This study was supported by a grant from the Spanish Ministry for Economy and Competitiveness (MEyC) (grant number: SAF2016-79593-P) and from the Carlos III Health Research Institute (grant number: DTS16/00059). The CNIC is supported by the Ministerio de Ciencia, Innovaci&#243;n y Universidades) and the Pro CNIC Foundation and is a Severo Ochoa Centre of Excellence (MEIC award SEV-2015-0505).

1. Reagent Preparation
<ol>
	<li>0.05 M HCl
	<ol>
		<li>Prepare 0.05 M HCl by adding 208 &#181;L of 37% HCl to 50 mL of distilled water.</li>
	</ol>
	</li>
	<li>High-performance liquid chromatography eluent
	<ol>
		<li>Prepare high-performance liquid chromatography (HPLC) eluent by dissolving 6.9 g of sodium dihydrogen phosphate monohydrate, 7.1 g of disodium hydrogen phosphate, 8.7 g of sodium chloride, and 0.7 g of sodium azide in 1 L of water. Mix well and check the pH. Pass the elu...

<ol>
	<li>Jennings, L. E., Long, N. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term='Two+is+better+than+one'--probes+for+dual-modality+molecular+imaging.">'Two is better than one'--probes for dual-modality molecular imaging.</a> Chemical Communications. (24), 3511-3524 (2009).</li><li>Lee, S., Chen, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dual-modality+probes+for+in+vivo+molecular+imaging.">Dual-modality probes for in vivo molecular imaging.</a> Molecular Imaging. 8 (2), 87-100 (2009).</li><li>Louie, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Multimodality+Imaging+Probes:+Design+and+Challenges.">Multimodality Imaging Probes: Design and Challenges.</a> Chemical Reviews. 110 (5), 3146-3195 (2010).</li><li>Judenhofer, M. 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=Simultaneous+PET-MRI:+a+new+approach+for+functional+and+morphological+imaging.">Simultaneous PET-MRI: a new approach for functional and morphological imaging.</a> Nature Medicine. 14 (4), 459-465 (2008).</li><li>Burtea, C., Laurent, S., Vander Elst, L., Muller, R. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Contrast+agents:+magnetic+resonance.">Contrast agents: magnetic resonance.</a> Handbook of Experimental Pharmacology. (185 Pt 1), 135-165 (2008).</li><li>Zhao, X., Zhao, H., Chen, Z., Lan, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ultrasmall+superparamagnetic+iron+oxide+nanoparticles+for+magnetic+resonance+imaging+contrast+agent.">Ultrasmall superparamagnetic iron oxide nanoparticles for magnetic resonance imaging contrast agent.</a> Journal of Nanoscience and Nanotechnology. 14 (1), 210-220 (2014).</li><li>Cheng, W., 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=Complementary+Strategies+for+Developing+Gd-Free+High-Field+T+1+MRI+Contrast+Agents+Based+on+Mn+III+Porphyrins.">Complementary Strategies for Developing Gd-Free High-Field T 1 MRI Contrast Agents Based on Mn III Porphyrins.</a> Journal of Medicinal Chemistry. 57 (2), 516-520 (2014).</li><li>Kim, H. -. 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=Gd-complexes+of+macrocyclic+DTPA+conjugates+of+1,1&#8242;-bis(amino)ferrocenes+as+high+relaxivity+MRI+blood-pool+contrast+agents+(BPCAs).">Gd-complexes of macrocyclic DTPA conjugates of 1,1&#8242;-bis(amino)ferrocenes as high relaxivity MRI blood-pool contrast agents (BPCAs).</a> Chemical Communications. 46 (44), 8442 (2010).</li><li>Sanyal, S., Marckmann, P., Scherer, S., Abraham, 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=Multiorgan+gadolinium+(Gd)+deposition+and+fibrosis+in+a+patient+with+nephrogenic+systemic+fibrosis--an+autopsy-based+review.">Multiorgan gadolinium (Gd) deposition and fibrosis in a patient with nephrogenic systemic fibrosis--an autopsy-based review.