Name: targeted plasma membrane delivery of a hydrophobic cargo encapsulated in a liquid crystal nanoparticle carrier
Uploaded: 2017-02-08T15:00:00
Description: Watch this Scientific Journal Video about Targeted Plasma Membrane Delivery of a Hydrophobic Cargo Encapsulated in a Liquid Crystal Nanoparticle Carrier at JoVE.com

This work was supported by the NRL Base Funding Program (Work Unit MA041-06-41-4943). ON is supported by a National Research Council Postdoctoral Research Associateship.

1. Preparation of DiO-LCNP and DiO-LCNP-PEG-Chol
<ol>
	<li>Dissolve liquid crystalline diacrylate cross-linking agent (DACTP11, 45 mg), 3,3&#8242;-dioctadecyloxacarbocyanine perchlorate (DiO, 2 mg), and a free radical initiator (azobisisobutyronitrile, 1 mg) for polymerization in 2 ml of chloroform. Add this to an aqueous solution of acrylate-functionalized surfactant (AC10COONa, 13 mg in 7 ml).</li>
	<li>Stir the mixture for 1 hr and sonicate at 80% amplitude for 5 min to produce a miniemulsion consisting of small dro...

<ol>
	<li>Nag, O. K., Field, L. D., Chen, Y., Sangtani, A., Breger, J. C., Delehanty, J. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Controlled+actuation+of+therapeutic+nanoparticles:+an+update+on+recent+progress.">Controlled actuation of therapeutic nanoparticles: an update on recent progress.</a> Ther. Deliv. 7 (5), 335-352 (2016).</li><li>Galvao, J., Davis, B., Tilley, M., Normando, E., Duchen, M. R., Cordeiro, M. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Unexpected+low-dose+toxicity+of+the+universal+solvent+DMSO.">Unexpected low-dose toxicity of the universal solvent DMSO.</a> FASEB J. 28 (3), 1317-1330 (2014).</li><li>Spillmann, C. M., Naciri, J., Anderson, G. P., Chen, M. S., Ratna, B. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Spectral+tuning+of+organic+nanocolloids+by+controlled+molecular+interactions.">Spectral tuning of organic nanocolloids by controlled molecular interactions.</a> ACS Nano. 3 (10), 3214-3220 (2009).</li><li>Spillmann, C. M., Naciri, J., Algar, W. R., Medintz, I. L., Delehanty, J. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Multifunctional+Liquid+Crystal+Nanoparticles+for+Intracellular+Fluorescent+Imaging+and+Drug+Delivery.">Multifunctional Liquid Crystal Nanoparticles for Intracellular Fluorescent Imaging and Drug Delivery.</a> ACS Nano. 8 (7), 6986-6997 (2014).</li><li>Timmers, M., Vermijlen, D., Vekemans, K., De Zanger, R., Wisse, E., Braet, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tracing+DiO-labelled+tumour+cells+in+liver+sections+by+confocal+laser+scanning+microscopy.">Tracing DiO-labelled tumour cells in liver sections by confocal laser scanning microscopy.</a> J. Microsc. 208 (Pt 1), 65-74 (2002).</li><li>Mufson, E. J., Brady, D. R., Kordower, J. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tracing+neuronal+connections+in+postmortem+human+hippocampal+complex+with+the+carbocyanine+dye+DiI.">Tracing neuronal connections in postmortem human hippocampal complex with the carbocyanine dye DiI.</a> Neurobiol Aging. 11 (6), 649-653 (1990).</li><li>K&#246;bbert, C., Apps, R., Bechmann, I., Lanciego, J. L., Mey, J., Thanos, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Current+concepts+in+neuroanatomical+tracing.">Current concepts in neuroanatomical tracing.</a> Prog. Neurobiol. 62 (4), 327-351 (2000).</li><li>Honig, M. G., Hume, R. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dil+and+DiO:+versatile+fluorescent+dyes+for+neuronal+labelling+and+pathway+tracing.">Dil and DiO: versatile fluorescent dyes for neuronal labelling and pathway tracing.</a> Trends Neurosci. 12 (9), 333-341 (1989).</li><li>Gan, W. B., Bishop, D. L., Turney, S. G., Lichtman, 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=Vital+imaging+and+ultrastructural+analysis+of+individual+axon+terminals+labeled+by+iontophoretic+application+of+lipophilic+dye.">Vital imaging and ultrastructural analysis of individual axon terminals labeled by iontophoretic application of lipophilic dye.</a> J. Neurosci. Methods. 93 (1), 13-20 (1999).</li><li>Godement, P., Vanselow, J., Thanos, S., Bonhoeffer, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+study+in+developing+visual+systems+with+a+new+method+of+staining+neurones+and+their+processes+in+fixed+tissue.">A study in developing visual systems with a new method of staining neurones and their processes in fixed tissue.</a> Development. 101 (4), 697-713 (1987).</li><li>Ragnarson, B., Bengtsson, L., Haegerstrand, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Labeling+with+fluorescent+carbocyanine+dyes+of+cultured+endothelial+and+smooth+muscle+cells+by+growth+in+dye-containing+medium.">Labeling with fluorescent carbocyanine dyes of cultured endothelial and smooth muscle cells by growth in dye-containing medium.</a> Histochemistry. 97 (4), 329-333 (1992).</li><li>Korkotian, E., Schwarz, A., Pelled, D., Schwarzmann, G., Segal, M., Futerman, A. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Elevation+of+intracellular+glucosylceramide+levels+results+in+an+increase+in+endoplasmic+reticulum+density+and+in+functional+calcium+stores+in+cultured+neurons.">Elevation of intracellular glucosylceramide levels results in an increase in endoplasmic reticulum density and in functional calcium stores in cultured neurons.</a> J. Biol. Chem. 274 (31), 21673-21678 (1999).</li><li>Garrett, R. H., Grisham, C. 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> Biochemistry. , (2013).</li><li>Berne, B. J., Pecora, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Dynamic Light Scattering. , 41155-41159 (2000).</li><li>Kremers, G. J., Piston, D. W., Davidson, M. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Basics of FRET Microscopy. , (2016).</li><li>Chen, H., Kim, S., Li, L., Wang, S., Park, K., Cheng, J. X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Release+of+hydrophobic+molecules+from+polymer+micelles+into+cell+membranes+revealed+by+Fo&#776;rster+resonance+energy+transfer+imaging.">Release of hydrophobic molecules from polymer micelles into cell membranes revealed by Fo&#776;rster resonance energy transfer imaging.</a> Proc. Natl. Acad. Sci. U.S.A. 105, 6596-6601 (2008).</li><li>Campling, B. G., Pym, J., Galbraith, P. R., Cole, S. P. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Use+of+the+MTT+assay+for+rapid+determination+of+chemosensitivity+of+human+leukemic+blast+cells.">Use of the MTT assay for rapid determination of chemosensitivity of human leukemic blast cells.</a> Leukemia Res. 12, 823-831 (1988).</li><li>Nag, O. K., Naciri, J., Oh, E., Spillmann, C. M., Delehanty, J. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Lipid+raft-mediated+membrane+tethering+and+delivery+of+hydrophobic+cargos+from+liquid+crystal-based+nanocarriers.">Lipid raft-mediated membrane tethering and delivery of hydrophobic cargos from liquid crystal-based nanocarriers.</a> Bioconjug. Chem. 27 (4), 982-993 (2016).</li><li>Karve, S., 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=Revival+of+the+abandoned+therapeutic+wortmannin+by+nanoparticle+drug+delivery.">Revival of the abandoned therapeutic wortmannin by nanoparticle drug delivery.</a> Proc. Natl. Acad. Sci. U. S. A. 109 (21), 8230-8235 (2012).</li></ol>

