Name: synthesis of monocyte-targeting peptide amphiphile micelles for imaging of atherosclerosis
Uploaded: 2017-11-17T14:00:00
Description: Watch this Scientific Journal Video about Synthesis of Monocyte-targeting Peptide Amphiphile Micelles for Imaging of Atherosclerosis at JoVE.com

The authors would like to acknowledge the financial support from the University of Southern California, the National Heart, Lung, and Blood Institute (NHLBI), R00HL124279, Eli and Edythe Broad Innovation Award, and the L.K. Whittier Foundation Non-Cancer Translational Research Award granted to EJC. The authors thank the Center for Electron Microscopy and Microanalysis, Center of Excellence in NanoBiophysics, Center of Excellence for Molecular Characterization, and Translational Imaging Center at the University of Southern California for assistance in instrumental setups.

NOTE: Read the MSDS for reagents and follow all chemical safety measures as required by local institution.
1. Preparation of MCP-1 PAMs
<ol>
	<li>Preparation of MCP-1 peptide
	<ol>
		<li>Weigh out 0.25 mmol of Fmoc-L-Lys(Boc)-Wang in a reaction vessel (RV). Rinse the side of the RV with 5 mL dimethylforamide (DMF) in a chemical fume hood.</li>
		<li>Load the RV onto an automated benchtop peptide synthesizer. Load pre-packaged amino acid vials, N&#39;-CYNFTINRKISVQRLASYRRITSS...

MCP-1 PAMs are a promising molecular imaging platform, consisting of a hydrophilic targeting peptide and hydrophobic tail that drives the self-assembled nature of the nanoparticle. This monocyte-targeting micelle can be prepared by simple synthesis and purification steps of the MCP-1 peptide and DSPE-PEG(2000)-MCP-1. PAMs have many beneficial characteristics for in vivo molecular imaging such as their self-assembly under mild conditions, intrinsic biodegradability, and structural and chemical diversity allowing ...

Cardiovascular diseases remain to be the leading causes of death globally with approximately 17.3 million deaths worldwide1. Cardiovascular diseases are contributed by atherosclerosis, a condition in which plaques build up in the arteries, thereby inhibiting blood and oxygen flow to the cells of the body2,3. The progression of atherosclerosis involves the thickening and hardening of arteries by an inflammatory response, irregular lipid metabolism, and plaque build-up, leading to plaque rupture and myocardial infarction4,5. Endothelial cells express cytokines and adhesion molecules, which include MCP-1 that binds to the C-C chemokine receptor (CCR2) found on the surface of monocytes6,7,8. Oxidized cholesterol converts monocytes to macrophages during the early stage of plaque formation, which amplifies the inflammatory response in the region and leads to tissue injury and the formation of unstable or vulnerable plaques9,10.
Traditionally, atherosclerosis is evaluated by assessing luminal stenosis by anatomical imaging using angiography or ultrasound11,12. However, these methods can only determine severe narrowing of the arterial wall and not the early stage of atherosclerosis, as initial plaque growth causes arterial remodeling to maintain artery size and blood flow rate12,13,14. Therefore, angiograms underrepresent atherosclerosis prevalence. Additionally, noninvasive imaging techniques such as single photon emission computed tomography, positron emission tomography, and magnetic resonance imaging have recently been used to characterize plaque morphology as they can provide initial details and characterization of plaques. However, these modalities are often limited by the lack of sensitivity, spatial resolution, or require the use of ionizing radiation, making imaging plaque progression at different stages much more challenging15,16,17. An imaging delivery system that would specifically identify plaques at different stages of atherosclerosis remains to be developed.
Nanoparticles have shown to be an emerging platform for in vivo plaque targeting and diagnostics18,19,20,21. In particular, PAMs are advantageous due to their chemical diversity and ability to accommodate a variety of moieties, compositions, sizes, shapes, and surface functionalization22. Peptide amphiphiles (PAs) consist of a hydrophilic, peptide &#34;headgroup&#34; attached to a hydrophobic tail, which are typically lipids; this amphiphilic structure confers self-assembling capabilities and allows for a multivalent display of peptides on the surface of the particle22,23,24. The peptide headgroups can affect the particle shape through folding and hydrogen bonding between peptides25. Peptides that fold through &#946;-sheet interaction have been shown to form elongated micelles, while &#945;-helical confirmation can form both spherical and elongated micelles22,23,24,25,26,27. Polyethylene glycol (PEG) linkers that shield the surface charge of the peptide can be placed between the hydrophilic peptide and the hydrophobic tail of PAMs, enhancing the availability of the nanoparticle in systemic circulation28,29,30,31. PAMs are also advantageous because they are biocompatible and have been shown to have a broad range of applications32,33. The water solubility of micelles offers an advantage over other nanoparticle-based systems such as certain polymeric nanoparticles that are not soluble in water and have to be suspended in solubilizers for injections34. Additionally, the ability to create PAMs that disassemble in response to a specific stimuli makes PAMs an attractive candidate for controlled intracellular drug delivery35.
By binding to the CCR2 receptor and accumulating in the aortic arch, PAMs were previously developed for monocyte targeting to monitor different stages of atherosclerotic lesions in the aorta9. In ApoE-/- mice, monocyte accumulation increases proportionally to plaque progression36. Furthermore, it was found that patients with rupture-prone, late-stage plaques contain higher amounts of monocytes37. Therefore, the modification of PAMs to incorporate MCP-1 is useful because it allows for greater targeting specificity and differentiation between early- and late-stage atherosclerotic lesions. These proof-of-concept studies also verified that PAMs are safe enough to be used pre-clinically and are cleared renally38. Since monocytes and inflammation are characteristic to other diseases, MCP-1 PAMs have the potential to be used for therapeutic and diagnostic applications in other diseases beyond atherosclerosis8,39,40,41.
Herein, we report the fabrication of highly scalable and self-assembled MCP-1 PAMs that demonstrated the particle&#39;s optimal size, surface charge, and selective targeting to monocytes for enhanced imaging applications in atherosclerosis.

