Name: fabrication of spherical and worm-shaped micellar nanocrystals by combining electrospray, self-assembly, and solvent-based structure control
Uploaded: 2018-02-11T13:00:00
Description: Watch this Scientific Journal Video about Fabrication of Spherical and Worm-shaped Micellar Nanocrystals by Combining Electrospray, Self-assembly, and Solvent-based Structure Control at JoVE.com

The authors gratefully acknowledge the financial support of a &#34;Thousand Young Global Talents&#34; award from the Chinese Central Government, a &#34;Shuang Chuang&#34; award from the Jiangsu Provincial Government, start-up fund from College of Engineering and Applied Sciences, Nanjing University, China, award from the &#34;Tian-Di&#34; Foundation, grant from the Priority Academic Program Development Fund of Jiangsu Higher Education Institutions (PAPD), grant from the Jiangsu Province Natural Science Fund.

Caution: Due to the use of organic solvents, all operations should be done in a chemical fume hood. Due to the use of high electric voltage, avoid body contact with the apparatus when the power supply is on. Use all appropriate safety practices such as using personal protective equipment (safety glasses, gloves, lab coat, full-length pants, and closed-toe shoes). Consult all relevant material safety data sheets (MSDS).
1. Setup of Materials
<ol>
	<li>To prepare QD solution, dissolve 10 mg hy...

<ol>
	<li>Nie, S., Xing, Y., Kim, G. J., Simons, 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=Nanotechnology+Applications+in+Cancer.">Nanotechnology Applications in Cancer.</a> Annu. Rev. Biomed. Eng. 9, 257-288 (2007).</li><li>Smith, A. M., Ruan, G., Rhyner, M. N., Nie, S. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Engineering+Luminescent+Quantum+Dots+for+In+Vivo+Molecular+and+Cellular+Imaging.">Engineering Luminescent Quantum Dots for In Vivo Molecular and Cellular Imaging.</a> Annals Biomed. Eng. 34 (1), 3-14 (2006).</li><li>Heath, J. R., Davis, M. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nanotechnology+and+Cancer.">Nanotechnology and Cancer.</a> Annu. Rev. Medicine. 59, 251-265 (2008).</li><li>Pu, K., Chattopadhyay, N., Rao, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recent+advances+of+semiconducting+polymer+nanoparticles+in+in+vivo+molecular+imaging.">Recent advances of semiconducting polymer nanoparticles in in vivo molecular imaging.</a> J. Control. Release. 240, 312-322 (2016).</li><li>Swierczewska, M., Han, H. S., Kim, K., Park, J. H., Lee, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Polysaccharide-based+nanoparticles+for+theranostic+nanomedicine.">Polysaccharide-based nanoparticles for theranostic nanomedicine.</a> Adv. Drug Deliv. Rev. 99, 70-84 (2016).</li><li>Gao, X. H., Yang, L. L., Petros, J. A., Marshal, F. F., Simons, J. W., Nie, S. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vivo+molecular+and+cellular+imaging+with+quantum+dots.">In vivo molecular and cellular imaging with quantum dots.</a> Curr. Opin. Biotechnol. 16 (1), 63-72 (2005).</li><li>Dubertret, B., Skourides, P., Norris, D. J., Noireaux, V., Brivanlou, A. H., Libchaber, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vivo+imaging+of+quantum+dots+encapsulated+in+phospholipid+micelles.">In vivo imaging of quantum dots encapsulated in phospholipid micelles.</a> Science. 298 (5599), 1759-1762 (2002).</li><li>Ruan, 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=Simultaneous+magnetic+manipulation+and+fluorescent+tracking+of+multiple+individual+hybrid+nanostructures.">Simultaneous magnetic manipulation and fluorescent tracking of multiple individual hybrid nanostructures.</a> Nano Lett. 10 (6), 2220-2224 (2010).</li><li>Ruan, G., Winter, J. O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Alternating-color+quantum+dot+nanocomposites+for+particle+tracking.">Alternating-color quantum dot nanocomposites for particle tracking.</a> Nano Lett. 11 (3), 941-945 (2011).</li><li>Park, J. H., von Maltzahn, G., Ruoslahti, E., Bhatia, S. N., Sailor, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Micellar+hybrid+nanoparticles+for+simultaneous+magnetofluorescent+imaging+and+drug+delivery.">Micellar hybrid nanoparticles for simultaneous magnetofluorescent imaging and drug delivery.</a> Angewandte Chemie-International Edition. 47 (38), 7284-7288 (2008).</li><li>Torchilin, V. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=PEG-based+micelles+as+carriers+of+contrast+agents+for+different+imaging+modalities.">PEG-based micelles as carriers of contrast agents for different imaging modalities.</a> Adv. Drug Deliv. Rev. 54 (2), 235-252 (2002).</li><li>Sun, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Examining+the+roles+of+emulsion+droplet+size+and+surfactant+in+the+interfacial+instability-based+fabrication+process+of+micellar+nanocrystals.">Examining the roles of emulsion droplet size and surfactant in the interfacial instability-based fabrication process of micellar nanocrystals.</a> Nanoscale Research Letters. 12, 434 (2017).</li><li>Ding, X. Y., Han, N., Wang, J., Sun, Y. X., Ruan, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+organic+solvents+on+the+structures+of+micellar+nanocrystals.">Effects of organic solvents on the structures of micellar nanocrystals.</a> RSC Advances. 7 (26), 16131-16138 (2017).</li><li>Sailor, M., Park, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hybrid+nanoparticles+for+detection+and+treatment+of+cancer.">Hybrid nanoparticles for detection and treatment of cancer.</a> Adv. Materials. 24 (28), 3779-3802 (2012).</li><li>Jing, L. H., Ding, K., Kershaw, S. V., Kempson, T. M., Rogach, A. L., Gao, M. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Magnetically+engineered+semiconductor+quantum+dots+as+multimodal+imaging+probes.">Magnetically engineered semiconductor quantum dots as multimodal imaging probes.</a> Adv. Materials. 26 (37), 6367-6386 (2014).</li><li>Bao, G., Mitragotri, S., Tong, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Multifunctional+nanoparticles+for+drug+delivery+and+molecular+imaging.">Multifunctional nanoparticles for drug delivery and molecular imaging.</a> Annu. Rev. Biomed. Eng. 15, 253-282 (2013).</li><li>Mura, S., Couvreur, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nanotheranostics+for+personalized+medicine.">Nanotheranostics for personalized medicine.</a> Adv. Drug Delivery Rev. 64 (13), 1394-1416 (2012).</li><li>Louie, A. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Multimodality+imaging+probes:+design+and+challenges.">Multimodality imaging probes: design and challenges.</a> Chem. Rev. 110 (5), 3146-3195 (2010).</li></ol>

