Name: a tripeptide-stabilized nanoemulsion of oleic acid
Uploaded: 2019-02-27T13:00:00
Description: Watch this Scientific Journal Video about A Tripeptide-Stabilized Nanoemulsion of Oleic Acid at JoVE.com

We gratefully acknowledge financial support from the National Cancer Institute, grant SC2CA206194. No competing financial interests are declared.

1. Synthesis of the Oleic Acids&#8211;Platinum(II) Conjugate
<ol>
	<li>Activation of cisplatin
	<ol>
		<li>Suspend 50 mg (0.167 mmol) of cisplatin in 4 mL of water (e.g., nanopure) at 60 &#176;C.</li>
		<li>Add dropwise 55.2 mg (0.325 mmol) of AgNO3 in 0.5 mL of water to the solution of cisplatin and stir the reaction for at least 2 h at 60 &#176;C. The white precipitate of AgCl will form indicating the progress of the reaction.</li>
		<li>To determine if the activation reaction is completed, perform the tes...

Critical steps in the nanoemulsion synthesis include adjusting the molar ratio of the substrates, maintaining temperature and flow rate control during oleic acids&#8211;Pt(II) addition, providing sufficient time for self-assembly, and purifying the product using a centrifugal concentrator column. These parameters influence the size and morphology of the KYF-Pt-NE; thus, it is particularly important to maintain the proper molar ratio and adjust the synthetic conditions correctly.
The ratio of t...

In recent years, there has been a growing interest in the engineering of nanoparticles for such biomedical applications as drug delivery and bioimaging1,2,3,4. The multifunctionality of nanoparticle-based systems often necessitates incorporating multiple components within one formulation. The building blocks that are based on lipids or polymers often differ in terms of their physicochemical properties as well as their biocompatibility and biodegradability, which ultimately might affect the function of the nanostructure1,5,6. Biologically derived materials, such as proteins and peptides, have long been recognized as promising components of multifunctional nanostructures due to their sequence flexibility7,8. Peptides self-assemble into highly ordered supramolecular architectures forming helical ribbons9,10, fibrous scaffolds11,12, and many more, thus paving the way to building biomolecule-based hybrid nanostructures using a bottom-up approach13.
Peptides have been explored for applications in medicine and biotechnology, especially for anticancer therapy14 and cardiovascular diseases15 as well as for antibiotic development16,17, metabolic disorders18, and infections19. There are over a hundred of small-peptide therapeutics undergoing clinical trials20. Peptides are easy to modify and fast to synthesize at low cost. In addition, they are biodegradable, which greatly facilitates their biological and pharmaceutical applications21,22. The use of peptides as structural components includes the engineering of responsive, peptide-based nanoparticles and hydrogel depots for controlled release23,24,25,26,27, peptide-based biosensors28,29,30,31, or bio-electronic devices32,33,34. Importantly, even short peptides with two or three amino-acid residues that include phenylalanine were found to guide the self-assembly processes35,36,37 and create stabilized emulsions38.
Platinum-based drugs, owing to their high efficacy, are used in many cancer treatment regimens, both alone and in combination with other agents39,40. Platinum compounds induce DNA damage by forming monoadducts and intrastrand or interstrand cross-links. The Pt-DNA lesions are recognized by the cellular machinery and, if not repaired, lead to cellular apoptosis. The most important mechanism, by which Pt(II) contributes to cancer cell death, is the inhibition of DNA transcription41,42. However, the benefits of platinum therapy are diminished by systemic toxicity of Pt(II) that triggers severe side effects. This leads to lower clinical dosing of Pt(II)43, which often results in sub-therapeutic concentrations of platinum reaching the DNA. As a consequence, the DNA repair that follows contributes to cancer cell survival and acquiring Pt(II) resistance. The platinum chemo-resistance is a major problem in anticancer therapy and the main cause of treatment failure44,45.
We have developed a stable nanosystem that encapsulates the Pt(II) agent in order to provide a shielding effect in systemic circulation and to diminish the Pt(II)-induced side effects. The system is based on an oleic acids-Pt(II) core stabilized with a KYF tripeptide to form a nanoemulsion (KYF-Pt-NE)46. The building blocks of KYF-Pt-NE, the amino acids of the tripeptide as well as the oleic acid, have the Generally Recognized As Safe (GRAS) status with Food and Drug Administration (FDA). The KYF-Pt-NE is prepared by using a nanoprecipitation method47. In short, the oleic acids-Pt(II) conjugate is dissolved in an organic solvent and then added dropwise to an aqueous KYF solution (Figure 1) at 37 &#176;C. The solution is stirred for several hours to allow self-assembly of the KYF-Pt-NE. The nanoemulsion is concentrated in 10 kDa centrifugal concentrators and washed three times with water. The chemical modification of the KYF with a fluorophore allows the synthesis of fluorescent FITC-KYF-Pt-NE suitable for biomedical imaging.

