Name: obtention of giant unilamellar hybrid vesicles by electroformation and measurement of their mechanical properties by micropipette aspiration
Uploaded: 2020-01-19T13:00:00
Description: Watch this Scientific Journal Video about Obtention of Giant Unilamellar Hybrid Vesicles by Electroformation and Measurement of their Mechanical Properties by Micropipette Aspiration at JoVE.com

The authors gratefully acknowledge the ANR for financial support (ANR Sysa).

1. Fabricating micropipettes
NOTE: Here, micropipettes with an inner diameter ranging from 6 to 12 &#181;m and a taper length around 3-4 mm are necessary. A detailed method of manufacturing micropipette is described in the following.
<ol>
	<li>Place the borosilicate glass capillary in the drawbar of the puller and fix one of the ends by tightening the knob.</li>
	<li>Carefully slide the glass through the holes at the side of the heater chamber.</li>
	<li>Tighten down the clamping knob at the...

<ol>
	<li>Bangham, A. D., Standish, M. M., Watkins, J. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Diffusion+of+univalent+ions+across+the+lamellae+of+swollen+phospholipids.">Diffusion of univalent ions across the lamellae of swollen phospholipids.</a> Journal of Molecular Biology. 13 (1), (1965).</li><li>Discher, D. E., Eisenberg, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Polymer+vesicles.">Polymer vesicles.</a> Science. 297 (5583), 967-973 (2002).</li><li>Hammer, D., 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=Polymersomes:+vesicles+from+block+copolymers.">Polymersomes: vesicles from block copolymers.</a> Annals of Biomedical Engineering. 28 (SUPPL. 1), (2000).</li><li>Le Meins, J. F., Schatz, C., Lecommandoux, S., Sandre, O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hybrid+polymer/lipid+vesicles:+state+of+the+art+and+future+perspectives.">Hybrid polymer/lipid vesicles: state of the art and future perspectives.</a> Materials Today. 16 (10), 397-402 (2013).</li><li>Schulz, M., Binder, W. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mixed+Hybrid+Lipid/Polymer+Vesicles+as+a+Novel+Membrane+Platform.">Mixed Hybrid Lipid/Polymer Vesicles as a Novel Membrane Platform.</a> Macromolecular Rapid Communications. 36, 2031-2041 (2015).</li><li>Schneider, M. B., Jenkins, J. T., Webb, W. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thermal+fluctuations+of+large+quasi-spherical+bimolecular+phospholipid+vesicles.">Thermal fluctuations of large quasi-spherical bimolecular phospholipid vesicles.</a> Journal De Physique. 45 (9), 1457-1472 (1984).</li><li>Dimova, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recent+developments+in+the+field+of+bending+rigidity+measurements+on+membranes.">Recent developments in the field of bending rigidity measurements on membranes.</a> Advances in Colloid and Interface Science. 208, 225-234 (2014).</li><li>Rodr&#237;guez-Garc&#237;a, R., 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=Polymersomes:+smart+vesicles+of+tunable+rigidity+and+permeability.">Polymersomes: smart vesicles of tunable rigidity and permeability.</a> Soft Matter. 7 (4), 1532-1542 (2011).</li><li>Angelova, M. I., Dimitrov, D. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Liposome+electroformation.">Liposome electroformation.</a> Faraday Discussions of the Chemical Society. 81, 303-311 (1986).</li><li>Dao, T. P. T., 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=Membrane+properties+of+giant+polymer+and+lipid+vesicles+obtained+by+electroformation+and+pva+gel-assisted+hydration+methods.">Membrane properties of giant polymer and lipid vesicles obtained by electroformation and pva gel-assisted hydration methods.</a> Colloids and Surfaces A: Physicochemical and Engineering Aspects. 533, 347-353 (2017).</li><li>Pereno, V., 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=Electroformation+of+Giant+Unilamellar+Vesicles+on+Stainless+Steel+Electrodes.">Electroformation of Giant Unilamellar Vesicles on Stainless Steel Electrodes.</a> ACS omega. 2 (3), 994-1002 (2017).</li><li>Evans, E., Rawicz, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Entropy-driven+tension+and+bending+elasticity+in+condensed-fluid+membranes.">Entropy-driven tension and bending elasticity in condensed-fluid membranes.</a> Physical Review Letters. 64 (17), 2094-2097 (1990).</li><li>Dao, T. P. T., 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=Modulation+of+phase+separation+at+the+micron+scale+and+nanoscale+in+giant+polymer/lipid+hybrid+unilamellar+vesicles+(GHUVs).">Modulation of phase separation at the micron scale and nanoscale in giant polymer/lipid hybrid unilamellar vesicles (GHUVs).</a> Soft Matter. 13 (3), 627-637 (2017).</li><li>Helfrich, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Elastic+properties+of+lipid+bilayers:+theory+and+possible+experiments.">Elastic properties of lipid bilayers: theory and possible experiments.</a> Z Naturforsch C. 11 (11), 693-703 (1973).</li><li>Dao, T. P. T., 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=The+combination+of+block+copolymers+and+phospholipids+to+form+giant+hybrid+unilamellar+vesicles+(GHUVs)+does+not+systematically+lead+to+&amp;#34;intermediate''+membrane+properties.">The combination of block copolymers and phospholipids to form giant hybrid unilamellar vesicles (GHUVs) does not systematically lead to &amp;#34;intermediate'' membrane properties.</a> Soft Matter. 14 (31), 6476-6484 (2018).</li><li>Shoemaker, S. D., Kyle Vanderlick, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Material+Studies+of+Lipid+Vesicles+in+the+L&#945;+and+L&#945;-Gel+Coexistence+Regimes.">Material Studies of Lipid Vesicles in the L&#945; and L&#945;-Gel Coexistence Regimes.</a> Biophysical Journal. 84 (2), 998-1009 (2003).</li><li>Longo, M. L., Ly, H. V., Dopico, A. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Methods in Membrane Lipids. , 421-437 (2007).</li><li>Chen, D., Santore, M. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hybrid+copolymer-phospholipid+vesicles:+phase+separation+resembling+mixed+phospholipid+lamellae,+but+with+mechanical+stability+and+control.">Hybrid copolymer-phospholipid vesicles: phase separation resembling mixed phospholipid lamellae, but with mechanical stability and control.</a> Soft Matter. 11 (13), 2617-2626 (2015).</li><li>Mabrouk, E., 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=Formation+and+material+properties+of+giant+liquid+crystal+polymersomes.">Formation and material properties of giant liquid crystal polymersomes.</a> Soft Matter. 5, 1870-1878 (2009).</li><li>Henriksen, J., 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=Universal+behavior+of+membranes+with+sterols.">Universal behavior of membranes with sterols.</a> Biophysical Journal. 90 (5), 1639-1649 (2006).</li><li>Ly, H. V., Block, D. E., Longo, M. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Interfacial+Tension+Effect+of+Ethanol+on+Lipid+Bilayer+Rigidity,+Stability,+and+Area/Molecule:&#8201;+A+Micropipet+Aspiration+Approach.">Interfacial Tension Effect of Ethanol on Lipid Bilayer Rigidity, Stability, and Area/Molecule:&#8201; A Micropipet Aspiration Approach.</a> Langmuir. 18 (23), 8988-8995 (2002).</li><li>Bermudez, H., Hammer, D. A., Discher, D. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+Bilayer+Thickness+on+Membrane+Bending+Rigidity.">Effect of Bilayer Thickness on Membrane Bending Rigidity.</a> Langmuir. 20, 540-543 (2004).</li></ol>

