Name: manganese oxide nanoparticle synthesis by thermal decomposition of manganese(ii) acetylacetonate
Uploaded: 2020-06-18T15:00:00
Description: Watch this Scientific Journal Video about Manganese Oxide Nanoparticle Synthesis by Thermal Decomposition of ManganeseII Acetylacetonate at JoVE.com

This work was supported by WVU Chemical and Biomedical Engineering Department startup funds (M.F.B.). The authors would like to thank Dr. Marcela Redigolo for guidance on grid preparation and image capture of nanoparticles with TEM, Dr. Qiang Wang for support on evaluating XRD and FTIR spectra, Dr. John Zondlo and Hunter Snoderly for programming and integrating the temperature controller into the nanoparticle synthesis protocol, James Hall for his assistance in assembly of the nanoparticle synthesis setup, Alexander Pueschel and Jenna Vito for aiding in quantification of MnO nanoparticle diameters from TEM images, and the WVU Shared Research Facility for use of the TEM, XRD, and FTIR.

1. Glassware and tubing assembly &#8211; to be performed only the first time
NOTE: Figure 1 shows the experimental setup for MnO nanoparticle synthesis with numbered tubing connections. Figure S1 shows the same setup with the main glassware components labeled. If there is a mismatch between the chemical resistant tubing and the glass connection size, cover the glass connection first with a short piece of smaller tubing before adding the...

The protocol herein describes a facile, one-pot synthesis of MnO nanoparticles using Mn(II) ACAC, DE, and OA. Mn(II) ACAC is utilized as the starting material to provide a source of Mn2+ for MnO nanoparticle formation. The starting material can be easily substituted to enable production of other metal oxide nanoparticles. For example, when iron(III) ACAC is applied, Fe3O4 nanoparticles can be generated using the same nanoparticle synthesis equipment and protocol described<sup class="xref"...