<table>
	<tbody>
		<tr>
			<td>2-(1H-benzotriazole-1-yl)-1,1,3,3-tetramethyluronium 
			tetrafluoroborate (TBTU)</td>
			<td>ANASPEC INC.:</td>
			<td>AS-20376</td>
			<td>SPPS</td>
		</tr>
		<tr>
			<td>4-well chamber confocal dish</td>
			<td>Lab-Tek II, Thermo Fisher Scientific</td>
			<td>154526</td>
			<td>For imaging</td>
		</tr>
		<tr>
			<td>6-bromohexanoic acid</td>
			<td>Chem-Impex INT&#8217;L INC.</td>
			<td>24477</td>
			<td>Click modification for peptide</td>
		</tr>
		<tr>
			<td>A2780</td>
			<td>Generously doanted by professor John Martignetti from The Mount Sinai Hospital</td>
			<td></td>
			<td>Ovarian cancer cell line</td>
		</tr>
		<tr>
			<td>Barnstead Nanopure</td>
			<td>Thermo Fisher</td>
			<td>D11901</td>
			<td>water filtration system</td>
		</tr>
		<tr>
			<td>BUCHI rotavapor R-3</td>
			<td>Buchi</td>
			<td>Z568090</td>
			<td>For solvent removal and sample drying</td>
		</tr>
		<tr>
			<td>Centrifuge 5810 R</td>
			<td>eppendorf</td>
			<td>5811F</td>
			<td>For platinum complex separation</td>
		</tr>
		<tr>
			<td>Cis-dichlorodiamineplatinum (II) 99%</td>
			<td>Acros Organics</td>
			<td>19376-0050</td>
			<td>in vitro tests</td>
		</tr>
		<tr>
			<td>CP70</td>
			<td>Generously doanted by professor John Martignetti from The Mount Sinai Hospital</td>
			<td></td>
			<td>Ovarian cancer cell line</td>
		</tr>
		<tr>
			<td>Digital water bath</td>
			<td>VWR</td>
			<td>97025-134</td>
			<td>For warming up media for cell culture</td>
		</tr>
		<tr>
			<td>Dynamic Light Scattering (DLS)</td>
			<td>Brookhaven Instrument Corporation</td>
			<td></td>
			<td>For nanoparticle size measurments</td>
		</tr>
		<tr>
			<td>ES-2</td>
			<td>ATCC</td>
			<td>CRL-1978</td>
			<td>ovarian cancer cell line</td>
		</tr>
		<tr>
			<td>Fmoc-L-Lys(Boc)-OH 99.79%</td>
			<td>Chem-Impex INT&#8217;L INC.</td>
			<td>00493</td>
			<td>SPPS</td>
		</tr>
		<tr>
			<td>Fmoc-L-Phe 4-alkoxybenzyl alcohol resin (0.382 meq/g),</td>
			<td>Chem-Impex INT&#8217;L INC.</td>
			<td>01914</td>
			<td>SPPS</td>
		</tr>
		<tr>
			<td>Fmoc-LTyr(tBu)-OH 98%</td>
			<td>Alfa Aesar</td>
			<td>H59730</td>
			<td>SPPS</td>
		</tr>
		<tr>
			<td>HERACELL 150i CO2 incubator</td>
			<td>Thermo Scientific Fisher</td>
			<td></td>
			<td>incubator</td>
		</tr>
		<tr>
			<td>High pressure syringe pump</td>
			<td>New Era</td>
			<td>1010-US</td>
			<td>For platinum complex addition in nanoparticle synthesis</td>
		</tr>
		<tr>
			<td>Hotplate/stirrer</td>
			<td>VWR</td>
			<td>12365-382</td>
			<td>For sample stirring and heating</td>
		</tr>
		<tr>
			<td>LAMP-1 Antibody(cojugated with Alexa Fluor 647)</td>
			<td>Santa Cruz Biotechnology</td>
			<td>sc-18821 AF647</td>
			<td>For imaging</td>
		</tr>
		<tr>
			<td>N,N-diisopropylethylamine (DIPEA)</td>
			<td>Oakwood Chemical</td>
			<td>005027</td>
			<td>SPPS</td>
		</tr>
		<tr>