A continuing goal of NMDD is the controlled targeting and delivery of drug formulations to cells and tissues, combined with simultaneous improved drug efficacy. One specific class of drug molecules for which this has posed a significant challenge is hydrophobic drugs/imaging agents that have sparingly to no solubility in aqueous media. This problem has plagued the transition of potent drugs from in vitro cell culture systems to the clinical setting and has resulted in a number of promising drug molecules being &...

Since the advent of interfacing nanomaterials (materials &#8804;100 nm in at least one dimension) with living cells, a continuing goal has been to take advantage of the unique size-dependent properties of nanoparticles (NPs) for various applications. These applications include cell and tissue labeling/imaging (both in vitro and in vivo), real-time sensing, and the controlled delivery of drugs and other cargos1. Examples of such relevant NP properties include the size-dependent emission of semiconductor nanocrystals (quantum dots, QDs); the photothermal properties of gold nanoparticles; the large loading capacity of the aqueous core of liposomes; and the ballistic conductivity of carbon allotropes, such as single-wall carbon nanotubes and graphene.
More recently, significant interest has arisen in the use of NPs for the controlled modulation of drugs and other cargos, such as contrast/imaging agents. Here, the rationale is to significantly enhance/optimize the overall solubility, delivered dose, circulation time, and eventual clearance of the drug cargo by delivering it as an NP formulation. This has come to be known as NP-mediated drug delivery (NMDD), and there are currently seven FDA-approved NP drug formulations for use in the clinic to treat various cancers and hundreds more in various stages of clinical trials. In essence, the goal is to &#34;achieve more with less;&#34; that is, to use the NP as a scaffold to deliver more drug with fewer dosing administrations by taking advantage of the large surface area:volume (e.g., hard particles, such as QDs and metal oxides) of NPs or their large interior volume for loading large cargo payloads (e.g., liposomes or micelles). The purpose here is to reduce the necessity for multiple systemically delivered dosing regimens while at the same time promoting aqueous stability and enhanced circulation, particularly for challenging hydrophobic drug cargos that, while highly effective, are sparingly soluble in aqueous media.
Thus, the goal of the work described herein was to determine the viability of using a novel NP scaffold for the specific and controlled delivery of hydrophobic cargos to the lipophilic plasma membrane bilayer. The motivation for the work was the inherent limited solubility and difficulty in the delivery of hydrophobic molecules to cells from aqueous media. Typically, the delivery of such hydrophobic molecules requires the use of organic solvents (e.g., DMSO) or amphiphilic surfactants (e.g., Poloxamers), which can be toxic and compromise cell and tissue viability2, or micelle carriers, which can have limited internal loading capacities. The NP carrier chosen here was a novel liquid crystal NP (LCNP) formulation developed previously3 and that had been shown previously to achieve a ~40-fold improvement in the efficacy of the anticancer drug doxorubicin in cultured cells4.
In the work described herein, the representative cargo selected was the potentiometric membrane dye, 3,3&#39;-dioctadecyloxacarbocyanine perchlorate (DiO). DiO is a water-insoluble dye that has been used for anterograde and retrograde tracing in living and fixed neurons, membrane potential measurements, and for general membrane labeling5,6,7,8,9. Due to its hydrophobic nature, DiO is typically added directly to cell monolayers or tissues in a crystalline form10, or it is incubated at very high concentrations (~1-20 &#181;M) after dilution from a concentration stock solution11,12.