</a> Nephrology, Dialysis, Transplantation: Official Publication of the European Dialysis and Transplant Association - European Renal Association. 26 (11), 3616-3626 (2011).</li><li>Hu, F., Jia, Q., Li, Y., Gao, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Facile+synthesis+of+ultrasmall+PEGylated+iron+oxide+nanoparticles+for+dual-contrast+T1-+and+T2-weighted+magnetic+resonance+imaging.">Facile synthesis of ultrasmall PEGylated iron oxide nanoparticles for dual-contrast T1- and T2-weighted magnetic resonance imaging.</a> Nanotechnology. 22, 245604 (2011).</li><li>Kim, B. 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=Large-Scale+Synthesis+of+Uniform+and+Extremely+Small-Sized+Iron+Oxide+Nanoparticles+for+High-Resolution+T+1+Magnetic+Resonance+Imaging+Contrast+Agents.">Large-Scale Synthesis of Uniform and Extremely Small-Sized Iron Oxide Nanoparticles for High-Resolution T 1 Magnetic Resonance Imaging Contrast Agents.</a> Journal of the American Chemical Society. 133 (32), 12624-12631 (2011).</li><li>Banerjee, S. R., Pomper, M. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Clinical+applications+of+Gallium-68.">Clinical applications of Gallium-68.</a> Applied Radiation and Isotopes. 76, 2-13 (2013).</li><li>Breeman, W. A. P., 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=68Ga-labeled+DOTA-Peptides+and+68Ga-labeled+Radiopharmaceuticals+for+Positron+Emission+Tomography:+Current+Status+of+Research,+Clinical+Applications,+and+Future+Perspectives.">68Ga-labeled DOTA-Peptides and 68Ga-labeled Radiopharmaceuticals for Positron Emission Tomography: Current Status of Research, Clinical Applications, and Future Perspectives.</a> Seminars in Nuclear Medicine. 41 (4), 314-321 (2011).</li><li>Morgat, C., Hindi&#233;, E., Mishra, A. K., Allard, M., Fernandez, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gallium-68:+chemistry+and+radiolabeled+peptides+exploring+different+oncogenic+pathways.">Gallium-68: chemistry and radiolabeled peptides exploring different oncogenic pathways.</a> Cancer Biotherapy &amp; Radiopharmaceuticals. 28 (2), 85-97 (2013).</li><li>Moon, S. -. 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=Development+of+a+complementary+PET/MR+dual-modal+imaging+probe+for+targeting+prostate-specific+membrane+antigen+(PSMA).">Development of a complementary PET/MR dual-modal imaging probe for targeting prostate-specific membrane antigen (PSMA).</a> Nanomedicine: Nanotechnology, Biology and Medicine. 12 (4), 871-879 (2016).</li><li>Kim, S. M., 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=Hybrid+PET/MR+imaging+of+tumors+using+an+oleanolic+acid-conjugated+nanoparticle.">Hybrid PET/MR imaging of tumors using an oleanolic acid-conjugated nanoparticle.</a> Biomaterials. 34 (33), 8114-8121 (2013).</li><li>Yang, B. Y., 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+a+multimodal+imaging+probe+by+encapsulating+iron+oxide+nanoparticles+with+functionalized+amphiphiles+for+lymph+node+imaging.">Development of a multimodal imaging probe by encapsulating iron oxide nanoparticles with functionalized amphiphiles for lymph node imaging.</a> Nanomedicine. 10 (12), 1899-1910 (2015).</li><li>Comes Franchini, M., 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=Biocompatible+nanocomposite+for+PET/MRI+hybrid+imaging.">Biocompatible nanocomposite for PET/MRI hybrid imaging.</a> International Journal of Nanomedicine. 7, 6021 (2012).