			<td>Ninhydrin 99%</td>
			<td>Alfa Aesar</td>
			<td>A10409</td>
			<td>Kaiser test</td>
		</tr>
		<tr>
			<td>Oleic acid</td>
			<td>Chem-Impex INT&#8217;L INC.</td>
			<td>01421</td>
			<td>For platinum complex synthesis</td>
		</tr>
		<tr>
			<td>OV90</td>
			<td>ATCC</td>
			<td>CRL-11732</td>
			<td>Ovarian cancer cell line</td>
		</tr>
		<tr>
			<td>PBS</td>
			<td>Corning</td>
			<td>21-031-CV</td>
			<td>For cell wash</td>
		</tr>
		<tr>
			<td>Permount mounting medium</td>
			<td>Fisher Chemical</td>
			<td>SP15-100</td>
			<td>For imaging</td>
		</tr>
		<tr>
			<td>Phenol</td>
			<td>Fisher Chemical</td>
			<td>A92500</td>
			<td>Kaiser test</td>
		</tr>
		<tr>
			<td>Phosphotungstic acid</td>
			<td>Fisher Chemical</td>
			<td>A248-25</td>
			<td>negative stain for TEM</td>
		</tr>
		<tr>
			<td>Piperidine 99%</td>
			<td>BTC</td>
			<td>219260-2.5L</td>
			<td>SPPS</td>
		</tr>
		<tr>
			<td>Platinum AAS standard soultion</td>
			<td>Alfa Aesar</td>
			<td>88086</td>
			<td>1000ug/ml for calibration curve</td>
		</tr>
		<tr>
			<td>Propargyl bromide 97%</td>
			<td>Alfa Aesar</td>
			<td>L10595</td>
			<td>For alkyne modification of fluoresceine</td>
		</tr>
		<tr>
			<td>Scientific biological cabinet</td>
			<td>Thermo Scientific Fisher</td>
			<td>1385</td>
			<td>Bio-hood for cell culture</td>
		</tr>
		<tr>
			<td>Self-Cleaning Vacuum System</td>
			<td>Welch</td>
			<td>2028</td>
			<td>Vacuum pump for rotavapor</td>
		</tr>
		<tr>
			<td>Silver nitrate</td>
			<td>Acros Organics</td>
			<td>19768-0250</td>
			<td>Cisplatin activation</td>
		</tr>
		<tr>
			<td>SKOV3</td>
			<td>ATCC</td>
			<td>HTB-77</td>
			<td>Ovarian cancer cell line</td>
		</tr>
		<tr>
			<td>Sodium hydroxide</td>
			<td>Fisher Scientific</td>
			<td>S313-1</td>
			<td>For platinum complex synthesis</td>
		</tr>
		<tr>
			<td>Tin (II) chloride</td>
			<td>Sigma Aldrich</td>
			<td>208256</td>
			<td>Test for Platinum presence</td>
		</tr>
		<tr>
			<td>TOV21G</td>
			<td>ATCC</td>
			<td>CRL-11730</td>
			<td>Ovarian cancer cell line</td>
		</tr>
		<tr>
			<td>Trifluoroacetic acid 99% (TFA)</td>
			<td>Alfa Aesar</td>
			<td>L06374</td>
			<td>SPPS</td>
		</tr>
		<tr>
			<td>Triisopropylsilane (TIPS)</td>
			<td>Chem-Impex INT&#8217;L INC.</td>
			<td>01966</td>
			<td>SPPS</td>
		</tr>
		<tr>
			<td>Triton-X</td>
			<td>Sigma Aldrich</td>
			<td>T8787-100ML</td>
			<td>For imaging</td>
		</tr>
		<tr>
			<td>Uranine powder 40%</td>
			<td>Fisher Scientific</td>
			<td>S25328A</td>
			<td>For alkyne modification of fluoresceine</td>
		</tr>
		<tr>
			<td>Vivaspin 20 (10000 MWCO)</td>
			<td>Sartorious</td>
			<td>VS2001</td>
			<td>For Nanoparticle wash and condensation</td>
		</tr>
		<tr>
			<td>VWR Inverted Microscope</td>
			<td>VWR</td>
			<td>89404-462</td>
			<td>For cell culture monitoring</td>
		</tr>
	</tbody>
</table>

