Name: preparation and characterization of lipophilic doxorubicin pro-drug micelles
Uploaded: 2016-08-02T15:00:00
Description: Watch this Scientific Journal Video about Preparation and Characterization of Lipophilic Doxorubicin Pro-drug Micelles at JoVE.com

This work was supported by the following grants: NIH-SC3 grant, NSF-PREM grant, Hampton University Faculty Research Grant. We would like to thank Mrs. Michele A. Cochran at Virginia Institute of Marine Science (VIMS) for the use of the particle size analyzer. We would also like to thank Mrs. Corinne R. Ramaley for reviewing the manuscript.

1. Synthesis of DOX-PA
<ol>
	<li>Weigh 390 mg of doxorubicin and 243 mg of palmitic acid hydrazide, and transfer to a round bottom flask.</li>
	<li>Add 150 ml of anhydrous methanol to the flask with a glass syringe. Add 39 &#181;l of trifluoroacetic acid (TFA) with a pipette. Using a magnetic stirrer, stir the reaction mixture for 18 hr at RT in the dark. 
	NOTE: The quantities of reaction materials can be scaled up or down to obtain different amounts of DOX-PA. The ratio of reactants should be ma...

<ol>
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I., Huang, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Doxorubicin+and+lapatinib+combination+nanomedicine+for+treating+resistant+breast+cancer.">Doxorubicin and lapatinib combination nanomedicine for treating resistant breast cancer.</a> Mol Pharm. 11 (8), 2600-2611 (2014).</li><li>Ma, P., Rahima Benhabbour, S., Feng, L., Mumper, R. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=2'-Behenoyl-paclitaxel+conjugate+containing+lipid+nanoparticles+for+the+treatment+of+metastatic+breast+cancer.">2'-Behenoyl-paclitaxel conjugate containing lipid nanoparticles for the treatment of metastatic breast cancer.</a> Cancer Lett. 334 (2), 253-262 (2013).</li><li>Lundberg, B. B., Risovic, V., Ramaswamy, M., Wasan, K. 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(64), (2012).</li><li>Ulbrich, K., Etrych, T., Chytil, P., Jelinkova, M., Rihova, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=HPMA+copolymers+with+pH-controlled+release+of+doxorubicin:+in+vitro+cytotoxicity+and+in+vivo+antitumor+activity.">HPMA copolymers with pH-controlled release of doxorubicin: in vitro cytotoxicity and in vivo antitumor activity.</a> J Controlled Release. 87 (1-3), 33-47 (2003).</li><li>Patil, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cellular+Delivery+of+Doxorubicin+via+pH-Controlled+Hydrazone+Linkage+Using+Multifunctional+Nano+Vehicle+Based+on+Poly(beta-L-Malic+Acid).">Cellular Delivery of Doxorubicin via pH-Controlled Hydrazone Linkage Using Multifunctional Nano Vehicle Based on Poly(beta-L-Malic Acid).</a> Int J Mol Sci. 13 (9), 11681-11693 (2012).</li><li>Hu, X., Liu, S., Huang, Y., Chen, X., Jing, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biodegradable+block+copolymer-doxorubicin+conjugates+via+different+linkages:+preparation,+characterization,+and+in+vitro+evaluation.">Biodegradable block copolymer-doxorubicin conjugates via different linkages: preparation, characterization, and in vitro evaluation.</a> Biomacromolecules. 11 (8), 2094-2102 (2010).</li><li>Huynh, L., Neale, C., Pomes, R., Allen, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Computational+approaches+to+the+rational+design+of+nanoemulsions,+polymeric+micelles,+and+dendrimers+for+drug+delivery.">Computational approaches to the rational design of nanoemulsions, polymeric micelles, and dendrimers for drug delivery.</a> Nanomedicine. 8 (1), 20-36 (2012).</li><li>Shi, C., 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=A+drug-specific+nanocarrier+design+for+efficient+anticancer+therapy.">A drug-specific nanocarrier design for efficient anticancer therapy.</a> Nat Commun. 6, 7449 (2015).</li></ol>

In this work, we describe an uncomplicated, rapid film-dispersion method for the preparation of micelles. This method utilizes the self-assembly properties of an amphiphilic polymer (e.g., DSPE-PEG) to form core-shell structured micelles in an aqueous environment. This micelle preparation method has several advantages. 1. It involves a simple formulation process, which avoids the use of complicated size-reduction steps (such as extrusion or homogenization) commonly used in the preparation of liposomes, nanoparti...