The fabrication method of micellar nanocrystals described in the present work combines top-down electrospray, bottom-up self-assembly, and solvent-based structure control. An effective and convenient quality control method is to use the Taylor cone formed at the coaxial nozzle tip. This is because a properly formed Taylor cone indicates balance (or near balance) between electric force and surface tension, which in turn indicates successful formation of micro-reactors (uniform ultrafine droplets) for the self-assembly rea...

Nanocrystals such as semiconductor quantum dots (QDs) and superparamagnetic iron oxide nanoparticles (SPIONs) have demonstrated great potential for biological detection, imaging, manipulation, and therapy1,2,3,4,5,6. Encapsulating one or more nanocrystals into a micelle has been a widely used method to interface nanocrystals with biological environments3,6. The thus-formed micellar nanocrystals (micelles with nanocrystals encapsulated) have become an emerging class of nanobiomaterials7,8,9,10. Commonly used methods to fabricate micelles that encapsulate various materials (e.g., nanocrystals, small molecule drugs, and dyes) include film hydration, dialysis, and several others7,11.
The present work describes a method of fabricating micellar nanocrystals based on combining top-down electrospray, bottom-up self-assembly, and solvent-mediated structural control. Compared with other fabrication methods of micellar nanocrystals, our method offers several beneficial features: (1) It is a largely continuous production process. This feature is mainly due to the fact that electrospray is used in our method to form emulsion droplets. In contrast, some other methods use vortexing or sonication to form emulsion droplets, thereby making these methods batch processes in nature12. (2) It results in products with high water-dispersibility, excellent colloidal stability, and intact physical functions of the encapsulated nanocrystals. This process can often give products with superior quality compared with other micelle encapsulation methods, to a large extent because electrospray can form ultrafine and uniform emulsion droplets. (3) The structures of the products, including micelle shape and number of encapsulated nanocrystals, can be controlled by the solvent, which is much more inexpensive compared with other ways of control such as changing the amphiphilic polymers used, and can produce not only the commonly available spherical micelle shape but worm-like micelle shape via micelle fusion13. The thus-formed worm-shaped micellar nanocrystals are found to offer greatly reduced non-specific cellular uptake than the spherical counterparts13. On the other hand, it is worth pointing out that this method requires the setup of an electrospray device, which is somewhat more technically demanding (although far from prohibitive) than the need of instrumentation in the other methods.
The fabrication method involves first generating ultrafine liquid (often oil-in-water emulsion) droplets with uniform sizes by electrospray, followed by evaporation of organic solvent resulting in self-assembly to form micellar nanocrystals (Figure 1).The electrospray setup has a coaxial configuration using concentric needles: the oil phase, which contains amphiphilic block copolymers and hydrophobic nanocrystals dissolved in organic solvent, is delivered to the inner needle (27 G stainless-steel capillary) with a syringe pump; the water phase, which contains a surfactant dissolved in water, is delivered to the outer needle (20 G stainless-steel three-way connector) with a second syringe pump. A high voltage is applied to the coaxial nozzle. Ultrafine droplets with uniform sizes are generated due to electrodynamic force overcoming surface tension and inertial stress in the liquid. Each droplet essentially functions as a &#39;micro-reactor&#39;, in which, upon removal of the organic solvent by evaporation, the self-assembly &#39;reaction&#39; occurs spontaneously due to hydrophobic interactions. Using different organic solvents leads to different structures of micellar nanocrystals: a water-immiscible organic solvent chloroform leads to spherical micelle shape, while a water-miscible organic solvent THF with a long reaction time leads to worm-like micelle shape along with enhanced nanocrystal encapsulation.