Here, the approach was use to the LCNP platform, a multifunctional NP whose inner core is completely hydrophobic and whose surface is simultaneously hydrophilic and amenable to bioconjugation, as a delivery vehicle for DiO. DiO is incorporated into the LCNP core during synthesis, and the NP surface is then functionalized with a PEGylated cholesterol moiety to promote the membrane binding of the DiO-LCNP ensemble to the plasma membrane. This approach resulted in a delivery system that partitioned the DiO into the plasma membrane with greater fidelity and membrane residence time than the free form of DiO delivered from bulk solution (DiOfree). Further, this method showed that the LCNP-mediated delivery of DiO substantially modulates and drives the rate of specific partitioning of the dye into the lipophilic plasma membrane bilayer. This is achieved while concomitantly reducing the cytotoxicity of the free drug by ~40% by delivering it as an LCNP formulation.
It is anticipated that the methodology described herein will be a powerful enabling technique for researchers whose work involves or requires the cellular delivery of highly hydrophobic cargos that are sparingly soluble or completely insoluble in aqueous solution.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>1-ethyl-3-(3-(dimethylamino)-propyl)carbodiimide hydrochloride (EDCA)</td>
			<td>ThermoFisher</td>
			<td>E2247</td>
			<td></td>
		</tr>
		<tr>
			<td>3,3&#8242;-dioctadecyloxacarbocyanine perchlorate (DiO)</td>
			<td>Sigma Aldrich</td>
			<td>D4292-20MG</td>
			<td>Hazardous/ make stock solution in DMSO</td>
		</tr>
		<tr>
			<td>Cholesterol poly(ethylene glycol) amine hydrochloride</td>
			<td>Nanocs, Inc.</td>
			<td>PG2-AMCS-2k</td>
			<td></td>
		</tr>
		<tr>
			<td>Countess automated cell counter</td>
			<td>ThermoFisher</td>
			<td>C10227</td>
			<td></td>
		</tr>
		<tr>
			<td>Dioctadecyl-3,3,3&#8242;,3&#8242;-tetramethylindocarbocyanine perchlorate (DiI)</td>
			<td>Sigma Aldrich</td>
			<td>468495-100MG</td>
			<td>Hazardous/ make stock solution in DMSO</td>
		</tr>
		<tr>
			<td>Dulbecco&#39;s Modified Eagle&#39;s Medium (DMEM)</td>
			<td>ThermoFisher</td>
			<td>21063045</td>
			<td>Warm in 37&#176;C before use</td>
		</tr>
		<tr>
			<td>Dulbecco&#39;s Phosphate Buffered Saline (DPBS)</td>
			<td>ThermoFisher</td>
			<td>14040182</td>
			<td>Warm in 37&#176;C before use</td>
		</tr>
		<tr>
			<td>Dynamic light scattering instrument</td>
			<td>ZetaSizer NanoSeries (Malvern Instruments Ltd., Worcestershire, UK)</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Fibronectin Bovine Protein, Plasma</td>
			<td>ThermoFisher</td>
			<td>33010018</td>
			<td>Make stock solution 1mg/mL using DPBS. Use 20-30 &#181;g/mL for coating MetTek dish, 2 h@ 37&#176;C</td>
		</tr>
		<tr>
			<td>Formaldehyde (16%, W/V)</td>
			<td>ThermoFisher</td>
			<td>28906</td>
			<td>Hazardous, dilute to 4% using DPBS</td>
		</tr>
		<tr>
			<td>Human embryonic kidney cells (HEK 293T/17)</td>
			<td>American Type Culture Collection</td>
			<td>ATCC&#174; CRL-11268&#8482;</td>
			<td></td>
		</tr>
		<tr>
			<td>Live cell imaging solution (LCIS)</td>
			<td>ThermoFisher</td>
			<td>A14291DJ</td>
			<td>Warm in 37&#176;C before use</td>
		</tr>
		<tr>
			<td>MatTek 14 mm # 1.0 coverglass insert cell culture dish</td>
			<td>MatTek corporation</td>
			<td>P35G-1.0-14-C</td>
			<td></td>
		</tr>
		<tr>
			<td>Modified Eagle Medium (DMEM) containing 25 mM HEPES</td>
			<td>ThermoFisher</td>
			<td>21063045</td>
			<td>Warm in 37&#176;C before use</td>
		</tr>
		<tr>
			<td>N-hydroxysulfosuccinimide sodium salt (NHSS)</td>
			<td>ThermoFisher</td>
			<td>24510</td>
			<td></td>
		</tr>
		<tr>
			<td>Nikon A1si spectral confocal microscope</td>
			<td>Nikon Instruments</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Trypan Blue Stain (0.4%)&#160;</td>
			<td>ThermoFisher</td>
			<td>T10282</td>
			<td>mix as a 50% to the cell suspension before counting the cells</td>
		</tr>
		<tr>
			<td>Zeta potential instrument</td>
			<td>ZetaSizer NanoSeries (Malvern Instruments Ltd., Worcestershire, UK)</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Ultrasonic Processor</td>
			<td>Sonics and Materials Inc</td>
			<td>GEX 600-5</td>
			<td></td>
		</tr>
		<tr>
			<td>Mini Cetntrifuge</td>
			<td>Benchmark</td>
			<td>Mini-fuge-04477</td>
			<td></td>
		</tr>
		<tr>
			<td>PD-10 Sephadex&#8482; G-25 Medium</td>
			<td>GE Healthcare</td>
			<td>17-0851-01</td>
			<td></td>
		</tr>
		<tr>
			<td>Bio-Rad ChemiDoc XRS Imaging System</td>
			<td>Bio-RAD</td>
			<td>76S/07434</td>
			<td></td>
		</tr>
		<tr>
			<td>Trypsin-EDTA(0.25%), phenol red</td>
			<td>ThermoFisher</td>
			<td>25200056</td>
			<td></td>
		</tr>
	</tbody>
</table>

targeted plasma membrane delivery of a hydrophobic cargo encapsulated in a liquid crystal nanoparticle carrier