Chemotherapy is commonly used to treat various forms of cancers. Most, if not all, chemotherapy drugs have toxic side effects which may vary from manageable minor conditions, such as nausea and diarrhea, to more life threatening conditions. Because most anticancer drugs are toxic, non-selective exposure of these drugs to normal tissue inevitably causes toxicity. Therefore, there is a great need for a therapeutic approach that can selectively deliver drugs into cancer cells. Another challenge with the administration of anticancer drugs is their poor water solubility. Usually, solubilizing agents are needed to formulate these poorly soluble drugs. However, most solubilizing agents, such as dimethyl sulfoxide (DMSO), Cremophor EL, and Polysorbate 80 (Tween 80) may cause liver and kidney toxicity, hemolysis, acute hypersensitivity reactions and peripheral neuropathies.1 Therefore, safe and biocompatible formulations are needed for the clinical use of poorly soluble anticancer drugs. Nanocarriers are promising drug delivery systems for addressing the above challenges. These nanocarriers include liposomes,2 nanoparticles,3 micelles,4-7 polymer-drug conjugates,8 and inorganic materials.9 Several nanomedicine products (e.g., Doxil, Abraxane, and Genexol) have been approved by the regulatory agencies to treat cancer patients.10
Polymeric micelles are promising nano-scale drug delivery carriers, which have been successfully used for the delivery of anticancer drugs.4-7,11,12 Typical polymeric micelles are prepared from amphiphilic polymers through a self-assembly process. The core-shell structured polymeric micelles include a hydrophilic shell and a hydrophobic core. The hydrophilic shell can sterically stabilize micelles and prolong their circulation in blood stream. The hydrophobic core can effectively encapsulate hydrophobic drugs. Because of the small size of micelles (typically less than 200 nm) and long-circulation properties, polymeric micelles are believed to achieve tumor targeting through enhanced permeability and retention (EPR) effects (passive tumor targeting).
Drug loading stability is critical for the tumor targeting ability of micelles. To achieve optimal tumor targeting, micelles should have minimal drug leakage before reaching the tumor site, yet quickly release the drug after entering cancer cells. In addition, formulation stability is also an essential requirement for product development, because formulation stability determines the feasibility of product development, as well as the shelf-life of developed products. Recently, much effort has been made to improve the loading of drugs into delivery carriers. The lipophilic pro-drug approach is a strategy which has been explored to improve drug loading into lipid nanoparticles and emulsions.13,14 The conjugation of lipids with drugs can significantly improve their lipophilicity and enhance loading and retention in the lipophilic components of nanocarriers.
Here, we describe a protocol for preparing lipophilic doxorubicin pro-drug loaded micelles. First, the synthesis procedure for doxorubicin lipophilic pro-drug is described. Then, a protocol for generating micelles with a film-dispersion method is introduced. This method has been successfully used in our previous studies.5 DSPE-PEG was selected as the carrier material for preparing micelles because it has been successfully used for micelle drug delivery.15,16 Finally, we describe several in vitro assays used to characterize micelle formulations and to evaluate anticancer activity.

