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

Podsumowanie

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.

Streszczenie

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.

Wprowadzenie

Nanocrystals such as semiconductor quantum dots (QDs) and superparamagnetic iron oxide nanoparticles (SPIONs) have demonstrated great potential for biological detection, imaging, manipulation, and therapy^1,2,3,4,5,6. Encapsulating one or more nanocrystals into a micelle has been a widely used method to interface nanocrystals with biological environments^3,6. The thus-formed micellar nanocrystals (micelles with nanoc....

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Protokół

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

1. To prepare QD solution, dissolve 10 mg hydrophobic QDs (fluorescent emission peak wavelength = 605 nm, used as the model nanocrystals here) in 20 mL organic solvent (chloroform for producing ....

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Wyniki

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.......

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Dyskusje

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.......

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Materiały

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