<table border="0" cellpadding="0" cellspacing="0" width="834">
	<tbody>
		<tr height="20">
			<td height="20" style="height:20px;width:309px;">1,2-ethanedithiol</td>
			<td style="width:147px;">VWR</td>
			<td style="width:119px;">E0032</td>
			<td style="width:259px;">for peptide synthesis</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">10 mL disposable serological pipets</td>
			<td>VWR</td>
			<td>89130-898</td>
			<td>for cell culture</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">15 mL centrifuge tubes, polypropylene</td>
			<td>VWR</td>
			<td>89401-566</td>
			<td>for various applications</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">2,5-dihydroxybenzoic acid, 99%</td>
			<td style="width:147px;">Fisher Scientific</td>
			<td>AC165200050</td>
			<td>for MALDI</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">25 mL disposable serological pipets</td>
			<td>VWR</td>
			<td>89130-900</td>
			<td>for cell culture</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:309px;">2-Mercaptoethanol, 50 mM</td>
			<td style="width:147px;">ThermoFisher Scientific</td>
			<td style="width:119px;">31350010</td>
			<td>for cell culture</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">5 mL disposable serological pipets</td>
			<td>VWR</td>
			<td>89130-896</td>
			<td>for cell culture</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">50 mL centrifuge tubes</td>
			<td>VWR</td>
			<td>89039-658</td>
			<td>for various applications</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:309px;">75 cm2 culture flask</td>
			<td style="width:147px;">Fisher Scientific</td>
			<td style="width:119px;">13-680-65</td>
			<td>for cell culture</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">75 mL reaction vessel</td>
			<td>Protein Technologies</td>
			<td>3000005</td>
			<td>for peptide synthesis</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">96-wells cell culture plate</td>
			<td style="width:147px;">VWR</td>
			<td>40101-346</td>
			<td>for MTS assay</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Acetonitrile, HPLC grade</td>
			<td style="width:147px;">Fisher Scientific</td>
			<td>A998SK-4</td>
			<td>for HPLC purification</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Borosilicate glass, 1 dram</td>
			<td style="width:147px;">VWR</td>
			<td>66011-041</td>
			<td>for PAM synthesis</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Borosillicate glass pipet, Long tips</td>
			<td style="width:147px;">VWR</td>
			<td>14673-043</td>
			<td>for various applications</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Coverslip, 0.16-0.19 mm, 22 x 22 mm</td>
			<td style="width:147px;">Fisher Scientific</td>
			<td>12-542B</td>
			<td>for confocal microscopy</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:309px;">Cy5 amine</td>
			<td style="width:147px;">Abcam</td>
			<td style="width:119px;">ab146463</td>
			<td>for peptide conjugation</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:309px;">Diethyl ether, ACS grade</td>
			<td style="width:147px;">Fisher Scientific</td>
			<td style="width:119px;">E138-1</td>
			<td>for peptide precipitation</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Disposable syringes, 20 mL</td>
			<td style="width:147px;">Fisher Scientific</td>
			<td>14-817-54</td>
			<td>for HPLC purification</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Double neubauer ruled hemocytometer</td>
			<td style="width:147px;">VWR</td>
			<td>63510-13</td>
			<td>for cell counting</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:309px;">DSPE-PEG(2000) amine</td>
			<td>Avanti</td>
			<td style="width:119px;">880128P</td>
			<td>for peptide conjugation</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:309px;">DSPE-PEG(2000) maleimide</td>
			<td>Avanti</td>
			<td style="width:119px;">880126P</td>
			<td>for peptide conjugation</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">DSPE-PEG(2000)-NHS ester&#160;</td>
			<td>Nanocs</td>
			<td>PG2-DSNS-10K</td>
			<td>for conjugation to Cy5</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:309px;">Dulbecco&#39;s modified eagle medium-high glucose</td>
			<td style="width:147px;">Sigma Aldrich</td>
			<td style="width:119px;">D5796-500ML</td>
			<td>for cell culture</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Fetal bovine serum, qualified, heat inactivated</td>
			<td>ThermoFisher Scientific</td>
			<td>10438026</td>
			<td>for cell culture</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Fmoc-L-Ala-OH /HBTU</td>
			<td>Protein Technologies</td>
			<td>PS3-H5-A</td>
			<td>for peptide synthesis</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Fmoc-L-Arg(Pbf)-OH /HBTU</td>
			<td>Protein Technologies</td>
			<td style="width:119px;">PS3-H5-RBF</td>
			<td>for peptide synthesis</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Fmoc-L-Asn(Trt)-OH /HBTU</td>
			<td>Protein Technologies</td>
			<td style="width:119px;">PS3-H5-NT</td>
			<td>for peptide synthesis</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Fmoc-L-Cys(Trt)-OH /HBTU</td>
			<td>Protein Technologies</td>
			<td style="width:119px;">PS3-H5-CT</td>
			<td>for peptide synthesis</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Fmoc-L-Gln(Trt)-OH /HBTU</td>
			<td>Protein Technologies</td>
			<td>PS3-H5-QT</td>
			<td>for peptide synthesis</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Fmoc-L-Ile-OH /HBTU</td>
			<td>Protein Technologies</td>
			<td style="width:119px;">PS3-H5-I</td>
			<td>for peptide synthesis</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Fmoc-L-Leu-OH /HBTU</td>
			<td>Protein Technologies</td>
			<td>PS3-H5-L</td>
			<td>for peptide synthesis</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Fmoc-L-Lys(Boc)-OH /HBTU</td>
			<td>Protein Technologies</td>