The coating of the micropipette is one of the key points to obtain reliable measurements. Adhesion of the vesicle to the micropipette must be prevented, and a coating is commonly used in literature17,18,19,20,21, with BSA, &#946;-casein or surfasil. Details of the coating procedure are rarely mentioned.
Dissolution of the BSA should...

Giant vesicles obtained from phospholipids (liposomes) have been widely used since the 1970s as the basic cell membrane model1. In the late 1990s, vesicular morphologies obtained from the self-assembly of copolymers, named polymersomes in reference to their lipid analogs2,3, rapidly appeared as an interesting alternative to liposomes that possess weak mechanical stability and poor modular chemical functionality. However, their cell biomimetic character is rather limited compared to liposomes since the latter are composed of phospholipids, the main component of the cell membrane. Furthermore, their low membrane permeability can be an issue in some applications like drug delivery where controlled diffusion of species through the membrane is required. Recently, the association of phospholipids with block copolymers to design hybrid polymer-lipid vesicles and membranes has been the subject of an increasing number of studies4,5. The main idea is to design entities that synergistically combine the benefits of each component (bio-functionality and permeability of lipid bilayers with the mechanical stability and chemical versatility of polymer membranes), which can be exploited in different applications: controlled and targeted drug delivery, biomolecular recognition within biosensors for diagnosis, functional membranes for artificial cells, development of bio-inspired micro-/nano-reactors.
Nowadays, different scientific communities (biochemists, chemists, biophysicists, physico-chemists, biologists) have increasing interest in development of a more advanced cell membrane model. Here, our goal is to present, as detailed as possible, existing methodologies (electroformation, micropipette aspiration) to obtain and characterize the mechanical properties of giant vesicles and the recent &#34;advanced&#34; cell membrane models that are hybrid polymer lipid giant vesicles4,5.
The purpose of these methods is to obtain reliable measurement of the area compressibility and bending moduli of the membrane as well as their lysis stress and strain. One of the most common techniques existing to measure bending rigidity of a giant vesicle is fluctuation analysis6,7, based on direct video microscope observation; but this requires large visible membrane fluctuation, and is not systematically obtained on thick membranes (e.g. polymersomes). Area compressibility modulus can be experimentally determined using the Langmuir Blodgett technique but most often on a monolayer8. The micropipette aspiration technique allows the measurement of both moduli on a bilayer forming giant unilamellar vesicle (GUV) in one experiment.
The following method is appropriate for all amphiphilic molecules or macromolecules able to form bilayers and, consequently, vesicles by electroformation. This requires a fluid character of the bilayer at the temperature of electroformation.