The controlled delivery of drug/imaging agents to cells is critical for the development of therapeutics and for the study of cellular signaling processes. Recently, nanoparticles (NPs) have shown significant promise in the development of such delivery systems. Here, a liquid crystal NP (LCNP)-based delivery system has been employed for the controlled delivery of a water-insoluble dye, 3,3&#8242;-dioctadecyloxacarbocyanine perchlorate (DiO), from within the NP core to the hydrophobic region of a plasma membrane bilayer. During the synthesis of the NPs, the dye was efficiently incorporated into the hydrophobic LCNP core, as confirmed by multiple spectroscopic analyses. Conjugation of a PEGylated cholesterol derivative to the NP surface (DiO-LCNP-PEG-Chol) enabled the binding of the dye-loaded NPs to the plasma membrane in HEK 293T/17 cells. Time-resolved laser scanning confocal microscopy and F&#246;rster resonance energy transfer (FRET) imaging confirmed the passive efflux of DiO from the LCNP core and its insertion into the plasma membrane bilayer. Finally, the delivery of DiO as a LCNP-PEG-Chol attenuated the cytotoxicity of DiO; the NP form of DiO exhibited ~30-40% less toxicity compared to DiOfree delivered from bulk solution. This approach demonstrates the utility of the LCNP platform as an efficient modality for the membrane-specific delivery and modulation of hydrophobic molecular cargos.

LCNPs were prepared in which the hydrophobic core of the NP was loaded with a representative membrane-labeling probe to demonstrate the utility of the LCNP as an efficient delivery vehicle for hydrophobic cargos. For this purpose, the cargo chosen was the highly water-insoluble potentiometric membrane-labeling dye, DiO. DiO-loaded LCNPs (DiO-LCNPs) were synthesized using a two-phase mini-emulsion technique with the chemical components DACTP11, AC10COONa, and DiO, as shown in Figure 1<sup...

Watch this Scientific Journal Video about Targeted Plasma Membrane Delivery of a Hydrophobic Cargo Encapsulated in a Liquid Crystal Nanoparticle Carrier at JoVE.com

Targeted Plasma Membrane Delivery of a Hydrophobic Cargo Encapsulated in a Liquid Crystal Nanoparticle Carrier

A liquid crystal nanoparticle (LCNP) nanocarrier is exploited as a vehicle for the controlled delivery of a hydrophobic cargo to the plasma membrane of living cells.

The controlled delivery of drug/imaging agents to cells is critical for the development of therapeutics and for the study of cellular signaling processes. ...

The overall goal of this experimental procedure is to use a liquid crystal based nanoparticle as a delivery platform for the controlled delivery of a hydrophobic dicargo to the lipophilic portion of the plasma membrane of living mammalian cells. This method can help answer key questions in the drug delivery field, such as how to efficiently enable the delivery and cellular uptake of poorly water soluble hydrophobic cargos. The main advantage of this technique is that it allows more specific delivery of membrane targeted hydrophobic cargos, to the plasma membrane, coupled with their reduced cytotoxicity.Demonstrating the procedure will be Dr.Okhil Nag, a postdoc from my laboratory. Begin this procedure with preparation of DiO liquid crystal nanoparticle as described in the text protocol. Then, add 20 microliters of freshly prepared working solution of NHSS/EDC to 1.0 millileters of the DiO liquid crystal nanoparticle in HEPES buffer.And stir for five minutes. Next, add 20 microleters of a stock solution of cholesterol PEG amine to this mixture and stir for two hours. After two hours, briefly centrifuge the reaction mixture at maximum speed for 30 seconds using a tabletop mini centrifuge.Then pass the supernatant through a PD 10 size exclusion chromatography column equilibrated with Dulbecco's phosphate buffered saline. To confirm the successful covalent conjugation of PEG cholesterol to the DiO liquid crystal nanoparticle surface by gel electrophoresis, prepare an agarose gel as described in the text protocol. Once the gel has solidified, add enough TBE running buffer to submerge the gel in the chamber.Then, add 35 microleters of DiO liquid crystal nanoparticle sample to the wells of the gel and run for 20 minutes at a voltage of 110 volts. Image the gel using a gel imaging system with an excitation filter at 488 nanometers and emission filters of 500 to 550 nanometers. Prepare 35 millimeter diameter tissue culture dishes fitted with 14 millimeter number one cover glass inserts by coating them with bovine fibronectin in DPBS for two hours at 37 degrees Celsius.After two hours, remove the fibronectin coating solution from the culture dish. Harvest HEK 293 T17 cells from the T25 flask by first washing the cell monolayer with three milliliters of DPBS, and then adding two milliliters of trypsin EDTA. Incubate the flask at 37 degrees Celsius for approximately three minutes.Once cells are detached from the flask, neutralize the trypsin by adding four milliliters of complete medium to the flask. Determine the cell concentration in the suspension by counting them in a cell counter. Then adjust the cell concentration to approximately 80, 000 cells per milliliter with growth medium.Add three milliliters of the cell suspension to the dish, and culture in the incubator overnight. The next day, the cells should be at approximately 70 percent confluency and ready for use. Adequate cell density is critical for robust and efficient labeling of a high percentage of cells.Prepare one milliliter solutions of DiO, DiO liquid crystal nanoparticle, and DiO liquid crystal nanoparticle PEG cholesterol, in delivery medium by diluting the corresponding stock solutions. Remove the growth medium from the culture dishes using a serological pipette, and wash the cell monolayers two times with HEPES DMEM. Perform the washes by using a pipette to gently add HEPES DMEM to the edge of the dishes, and then removing it.Add 0.2 milliliters of the prepared DiO free or DiO liquid crystal nanoparticle delivery solutions to the center of the culture dishes. Then return the dishes to the incubator for an appropriate period of time. Longer incubation times lead to nonspecific cellular labeling of non membraneous areas.After the incubation period, remove the delivery solutions using a serological pipette. Wash the cell monolayers two times with DPBS using two milliliters for each wash. Fix the cell monolayers using four percent paraformaldehyde for 15 minutes at room temperature.Remove the paraformaldehyde solution using a pipette and gently wash the cells one time with two milliliters of DPBS. Now the fixed cells are ready to be imaged for the presence of a membraneous fluorescent signal, using confocal laser scanning microscopy. On a microscope stage equipped with a heated incubation chamber, image the live cell sample using a confocal microscope to assess membrane labeling.If the imaging is not performed immediately, replace the medium with DPBS containing 0.05 percent sodium azide and store the dishes at four degrees Celsius. In this method, cells are colabeled with DiO as a FRET donor, and DiI as a FRET acceptor. Label the sells sequentially with DiO liquid crystal nanoparticle PEG cholesterol, and DiI free as before.After staining, wash the cells one time with two millileters of DPBS using a serological pipette and replace with two milliliters of the live cell imaging solution. On a microscope stage equipped with a heated incubation chamber, image the live cell sample using a confocal microscope with a FRET imaging. Configure the experiment for 30 minute intervals over a four hour period by exciting the DiO donor at 488 nanometers, and collecting full emission spectra of both the DiO donor and the DiI acceptor from 490 to 700 nanometers, with a 32 channel spectral detector.Then, determine the time resolved emission intensity of both the DiO donor and the DiI acceptor from cells stained with DiO liquid crystal nanoparticle PEG cholesterol, and DiI. Finally, calculate the time resolved acceptor donor FRET ratio for the images as described in the text protocol. Free DiO accumulates nonspecifically in the cell interior, rather than the plasma membranes of the cells which were counterstained with a dilabeled membrane phospholipid.This can be visualized with the merged images. Conversely, the DiO liquid crystal nanoparticle PEG cholesterol specifically labels just the plasma membrane of the cell, as visualized by colocalization with the dilabeled membrane phospholipid. FRET confirms diopartitioning from the liquid crystal nanoparticle into the membrane lipid bilayer through an observed increase in energy transfer from the DiO donor to the DiI acceptor.FRET between DiO and DiI, as well as DiO and DiI emission changes, confirm increased FRET from DiO to DiI as a function of time. The DiO liquid crystal nanoparticle PEG cholesterol nanoparticles exhibit minimal cytotoxicity at 90 percent viability, as compared to significant toxicity for free DiO at approximately 50 percent viability. After watching this video, you should have a good understanding of how to synthesize cargo loaded liquid crystal nanoparticles, biofunctionalize them for cellular targeting, and image the cargo loaded cells for successful cellular delivery.Generally, individuals new to this method will struggle because the specific delivery of DiO from aqueous solution to the plasma membrane is a significant challenge. We first had the idea for this method after we used the liquid crystal nanoparticle platform for the cellular delivery of the anticancer drug doxorubicin, and saw its ability to modulate the drug's cellular uptake kinetics. Following this procedure, this approach can be implemented for the cellular delivery of a wide array of hydrophobic cargos that pose a particular challenge with respect of their delivery to cells from aqueous media.This approach can be utilized to achieve more efficient delivery of membrane targeted drugs and bioactive molecules, such as voltage sensitive dyes for brain imaging, or photodynamic drugs for photonic assisted drug therapy.

