Name: in situ detection and single cell quantification of metal oxide nanoparticles using nuclear microprobe analysis
Uploaded: 2018-02-03T13:00:00
Description: Watch this Scientific Journal Video about In Situ Detection and Single Cell Quantification of Metal Oxide Nanoparticles Using Nuclear Microprobe Analysis at JoVE.com

We thank Serge Borderes for directing and editing of the video. The French National Research Agency supports the research program TITANIUMS (ANR CES 2010, n&#176; CESA 009 01). The CNRS and the European Community as an Integrating activity provided the "Support of Public and Industrial Research Using Ion Beam Technology (SPIRIT)" under the EC contract n&#176; 227012. This work has been supported by Marie Curie Actions - Initial Training Networks (ITN) as an "Integrating Activity Supporting Postgraduate Research with Internships in Industry and Training Excellence" (SPRITE, D1.3) under EC contract no. 317169. The C'NANO Grand Sud Ouest and the Region Aquitaine support the research program TOX-NANO (n&#176;20111201003) and the research program POPRA (n&#176; 14006636-034).

1. Sample Holder Preparation
<ol>
	<li>Sample holder design and preparation
	<ol>
		<li>Manufacture a sample holder by drilling a 5 mm x 5 mm square in a 1-mm thick PEEK frame.</li>
		<li>Clean by rinsing with ethanol 70% (v/v) and keep in sterile plates until ready to use. 
		Note. A sample holder appropriate for cell culture and cell handling is required. It needs to be designed for cell culturing, in vitro observations with optical microscopy, and nuclear microprobe analysis and imagin...

<ol>
	<li>Krug, H. F., Wick, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nanotoxicology:+An+Interdisciplinary+Challenge.">Nanotoxicology: An Interdisciplinary Challenge.</a> Angew. Chem. Int. Ed. 50 (6), 1260-1278 (2011).</li><li>Van Hove, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=From+surface+science+to+nanotechnology.">From surface science to nanotechnology.</a> Catalysis Today. 113 (3-4), 133-140 (2006).</li><li>Le Trequesser, Q., Seznec, H., Delville, M. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Functionalized+nanomaterials:+their+use+as+contrast+agents+in+bioimaging:+mono-+and+multimodal+approaches.">Functionalized nanomaterials: their use as contrast agents in bioimaging: mono- and multimodal approaches.</a> Nanotox. Rev. 2 (2), 125-169 (2013).</li><li>Oberdorster, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Safety+assessment+for+nanotechnology+and+nanomedicine:+concepts+of+nanotoxicology.">Safety assessment for nanotechnology and nanomedicine: concepts of nanotoxicology.</a> J. Int. Med. , 89-105 (2009).</li><li>Savolainen, 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=Nanotechnologies,+engineered+nanomaterials+and+occupational+health+and+safety+-+A+review.">Nanotechnologies, engineered nanomaterials and occupational health and safety - A review.</a> Saf. Sci. 48 (8), 957-963 (2010).</li><li>Savolainen, K., Alenius, H., Norppa, H., Pylkkanen, L., Tuomi, T., Kasper, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Risk+assessment+of+engineered+nanomaterials+and+nanotechnologies+-+A+review.">Risk assessment of engineered nanomaterials and nanotechnologies - A review.</a> Toxicol. 269 (2-3), 92-104 (2010).</li><li>Arora, S., Rajwade, J. M., Paknikar, K. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nanotoxicology+and+in+vitro+studies:+The+need+of+the+hour.">Nanotoxicology and in vitro studies: The need of the hour.</a> Toxicol. . Appl. Pharm. 258 (2), 151-165 (2012).</li><li>Donaldson, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Resolving+the+nanoparticles+paradox.">Resolving the nanoparticles paradox.</a> Future Med. 1 (2), 229-234 (2006).</li><li>Schaumann, G. 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=Understanding+the+fate+and+biological+effects+of+Ag-+and+TiO2-nanoparticles+in+the+environment:+The+quest+for+advanced+analytics+and+interdisciplinary+concepts.">Understanding the fate and biological effects of Ag- and TiO2-nanoparticles in the environment: The quest for advanced analytics and interdisciplinary concepts.</a> Sci Total Environ. 535, 3-19 (2014).</li><li>Olesik, J. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Inductively Coupled Plasma Mass Spectrometers. Treatise on Geochemistry. , (2014).</li><li>Krystek, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+review+on+approaches+to+bio-distribution+studies+about+gold+and+silver+engineered+nanoparticles+by+inductively+coupled+plasma+mass+spectrometry.">A review on approaches to bio-distribution studies about gold and silver engineered nanoparticles by inductively coupled plasma mass spectrometry.</a> Microchem. J. 105 (November 2011), 39-43 (2012).</li><li>Le Trequesser, Q., 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=Multimodal+correlative+microscopy+for+in+situ+detection+and+quantification+of+chemical+elements+in+biological+specimens.+Applications+to+nanotoxicology.">Multimodal correlative microscopy for in situ detection and quantification of chemical elements in biological specimens. Applications to nanotoxicology.</a> J .Chem. Biol. 8 (4), 159-167 (2015).</li><li>Le Trequesser, Q., 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=Single+cell+in+situ+detection+and+quantification+of+metal+oxide+nanoparticles+using+multimodal+correlative+microscopy.">Single cell in situ detection and quantification of metal oxide nanoparticles using multimodal correlative microscopy.</a> Anal. Chem. 86 (15), 7311-7319 (2014).</li><li>Ackermann, C. M., Lee, S., Chang, C. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analytical+Methods+for+Imaging+Metals+in+Biology:+From+Transition+Metal+Metabolism+to+Transition+Metal+Signaling.">Analytical Methods for Imaging Metals in Biology: From Transition Metal Metabolism to Transition Metal Signaling.</a> Anal. Chem. 89 (1), 22-41 (2017).</li><li>Legin, A. 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=NanoSIMS+combined+with+fluorescence+microscopy+as+a+tool+for+subcellular+imaging+of+isotopically+labeled+platinum-based+anticancer+drugs.">NanoSIMS combined with fluorescence microscopy as a tool for subcellular imaging of isotopically labeled platinum-based anticancer drugs.</a> Chem. Sci. 5, 3135 (2014).</li><li>Lanni, E. J., Rubakhin, S. S., Sweedler, J. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mass+spectrometry+imaging+and+profiling+of+single+cells.">Mass spectrometry imaging and profiling of single cells.</a> J. Proteomics. 75 (16), 5036-5051 (2012).</li><li>Waypa, G. 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=Hypoxia+triggers+subcellular+compartmental+redox+signaling+in+vascular+smooth+muscle+cells.">Hypoxia triggers subcellular compartmental redox signaling in vascular smooth muscle cells.</a> Circ. Res. 106 (3), 526-535 (2010).</li><li>Dooley, C. 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=Imaging+Dynamic+Redox+Changes+in+Mammalian+Cells+with+Green+Fluorescent+Protein+Indicators.">Imaging Dynamic Redox Changes in Mammalian Cells with Green Fluorescent Protein Indicators.</a> J. Biol. Chem. 279 (21), 22284-22293 (2004).</li><li>Hanson, G. 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=Investigating+Mitochondrial+Redox+Potential+with+Redox-sensitive+Green+Fluorescent+Protein+Indicators.">Investigating Mitochondrial Redox Potential with Redox-sensitive Green Fluorescent Protein Indicators.</a> J. Biol. Chem. 279 (13), 13044-13053 (2004).</li><li>Chen, X., Mao, S. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Titanium+dioxide+nanomaterials:+Synthesis,+properties,+modifications+and+applications.">Titanium dioxide nanomaterials: Synthesis, properties, modifications and applications.</a> Chem. Rev. 107 (7), 2891-2959 (2007).</li><li>Simon, M., Barberet, P., Delville, M. H., Moretto, P., Seznec, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Titanium+dioxide+nanoparticles+induced+intracellular+calcium+homeostasis+modi+fi+cation+in+primary+human+keratinocytes.+Towards+an+in+vitro+explanation+of+titanium+dioxide+nanoparticles+toxicity.">Titanium dioxide nanoparticles induced intracellular calcium homeostasis modi fi cation in primary human keratinocytes. Towards an in vitro explanation of titanium dioxide nanoparticles toxicity.</a> Nanotox. 5 (June), 125-139 (2011).</li><li>Sorieul, 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=An+ion+beam+facility+for+multidisciplinary+research.">An ion beam facility for multidisciplinary research.</a> Nucl. Instr. Meth. Phys. Res., B. 332, 68-73 (2014).</li><li>Barberet, 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=First+results+obtained+using+the+CENBG+nanobeam+line:+Performances+and+applications.">First results obtained using the CENBG nanobeam line: Performances and applications.</a> Nucl Instr Meth Phys Res B. 269 (20), 2163-2167 (2011).</li><li>Dev&#232;s, G., 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=An+ImageJ+plugin+for+ion+beam+imaging+and+data+processing+at+AIFIRA+facility.">An ImageJ plugin for ion beam imaging and data processing at AIFIRA facility.</a> Nucl. Instr. Meth. Phys. Res. B. 348, 62-67 (2015).</li><li>Mayer, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> SIMNRA User's Guide, Report IPP 9/113. , (1997).</li><li>Campbell, J. L., Boyd, N. I., Grassi, N., Bonnick, P., Maxwell, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Guelph+PIXE+software+package+IV.">The Guelph PIXE software package IV.</a> Nucl. Instr. Meth. Phys. Res. B. 268 (20), 3356-3363 (2010).</li><li>Yu, K., Chang, S., Park, S. J., Lim, J., Lee, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Titanium+Dioxide+Nanoparticles+Induce+Endoplasmic+Reticulum+Stress-Mediated+Autophagic+Cell+Death+via+Mitochondria-+Associated+Endoplasmic+Reticulum+Membrane+Disruption+in+Normal+Lung+Cells.">Titanium Dioxide Nanoparticles Induce Endoplasmic Reticulum Stress-Mediated Autophagic Cell Death via Mitochondria- Associated Endoplasmic Reticulum Membrane Disruption in Normal Lung Cells.</a> PLoS ONE. , 1-17 (2015).</li></ol>