Metal oxide nanoparticles possess magnetic, electric, and catalytic properties, which have been applied in bioimaging1,2,3, sensor technologies4,5, catalysis6,7,8, energy storage9, and water purification10. Within the biomedical field, iron oxide nanoparticles and manganese oxide (MnO) nanoparticles have proven utility as contrast agents in magnetic resonance imaging (MRI)1,2. Iron oxide nanoparticles produce robust negative contrast on T2* MRI and are powerful enough to visualize single labeled cells in vivo11,12,13; however, the negative MRI signal cannot be modulated and remains &#8220;ON&#8221; throughout the duration of typical experiments. Due to endogenous iron present in the liver, bone marrow, blood and spleen, the negative contrast generated from iron oxide nanoparticles may be difficult to interpret. MnO nanoparticles, on the other hand, are responsive to a drop in pH. MRI signal for MnO nanoparticles can transition from &#8220;OFF&#8221; to &#8220;ON&#8221; once the nanoparticles are internalized inside the low pH endosomes and lysosomes of the target cell such as a cancer cell14,15,16,17,18,19. The positive contrast on T1 MRI produced from the dissolution of MnO to Mn2+ at low pH is unmistakable and can improve cancer detection specificity by only lighting up at the target site within a malignant tumor. Control over nanoparticle size, morphology and composition is crucial to achieve maximum MRI signal from MnO nanoparticles. Herein, we describe how to synthesize and characterize MnO nanoparticles using the thermal decomposition method and note different strategies for fine-tuning nanoparticle properties by altering variables in the synthesis process. This protocol can be easily modified to produce other magnetic nanoparticles such as iron oxide nanoparticles.
MnO nanoparticles have been produced by a variety of techniques including thermal decomposition20,21,22,23,24,25, hydro/solvothermal26,27,28,29, exfoliation30,31,32,33,34, permanganates reduction35,36,37,38, and adsorption-oxidation39,40,41,42. Thermal decomposition is the most commonly used technique which involves dissolving manganese precursors, organic solvents, and stabilizing agents at high temperatures (180 &#8211; 360 &#176;C) under the presence of an inert gaseous atmosphere to form MnO nanoparticles43. Out of all of these techniques, thermal decomposition is the superior method to generate a variety of MnO nanocrystals of pure phase (MnO, Mn3O4 and Mn2O3) with a narrow size distribution. Its versatility is highlighted through the ability to tightly control nanoparticle size, morphology and composition by altering reaction time44,45,46, temperature44,47,48,49, types/ratios of reactants20,45,47,48,50 and inert gas47,48,50 used. The main limitations of this method are the requirement for high temperatures, the oxygen-free atmosphere, and the hydrophobic coating of the synthesized nanoparticles, which requires further modification with polymers, lipids or other ligands to increase solubility for biological applications14,51,52,53.
Besides thermal decomposition, the hydro/solvothermal method is the only other technique that can produce a variety of MnO phases including MnO, Mn3O4, and MnO2; all other strategies only form MnO2 products. During hydro/solvothermal synthesis, precursors such as Mn(II) stearate54,55 and Mn(II) acetate27 are heated to between 120-200 &#176;C over several hours to achieve nanoparticles with a narrow size distribution; however, specialized reaction vessels are required and reactions are performed at high pressures. In contrast, the exfoliation strategy involves treatment of a layered or bulk material to promote dissociation into 2D single layers. Its main advantage is in producing MnO2 nanosheets, but the synthesis process is long requiring several days and the resulting size of the sheets is difficult to control. Alternatively, permanganates such as KMnO4 can react with reducing agents such as oleic acid56,57, graphene oxide58 or poly(allylamine hydrochloride)59 to create MnO2 nanoparticles. Use of KMnO4 facilitates nanoparticle formation at room temperature over a few minutes to hours within aqueous conditions43. Unfortunately, the rapid synthesis and nanoparticle growth makes it challenging to finely control resulting nanoparticle size. MnO2 nanoparticles can also be synthesized using adsorption-oxidation whereby Mn2+ ions are adsorbed and oxidized to MnO2 by oxygen under basic conditions. This method will produce small MnO2 nanoparticles with a narrow size distribution at room temperature over several hours in aqueous media; however the requirement for adsorption of Mn2+ ions and alkali conditions limits its widespread application43.
Of the MnO nanoparticle synthesis methods discussed, thermal decomposition is the most versatile to generate different monodisperse pure phase nanocrystals with control over nanoparticle size, shape and composition without requiring specialized synthesis vessels. In this manuscript, we describe how to synthesize MnO nanoparticles by thermal decomposition at 280 &#176;C using manganese(II) acetylacetonate (Mn(II) ACAC) as the source of Mn2+ ions, oleylamine (OA) as the reducing agent and stabilizer, and dibenzyl ether (DE) as the solvent under a nitrogen atmosphere. The glassware and tubing setup for nanoparticle synthesis is explained in detail. One advantage of the technique is the inclusion of a temperature controller, thermocouple probe, and heating mantle to enable precise control over the heating rate, peak temperature, and reaction times at each temperature to fine-tune nanoparticle size and composition. Herein, we show how nanoparticle size can also be manipulated by changing the ratio of OA to DE. Additionally, we demonstrate how to prepare nanoparticle samples and measure nanoparticle size, bulk composition and surface composition using transmission electron microscopy (TEM), x-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR), respectively. Further guidance is included on how to analyze the collected images and spectra from each instrument. To generate uniformly shaped MnO nanoparticles, a stabilizer and adequate nitrogen flow must be present; XRD and TEM results are shown for undesired products formed in the absence of OA and under low nitrogen flow. In the Discussion section, we highlight crucial steps in the protocol, metrics to determine successful nanoparticle synthesis, further variation of the decomposition protocol to modify nanoparticle properties (size, morphology and composition), troubleshooting and limitations of the method, and applications of MnO nanoparticles as contrast agents for biomedical imaging.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Chemicals and Gases</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Benzyl ether (DE)</td>
