Name: high resolution physical characterization of single metallic nanoparticles
Uploaded: 2019-06-28T11:00:00
Description: Watch this Scientific Journal Video about High Resolution Physical Characterization of Single Metallic Nanoparticles at JoVE.com

We are grateful for financial support from the European Molecular Biology Organization for a postdoctoral fellowship (to J.E.) and a grant from the NIH NHGRI (to J.J.K.). We appreciate the help of Professors Jingyue Ju and Sergey Kalachikov (Columbia University) for providing heptameric &#945;HL, and for inspiring discussions with Professor Joseph Reiner (Virginia Commonwealth University).

Note: The protocol below is specific to the Electronic BioSciences (EBS) Nanopatch DC System. However, it can be readily adapted to other electrophysiology apparatus used to measure the current through planar lipid bilayer membranes (standard lipid bilayer membrane chamber, U-tube geometry, pulled microcapillaries, etc.). The identification of commercial materials and their sources is given to describe the experimental results. In no case does this identification imply recommendation by the Nati...

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T., Hill, C. L., Judd, D. A., Schinazi, R. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Polyoxometalates+in+medicine.">Polyoxometalates in medicine.</a> Chemical Reviews. 98 (1), 327-358 (1998).</li><li>Gao, N., 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=Transition-metal-substituted+polyoxometalate+derivatives+as+functional+anti-amyloid+agents+for+Alzheimer's+disease.">Transition-metal-substituted polyoxometalate derivatives as functional anti-amyloid agents for Alzheimer's disease.</a> Nature Communications. 5, 3422 (2014).</li><li>Pope, M. 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Due to their anionic charge, POMs likely associate with organic counter cations through electrostatic interactions. Therefore, it is important to identify the proper solution conditions and the right electrolyte environments (especially cations in solution) to avoid complex formation with POMs. Particular care is required in the buffer choice. For example, the capture rate of POMs with tris(hydroxymethyl)aminomethane and citric acid-buffered solutions is significantly lower than that in phosphate buffered solution, likel...

Detecting biomolecular analytes at the single molecule level can be performed by using nanopores and measuring ionic current modulations. Typically, nanopores are divided into two categories based on their fabrication: biological (self-assembled from protein or DNA origami)1,2,3, or solid-state (e.g., manufactured with semiconductor processing tools)4,5. While solid-state nanopores were suggested as potentially more physically robust and can be used over a wide range of solution conditions, protein nanopores thus far offer greater sensitivity, more resistance to fouling, greater bandwidth, better chemical selectivity, and a greater signal to noise ratio.
A variety of protein ion channels, such as the one formed by Staphylococcus aureus &#945;-hemolysin (&#945;HL), can be used to detect single molecules, including ions (e.g., H+ and D+)2,3, polynucleotides (DNA and RNA)6,7,8, damaged DNA9, polypeptides10, proteins (folded and unfolded)11, polymers (polyethylene glycol and others)12,13,14, gold nanoparticles15,16,17,18,19, and other synthetic molecules20.
We recently demonstrated that the &#945;HL nanopore can also easily detect and characterize metallic clusters, polyoxometalates (POMs), at the single molecule level. POMs are discrete nanoscale anionic metal oxygen clusters that were discovered in 182621, and since then, many more types have been synthesized. The different sizes, structures, and elemental compositions of polyoxometalates that are now available led to a wide range of properties and applications including chemistry22,23, catalysis24, material science25,26, and biomedical research27,28,29.
POM synthesis is a self-assembly process typically carried out in water by mixing the stoichiometrically required amounts of monomeric metal salts. Once formed, POMs exhibit a great diversity of sizes and shapes. For example, the Keggin polyanion structure, XM12O40q- is composed of one heteroatom (X) surrounded by four oxygens to form a tetrahedron (q is the charge). The heteroatom is centrally located within a cage formed by 12 octahedral MO6 units (where M = transition metals in their high oxidation state), which are linked to one another by neighboring shared oxygen atoms. While tungsten polyoxometalates structure is stable in acidic conditions, hydroxide ions lead to the hydrolytic cleavage of metal-oxygen (M-O) bonds30. This complex process results in the loss of one or more MO6 octahedral subunits, leading to the formation of monovacant and trivacant species and eventually to the complete decomposition of the POMs. Our discussion here will be limited to the partial decomposition products of 12-phosphotungstic acid at pH 5.5 and 7.5.
The goal of this protocol is to detect discrete metal oxygen clusters at the single molecule limit using a biological nanopore-based electronic platform. This method allows the detection of metallic clusters in solution. Multiple species in solution can be discriminated with greater sensitivity than conventional analytical methods33. With it, subtle differences in POM structure can be elucidated, and at concentrations markedly lower than those required for NMR spectroscopy. Importantly, this approach even allows the discrimination of isomeric forms of Na8HPW9O341.