<table>
	<tbody>
		<tr>
			<td>Required equipment and materials for micropipette design</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Borosilicate Glass Capillaries</td>
			<td>World Precision Instruments</td>
			<td>1B100-4</td>
			<td>external and internal diameter of 1mm and 0.58 mm respectively.</td>
		</tr>
		<tr>
			<td>Filament installed</td>
			<td>Sutter Instrument Co.</td>
			<td>FB255B</td>
			<td>2.5mm*2.5mm Box Filament</td>
		</tr>
		<tr>
			<td>Flaming/Brown Micropipette Puller</td>
			<td>Sutter Instrument Co.</td>
			<td>Model P-97</td>
			<td></td>
		</tr>
		<tr>
			<td>Microforge</td>
			<td>NARISHGE Co.</td>
			<td>MF-900</td>
			<td>fitted with two objectives (10x and 32x)</td>
		</tr>
		<tr>
			<td>Materials for coating pipette tips with BSA</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Bovine Serum Albumin Fraction V (BSA)</td>
			<td>Sigma-Aldrich</td>
			<td>10735078001</td>
			<td></td>
		</tr>
		<tr>
			<td>Disposable 1 ml syringe Luer Tip</td>
			<td>Codan</td>
			<td>62.1612</td>
			<td></td>
		</tr>
		<tr>
			<td>Disposable 10 ml syringe Luer Tip</td>
			<td>Codan</td>
			<td>626616</td>
			<td></td>
		</tr>
		<tr>
			<td>Disposable 5 ml syringe Luer Tip</td>
			<td>Codan</td>
			<td>62.5607</td>
			<td></td>
		</tr>
		<tr>
			<td>Disposable acetate cellulose filter</td>
			<td>Cluzeau Info Labo</td>
			<td>L5003SPA</td>
			<td>Pore size: 0.22&#181;m, diameter: 25mm</td>
		</tr>
		<tr>
			<td>Flexible Fused Silica Capillary Tubing</td>
			<td>Polymicro Technologies.</td>
			<td>TSP530660</td>
			<td>Inner Diameter 536&#181;m, Outer Diameter 660&#181;m,</td>
		</tr>
		<tr>
			<td>Glucose</td>
			<td>Sigma-Aldrich</td>
			<td>G5767</td>
			<td></td>
		</tr>
		<tr>
			<td>Syringe 500 &#181;L luer Lock GASTIGHT</td>
			<td>Hamilton Syringe Company</td>
			<td>1750</td>
			<td></td>
		</tr>
		<tr>
			<td>Test tube rotatory mixer</td>
			<td>Labinco</td>
			<td>28210109</td>
			<td></td>
		</tr>
		<tr>
			<td>Micromanipulation Set up</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Aluminum Optical Rail, 1000 mm Length, M4 threads, X48 Series</td>
			<td>Newport</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Damped Optical Table</td>
			<td>Newport</td>
			<td></td>
			<td>used as support of microscope to prevent external vibrations.</td>
		</tr>
		<tr>
			<td>Micromanipulator</td>
			<td>Eppendorf</td>
			<td>Patchman NP 2</td>
			<td>The module unit (motor unit for X, Y and Z movement) is mounted on the inverted microscope by the way of an adapter.</td>
		</tr>
		<tr>
			<td>Micrometer</td>
			<td>Mitutoyo Corporation</td>
			<td>350-354-10</td>
			<td>Digimatic LCD Micrometer Head 25,4 mm Range 0,001 mm</td>
		</tr>
		<tr>
			<td>Plexiglass water reservoir (100 ml)</td>
			<td>Home made</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>TCS SP5 inverted confocal microscope (DMI6000) equipped with a resonant scanner and a water immersion objective (HCX APO L 40x/0.80 WU-V-I).</td>
			<td>Leica</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>X48 Rail Carrier 80 mm Length,with 1/4-20, 8-32 and 4-40 thread</td>
			<td>Newport</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Materials for sucrose and amphiphile solution preparation</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td><a href="https://www.sigmaaldrich.com/catalog/substance/2oleoyl1palmitoylsnglycero3phosphocholine760082685331611" target="_blank">2-Oleoyl-1-palmitoyl-sn-glycero-3-phosphocholine</a></td>
			<td>Sigma-Aldrich</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Chloroform</td>
			<td>VWR</td>
			<td>22711.244</td>
			<td></td>
		</tr>
		<tr>
			<td>L-&#945;-Phosphatidylethanolamine-N-(lissamine rhodamine B sulfonyl)</td>
			<td>Sigma-Aldrich</td>
			<td>810146C</td>
			<td>Rhodamine tagged lipid</td>
		</tr>
		<tr>
			<td>Sucrose</td>
			<td>Sigma-Aldrich</td>
			<td>S7903</td>
			<td></td>
		</tr>
		<tr>
			<td>Electroformation set up</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>10 &#181;L glass capillary ringcaps</td>
			<td>Hirschmann</td>
			<td>9600110</td>
			<td></td>
		</tr>
		<tr>
			<td>Disposable 1 ml syringe Luer Tip</td>
			<td>Codan</td>
			<td>62.1612</td>
			<td></td>
		</tr>
		<tr>
			<td>H Grease</td>
			<td>Apiezon</td>
			<td>Apiezon H Grease</td>
			<td>Silicon-free grease</td>
		</tr>
		<tr>
			<td>Indium tin oxide coated glass slides</td>
			<td>Sigma-Aldrich</td>
			<td>703184</td>
			<td></td>
		</tr>
		<tr>
			<td>Needle</td>
			<td>Terumo</td>
			<td>AN2138R1</td>
			<td>0.8 x 38 mm</td>
		</tr>
		<tr>
			<td>Ohmmeter (Multimeter)</td>
			<td>Voltcraft</td>
			<td>VC140</td>
			<td></td>
		</tr>
		<tr>
			<td>Toluene</td>
			<td>VWR</td>
			<td>28676.297</td>
			<td></td>
		</tr>
		<tr>
			<td>Voltage generator</td>
			<td>Keysight</td>
			<td>33210A</td>
			<td></td>
		</tr>
	</tbody>
</table>