<table>
	<tbody>
		<tr>
			<td>Hydrophobic quantum dots</td>
			<td>Ocean Nanotech</td>
			<td>QSP</td>
			<td>Solid hydrophobic CdSe/ZnS quantum dots. Peak fluorescence emission wavelength is 605 nm.</td>
		</tr>
		<tr>
			<td>Poly(styrene)-b-poly(ethylene glycol) (PS-PEG)</td>
			<td>Sigma-Aldrich</td>
			<td>666476-500MG</td>
			<td>Molecular weight of PS segment is 9.5 kDa and that of PEG segment is 18.0 kDa.</td>
		</tr>
		<tr>
			<td>Poly(vinyl alcohol) (PVA)</td>
			<td>Sigma-Aldrich</td>
			<td>363170-500G</td>
			<td>Molecular weight 13&#8211;23 kDa, 87&#8211;89% hydrolyzed.</td>
		</tr>
		<tr>
			<td>Tetrahydrofuran (THF)</td>
			<td>Sinopharma Chemical Reagent</td>
			<td>80124418</td>
			<td></td>
		</tr>
		<tr>
			<td>Chloroform</td>
			<td>Sinopharma Chemical Reagent</td>
			<td>40007960</td>
			<td></td>
		</tr>
		<tr>
			<td>Syringe pumps</td>
			<td>Bao Ding Shen Chen</td>
			<td>SPLab01</td>
			<td></td>
		</tr>
		<tr>
			<td>Tubing</td>
			<td>Shanghei Lai Xing</td>
			<td></td>
			<td>2 mm outer diameter and 1.8 mm inner diameter PTFE tubing.</td>
		</tr>
		<tr>
			<td>Syringes</td>
			<td>Yi Ming</td>
			<td>5.CC</td>
			<td>5 mL disposable syringe made of PTFE.</td>
		</tr>
		<tr>
			<td>High voltage power supply</td>
			<td>Dong Wen</td>
			<td>DW Series</td>
			<td>Direct current power supply (0&#8211;50 kV range).</td>
		</tr>
		<tr>
			<td>Electrospray coaxial nozzle</td>
			<td>Hunan Chang Sha Na Yi</td>
			<td></td>
			<td>Stainless steel assembly. Inner capillary needle was a 27 gauge (outer diameter 500 &#956;m; inner diameter 300 &#956;m). Outer capillary was a 20 gauge (outer diameter 1,000 &#956;m; inner diameter 500 &#956;m).</td>
		</tr>
		<tr>
			<td>Vortexer</td>
			<td>Xi&#39;an HEB Biotechnology Co., Ltd. China</td>
			<td>MX-S</td>
			<td>MX-S with wide speed range of 0&#8211;2,500 rpm, stepless speed regulation, touch and continuous operations.</td>
		</tr>
		<tr>
			<td>Steel ring</td>
			<td>Yiwu Wan Tu</td>
			<td></td>
			<td>Rings with a range of diameters (0.8&#8211;1.8 cm) can be constructued. For example, a 1.3 cm diameter ring was constructed by curling an approximately 25 cm (length) of 0.5-mm diamter (24 gauge, AWG) steel wire.</td>
		</tr>
		<tr>
			<td>Glass collecting dish</td>
			<td>Grainger</td>
			<td>1u5084</td>
			<td>25-mm height and 120-mm diameter glass dish.</td>
		</tr>
		<tr>
			<td>15 mL centrifuge tube</td>
			<td>Jiangsu Xinkang Medical Instrument Co., Ltd.</td>
			<td>X-407</td>
			<td>Centrifuge tube is made of transparent polypropylene (PP).</td>
		</tr>
	</tbody>
</table>

fabrication of spherical and worm-shaped micellar nanocrystals by combining electrospray, self-assembly, and solvent-based structure control