</li><li>Karageorgou, M., 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=Gallium-68+Labeled+Iron+Oxide+Nanoparticles+Coated+with+2,3-Dicarboxypropane-1,1-diphosphonic+Acid+as+a+Potential+PET/MR+Imaging+Agent:+A+Proof-of-Concept+Study.">Gallium-68 Labeled Iron Oxide Nanoparticles Coated with 2,3-Dicarboxypropane-1,1-diphosphonic Acid as a Potential PET/MR Imaging Agent: A Proof-of-Concept Study.</a> Contrast Media &amp; Molecular Imaging. 2017, 1-13 (2017).</li><li>Madru, R., 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=(68)Ga-labeled+superparamagnetic+iron+oxide+nanoparticles+(SPIONs)+for+multi-modality+PET/MR/Cherenkov+luminescence+imaging+of+sentinel+lymph+nodes.">(68)Ga-labeled superparamagnetic iron oxide nanoparticles (SPIONs) for multi-modality PET/MR/Cherenkov luminescence imaging of sentinel lymph nodes.</a> American Journal of Nuclear Medicine and Molecular Imaging. 4 (1), 60-69 (2013).</li><li>Lahooti, A., 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=PEGylated+superparamagnetic+iron+oxide+nanoparticles+labeled+with+68Ga+as+a+PET/MRI+contrast+agent:+a+biodistribution+study.">PEGylated superparamagnetic iron oxide nanoparticles labeled with 68Ga as a PET/MRI contrast agent: a biodistribution study.</a> Journal of Radioanalytical and Nuclear Chemistry. 311 (1), 769-774 (2017).</li><li>Lee, H. -. Y., 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=PET/MRI+dual-modality+tumor+imaging+using+arginine-glycine-aspartic+(RGD)-conjugated+radiolabeled+iron+oxide+nanoparticles.">PET/MRI dual-modality tumor imaging using arginine-glycine-aspartic (RGD)-conjugated radiolabeled iron oxide nanoparticles.</a> Journal of Nuclear Medicine. 49 (8), 1371-1379 (2008).</li><li>Patel, D., 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+cell+labeling+efficacy,+cytotoxicity+and+relaxivity+of+copper-activated+MRI/PET+imaging+contrast+agents.">The cell labeling efficacy, cytotoxicity and relaxivity of copper-activated MRI/PET imaging contrast agents.</a> Biomaterials. 32 (4), 1167-1176 (2011).</li><li>Choi, 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=A+Hybrid+Nanoparticle+Probe+for+Dual-Modality+Positron+Emission+Tomography+and+Magnetic+Resonance+Imaging.">A Hybrid Nanoparticle Probe for Dual-Modality Positron Emission Tomography and Magnetic Resonance Imaging.</a> Angewandte Chemie International Edition. 47 (33), 6259-6262 (2008).</li><li>Wong, R. M., 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=Rapid+size-controlled+synthesis+of+dextran-coated,+64Cu-doped+iron+oxide+nanoparticles.">Rapid size-controlled synthesis of dextran-coated, 64Cu-doped iron oxide nanoparticles.</a> ACS Nano. 6 (4), 3461-3467 (2012).</li><li>Osborne, E. A., 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=Rapid+microwave-assisted+synthesis+of+dextran-coated+iron+oxide+nanoparticles+for+magnetic+resonance+imaging.">Rapid microwave-assisted synthesis of dextran-coated iron oxide nanoparticles for magnetic resonance imaging.</a> Nanotechnology. 23 (21), 215602 (2012).</li><li>Pellico, 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=Fast+synthesis+and+bioconjugation+of+68+Ga+core-doped+extremely+small+iron+oxide+nanoparticles+for+PET/MR+imaging.">Fast synthesis and bioconjugation of 68 Ga core-doped extremely small iron oxide nanoparticles for PET/MR imaging.</a> Contrast Media &amp; Molecular Imaging. 11 (3), 203-210 (2016).</li><li>Pellico, 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=In+vivo+imaging+of+lung+inflammation+with+neutrophil-specific+68Ga+nano-radiotracer.">In vivo imaging of lung inflammation with neutrophil-specific 68Ga nano-radiotracer.</a> Scientific Reports. 7 (1), 13242 (2017).</li></ol>

