This work was supported by the European Union (ERC-2014-CoG project MaTissE #648779). The authors would like to acknowledge&#160;the CNanoMat physico-chemical characterizations platform of University Paris 13.

1. Synthesis of magnetic nanoparticles
<ol>
	<li>Core synthesis &#8211; microwave-assisted
	<ol>
		<li>Dissolve 400 mg of iron(III) acetylacetonate (&#62;99.9%) in 10 mL of benzyl alcohol (BA, 99.8%) within a 30 mL monowave glass vial.</li>
		<li>Increase the temperature of the suspension from 25 to 250 &#176;C in 20 min (at a rate of 11.25 &#176;C/min) and maintain it at 250 &#176;C for 30 min using a microwave reactor.</li>
		<li>Transfer the resulting nanoparticles suspended in benzyl alcohol to a glass vial and sep...

<ol>
	<li>Azevedo-Pereira, R. 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=Superparamagnetic+iron+oxide+nanoparticles+as+a+tool+to+track+mouse+neural+stem+cells+in+vivo.">Superparamagnetic iron oxide nanoparticles as a tool to track mouse neural stem cells in vivo.</a> Molecular Biology Reports. 46 (1), 191-198 (2019).</li><li>Fayol, D., Frasca, G., Le Visage, C., Gazeau, F., Luciani, N., Wilhelm, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Use+of+magnetic+forces+to+promote+stem+cell+aggregation+during+differentiation,+and+cartilage+tissue+modeling.">Use of magnetic forces to promote stem cell aggregation during differentiation, and cartilage tissue modeling.</a> Advanced Materials. 25 (18), 2611-2616 (2013).</li><li>Kim, J. 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=High-throughput+generation+of+spheroids+using+magnetic+nanoparticles+for+three-dimensional+cell+culture.">High-throughput generation of spheroids using magnetic nanoparticles for three-dimensional cell culture.</a> Biomaterials. 34 (34), 8555-8563 (2013).</li><li>Yamamoto, 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=Preparation+of+artificial+skeletal+muscle+tissues+by+a+magnetic+force-based+tissue+engineering+technique.">Preparation of artificial skeletal muscle tissues by a magnetic force-based tissue engineering technique.</a> Journal of Bioscience and Bioengineering. 108 (6), 538-543 (2009).</li><li>Gon&#231;alves, A. I., Rodrigues, M. T., Gomes, M. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tissue-engineered+magnetic+cell+sheet+patches+for+advanced+strategies+in+tendon+regeneration.">Tissue-engineered magnetic cell sheet patches for advanced strategies in tendon regeneration.</a> Acta Biomaterialia. 63, 110-122 (2017).</li><li>Du, 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=A+3D+magnetic+tissue+stretcher+for+remote+mechanical+control+of+embryonic+stem+cell+differentiation.">A 3D magnetic tissue stretcher for remote mechanical control of embryonic stem cell differentiation.</a> Nature Communications. 8 (1), 400 (2017).</li><li>Amiri, M., Salavati-Niasari, M., Pardakhty, A., Ahmadi, M., Akbari, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Caffeine:+A+novel+green+precursor+for+synthesis+of+magnetic+CoFe2O4+nanoparticles+and+pH-sensitive+magnetic+alginate+beads+for+drug+delivery.">Caffeine: A novel green precursor for synthesis of magnetic CoFe2O4 nanoparticles and pH-sensitive magnetic alginate beads for drug delivery.</a> Materials Science and Engineering: C. 76, 1085-1093 (2017).</li><li>Vangijzegem, T., Stanicki, D., Laurent, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Magnetic+iron+oxide+nanoparticles+for+drug+delivery:+applications+and+characteristics.">Magnetic iron oxide nanoparticles for drug delivery: applications and characteristics.</a> Expert Opinion on Drug Delivery. 16 (1), 69-78 (2019).</li><li>Cazares-Cortes, 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=Recent+insights+in+magnetic+hyperthermia:+From+the+"hot-spot"+effect+for+local+delivery+to+combined+magneto-photo-thermia+using+magneto-plasmonic+hybrids.">Recent insights in magnetic hyperthermia: From the "hot-spot" effect for local delivery to combined magneto-photo-thermia using magneto-plasmonic hybrids.</a> Advanced Drug Delivery Reviews. 138, 233-246 (2019).</li><li>Espinosa, 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=Magnetic+(Hyper)Thermia+or+Photothermia?+Progressive+Comparison+of+Iron+Oxide+and+Gold+Nanoparticles+Heating+in+Water,+in+Cells,+and+in+vivo.">Magnetic (Hyper)Thermia or Photothermia? Progressive Comparison of Iron Oxide and Gold Nanoparticles Heating in Water, in Cells, and in vivo.</a> Advanced Functional Materials. 