Micellar nanocrystals (micelles with encapsulated nanocrystals) have become an emerging major class of nanobiomaterials. We describe a method of fabricating micellar nanocrystals based on combining top-down electrospray, bottom-up self-assembly, and solvent-based structure control. This method involves first using electrospray to generate uniform ultrafine liquid droplets, each of which functions as a micro-reactor in which self-assembly reaction occurs forming micellar nanocrystals, with the structures (micelle shape and nanocrystal encapsulation) controlled by the organic solvent used. This method is largely continuous and produces high quality micellar nanocrystal products with an inexpensive structure control approach. By using a water-miscible organic solvent tetrahydrofuran (THF), worm-shaped micellar nanocrystals can be produced due to solvent-induced/facilitated micelle fusion. Compared with the common spherical micellar nanocrystals, worm-shaped micellar nanocrystals can offer minimized non-specific cellular uptake, thus enhancing biological targeting. By co-encapsulating multiple nanocrystals into each micelle, multifunctional or synergistic effects can be achieved. Current limitations of this fabrication method, which will be part of the future work, primarily include imperfect encapsulation in the micellar nanocrystal product and the incompletely continuous nature of the process.

Figure 1 shows a schematic summarizing the control of structures (shape and encapsulation) of micellar nanocrystals by the organic solvent used in the production process. Briefly, dichloromethane leads to spherical micelles with no encapsulation of nanocrystals; chloroform leads to spherical micelles with a low encapsulation number of nanocrystals; THF leads to spherical micelles with a high encapsulation number of nanocrystals at a short reaction time and wo...

Watch this Scientific Journal Video about Fabrication of Spherical and Worm-shaped Micellar Nanocrystals by Combining Electrospray, Self-assembly, and Solvent-based Structure Control at JoVE.com

Fabrication of Spherical and Worm-shaped Micellar Nanocrystals by Combining Electrospray, Self-assembly, and Solvent-based Structure Control

The present work describes a method to fabricate micellar nanocrystals, an emerging major class of nanobiomaterials. This method combines top-down electrospray, bottom-up self-assembly, and solvent-based structure control. The fabrication method is largely continuous, can produce high quality products, and possesses an inexpensive means of structure control.

Micellar nanocrystals (micelles with encapsulated nanocrystals) have become an emerging major class of nanobiomaterials. We describe a method of ...