			<td>Acros Organics</td>
			<td>AC14840-0010</td>
			<td>Concentration: 99%, 1 L</td>
		</tr>
		<tr>
			<td>Drierite</td>
			<td>W. A. Hammond Drierite Co. LTD</td>
			<td>23001</td>
			<td>Drierite 8 mesh, 1 lb</td>
		</tr>
		<tr>
			<td>Ethanol</td>
			<td>Decon Laboratories&#160;</td>
			<td>2701</td>
			<td>200 proof, 4 x 3.7 L</td>
		</tr>
		<tr>
			<td>Hexane</td>
			<td>Macron Fine Chemicals</td>
			<td>5189-08</td>
			<td>Concentration:&#160; &#8805;98.5%, 4 L</td>
		</tr>
		<tr>
			<td>Hydrochloric acid</td>
			<td>VWR</td>
			<td>BDH3030-2.5LPC</td>
			<td>Concentration: 36.5 - 38.0 % ACS, 2.5 L</td>
		</tr>
		<tr>
			<td>Manganese (II) acetyl acetonate (Mn(II)ACAC)</td>
			<td>Sigma Aldrich</td>
			<td>245763-100G</td>
			<td>100 g</td>
		</tr>
		<tr>
			<td>Nitrogen gas tank</td>
			<td>Airgas</td>
			<td>NI R300</td>
			<td>Research 5.7 grade nitrogen, size 300 cylinder</td>
		</tr>
		<tr>
			<td>Nitrogen regulator</td>
			<td>Airgas</td>
			<td>Y11244D580-AG</td>
			<td>Single stage brass 0-100 psi analytical cylinder regulator CGA-580 with needle outlet</td>
		</tr>
		<tr>
			<td>Oleylamine (OA)</td>
			<td>Sigma Aldrich</td>
			<td>O7805-500G</td>
			<td>Concentration: 70%, technical grade, 500 g</td>
		</tr>
		<tr>
			<td>Silicone oil</td>
			<td>Beantown Chemical</td>
			<td>221590-100G</td>
			<td>100 g</td>
		</tr>
		<tr>
			<td>Equipment</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Centrifuge</td>
			<td>Beckman-Coulter</td>
			<td>Avanti J-E</td>
			<td>JA-20 fixed-angle aluminum rotor, 8 x 50 mL, 48,400 x g</td>
		</tr>
		<tr>
			<td>Hemisphere mantle</td>
			<td>Ace Glass Inc.</td>
			<td>12035-17</td>
			<td>115 V, 270 W, 500 mL, temperature up to 450 &#176;C</td>
		</tr>
		<tr>
			<td>Hot plate stirrer</td>
			<td>VWR</td>
			<td>97042-642</td>
			<td>120 V, 1000 W, 8.3 A, ceramic top</td>
		</tr>
		<tr>
			<td>Temperature controller</td>
			<td>Yokogawa Electric Corporation</td>
			<td>UP351</td>
			<td></td>
		</tr>
		<tr>
			<td>Temperature probe</td>
			<td>Omega</td>
			<td>KMQXL-040G-12</td>
			<td>Immersion probe, temperature up to 1335 &#176;C</td>
		</tr>
		<tr>
			<td>Vacuum oven</td>
			<td>Fisher Scientific</td>
			<td>282A</td>
			<td>120 V, 1800 W, temperature up to 280 &#176;C</td>
		</tr>
		<tr>
			<td>Vortex mixer</td>
			<td>Fisher Scientific</td>
			<td>02-215-365</td>
			<td>120 V, 50/60 Hz, 150 W</td>
		</tr>
		<tr>
			<td>Water bath sonicator</td>
			<td>Fisher Scientific</td>
			<td>FS30H</td>
			<td>Ultrasonic power 130 W, 3.7 L tank</td>
		</tr>
		<tr>
			<td>Tools and Materials</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Dumont tweezer</td>
			<td>Electron Microscopy Sciences</td>
			<td>72703D</td>
			<td>Style 5/45, Dumoxel, 109 mm, for picking up TEM grids</td>
		</tr>
		<tr>
			<td>Dumont reverse tweezer</td>
			<td>Ted Pella</td>
			<td>5748</td>
			<td>Style N2a, 118 mm, NM-SS, self-closing, holding TEM grids in place for sample preparation</td>
		</tr>
		<tr>
			<td>Mortar and pestle</td>
			<td>Amazon</td>
			<td>BS0007</td>
			<td>BIPEE agate mortar and pestle, 70 X 60 X 15 mm labware</td>
		</tr>
		<tr>
			<td>Nalgene&#8482; Oak Ridge tubes</td>
			<td>ThermoFisher Scientific</td>
			<td>3139-0050</td>
			<td>Polypropylene copolymer, 50,000 x g, 50 mL, pack of 10</td>
		</tr>
		<tr>
			<td>Scintillation vials</td>
			<td>Fisher Scientific</td>
			<td>03-337-4</td>
			<td>20 mL vials with white caps, case of 500</td>
		</tr>
		<tr>
			<td>TEM grids</td>
			<td>Ted Pella</td>
			<td>01813-F</td>
			<td>Carbon Type-B, 300 mesh, copper, pack of 50</td>
		</tr>
		<tr>
			<td>Glassware Setup</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>4-neck round bottom flask</td>
			<td>Chemglass Life Sciences</td>
			<td>CG-1534-01</td>
			<td>24/40 joint, 500 mL, #7 chem thread for thermometers</td>
		</tr>
		<tr>
			<td>6-port vacuum manifold</td>
			<td>Chemglass Life Sciences</td>
			<td>CG-4430-02</td>
			<td>480 nm, 6 ports, 4 mm PTFE stopcocks</td>
		</tr>
		<tr>
			<td>Adapter</td>
			<td>Chemglass Life Sciences</td>
			<td>CG-1014-01</td>
			<td>24/40 inner joint, 90&#176;</td>
		</tr>
		<tr>
			<td>Condenser</td>
			<td>Chemglass Life Sciences</td>
			<td>CG-1216-03</td>
			<td>24/40 joint, 365 mm, 250 mm jacket length</td>
		</tr>
		<tr>
			<td>Drierite 26800 drying column</td>
			<td>Cole-Parmer&#160;</td>
			<td>EW-07193-00</td>
			<td>200 L/hr, 90 psi</td>
		</tr>
		<tr>
			<td>Funnel</td>
			<td>Chemglass Life Sciences</td>
			<td>CG-1720-L-02</td>
			<td>24/40 joint, 100 powder funnel, 195 mm OAL</td>
		</tr>
		<tr>
			<td>Interlocked worm gear hose clamp</td>
			<td>Grainger</td>
			<td>16P292</td>
			<td>1/2&#34; wide stainless steel clamp, 3/8&#34; to 7/8&#34; diameter, to secure condenser tubing, 10 pack&#160;</td>
		</tr>
		<tr>
			<td>Keck clips</td>
			<td>Kemtech America Inc</td>
			<td>CS002440</td>
			<td>24/40 joint</td>
		</tr>
		<tr>
			<td>Metal claw clamp</td>
			<td>Fisher Scientific</td>
			<td>05-769-7Q</td>
			<td>22cm, three-prong extension clamps</td>
		</tr>
		<tr>
			<td>Metal claw clamp holder</td>
			<td>Fisher Scientific</td>
			<td>05-754Q</td>
			<td>Clamp regular holder</td>
		</tr>
		<tr>
			<td>Mineral oil bubbler</td>
			<td>Kemtech America Inc</td>
			<td>B257040</td>
			<td>185 mm</td>
		</tr>
		<tr>
			<td>Rotovap trap</td>
			<td>Chemglass Life Sciences</td>
			<td>CG-1319-02</td>
			<td>24/40 joints, 100 mL, self washing rotary evaporator</td>
		</tr>
		<tr>
			<td>Rubber stopper</td>
			<td>Chemglass Life Sciences</td>
			<td>CG-3022-98</td>
			<td>24/40 joints, red rubber</td>
		</tr>
		<tr>
			<td>Tubing for air/water&#160;</td>
			<td>McMaster-Carr</td>
			<td>6516T21</td>
			<td>Clear Tygon PVC for air/water, B-44-3, 1/4&#34; ID, 1/16&#34; wall, 25 ft</td>
		</tr>
		<tr>
			<td>Tubing for air/water&#160;</td>
			<td>McMaster-Carr</td>
			<td>6516T26</td>
			<td>Clear Tygon PVC for air/water, B-44-3, 3/8&#34; ID, 1/16&#34; wall, 25 ft</td>
		</tr>
		<tr>
			<td>Tubing for chemicals</td>
			<td>McMaster-Carr</td>
			<td>5155T34</td>
			<td>Clear Tygon PVC for chemicals, E-3603, 3/8&#34; ID, 1/16&#34; wall, 50 ft</td>
		</tr>
		<tr>
			<td>Analysis Programs</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>XRD analysis program</td>
			<td>Malvern Panalytical</td>
			<td>N/A</td>
			<td>X&#39;Pert HighScore Plus</td>
		</tr>
		<tr>
			<td>FTIR analysis program</td>
			<td>Varian, Inc.</td>
			<td>N/A</td>
			<td>Varian Resolutions Pro</td>
		</tr>
	</tbody>
</table>