28 (37), 1803660 (2018).</li><li>Plan Sangnier, 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=Targeted+thermal+therapy+with+genetically+engineered+magnetite+magnetosomes@RGD:+Photothermia+is+far+more+efficient+than+magnetic+hyperthermia.">Targeted thermal therapy with genetically engineered magnetite magnetosomes@RGD: Photothermia is far more efficient than magnetic hyperthermia.</a> Journal of Controlled Release. 279, 271-281 (2018).</li><li>Pham, B. T. T., 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=Biodistribution+and+Clearance+of+Stable+Superparamagnetic+Maghemite+Iron+Oxide+Nanoparticles+in+Mice+Following+Intraperitoneal+Administration.">Biodistribution and Clearance of Stable Superparamagnetic Maghemite Iron Oxide Nanoparticles in Mice Following Intraperitoneal Administration.</a> International Journal of Molecular Sciences. 19 (1), (2018).</li><li>Kolosnjaj-Tabi, 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=Biotransformations+of+magnetic+nanoparticles+in+the+body.">Biotransformations of magnetic nanoparticles in the body.</a> Nano Today. 11 (3), 280-284 (2016).</li><li>Bargheer, 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+distribution+and+degradation+of+radiolabeled+superparamagnetic+iron+oxide+nanoparticles+and+quantum+dots+in+mice.">The distribution and degradation of radiolabeled superparamagnetic iron oxide nanoparticles and quantum dots in mice.</a> Beilstein Journal of Nanotechnology. 6, 111-123 (2015).</li><li>Freund, 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=A+simple+and+widely+applicable+method+to+59Fe-radiolabel+monodisperse+superparamagnetic+iron+oxide+nanoparticles+for+in+vivo+quantification+studies.">A simple and widely applicable method to 59Fe-radiolabel monodisperse superparamagnetic iron oxide nanoparticles for in vivo quantification studies.</a> ACS Nano. 6 (8), 7318-7325 (2012).</li><li>Singh, S. P., Rahman, M. F., Murty, U. S. N., Mahboob, M., Grover, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparative+study+of+genotoxicity+and+tissue+distribution+of+nano+and+micron+sized+iron+oxide+in+rats+after+acute+oral+treatment.">Comparative study of genotoxicity and tissue distribution of nano and micron sized iron oxide in rats after acute oral treatment.</a> Toxicology and Applied Pharmacology. 266 (1), 56-66 (2013).</li><li>Levy, 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=Long+term+in+vivo+biotransformation+of+iron+oxide+nanoparticles.">Long term in vivo biotransformation of iron oxide nanoparticles.</a> Biomaterials. 32 (16), 3988-3999 (2011).</li><li>Briley-Saebo, 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=Hepatic+cellular+distribution+and+degradation+of+iron+oxide+nanoparticles+following+single+intravenous+injection+in+rats:+implications+for+magnetic+resonance+imaging.">Hepatic cellular distribution and degradation of iron oxide nanoparticles following single intravenous injection in rats: implications for magnetic resonance imaging.</a> Cell and Tissue Research. 316 (3), 315-323 (2004).</li><li>Gu, L., Fang, R. H., Sailor, M. J., Park, J. H. <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+Clearance+and+Toxicity+of+Monodisperse+Iron+Oxide+Nanocrystals.">In vivo Clearance and Toxicity of Monodisperse Iron Oxide Nanocrystals.</a> ACS Nano. 6 (6), 4947-4954 (2012).</li><li>Sangnier, 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=Impact+of+magnetic+nanoparticle+surface+coating+on+their+long-term+intracellular+biodegradation+in+stem+cells.">Impact of magnetic nanoparticle surface coating on their long-term intracellular biodegradation in stem cells.</a> Nanoscale. , (2019).</li><li>Mazuel, 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=Magneto-Thermal+Metrics+Can+Mirror+the+Long-Term+Intracellular+Fate+of+Magneto-Plasmonic+Nanohybrids+and+Reveal+the+Remarkable+Shielding+Effect+of+Gold.">Magneto-Thermal Metrics Can Mirror the Long-Term Intracellular Fate of Magneto-Plasmonic Nanohybrids and Reveal the Remarkable Shielding Effect of Gold.</a> Advanced Functional Materials. 27 (9), 1605997 (2017).</li><li>Van de Walle, 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=Biosynthesis+of+magnetic+nanoparticles+from+nano-degradation+products+revealed+in+human+stem+cells.">Biosynthesis of magnetic nanoparticles from nano-degradation products revealed in human stem cells.</a> Proceedings of the National Academy of Sciences of the United States of America. 