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JoVE Journal

Bioengineering

Contrast Ultrasound Targeted Treatment of Gliomas in Mice via Drug-Bearing Nanoparticle Delivery and Microvascular Ablation

We are developing minimally-invasive contrast agent microbubble based therapeutic approaches in which the permeabilization and/or ablation of the microvasculature are controlled by varying ultrasound pulsing parameters.  Specifically, we are testing whether such approaches may be used to treat malignant brain tumors through drug delivery and microvascular ablation.  Preliminary studies have been performed to determine whether targeted drug-bearing nanoparticle delivery can be facilitated by the ultrasound mediated destruction of "composite" delivery agents comprised of 100nm poly(lactide-co-glycolide) (PLAGA) nanoparticles that are adhered to albumin shelled microbubbles. We denote these agents as microbubble-nanoparticle composite agents (MNCAs). When targeted to subcutaneous C6 gliomas with ultrasound, we observed an immediate 4.6-fold increase in nanoparticle delivery in MNCA treated tumors over tumors treated with microbubbles co-administered with nanoparticles and a 8.5 fold increase over non-treated tumors. Furthermore, in many cancer applications, we believe it may be desirable to perform targeted drug delivery in conjunction with ablation of the tumor microcirculation, which will lead to tumor hypoxia and apoptosis. To this end, we have tested the efficacy of non-theramal cavitation-induced microvascular ablation, showing that this approach elicits tumor perfusion reduction, apoptosis, significant growth inhibition, and necrosis. Taken together, these results indicate that our ultrasound-targeted approach has the potential to increase therapeutic efficiency by creating tumor necrosis through microvascular ablation and/or simultaneously enhancing the drug payload in gliomas.

Insonation of microbubbles is a promising strategy for tumor ablation at reduced time-averaged acoustic powers, as well as for the targeted delivery of therapeutics. The purpose of the present study is to develop low duty cycle ultrasound pulsing strategies and nanocarriers to maximize non-thermal microvascular ablation and payload delivery to subcutaneous C6 gliomas.

We are developing minimally-invasive contrast agent microbubble based therapeutic approaches in which the permeabilization and/or ablation of the ...

Utilization of Plasmonic and Photonic Crystal Nanostructures for Enhanced Micro- and Nanoparticle Manipulation

