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>
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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 ...

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