			<td>PS3-H5-KBC</td>
			<td>for peptide synthesis</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Fmoc-L-Phe-OH /HBTU</td>
			<td>Protein Technologies</td>
			<td style="width:119px;">PS3-H5-F</td>
			<td>for peptide synthesis</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Fmoc-L-Ser(tBu)-OH /HBTU</td>
			<td>Protein Technologies</td>
			<td style="width:119px;">PS3-H5-SB</td>
			<td>for peptide synthesis</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Fmoc-L-Thr(tBu)-OH /HBTU</td>
			<td>Protein Technologies</td>
			<td>PS3-H5-TB</td>
			<td>for peptide synthesis</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Fmoc-L-Tyr(tBu)-OH /HBTU</td>
			<td>Protein Technologies</td>
			<td>PS3-H5-YB</td>
			<td>for peptide synthesis</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Fmoc-L-Val-OH /HBTU</td>
			<td>Protein Technologies</td>
			<td>PS3-H5-V</td>
			<td>for peptide synthesis</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:309px;">Fmoc-Lys(Boc)-wang resin, 100-200 mesh</td>
			<td>Novabiochem</td>
			<td style="width:119px;">856013</td>
			<td>for peptide synthesis</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Formic acid, optima LC/MS grade</td>
			<td style="width:147px;">Fisher Scientific</td>
			<td>A117-50</td>
			<td>for HPLC purification</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:309px;">Glycerol</td>
			<td style="width:147px;">VWR</td>
			<td style="width:119px;">M152-1L</td>
			<td>for confocal microscopy</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Hand tally counter</td>
			<td style="width:147px;">Fisher Scientific</td>
			<td>S90189</td>
			<td>for cell counting</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Magnetic stir bars, egg-shaped</td>
			<td style="width:147px;">VWR</td>
			<td>58949-006</td>
			<td>for peptide conjugation</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Methanol, ACS certified</td>
			<td style="width:147px;">Fisher Scientific</td>
			<td>A412-4</td>
			<td>for PAM synthesis</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">MTS cell proliferation colorimetric assay kit</td>
			<td style="width:147px;">VWR</td>
			<td style="width:119px;">10191-104</td>
			<td>for MTS assay</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">N,N-Dimethylformamide, sequencing grade</td>
			<td style="width:147px;">Fisher Scientific</td>
			<td>BP1160-4</td>
			<td>for peptide synthesis</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">N-Methylmorpholine</td>
			<td>Protein Technologies</td>
			<td>S-1L-NMM</td>
			<td>for peptide synthesis</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:309px;">Paraformaldehyde</td>
			<td style="width:147px;">Fisher Scientific</td>
			<td style="width:119px;">AC416780250</td>
			<td>for fixing cells</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">PBS, pH 7.4</td>
			<td style="width:147px;">ThermoFisher Scientific</td>
			<td>10010049</td>
			<td>for various applications</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Penicillin/streptomycin, 10,000 U/mL</td>
			<td>ThermoFisher Scientific</td>
			<td>15140122</td>
			<td>for cell culture</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:309px;">Peptide synthesis vessel, 25 mL&#160;</td>
			<td style="width:147px;">Fisher Scientific</td>
			<td style="width:119px;">CG186011</td>
			<td>for peptide synthesis</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:309px;">Phosphotungstic acid&#160;</td>
			<td style="width:147px;">Fisher Scientific</td>
			<td style="width:119px;">A248-25</td>
			<td>for TEM</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Piperidine</td>
			<td>Spectrum</td>
			<td>P1146-2.5LTGL</td>
			<td>for peptide synthesis</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Plain glass microscope slide 75 x 25 mm</td>
			<td style="width:147px;">Fisher Scientific</td>
			<td>12-550-A3</td>
			<td>for confocal microscopy</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Reagent reservoirs, sterile&#160;</td>
			<td>VWR</td>
			<td>95128093</td>
			<td>for cell culture</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:309px;">Self-closing tweezer</td>
			<td style="width:147px;">TedPella</td>
			<td style="width:119px;">515</td>
			<td>for TEM</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">TEM support film</td>
			<td style="width:147px;">TedPella</td>
			<td style="width:119px;">01814F</td>
			<td>for TEM</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Trifluoroacetic acid&#160;</td>
			<td style="width:147px;">Fisher Scientific</td>
			<td>BP618-500</td>
			<td>for peptide cleavage and HPLC purification</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Triisopropylsilane</td>
			<td style="width:147px;">VWR</td>
			<td>TCT1533-5ml</td>
			<td>for peptide cleavage</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Trypan blue solution, 0.4%</td>
			<td style="width:147px;">ThermoFisher Scientific</td>
			<td style="width:119px;">15250061</td>
			<td>for cell counting</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Tweezer, general purpose-serrated</td>
			<td style="width:147px;">VWR</td>
			<td>231-SA-SE</td>
			<td>for confocal microscopy</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">WEHI-274.1</td>
			<td>ATCC</td>
			<td style="width:119px;">ATCC&#160;CRL-1679</td>
			<td>murine monocyte</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:309px;">automated benchtop peptide synthesizer</td>
			<td>Protein Technologies</td>
			<td style="width:119px;"></td>
			<td style="width:259px;">PS3 Benchtop Peptide Synthesizer</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">&#945;- cyano- 4- hydroxycinnamic acid, 99%</td>
			<td style="width:147px;">Sigma Aldrich</td>
			<td>476870-2G</td>
			<td>for MALDI</td>
		</tr>
	</tbody>
</table>