Iron oxide nanoparticles are a well-established contrast agent for T2-weighted MRI. However, due to the drawbacks of this type of contrast for the diagnosis of certain pathologies, T1-weighted or bright contrast is many times preferred. The nanoparticles presented here not only overcome these limitations by offering positive contrast in MRI but also offer a signal in a functional imaging technique, such as PET, via 68Ga incorporation in their core. Microwave technology enhances t...

The combination of imaging techniques for medical purposes has triggered the quest for different methods to synthesize multimodal probes1,2,3. Due to the sensitivity of positron emission tomography (PET) scanners and the spatial resolution of MRI, PET/MRI combinations seem to be one of the most attractive possibilities, providing anatomical and functional information at the same time4. In MRI, T2-weighted sequences can be used, darkening the tissues in which they accumulate. T1-weighted sequences may also be used, producing the brightening of the specific accumulation location5. Among them, positive contrast is often the most adequate option, as negative contrast makes it much harder to differentiate signal from endogenous hypointense areas, including those often presented by organs such as the lungs6. Traditionally, Gd-based molecular probes have been employed to obtain positive contrast. However, Gd-based contrast agents present a major drawback, namely their toxicity, which is critical in patients with renal problems7,8,9. This has motivated research in the synthesis of biocompatible materials for their use as T1 contrast agents. An interesting approach is the use of iron oxide nanoparticles (IONPs), with an extremely small core size, that provide positive contrast10. Due to this extremely small core (~2 nm), most of the Fe3+ ions are on the surface, with 5 unpaired electrons each. This increases longitudinal relaxation time (r1) values and yields much lower transversal/longitudinal (r2/r1) ratios compared to traditional IONPs, producing the desired positive contrast11.
To combine IONPs with a positron emitter for PET, there are two key issues to take into account: radioisotope election and nanoparticle radiolabeling. Regarding the first issue, 68Ga is an alluring choice. It has a relatively short half-life (67.8 min). Its half-life is suitable for peptide labeling since it matches common peptide biodistribution times. Moreover, 68Ga is produced in a generator, enabling the synthesis in bench modules and avoiding the need for a cyclotron nearby12,13,14. In order to radiolabel the nanoparticle, surface-labeling radioisotope incorporation is the prevalent strategy. This can be done using a ligand that chelates 68Ga or taking advantage of the affinity of the radiometal toward the surface of the nanoparticle. Most examples in the literature concerning IONPs use a chelator. There are examples of the use of heterocyclic ligands such as 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA)15, 1,4,7-triazacyclononane-1,4,7-triacetic acid (NOTA)16,17, and 1,4,7-triazacyclononane,1-glutaric acid-4,7-acetic acid (NODAGA)18, and the use of 2,3-dicarboxypropane-1,1-diphosphonic acid (DPD), a tetradentate ligand 19. Madru et al.20 developed a chelator-free strategy in 2014 to label IONPs using a chelator-free method used by another group posteriorly21.
However, major drawbacks of this approach include a high risk of in vivo transmetalation, low radiolabeling yields, and lengthy protocols unsuitable for short-lived isotopes22,23,24. For this reason, Wong et al.25 developed the first example of core-doped nanoparticles, managing to incorporate 64Cu in the core of the IONPs in a 5-min synthesis using microwave technology.
Here, we describe a rapid and efficient procedure to incorporate the radionuclide into the core of the nanoparticle, eluding many of the drawbacks presented by traditional methods. For this purpose, we propose the use of a microwave-driven synthesis (MWS), which reduces reaction times considerably, increases yields, and enhances reproducibility, critically important parameters in IONP synthesis. The refined performance of MWS is due to dielectric heating: rapid sample heating as molecular dipoles try to align with the alternating electric field, being polar solvents and reagents more efficient for this type of synthesis. In addition, the use of citric acid as a surfactant, together with microwave technology, results in extremely small nanoparticles, producing a dual T1-weighted MRI/PET26 signal, herein denoted as 68Ga Core-doped iron oxide nanoparticles (68Ga-C-IONP).
The protocol combines the use of microwave technology, 68GaCl3 as positron emitter, iron chloride, sodium citrate, and hydrazine hydrate, resulting in dual T1-weighted MRI/PET nanoparticulate material in hardly 20 min. Moreover, it yields consistent results over a range of 68Ga activities (37 MBq, 111 MBq, 370 MBq, and 1110 MBq) with no significant effects on the main physicochemical properties of the nanoparticles. The reproducibility of the method using high 68Ga activities extends the field of possible applications, including large animal models or human studies. In addition, there is a single purification step included in the method. In the process, any excess of free gallium, iron chloride, sodium citrate, and hydrazine hydrate are removed by gel filtration. Total free isotope elimination and the purity of the sample ensure no toxicity and enhance imaging resolution. In the past, we have already demonstrated the usefulness of this approach in targeted molecular imaging27,28.

<table>
	<tbody>
		<tr>
			<td>Iron (III) chloride hexahydrate</td>
			<td>POCH</td>
			<td>2317294</td>
			<td></td>
		</tr>
		<tr>
			<td>Citric acid, trisodium salt dihydrate 99%</td>
			<td>Acros organics</td>
			<td>227130010</td>
			<td></td>
		</tr>
		<tr>
			<td>Hydrazine hydrate</td>
			<td>Aldrich</td>
			<td>225819</td>
			<td></td>
		</tr>
		<tr>
			<td>Hydrochloric acid 37%</td>
			<td>Fisher Scientific</td>
			<td>10000180</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium dihydrogen phosphate monohydrate</td>
			<td>Aldrich</td>
			<td>S9638</td>
			<td></td>
		</tr>
		<tr>
			<td>Disodium phosphate dibasic</td>
			<td>Aldrich</td>
			<td>S7907</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium chloride</td>
			<td>Aldrich</td>
			<td>746398</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium Azide</td>
			<td>Aldrich</td>
			<td>S2002</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium dihydrogen phosphate anhydrous</td>
			<td>POCH</td>
			<td>799200119</td>
			<td></td>
		</tr>
		<tr>
			<td>68Ga Chloride</td>
			<td>&#160;ITG Isotope Technologies Garching GmbH, Germany</td>
			<td>68Ge/68Ga generator system</td>
			<td></td>
		</tr>
		<tr>
			<td>Microwave</td>
			<td>Anton Paar</td>
			<td>Monowave 300</td>
			<td></td>
		</tr>
		<tr>
			<td>Centrifuge</td>
			<td>Hettich</td>
			<td>Universal 320</td>
			<td></td>
		</tr>
		<tr>
			<td>Size Exclusion columns</td>
			<td>GE Healthcare</td>
			<td>PD-10</td>
			<td></td>
		</tr>
	</tbody>
</table>