obtention of giant unilamellar hybrid vesicles by electroformation and measurement of their mechanical properties by micropipette aspiration

Giant vesicles obtained from phospholipids and copolymers can be exploited in different applications: controlled and targeted drug delivery, biomolecular recognition within biosensors for diagnosis, functional membranes for artificial cells, and development of bioinspired micro/nano-reactors. In all of these applications, the characterization of their membrane properties is of fundamental importance. Among existing characterization techniques, micropipette aspiration, pioneered by E. Evans, allows the measurement of mechanical properties of the membrane such as area compressibility modulus, bending modulus and lysis stress and strain. Here, we present all the methodologies and detailed procedures to obtain giant vesicles from the thin film of a lipid or copolymer (or both), the manufacturing and surface treatment of micropipettes, and the aspiration procedure leading to the measurement of all the parameters previously mentioned.

With the protocol aforementioned, we have studied different synthetic giant unilamellar vesicle (GUV), obtained from a phospholipid: 2-oleoyl-1-palmitoyl-sn-glycero-3-phosphocholine (POPC), a triblock copolymer: Poly(ethyleneoxide)-b-Poly(dimethylsiloxane)-b-Poly(ethyleneoxide) (PEO12-b-PDMS43-b-PEO12) synthesized in a previous study13, and a diblock copolymer Poly(dimethylsiloxane)-b...

Watch this Scientific Journal Video about Obtention of Giant Unilamellar Hybrid Vesicles by Electroformation and Measurement of their Mechanical Properties by Micropipette Aspiration at JoVE.com

Obtention of Giant Unilamellar Hybrid Vesicles by Electroformation and Measurement of their Mechanical Properties by Micropipette Aspiration

The goal of the protocol is to reliably measure membrane mechanical properties of giant vesicles by micropipette aspiration.

Giant vesicles obtained from phospholipids and copolymers can be exploited in different applications: controlled and targeted drug delivery, biomolecular ...