We describe a method providing useful information beyond what is possible with other imaging techniques, especially at the subcellular level. In addition to its imaging ability, nuclear microprobe analysis also offers possibilities of quantification of chemical elements entering in the composition of a biological sample. In the present work, we studied human cell populations and focused down to the analysis of a chosen region of interest based on a single cell exposed to TiO2 NPs. Its combination with other te...

Cellular homeostasis is determined by the uptake control, assimilation, and intracellular localization of different trace elements (ions, metals, exogenous inorganic compounds). These components are frequently in the form of traces, but nevertheless may have a considerable impact in the system physiology. Thus, the study of cell biochemistry in both normal and pathological/stressed situations is a key-step towards an overall understanding of cellular metabolic mechanisms. Therefore, the development of imaging and analytical techniques enabling the investigation of intracellular chemical abundances, structural organization and their related metabolic functions becomes necessary. Very few methods are able to provide an in situ quantitative piece of information concerning the overall chemical nature of a given sample. Apart from methods analyzing samples in the bulk form, in situ analyses consider biological samples in their integrality without losing mass and structural information, thereby preserving their constituent chemicals (trace elements and ions) and proteins. Furthermore, as the nanosciences continue to develop, improved imaging and analytical methods for environmental monitoring at the cellular scale will be necessary to observe and quantify nano-object behaviors and interactions.1
Nanoparticles (NPs) have been defined as objects exhibiting at least one facial dimension in the range 1 and 100 nm.2 Due to their particular physicochemical properties, NPs are extensively used in industry. NPs are employed in bio-applications and in nanomedicine.3,4 Despite the numerous physicochemical characteristics of NPs, they may generate some risks of adverse effects on human health and environment. These risks can be induced by both prolonged and repetitive exposures at various concentration levels and this has not yet been clearly established.5,6,7,8 In particular, the fate of NPs inside cells and the associated cellular responses are, to date, not fully described. This is in part due to the scarcity of methods that allow the detection and quantification of internalized NPs in a single cell.9
The classical analytical tools used to estimate the cellular dose of nanoparticles are microscopies, mass spectrometry (MS), inductively coupled plasma MS (ICP-MS)10,11 and liquid chromatography MS (LC-MS), but they only provide useful information at the macroscopic scale. None of them can provide a precise evaluation of the subcellular NPs content nor the NPs distribution without the use of fractionation methods. A systematic assessment of the dose-response is thus impossible with these methods, as opposed to methods based on atomic spectroscopy such as nuclear microprobe analysis12,13, synchrotron X-ray fluorescence microscopy14, and Secondary Ion Mass Spectrometry (SIMS).15,16 These methods are particularly interesting as they complement observations made using fluorescence microscopy, especially when NPs cannot be labeled with fluorescent molecules and are thus studied in their native state. To some extent, even when NPs are grafted with fluorophores, (i) quantification remains difficult because the tagging level per NP is unknown and (ii) the chemical modification of the NP surface may modify its cellular distribution.
In this article, we focus on a method based on a combination of nuclear microprobe techniques aiming at imaging the morphology and elemental composition of biological specimens in major, minor, and trace concentrations.
Nuclear microprobe analysis proves to be particularly suitable for the measurement of trace chemical elements in biological tissues. Both the beam lateral resolution (0.3 to 1 &#181;m) and sensitivity in chemical element detection (from 1 to 10 &#181;g.g-1 dry mass) are well suited for studies at the cellular level. Nuclear microprobe techniques are based on particles detection (photons, electrons, ions) emitted after the ion beam (typically running at MeV energies) interacts with atoms present in the sample. Interactions occurring in cells are mainly: 1) excitation/ionization of atoms followed by an emission of photons after atoms return to their fundamental state; and 2) diffusion of incoming particles leading to change in their energy and direction. The measurement of emitted particle energy allowsthe identification of atoms involved in the interaction. To perform mapping of elements, the ion microbeam is repeatedly scanned over the sample surface, often over an area of about 100 by 100 &#181;m2 containing several cells. Emitted particles are detected and their energy is recorded for each beam position. Sorting of particles according to the beam position, thus identifying the structure responsible for the emission of such particles is the aim of data treatment. Here, we precisely describe an approach based on fluorescence microscopy and nuclear microprobe analysis to detect as well as to quantify exogenous NPs at the cellular and sub-cellular scales, in order to investigate the consequences of NP interactions with living systems. We shall particularly focus on the opportunities offered by this method in terms of in situ quantification of titanium dioxide nanoparticles (TiO2 NPs) aggregates at the subcellular level.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Cell culture</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>U2OS</td>
			<td>ATCC, LGC STANDARDS</td>
			<td>ATCC HTB-96</td>
			<td></td>
		</tr>
		<tr>
			<td>Medium MCCOY 5A w/o L-Glutamine</td>
			<td>Dominique DUTSCHER</td>
			<td>L0211-500</td>
			<td></td>
		</tr>
		<tr>
			<td>FBS 500 mL</td>
			<td>Dominique DUTSCHER</td>
			<td>500105U</td>
			<td></td>
		</tr>
		<tr>
			<td>Penicillin/Streptomycin&#160;</td>
			<td>ThermoFisher Scientific</td>
			<td>11548876</td>
			<td></td>
		</tr>
		<tr>
			<td>&#160;L-Glutamine 200 mM, 100 mL&#160;</td>
			<td>Invitrogen</td>
			<td>25030024</td>
			<td></td>
		</tr>
		<tr>
			<td>Geneticin,&#160; 20 mL</td>
			<td>ThermoFisher Scientific</td>
			<td>10092772</td>
			<td></td>
		</tr>
		<tr>
			<td>Trypsin-EDTA 0.25% (v/v)&#160; 500 mL</td>
			<td>ThermoFisher Scientific</td>
			<td>11570626</td>
			<td></td>