synthesis of monocyte-targeting peptide amphiphile micelles for imaging of atherosclerosis

Atherosclerosis is a major contributor to cardiovascular disease, the leading cause of death worldwide, which claims 17.3 million lives annually. Atherosclerosis is also the leading cause of sudden death and myocardial infarction, instigated by unstable plaques that rupture and occlude the blood vessel without warning. Current imaging modalities cannot differentiate between stable and unstable plaques that rupture. Peptide amphiphiles micelles (PAMs) can overcome this drawback as they can be modified with a variety of targeting moieties that bind specifically to diseased tissue. Monocytes have been shown to be early markers of atherosclerosis, while large accumulation of monocytes is associated with plaques prone to rupture. Hence, nanoparticles that can target monocytes can be used to discriminate different stages of atherosclerosis. To that end, here, we describe a protocol for the preparation of monocyte-targeting PAMs (monocyte chemoattractant protein-1 (MCP-1) PAMs). MCP-1 PAMs are self-assembled through synthesis under mild conditions to form nanoparticles of 15 nm in diameter with near neutral surface charge. In vitro, PAMs were found to be biocompatible and had a high binding affinity for monocytes. The methods described herein show promise for a wide range of applications in atherosclerosis as well as other inflammatory diseases.

Preparation of MCP-1 PAM 
The CCR2-binding motif (residues 13-35) of the MCP-1 protein [YNFTNRKISVQRLASYRRITSSK] or scrambled peptide [YNSLVFRIRNSTQRKYRASIST] was modified by adding a cysteine residue on the N-terminus. The MCP-1 peptide was synthesized by a Fmoc-mediated solid-phase method using an automated peptide synthesizer. The crude peptide was purified by reverse-phase HPLC on a C8 column at 50 &#176;C using 0.1% TFA in acetonitrile/water mixtures and charact...

Watch this Scientific Journal Video about Synthesis of Monocyte-targeting Peptide Amphiphile Micelles for Imaging of Atherosclerosis at JoVE.com

Synthesis of Monocyte-targeting Peptide Amphiphile Micelles for Imaging of Atherosclerosis

This paper presents a method involving the synthesis and characterization of monocyte-targeting peptide amphiphile micelles and the corresponding assays to test for biocompatibility and ability of the micelle to bind to monocytes.

Atherosclerosis is a major contributor to cardiovascular disease, the leading cause of death worldwide, which claims 17.3 million lives annually. ...