This protocol facilitates a reliable measurement of the membrane mechanical properties of synthetic and real polymer lipid vesicle using a micropipette aspiration technique. This is the only technique that allows membrane flexibility and instability to be stretched to be assessed in single experiments. This protocol involves a series of procedures from vesicle preparation to the mechanical assessment.It is very important to be patient and to solve any technical issues as they arise. Visualization on these techniques is critical for understanding how to properly treat the capillary surface and how to perform the mandatory prestress step. Showing up the vesicle without defects.Demonstrating procedure will be Martin Fauquignon, a PhD student from the laboratory working on the development of hybrid polymer lipid vesicles. Before beginning the procedure place cold glass micropipette capillaries vertically into holders. And lower the holders until the tips are immersed in freshly prepared glucose bovine serum albumin solution overnight.By the next morning the solution should have risen about one centimeter into the tips by capillary action. Using a 500 microliter glass syringe, equipped with a flexible fused silica capillary, fill each pipette with the glucose solution. Then aspirate the solution from each pipette, before refilling the pipettes with fresh glucose solution several times until all of the serum as been removed.To prepare an electroformation chamber, first clean ITO slides with an appropriate organic solvent, and identify the conductive surface with an Ohmeter. Attach electrical wires onto the conductive side of each slide with adhesive tape. Dip one capillary into ampivial solution until about 5 microliters of the solution has been collected by capillary action.Place the loaded capillary into contact with the center of one glass ITO plate and gently spread the solution across the slide. When the solvent has completely evaporated, apply the solution two more times as just demonstrated. before adding a layer of silicon-free grease on both sides of the opened O-ring spacer around the area of deposition.Next, place the conductive face of a second ITO glass plate on the top of the spacer, and place the electroformation chamber under vacuum for 3 hours to remove any traces of organic solvent. For the electroformation of Giant Unilamellar Vesicles, Plug the electric wires into the generator. Set the generator frequency to 10 Hertz, and the amplitude to 2 Volts, peak to peak.When the voltage has been set, use a syringe equipped with an 0.8 millimeter inner diameter needle to inject one milliliter of 0.1 molar sucrose solution into the chamber, and leave the chamber under the applied voltage and frequency for 75 minutes. At the end of the electroformation, turn off the generator. And use the one milliliter syringe to aspirate a small volume of solution until an air bubble is produced inside the chamber.Tilt the chamber slightly to move the bubble into the chamber, and to help the vesicles detach from the slide surface. And aspirate the entire volume of solution into the syringe. Then, transfer the vesicle solution into a one milliliter plastic tube.To set up the materials for the micromanipulation, aspirate to create a water flow, a tank of pure water, to one holder. And lightly tap while raising the tank to eliminate any air bubbles, and to create positive pressure. Fill a serum coated capillary with fresh glucose solution until a drop forms at the tip.Remove the syringe tubing from the metal holder to create a slight water flow at the end of the holder, and turn the capillary upside-down to connect the glucose drop to the water flow. Then, screw the capillary and the holder together. To position the pipette, glue two glass slides from a custom-made aluminum stage together with vacuum grease.And install the slides onto a microscope stage. Using a one milliliter pipette, form a meniscus between the two slides with 0.1 molar glucose. Place the pipette and its holder on the motor unit of the micromanipulator.Tighten the clamping knob, and use the control panel joystick in coarse mode. Lower the micropipette near the glucose meniscus. Use the fine mode to adjust the position of the tip to the center of the meniscus.Immerse the tip in the glucose to clean its outer and inner surfaces. After a few minutes, withdraw the capillary from the meniscus and replace the glucose with a fresh meniscus. Aspirate two microliters of Giant Unilamellar Vesicles in 0.1 molar sucrose, into a 20 milliliter micropipette tip.Introduce the vesicles into the meniscus. Use the microscope to observe the vesicles at the bottom of the slide chamber. When the vesicles are slightly deflated, reinsert the suction pipette, and focus on the tip of the pipette.Then set the baseline height of the water tank to the pressure at which the motion of the particles is stopped. Surround the meniscus with mineral oil to prevent evaporation. To perform a micropipette aspiration experiment, lower the pipette tip into the meniscus.Create a small amount of suction pressure to aspirate a vesicle. The membrane of the selected vesicle should slightly fluctuate and should not present any visible defects. Use the micromanipulator to raise the pipette to a higher level to isolate the aspirated vesicle from other vesicles.Lower the water tank to approximately 10 centimeters to prestress the vesicle before raising the tank to return the pressure to the initial value. From a height of 0.5 centimeters, slowly decrease the suction pressure until a pressure at which the membrane fluctuates is reached. Then increase the pressure to clearly visualize a tongue in the tip, the projection length of a few microns.To determine the bending modulus, increase the suction pressure, one micrometer at a time in a stepwise manner. Until 0.5 to 0.8 milliNewtons per meter is reached. Waiting five seconds, and taking a snapshot of the tongue after each step.To determine the area compressibility modulus, and lysis tension and strain continue to increase the suction pressure from 0.5 milliNewtons per meter until the rupture tension is reached. In this representative experiment the area compressibility modulus and lysis strain for POPC were in perfect agreement with that expected from the literature. In this table typical values for the polymersomes obtained can be observed.Note that the toughness of the membrane obtained from diblock copolymers is far greater than those obtained from triblock copolymer. Interestingly, using the diblock copolymer, it is possible to obtain a Giant Hybrid Unilamilar Lipid Polymer Vesicles that demonstrate a more robust toughness than that measured for liposomes. This protocol can be helpful for measuring vesicle with a pipette, for example, to measure the permeability of the membrane through asmatic shock.Be sure to complete each step with rigor and precision, especially when setting up the tribune connection. This technique has been exploited to understand physical origin of membrane fission, through the measurement of line tension at the main boundaries in modified vesicles.

obtention-giant-unilamellar-hybrid-vesicles-electroformation

Research

JoVE Journal

Chemistry

Fabricating Nanogaps by Nanoskiving

There are several methods of fabricating nanogaps with controlled spacings, but the precise control over the sub-nanometer spacing between two electrodes-and generating them in practical quantities-is still challenging. The preparation of nanogap electrodes using nanoskiving, which is a form of edge lithography, is a fast, simple and powerful technique. This method is an entirely mechanical process which does not include any photo- or electron-beam lithographic steps and does not require any special equipment or infrastructure such as clean rooms. Nanoskiving is used to fabricate electrically addressable nanogaps with control over all three dimensions; the smallest dimension of these structures is defined by the thickness of the sacrificial layer (Al or Ag) or self-assembled monolayers. These wires can be manually positioned by transporting them on drops of water and are directly electrically-addressable; no further lithography is required to connect them to an electrometer.