The overall goal of this procedure is to fabricate micellar nanocrystals by combining top-down electrospray, bottom-up self-assembly, and an inexpensive solvent-based method of structure control. This method offers a good way to produce an emerging class of nanobiomaterials known as micellar nanocrystals, which can be useful for biomedical detection, imaging, and therapy. The main advantages of this technique include, firstly, it's a continuous process.Second, it produces high quality products. And thirdly, it has an inexpensive way of controlling structure. Potentially, this technique could be adapted to produce other types of nanomaterials as well.To begin the procedure, dissolve 10 milligrams of hydrophobic quantum dots in 20 milliliters of either chloroform or tetrahydrofuran, depending on the desired micelle shape. Vortex the solution for 20 seconds. Next, dissolve 100 milligrams of polystyrene block polyethylene glycol in 10 milliliters of either chloroform or THF, depending on the desired shape.If the solution is in chloroform, vortex it for 20 seconds. If the solution is in THF instead, sonicate it in a bath sonicator for two minutes. Combine one milliliter of the quantum dot solution with one milliliter of the PS peg solution.Vortex the mixture for one minute, and then draw the solution into a five milliliter PTFE syringe labeled Syringe A.Next, combine 400 milligrams of polyvinyl alcohol with 10 milliliters of deionized water. Stir the mixture at 60 to 80 degrees Celsius for four to five hours. Then, allow the PVA solution to cool to room temperature.Draw the cooled PVA solution into a five milliliter PTFE syringe labeled Syringe B.To begin setting up the coaxial electrospray system, insert the 27-gauge stainless steel inner capillary into the 20-gauge stainless steel outer capillary assembly. Gently screw the inner capillary into position until it just meets resistance, being careful not to overtighten. Load Syringe A into a syringe pump.Connect the syringe to the inner capillary of the coaxial nozzle with 37 centimeters of PTFE tubing. Load Syringe B into another syringe pump, and connect the syringe to the outer capillary with 17 centimeters of PTFE tubing. Position the coaxial nozzle tip about 0.8 centimeters above a steel wire ring, with a diameter of 1.5 centimeters fixed to a metal rod.Place a 25 millimeter by 125 millimeter circular glass collection dish on a stand approximately 10 centimeters below the nozzle tip. Ensure that the direct current high voltage power supply is turned off. Then, ground the steel ring by connecting it to the negative terminal of the power supply.Finally, connect the positive terminal of the power supply to the inner needle of the coaxial nozzle. Set syringe pump A to 0.6 milliliters per hour, and syringe pump B to 1.5 milliliters per hour. Start both syringe pumps and wait for the flow rates to stabilize, as indicated by drops forming at the nozzle at a steady rate.Verify that there are no air bubbles in the tubing and that there are no leaks. Then turn on the system power supply. Adjust the applied voltage, staying between five and nine kilovolts, until a properly formed tailor cone is observed at the coaxial nozzle tip.Then, place 10 milliliters of deionized water into a new collection dish. Replace the collection dish in the assembly with a new dish. Allow the electrospray process to run for 40 minutes when producing spherical micelles, or 90 minutes when producing wormlike micelles.Then remove the collection dish. Stop the syringe pumps and turn off the power supply. Let the product dish sit uncovered in a fume hood overnight to allow the organic solvent to evaporate.Then, transfer the product to a 15 milliliter centrifuge tube for characterization or use. Store the product at four degrees Celsius for up to one month. Transmission electron microscopy of micelles produced in chloroform revealed spherical particles with a low encapsulation number of nanocrystals.The particle size was approximately 35 nanometers. Proper tailor cone formation was essential for micelle self-assembly. An improperly formed tailor cone resulted in overall unsuccessful production.When THF was used as the organic solvent, wormlike micelles formed from the fusion of self-assembled spherical micelles. After 90 minutes, nearly all observed micellar nanocrystals were in wormlike shapes. The use of THF also resulted in greater nanocrystal encapsulation than was observed in chloroform.After watching this video, you should have a good understanding of how to make micellar nanocrystals of different shapes using our fabrication method, which is scalable, inexpensive, and gives good quality of products.

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Chemistry

Origami Inspired Self-assembly of Patterned and Reconfigurable Particles

There are numerous techniques such as photolithography, electron-beam lithography and soft-lithography that can be used to precisely pattern two dimensional (2D) structures. These technologies are mature, offer high precision and many of them can be implemented in a high-throughput manner. We leverage the advantages of planar lithography and combine them with self-folding methods1-20 wherein physical forces derived from surface tension or residual stress, are used to curve or fold planar structures into three dimensional (3D) structures. In doing so, we make it possible to mass produce precisely patterned static and reconfigurable particles that are challenging to synthesize.
In this paper, we detail visualized experimental protocols to create patterned particles, notably, (a) permanently bonded, hollow, polyhedra that self-assemble and self-seal due to the minimization of surface energy of liquefied hinges21-23 and (b) grippers that self-fold due to residual stress powered hinges24,25. The specific protocol described can be used to create particles with overall sizes ranging from the micrometer to the centimeter length scales. Further, arbitrary patterns can be defined on the surfaces of the particles of importance in colloidal science, electronics, optics and medicine. More generally, the concept of self-assembling mechanically rigid particles with self-sealing hinges is applicable, with some process modifications, to the creation of particles at even smaller, 100 nm length scales22, 26 and with a range of materials including metals21, semiconductors9 and polymers27. With respect to residual stress powered actuation of reconfigurable grasping devices, our specific protocol utilizes chromium hinges of relevance to devices with sizes ranging from 100 &mu;m to 2.5 mm. However, more generally, the concept of such tether-free residual stress powered actuation can be used with alternate high-stress materials such as heteroepitaxially deposited semiconductor films5,7 to possibly create even smaller nanoscale grasping devices.

We describe experimental details of the synthesis of patterned and reconfigurable particles from two dimensional (2D) precursors. This methodology can be used to create particles in a variety of shapes including polyhedra and grasping devices at length scales ranging from the micro to centimeter scale.