The overall goal of this protocol is to synthesize monocyte-targeting peptide amphiphile micelles for atherosclerosis imaging. This method can help answer key question in the cardiovascular field about diagnostic imaging of atherosclerotic plaque. The main advantage of this technique is that the incorporation of peptide amphiphile micelles with MCP-1 allow a greater targeting specificity and differentiation between early and late-stage atherosclerotic lesions.The implications of this technique extend to the diagnosis of plaque at different stages of atherosclerosis, as patients with rupture-prone, late-stage plaques contain higher number of monocytes. Though this method can provide insight into atherosclerosis, it can also be applied to other diseases, such as cancer. Demonstrating the procedure with me will be Jonathan Wang, a graduate student from our laboratory.Begin by weighing out 0.25 millimoles of fmach-L-lysine-bach-wong-resin in a reaction vessel. Transfer the vessel to a chemical fume hood and rinse the vessel sides with five milliliters of dimethylforamide. Load the reaction vessel and prepackaged amino acid vials from the C-to-N terminus, onto an automated benchtop peptide synthesizer, including an empty vial at the end for the final deprotection setp.After running the synthesis, transfer the peptides and resin from the reaction vessel into a scintillation vial containing two to three milliliters of methanol until all of the resin has been transferred. When the resin has sunk to the bottom of the vial, remove the supernane and allow the resin to air dry, followed by vacuum drying for at least two hours at room temperature. When the vial is completely dry, use a clamp to secure the bottom half of a synthesis vessel onto an arm shaker and add two milliliters of cleavage solution to the scintillation vial.Transfer the entire volume of peptide resin to the synthesis vessel and wash the sides of the vessel with three milliters of fresh cleavage solution. Then shake the vessel, capped, for four hours at 300 oscillations per minute. At the end of the shaking incubation, drain the cleaved peptide solution into a balanced-weighed 50 milliliter conical tube and rinse the synthesis vessel several times with the remaining cleavage solution.Evaporate the cleaved peptide solution with nitrogen until there is less than four milliliters of solution remaining in the centrifuge tube and add 36 milliliters of ice cold ether to the peptide cleaved solution. Vortex the resulting solution. When the suspension turns completely white or yellow, pellet the peptides by centrifugation.Resuspend the peptide in 40 milliliters of ice cold ether and vortex and sonicate the peptide again. After a second centrifugation and supernatant decanting, dry the crude peptide amphiphile pellet with nitrogen gas purging. When the ether has been visibly evaporated, add 20 milliliters of double distilled water to the tube and vortex and sonicate the tube until the peptide is completely dissolved in solution.Freeze the solution and lifelize until dry. Then weigh the tube again and dissolve the crude peptide in five milligrams per milliliter water. Next, inject the entire volume of crude MCP-1 peptide into a high-performance liquid chromotography or HPLC instrument.Analyze each fraction using matrix-assisted laser desorption ionization mass spectroscopy for the expected product mass charge at 2, 890. Then combine the product fractions. Blow off the acetonitrile and freeze and lifelize the purified peptides until dry.To prepare the MCP-1 peptide amphiphiles or PAs, first dissolve the lifelized peptide in 15 milligrams per milliliter of water and combine the peptide solution with 15 milligrams per milliliter of DSPE PEG 2000 millimide solution. Add one mole of sodium hydroxide dropwise until the pH of the solution equals seven. Then nitrogen purge for five minutes, followed by overnight stirring.The next morning, freeze and lifelize the solution. When the crude product is dry, dissolve the solid in five milligrams per milliliter water and purify the peptide by HPLC, as just demonstrated. To assemble the PA membranes, dissolve 1.75 milligrams of the MCP-1 PAs in three milliliters of methanol in a one dram vial and sonicate until the MCP-1 PA is completely dissolved.Evaporate the methanol under nitrogen while moving the vial a circular motion and rinsing the remaining methanol off of the sides of the vial, until a uniform film is formed at the bottom. Vacuum dry the film overnight. The next morning, hydrate the film with three milliliters of water to make a 100 micromolar MCP-1 PAM solution and gently vortex and sonicate the solution until clear.Incubate the solution at 80 degrees Celsius for 30 minutes, then cool the resulting dispersion. In the following representative experiment, MCP-1 and scrambled peptide were purified by reverse-phase HPLC on a CA column at 50 degrees Celsius using 0.1%trifluoroacetic acid in acetonitrile water mixtures. And characterized by matrix-assisted laser desorption ionization mass spectrometry, as just demonstrated.Desisting containing peptides were conjugated onto DSPE PEG 2000 milliamide to yield DSPE PEG 2000 peptide conjugates via a thioether linkage and purified by HPLC using a C4 column. Dynamic light scattering analysis and transmission electron microscopy imaging of the monocyte targeting PAMs revealed well dispersed spherical nanoparticles with slightly positive zeta potentials. Circular dicroisms spectroscopy analysis confirmed the incorporation of the MCP-1 peptide within the micelle enhanced the secondary structure.The incubation amalse monocytes with up to 100 micromolar concentrations of MCP-1 peptide, MCP-1 PAM, scrambled peptide, and scrambled PAM for 72 hours demonstrated the viability and biocompatibility of the peptides. The specific binding of the monocytes to MCP-1 PAMs compared to scrambled PAMs is then established by confocal microscopy. After watching this video you should have a good understanding of how to prepare monocyte targeting peptide amphiphile micelle through the synthesis and purification of the MCP-1 peptide and the preparation of the MCP-1 peptide amphiphile and micelle assembly.Don't forget that working with chemical reagent can be extremely hazardous and that precautions, such as reading the MSDS and working inside a chemical fume hood should always be taken when working with this materials.

synthesis-monocyte-targeting-peptide-amphiphile-micelles-for-imaging

Research

JoVE Journal

Bioengineering

Synthesis, Assembly, and Characterization of Monolayer Protected Gold Nanoparticle Films for Protein Monolayer Electrochemistry

