerized and the bicyclic ...

A Protocol for Safe Lithiation Reactions Using Organolithium Reagents

Organolithium reagents are powerful tools in the synthetic chemist&#39;s toolbox. However, the extreme pyrophoric nature of the most reactive reagents warrants proper technique, thorough training, and proper personal protective equipment. To aid in the training of researchers using organolithium reagents, a thorough, step-by-step protocol for the safe and effective use of tert-butyllithium on an inert gas line or within a glovebox is described. As a model reaction, preparation of lithium tert-butyl amide by the reaction of tert-butyl amine with one equivalent of tert-butyl lithium is presented.

The safe and proper use of organolithium reagents is described.

Organolithium reagents are powerful tools in the synthetic chemist&#39;s toolbox. However, the extreme pyrophoric nature of the most reactive reagents ...

Rapid Nanoprobe Signal Enhancement by In Situ Gold Nanoparticle Synthesis

The use of nanoprobes such as gold, silver, silica or iron-oxide nanoparticles as detection reagents in bioanalytical assays can enable high sensitivity and convenient colorimetric readout. However, high densities of nanoparticles are typically needed for detection. The available synthesis-based enhancement protocols are either limited to gold and silver nanoparticles or rely on precise enzymatic control and optimization. Here, we present a protocol to enhance the colorimetric readout of gold, silver, silica, and iron oxide nanoprobes. It was observed that the colorimetric signal can be improved by up to a 10000-fold factor. The basis for such signal enhancement strategies is the chemical reduction of Au3+ to Au0. There are several chemical reactions that enable the reduction of Au3+ to Au0. In the protocol, Good&#39;s buffers and H2O2 are used and it is possible to favor the deposition of Au0 onto the surface of existing nanoprobes, in detriment of the formation of new gold nanoparticles. The protocol consists of the incubation of the microarray with a solution consisting of chloroauric acid and H2O2 in 2-(N-morpholino)ethanesulfonic acid pH 6 buffer following the nanoprobe-based detection assay. The enhancement solution can be applied to paper and glass-based sensors. Moreover, it can be used in commercially available immunoassays as demonstrated by the application of the method to a commercial allergen microarray. The signal development requires less than 5 min of incubation with the enhancement solution and the readout can be assessed by naked eye or low-end image acquisition devices such as a table-top scanner or a digital camera.

Rapid Nanoprobe Signal Enhancement by In Situ Gold Nanoparticle Synthesis

In this work, a protocol for signal enhancement of nanoprobe-based biosensing is presented. The protocol is based on the reduction of chloroauric acid onto the surface of existing nanoprobes that consist of gold, silver, silica or iron-oxide nanoparticles.

The use of nanoprobes such as gold, silver, silica or iron-oxide nanoparticles as detection reagents in bioanalytical assays can enable high sensitivity ...

The MPLEx Protocol for Multi-omic Analyses of Soil Samples

Mass spectrometry (MS)-based integrated metaproteomic, metabolomic, and lipidomic (multi-omic) studies are transforming our ability to understand and characterize microbial communities in environmental and biological systems. These measurements are even enabling enhanced analyses of complex soil microbial communities, which are the most complex microbial systems known to date. Multi-omic analyses, however, do have sample preparation challenges, since separate extractions are typically needed for each omic study, thereby greatly amplifying the preparation time and amount of sample required. To address this limitation, a 3-in-1 method for the simultaneous extraction of metabolites, proteins, and lipids (MPLEx) from the same soil sample was created by adapting a solvent-based approach. This MPLEx protocol has proven to be both simple and robust for many sample types, even when utilized for limited quantities of complex soil samples. The MPLEx method also greatly enabled the rapid multi-omic measurements needed to gain a better understanding of the members of each microbial community, while evaluating the changes taking place upon biological and environmental perturbations.

A protocol is presented for simultaneously extracting metabolites, proteins, and lipids from a single soil sample, allowing reduced sample preparation times and enabling multi-omic mass spectrometry analyses of samples with limited quantities.

Mass spectrometry (MS)-based integrated metaproteomic, metabolomic, and lipidomic (multi-omic) studies are transforming our ability to understand and ...