There are numerous techniques such as photolithography, electron-beam lithography and soft-lithography that can be used to precisely pattern two ...

Seeded Synthesis of CdSe/CdS Rod and Tetrapod Nanocrystals

We demonstrate a method for the synthesis of multicomponent nanostructures consisting of CdS and CdSe with rod and tetrapod morphologies. A seeded synthesis strategy is used in which spherical seeds of CdSe are prepared first using a hot-injection technique. By controlling the crystal structure of the seed to be either wurtzite or zinc-blende, the subsequent hot-injection growth of CdS off of the seed results in either a rod-shaped or tetrapod-shaped nanocrystal, respectively. The phase and morphology of the synthesized nanocrystals are confirmed using X-ray diffraction and transmission electron microscopy, demonstrating that the nanocrystals are phase-pure and have a consistent morphology. The extinction coefficient and quantum yield of the synthesized nanocrystals are calculated using UV-Vis absorption spectroscopy and photoluminescence spectroscopy. The rods and tetrapods exhibit extinction coefficients and quantum yields that are higher than that of the bare seeds. This synthesis demonstrates the precise arrangement of materials that can be achieved at the nanoscale by using a seeded synthetic approach.

A protocol for the seeded synthesis of rod-shaped and tetrapod-shaped multicomponent nanostructures consisting of CdS and CdSe is presented.

We demonstrate a method for the synthesis of multicomponent nanostructures consisting of CdS and CdSe with rod and tetrapod morphologies. A seeded ...

Formation of Ordered Biomolecular Structures by the Self-assembly of Short Peptides

In nature, complex functional structures are formed by the self-assembly of biomolecules under mild conditions. Understanding the forces that control self-assembly and mimicking this process in vitro will bring about major advances in the areas of materials science and nanotechnology. Among the available biological building blocks, peptides have several advantages as they present substantial diversity, their synthesis in large scale is straightforward, and they can easily be modified with biological and chemical entities1,2. Several classes of designed peptides such as cyclic peptides, amphiphile peptides and peptide-conjugates self-assemble into ordered structures in solution. Homoaromatic dipeptides, are a class of short self-assembled peptides that contain all the molecular information needed to form ordered structures such as nanotubes, spheres and fibrils3-8. A large variety of these peptides is commercially available.
This paper presents a procedure that leads to the formation of ordered structures by the self-assembly of homoaromatic peptides. The protocol requires only commercial reagents and basic laboratory equipment. In addition, the paper describes some of the methods available for the characterization of peptide-based assemblies. These methods include electron and atomic force microscopy and Fourier-Transform Infrared Spectroscopy (FT-IR). Moreover, the manuscript demonstrates the blending of peptides (coassembly) and the formation of a &#34;beads on a string&#34;-like structure by this process.9 The protocols presented here can be adapted to other classes of peptides or biological building blocks and can potentially lead to the discovery of new peptide-based structures and to better control of their assembly.

This paper describes the formation of highly ordered peptide-based structures by the spontaneous process of self-assembly. The method utilizes commercially available peptides and common lab equipment. This technique can be applied to a large variety of peptides and may lead to the discovery of new peptide-based assemblies.

In nature, complex functional structures are formed by the self-assembly of biomolecules under mild conditions. Understanding the forces that control ...

Self-assembly of Complex Two-dimensional Shapes from Single-stranded DNA Tiles

Current methods in DNA nano-architecture have successfully engineered a variety of 2D and 3D structures using principles of self-assembly. In this article, we describe detailed protocols on how to fabricate sophisticated 2D shapes through the self-assembly of uniquely addressable single-stranded DNA tiles which act as molecular pixels on a molecular canvas. Each single-stranded tile (SST) is a 42-nucleotide DNA strand composed of four concatenated modular domains which bind to four neighbors during self-assembly. The molecular canvas is a rectangle structure self-assembled from SSTs. A prescribed complex 2D shape is formed by selecting the constituent molecular pixels (SSTs) from a 310-pixel molecular canvas and then subjecting the corresponding strands to one-pot annealing. Due to the modular nature of the SST approach we demonstrate the scalability, versatility and robustness of this method. Compared with alternative methods, the SST method enables a wider selection of information polymers and sequences through the use of de novo designed and synthesized short DNA strands.

DNA tiling is an effective approach to make programmable nanostructures. We describe the protocols to construct complex two-dimensional shapes by the self-assembly of single-stranded DNA tiles.

Current methods in DNA nano-architecture have successfully engineered a variety of 2D and 3D structures using principles of self-assembly. In this ...