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	<tbody>
		<tr height="23">
			<td height="23" style="height:23px;width:216px;">DSPE-PEG2K</td>
			<td style="width:191px;">Cordenpharm</td>
			<td style="width:119px;">LP-R4-039</td>
			<td style="width:167px;">&#62;95%</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Doxorubicin</td>
			<td style="width:191px;">LC Laboratories</td>
			<td style="width:119px;">D-4000</td>
			<td>&#62;99%</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Palmitic Acid Hydrazide</td>
			<td style="width:191px;">TCI AMERICA&#160;&#160;</td>
			<td style="width:119px;">P000425G</td>
			<td>&#62;98.0%</td>
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			<td height="21" style="height:21px;width:216px;">Methanol</td>
			<td style="width:191px;">ACROS Organics</td>
			<td style="width:119px;">610981000</td>
			<td>Anhydrous</td>
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		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Methylene chloride&#160;</td>
			<td style="width:191px;">FISHER&#160;</td>
			<td style="width:119px;">D151-4</td>
			<td>99.90%</td>
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		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Methyl sulfoxide-d6</td>
			<td style="width:191px;">ACROS Organics</td>
			<td style="width:119px;">AC320760075</td>
			<td>NMR solvent</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Trifluoroacetic Acid&#160;</td>
			<td style="width:191px;">ACROS Organics</td>
			<td style="width:119px;">AC293811000</td>
			<td>99.50%</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Silica Gel</td>
			<td style="width:191px;">FISHER&#160;</td>
			<td style="width:119px;">L-7446</td>
			<td>230-400 mesh</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">BAKER FLEX TLC PLATES&#160;</td>
			<td style="width:191px;">FISHER&#160;</td>
			<td style="width:119px;">NC9990129</td>
			<td></td>
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		<tr height="21">
			<td height="21" style="height:21px;width:216px;">DPBS</td>
			<td style="width:191px;">Sigma-Aldrich</td>
			<td style="width:119px;">D8537</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">DU 145&#160; Prostate Cancer Cells</td>
			<td style="width:191px;">ATCC</td>
			<td style="width:119px;">HTB-81</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">MTT</td>
			<td style="width:191px;">ACROS Organics</td>
			<td style="width:119px;">158990050</td>
			<td>98%</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">RPMI 1640 Medium</td>
			<td style="width:191px;">MEDIATECH INC&#160;</td>
			<td style="width:119px;">10041CV</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Antibiotic-Antimycotic&#160;</td>
			<td style="width:191px;">LIFE TECHNOLOGIES&#160;</td>
			<td style="width:119px;">15240062</td>
			<td>100x stock solution</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Fetal Bovine Serum</td>
			<td style="width:191px;">LIFE TECHNOLOGIES&#160;</td>
			<td style="width:119px;">10437077</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Nuclear Magnetic Resonance Spectroscopy</td>
			<td style="width:191px;">Varian, Inc</td>
			<td style="width:119px;"></td>
			<td>300 NMR&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">B&#252;chi R-3 Rotavapor</td>
			<td style="width:191px;">Buchi</td>
			<td style="width:119px;">1103022V1&#160;</td>
			<td>Rotary evaporator</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Ultrasonic Bath</td>
			<td style="width:191px;">BRANSON ULTRASONICS CORPORATION&#160;</td>
			<td style="width:119px;">CPX952318R</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">UV-VIS spectrometer Biomate 3</td>
			<td style="width:191px;">Thermo Spectronic</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Zetasizer Nano ZS90&#160;</td>
			<td style="width:191px;">Malvern Instruments</td>
			<td style="width:119px;"></td>
			<td>Particle Size Analyer</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Microplate Spectrophotometer&#160;</td>
			<td style="width:191px;">Rio-Rad</td>
			<td style="width:119px;">Benchmark Plus&#160;</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Cell Culture Incubator</td>
			<td style="width:191px;">Napco</td>
			<td style="width:119px;">CO2 6000</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Biological Safety Cabinet</td>
			<td style="width:191px;">Nuaire</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">SigmaPlot&#160;</td>
			<td style="width:191px;">Systat Software, Inc.</td>
			<td style="width:119px;"></td>
			<td>Analytical Software</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">96-Well Cell Culture Plate</td>
			<td style="width:191px;">Becton Dickinson</td>
			<td style="width:119px;">353072</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Trypsin&#160; 0.25%</td>
			<td style="width:191px;">Corning Cellgro</td>
			<td style="width:119px;">25-053-CI</td>
			<td></td>
		</tr>
	</tbody>
</table>

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.

Figure 1 shows the synthesis scheme of DOX-PA. DOX-PA was synthesized by conjugation of palmitic acid with doxorubicin through a pH-sensitive hydrazone bond. A slight excess of palmitic acid hydrazide was used to facilitate the completion of the reaction. This reaction method has a very high efficiency and only a small amount of doxorubicin remained after an 18 hr reaction (Figure 2). The yield was approximately 88%. At the end of the reaction, DOX-PA was...

Watch this Scientific Journal Video about Preparation and Characterization of Lipophilic Doxorubicin Pro-drug Micelles at JoVE.com

Preparation and Characterization of Lipophilic Doxorubicin Pro-drug Micelles

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 ...