		</tr>
		<tr>
			<td>Viromer Red</td>
			<td>Lipocalyx</td>
			<td>VR-01LB-01</td>
			<td></td>
		</tr>
		<tr>
			<td>Matrix-roGFP Plasmid</td>
			<td>AddGene</td>
			<td>#49437</td>
			<td></td>
		</tr>
		<tr>
			<td>Hoechst 33342</td>
			<td>ThermoFisher Scientific</td>
			<td>H3570</td>
			<td>Handle with care</td>
		</tr>
		<tr>
			<td>NPs preparation</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>TiO2 P25 AEROXIDE</td>
			<td>Degussa/Evonik</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Tetramethylrhodamine isothiocyanate (TRITC)</td>
			<td>SIGMA-ALDRICH</td>
			<td>T3163</td>
			<td>Surface modification of NPs</td>
		</tr>
		<tr>
			<td>Sample preparation</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Polycarbonate foil</td>
			<td>Goodfellow</td>
			<td>CT301020</td>
			<td></td>
		</tr>
		<tr>
			<td>Polyether Ether Ketone support (PEEK)</td>
			<td>Matechplast</td>
			<td>A-239-4047</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethanol, ACS absolute</td>
			<td>SIGMA-ALDRICH</td>
			<td>02860-6x1L</td>
			<td></td>
		</tr>
		<tr>
			<td>Chlorform, Anhydrous, 99%</td>
			<td>SIGMA-ALDRICH</td>
			<td>372978-1L&#160;</td>
			<td>Caution toxic</td>
		</tr>
		<tr>
			<td>Formvar 100 g</td>
			<td>Agar Scientific</td>
			<td>AGR1201</td>
			<td>Harmful. Use in a concentration of 10 &#181;g per mL of chloroform</td>
		</tr>
		<tr>
			<td>NaOH</td>
			<td>SIGMA-ALDRICH</td>
			<td>S5881-500G</td>
			<td></td>
		</tr>
		<tr>
			<td>Sample fixation</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Powder, 95% Paraformaldehyde</td>
			<td>SIGMA-ALDRICH</td>
			<td>158127-500G</td>
			<td>Caution toxic. Use as a 4% solution in PBS</td>
		</tr>
		<tr>
			<td>PBS (pH 7.4, without Ca2+ and Mg2+)</td>
			<td>ThermoFisher Scientific</td>
			<td>11503387</td>
			<td></td>
		</tr>
		<tr>
			<td>Prolong Gold Antifade Reagent</td>
			<td>ThermoFisher Scientific</td>
			<td>P36934</td>
			<td></td>
		</tr>
		<tr>
			<td>Triton X-100</td>
			<td>SIGMA-ALDRICH</td>
			<td>93443</td>
			<td>Harmful</td>
		</tr>
		<tr>
			<td>Sample cryofixation</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Liquid nitrogen</td>
			<td>air liquids sante</td>
			<td></td>
			<td>Harmful</td>
		</tr>
		<tr>
			<td>Methylbutane &#62;=99%</td>
			<td>SIGMA-ALDRICH</td>
			<td>&#160;M32631-1L</td>
			<td>Caution toxic</td>
		</tr>
		<tr>
			<td>Aluminium transfer plate</td>
			<td>Home-made</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Distilled and deionized water</td>
			<td>Home-made</td>
			<td></td>
			<td>Produced in the laboratory using the Barnstead Smart2Pure system</td>
		</tr>
		<tr>
			<td>Parafilm</td>
			<td>VWR</td>
			<td>52858-000</td>
			<td></td>
		</tr>
		<tr>
			<td>Equipment</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Barnstead Smart2Pure</td>
			<td>ThermoFisher Scientific</td>
			<td>50129870</td>
			<td></td>
		</tr>
		<tr>
			<td>Biosafety bench, class II</td>
			<td>ThermoFisher Scientific</td>
			<td>MSC-Advantage</td>
			<td></td>
		</tr>
		<tr>
			<td>TC20 automated cell counter</td>
			<td>Biorad</td>
			<td>145-0102SP</td>
			<td></td>
		</tr>
		<tr>
			<td>Counting slides 2 wells</td>
			<td>Biorad</td>
			<td>1450016</td>
			<td></td>
		</tr>
		<tr>
			<td>PIPS detector, 25 mm2, 12 keV energy resolution @5.5 MeV</td>
			<td>Canberra&#160;</td>
			<td>PD25-12-100AM</td>
			<td></td>
		</tr>
		<tr>
			<td>High-resolution Si (Li) solid-state detector,145-eVenergy resolution, @Mn-K&#945;</td>
			<td>Oxford Instruments</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Everhart-Thornley type secondary electron detector (SED)&#160;</td>
			<td>Orsay Physics</td>
			<td>1-SED</td>
			<td></td>
		</tr>
		<tr>
			<td>XRF Calibration Standard sodium or Chlorine as NaCl</td>
			<td>Micromatter</td>
			<td>34381</td>
			<td></td>
		</tr>
		<tr>
			<td>XRF Calibration Standard Magnesium as MgF2</td>
			<td>Micromatter</td>
			<td>34382</td>
			<td></td>
		</tr>
		<tr>
			<td>XRF Calibration Standard Aluminium as Al metal</td>
			<td>Micromatter</td>
			<td>34383</td>
			<td></td>
		</tr>
		<tr>
			<td>XRF Calibration Standard Silicon as SiO</td>
			<td>Micromatter</td>
			<td>34384</td>
			<td></td>
		</tr>
		<tr>
			<td>XRF Calibration Standard Sulfur as CuSx</td>
			<td>Micromatter</td>
			<td>34385</td>
			<td></td>
		</tr>
		<tr>
			<td>XRF Calibration Standard Calcium as CaF2</td>
			<td>Micromatter</td>
			<td>34387</td>
			<td></td>
		</tr>
		<tr>
			<td>XRF Calibration Standard Titanium as Ti metal</td>
			<td>Micromatter</td>
			<td>34388</td>
			<td></td>
		</tr>
		<tr>
			<td>XRF Calibration Standard Iron as Fe metal</td>
			<td>Micromatter</td>
			<td>34389</td>
			<td></td>
		</tr>
		<tr>
			<td>Sonicator 750W</td>
			<td>Sonics Materials</td>
			<td>11743619</td>
			<td></td>
		</tr>
		<tr>
			<td>3MM microprobe</td>
			<td>Bioblock scientific</td>
			<td>220-05</td>
			<td></td>
		</tr>
		<tr>
			<td>Lyophilizer in vacuum</td>
			<td>Elexience</td>
			<td>EK3147</td>
			<td></td>
		</tr>
		<tr>
			<td>Optical microscope Zeiss AxioObserver Z1</td>
			<td>Carl Zeiss MicroImaging, GmbH</td>
			<td>431006-9901</td>
			<td></td>
		</tr>
		<tr>
			<td>Motorized stage xy</td>
			<td>Carl Zeiss MicroImaging, GmbH</td>
			<td>432031-9902</td>
			<td></td>
		</tr>
		<tr>
			<td>EC Plan-Neofluar 20X, NA 0.50 Ph2 M27 objective</td>
			<td>Carl Zeiss MicroImaging, GmbH</td>
			<td>420351-9910</td>
			<td></td>
		</tr>
		<tr>
			<td>Plan-Apochromat 63X, NA 1,40 Ph3M27 objective</td>
			<td>Carl Zeiss MicroImaging, GmbH</td>
			<td>420781-9910</td>
			<td></td>
		</tr>
		<tr>
			<td>Zeiss filterset 02</td>
			<td>Carl Zeiss MicroImaging, GmbH</td>
			<td>488002-9901</td>
			<td></td>
		</tr>
		<tr>
			<td>Zeiss filterset 38HE</td>
			<td>Carl Zeiss MicroImaging, GmbH</td>
			<td>489038-9901</td>
			<td></td>
		</tr>
		<tr>
			<td>Zeiss filterset 31</td>
			<td>Carl Zeiss MicroImaging, GmbH</td>
			<td>000000-1031-350</td>
			<td></td>
		</tr>
		<tr>
			<td>Chemical fume hood</td>
			<td>Erlab</td>
			<td>Captair SD321</td>
			<td></td>
		</tr>
		<tr>
			<td>Particle accelerator</td>
			<td>HVEE</td>
			<td>singletron</td>
			<td></td>
		</tr>
		<tr>
			<td>Software</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>ImageJ software</td>
			<td>National Institutes of health, USA</td>
			<td>ImageJ 1.51</td>
			<td></td>
		</tr>
		<tr>
			<td>SimNRA software</td>
			<td>Max-Planck-Institut f&#252;r Plasmaphysik, Germany</td>
			<td>SIMNRA 6.06</td>
			<td></td>
		</tr>
		<tr>
			<td>Gupix software</td>
			<td>Guelph university, Canada</td>
			<td>GUPIXWIN 2.2.4</td>
			<td></td>
		</tr>
	</tbody>
</table>