manganese oxide nanoparticle synthesis by thermal decomposition of manganese(ii) acetylacetonate

For biomedical applications, metal oxide nanoparticles such as iron oxide and manganese oxide (MnO), have been used as biosensors and contrast agents in magnetic resonance imaging (MRI). While iron oxide nanoparticles provide constant negative contrast on MRI over typical experimental timeframes, MnO generates switchable positive contrast on MRI through dissolution of MnO to Mn2+ at low pH within cell endosomes to &#8216;turn ON&#8217; MRI contrast. This protocol describes a one-pot synthesis of MnO nanoparticles formed by thermal decomposition of manganese(II) acetylacetonate in oleylamine and dibenzyl ether. Although running the synthesis of MnO nanoparticles is simple, the initial experimental setup can be difficult to reproduce if detailed instructions are not provided. Thus, the glassware and tubing assembly is first thoroughly described to allow other investigators to easily reproduce the setup. The synthesis method incorporates a temperature controller to achieve automated and precise manipulation of the desired temperature profile, which will impact resulting nanoparticle size and chemistry. The thermal decomposition protocol can be readily adapted to generate other metal oxide nanoparticles (e.g., iron oxide) and to include alternative organic solvents and stabilizers (e.g., oleic acid). In addition, the ratio of organic solvent to stabilizer can be changed to further impact nanoparticle properties, which is shown herein. Synthesized MnO nanoparticles are characterized for morphology, size, bulk composition, and surface composition through transmission electron microscopy, X-ray diffraction, and Fourier-transform infrared spectroscopy, respectively. The MnO nanoparticles synthesized by this method will be hydrophobic and must be further manipulated through ligand exchange, polymeric encapsulation, or lipid capping to incorporate hydrophilic groups for interaction with biological fluids and tissues.

To confirm successful synthesis, MnO nanoparticles should be assayed for size and morphology (TEM), bulk composition (XRD), and surface composition (FTIR). Figure 2 shows representative TEM images of MnO nanoparticles synthesized using decreasing ratios of oleylamine (OA, the stabilizer) to dibenzyl ether (DE, the organic solvent): 60:0, 50:10, 40:20, 30:30, 20:40, 10:50. Ideal TEM images consist of individual nanoparticles (shown as dark rounded octagons in Figure 2</st...

Watch this Scientific Journal Video about Manganese Oxide Nanoparticle Synthesis by Thermal Decomposition of ManganeseII Acetylacetonate at JoVE.com

Manganese Oxide Nanoparticle Synthesis by Thermal Decomposition of ManganeseII Acetylacetonate

This protocol details a facile, one-pot synthesis of manganese oxide (MnO) nanoparticles by thermal decomposition of manganese(II) acetylacetonate in the presence of oleylamine and dibenzyl ether. MnO nanoparticles have been utilized in diverse applications including magnetic resonance imaging, biosensing, catalysis, batteries, and waste water treatment.

Manganese Oxide Nanoparticle Synthesis by Thermal Decomposition of Manganese(II) Acetylacetonate

For biomedical applications, metal oxide nanoparticles such as iron oxide and manganese oxide (MnO), have been used as biosensors and contrast agents in ...