116 (10), 4044-4053 (2019).</li><li>Mazuel, 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=Massive+Intracellular+Biodegradation+of+Iron+Oxide+Nanoparticles+Evidenced+Magnetically+at+Single-Endosome+and+Tissue+Levels.">Massive Intracellular Biodegradation of Iron Oxide Nanoparticles Evidenced Magnetically at Single-Endosome and Tissue Levels.</a> ACS Nano. 10 (8), 7627-7638 (2016).</li><li>Bee, A., Massart, R., Neveu, S. <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+very+fine+maghemite+particles.">Synthesis of very fine maghemite particles.</a> Journal of Magnetism and Magnetic Materials. 149 (1), 6-9 (1995).</li><li>Feldmann, C., Jungk, H. O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Polyol-Mediated+Preparation+of+Nanoscale+Oxide+Particles.">Polyol-Mediated Preparation of Nanoscale Oxide Particles.</a> Angewandte Chemie International Edition. 40 (2), 359-362 (2001).</li><li>Hyeon, T., Lee, S. S., Park, J., Chung, Y., Na, H. B. <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+Highly+Crystalline+and+Monodisperse+Maghemite+Nanocrystallites+without+a+Size-Selection+Process.">Synthesis of Highly Crystalline and Monodisperse Maghemite Nanocrystallites without a Size-Selection Process.</a> Journal of the American Chemical Society. 123 (51), 12798-12801 (2001).</li><li>Pinna, N., Grancharov, S., Beato, P., Bonville, P., Antonietti, M., Niederberger, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Magnetite+Nanocrystals:+Nonaqueous+Synthesis,+Characterization,+and+Solubility.">Magnetite Nanocrystals: Nonaqueous Synthesis, Characterization, and Solubility.</a> Chemistry of Materials. 17 (11), 3044-3049 (2005).</li><li>Richard, 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=USPIO+size+control+through+microwave+nonaqueous+sol-gel+method+for+neoangiogenesis+T2+MRI+contrast+agent.">USPIO size control through microwave nonaqueous sol-gel method for neoangiogenesis T2 MRI contrast agent.</a> Nanomedicine. 11 (21), 2769-2797 (2016).</li><li>Ngo, A. T., Pileni, M. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Assemblies+of+Ferrite+Nanocrystals:+Partial+Orientation+of+the+Easy+Magnetic+Axes.">Assemblies of Ferrite Nanocrystals: Partial Orientation of the Easy Magnetic Axes.</a> The Journal of Physical Chemistry B. 105 (1), 53-58 (2001).</li><li>Li, 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=Effect+of+synthesis+conditions+on+the+properties+of+citric-acid+coated+iron+oxide+nanoparticles.">Effect of synthesis conditions on the properties of citric-acid coated iron oxide nanoparticles.</a> Microelectronic Engineering. 110, 329-334 (2013).</li><li>Sun, X., 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=Tracking+stem+cells+and+macrophages+with+gold+and+iron+oxide+nanoparticles+-+The+choice+of+the+best+suited+particles.">Tracking stem cells and macrophages with gold and iron oxide nanoparticles - The choice of the best suited particles.</a> Applied Materials Today. 15, 267-279 (2019).</li><li>Buchner, M., H&#246;fler, K., Henne, B., Ney, V., Ney, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tutorial:+Basic+principles,+limits+of+detection,+and+pitfalls+of+highly+sensitive+SQUID+magnetometry+for+nanomagnetism+and+spintronics.">Tutorial: Basic principles, limits of detection, and pitfalls of highly sensitive SQUID magnetometry for nanomagnetism and spintronics.</a> Journal of Applied Physics. 124 (16), 161101 (2018).</li><li>Wilhelm, C., Gazeau, F., Bacri, J. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Magnetophoresis+and+ferromagnetic+resonance+of+magnetically+labeled+cells.">Magnetophoresis and ferromagnetic resonance of magnetically labeled cells.</a> European Biophysics Journal. 31 (2), 118-125 (2002).</li><li>Jing, 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=Quantitative+intracellular+magnetic+nanoparticle+uptake+measured+by+live+cell+magnetophoresis.">Quantitative intracellular magnetic nanoparticle uptake measured by live cell magnetophoresis.</a> The FASEB Journal. 22 (12), 4239-4247 (2008).</li><li>Van de Walle, 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=Real-time+in+situ+magnetic+measurement+of+the+intracellular+biodegradation+of+iron+oxide+nanoparticles+in+a+stem+cell-spheroid+tissue+model.">Real-time in situ magnetic measurement of the intracellular biodegradation of iron oxide nanoparticles in a stem cell-spheroid tissue model.</a> Nano Research. , (2020).</li></ol>