in situ detection and single cell quantification of metal oxide nanoparticles using nuclear microprobe analysis

Micro-analytical techniques based on chemical element imaging enable the localization and quantification of chemical composition at the cellular level. They offer new possibilities for the characterization of living systems and are particularly appropriate for detecting, localizing and quantifying the presence of metal oxide nanoparticles both in biological specimens and the environment. Indeed, these techniques all meet relevant requirements in terms of (i) sensitivity (from 1 up to 10 &#181;g.g-1 of dry mass), (ii) micrometer range spatial resolution, and (iii) multi-element detection. Given these characteristics, microbeam chemical element imaging can powerfully complement routine imaging techniques such as optical and fluorescence microscopy. This protocol describes how to perform a nuclear microprobe analysis on cultured cells (U2OS) exposed to titanium dioxide nanoparticles. Cells must grow on and be exposed directly in a specially designed sample holder used on the optical microscope and in the nuclear microprobe analysis stages. Plunge-freeze cryogenic fixation of the samples preserves both the cellular organization and the chemical element distribution. Simultaneous nuclear microprobe analysis (scanning transmission ion microscopy, Rutherford backscattering spectrometry and particle induced X-ray emission) performed on the sample provides information about the cellular density, the local distribution of the chemical elements, as well as the cellular content of nanoparticles. There is a growing need for such analytical tools within biology, especially in the emerging context of Nanotoxicology and Nanomedicine for which our comprehension of the interactions between nanoparticles and biological samples must be deepened. In particular, as nuclear microprobe analysis does not require nanoparticles to be labelled, nanoparticle abundances are quantifiable down to the individual cell level in a cell population, independently of their surface state.