The fabrication of electrically addressable, high-aspect-ratio (> 1000:1) metal nanowires separated by gaps of single nanometers using either sacrificial layers of aluminum and silver or self-assembled monolayers as templates is described. These nanogap structures are fabricated without a clean room or any photo- or electron-beam lithographic processes by a form of edge lithography known as nanoskiving.

There are several methods of fabricating nanogaps with controlled spacings, but the precise control over the sub-nanometer spacing between two ...

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 ...

Synthesis of Non-uniformly Pr-doped SrTiO3 Ceramics and Their Thermoelectric Properties

We demonstrate a novel synthesis strategy for the preparation of Pr-doped SrTiO3 ceramics via a combination of solid state reaction and spark plasma sintering techniques. Polycrystalline ceramics possessing a unique morphology can be achieved by optimizing the process parameters, particularly spark plasma sintering heating rate. The phase and morphology of the synthesized ceramics were investigated in detail using X-ray diffraction, scanning electron microcopy and energy-dispersive X-ray spectroscopy. It was observed that the grains of these bulk Pr-doped SrTiO3 ceramics were enhanced with Pr-rich grain boundaries. Electronic and thermal transport properties were also investigated as a function of temperature and doping concentration. Such a microstructure was found to give rise to improved thermoelectric properties. Specifically, it resulted in a significant improvement in carrier mobility and the thermoelectric power factor. Simultaneously, it also led to a marked reduction in the thermal conductivity. As a result, a significant improvement (> 30%) in the thermoelectric figure of merit was achieved for the whole temperature range over all previously reported maximum values for SrTiO3-based ceramics. This synthesis demonstrates the steps for the preparation of bulk polycrystalline ceramics of non-uniformly Pr-doped SrTiO3.

Synthesis of Non-uniformly Pr-doped SrTiO3 Ceramics and Their Thermoelectric Properties

A protocol for the synthesis and processing of polycrystalline SrTiO3 ceramics doped non-uniformly with Pr is presented along with the investigation of their thermoelectric properties.

We demonstrate a novel synthesis strategy for the preparation of Pr-doped SrTiO3 ceramics via a combination of solid state reaction and spark plasma ...

Synthesis and Characterization of Fe-doped Aluminosilicate Nanotubes with Enhanced Electron Conductive Properties

The goal of the protocol is to synthesize Fe-doped aluminosilicate nanotubes of the imogolite type with the formula (OH)3Al2-xFexO3SiOH. Doping with Fe aims at lowering the band gap of imogolite, an insulator with the chemical formula (OH)3Al2O3SiOH, and at modifying its adsorption properties towards azo-dyes, an important class of organic pollutants of both wastewater and groundwater.
Fe-doped nanotubes are obtained in two ways: by direct synthesis, where FeCl3 is added to an aqueous mixture of the Si and Al precursors, and by post-synthesis loading, where preformed nanotubes are put in contact with a FeCl3&#8226;6H2O aqueous solution. In both synthesis methods, isomorphic substitution of Al3+ by Fe3+ occurs, preserving the nanotube structure. Isomorphic substitution is indeed limited to a mass fraction of ~1.0% Fe, since at a higher Fe content (i.e., a mass fraction of 1.4% Fe), Fe2O3 clusters form, especially when the loading procedure is adopted. The physicochemical properties of the materials are studied by means of X-ray powder diffraction (XRD), N2 sorption isotherms at -196 &#176;C, high resolution transmission electron microscopy (HRTEM), diffuse reflectance (DR) UV-Vis spectroscopy, and &#950;-potential measurements. The most relevant result is the possibility to replace Al3+ ions (located on the outer surface of the nanotubes) by post-synthesis loading on preformed imogolite without perturbing the delicate hydrolysis equilibria occurring during nanotube formation. During the loading procedure, an anionic exchange occurs, where Al3+ ions on the outer surface of the nanotubes are replaced by Fe3+ ions. In Fe-doped aluminosilicate nanotubes, isomorphic substitution of Al3+ by Fe3+ is found to affect the band gap of doped imogolite. Nonetheless, Fe3+ sites on the outer surface of nanotubes are able to coordinate organic moieties, like the azo-dye Acid Orange 7, through a ligand-displacement mechanism occurring in an aqueous solution.

Here, we present a protocol to synthesize and characterize Fe-doped aluminosilicate nanotubes. The materials are obtained by either sol-gel synthesis upon addition of FeCl3&#8226;6H2O to the mixture containing the Si and Al precursors or by post-synthesis ionic exchange of preformed aluminosilicate nanotubes.

The goal of the protocol is to synthesize Fe-doped aluminosilicate nanotubes of the imogolite type with the formula (OH)3Al2-xFexO3SiOH. Doping with Fe ...