Compared to other synthesis methods, thermal decomposition generates uniform metal oxide nano-particles with tight control over particle size, shape, and chemical composition. This technique is an easy one pot synthesis that uses three reagents, a metal precursor, an organic solvent and a stabilizer. It can produce different types of nano-particles including manganese oxide and iron oxide.Demonstrating the procedure will be Celia Martinez De La Torre, a graduate research assistant in my laboratory. Before beginning an experiment, place a four neck 500 milliliter round bottom flask onto the heating mantle. And secure the middle neck with a metal claw clamp.Add magnetic stir bar to the round bottom flask and place a glass funnel in the middle neck of the flask. Make sure the safety and input stopcocks are open. Add 1.51 grams of manganese II acetylacetonate through the funnel into the round bottom flask.And add 20 milliliters of allylamine and 40 milliliters of di-benzyl ether to the flask. Attach a condenser to the left neck of the flask and use a metal claw clamp to secure the condenser to the flask. Add the glass elbow adapter to the top of the condenser and attach the rotovap trap to the right neck of the round bottom flask.Lace the glass elbow adaptor on top of the rotovap trap. And fold the rubber stopper on the middle neck of the round bottom flask. So the sides cover the neck of the flask.Use plastic conical joint clips to secure the glassware neck connections. And place the temperature probe into the smallest neck in the brown bottom flask. Use a neck cap and an O-ring to tighten and secure the probe and the reaction mixture without touching the glass.And connect the temperature probe to the input of the temperature controller. Connect the heating mantle to the output of the temperature controller and turn on the stir plate to begin vigorous stirring of the solution. Open the air free nitrogen tank to slowly begin flowing nitrogen into the system and use the regulator to adjust the flow until a steady stream of bubbles forms in the middle of mineral oil bubbler.Then turn on the cold water in the fume hood to the condenser and close this For nanoparticle synthesis turn on the temperature controller to start the reaction. And monitor the changes that occur in the temperature throughout the experiment. At 280 degrees Celsius turn off the nitrogen tank and close the right stopcock.The temperature will be held at 280 degrees Celsius for 30 minutes. During this time, the reaction color will change to a green tone indicating manganese oxide formation. When the reaction is cool to room temperature, turn off the temperature controller, stir plate and water and decant the manganese oxide nano-particles solution into a clean 500 milliliter beaker.Add two times the volume of 200 proof ethanol to the beaker. And split the nanoparticle mixture equally between four centrifuge tubes. After capping sediment the nano-particles by centrifugation and discard the brown clear supernatant.Add five milliliters of hexane to each tube. And re-suspend the nano-particles by vortexing. Add any extra nano-particles solution and the 200 proof ethanol to the tubes until each is three quarters full and centrifuge the nano-particles again.Re-suspend each tube of nano-particles in five milliliters of hexane with vortexing and pool the four tubes of solution into two tubes. Bring the volume in each tube up to three quarters full with 200 proof ethanol and centrifuge the nano-particles again. Discard the nearly colorless and clear a supernatant.And re-suspend the nano-particles in five milliliters of hexane with vortexing. Pour the entire volume of both tubes into a 20 milliliter glass scintillation vile. And evaporate the hexane in a fume hood overnight.The next morning place the vile at 100 degrees Celsius for 24 hours to dry out the nano-particles before using a spatula to break up the powder. To assess the nano-particle size and surface morphology, use a mortar and pestle to pulverize the manganese oxide nano-particles into a thin powder, and add five milligrams of the powder to a 15 milliliter conical centrifuge tube. Add 10 milliliters of 200 proof ethanol to the tube and bath sonicate the nanoparticle mixture for five minutes until the nano-particles are fully re-suspended.Immediately upon re-suspension, add three five microliter drops of nano-particle solution into a 300 mesh copper grid support film of carbon type B.After air drying assess the nanoparticle shape and size by TEM according to standard protocols with a beam strength of 200 kilovolts a spot size of one and a 300 X magnification. To determine the nanoparticle bulk composition, use a spatula to transfer some of the fine nanoparticle powder onto an x-ray diffraction sample holder. And collect the x-ray diffraction spectra of the manganese oxide particles according to standard protocols.Use a two theta range from 10 to 110 degrees to view the manganese oxide and manganese to three oxide peaks. To determine the nanoparticle surface composition add dry manganese oxide nanoparticle powder to an FTIR sample holder and collect the FTIR spectrum of the nano-particles according to standard protocols between the 4, 400 inverse centimeter wavelength range with a four centimeter resolution. Ideal TEM images consist of individual dark rounded octagonal nano-particles with minimal overlap.If a high concentration of manganese oxide nano-particles are suspended in ethanol, or too many drops of nano-particles suspension are added to the T and grid each image will consist of large agglomerations of nano-particles. If a low nano-particle concentration is prepared in ethanol the nano-particles will be separated but too sparsely distributed on the TEM grid. Overall, a decrease in the ratio of allylamine di benzyl ether yields smaller manganese oxide nano-particles with less variation in size, except when allylamine alone is used producing similar size nano-particles to the 30 30 ratio.X-ray diffraction can be used to determine the crystal structure and phase of the nano-particles. The x-ray diffraction sample peaks can then be matched to x-ray diffraction peaks from known compounds. To facilitate estimation of the nanoparticle composition, here FTIR spectrum manganese oxide nano-particles after background correction can be observed.All spectra show the symmetric and asymmetric methylene peaks associated with groups. In addition to the aminal radicle bending vibration peaks associated with groups. Furthermore, all nanoparticle FTIR spectra contain manganese oxygen and manganese oxygen manganese bond vibrations around 600 inverse centimeters which confirmed the composition found through x-ray diffraction.To ensure an accurate temperature reading, the temperature probe do not touch the glass. The level of silicone oil and rate of nitrogen flow should also be carefully monitored. Metal oxide nano-particles can be made hydrophilic through polymer or lipid encapsulation to enhance their biocompatibility.Targeting agents can be also touch to light nanoparticle accumulation in vivo.

manganese-oxide-nanoparticle-synthesis-thermal-decomposition

Research

JoVE Journal

Bioengineering

Synthesis, Assembly, and Characterization of Monolayer Protected Gold Nanoparticle Films for Protein Monolayer Electrochemistry

Colloidal gold nanoparticles protected with alkanethiolate ligands called monolayer protected gold clusters (MPCs) are synthesized and subsequently incorporated into film assemblies that serve as adsorption platforms for protein monolayer electrochemistry (PME). PME is utilized as the model system for studying electrochemical properties of redox proteins by confining them to an adsorption platform at a modified electrode, which also serves as a redox partner for electron transfer (ET) reactions. Studies have shown that gold nanoparticle film assemblies of this nature provide for a more homogeneous protein adsorption environment and promote ET without distance dependence compared to the more traditional systems modified with alkanethiol self-assembled monolayers (SAM).1-3 In this paper, MPCs functionalized with hexanethiolate ligands are synthesized using a modified Brust reaction4 and characterized with ultraviolet visible (UV-Vis) spectroscopy, transmission electron microscopy (TEM), and proton (1H) nuclear magnetic resonance (NMR). MPC films are assembled on SAM modified gold electrode interfaces by using a "dip cycle" method of alternating MPC layers and dithiol linking molecules. Film growth at gold electrode is tracked electrochemically by measuring changes to the double layer charging current of the system. Analogous films assembled on silane modified glass slides allow for optical monitoring of film growth and cross-sectional TEM analysis provides an estimated film thickness. During film assembly, manipulation of the MPC ligand protection as well as the interparticle linkage mechanism allow for networked films, that are readily adaptable, to interface with redox protein having different adsorption mechanism. For example, Pseudomonas aeruginosa azurin (AZ) can be adsorbed hydrophobically to dithiol-linked films of hexanethiolate MPCs and cytochrome c (cyt c) can be immobilized electrostatically at a carboxylic acid modified MPC interfacial layer. In this report, we focus on the film protocol for the AZ system exclusively. Investigations involving the adsorption of proteins on MPC modified synthetic platforms could further the understanding of interactions between biomolecules and man-made materials, and consequently aid the development of biosensor schemes, ET modeling systems, and synthetic biocompatible materials.5-8

Alkanethiolate stabilized gold colloids known as monolayer protected clusters (MPCs) are synthesized, characterized, and assembled into thin films as an adsorption interface for protein monolayer electrochemistry of simple redox protein like Pseudomonas aeruginosa azurin (AZ) and cytochrome c (cyt c).

Colloidal gold nanoparticles protected with alkanethiolate ligands called monolayer protected gold clusters (MPCs) are synthesized and subsequently ...