Cell culture and fluorescence imaging of fluorescently labeled TiO2 NPs
We designed a sample holder adapted for cell culture, cell handling as well as multimodal analysis. Specifically, it was important that the holder permitted routine optical microscopy as well as nuclear microprobe analysis and imaging. This sample holder is based on a 2-&#181;m thick polycarbonate...

Watch this Scientific Journal Video about In Situ Detection and Single Cell Quantification of Metal Oxide Nanoparticles Using Nuclear Microprobe Analysis at JoVE.com

In Situ Detection and Single Cell Quantification of Metal Oxide Nanoparticles Using Nuclear Microprobe Analysis

We describe a procedure for the detection of chemical elements present in situ in human cells as well as their in vitro quantification. The method is well-suited to any cell type and is particularly useful for quantitative chemical analyses in single cells following in vitro metal oxide nanoparticles exposure.

In Situ Detection and Single Cell Quantification of Metal Oxide Nanoparticles Using Nuclear Microprobe Analysis

Micro-analytical techniques based on chemical element imaging enable the localization and quantification of chemical composition at the cellular level. ...

Nanoparticles are increasingly used in industry and medicine due to their unique physiochemical properties. However, concerns for human health associated with prolonged nanoparticle exposure persists. These risks can be quantified by studying the behavior of nanoparticles inside cells and the induced metabolic responses of cells to nanoparticles.This is partially due to the lack of methods that allow the detection and quantification of internalized nanoparticles in a sincle cell. While numerous analytical tools, including microscopy and mass spectrometry, can be used to estimate the cellular uptake of nanoparticles, these only provide qualitative information at a microscopic level. On the contrary, in situ methods based on atomic spectroscopy can reduce the quantity of imaging artifacts that arise from sample preparation and can yield direct observation of nanoparticles.To take advantage of this, we present a correlative approach which allows us to study nanoparticles either in the native state or lab bed with a fluorescent tag. Here, we describe a method based on the combination of fluorescence microscopy and nuclear microprobe analysis. This provides images of the cellular density, chemical element special distribution, and the amount of nanoparticles per cell.As a demonstration, we shall research from cells exposed to titanium dioxide nanoparticles over 24 hours using both fluorescence microscopy and nuclear microprobe analysis. For this protocol, a custom sample holder made with the polymer PEEK is needed. It must be suited for cell culturing and in vitro observations.Cover the holder with two micron thick polycarbonate foil. The polycarbonate foil is glued to the PEEK dish with a thin layer of Formvar solution. Once mounted, the sample holder needs to be sterilized.Multiple sterile sample holders may be stored, one per well, in a sterile twelve-well plate until they are needed for use. Cells transfected with matrix row GFP plasmids are checked by fluorescence microscopy to insure transfection has occurred successfully, and that they express the fluorescent protein. Harvest the cells with trypsin, and incubate them for three minutes at 37 degrees Celsius.Stop the trypsin action by adding fresh culture medium. Pellet the cells by centrifugation for five minutes at 1200 revolutions per minute at four degrees Celsius. Remove the supernatant and add an appropriate volume of fresh culture medium.Count the cells and perform a dilution with fresh and thermostated complete culture medium to obtain a cell suspension of 500 cells per microliter. Plate a 40-microliter drop at the center of the polycarbonate foil. Carefully place the sample in the cell incubator for two hours.Gently add two milliliters of fresh culture medium and leave them for 24 hours. Fluorescent dimodified titanium oxide nanoparticles were designed, synthesized, and grafted with commonly used fluorophores in order to detect, track, and localize nanoparticles in vitro. For this step, a titanium dioxide nanoparticle suspension in ultra-pure water with a concentration of one milligram per milliliter should already have been prepared.Disperse the nanoparticles by using one-minute long intense sonication pulses at room temperature. Dilute the nanoparticles in an appropriate culture medium to obtain an exposure suspension of four micrograms per square centimeter. Switch the previous cell culture medium to this new nanoparticle-containing medium and mix it gently to achieve a homogeneous nanoparticle distribution.Prepare a set of control cells in the same manner without the addition of titanium dioxide nanoparticles. Incubate the cell populations for 24 hours. Using paraformaldehyde, these samples may be fixed and processed for in situ and single-cell imaging using fluorescence microscopy.Cryogenic physical fixation, however, preserves the cell ultrastructure and biochemical integrity. Plunge freezing fixation rapidly stops the cellular activity within milliseconds and avoids using fixative compounds. To cryogenically fix the cells, we perform the following.Prepare an aluminum transfer plate by cooling it in liquid nitrogen. Store the plate in a box filled with liquid nitrogen, keeping the plate surface above the liquid in the cold nitrogen vapor. Chill a sufficient amount of 2-methylbutane to 150 degrees Celsius.Prepare one 50 milliliter Falcon with culture medium and two Falcons with ultra-pure water. Ensure absorbent paper is nearby to dry the sample before freezing it. Rinse cells once in culture medium and then two more times in sterile, ultra-pure water to remove excess salts remaining in the culture medium.Quickly dry the sample on the absorbent paper. Plunge-freeze the cells in the chilled 2-methylbutane for 30 seconds and place them on the chilled aluminum transfer plate. It is critical that the box be kept closed as much as possible in order to prevent water vapor from condensing on the cold plate surface.After freezing all samples, freeze-drying is performed by the following method to sublimate away any water. First, perform a primary desiccation for 12 to 24 hours at low pressure and low temperature. Next, keeping the pressure low, perform a secondary desiccation phase for at least 24 hours with the plate temperature increased to 40 degrees Celsius.After cryofixation, samples can be stored at room temperature for several days in sterile and dry conditions protected from dust and moisture. Nuclear microprobe analysis was conducted at the Ifera facility in Bordeaux, France. A 3.5 megavolt singletron particle accelerator delivers a light ion beam in the megaelectron volt energy range.Chemical element imaging was carried out on the microprobe beamline using complementary ion beam analytical techniques. The techniques used through a micro-PIXE, particle-induced X-ray emission, STIM, scanning transmission ion microscopy, and micro-RBS, rutherford backscattering spectrometry. Samples are positioned inside the analysis chamber and irradiated under vacuum with different particles in order to perform different ion beam analyses.STIM is used to record aerial density maps of cells based on the energy particles loose passing through regions of cells with different densities. Micro-PIXE and micro-RBS analysis provide the spatial distribution and quantification of chemical elements at a single-cell level. A 1.5 megaelectron volt proton microbeam is focused down to a diameter of about 1 micrometer and it is scanned across the cells of interest, identified by STIM.X-rays emitted from atoms present in the sample, ranging from sodium to titanium, permit the elemental concentrations to be determined. Backscattered protons are collected in order to measure the total number of incoming particles required to normalize X-ray intensities. It is critical to have certified calibration standards for the quantification of elemental concentrations in order to calibrate the X-ray detector response.In order to the analyze the ion beam data, we developed a new plugin for ImageJ. First, STIM density maps were calculated. Contrast in scanning transmission iron microscopy images is due to local differences in density and allows the detection of cell structures such as the nucleus and cytoplasm.Several maps can be processed at once. Each map corresponds to the medium transmitted energy from incoming particles. The second step in data analysis consists in calculating individual cell spectra.Particle-induced X-ray emission analysis yields both the chemical composition of the sample and the elemental maps of chemical elements. Chemical element maps are computed after sorting photons according to the beam position at the time of recording and selecting an energy window centered around a specific element. Maps usually represent the number of detected events at the beam position and contain quantitative data.A stack of chemical maps, one for each selected element, is calculated. Regions of interest for each cell are found using the PIXE data for phosphorus. The spectra corresponding to each whole cell is then calculated by summing the individual spectra across each cell's region of interest.From here, quantitative data about chemical abundances in each cell can be extracted using dedicated PIXE and IBS analysis software. Here we show fluorescence imagery of cells after paraformaldehyde fixation. The top row shows cells that have not been exposed to titanium dioxide nanoparticles while the bottom row has been.The blue channel shows the cell nucleus, the green channel shows mitochondria, and the red channel shows titanium. It can be clearly seen that no titanium dioxide is present in the controls. From the merged channel at the right, it can be seen that nanoparticles are found exclusively in the cytoplasm and are excluded from mitochondria.What this method lacks, however, is quantitative information about the nanoparticle concentration. Nuclear microprobe analysis can hope to provide this. These images have all been taken using various microprobe analysis techniques.Again, the top row shows the control cells and the bottom row shows cells containing titanium nanoparticles. The leftmost image shows STIM measurements of the density of the cryogenically fixed cells. The following three panels show the abundance of potassium, phosphorus, and titanium present in the cells obtained by PIXE.Again, no titanium is visant in the controls nor in the cell nuclei. In order to quantify, cell by cell, the uptake of titanium, we define regions of interest based on the cell boundaries shown in the rightmost panel and measure the elemental abundances in these regions. From these PIXE measurements, we have plotted the distribution of elemental abundances at the single-cell level for the control and the exposed populations.The control population is plotted in white, and the exposed population is plotted in yellow. The median content of titanium present here is quite low compared to the four microgram per square centimeter exposure dose. The range of titanium uptake shows a large variation across the population, from 0.2 micrograms per square centimeter up to 1.8 micrograms per square centimeter.We also noticed an increase of free intracellular ions such as potassium and calcium in nanoparticle-exposed samples, suggesting an alteration to cellular homeostasis induced by the presence of titanium dioxide nanoparticles. Nuclear microprobe analysis can provide useful information on the subcellular level and provides a quantification of the chemical elements that make up a biological sample. These techniques present many advantages.One, in sample preparation which does not require chemical fixation. Two, the possibility to study larger areas with the ability to focus on additional regions of interest. Three, the quantification of chemical elements with a sensitivity of a few micrograms per gram.And four, the identification of cell compartments such as the nucleus, nucleolus, and cytoplasm. The accurate determination of those, when studying the internalization of nanoparticles in single cells, is essential for quantitative nanoparticle toxicology. As shown in the cases studied here, the ability to observe and quantify nanoparticles within individual cells allow us to better understand the value accumulation of endogenous and exogenous chemical elements, such metal oxide nanoparticles.This protocol highlights the suitability of nuclear microprobe analysis for future studies of nanoparticle interaction with living cells. The quantitative approach gives information about the impact of these nanoparticles in terms of detection, identification, localization, and quantification, and in single-cell level for both native and chemical modified-nanoparticles.