The authors have nothing to disclose.

Using a fast and efficient microwave-based synthesis, magnetic nanoparticles can easily be synthesized, with controlled size, and further coated with given molecules. A critical step is to stock the iron salt and the benzyl alcohol under vacuum to keep a small dispersion in size. The benzyl alcohol acts as both as solvent and ligand at the same time allowing to directly obtain calibrated bare iron oxide without the need of additional ligands. After nanoparticles transfer in water the bare magnetic nanoparticles can be ea...

There is increased interest in the magnetic features of iron oxide nanoparticles for a wide range of biomedical applications. Their response to magnetic resonance makes them reliable contrast agents for magnetic resonance imaging (MRI), an advantage in regenerative medicine where cells labeled with magnetic nanoparticles can be tracked in vivo following implantation1. Using magnetic fields, cells can also be guided at a distance; this way, cellular spheroids2,3, rings4, or sheets5 can be engineered magnetically and also remotely stimulated6, an asset in the development of scaffold-free tissues. The range of possibilities for these nanoparticles also includes drug delivery systems7,8 and magnetic and photoinduced hyperthermal treatment to kill cancerous cells9,10,11. For all these applications, the nanoparticles are integrated in the biological environment either by intravenous injection or via direct internalization in cells and are then left within, which brings into question their intracellular fate.
In vivo analyses conveyed a general understanding of the nanoparticles&#8217; fate in the organism: upon injection in the blood stream, they are first captured mostly by the macrophages of the liver (Kupffer cells), spleen and bone marrow, are progressively degraded, and join the iron pool of the organism12,13,14,15,16,17,18,19. Qualitative observations are only possible due to the circulation of the nanoparticles throughout the organism. Typically, transmission electronic microscopy (TEM) can be used to directly observe the nanoparticles and the presence of iron in the organs can be determined via dosage. More recently, their fate has been assessed directly on a pool of cells, meaning in close circuit with no iron escape, allowing a quantitative measurement of their biotransformations at the cell-level20,21,22. Such measurements are possible via the analysis of the magnetic properties of the nanoparticles that are tightly linked to their structural integrity. Vibrating sample magnetometry (VSM) is a technique where the sample is vibrated periodically so that the coil-measurement of the flux induced provides the magnetic moment of the sample at the applied magnetic field. Such synchronous detection allows for a rapid measurement, which is an asset for determining the magnetic moments of a large number of samples20,21,22,23. The macroscopic magnetic signature retrieved by VSM then gives a quantitative overview of the entire biological sample directly correlated to the nanoparticles&#39; size and structure. In particular, it provides the magnetic moment at saturation (expressed in emu) of the samples, which is a direct quantification of the number of magnetic nanoparticles present in the sample, respectively to their specific magnetic properties.
It has been shown that the intracellular processing of magnetic nanoparticles is tightly linked to their structural features20. These features can be controlled via optimal synthesis protocols. Each protocol presents advantages and limitations. Iron oxide nanoparticles are commonly synthesized in aqueous solutions via coprecipitation of iron ions24. To overcome the limitations of nanoparticles size polydispersity, other synthesis methods such as polyol-mediated sol-gel methods have been developed25. Nonaqueous approaches by thermal decomposition leads to the production of very well-calibrated iron oxide nanoparticles26. However, the use of massive amounts of surfactants like oleylamine or oleic acid complicates their functionalization and water transfer for biomedical applications. For this reason, we synthesize such magnetic nanoparticles through a nonaqueous sol gel route leading to high crystallinity, purity and reproducibility27. This protocol produces well-controlled size nanoparticles that can be tuned through temperature variation28. Nevertheless, the microwave-assisted non-aqueous sol-gel route has an upper size limit of the obtained nanoparticles of around 12 nm. This procedure would not be adapted for applications using ferromagnetic particles at room temperature. In addition to the core synthesis, another main feature to be considered is the coating. Lying at the surface of the nanoparticle, the coating acts as an anchoring molecule, helping the targeted internalization of the nanoparticles, or it can protect the nanoparticle from degradation. Since benzyl alcohol acts as an oxygen source and a ligand at the same time, bare nanoparticles are produced without the need for additional surfactants or ligands. The nanoparticles are then easily surface functionalized after synthesis without a surfactant exchange process.
Herein, two types of nanoparticles are assessed that possess the same core and differ in the coating. The core is synthesized using a fast and highly efficient microwave based technique. The two coatings compared consist of citric acid, one of the most used as coating agent in biomedical applications29,30, and polyacrylic acid (PAA), a polymeric coating with a high number of chelating functions. VSM magnetometry measurements are then used first to quantify the nanoparticle uptake by the cells, and then as a direct assessment of the nanoparticle structural integrity upon internalization in stem cells. Results demonstrate that the incubation concentration impacts nanoparticle uptake and that the coating influences their degradation, with the large number of anchoring molecules of PAA protecting the core from degradation.