Colloidal gold nanoparticles protected with alkanethiolate ligands called monolayer protected gold clusters (MPCs) are synthesized and subsequently incorporated into film assemblies that serve as adsorption platforms for protein monolayer electrochemistry (PME). PME is utilized as the model system for studying electrochemical properties of redox proteins by confining them to an adsorption platform at a modified electrode, which also serves as a redox partner for electron transfer (ET) reactions. Studies have shown that gold nanoparticle film assemblies of this nature provide for a more homogeneous protein adsorption environment and promote ET without distance dependence compared to the more traditional systems modified with alkanethiol self-assembled monolayers (SAM).1-3 In this paper, MPCs functionalized with hexanethiolate ligands are synthesized using a modified Brust reaction4 and characterized with ultraviolet visible (UV-Vis) spectroscopy, transmission electron microscopy (TEM), and proton (1H) nuclear magnetic resonance (NMR). MPC films are assembled on SAM modified gold electrode interfaces by using a "dip cycle" method of alternating MPC layers and dithiol linking molecules. Film growth at gold electrode is tracked electrochemically by measuring changes to the double layer charging current of the system. Analogous films assembled on silane modified glass slides allow for optical monitoring of film growth and cross-sectional TEM analysis provides an estimated film thickness. During film assembly, manipulation of the MPC ligand protection as well as the interparticle linkage mechanism allow for networked films, that are readily adaptable, to interface with redox protein having different adsorption mechanism. For example, Pseudomonas aeruginosa azurin (AZ) can be adsorbed hydrophobically to dithiol-linked films of hexanethiolate MPCs and cytochrome c (cyt c) can be immobilized electrostatically at a carboxylic acid modified MPC interfacial layer. In this report, we focus on the film protocol for the AZ system exclusively. Investigations involving the adsorption of proteins on MPC modified synthetic platforms could further the understanding of interactions between biomolecules and man-made materials, and consequently aid the development of biosensor schemes, ET modeling systems, and synthetic biocompatible materials.5-8

Alkanethiolate stabilized gold colloids known as monolayer protected clusters (MPCs) are synthesized, characterized, and assembled into thin films as an adsorption interface for protein monolayer electrochemistry of simple redox protein like Pseudomonas aeruginosa azurin (AZ) and cytochrome c (cyt c).

Colloidal gold nanoparticles protected with alkanethiolate ligands called monolayer protected gold clusters (MPCs) are synthesized and subsequently ...

Cultivation of Human Neural Progenitor Cells in a 3-dimensional Self-assembling Peptide Hydrogel

The influence of 3-dimensional (3D) scaffolds on growth, proliferation and finally neuronal differentiation is of great interest in order to find new methods for cell-based and standardised therapies in neurological disorders or neurodegenerative diseases. 3D structures are expected to provide an environment much closer to the in vivo situation than 2D cultures. In the context of regenerative medicine, the combination of biomaterial scaffolds with neural stem and progenitor cells holds great promise as a therapeutic tool.1-5 Culture systems emulating a three dimensional environment have been shown to influence proliferation and differentiation in different types of stem and progenitor cells. Herein, the formation and functionalisation of the 3D-microenviroment is important to determine the survival and fate of the embedded cells.6-8 Here we used PuraMatrix9,10 (RADA16, PM), a peptide based hydrogel scaffold, which is well described and used to study the influence of a 3D-environment on different cell types.7,11-14 PuraMatrix can be customised easily and the synthetic fabrication of the nano-fibers provides a 3D-culture system of high reliability, which is in addition xeno-free.
Recently we have studied the influence of the PM-concentration on the formation of the scaffold.13 In this study the used concentrations of PM had a direct impact on the formation of the 3D-structure, which was demonstrated by atomic force microscopy. A subsequent analysis of the survival and differentiation of the hNPCs revealed an influence of the used concentrations of PM on the fate of the embedded cells. However, the analysis of survival or neuronal differentiation by means of immunofluorescence techniques posses some hurdles. To gain reliable data, one has to determine the total number of cells within a matrix to obtain the relative number of e.g. neuronal cells marked by &beta;III-tubulin. This prerequisites a technique to analyse the scaffolds in all 3-dimensions by a confocal microscope or a comparable technique like fluorescence microscopes able to take z-stacks of the specimen. Furthermore this kind of analysis is extremely time consuming. 
Here we demonstrate a method to release cells from the 3D-scaffolds for the later analysis e.g. by flow cytometry. In this protocol human neural progenitor cells (hNPCs) of the ReNcell VM cell line (Millipore USA) were cultured and differentiated in 3D-scaffolds consisting of PuraMatrix (PM) or PuraMatrix supplemented with laminin (PML). In our hands a PM-concentration of 0.25% was optimal for the cultivation of the cells13, however the concentration might be adapted to other cell types.12 The released cells can be used for e.g. immunocytochemical studies and subsequently analysed by flow cytometry. This speeds up the analysis and more over, the obtained data rest upon a wider base, improving the reliability of the data.

Here we describe the use of a self-assembling 3-dimensional scaffold to culture human neural progenitor cells. We present a protocol to release the cells from the scaffolds to be analysed subsequently e.g. by flow cytometry. This protocol might be adapted to other cell types to perform detailed mechanistically studies.

The  influence of 3-dimensional (3D) scaffolds on growth, proliferation and finally  neuronal differentiation is of great interest in order to find new ...