in-situ-detection-single-cell-quantification-metal-oxide

Research

JoVE Journal

Chemistry

Using Polystyrene-block-poly(acrylic acid)-coated Metal Nanoparticles as Monomers for Their Homo- and Co-polymerization

We present a template-free method for &#8220;polymerizing&#8221; nanoparticles into long chains without side branches. A variety of nanoparticles are encapsulated in polystyrene-block-poly(acrylic acid) (PSPAA) shells and then used as monomers for their self-assembly. Spherical PSPAA micelles upon acid treatment are known to assemble into cylindrical micelles. Exploiting this tendency, the core-shell nanoparticles are induced to aggregate, coalesce, and then transform into long chains. When more than one type of nanoparticles are used, random and block &#8220;copolymers&#8221; of nanoparticles can be obtained. Detailed procedures are reported for the PSPAA encapsulation of nanoparticles, homo- and co-polymerization of the core-shell nanoparticles, separation and purification of the resulting nanoparticle chains. Transformations of single-line chains into double- and triple-line chains are also presented. The synergy between the polymer shell and the embedded nanoparticles leads to an unusual chain-growth polymerization mode, giving long nanoparticle chains that are distinct from the products of the traditional step-growth aggregation process.

Using Polystyrene-block-polyacrylic acid-coated Metal Nanoparticles as Monomers for Their Homo- and Co-polymerization

We report protocols for &#8220;polymerizing&#8221; various types of polymer-encapsulated metal nanoparticles into long chains of &#8220;homo-&#8220; and &#8220;co-polymers&#8221;.

We present a template-free method for &#8220;polymerizing&#8221; nanoparticles into long chains without side branches. A variety of nanoparticles are ...

Reverse Microemulsion-mediated Synthesis of Monometallic and Bimetallic Early Transition Metal Carbide and Nitride Nanoparticles

A reverse microemulsion is used to encapsulate monometallic or bimetallic early transition metal oxide nanoparticles in microporous silica shells. The silica-encapsulated metal oxide nanoparticles are then carburized in a methane/hydrogen atmosphere at temperatures over 800 &#176;C to form silica-encapsulated early transition metal carbide nanoparticles. During the carburization process, the silica shells prevent the sintering of adjacent carbide nanoparticles while also preventing the deposition of excess surface carbon. Alternatively, the silica-encapsulated metal oxide nanoparticles can be nitridized in an ammonia atmosphere at temperatures over 800 &#176;C to form silica-encapsulated early transition metal nitride nanoparticles. By adjusting the reverse microemulsion parameters, the thickness of the silica shells, and the carburization/nitridation conditions, the transition metal carbide or nitride nanoparticles can be tuned to various sizes, compositions, and crystal phases. After carburization or nitridation, the silica shells are then removed using either a room-temperature aqueous ammonium bifluoride solution or a 0.1 to 0.5 M NaOH solution at 40-60 &#176;C. While the silica shells are dissolving, a high surface area support, such as carbon black, can be added to these solutions to obtain supported early transition metal carbide or nitride nanoparticles. If no high surface area support is added, then the nanoparticles can be stored as a nanodispersion or centrifuged to obtain a nanopowder.