synthesis of 68ga core-doped iron oxide nanoparticles for dual positron emission tomography /(t1)magnetic resonance imaging

Here, we describe a microwave synthesis to obtain iron oxide nanoparticles core-doped with 68Ga. Microwave technology enables fast and reproducible synthetic procedures. In this case, starting from FeCl3 and citrate trisodium salt, iron oxide nanoparticles coated with citric acid are obtained in 10 min in the microwave. These nanoparticles present a small core size of 4.2 &#177; 1.1 nm and a hydrodynamic size of 7.5 &#177; 2.1 nm. Moreover, they have a high longitudinal relaxivity (r1) value of 11.9 mM-1&#183;s-1 and a modest transversal relaxivity value (r2) of 22.9 mM-1&#183;s-1, which results in a low r2/r1 ratio of 1.9. These values enable positive contrast generation in magnetic resonance imaging (MRI) instead of negative contrast, commonly used with iron oxide nanoparticles. In addition, if a 68GaCl3 elution from a 68Ge/68Ga generator is added to the starting materials, a nano-radiotracer doped with 68Ga is obtained. The product is obtained with a high radiolabeling yield (&#62; 90%), regardless of the initial activity used. Furthermore, a single purification step renders the nano-radiomaterial ready to be used in vivo.

68Ga-C-IONP were synthesized by combining FeCl3, 68GaCl3, citric acid, water, and hydrazine hydrate. This mixture was introduced into the microwave for 10 min at 120 &#176;C and 240 W under controlled pressure. Once the sample had cooled down to room temperature, the nanoparticles were purified by gel filtration to eliminate unreacted species (FeCl3, citrate, hydrazine hydrate) and free 68Ga (Figure 1</...

Watch this Scientific Journal Video about Synthesis of 68Ga Core-doped Iron Oxide Nanoparticles for Dual Positron Emission Tomography /T1Magnetic Resonance Imaging at JoVE.com

Synthesis of 68Ga Core-doped Iron Oxide Nanoparticles for Dual Positron Emission Tomography /T1Magnetic Resonance Imaging

Here, we present a protocol to obtain 68Ga core-doped iron oxide nanoparticles via fast microwave-driven synthesis. The methodology renders PET/(T1)MRI nanoparticles with radiolabeling efficiencies higher than 90% and radiochemical purity of 99% in a 20-min synthesis.

Synthesis of 68Ga Core-doped Iron Oxide Nanoparticles for Dual Positron Emission Tomography /(T1)Magnetic Resonance Imaging

Here, we describe a microwave synthesis to obtain iron oxide nanoparticles core-doped with 68Ga. Microwave technology enables fast and reproducible ...