<table>
	<tbody>
		<tr>
			<td>Nanopatch DC System</td>
			<td>Electronic Biosciences, Inc., EBS</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Millipore LC-PAK</td>
			<td>Millipore vacuum filter</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>1,2-Diphytanoyl-sn- Glycero-3-Phosphocholine (DPhPC)</td>
			<td>Avanti Polar Lipids, Alabaster, AL</td>
			<td>850356P</td>
			<td></td>
		</tr>
		<tr>
			<td>Decane, ReagentPlus, &#8805;99%,</td>
			<td>Sigma-Aldrich</td>
			<td>D901</td>
			<td></td>
		</tr>
		<tr>
			<td>&#945;HL</td>
			<td>List Biological Laboratories, Campbell, CA</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Ag wire</td>
			<td>Alfa Aesar</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>2 mm Ag/AgCl disk electrode</td>
			<td>In Vivo Metric</td>
			<td>E202</td>
			<td></td>
		</tr>
		<tr>
			<td>High-impedance amplifier system</td>
			<td>Electronic Biosciences, San Diego, CA</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>quartz capillaries</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>custom polycarbonate test cell</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Data Processing and Analysis MOSAIC</td>
			<td>https://pages.nist.gov/mosaic/</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Phosphotungstic acid hydrate</td>
			<td>Sigma-Aldrich</td>
			<td>455970</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium Chloride</td>
			<td>Sigma-Aldrich</td>
			<td>S3014</td>
			<td></td>
		</tr>
		<tr>
			<td>sodium phosphate monobasic monohydrate</td>
			<td>Sigma-Aldrich</td>
			<td>71507</td>
			<td></td>
		</tr>
	</tbody>
</table>

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;

Over the past two decades, membrane-bound protein nanometer-scale pores have been demonstrated as versatile single-molecule sensors. Nanopore-based measurements are relatively straightforward to execute.&#160; Two chambers&#160;filled with electrolyte solution are separated by a nanopore embedded in an electrically insulating lipid membrane. Either a patch-clamp amplifier or an external power supply provides an electrostatic potential across the nanopore via Ag/AgCl electrodes im...

Watch this Scientific Journal Video about High Resolution Physical Characterization of Single Metallic Nanoparticles at JoVE.com

High Resolution Physical Characterization of Single Metallic Nanoparticles

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 ...