A &#8220;removable ceramic coating method&#8221; is presented in visual format for the synthesis of non-sintered and metal-terminated monometallic and bimetallic early transition metal carbide and nitride nanoparticles with tunable sizes and crystal structures.

A reverse microemulsion is used to encapsulate monometallic or bimetallic early transition metal oxide nanoparticles in microporous silica shells. The ...

Generation of Zerovalent Metal Core Nanoparticles Using n-(2-aminoethyl)-3-aminosilanetriol

In this work, a facile one-pot reaction for the formation of metal nanoparticles in a water solution through the use of n-(2-aminoethyl)-3-aminosilanetriol is presented. This compound can be used to effectively reduce and complex metal salts into metal core nanoparticles coated with the compound. By controlling the concentrations of salt and silane one is able to control reaction rates, particle size, and nanoparticle coating. The effects of these changes were characterized through transmission electron microscopy (TEM), UV-Vis spectrometry (UV-Vis), Nuclear Magnetic Resonance spectroscopy (NMR) and Fourier Transform Infrared spectroscopy (FTIR). A unique aspect to this reaction is that usually silanes hydrolyze and cross-link in water; however, in this system the silane is water-soluble and stable. It is known that silicon and amino moieties can form complexes with metal salts. The silicon is known to extend its coordination sphere to form penta- or hexa-coordinated species. Furthermore, the silanol group can undergo hydrolysis to form a Si-O-Si silica network, thereby transforming the metal nanoparticles into a functionalized nanocomposites.

Generation of Zerovalent Metal Core Nanoparticles Using n-2-aminoethyl-3-aminosilanetriol

A novel method for metal core nanoparticle synthesis using a water stable silanol is described.

In this work, a facile one-pot reaction for the formation of metal nanoparticles in a water solution through the use of ...

Photochemical Oxidative Growth of Iridium Oxide Nanoparticles on CdSe@CdS Nanorods

We demonstrate a procedure for the photochemical oxidative growth of iridium oxide catalysts on the surface of seeded cadmium selenide-cadmium sulfide (CdSe@CdS) nanorod photocatalysts. Seeded rods are grown using a colloidal hot-injection method and then moved to an aqueous medium by ligand exchange. CdSe@CdS nanorods, an iridium precursor and other salts are mixed and illuminated. The deposition process is initiated by absorption of photons by the semiconductor particle, which results with formation of charge carriers that are used to promote redox reactions. To insure photochemical oxidative growth we used an electron scavenger. The photogenerated holes oxidize the iridium precursor, apparently in a mediated oxidative pathway. This results in the growth of high quality crystalline iridium oxide particles, ranging from 0.5 nm to about 3 nm, along the surface of the rod. Iridium oxide grown on CdSe@CdS heterostructures was studied by a variety of characterization methods, in order to evaluate its characteristics and quality. We explored means for control over particle size, crystallinity, deposition location on the CdS rod, and composition. Illumination time and excitation wavelength were found to be key parameters for such control. The influence of different growth conditions and the characterization of these heterostructures are described alongside a detailed description of their synthesis. Of significance is the fact that the addition of iridium oxide afforded the rods astounding photochemical stability under prolonged illumination in pure water (alleviating the requirement for hole scavengers).

A protocol for the photochemical oxidative growth of small crystalline iridium oxide nanoparticles on the surface of CdSe@CdS seeded rod nanoparticles is presented.

We demonstrate a procedure for the photochemical oxidative growth of iridium oxide catalysts on the surface of seeded cadmium selenide-cadmium sulfide ...

Sequencing of Plant Wall Heteroxylans Using Enzymic, Chemical (Methylation) and Physical (Mass Spectrometry, Nuclear Magnetic Resonance) Techniques

This protocol describes the specific techniques used for the characterization of reducing end (RE) and internal region glycosyl sequence(s) of heteroxylans. De-starched wheat endosperm cell walls were isolated as an alcohol-insoluble residue (AIR)1 and sequentially extracted with water (W-sol Fr) and 1 M KOH containing 1% NaBH4 (KOH-sol Fr) as described by Ratnayake et al. (2014)2. Two different approaches (see summary in Figure 1) are adopted. In the first, intact W-sol AXs are treated with 2AB to tag the original RE backbone chain sugar residue and then treated with an endoxylanase to generate a mixture of 2AB-labelled RE and internal region reducing oligosaccharides, respectively. In a second approach, the KOH-sol Fr is hydrolyzed with endoxylanase to first generate a mixture of oligosaccharides which are subsequently labelled with 2AB. The enzymically released ((un)tagged) oligosaccharides from both W- and KOH-sol Frs are then methylated and the detailed structural analysis of both the native and methylated oligosaccharides is performed using a combination of MALDI-TOF-MS, RP-HPLC-ESI-QTOF-MS and ESI-MSn. Endoxylanase digested KOH-sol AXs are also characterized by nuclear magnetic resonance (NMR) that also provides information on the anomeric configuration. These techniques can be applied to other classes of polysaccharides using the appropriate endo-hydrolases.

Sequencing of Plant Wall Heteroxylans Using Enzymic, Chemical Methylation and Physical Mass Spectrometry, Nuclear Magnetic Resonance Techniques

This protocol describes the specific techniques used for the structural characterization of reducing end (RE) and internal region glycosyl sequence(s) of heteroxylans by tagging the RE with 2 aminobenzamide prior to enzymatic (endoxylanase) hydrolysis and then analysis of the resultant oligosaccharides using mass spectrometry (MS) and nuclear magnetic resonance (NMR).

This protocol describes the specific techniques used for the characterization of reducing end (RE) and internal region glycosyl sequence(s) of ...

Aerosol-assisted Chemical Vapor Deposition of Metal Oxide Structures: Zinc Oxide Rods

Whilst columnar zinc oxide (ZnO) structures in the form of rods or wires have been synthesized previously by different liquid- or vapor-phase routes, their high cost production and/or incompatibility with microfabrication technologies, due to the use of pre-deposited catalyst-seeds and/or high processing temperatures exceeding 900 &#176;C, represent a drawback for a widespread use of these methods. Here, however, we report the synthesis of ZnO rods via a non-catalyzed vapor-solid mechanism enabled by using an aerosol-assisted chemical vapor deposition (CVD) method at 400 &#176;C with zinc chloride (ZnCl2) as the precursor and ethanol as the carrier solvent. This method provides both single-step formation of ZnO rods and the possibility of their direct integration with various substrate types, including silicon, silicon-based micromachined platforms, quartz, or high heat resistant polymers. This potentially facilitates the use of this method at a large-scale, due to its compatibility with state-of-the-art microfabrication processes for device manufacture. This report also describes the properties of these structures (e.g., morphology, crystalline phase, optical band gap, chemical composition, electrical resistance) and validates its gas sensing functionality towards carbon monoxide.