a tripeptide-stabilized nanoemulsion of oleic acid

We describe a method to produce a nanoemulsion composed of an oleic acids-Pt(II) core and a lysine-tyrosine-phenylalanine (KYF) coating (KYF-Pt-NE). The KYF-Pt-NE encapsulates Pt(II) at 10 wt. %, has a diameter of 107 &#177; 27 nm and a negative surface charge. The KYF-Pt-NE is stable in water and in serum, and is biologically active. The conjugation of a fluorophore to KYF allows the synthesis of a fluorescent nanoemulsion that is suitable for biological imaging. The synthesis of the nanoemulsion is performed in an aqueous environment, and the KYF-Pt-NE forms via self-assembly of a short KYF peptide and an oleic acids-platinum(II) conjugate. The self-assembly process depends on the temperature of the solution, the molar ratio of the substrates, and the flow rate of the substrate addition. Crucial steps include maintaining the optimal stirring rate during the synthesis, permitting sufficient time for self-assembly, and pre-concentrating the nanoemulsion gradually in a centrifugal concentrator.

Representative TEM image of KYF-Pt-NE prepared using this protocol is shown in Figure 2A. The KYF-Pt-NEs are spherical in morphology, well dispersed, and uniform in size. The core diameter of the KYF-Pt-NEs, measured directly from three TEM images with a minimum of 200 measurements done, is 107 &#177; 27 nm. The hydrodynamic diameter of KYF-Pt-NE, analyzed using dynamic light spectroscopy (DLS), was found to be 240 nm with a polydispersity index of 0.156. The...

Watch this Scientific Journal Video about A Tripeptide-Stabilized Nanoemulsion of Oleic Acid at JoVE.com

A Tripeptide-Stabilized Nanoemulsion of Oleic Acid

This protocol describes an efficient method to synthesize a nanoemulsion of an oleic acids-platinum(II) conjugate stabilized with a lysine-tyrosine-phenylalanine (KYF) tripeptide. The nanoemulsion forms under mild synthetic conditions via self-assembly of the KYF and the conjugate.

We describe a method to produce a nanoemulsion composed of an oleic acids-Pt(II) core and a lysine-tyrosine-phenylalanine (KYF) coating (KYF-Pt-NE). The ...

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