Wideband Optical Detector of Ultrasound for Medical Imaging Applications

Optical sensors of ultrasound are a promising alternative to piezoelectric techniques, as has been recently demonstrated in the field of optoacoustic imaging. In medical applications, one of the major limitations of optical sensing technology is its susceptibility to environmental conditions, e.g. changes in pressure and temperature, which may saturate the detection. Additionally, the clinical environment often imposes stringent limits on the size and robustness of the sensor. In this work, the combination of pulse interferometry and fiber-based optical sensing is demonstrated for ultrasound detection. Pulse interferometry enables robust performance of the readout system in the presence of rapid variations in the environmental conditions, whereas the use of all-fiber technology leads to a mechanically flexible sensing element compatible with highly demanding medical applications such as intravascular imaging. In order to achieve a short sensor length, a pi-phase-shifted fiber Bragg grating is used, which acts as a resonator trapping light over an effective length of 350 &#181;m. To enable high bandwidth, the sensor is used for sideway detection of ultrasound, which is highly beneficial in circumferential imaging geometries such as intravascular imaging. An optoacoustic imaging setup is used to determine the response of the sensor for acoustic point sources at different positions.

Optical detection of ultrasound is impractical in many imaging scenarios because it often requires stable environmental conditions. We demonstrate an optical technique for ultrasound sensing in volatile environments with miniaturization and sensitivity levels appropriate for optoacoustic imaging in restrictive scenarios, e.g. intravascular applications.

Optical sensors of ultrasound are a promising alternative to piezoelectric techniques, as has been recently demonstrated in the field of optoacoustic ...

Synthesis of Keratin-based Nanofiber for Biomedical Engineering

Electrospinning, due to its versatility and potential for applications in various fields, is being frequently used to fabricate nanofibers. Production of these porous nanofibers is of great interest due to their unique physiochemical properties. Here we elaborate on the fabrication of keratin containing poly (&#949;-caprolactone) (PCL) nanofibers (i.e., PCL/keratin composite fiber). Water soluble keratin was first extracted from human hair and mixed with PCL in different ratios. The blended solution of PCL/keratin was transformed into nanofibrous membranes using a laboratory designed electrospinning set up. Fiber morphology and mechanical properties of the obtained nanofiber were observed and measured using scanning electron microscopy and tensile tester. Furthermore, degradability and chemical properties of the nanofiber were studied by FTIR. SEM images showed uniform surface morphology for PCL/keratin fibers of different compositions. These PCL/keratin fibers also showed excellent mechanical properties such as Young&#39;s modulus and failure point. Fibroblast cells were able to attach and proliferate thus proving good cell viability. Based on the characteristics discussed above, we can strongly argue that the blended nanofibers of natural and synthetic polymers can represent an excellent development of composite materials that can be used for different biomedical applications.

Electrospun nanofibers have a high surface area to weight ratio, excellent mechanical integrity, and support cell growth and proliferation. These nanofibers have a wide range of biomedical applications. Here we fabricate keratin/ PCL nanofibers, using the electrospinning technique, and characterize the fibers for possible applications in tissue engineering.

Electrospinning, due to its versatility and potential for applications in various fields, is being frequently used to fabricate nanofibers. Production of ...

Microwave-driven Synthesis of Iron Oxide Nanoparticles for Fast Detection of Atherosclerosis

A fast and reproducible microwave-driven protocol has been developed for the synthesis of neridronate-functionalized nanoparticles. Starting from the synthesis of hydrophobic nanoparticles, our method is based on an adaptation from thermal decomposition method to microwave driven synthesis. The new methodology produces a decrease in the reaction times in comparison with traditional procedures. Moreover, the use of the microwave technology increases the reproducibility of the reactions, something important from the point of view of clinical applications. The novelty of this iron oxide nanoparticle is the attachment of Neridronate. The use of this molecule leads a bisphosphonate moiety towards the outside of the nanoparticle that provides Ca2+ binding properties in vitro and selective accumulation in vivo in the atheroma plaque. The protocol allows the synthesis and plaque detection in about 3 hr since the initial synthesis from organic precursors. Their accumulation in the atherosclerotic area in less than 1 hr provides a contrast agent particularly suitable for clinical applications.

Microwave technology enables extremely fast synthesis of iron oxide nanoparticles for atherosclerosis plaque characterization. The use of an aminobisphosphonate in the external side of the nanoparticle provides a fast accumulation in the atherosclerotic area.

A fast and reproducible microwave-driven protocol has been developed for the synthesis of neridronate-functionalized nanoparticles. Starting from the ...

Preparation and Characterization of Lipophilic Doxorubicin Pro-drug Micelles

Micelles have been successfully used for the delivery of anticancer drugs. Amphiphilic polymers form core-shell structured micelles in an aqueous environment through self-assembly. The hydrophobic core of micelles functions as a drug reservoir and encapsulates hydrophobic drugs. The hydrophilic shell prevents the aggregation of micelles and also prolongs their systemic circulation in vivo. In this protocol, we describe a method to synthesize a doxorubicin lipophilic pro-drug, doxorubicin-palmitic acid (DOX-PA), which will enhance drug loading into micelles. A pH-sensitive hydrazone linker was used to conjugate doxorubicin with the lipid, which facilitates the release of free doxorubicin inside cancer cells. Synthesized DOX-PA was purified with a silica gel column using dichloromethane/methanol as the eluent. Purified DOX-PA was analyzed with thin layer chromatography (TLC) and 1H-Nuclear Magnetic Resonance Spectroscopy (1H-NMR). A film dispersion method was used to prepare DOX-PA loaded DSPE-PEG micelles. In addition, several methods for characterizing micelle formulations are described, including determination of DOX-PA concentration and encapsulation efficiency, measurement of particle size and distribution, and assessment of in vitro anticancer activities. This protocol provides useful information regarding the preparation and characterization of drug-loaded micelles and thus will facilitate the research and development of novel micelle-based cancer nanomedicines.