This nanopore-based detection method has demonstrated the potential to physically characterize and identify individual molecules. Working with metallo-nanoparticles, which is the purpose of this video, is challenging our understanding of what limits the measurement's accuracy and precision. The main advantage of this technique is that this apparatus has greater bandwidth than traditional lipid bilayer memory set-up, which lets us see faster results and more reactions in nanopore.This technique was made possible because in the early 1990s it was shown that gating in protein nanopores, that is, switching between different states, can be controlled and molecules can bind to the pore wall. This technique is being developed for commercial DNA-sequencing applications because it uses minimal samples. It doesn't require fluorescent labels and uses much longer read lengths than conventional methods do.This technique has also been developed to discriminate between polymers based on their size with greater accuracy and speed than gel electrophoresis and chromatography. First, prepare 500 milliliters of a solution of one-molar sodium chloride and 10-millimolar monosodium phosphate in ultrapure water as the electrolyte. It is best to use fresh solutions and samples with this particular set-up.In addition, we found that high-quality deionized water is very important for successfully forming membranes. Next, combine one milligram of lyophilized wild-type monomeric S.aureus alpha hemolysin powder with one milliliter of ultrapure water. Don't forget that working with Staph aureus alpha hemolysin toxin protein can be hazardous.Follow the precautions in the MSDS when performing this procedure. Next, prepare four milliliters of five milligrams per milliliter DPhyPC in endecaine in a glass scintillation vial. Cap the vial with a polytetrafluoroethylene-lined cap and store it at four degrees Celsius for up to a month.After that, dissolve 57.6 milligrams of 12-phosphotungstic acid hydrate in 10 milliliters of the electrolyte to make a two-millimolar polyoxometalate solution. Divide the POM solution into two five-milliliter portions. Use three-molar sodium hydroxide to adjust the pH of one POM solution to 5.5.To begin preparing for the test, assemble the test cell of a planar lipid bilayer electrophysiology apparatus. First, abrade a silver wire with 600-grit sandpaper and soak it in commercially available sodium hypochlorite-based bleach for 10 minutes to make the silver-silver chloride wire electrode. Rinse and dry the wire electrode before inserting it into the quartz capillary of the apparatus.Keep the electrode inside the quartz-nanopore membrane, or QNM, separating the capillary and the reservoir. Then place a cylindrical silver-silver chloride pellet electrode mounted on a silver wire in the reservoir. Connect both electrodes to the amplifier circuit board.Next, open the data acquisition program and start the power supply at zero millivolts. Confirm that no DC current is detected between the electrodes in the empty cell. During this demonstration it's important to watch how the transcapillary pressure can impact membrane formation and subsequent nanopore formation.Without doing these two steps correctly, the experiments won't work. Load about one milliliter of electrolyte into a syringe and connect it to the fluid line connected to the reservoir. Add electrolyte to the reservoir until the face of the QNM is submerged, as indicated by the ionic current between the electrodes saturating the amplifier.If the amplifier does not saturate, unclog the QNM by applying a pop voltage of plus or minus one volt or increasing the capillary pressure by about 300 millimeters of mercury. Use both techniques if necessary. Once the amplifier saturates, withdraw electrolyte from the reservoir until the solution levels drops below the QNM, as indicated by the current returning to zero.To begin the lipid bilayer formation process, raise the electrolyte solution level well above the face of the QNM and note about how much solution that took. Then dip a 10-microliter pipette tip into the DPHyPC solution and draw all visible lipid into the tip. Touch the tip of the pipette to the surface of the electrolyte solution and allow the lipid to flow from the pipette across the air-water interface.Wait two to five minutes for the lipid to spread uniformly across the solution. Next, slowly withdraw the electrolyte until the solution's surface is below the QNM and then slowly add enough electrolyte to raise the solution above the QNM to form the insulating lipid bilayer membrane. If the bilayer does not form after three attempts, apply another portion of lipid as previously described and repeat the process.Once the bilayer seems to have formed, increase the pressure to the capillary to pop the bilayer and then reform it by slowly lowering and raising the solution level in the same way as before. Repeat this process several times to ensure that the QNM is not clogged and a bilayer has formed. Next, thaw an aliquot of alpha hemolysin protein on ice or at room temperature.Fill the reservoir with 250 nanograms of monomeric alpha hemolysin protein and about 250 microliters of ultrapure water. Then, apply a 200 to 400 millivolt bias to induce pore formation. To facilitate pore formation, increase the capillary pressure by 40 to 200 millimeters of mercury to expand the bilayer from the QNM.Once a nanopore forms, reduce the applied bias to the measurement voltage and reduce the pressure to about half of the insertion pressure. To begin the test, readjust the DC-offset voltage to ensure that there is no measured current when the applied potential is set to zero. Next, acquire an ionic current trace for an applied potential of 120 to negative 120 millivolts relative to the reservoir.Confirm that there are no contaminants, which would be indicated by spontaneous current blockades. Add one to six microliters of pH 5.5 two-millimolar POM cluster solution to the reservoir. Apply ionic current time-series measurements at an applied voltage of negative 120 millivolts.The movement of individual anionic phosphotungstic acid molecules through the alpha hemolysin channel produced transient blockades that decreased the mean open-pore ionic current by about 80%The duration and blockade current are both directly related to the particle-pore interaction, allowing ionic species to be differentiated in histograms of the relative blockade depth ratios. At pH 5.5, two peaks were observed with depth ratios of about 0.06 and 0.16. Based on phosphorous NMR, the minor peak was the six-minus phosphotungstate species and the major peak was the seven-minus species.At pH 7.5, the relative concentrations shifted to a higher ratio of the 6-minus species to the seven-minus species. The 20-fold decrease in blockade events relative to pH 5.5 was attributed to degradation to free phosphate and tungstate ions. Fitting the residence-time distributions required multiple exponential functions, indicating multiple types of particle-pore interactions within each ionic species.The shorter residence times at pH 7.5 suggested weaker particle-pore interactions than pH 5.5, consistent with prior studies showing pH-dependent changes in the relative number of fixed charges in or near the alpha hemolysin channel lumen. High-purity deionized water is critical for this particular set-up. A spent organics filter cartridge was the likely cause of our lab being unable to form membranes on the QNMs for months.Individuals new to this particular version of the method might also struggle because the membranes are so small and there is a trick to getting nanopores to form. This method, which was initiated several decades ago, has proven useful for analyzing ions, nucleic acids, and synthetic polymers as well as DNA sequencing. It could also find applications in biophysics and basic cell biology.For example, this procedure can be used to study the physical properties of synthetic polymers and biopolymers to investigate their size, interactions with other molecules, and other important questions.