<table>
	<tbody>
		<tr>
			<td>0.05% Trypsin-EDTA (1x)</td>
			<td>Life Technologies</td>
			<td>25300-054</td>
			<td></td>
		</tr>
		<tr>
			<td>Benzyl alcohol for synthesis</td>
			<td>Sigma Aldrich</td>
			<td>8.22259</td>
			<td></td>
		</tr>
		<tr>
			<td>Dexamethasone</td>
			<td>Sigma</td>
			<td>D4902</td>
			<td>Prepare a 1 mM stock solution diluted in Ethanol 100% and store at -20&#176;C</td>
		</tr>
		<tr>
			<td>Dichloromethane &#8805;99% stabilised, GPR RECTAPUR</td>
			<td>VWR Chemicals</td>
			<td>23367</td>
			<td></td>
		</tr>
		<tr>
			<td>DMEM with Glutamax I</td>
			<td>Life Technologies</td>
			<td>31966-021</td>
			<td>No sodium pyruvate, no HEPES</td>
		</tr>
		<tr>
			<td>Ethanol absolute</td>
			<td>VWR</td>
			<td>20821.310</td>
			<td></td>
		</tr>
		<tr>
			<td>Fetal Bovine Serum</td>
			<td>Life Technologies</td>
			<td>10270-106</td>
			<td></td>
		</tr>
		<tr>
			<td>Formalin solution 10% neutral buffered</td>
			<td>Sigma</td>
			<td>HT5012</td>
			<td></td>
		</tr>
		<tr>
			<td>Hydrochloric acid, 1.0N Standardized Solution</td>
			<td>Alfa Aesar</td>
			<td>35640</td>
			<td></td>
		</tr>
		<tr>
			<td>Iron(III) acetylacetonate (&#62; 99.9%)</td>
			<td>Sigma Aldrich</td>
			<td>517003</td>
			<td></td>
		</tr>
		<tr>
			<td>ITS Premix Universal Culture Supplement (20x)</td>
			<td>Corning</td>
			<td>354352</td>
			<td></td>
		</tr>
		<tr>
			<td>L-Ascorbic Acid 2-phosphate</td>
			<td>Sigma</td>
			<td>A8960</td>
			<td>Prepare a fresh concentrated solution (25 mM) diluted in distilled water</td>
		</tr>
		<tr>
			<td>L-Proline</td>
			<td>Sigma</td>
			<td>P5607</td>
			<td>Prepare a 175 mM stock solution diluted in distilled water and store at 4&#176;C</td>
		</tr>
		<tr>
			<td>Mesenchymal Stem Cell (MSC)</td>
			<td>Lonza</td>
			<td>PT-2501</td>
			<td></td>
		</tr>
		<tr>
			<td>Monowave glass vial</td>
			<td>Anton Paar</td>
			<td>82723_us</td>
			<td></td>
		</tr>
		<tr>
			<td>Microwave reactor</td>
			<td>Anton Paar</td>
			<td>Monowave 300</td>
			<td></td>
		</tr>
		<tr>
			<td>MSCGM BulletKit medium</td>
			<td>Lonza</td>
			<td>PT-3001</td>
			<td>For the complete medium, add the provided BulletKit (containing serum, glutamine and antibiotics) to the MSCGM medium</td>
		</tr>
		<tr>
			<td>PBS w/o CaCl2 w/o MgCl2</td>
			<td>Life Technologies</td>
			<td>14190-094</td>
			<td></td>
		</tr>
		<tr>
			<td>Penicillin (10.000U/mL)/Streptomicin (10.000&#181;g/mL)</td>
			<td>Life Technologies</td>
			<td>15140-122</td>
			<td></td>
		</tr>
		<tr>
			<td>Poly(acrylic acid, sodium salt)</td>
			<td>Sigma Aldrich</td>
			<td>416010</td>
			<td>MW = 1200 g/mol</td>
		</tr>
		<tr>
			<td>RPMI medium 1640, no Glutamine</td>
			<td>Life Technologies</td>
			<td>31870-025</td>
			<td>No sodium pyruvate, no HEPES</td>
		</tr>
		<tr>
			<td>Sodium hydroxide, 1.0N Standardized Solution</td>
			<td>Alfa Aesar</td>
			<td>35629</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium pyruvate solution 100mM</td>
			<td>Sigma</td>
			<td>S8636</td>
			<td></td>
		</tr>
		<tr>
			<td>Sterile conical centrifuge tube</td>
			<td>Falcon</td>
			<td>352097</td>
			<td>15 mL tubes</td>
		</tr>
		<tr>
			<td>Trypsin-EDTA (0.05%), phenol red</td>
			<td>Thermo Fisher Scientific</td>
			<td>25300054</td>
			<td></td>
		</tr>
		<tr>
			<td>Tri-sodium citrate</td>
			<td>VWR</td>
			<td>33615.268</td>
			<td>Prepare a 1 M stock solution diluted in distilled water and store at 4&#176;C</td>
		</tr>
		<tr>
			<td>Tri-Sodium Citrate Dihydrate, Certified AR for Analysis</td>
			<td>Sigma Aldrich</td>
			<td>10396430</td>
			<td></td>
		</tr>
		<tr>
			<td>Ultra centrifugal filter</td>
			<td>Amicon</td>
			<td>AC S510024</td>
			<td></td>
		</tr>
	</tbody>
</table>

using magnetometry to monitor cellular incorporation and subsequent biodegradation of chemically synthetized iron oxide nanoparticles