Luminophore Formation in Various Conformations of Bovine Serum Albumin by Binding of Gold(III)

The purpose of the presented protocols is to study the process of Au(III) binding to BSA, yielding conformation change-induced red fluorescence (&#955;em = 640 nm) of BSA-Au(III) complexes. The method adjusts the pH to show that the emergence of the red fluorescence is correlated with the pH-induced equilibrium transitions of the BSA conformations. Red fluorescent BSA-Au(III) complexes can only be formed with an adjustment of pH at or above 9.7, which corresponds to the &#34;A-form&#34; conformation of BSA. The protocol to adjust the BSA to Au molar ratio and to monitor the time-course of the process of Au(III) binding is described. The minimum number of Au(III) per BSA, to produce the red fluorescence, is less than seven. We describe the protocol in steps to illustrate the presence of multiple Au(III) binding sites in BSA. First, by adding copper (Cu(II)) or nickel (Ni(II)) cations followed by Au(III), this method reveals a binding site for Au(III) that is not the red fluorophore. Second, by modifying BSA by thiol capping agents, another nonfluorophore-forming Au(III) binding site is revealed. Third, changing the BSA conformation by cleaving and capping of the disulfide bonds, the possible Au(III) binding site(s) are illustrated. The protocol described, to control the BSA conformations and Au(III) binding, can be generally applied to study the interactions of other proteins and metal cations.

Luminophore Formation in Various Conformations of Bovine Serum Albumin by Binding of GoldIII

The protocols for studying the binding of gold cations (Au(III)) to various conformations of bovine serum albumin (BSA) as well as for characterizing the conformational dependent unique BSA-Au fluorescence are presented.

The purpose of the presented protocols is to study the process of Au(III) binding to BSA, yielding conformation change-induced red fluorescence (&#955;em ...

Synthesis and Characterization of Amphiphilic Gold Nanoparticles

Gold nanoparticles covered with a mixture of 1-octanethiol (OT) and 11-mercapto-1-undecane sulfonic acid (MUS) have been extensively studied because of their interactions with cell membranes, lipid bilayers, and viruses. The hydrophilic ligands make these particles colloidally stable in aqueous solutions and the combination with hydrophobic ligands creates an amphiphilic particle that can be loaded with hydrophobic drugs, fuse with the lipid membranes, and resist nonspecific protein adsorption. Many of these properties depend on nanoparticle size and the composition of the ligand shell. It is, therefore, crucial to have a reproducible synthetic method and reliable characterization techniques that allow the determination of nanoparticle properties and the ligand shell composition. Here, a one-phase chemical reduction, followed by a thorough purification to synthesize these nanoparticles with diameters below 5 nm, is presented. The ratio between the two ligands on the surface of the nanoparticle can be tuned through their stoichiometric ratio used during synthesis. We demonstrate how various routine techniques, such as transmission electron microscopy (TEM), nuclear magnetic resonance (NMR), thermogravimetric analysis (TGA), and ultraviolet-visible (UV-Vis) spectrometry, are combined to comprehensively characterize the physicochemical parameters of the nanoparticles.

Amphiphilic gold nanoparticles can be used in many biological applications. A protocol to synthesize gold nanoparticles coated by a binary mixture of ligands and a detailed characterization of these particles is presented.

Gold nanoparticles covered with a mixture of 1-octanethiol (OT) and 11-mercapto-1-undecane sulfonic acid (MUS) have been extensively studied because of ...

Synthesis of Aptamer-PEI-g-PEG Modified Gold Nanoparticles Loaded with Doxorubicin for Targeted Drug Delivery

Due to drug resistance and toxicity in healthy cells, use of doxorubicin (DOX) has been limited in clinical cancer therapy. This protocol describes the designing of poly(ethylenimine) grafted with polyethylene glycol (PEI-g-PEG) copolymer functionalized gold nanoparticles (AuNPs) with loaded aptamer (AS1411) and DOX through amide reactions. AS1411 is specifically bonded with targeted nucleolin receptors on cancer cells so that DOX targets cancer cells instead of healthy cells. First, PEG is carboxylated, then grafted to branched PEI to obtain a PEI-g-PEG copolymer, which is confirmed by 1H NMR analysis. Next, PEI-g-PEG copolymer coated gold nanoparticles (PEI-g-PEG@AuNPs) are synthesized, and DOX and AS1411 are covalently bonded to AuNPs gradually via amide reactions. The diameter of the prepared AS1411-g-DOX-g-PEI-g-PEG@AuNPs is ~39.9 nm, with a zeta potential of -29.3 mV, indicating that the nanoparticles are stable in water and cell medium. Cell cytotoxicity assays show that the newly designed DOX loaded AuNPs are able to kill cancer cells (A549). This synthesis demonstrates the delicate arrangement of PEI-g-PEG copolymers, aptamers, and DOX on AuNPs that are achieved by sequential amide reactions. Such aptamer-PEI-g-PEG functionalized AuNPs provide a promising platform for targeted drug delivery in cancer therapy.

In this protocol, doxorubicin-loaded AS1411-g-PEI-g-PEG modified gold nanoparticles are synthesized via three-step amide reactions. Then, doxorubicin is loaded and delivered to target cancer cells for cancer therapy.

Due to drug resistance and toxicity in healthy cells, use of doxorubicin (DOX) has been limited in clinical cancer therapy. This protocol describes the ...