This method provides some fascinating synthesis of gallium-68 core-doped nanoparticles for hybrid PET/MR molecular imaging. The main advantage of this technique is that thanks to the use of microwave technology, the synthesis is fast and more importantly, completely reproducible. First, dissolve 75 milligrams of iron chloride hexahydrate and 80 milligrams of citric acid trisodium salt dihydrate in nine milliliters of water.Transfer the mixture to a microwave-adapted flask. Next, load a dynamic protocol in the microwave. Set the temperature to 120 degrees Celsius, the time to 10 minutes, the pressure to 250 psi, and the power to 240 watts.Add one milliliter of hydrazine hydrate to the reaction mixture. Then start the microwave protocol. In the meantime, rinse a gel filtration desalting column with 20 milliliters of distilled water.Once the protocol is finished, and the flask cooled to room temperature, pipette 2.5 milliliters of the final mixture onto the column and discard the flowthrough. Following this, add three milliliters of distilled water to the column and collect the nanoparticles in a plastic tube. Add 75 milligrams of iron chloride hexahydrate and 80 milligrams of citric acid trisodium salt dihydrate into a vial.Elute the gallium-68 generator using the recommended volume and concentration of hydrochloric acid according to the vendor. After the hydrochloric acid injection in the self-shielded generator, four milliliters of gallium-68 chloride is obtained, ready to use without further processing. Add four milliliters of gallium-68 chloride to the microwave-adapted flask.Then pipette five milliliters of distilled water into the flask and mix well. Now load a dynamic protocol in the microwave. Set the temperature to 120 degrees Celsius, the time to 10 minutes, the pressure to 250 psi, and the power to 240 watts.Add one milliliter of hydrazine hydrate to the reaction mixture. Then start the microwave protocol. In the meantime, rinse a gel filtration desalting column with 20 milliliters of distilled water.Once the protocol is finished and the flask cooled to room temperature, pipette 2.5 milliliters of the final mixture onto the column and discard the flowthrough. Then add three milliliters of distilled water to the column and collect the nanoparticles in a glass vial. To measure the hydrodynamic size of the gallium-68 nanoparticles, pipette 60 microliters of the sample into a cuvette and perform three dynamic light scattering measurements per sample.To assess the colloidal stability of the gallium-68 nanoparticles, incubate 500 microliters of sample in different buffers at 37 degrees Celsius for different times, ranging from zero to 24 hours. At the selected times, transfer 60 microliter aliquots to cuvettes and measure their hydrodynamic size. To obtain a gel filtration radiochromatogram, fractionate the elution from the size exclusion column into 500 microliter aliquots during the gel filtration purification step.Then measure the radioactivity present in each aliquot using an activimeter. To determine the radiochemical stability, incubate the gallium-68 nanoparticles in mouse serum for 30 minutes at 37 degrees Celsius. After incubation, purify the nanoparticles by ultrafiltration.Then measure the radioactivity present in the nanoparticles and filtrate. Hydrodynamic size data for the gallium-68 nanoparticles revealed a narrow size distribution and mean hydrodynamic size of 7.9 nanometers. Measurements of five different syntheses proved method reproducibility.The hydrodynamic size of gallium-68 nanoparticles incubated in different media from zero to 24 hours showed no significant changes, meaning the sample is stable in different buffers and serums. Because of the fast heating achieved using microwave technology, nanoparticles present ultra small core sizes of about four nanometers. Electron microscopy images revealed homogeneous core sizes and the absence of aggregation.The gallium-68 nanoparticle gel filtration chromatogram shows a main radioactivity peak corresponding to the nanoparticles and a reduced peak corresponding to free gallium-68. The radiolabeling yield was 92%which translates into a specific activity relative to 7.1 gigabecquerel per millimole of iron. An excellent longitudinal value of 11.9 and a modest relaxation value of 22.9 were obtained for five gallium-68 nanoparticle syntheses, yielding an average ratio of 1.9, meaning gallium-68 nanoparticles are ideal for T1-weighted MRI.MR phantom images at different gallium-68 nanoparticle concentrations show an increase in the iron concentration and positive contrast. An increasing iron concentration implies an increasing gallium-68 concentration, and the PET signal is increasingly intense. The use of microwave technology allows for the reproducible and rapid synthesis of iron oxide nanoparticles for multi-modal imaging.Following this procedure, we have produced a tracer that can be used for targeted molecular imaging with PET, T1 MRI, or hybrid approaches. After its development, this technique pave the way for researchers to explore the use of hybrid molecular imaging in fields such as oncology and cardiovascular diseases. Don't forget that working with radioactive compounds can be extremely hazardous, and radioprotection precautions should always be taken while performing this procedure.

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Research

JoVE Journal

Biology

6.4K 조회수.  Centro Nacional de Investigaciones Cardiovasculares Carlos III (CNIC). 이 방법은 하이브리드 PET/MR 분자 이미징을 위한 담륨-68 코어 도핑 나노 입자의 매혹적인 합성을 제공합니다. 이 기술의 주요 장점은 전자 레인지 기술의 사용 덕분에 합성이 빠르고 더 중요한 것은 완전히 재현 할 수 있다는 것입니다. 첫째, 염화물 육수산 염분염 75밀리그램과 구연산 삼나트륨 소금 80밀리그램을 9밀리리터의 물에 녹입니다.혼합물을 전자레인지에 맞게 ...