A method to manipulate the position and orientation of submicron particles nondestructively would be an incredibly useful tool for basic biological research. Perhaps the most widely used physical force to achieve noninvasive manipulation of small particles has been dielectrophoresis(DEP).1 However, DEP on its own lacks the versatility and precision that are desired when manipulating cells since it is traditionally done with stationary electrodes. Optical tweezers, which utilize a three dimensional electromagnetic field gradient to exert forces on small particles, achieve this desired versatility and precision.2 However, a major drawback of this approach is the high radiation intensity required to achieve the necessary force to trap a particle which can damage biological samples.3 A solution that allows trapping and sorting with lower optical intensities are optoelectronic tweezers (OET) but OET's have limitations with fine manipulation of small particles; being DEP-based technology also puts constraint on the property of the solution.4,5
This video article will describe two methods that decrease the intensity of the radiation needed for optical manipulation of living cells and also describe a method for orientation control. The first method is plasmonic tweezers which use a random gold nanoparticle (AuNP) array as a substrate for the sample as shown in Figure 1. The AuNP array converts the incident photons into localized surface plasmons (LSP) which consist of resonant dipole moments that radiate and generate a patterned radiation field with a large gradient in the cell solution. Initial work on surface plasmon enhanced trapping by Righini et al and our own modeling have shown the fields generated by the plasmonic substrate reduce the initial intensity required by enhancing the gradient field that traps the particle.6,7,8 The plasmonic approach allows for fine orientation control of ellipsoidal particles and cells with low optical intensities because of more efficient optical energy conversion into mechanical energy and a dipole-dependent radiation field. These fields are shown in figure 2 and the low trapping intensities are detailed in figures 4 and 5. The main problems with plasmonic tweezers are that the LSP's generate a considerable amount of heat and the trapping is only two dimensional. This heat generates convective flows and thermophoresis which can be powerful enough to expel submicron particles from the trap.9,10 The second approach that we will describe is utilizing periodic dielectric nanostructures to scatter incident light very efficiently into diffraction modes, as shown in figure 6.11 Ideally, one would make this structure out of a dielectric material to avoid the same heating problems experienced with the plasmonic tweezers but in our approach an aluminum-coated diffraction grating is used as a one-dimensional periodic dielectric nanostructure. Although it is not a semiconductor, it did not experience significant heating and effectively trapped small particles with low trapping intensities, as shown in figure 7. Alignment of particles with the grating substrate conceptually validates the proposition that a 2-D photonic crystal could allow precise rotation of non-spherical micron sized particles.10 The efficiencies of these optical traps are increased due to the enhanced fields produced by the nanostructures described in this paper.

Plasmonic tweezers and photonic crystal nanostructures are shown to produce useful enhancements in the efficiency and orientation control of optically trapping micro- and nano-particles.

A method to manipulate the position and orientation of submicron particles nondestructively would be an incredibly useful tool for basic biological ...

Cellular Lipid Extraction for Targeted Stable Isotope Dilution Liquid Chromatography-Mass Spectrometry Analysis

The metabolism of fatty acids, such as arachidonic acid (AA) and linoleic acid (LA), results in the formation of oxidized bioactive lipids, including numerous stereoisomers1,2. These metabolites can be formed from free or esterified fatty acids. Many of these oxidized metabolites have biological activity and have been implicated in various diseases including cardiovascular and neurodegenerative diseases, asthma, and cancer3-7. Oxidized bioactive lipids can be formed enzymatically or by reactive oxygen species (ROS). Enzymes that metabolize fatty acids include cyclooxygenase (COX), lipoxygenase (LO), and cytochromes P450 (CYPs)1,8. Enzymatic metabolism results in enantioselective formation whereas ROS oxidation results in the racemic formation of products.
While this protocol focuses primarily on the analysis of AA- and some LA-derived bioactive metabolites; it could be easily applied to metabolites of other fatty acids. Bioactive lipids are extracted from cell lysate or media using liquid-liquid (l-l) extraction. At the beginning of the l-l extraction process, stable isotope internal standards are added to account for errors during sample preparation. Stable isotope dilution (SID) also accounts for any differences, such as ion suppression, that metabolites may experience during the mass spectrometry (MS) analysis9. After the extraction, derivatization with an electron capture (EC) reagent, pentafluorylbenzyl bromide (PFB) is employed to increase detection sensitivity10,11. Multiple reaction monitoring (MRM) is used to increase the selectivity of the MS analysis. Before MS analysis, lipids are separated using chiral normal phase high performance liquid chromatography (HPLC). The HPLC conditions are optimized to separate the enantiomers and various stereoisomers of the monitored lipids12. This specific LC-MS method monitors prostaglandins (PGs), isoprostanes (isoPs), hydroxyeicosatetraenoic acids (HETEs), hydroxyoctadecadienoic acids (HODEs), oxoeicosatetraenoic acids (oxoETEs) and oxooctadecadienoic acids (oxoODEs); however, the HPLC and MS parameters can be optimized to include any fatty acid metabolites13.
Most of the currently available bioanalytical methods do not take into account the separate quantification of enantiomers. This is extremely important when trying to deduce whether or not the metabolites were formed enzymatically or by ROS. Additionally, the ratios of the enantiomers may provide evidence for a specific enzymatic pathway of formation. The use of SID allows for accurate quantification of metabolites and accounts for any sample loss during preparation as well as the differences experienced during ionization. Using the PFB electron capture reagent increases the sensitivity of detection by two orders of magnitude over conventional APCI methods. Overall, this method, SID-LC-EC-atmospheric pressure chemical ionization APCI-MRM/MS, is one of the most sensitive, selective, and accurate methods of quantification for bioactive lipids.

This protocol will demonstrate the extraction and analysis of free and esterified bioactive fatty acids from cells. Fatty acids are accurately quantified using stable isotope dilution, chiral liquid chromatography, electron capture atmospheric chemical ionization multiple reaction monitoring mass spectrometry (SID-LC-ECAPCI-MRM/MS).

The metabolism of fatty acids, such as arachidonic acid (AA) and linoleic acid (LA), results in the formation of oxidized bioactive lipids, including ...