Magnetic nanoparticles, made of iron oxide, present a peculiar interest for a wide range of biomedical applications for which they are often internalized in cells and then left within. One challenge is to assess their fate in the intracellular environment with reliable and precise methodologies. Herein, we introduce the use of the vibrating sample magnetometer (VSM) to precisely quantify the integrity of magnetic nanoparticles within cells by measuring their magnetic moment. Stem cells are first labeled with two types of magnetic nanoparticles; the nanoparticles have the same core produced via a fast and efficient microwave-based nonaqueous sol gel synthesis and differ in their coating: the commonly used citric acid molecule is compared to polyacrylic acid. The formation of 3D cell-spheroids is then achieved via centrifugation and the magnetic moment of these spheroids is measured at different times with the VSM. The obtained moment is a direct fingerprint of the nanoparticles&#8217; integrity, with decreasing values indicative of a nanoparticle degradation. For both nanoparticles, the magnetic moment decreases over culture time revealing their biodegradation. A protective effect of the polyacrylic acid coating is also shown, when compared to citric acid.

Using the microwave-assisted synthesis, magnetic nanoparticles with a monodisperse 8.8 &#177; 2.5 nm core size are produced and coated with either citrate or PAA (Figure 1A). Stem cells are then incubated with these nanoparticles dispersed in culture medium at a given concentration for 30 minutes, resulting in their endocytosis and confinement within the cellular endosomes (Figure 1B). The magnetic stem cells are then suspended in medium, centrifuged, and the ce...

Watch this Scientific Journal Video about Using Magnetometry to Monitor Cellular Incorporation and Subsequent Biodegradation of Chemically Synthetized Iron Oxide Nanoparticles at JoVE.com

Using Magnetometry to Monitor Cellular Incorporation and Subsequent Biodegradation of Chemically Synthetized Iron Oxide Nanoparticles

Iron oxide nanoparticles are synthesized via a nonaqueous sol gel procedure and coated with anionic short molecules or polymer. The use of magnetometry for monitoring the incorporation and biotransformations of magnetic nanoparticles inside human stem cells is demonstrated using a vibrating sample magnetometer (VSM).

Magnetic nanoparticles, made of iron oxide, present a peculiar interest for a wide range of biomedical applications for which they are often internalized ...