Soft Lithographic Functionalization and Patterning Oxide-free Silicon and Germanium

The development of hybrid electronic devices relies in large part on the integration of (bio)organic materials and inorganic semiconductors through a stable interface that permits efficient electron transport and protects underlying substrates from oxidative degradation. Group IV semiconductors can be effectively protected with highly-ordered self-assembled monolayers (SAMs) composed of simple alkyl chains that act as impervious barriers to both organic and aqueous solutions. Simple alkyl SAMs, however, are inert and not amenable to traditional patterning techniques. The motivation for immobilizing organic molecular systems on semiconductors is to impart new functionality to the surface that can provide optical, electronic, and mechanical function, as well as chemical and biological activity. 
Microcontact printing (&mu;CP) is a soft-lithographic technique for patterning SAMs on myriad surfaces.1-9 Despite its simplicity and versatility, the approach has been largely limited to noble metal surfaces and has not been well developed for pattern transfer to technologically important substrates such as oxide-free silicon and germanium. Furthermore, because this technique relies on the ink diffusion to transfer pattern from the elastomer to substrate, the resolution of such traditional printing is essentially limited to near 1 &mu;m.10-16
In contrast to traditional printing, inkless &mu;CP patterning relies on a specific reaction between a surface-immobilized substrate and a stamp-bound catalyst. Because the technique does not rely on diffusive SAM formation, it significantly expands the diversity of patternable surfaces. In addition, the inkless technique obviates the feature size limitations imposed by molecular diffusion, facilitating replication of very small (&lt;200 nm) features.17-23 However, up till now, inkless &mu;CP has been mainly used for patterning relatively disordered molecular systems, which do not protect underlying surfaces from degradation.
Here, we report a simple, reliable high-throughput method for patterning passivated silicon and germanium with reactive organic monolayers and demonstrate selective functionalization of the patterned substrates with both small molecules and proteins. The technique utilizes a preformed NHS-reactive bilayered system on oxide-free silicon and germanium. The NHS moiety is hydrolyzed in a pattern-specific manner with a sulfonic acid-modified acrylate stamp to produce chemically distinct patterns of NHS-activated and free carboxylic acids. A significant limitation to the resolution of many &mu;CP techniques is the use of PDMS material which lacks the mechanical rigidity necessary for high fidelity transfer. To alleviate this limitation we utilized a polyurethane acrylate polymer, a relatively rigid material that can be easily functionalized with different organic moieties. Our patterning approach completely protects both silicon and germanium from chemical oxidation, provides precise control over the shape and size of the patterned features, and gives ready access to chemically discriminated patterns that can be further functionalized with both organic and biological molecules. The approach is general and applicable to other technologically-relevant surfaces.

Here we describe a simple method for patterning oxide-free silicon and germanium with reactive organic monolayers and demonstrate functionalization of the patterned substrates with small molecules and proteins. The approach completely protects surfaces from chemical oxidation, provides precise control over feature morphology, and provides ready access to chemically discriminated patterns.

The development of hybrid electronic devices relies in large part on the integration of (bio)organic materials and inorganic semiconductors through a ...

Combinatorial Synthesis of and High-throughput Protein Release from Polymer Film and Nanoparticle Libraries

Polyanhydrides are a class of biomaterials with excellent biocompatibility and drug delivery capabilities. While they have been studied extensively with conventional one-sample-at-a-time synthesis techniques, a more recent high-throughput approach has been developed enabling the synthesis and testing of large libraries of polyanhydrides1. This will facilitate more efficient optimization and design process of these biomaterials for drug and vaccine delivery applications. The method in this work describes the combinatorial synthesis of biodegradable polyanhydride film and nanoparticle libraries and the high-throughput detection of protein release from these libraries. In this robotically operated method (Figure 1), linear actuators and syringe pumps are controlled by LabVIEW, which enables a hands-free automated protocol, eliminating user error. Furthermore, this method enables the rapid fabrication of micro-scale polymer libraries, reducing the batch size while resulting in the creation of multivariant polymer systems. This combinatorial approach to polymer synthesis facilitates the synthesis of up to 15 different polymers in an equivalent amount of time it would take to synthesize one polymer conventionally. In addition, the combinatorial polymer library can be fabricated into blank or protein-loaded geometries including films or nanoparticles upon dissolution of the polymer library in a solvent and precipitation into a non-solvent (for nanoparticles) or by vacuum drying (for films). Upon loading a fluorochrome-conjugated protein into the polymer libraries, protein release kinetics can be assessed at high-throughput using a fluorescence-based detection method (Figures 2 and 3) as described previously1. This combinatorial platform has been validated with conventional methods2 and the polyanhydride film and nanoparticle libraries have been characterized with 1H NMR and FTIR. The libraries have been screened for protein release kinetics, stability and antigenicity; in vitro cellular toxicity, cytokine production, surface marker expression, adhesion, proliferation and differentiation; and in vivo biodistribution and mucoadhesion1-11. The combinatorial method developed herein enables high-throughput polymer synthesis and fabrication of protein-loaded nanoparticle and film libraries, which can, in turn, be screened in vitro and in vivo for optimization of biomaterial performance.

This method describes the combinatorial synthesis of biodegradable polyanhydride film and nanoparticle libraries and the high-throughput detection of protein release from these libraries.

Polyanhydrides are a class of biomaterials with excellent biocompatibility and drug delivery capabilities. While they have been studied extensively with ...