Hydrogel Nanoparticle Harvesting of Plasma or Urine for Detecting Low Abundance Proteins

Novel biomarker discovery plays a crucial role in providing more sensitive and specific disease detection. Unfortunately many low-abundance biomarkers that exist in biological fluids cannot be easily detected with mass spectrometry or immunoassays because they are present in very low concentration, are labile, and are often masked by high-abundance proteins such as albumin or immunoglobulin. Bait containing poly(N-isopropylacrylamide) (NIPAm) based nanoparticles are able to overcome these physiological barriers. In one step they are able to capture, concentrate and preserve biomarkers from body fluids. Low-molecular weight analytes enter the core of the nanoparticle and are captured by different organic chemical dyes, which act as high affinity protein baits. The nanoparticles are able to concentrate the proteins of interest by several orders of magnitude. This concentration factor is sufficient to increase the protein level such that the proteins are within the detection limit of current mass spectrometers, western blotting, and immunoassays. Nanoparticles can be incubated with a plethora of biological fluids and they are able to greatly enrich the concentration of low-molecular weight proteins and peptides while excluding albumin and other high-molecular weight proteins. Our data show that a 10,000 fold amplification in the concentration of a particular analyte can be achieved, enabling mass spectrometry and immunoassays to detect previously undetectable biomarkers.

Several pathological biomarkers cannot be easily detected by current techniques because of their low concentration in biological fluids, the presence of degrading enzymes, and large amounts of high molecular weight proteins. Chemically functionalized hydrogel nanoparticles can harvest, preserve and concentrate low abundance proteins enabling the detection of previously undetectable biomarkers.

Novel biomarker discovery plays a crucial role in providing more sensitive and specific disease detection. Unfortunately many low-abundance biomarkers ...

Fluorescence-quenching of a Liposomal-encapsulated Near-infrared Fluorophore as a Tool for In Vivo Optical Imaging

Optical imaging offers a wide range of diagnostic modalities and has attracted a lot of interest as a tool for biomedical imaging. Despite the enormous number of imaging techniques currently available and the progress in instrumentation, there is still a need for highly sensitive probes that are suitable for in vivo imaging. One typical problem of available preclinical fluorescent probes is their rapid clearance in vivo, which reduces their imaging sensitivity. To circumvent rapid clearance, increase number of dye molecules at the target site, and thereby reduce background autofluorescence, encapsulation of the near-infrared fluorescent dye, DY-676-COOH in liposomes and verification of its potential for in vivo imaging of inflammation was done. DY-676 is known for its ability to self-quench at high concentrations. We first determined the concentration suitable for self-quenching, and then encapsulated this quenching concentration into the aqueous interior of PEGylated liposomes. To substantiate the quenching and activation potential of the liposomes we use a harsh freezing method which leads to damage of liposomal membranes without affecting the encapsulated dye. The liposomes characterized by a high level of fluorescence quenching were termed Lip-Q. We show by experiments with different cell lines that uptake of Lip-Q is predominantly by phagocytosis which in turn enabled the characterization of its potential as a tool for in vivo imaging of inflammation in mice models. Furthermore, we use a zymosan-induced edema model in mice to substantiate the potential of Lip-Q in optical imaging of inflammation in vivo. Considering possible uptake due to inflammation-induced enhanced permeability and retention (EPR) effect, an always-on liposome formulation with low, non-quenched concentration of DY-676-COOH (termed Lip-dQ) and the free DY-676-COOH were compared with Lip-Q in animal trials.

Fluorescence-quenching of a Liposomal-encapsulated Near-infrared Fluorophore as a Tool for In Vivo Optical Imaging

The use of fluorophores for in vivo imaging can be greatly limited by opsonization, rapid clearance, low detection sensitivity and cytotoxic effects on the host. Encapsulation of fluorophores in liposomes by film hydration and extrusion leads to fluorescence quenching and protection which enables in vivo imaging with high detection sensitivity.

Optical imaging offers a wide range of diagnostic modalities and has attracted a lot of interest as a tool for biomedical imaging. Despite the enormous ...

Alternating Magnetic Field-Responsive Hybrid Gelatin Microgels for Controlled Drug Release

Magnetically-responsive nano/micro-engineered biomaterials that enable a tightly controlled, on-demand drug delivery have been developed as new types of smart soft devices for biomedical applications. Although a number of magnetically-responsive drug delivery systems have demonstrated efficacies through either in vitro proof of concept studies or in vivo preclinical applications, their use in clinical settings is still limited by their insufficient biocompatibility or biodegradability. Additionally, many of the existing platforms rely on sophisticated techniques for their fabrications. We recently demonstrated the fabrication of biodegradable, gelatin-based thermo-responsive microgel by physically entrapping poly(N-isopropylacrylamide-co-acrylamide) chains as a minor component within a three-dimensional gelatin network. In this study, we present a facile method to fabricate a biodegradable drug release platform that enables a magneto-thermally triggered drug release. This was achieved by incorporating superparamagnetic iron oxide nanoparticles and thermo-responsive polymers within gelatin-based colloidal microgels, in conjunction with an alternating magnetic field application system.

We present a facile method to fabricate a biodegradable gelatin-based drug release platform that is magneto-thermally responsive. This was achieved by incorporating superparamagnetic iron oxide nanoparticles and poly(N-isopropylacrylamide-co-acrylamide) within a spherical gelatin micro-network crosslinked by genipin, in conjunction with an alternating magnetic field application system.

Magnetically-responsive nano/micro-engineered biomaterials that enable a tightly controlled, on-demand drug delivery have been developed as new types of ...

Preparation of Monodomain Liquid Crystal Elastomers and Liquid Crystal Elastomer Nanocomposites

LCEs are shape-responsive materials with fully reversible shape change and potential applications in medicine, tissue engineering, artificial muscles, and as soft robots. Here, we demonstrate the preparation of shape-responsive liquid crystal elastomers (LCEs) and LCE nanocomposites along with characterization of their shape-responsiveness, mechanical properties, and microstructure. Two types of LCEs &#8212; polysiloxane-based and epoxy-based &#8212; are synthesized, aligned, and characterized. Polysiloxane-based LCEs are prepared through two crosslinking steps, the second under an applied load, resulting in monodomain LCEs. Polysiloxane LCE nanocomposites are prepared through the addition of conductive carbon black nanoparticles, both throughout the bulk of the LCE and to the LCE surface. Epoxy-based LCEs are prepared through a reversible esterification reaction. Epoxy-based LCEs are aligned through the application of a uniaxial load at elevated (160 &#176;C) temperatures. Aligned LCEs and LCE nanocomposites are characterized with respect to reversible strain, mechanical stiffness, and liquid crystal ordering using a combination of imaging, two-dimensional X-ray diffraction measurements, differential scanning calorimetry, and dynamic mechanical analysis. LCEs and LCE nanocomposites can be stimulated with heat and/or electrical potential to controllably generate strains in cell culture media, and we demonstrate the application of LCEs as shape-responsive substrates for cell culture using a custom-made apparatus.