Columnar zinc oxide structures in the form of rods are synthesized via aerosol-assisted chemical vapor deposition without the use of pre-deposited catalyst-seed particles. This method is scalable and compatible with various substrates based on either silicon, quartz or polymers.

Whilst columnar zinc oxide (ZnO) structures in the form of rods or wires have been synthesized previously by different liquid- or vapor-phase routes, ...

Microprobe Capillary Electrophoresis Mass Spectrometry for Single-cell Metabolomics in Live Frog (Xenopus laevis) Embryos

The quantification of small molecules in single cells raises new potentials for better understanding the basic processes that underlie embryonic development. To enable single-cell investigations directly in live embryos, new analytical approaches are needed, particularly those that are sensitive, selective, quantitative, robust, and scalable to different cell sizes. Here, we present a protocol that enables the in situ analysis of metabolism in single cells in freely developing embryos of the South African clawed frog (Xenopus laevis), a powerful model in cell and developmental biology. This approach uses a capillary microprobe to aspirate a defined portion from single identified cells in the embryo, leaving neighboring cells intact for subsequent analysis. The collected cell content is analyzed by a microscale capillary electrophoresis electrospray ionization (CE-ESI) interface coupled to a high-resolution tandem mass spectrometer. This approach is scalable to various cell sizes and compatible with the complex three-dimensional structure of the developing embryo. As an example, we demonstrate that microprobe single-cell CE-ESI-MS enables the elucidation of metabolic cell heterogeneity that unfolds as a progenitor cell gives rise to descendants during development of the embryo. Besides cell and developmental biology, the single-cell analysis protocols described here are amenable to other cell sizes, cell types, or animal models.

Microprobe Capillary Electrophoresis Mass Spectrometry for Single-cell Metabolomics in Live Frog Xenopus laevis Embryos

We describe steps that enable fast in situ sampling of a small portion of an individual cell with high precision and minimal invasion using capillary-based micro-sampling, to facilitate chemical characterization of a snapshot of metabolic activity in live embryos using a custom-built single cell capillary electrophoresis and mass spectrometry platform.

The quantification of small molecules in single cells raises new potentials for better understanding the basic processes that underlie embryonic ...

Ligand-Mediated Nucleation and Growth of Palladium Metal Nanoparticles

The size, size distribution and stability of colloidal nanoparticles are greatly affected by the presence of capping ligands. Despite the key contribution of capping ligands during the synthesis reaction, their role in regulating the nucleation and growth rates of colloidal nanoparticles is not well understood. In this work, we demonstrate a mechanistic investigation of the role of trioctylphosphine (TOP) in Pd nanoparticles in different solvents (toluene and pyridine) using in situ SAXS and ligand-based kinetic modeling. Our results under different synthetic conditions reveal the overlap of nucleation and growth of Pd nanoparticles during the reaction, which contradicts the LaMer-type nucleation and growth model. The model accounts for the kinetics of Pd-TOP binding for both, the precursor and the particle surface, which is essential to capture the size evolution as well as the concentration of particles in situ. In addition, we illustrate the predictive power of our ligand-based model through designing the synthetic conditions to obtain nanoparticles with desired sizes. The proposed methodology can be applied to other synthesis systems and therefore serves as an effective strategy for predictive synthesis of colloidal nanoparticles.

The main goal of this work is to elucidate the role of capping agents in regulating the size of palladium nanoparticles by combining in situ small angle x-ray scattering (SAXS) and ligand-based kinetic modeling.

The size, size distribution and stability of colloidal nanoparticles are greatly affected by the presence of capping ligands. Despite the key contribution ...

High Resolution Physical Characterization of Single Metallic Nanoparticles

Individual molecules can be detected and characterized by measuring the degree by which they reduce the ionic current flowing through a single nanometer-scale pore. The signal is characteristic of the molecule&#39;s physicochemical properties and its interactions with the pore. We demonstrate that the nanopore formed by the bacterial protein exotoxin Staphylococcus aureus alpha hemolysin (&#945;HL) can detect polyoxometalates (POMs, anionic metal oxygen clusters), at the single molecule limit. Moreover, multiple degradation products of 12-phosphotungstic acid POM (PTA, H3PW12O40) in solution are simultaneously measured. The single molecule sensitivity of the nanopore method allows for POMs to be characterized at significantly lower concentrations than required for nuclear magnetic resonance (NMR) spectroscopy. This technique could serve as a new tool for chemists to study the molecular properties of polyoxometalates or other metallic clusters, to better understand POM synthetic processes, and possibly improve their yield. Hypothetically, the location of a given atom, or the rotation of a fragment in the molecule, and the metal oxidation state could be investigated with this method. In addition, this new technique has the advantage of allowing the real-time monitoring of molecules in solution.&#160;

Here, we present a protocol to detect discrete metal oxygen clusters, polyoxometalates (POMs), at the single molecule limit using a biological nanopore-based electronic platform. The method provides a complementary approach to traditional analytical chemistry tools used in the study of these molecules.

Individual molecules can be detected and characterized by measuring the degree by which they reduce the ionic current flowing through a single ...

Molten-Salt Synthesis of Complex Metal Oxide Nanoparticles

The development of feasible synthesis methods is critical for the successful exploration of novel properties and potential applications of nanomaterials. Here, we introduce the molten-salt synthesis (MSS) method for making metal oxide nanomaterials. Advantages over other methods include its simplicity, greenness, reliability, scalability, and generalizability. Using pyrochlore lanthanum hafnium oxide (La2Hf2O7) as a representative, we describe the MSS protocol for the successful synthesis of complex metal oxide nanoparticles (NPs). Furthermore, this method has the unique ability to produce NPs with different material features by changing various synthesis parameters such as pH, temperature, duration, and post-annealing. By fine-tuning these parameters, we are able to synthesize highly uniform, non-agglomerated, and highly crystalline NPs. As a specific example, we vary the particle size of the La2Hf2O7&#160;NPs by changing the concentration of the ammonium hydroxide solution used in the MSS process, which allows us to further explore the effect of particle size on various properties. It is expected that the MSS method will become a more popular synthesis method for nanomaterials and more widely employed in the nanoscience and nanotechnology community in the upcoming years.

Here, we demonstrate a unique, relatively low-temperature, molten-salt synthesis method for preparing uniform complex metal oxide lanthanum hafnate nanoparticles.

The development of feasible synthesis methods is critical for the successful exploration of novel properties and potential applications of nanomaterials. ...