high-resolution-physical-characterization-single-metallic

Research

JoVE Journal

Chemistry

Preparation and Characterization of SDF-1&#945;-Chitosan-Dextran Sulfate Nanoparticles

Chitosan (CS) and dextran sulfate (DS) are charged polysaccharides (glycans), which form polyelectrolyte complex-based nanoparticles when mixed under appropriate conditions. The glycan nanoparticles are useful carriers for protein factors, which facilitate the in vivo delivery of the proteins and sustain their retention in the targeted tissue. The glycan polyelectrolyte complexes are also ideal for protein delivery, as the incorporation is carried out in aqueous solution, which reduces the likelihood of inactivation of the proteins. Proteins with a heparin-binding site adhere to dextran sulfate readily, and are, in turn, stabilized by the binding. These particles are also less inflammatory and toxic when delivered in vivo. In the protocol described below, SDF-1&#945; (Stromal cell-derived factor-1&#945;), a stem cell homing factor, is first mixed and incubated with dextran sulfate. Chitosan is added to the mixture to form polyelectrolyte complexes, followed by zinc sulfate to stabilize the complexes with zinc bridges. The resultant SDF-1&#945;-DS-CS particles are measured for size (diameter) and surface charge (zeta potential). The amount of the incorporated SDF-1&#945; is determined, followed by measurements of its in vitro release rate and its chemotactic activity in a particle-bound form.

Preparation and Characterization of SDF-1&amp;#945;-Chitosan-Dextran Sulfate Nanoparticles

The objective of this protocol is to incorporate SDF-1&#945;, a stem cell homing factor, into dextran sulfate-chitosan nanoparticles. The resultant particles are measured for their size and zeta potential, as well as the content, activity, and in vitro release rate of SDF-1&#945; from the nanoparticles.

Chitosan (CS) and dextran sulfate (DS) are charged polysaccharides (glycans), which form polyelectrolyte complex-based nanoparticles when mixed under ...

Synthesis, Characterization, and Functionalization of Hybrid Au/CdS and Au/ZnS Core/Shell Nanoparticles

Plasmonic nanoparticles are an attractive material for light harvesting applications due to their easily modified surface, high surface area and large extinction coefficients which can be tuned across the visible spectrum. Research into the plasmonic enhancement of optical transitions has become popular, due to the possibility of altering and in some cases improving photo-absorption or emission properties of nearby chromophores such as molecular dyes or quantum dots. The electric field of the plasmon can couple with the excitation dipole of a chromophore, perturbing the electronic states involved in the transition and leading to increased absorption and emission rates. These enhancements can also be negated at close distances by energy transfer mechanism, making the spatial arrangement of the two species critical. Ultimately, enhancement of light harvesting efficiency in plasmonic solar cells could lead to thinner and, therefore, lower cost devices. The development of hybrid core/shell particles could offer a solution to this issue. The addition of a dielectric spacer between a gold nanoparticles and a chromophore is the proposed method to control the exciton plasmon coupling strength and thereby balance losses with the plasmonic gains. A detailed procedure for the coating of gold nanoparticles with CdS and ZnS semiconductor shells is presented. The nanoparticles show high uniformity with size control in both the core gold particles and shell species allowing for a more accurate investigation into the plasmonic enhancement of external chromophores.