We demonstrate the preparation of siloxane-based and epoxy-based liquid crystal elastomers (LCEs) and LCE nanocomposites. The LCEs are characterized with respect to reversible strain, liquid crystal ordering, and stiffness. As a potential application, we demonstrate their use as shape-responsive substrates in a custom device for active cell culture.

LCEs are shape-responsive materials with fully reversible shape change and potential applications in medicine, tissue engineering, artificial muscles, and ...

Synthesis of Biocompatible Liquid Crystal Elastomer Foams as Cell Scaffolds for 3D Spatial Cell Cultures

Here, we present a step-by-step preparation of a 3D, biodegradable, foam-like cell scaffold. These scaffolds were prepared by cross-linking star block co-polymers featuring cholesterol units as side-chain pendant groups, resulting in smectic-A (SmA) liquid crystal elastomers (LCEs). Foam-like scaffolds, prepared using metal templates, feature interconnected microchannels, making them suitable as 3D cell culture scaffolds. The combined properties of the regular structure of the metal foam and of the elastomer result in a 3D cell scaffold that promotes not only higher cell proliferation compared to conventional porous templated films, but also better management of mass transport (i.e., nutrients, gases, waste, etc.). The nature of the metal template allows for the easy manipulation of foam shapes (i.e., rolls or films) and for the preparation of scaffolds of different pore sizes for different cell studies while preserving the interconnected porous nature of the template. The etching process does not affect the chemistry of the elastomers, preserving their biocompatible and biodegradable nature. We show that these smectic LCEs, when grown for extensive time periods, enable the study of clinically relevant and complex tissue constructs while promoting the growth and proliferation of cells.

This study presents a methodology to prepare 3D, biodegradable, foam-like cell scaffolds based on biocompatible side-chain liquid crystal elastomers (LCEs). Confocal microscopy experiments show that foam-like LCEs allow for cell attachment, proliferation, and the spontaneous alignment of C2C12s myoblasts.

Here, we present a step-by-step preparation of a 3D, biodegradable, foam-like cell scaffold. These scaffolds were prepared by cross-linking star block ...

Real-time Visualization and Analysis of Chondrocyte Injury Due to Mechanical Loading in Fully Intact Murine Cartilage Explants

Homeostasis of articular cartilage depends on the viability of resident cells (chondrocytes). Unfortunately, mechanical trauma can induce widespread chondrocyte death, potentially leading to irreversible breakdown of the joint and the onset of osteoarthritis. Additionally, maintenance of chondrocyte viability is important in osteochondral graft procedures for optimal surgical outcomes. We present a method to assess the spatial extent of cell injury/death on the articular surface of intact murine synovial joints after application of controlled mechanical loads or impacts. This method can be used in comparative studies to investigate the effects of different mechanical loading regimens, different environmental conditions or genetic manipulations, as well as different stages of cartilage degeneration on short- and/or long-term vulnerability of in situ articular chondrocytes. The goal of the protocol introduced in the manuscript is to assess the spatial extent of cell injury/death on the articular surface of murine synovial joints. Importantly, this method enables testing on fully intact cartilage without compromising native boundary conditions. Moreover, it allows for real-time visualization of vitally stained articular chondrocytes and single image-based analysis of cell injury induced by application of controlled static and impact loading regimens. Our representative results demonstrate that in healthy cartilage explants, the spatial extent of cell injury depends sensitively on load magnitude and impact intensity. Our method can be easily adapted to investigate the effects of different mechanical loading regimens, different environmental conditions or different genetic manipulations on the mechanical vulnerability of in situ articular chondrocytes.

We present a method to assess the spatial extent of cell injury/death on the articular surface of intact murine joints after application of controlled mechanical loads or impacts. This method can be used to investigate how osteoarthritis, genetic factors and/or different loading regimens affect the vulnerability of in situ chondrocytes.

Homeostasis of articular cartilage depends on the viability of resident cells (chondrocytes). Unfortunately, mechanical trauma can induce widespread ...

In Vesiculo Synthesis of Peptide Membrane Precursors for Autonomous Vesicle Growth

Compartmentalization of biochemical reactions is a central aspect of synthetic cells. For this purpose, peptide-based reaction compartments serve as an attractive alternative to liposomes or fatty acid-based vesicles. Externally or within the vesicles, peptides can be easily expressed and simplify the synthesis of membrane precursors. Provided here is a protocol for the creation of vesicles with diameters of ~200 nm based on the amphiphilic elastin-like polypeptides (ELP) utilizing dehydration-rehydration from glass beads. Also presented are protocols for bacterial ELP expression and purification via inverse temperature cycling, as well as their covalent functionalization with fluorescent dyes. Furthermore, this report describes a protocol to enable the transcription of RNA aptamer dBroccoli inside ELP vesicles as a less complex example for a biochemical reaction. Finally, a protocol is provided, which allows in vesiculo expression of fluorescent proteins and the membrane peptide, whereas synthesis of the latter results in vesicle growth.

Presented here are protocols for the creation of peptide-based small unilamellar vesicles capable of growth. To facilitate in vesiculo production of the membrane peptide, these vesicles are equipped with a transcription-translation system and the peptide-encoding plasmid.

Compartmentalization of biochemical reactions is a central aspect of synthetic cells. For this purpose, peptide-based reaction compartments serve as an ...