A Study of the Complexation of Mercury(II) with Dicysteinyl Tetrapeptides by Electrospray Ionization Mass Spectrometry

In this study we evaluated a method for the characterization of complexes, formed in different relative ratios of mercury(II) to dicysteinyl tetrapeptide, by electrospray ionization orbitrap mass spectrometry. This strategy is based on previous successful characterization of mercury-dicysteinyl complexes involving tripeptides by utilizing mass spectrometry among other techniques. Mercury(II) chloride and a dicysteinyl tetrapeptide were incubated in a degassed buffered medium at varying stoichiometric ratios. The complexes formed were subsequently analyzed on an electrospray mass spectrometer consisting of a hybrid linear ion- and orbi- trap mass analyzer. The electrospray ionization mass spectrometry (ESI-MS) spectra were acquired in the positive mode and the observed peaks were then analyzed for distinct mercury isotopic distribution patterns and associated monoisotopic peak. This work demonstrates that an accurate stoichiometry of mercury and peptide in the complexes formed under specified electrospray ionization conditions can be determined by using high resolution ESI MS based on distinct mercury isotopic distribution patterns.

A Study of the Complexation of MercuryII with Dicysteinyl Tetrapeptides by Electrospray Ionization Mass Spectrometry

The characterization of complexes formed in different relative ratios of mercury(II) to dicysteinyl tetrapeptides by electrospray ionization orbitrap mass spectrometry is presented.

In this study we evaluated a method for the characterization of complexes, formed in different relative ratios of mercury(II) to dicysteinyl tetrapeptide, ...

Green and Low-cost Production of Thermally Stable and Carboxylated Cellulose Nanocrystals and Nanofibrils Using Highly Recyclable Dicarboxylic Acids

Here we demonstrate potentially low cost and green productions of high thermally stable and carboxylated cellulose nanocrystals (CNCs) and nanofibrils (CNF) from bleached eucalyptus pulp (BEP) and unbleached mixed hardwood kraft pulp (UMHP) fibers using highly recyclable dicarboxylic solid acids. Typical operating conditions were acid concentrations of 50 - 70 wt% at 100 &#176;C for 60 min and 120 &#176;C (no boiling at atmospheric pressure) for 120 min, for BEP and UMHP, respectively. The resultant CNCs have a higher thermal degradation temperature than their corresponding feed fibers and carboxylic acid group content from 0.2 - 0.4 mmol/g. The low strength (high pKa of 1.0 - 3.0) of organic acids also resulted in CNCs with both longer lengths of approximately 239 - 336 nm and higher crystallinity than CNCs produced using mineral acids. Cellulose loss to sugar was minimal. Fibrous cellulosic solid residue (FCSR) from the dicarboxylic acid hydrolysis was used to produce carboxylated CNFs through subsequent mechanical fibrillation with low energy input.

Here we demonstrate a novel method for green and sustainable productions of highly thermally stable and carboxylated cellulose nanocrystals (CNC) and nanofibrils (CNF) using highly recyclable solid dicarboxylic acids.

Here we demonstrate potentially low cost and green productions of high thermally stable and carboxylated cellulose nanocrystals (CNCs) and nanofibrils ...

Influence of Hybrid Perovskite Fabrication Methods on Film Formation, Electronic Structure, and Solar Cell Performance

Hybrid organic/inorganic halide perovskites have lately been a topic of great interest in the field of solar cell applications, with the potential to achieve device efficiencies exceeding other thin film device technologies. Yet, large variations in device efficiency and basic physical properties are reported. This is due to unintentional variations during film processing, which have not been sufficiently investigated so far. We therefore conducted an extensive study of the morphology and electronic structure of a large number of CH3NH3PbI3 perovskite where we show how the preparation method as well as the mixing ratio of educts methylammonium iodide and lead(II) iodide impact properties like film formation, crystal structure, density of states, energy levels, and ultimately the solar cell performance.

We present an extensive study on the effects of different fabrication methods for organic/inorganic perovskite thin films by comparing crystal structures, density of states, energy levels, and ultimately the solar cell performance.

Hybrid organic/inorganic halide perovskites have lately been a topic of great interest in the field of solar cell applications, with the potential to ...