The synthesis of uniform gold nanoparticles coated with semiconductor shells of CdS or ZnS is performed. The semiconductor coating is conducted by first depositing a silver sulfide shell and exchanging the silver cations for zinc or cadmium cations.

Plasmonic nanoparticles are an attractive material for light harvesting applications due to their easily modified surface, high surface area and large ...

Synthesis and Characterization of Supramolecular Colloids

Control over colloidal assembly is of utmost importance for the development of functional colloidal materials with tailored structural and mechanical properties for applications in photonics, drug delivery and coating technology. Here we present a new family of colloidal building blocks, coined supramolecular colloids, whose self-assembly is controlled through surface-functionalization with a benzene-1,3,5-tricarboxamide (BTA) derived supramolecular moiety. Such BTAs interact via directional, strong, yet reversible hydrogen-bonds with other identical BTAs. Herein, a protocol is presented that describes how to couple these BTAs to colloids and how to quantify the number of coupling sites, which determines the multivalency of the supramolecular colloids. Light scattering measurements show that the refractive index of the colloids is almost matched with that of the solvent, which strongly reduces the van der Waals forces between the colloids. Before photo-activation, the colloids remain well dispersed, as the BTAs are equipped with a photo-labile group that blocks the formation of hydrogen-bonds. Controlled deprotection with UV-light activates the short-range hydrogen-bonds between the BTAs, which triggers the colloidal self-assembly. The evolution from the dispersed state to the clustered state is monitored by confocal microscopy. These results are further quantified by image analysis with simple routines using ImageJ and Matlab. This merger of supramolecular chemistry and colloidal science offers a direct route towards light- and thermo-responsive colloidal assembly encoded in the surface-grafted monolayer.

A protocol for the synthesis and characterization of colloids coated with supramolecular moieties is described. These supramolecular colloids undergo self-assembly upon the activation of the hydrogen-bonds between the surface-anchored molecules by UV-light.

Control over colloidal assembly is of utmost importance for the development of functional colloidal materials with tailored structural and mechanical ...

Rapid High-throughput Species Identification of Botanical Material Using Direct Analysis in Real Time High Resolution Mass Spectrometry

We demonstrate that direct analysis in real time-high resolution mass spectrometry can be used to produce mass spectral profiles of botanical material, and that these chemical fingerprints can be used for plant species identification. The mass spectral data can be acquired rapidly and in a high throughput manner without the need for sample extraction, derivatization or pH adjustment steps. The use of this technique bypasses challenges presented by more conventional techniques including lengthy chromatography analysis times and resource intensive methods. The high throughput capabilities of the direct analysis in real time-high resolution mass spectrometry protocol, coupled with multivariate statistical analysis processing of the data, provide not only class characterization of plants, but also yield species and varietal information. Here, the technique is demonstrated with two psychoactive plant products, Mitragyna speciosa (Kratom) and Datura (Jimsonweed), which were subjected to direct analysis in real time-high resolution mass spectrometry followed by statistical analysis processing of the mass spectral data. The application of these tools in tandem enabled the plant materials to be rapidly identified at the level of variety and species.

A method for species identification of botanical material by direct analysis in real time-high resolution mass spectrometry and multivariate statistical analysis is presented.

We demonstrate that direct analysis in real time-high resolution mass spectrometry can be used to produce mass spectral profiles of botanical material, ...

High Pressure Single Crystal Diffraction at PX^2

In this report we describe detailed procedures for carrying out single crystal X-ray diffraction experiments with a diamond anvil cell (DAC) at the GSECARS 13-BM-C beamline at the Advanced Photon Source. The DAC program at 13-BM-C is part of the Partnership for Extreme Xtallography (PX^2) project. BX-90 type DACs with conical-type diamond anvils and backing plates are recommended for these experiments. The sample chamber should be loaded with noble gas to maintain a hydrostatic pressure environment. The sample is aligned to the rotation center of the diffraction goniometer. The MARCCD area detector is calibrated with a powder diffraction pattern from LaB6. The sample diffraction peaks are analyzed with the ATREX software program, and are then indexed with the RSV software program. RSV is used to refine the UB matrix of the single crystal, and with this information and the peak prediction function, more diffraction peaks can be located. Representative single crystal diffraction data from an omphacite (Ca0.51Na0.48)(Mg0.44Al0.44Fe2+0.14Fe3+0.02)Si2O6 sample were collected. Analysis of the data gave a monoclinic lattice with P2/n space group at 0.35 GPa, and the lattice parameters were found to be: a = 9.496 &#177;0.006 &#197;, b = 8.761 &#177;0.004 &#197;, c = 5.248 &#177;0.001 &#197;, &#946; = 105.06 &#177;0.03&#186;, &#945; = &#947; = 90&#186;.