Evaluation of Polymeric Gene Delivery Nanoparticles by Nanoparticle Tracking Analysis and High-throughput Flow Cytometry

Non-viral gene delivery using polymeric nanoparticles has emerged as an attractive approach for gene therapy to treat genetic diseases1 and as a technology for regenerative medicine2. Unlike viruses, which have significant safety issues, polymeric nanoparticles can be designed to be non-toxic, non-immunogenic, non-mutagenic, easier to synthesize, chemically versatile, capable of carrying larger nucleic acid cargo and biodegradable and/or environmentally responsive. Cationic polymers self-assemble with negatively charged DNA via electrostatic interaction to form complexes on the order of 100 nm that are commonly termed polymeric nanoparticles. Examples of biomaterials used to form nanoscale polycationic gene delivery nanoparticles include polylysine, polyphosphoesters, poly(amidoamines)s and polyethylenimine (PEI), which is a non-degradable off-the-shelf cationic polymer commonly used for nucleic acid delivery1,3 . Poly(beta-amino ester)s (PBAEs) are a newer class of cationic polymers4 that are hydrolytically degradable5,6 and have been shown to be effective at gene delivery to hard-to-transfect cell types such as human retinal endothelial cells (HRECs)7, mouse mammary epithelial cells8, human brain cancer cells9 and macrovascular (human umbilical vein, HUVECs) endothelial cells10.
A new protocol to characterize polymeric nanoparticles utilizing nanoparticle tracking analysis (NTA) is described. In this approach, both the particle size distribution and the distribution of the number of plasmids per particle are obtained11. In addition, a high-throughput 96-well plate transfection assay for rapid screening of the transfection efficacy of polymeric nanoparticles is presented. In this protocol, poly(beta-amino ester)s (PBAEs) are used as model polymers and human retinal endothelial cells (HRECs) are used as model human cells. This protocol can be easily adapted to evaluate any polymeric nanoparticle and any cell type of interest in a multi-well plate format.

A protocol for nanoparticle tracking analysis (NTA) and high-throughput flow cytometry to evaluate polymeric gene delivery nanoparticles is described. NTA is utilized to characterize the nanoparticle particle size distribution and the plasmid per particle distribution. High-throughput flow cytometry enables quantitative transfection efficacy evaluation for a library of gene delivery biomaterials.

Non-viral gene delivery using polymeric nanoparticles has emerged as an attractive approach for gene therapy to treat genetic diseases1 and as a ...

Fabrication of a Functionalized Magnetic Bacterial Nanocellulose with Iron Oxide Nanoparticles

In this study, bacterial nanocellulose (BNC) produced by the bacteria Gluconacetobacter xylinus is synthesized and impregnated in situ with iron oxide nanoparticles (IONP) (Fe3O4) to yield a magnetic bacterial nanocellulose (MBNC). The synthesis of MBNC is a precise and specifically designed multi-step process. Briefly, bacterial nanocellulose (BNC) pellicles are formed from preserved G. xylinus strain according to our experimental requirements of size and morphology. A solution of iron(III) chloride hexahydrate (FeCl3&#183;6H2O) and iron(II) chloride tetrahydrate (FeCl2&#183;4H2O) with a 2:1 molar ratio is prepared and diluted in deoxygenated high purity water. A BNC pellicle is then introduced in the vessel with the reactants. This mixture is stirred and heated at 80 &#176;C in a silicon oil bath and ammonium hydroxide (14%) is then added by dropping to precipitate the ferrous ions into the BNC mesh. This last step allows forming in situ magnetite nanoparticles (Fe3O4) inside the bacterial nanocellulose mesh to confer magnetic properties to BNC pellicle. A toxicological assay was used to evaluate the biocompatibility of the BNC-IONP pellicle. Polyethylene glycol (PEG) was used to cover the IONPs in order to improve their biocompatibility. Scanning electron microscopy (SEM) images showed that the IONP were located preferentially in the fibril interlacing spaces of the BNC matrix, but some of them were also found along the BNC ribbons. Magnetic force microscope measurements performed on the MBNC detected the presence magnetic domains with high and weak intensity magnetic field, confirming the magnetic nature of the MBNC pellicle. Young&#39;s modulus values obtained in this work are also in a reasonable agreement with those reported for several blood vessels in previous studies.

Here, we present a protocol to make a bacterial nanocellulose (BNC) magnetic for applications in damaged blood vessel reconstruction. The BNC was synthesized by G. xylinus strain. On the other hand, magnetization of the BNC was realized through in situ precipitation of Fe2+ and Fe3+ ferrous ions inside the BNC mesh.

In this study, bacterial nanocellulose (BNC) produced by the bacteria Gluconacetobacter xylinus is synthesized and impregnated in situ with iron oxide ...

Identification of Metal Oxide Nanoparticles in Histological Samples by Enhanced Darkfield Microscopy and Hyperspectral Mapping

Nanomaterials are increasingly prevalent throughout industry, manufacturing, and biomedical research. The need for tools and techniques that aid in the identification, localization, and characterization of nanoscale materials in biological samples is on the rise. Currently available methods, such as electron microscopy, tend to be resource-intensive, making their use prohibitive for much of the research community. Enhanced darkfield microscopy complemented with a hyperspectral imaging system may provide a solution to this bottleneck by enabling rapid and less expensive characterization of nanoparticles in histological samples. This method allows for high-contrast nanoscale imaging as well as nanomaterial identification. For this technique, histological tissue samples are prepared as they would be for light-based microscopy. First, positive control samples are analyzed to generate the reference spectra that will enable the detection of a material of interest in the sample. Negative controls without the material of interest are also analyzed in order to improve specificity (reduce false positives). Samples can then be imaged and analyzed using methods and software for hyperspectral microscopy or matched against these reference spectra in order to provide maps of the location of materials of interest in a sample. The technique is particularly well-suited for materials with highly unique reflectance spectra, such as noble metals, but is also applicable to other materials, such as semi-metallic oxides. This technique provides information that is difficult to acquire from histological samples without the use of electron microscopy techniques, which may provide higher sensitivity and resolution, but are vastly more resource-intensive and time-consuming than light microscopy.