Grafting Multiwalled Carbon Nanotubes with Polystyrene to Enable Self-Assembly and Anisotropic Patchiness

We demonstrate a straightforward protocol to graft pristine multiwalled carbon nanotubes (MWCNTs) with polystyrene (PS) chains at the sidewalls through a free-radical polymerization strategy to enable the modulation of the nanotube surface properties and produce supramolecular self-assembly of the nanostructures. First, a selective hydroxylation of the pristine nanotubes through a biphasic catalytically mediated oxidation reaction creates superficially distributed reactive sites at the sidewalls. The latter reactive sites are subsequently modified with methacrylic moieties using a silylated methacrylic precursor to create polymerizable sites. Those polymerizable groups can address further polymerization of styrene to produce a hybrid nanomaterial containing PS chains grafted to the nanotube sidewalls. The polymer-graft content, amount of silylated methacrylic moieties introduced and hydroxylation modification of the nanotubes are identified and quantified by Thermogravimetric Analysis (TGA). The presence of reactive functional groups hydroxyl and silylated methacrylate are confirmed by Fourier Transform Infrared Spectroscopy (FT-IR). Polystyrene-grafted carbon nanotube solutions in tetrahydrofuran (THF) provide wall-to-wall collinearly self-assembled nanotubes when cast samples are analyzed by transmission electron microscopy (TEM). Those self-assemblies are not obtained when suitable blanks are similarly cast from analogous solutions containing non-grafted counterparts. Therefore, this method enables the modification of the nanotube anisotropic patchiness at the sidewalls which results into spontaneous auto-organization at the nanoscale.

A procedure for the synthesis of polystyrene-grafted multiwalled carbon nanotubes using successive chemical modification steps to selectively introduce the polymer chains to the sidewalls and their self-assembly via anisotropic patchiness is presented.

We demonstrate a straightforward protocol to graft pristine multiwalled carbon nanotubes (MWCNTs) with polystyrene (PS) chains at the sidewalls through a ...

Liquid-cell Transmission Electron Microscopy for Tracking Self-assembly of Nanoparticles

Drying a nanoparticle dispersion is a versatile way to create self-assembled structures of nanoparticles, but the mechanism of this process is not fully understood. We have traced the trajectories of individual nanoparticles using liquid-cell transmission electron microscopy (TEM) to investigate the mechanism of the assembly process. Herein, we present the protocols used for liquid-cell TEM studies of the self-assembly mechanism. First, we introduce the detailed synthetic protocols used to produce uniformly sized platinum and lead selenide nanoparticles. Next, we present the microfabrication processes used to produce liquid cells with silicon nitride or silicon windows and then describe the loading and imaging procedures of the liquid-cell TEM technique. Several notes are included to provide helpful tips for the entire process, including how to manage the fragile cell windows. The individual motions of nanoparticles tracked by liquid-cell TEM revealed that changes in the solvent boundaries caused by evaporation affected the self-assembly process of nanoparticles. The solvent boundaries drove nanoparticles to primarily form amorphous aggregates, followed by flattening of the aggregates to produce a 2-dimensional (2D) self-assembled structure. These behaviors are also observed for different nanoparticle types and different liquid-cell compositions.

Here we introduce experimental protocols for the real-time observation of a self-assembly process using liquid-cell transmission electron microscopy.

Drying a nanoparticle dispersion is a versatile way to create self-assembled structures of nanoparticles, but the mechanism of this process is not fully ...

Synthesis of Core-shell Lanthanide-doped Upconversion Nanocrystals for Cellular Applications

Lanthanide-doped upconversion nanocrystals (UCNs) have attracted much attention in recent years based on their promising and controllable optical properties, which allow for the absorption of near-infrared (NIR) light and can subsequently convert it into multiplexed emissions that span over a broad range of regions from the UV to the visible to the NIR. This article presents detailed experimental procedures for high-temperature co-precipitation synthesis of core-shell UCNs that incorporate different lanthanide ions into nanocrystals for efficiently converting deep-tissue penetrable NIR excitation (808 nm) into a strong blue emission at 480 nm. By controlling the surface modification with biocompatible polymer (polyacrylic acid, PAA), the as-prepared UCNs acquires great solubility in buffer solutions. The hydrophilic nanocrystals are further functionalized with specific ligands (dibenzyl cyclooctyne, DBCO) for localization on the cell membrane. Upon NIR light (808 nm) irradiation, the upconverted blue emission can effectively activate the light-gated channel protein on the cell membrane and specifically regulate the cation (e.g., Ca2+) influx in the cytoplasm. This protocol provides a feasible methodology for the synthesis of core-shell lanthanide-doped UCNs and subsequent biocompatible surface modification for further cellular applications.

A protocol is presented for the synthesis of core-shell lanthanide-doped upconversion nanocrystals (UCNs) and their cellular applications for channel protein regulation upon near-infrared (NIR) light illumination.