In this report, we describe detailed procedures for carrying out single crystal X-ray diffraction experiments with a diamond anvil cell at the GSECARS 13-BM-C beamline at the Advanced Photon Source. ATREX and RSV programs are used to analyze the data.

In this report we describe detailed procedures for carrying out single crystal X-ray diffraction experiments with a diamond anvil cell (DAC) at the ...

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.

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.

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

Real-time Breath Analysis by Using Secondary Nanoelectrospray Ionization Coupled to High Resolution Mass Spectrometry

Exhaled volatile organic compounds (VOCs) have aroused considerable interest, since they can serve as biomarkers for disease diagnosis and environmental exposure in a non-invasive manner. In this work, we present a protocol to characterize the exhaled VOCs in real time by using secondary nanoelectrospray ionization coupled to high resolution mass spectrometry (Sec-nanoESI-HRMS). The homemade Sec-nanoESI source was readily set up based on a commercial nanoESI source. Hundreds of peaks were observed in the background-subtracted mass spectra of exhaled breath, and the mass accuracy values are -4.0-13.5 ppm and -20.3-1.3 ppm in the positive and negative ion detection modes, respectively. The peaks were assigned with accurate elemental composition according to the accurate mass and isotopic pattern. Less than 30 s is used for one exhalation measurement, and it takes approximately 7 min for six replicated measurements.

A protocol for characterizing chemical composition of exhaled breath in real time by using secondary nanoelectrospray ionization coupled to high resolution mass spectrometry is demonstrated.

Exhaled volatile organic compounds (VOCs) have aroused considerable interest, since they can serve as biomarkers for disease diagnosis and environmental ...

Synthesis and Characterization of Amphiphilic Gold Nanoparticles

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

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

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

A Continuous-flow Photocatalytic Reactor for the Precisely Controlled Deposition of Metallic Nanoparticles

In this work, a novel photocatalytic reactor for the pulsed and controlled excitation of the photocatalyst and the precise deposition of metallic nanoparticles is developed. Guidelines for the replication of the reactor and its operation are provided in detail. Three different composite systems (Pt/graphene, Pt/TiO2, and Au/TiO2) with monodisperse and uniformly distributed particles are produced by this reactor, and the photodeposition mechanism, as well as the synthesis optimization strategy, are discussed. The synthesis methods and their technical aspects are described comprehensively. The role of the ultraviolet (UV) dose (in each excitation pulse) on the photodeposition process is investigated and the optimum values for each composite system are provided.

For a continuous and scalable synthesis of noble-metal-based nanocomposites, a novel photocatalytic reactor is developed and its structure, operation principles, and product quality optimization strategies are described.

In this work, a novel photocatalytic reactor for the pulsed and controlled excitation of the photocatalyst and the precise deposition of metallic ...

A Closed-Type Wireless Nanopore Electrode for Analyzing Single Nanoparticles

Measuring the intrinsic features of single nanoparticles by nanoelectrochemistry holds deep fundamental importance and has potential impacts in nanoscience. However, electrochemically analyzing single nanoparticles is challenging, as the sensing nanointerface is uncontrollable. To address this challenge, we describe here the fabrication and characterization of a closed-type wireless nanopore electrode (WNE) that exhibits a highly controllable morphology and outstanding reproducibility. The facile fabrication of WNE enables the preparation of well-defined nanoelectrodes in a general chemistry laboratory without the use of a clean room and expensive equipment. One application of a 30 nm closed-type WNE in analysis of single gold nanoparticles in the mixture is also highlighted, which shows a high current resolution of 0.6 pA and high temporal resolution of 0.01 ms. Accompanied by their excellent morphology and small diameters, more potential applications of closed-type WNEs can be expanded from nanoparticle characterization to single molecule/ion detection and single-cell probing.

Here, we present a protocol for fabrication of a closed-type wireless nanopore electrode and subsequent electrochemical measurement of single nanoparticle collisions.