This video introduces a fast and efficient method for the synthesis of magnetic nanoparticles and the use of magnetometry to photograph transformation in the biological environment. Magnetic nanoparticles have attracted increased attention for biomedical applications, And it is important to understand that fate once internalized in cells. This is achieved here by measuring the cellular magnetism.For both magnetic nanoparticles synthesis and measurements, result could be affected by contamination. Use well-cleaned chemical vials and make sure that the magnetometer equipment is free of contamination. The magnetometry samples holder is usually used for powder samples.We show how to adapt the use of the holder to liquid or biological samples. In a 30 milliliter mana wave glass vial dissolve 400 milligrams of iron three acetylacetonate in 10 milliliters of benzyl alcohol. Using a microwave reactor, heat the suspension from 25 degrees Celsius to 250 degrees Celsius at a rate of 11.25 degrees Celsius per minute, and maintain it at 250 degrees Celsius.To separate the nanoparticles, apply a neodymium magnet for 30 minutes. To pellet the nanoparticles, perform a series of washes using 10 milliliters of the designated wash fluid and applying a neodymium magnet for five minutes. Remove the filtrate and add 12 milliliters of 10 to the minus two molar hydrochloric acid.Centrifuge the suspension and a 100 kilodalton filter at 2, 200 times G for 10 minutes. Then resuspend the nanoparticles in 10 milliliters of 10 to the minus two molar hydrochloric acid. Prepare the coating molecule solution as described in the manuscript.Add the 10 milliliter nanoparticle aqueous dispersion to the coating molecule solution at a mass ratio of five to one between the coating molecules and the nanoparticles. Then agitate the mixture for two hours at room temperature using a magnetic stirrer. After the reaction is complete, adjust the pH of the mixture to seven using one molar sodium hydroxide.When the culture of human mesenchymal stem cells are at passage five and 90%confluent, remove the medium and rinse the cells with serum-free RPMI without glutamine. To each 150 square centimeter culture flask, add 10 milliliters of the nanoparticle suspension. Incubate the flasks at 37 degrees Celsius and 5%carbon dioxide for 30 minutes.Then discard the medium containing the nanoparticle suspension and wash the cells once with serum-free RPMI 1640. Add DMEM supplemented with 10%FBS and 1%penicillin streptomycin. Incubate overnight at 37 degrees Celsius and 5%carbon dioxide to allow complete internalization of the nanoparticles.Add 10 milliliters of 0.05%trypsin EDTA prewarmed for 37 degrees Celsius to each flask of magnetically labeled MSCs. After two to three minutes, when the cells are detached, immediately inactivate the trypsin by adding one third of the volume of pre-warned supplemented DMEM. Centrifuge the detached cells at 260 times G for five minutes.Aspirate the medium and resuspend the cells in a small volume of cell-spheroid culture medium at a concentration of approximately 200, 000 cells per 50 microliters. Add one milliliter of freshly prepared cell-spheroid culture medium to a 15 milliliter sterile conical centrifuge tube. Then add a volume of cell suspension corresponding to 200, 000 cells.Centrifuge these magnetically