Enhanced darkfield microscopy and hyperspectral imaging with spectral mapping enable screening, localization, and identification of nanoscale materials in histological samples with improved speed and accuracy over traditional methods. The goal of this paper is to provide methods for darkfield imaging and hyperspectral mapping of metal oxide nanoparticles in histological samples.

Nanomaterials are increasingly prevalent throughout industry, manufacturing, and biomedical research. The need for tools and techniques that aid in the ...

Microwave-driven Synthesis of Iron Oxide Nanoparticles for Fast Detection of Atherosclerosis

A fast and reproducible microwave-driven protocol has been developed for the synthesis of neridronate-functionalized nanoparticles. Starting from the synthesis of hydrophobic nanoparticles, our method is based on an adaptation from thermal decomposition method to microwave driven synthesis. The new methodology produces a decrease in the reaction times in comparison with traditional procedures. Moreover, the use of the microwave technology increases the reproducibility of the reactions, something important from the point of view of clinical applications. The novelty of this iron oxide nanoparticle is the attachment of Neridronate. The use of this molecule leads a bisphosphonate moiety towards the outside of the nanoparticle that provides Ca2+ binding properties in vitro and selective accumulation in vivo in the atheroma plaque. The protocol allows the synthesis and plaque detection in about 3 hr since the initial synthesis from organic precursors. Their accumulation in the atherosclerotic area in less than 1 hr provides a contrast agent particularly suitable for clinical applications.

Microwave technology enables extremely fast synthesis of iron oxide nanoparticles for atherosclerosis plaque characterization. The use of an aminobisphosphonate in the external side of the nanoparticle provides a fast accumulation in the atherosclerotic area.

A fast and reproducible microwave-driven protocol has been developed for the synthesis of neridronate-functionalized nanoparticles. Starting from the ...

Synthesis of Gold Nanoparticle Integrated Photo-responsive Liposomes and Measurement of Their Microbubble Cavitation upon Pulse Laser Excitation

Photo-responsive nanoparticles (NPs) have received considerable attention because of their potential in providing spatial, temporal, and dosage control over the drug release. However, most of the relevant technologies are still in the development process and are unprocurable by clinics. Here, we describe a facile fabrication of these photo-responsive NPs with commercially available gold NPs and thermo-responsive liposomes. Calcein is used as a model drug to evaluate the encapsulation efficiency and the release kinetic profile upon heat/light stimulation. Finally, we show that this photo-triggered release is due to the membrane disruption caused by microbubble cavitation, which can be measured with hydrophone.

This protocol describes a simple preparation method for gold nanoparticle integrated photo-responsive liposomes with the commercially available materials. It also shows how to measure the microbubble cavitation process of the synthesized liposomes upon the treatment of pulsed laser.

Photo-responsive nanoparticles (NPs) have received considerable attention because of their potential in providing spatial, temporal, and dosage control ...

An Integrated System to Remotely Trigger Intracellular Signal Transduction by Upconversion Nanoparticle-mediated Kinase Photoactivation

Upconversion nanoparticle (UCNP)-mediated photoactivation is a new approach to remotely control bioeffectors with much less phototoxicity and with deeper tissue penetration. However, the existing instrumentation on the market is not readily compatible with upconversion application. Therefore, modifying the commercially available instrument is essential for this research. In this paper, we first illustrate the modifications of a conventional fluorimeter and fluorescence microscope to make them compatible for photon upconversion experiments. We then describe the synthesis of a near-infrared (NIR)-triggered caged protein kinase A catalytic subunit (PKA) immobilized on a UCNP complex. Parameters for microinjection and NIR photoactivation procedures are also reported. After the caged PKA-UCNP is microinjected into REF52 fibroblast cells, the NIR irradiation, which is significantly superior to conventional UV irradiation, efficiently triggers the PKA signal transduction pathway in living cells. In addition, positive and negative control experiments confirm that the PKA-induced pathway leading to the disintegration of stress fibers is specifically triggered by NIR irradiation. Thus, the use of protein-modified UCNP provides an innovative approach to remotely control light-modulated cellular experiments, in which direct exposure to UV light must be avoided.

In this protocol, caged protein kinase A (PKA), a cellular signal transduction bioeffector, was immobilized on a nanoparticle surface, microinjected into the cytosol, and activated by the upconverted UV light from near-infrared (NIR) irradiation, inducing downstream stress fiber disintegration in the cytosol.

Upconversion nanoparticle (UCNP)-mediated photoactivation is a new approach to remotely control bioeffectors with much less phototoxicity and with deeper ...

Retroductal Nanoparticle Injection to the Murine Submandibular Gland

Two common goals of salivary gland therapeutics are prevention and cure of tissue dysfunction following either autoimmune or radiation injury. By locally delivering bioactive compounds to the salivary glands, greater tissue concentrations can be safely achieved versus systemic administration. Furthermore, off target tissue effects from extra-glandular accumulation of material can be dramatically reduced. In this regard, retroductal injection is a widely used method for investigating both salivary gland biology and pathophysiology. Retroductal administration of growth factors, primary cells, adenoviral vectors, and small molecule drugs has been shown to support gland function in the setting of injury. We have previously shown the efficacy of a retroductally injected nanoparticle-siRNA strategy to maintain gland function following irradiation. Here, a highly effective and reproducible method to administer nanomaterials to the murine submandibular gland through Wharton's duct is detailed (Figure 1). We describe accessing the oral cavity and outline the steps necessary to cannulate Wharton's duct, with further observations serving as quality checks throughout the procedure.

Local drug delivery to the submandibular glands is of interest in understanding salivary gland biology and for the development of novel therapeutics. We present an updated and detailed retroductal injection protocol, designed to improve delivery accuracy and experimental reproducibility. The application presented herein is the delivery of polymeric nanoparticles.

Two common goals of salivary gland therapeutics are prevention and cure of tissue dysfunction following either autoimmune or radiation injury. By locally ...