Measurement of Particle Size Distribution in Turbid Solutions by Dynamic Light Scattering Microscopy

A protocol for measuring polydispersity of concentrated polymer solutions using dynamic light scattering is described. Dynamic light scattering is a technique used to measure the size distribution of polymer solutions or colloidal particles. Although this technique is widely used for the assessment of polymer solutions, it is difficult to measure the particle size in concentrated solutions due to the multiple scattering effect or strong light absorption. Therefore, the concentrated solutions should be diluted before measurement. Implementation of the confocal optical component in a dynamic light scattering microscope1 helps to overcome this barrier. Using such a microscopic system, both transparent and turbid systems can be analyzed under the same experimental setup without a dilution. As a representative example, a size distribution measurement of a temperature-responsive polymer solution was performed. The sizes of the polymer chains in an aqueous solution were several tens of nanometers at a temperature below the lower critical solution temperature (LCST). In contrast, the sizes increased to more than 1.0 &#181;m when above the LCST. This result is consistent with the observation that the solution turned turbid above the LCST.

A protocol for the direct measurement of particle size distribution in concentrated solutions using dynamic light scattering microscopy is presented.

A protocol for measuring polydispersity of concentrated polymer solutions using dynamic light scattering is described. Dynamic light scattering is a ...

TiO2-coated Hollow Glass Microspheres with Superhydrophobic and High IR-reflective Properties Synthesized by a Soft-chemistry Method

This manuscript proposes a soft-chemistry method to develop superhydrophobic and highly IR-reflective hollow glass microspheres (HGM). The anatase TiO2 and a superhydrophobic agent were coated on the HGM surface in one step. TBT and PFOTES were selected as the Ti source and the superhydrophobic agent, respectively. They were both coated on the HGM, and after the hydrothermal process, the TBT turned to anatase TiO2. In this way, a PFOTES/TiO2-coated HGM (MCHGM) was prepared. For comparison, PFOTES single-coated HGM (F-SCHGM) and TiO2 single-coated HGM (Ti-SCHGM) were synthesized as well. The PFOTES and TiO2 coatings on the HGM surface were demonstrated through X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive detector (EDS) characterizations. The MCHGM showed a higher contact angle (153&#176;) but a lower sliding angle (16&#176;) than F-SCHGM, with a contact angle of 141.2&#176; and a sliding angle of 67&#176;. In addition, both Ti-SCHGM and MCHGM displayed similar IR reflectivity values, which were about 5.8% higher than the original HGM and F-SCHGM. Also, the PFOTES coating barely changed the thermal conductivity. Therefore, F-SCHGM, with a thermal conductivity of 0.0479 W/(m&#183;K), was quite like the original HGM, which was 0.0475 W/(m&#183;K). MCHGM and Ti-SCHGM were also similar. Their thermal conductivity values were 0.0543 W/(m&#183;K) and 0.0543 W/(m&#183;K), respectively. The TiO2 coating slightly increased the thermal conductivity, but with the increase in reflectivity, the overall heat-insulation property was enhanced. Finally, since the IR-reflecting property is provided by the HGM coating, if the coating is fouled, the reflectivity decreases. Therefore, with the superhydrophobic coating, the surface is protected from fouling, and its lifetime is also prolonged.

TiO2-coated Hollow Glass Microspheres with Superhydrophobic and High IR-reflective Properties Synthesized by a Soft-chemistry Method

This manuscript proposes a soft-chemistry method to synthesize superhydrophobic, TiO2-coated hollow glass microspheres (HGM) with high IR-reflective properties.

This manuscript proposes a soft-chemistry method to develop superhydrophobic and highly IR-reflective hollow glass microspheres (HGM). The anatase TiO2 ...

Fabrication and Testing of Photonic Thermometers

In recent years, a push for developing novel silicon photonic devices for telecommunications has generated a vast knowledge base that is now being leveraged for developing sophisticated photonic sensors. Silicon photonic sensors seek to exploit the strong confinement of light in nano-waveguides to transduce changes in physical state to changes in resonance frequency. In the case of thermometry, the thermo-optic coefficient, i.e., changes in refractive index due to temperature, causes the resonant frequency of the photonic device such as a Bragg grating to drift with temperature. We are developing a suite of photonic devices that leverage recent advances in telecom compatible light sources to fabricate cost-effective photonic temperature sensors, which can be deployed in a wide variety of settings ranging from controlled laboratory conditions, to the noisy environment of a factory floor or a residence. In this manuscript, we detail our protocol for the fabrication and testing of photonic thermometers.

We describe the process of fabrication and testing of photonic thermometers.

In recent years, a push for developing novel silicon photonic devices for telecommunications has generated a vast knowledge base that is now being ...

Preparation and Characterization of C60/Graphene Hybrid Nanostructures

Physical thermal deposition in a high vacuum environment is a clean and controllable method for fabricating novel molecular nanostructures on graphene. We present methods for depositing and passively manipulating C60 molecules on rippled graphene that advance the pursuit of realizing applications involving 1D C60/graphene hybrid structures. The techniques applied in this exposition are geared towards high vacuum systems with preparation areas capable of supporting molecular deposition as well as thermal annealing of the samples. We focus on C60 deposition at low pressure using a homemade Knudsen cell connected to a scanning tunneling microscopy (STM) system. The number of molecules deposited is regulated by controlling the temperature of the Knudsen cell and the deposition time. One-dimensional (1D) C60 chain structures with widths of two to three molecules can be prepared via tuning of the experimental conditions. The surface mobility of the C60 molecules increases with annealing temperature allowing them to move within the periodic potential of the rippled graphene. Using this mechanism, it is possible to control the transition of 1D C60 chain structures to a hexagonal close packed quasi-1D stripe structure.