A protocol for the preparation and characterization of lipophilic doxorubicin pro-drug loaded 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[amino(polyethylene glycol)-2000] (DSPE-PEG) micelles is described.

Micelles have been successfully used for the delivery of anticancer drugs. Amphiphilic polymers form core-shell structured micelles in an aqueous ...

Synthesis of Cationized Magnetoferritin for Ultra-fast Magnetization of Cells

Many important biomedical applications, such as cell imaging and remote manipulation, can be achieved by labeling cells with superparamagnetic iron oxide nanoparticles (SPIONs). Achieving sufficient cellular uptake of SPIONs is a challenge that has traditionally been met by exposing cells to elevated concentrations of SPIONs or by prolonging exposure times (up to 72 hr). However, these strategies are likely to mediate toxicity. Here, we present the synthesis of the protein-based SPION magnetoferritin as well as a facile surface functionalization protocol that enables rapid cell magnetization using low exposure concentrations. The SPION core of magnetoferritin consists of cobalt-doped iron oxide with an average particle diameter of 8.2 nm mineralized inside the cavity of horse spleen apo-ferritin. Chemical cationization of magnetoferritin produced a novel, highly membrane-active SPION that magnetized human mesenchymal stem cells (hMSCs) using incubation times as short as one minute and iron concentrations as lows as 0.2 mM.

A protocol for the synthesis and cationization of cobalt-doped magnetoferritin is presented, as well as a method to rapidly magnetize stem cells with cationized magnetoferritin.

Many important biomedical applications, such as cell imaging and remote manipulation, can be achieved by labeling cells with superparamagnetic iron oxide ...

Design and Synthesis of a Reconfigurable DNA Accordion Rack

DNA nanostructure-based mechanical systems or DNA nanomachines, which produce complex nanoscale motion in 2D and 3D in the nanometer to &#229;ngstr&#246;m resolution, show great potential in various fields of nanotechnology such as the molecular reactors, drug delivery, and nanoplasmonic systems. The reconfigurable DNA accordion rack, which can collectively manipulate a 2D or 3D nanoscale network of elements, in multiple stages in response to the DNA inputs, is described. The platform has potential to increase the number of elements that DNA nanomachines can control from a few elements to a network scale with multiple stages of reconfiguration.
In this protocol, we describe the entire experimental process of the reconfigurable DNA accordion rack of 6 by 6 meshes. The protocol includes a design rule and simulation procedure of the structures and a wet-lab experiment for synthesis and reconfiguration. In addition, analysis of the structure using TEM (transmission electron microscopy) and FRET (fluorescence resonance energy transfer) is included in the protocol. The novel design and simulation methods covered in this protocol will assist researchers to use the DNA accordion rack for further applications.

We describe the detailed protocol for design, simulation, wet-lab experiments, and analysis for a reconfigurable DNA accordion rack of 6 by 6 meshes.

DNA nanostructure-based mechanical systems or DNA nanomachines, which produce complex nanoscale motion in 2D and 3D in the nanometer to &#229;ngstr&#246;m ...

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 ...

Synthesis of Near-Infrared Emitting Gold Nanoclusters for Biological Applications

Over the past decade, fluorescent gold nanoclusters (AuNCs) have witnessed growing popularity in biological applications and enormous efforts have been devoted to their development. In this protocol, a recently developed, facile method for preparation of water soluble, biocompatible, and colloidally stable near-infrared emitting AuNCs have been described in detail. This room-temperature, bottom-up chemical synthesis provides easily functionalizable AuNCs capped with thioctic acid and thiol-modified polyethylene glycol in aqueous solution. The synthetic approach requires neither organic solvents or additional ligand exchange nor extensive knowledge of synthetic chemistry to reproduce. The resulting AuNCs offer free surface carboxylic acids, which can be functionalized with various biological molecules bearing a free amine group without adversely affecting the photoluminescent properties of the AuNCs. A quick, reliable procedure for flow cytometric quantification and confocal microscopic imaging of AuNC uptake by HeLa cells also been described. Due to the large Stokes shift, proper setting of filters in flow cytometry and confocal microscopy is necessary for efficient detection of near-infrared photoluminescence of AuNCs.

A reliable and easily reproducible method for preparation of functionalizable, near-infrared emitting photoluminescent gold nanoclusters and their direct detection inside HeLa cells by flow cytometry and confocal laser scanning microscopy is described.

Over the past decade, fluorescent gold nanoclusters (AuNCs) have witnessed growing popularity in biological applications and enormous efforts have been ...