labeled cells at 180 times G for three minutes in order to form a cell pellet at the bottom of the tube. Then place the tube in the incubator at 37 degrees Celsius and 5%carbon dioxide, keeping the cap slightly opened for gas exchange. Place either a given volume of magnetic nanoparticle or a fixed single cell-spheroid suspension into the vibrating sample magnetometer, or VSM, sample holder.If necessary, PTFE tape can be used to prevent any leakage. Insert the sample holder into the VSM and scan for sample offset. Place the sample at the position corresponding to the magnetization maximum.Perform the first measurement at a low magnetic field between negative 1, 500 Oersteds and positive 1, 500 Oersteds at a rate of 20 Oersteds per second. Perform a second measurement at a high magnetic field between zero Oersteds and positive 30, 000 Oersteds at a rate of 200 Oersteds per second. 10 microliters of nanoparticles dispersed in an aqueous solution were measured in the vibrating sample magnetometer.The slope of the second part of the curve is the diamagnetic constant, representing the diamagnetic signal from the water and the sample holder. This diamagnetic constant was subtracted from the magnetic moment of the solution to obtain the magnetic moment of the nanoparticles only. The magnetic moment at saturation was then determined.Coated nanoparticles were internalized in stem cells. Electron microscope images show the citrate-coated and PAA-coated nanoparticles confined in the endosomes. After the cells were pelleted by centrifugation, they formed a cell-spheroid that can be kept in culture for extended time periods.Individual cell-spheroids were also measured using the VSM and the saturation magnetic moment was used to calculate the quantity of nanoparticles in a cellular sample. Uptake of the nanoparticles was found to depend on their incubation concentration. A decrease in magnetism of the cell-spheroids over time indicated the biodegradation of the nanoparticles, which was confirmed by electron microscopy.Degradation was more substantial in the citrate-coated nanoparticles than in the PAA-coated nanoparticles. Using magnetometry, the degradation of magnetic nanoparticles within cells can be precisely quantified, and the impact of the futures of nanoparticles on the interested in raw behavior can be assessed. In this protocol, the magnetometry measurements were performed on cell-spheroids, but they can be extended to cells into suspension or to organs.With the described method, you are able to explore the interactions of newly designed magnetic nanoparticles in different cell system of interest, but also you can follow their in vivo biodistribution and fate.

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Research

JoVE Journal

Bioengineering

4.1K visualizações.  Complexes MSC, UMR 7057, CNRS & University Paris Diderot. Este vídeo introduz um método rápido e eficiente para a síntese de nanopartículas magnéticas e o uso da magnetometria para fotografar a transformação no ambiente biológico. As nanopartículas magnéticas têm atraído maior atenção para aplicações biomédicas, e é importante entender que o destino uma vez internalizado nas células. Isso é conseguido aqui medindo o magnetismo celular.Tanto para as nanopartículas magnéticas quanto para as medidas, o resultado pode ser a...