Preparation and Characterization of C60/Graphene Hybrid Nanostructures

Here we present a protocol for the fabrication of C60/graphene hybrid nanostructures by physical thermal evaporation. Particularly, the proper manipulation of deposition and annealing conditions allow the control over the creation of 1D and quasi 1D C60 structures on rippled graphene.

Physical thermal deposition in a high vacuum environment is a clean and controllable method for fabricating novel molecular nanostructures on graphene. We ...

Membrane Remodeling of Giant Vesicles in Response to Localized Calcium Ion Gradients

In a wide variety of fundamental cell processes, such as membrane trafficking and apoptosis, cell membrane shape transitions occur concurrently with local variations in calcium ion concentration. The main molecular components involved in these processes have been identified; however, the specific interplay between calcium ion gradients and the lipids within the cell membrane is far less known, mainly due to the complex nature of biological cells and the difficultly of observation schemes. To bridge this gap, a synthetic approach is successfully implemented to reveal the localized effect of calcium ions on cell membrane mimics. Establishing a mimic to resemble the conditions within a cell is a severalfold problem. First, an adequate biomimetic model with appropriate dimensions and membrane composition is required to capture the physical properties of cells. Second, a micromanipulation setup is needed to deliver a small amount of calcium ions to a particular membrane location. Finally, an observation scheme is required to detect and record the response of the lipid membrane to the external stimulation. This article offers a detailed biomimetic approach for studying the calcium ion-membrane interaction, where a lipid vesicle system, consisting of a giant unilamellar vesicle (GUV) connected to a multilamellar vesicle (MLV), is exposed to a localized calcium gradient formed using a microinjection system. The dynamics of the ionic influence on the membrane were observed using fluorescence microscopy and recorded at video frame rates. As a result of the membrane stimulation, highly curved membrane tubular protrusions (MTPs) formed inside the GUV, oriented away from the membrane. The described approach induces the remodeling of the lipid membrane and MTP production in an entirely contactless and controlled manner. This approach introduces a means to address the details of calcium ion-membrane interactions, providing new avenues to study the mechanisms of cell membrane reshaping.

We present a technique for contactless micromanipulation of vesicles, using localized calcium ion gradients. Microinjection of a calcium ion solution, in the vicinity of a giant lipid vesicle, is utilized to remodel the lipid membrane, resulting in the production of membrane tubular protrusions.

In a wide variety of fundamental cell processes, such as membrane trafficking and apoptosis, cell membrane shape transitions occur concurrently with local ...

Disentangling High Strength Copolymer Aramid Fibers to Enable the Determination of Their Mechanical Properties

Traditionally, soft body armor has been made from poly(p-phenylene terephthalamide) (PPTA) and ultra-high molecular weight polyethylene. However, to diversify the fiber choices in the United States body armor market, copolymer fibers based on the combination of 5-amino-2-(p-aminophenyl) benzimidazole (PBIA) and the more conventional PPTA were introduced. Little is known regarding the long-term stability of these fibers, but as condensation polymers, they are expected to have potential sensitivity to moisture and humidity. Therefore, characterizing the strength of the materials and understanding their vulnerability to environmental conditions is important for evaluating their use lifetime in safety applications. Ballistic resistance and other critical structural properties of these fibers are predicated on their strength. To accurately determine the strength of the individual fibers, it is necessary to disentangle them from the yarn without introducing any damage. Three aramid-based copolymer fibers were selected for the study. The fibers were washed with acetone followed by methanol to remove an organic coating that held the individual fibers in each yarn bundle together. This coating makes it difficult to separate single fibers from the yarn bundle for mechanical testing without damaging the fibers and affecting their strength. After washing, fourier transform infrared (FTIR) spectroscopy was performed on both washed and unwashed samples and the results were compared. This experiment has shown that there are no significant variations in the spectra of poly(p-phenylene-benzimidazole-terephthalamide-co-p-phenylene terephthalamide) (PBIA-co-PPTA1) and PBIA-co-PPTA3 after washing, and only a small variation in intensity for PBIA. This indicates that the acetone and methanol rinses are not adversely affecting the fibers and causing chemical degradation. Additionally, single fiber tensile testing was performed on the washed fibers to characterize their initial tensile strength and strain to failure, and compare those to other reported values. Iterative procedural development was necessary to find a successful method for performing tensile testing on these fibers.

The primary goal of the study is to develop a protocol to prepare consistent specimens for accurate mechanical testing of high strength copolymer aramid fibers, by removing a coating and disentangling the individual fiber strands without introducing significant chemical or physical degradation.

Traditionally, soft body armor has been made from poly(p-phenylene terephthalamide) (PPTA) and ultra-high molecular weight polyethylene. However, to ...