The overall goal of this protocol is to describe procedures for preparing and characterizing lipophilic doxorubicin prodrug loaded micell formulations. This method provides a simple and reliable approach for micell formulation. The synthesis of lipophilic prodrug of doxorubicin can enhance drug loading and stability, thus addressing a significant challenge in developing micell formulation.The micell formulation can enhance drug targeting into tumors and therefore can reduce toxicities of cancer treatment. In addition to the application described in this project, this technical can also be used to prepare the nanomedicine for the agents. To synthesize lipophilic doxorubicin prodrug DOX-PA, weigh 390 milligrams of doxorubicin and 243 milligrams of palmitic acid hydrozide, and transfer them to a round bottom flask.Add 150 milliliters of anhydrous methanol to the flask with a glass syringe. Then add 39 microliters of trifluoroacetic acid, or TFA, with a pipette. Using a magnetic stirrer, stir the reaction mixture for 18 hours at room temperature in the dark.To purify DOX-PA using a silica gel column, first remove the solvent in the reaction mixture with a rotary evaporator. Add three grams of silica gel after the volume of the mixture is reduced to around 20 milliliters. Continue rotary evaporation to yield dry powders and to allow the absorption of products onto the silica gel.Keep the sample under a vacuum for an additional 30 minutes after the dry powders are formed. Pack 50 grams of silica gel into a column using dichloromethane as a solvent. Carefully add the silica gel sample containing absorbed product to the column.Elute the column with a mixture of dichloromethane and methanol while gradually increasing the percentage of methanol, thereby increasing solvent polarity. Collect fractions of elluent in test tubes at 25 milliliters per tube, and monitor the progress by thin layer chromatography, or TLC. Combine all fractions containing pure DOX-PA and remove the solvent using a rotary evaporator until dry powder is formed.Further dry the product under a vacuum overnight. To prepare micelles, dissolve 40 milligrams of DSPE-PEG and four milligrams of DOX-PA with two milliliters of methanol in a 10 milliliter glass vial. Remove the organic solvent under a vacuum using a rotary evaporator, until a thin film forms in the vial.Next, transfer two milliliters of Dulbecco's phosphate buffered saline, pH 7.4 to the glass vial. Select an ultrasonic bath that can generate enough ultrasonic power to disperse the thin polymer drug film. The output power of the ultrasonic bath used in this protocol is 110 watts.Place the vial in an ultrasonic bath for three minutes at room temperate to generate micelles. Keep micelles at four degrees Celsius for short term storage, and minus 20 degrees celsius for long term storage. Once micelles are prepared, perform various characterizations to determine drug concentration in micelles, particle sizes, and in vitro anticancer activities.To determine the DOX-PA concentration and drug encapsulation efficiency, dilute 25 microliters of drug loaded micelles with 500 microliters of DMSO. Measure the absorption at 490 nanometers with a UV-VIS spectrometer, and calculate drug concentrations and encapsulation efficiency as described in the text protocol. To evaluate in vitro anticancer activity, add the diluted cell suspensions into a 96 well cell culture plate at 100 microliters per well.Incubate the cells in a cell culture incubator for 18 hours to allow cell attachment. Next, dilute a DOX DMSO solution and a DOX-PA DMSO solution with cell culture medium to obtain final drug concentrations. Keep the final DMSO concentration in all samples at 0.5%Then dilute DOX-PA micelles with cell culture medium to obtain final drug concentrations.Use the blank cell culture medium as a control. Remove the 96 well cell culture plate from the incubator and replace the cell culture medium with 100 microliters of medium containing different treatment agents. Incubate the cells in the cell culture incubator for an additional 72 hours.Next, aspirate the medium and add 100 microliters of medium containing 0.5 milligrams per milliliter of MTT. Incubate the cells in the cell culture incubator for an additional two hours. Carefully remove the medium and add 100 microliters of DMSO to dissolve formazan crystals.Measure absorbence with the microplate spectrophotometer at a wavelength of 570 nanometers and a reference wavelength of 670 nanometers. Finally, calculate the cell viability as described in the text protocol. The synthesis scheme of DOX-PA is shown here.Palmitic acid is conjugated to doxorubicin through a pH sensitive hydrozine linker. The structure of DOX-PA was further confirmed with a proton NMR spectrum. Characteristic NMR peaks from both doxorubicin and palmitic acid are observed.Letters indicate peaks, and their corresponding moiety within the structure. Blank DSPE-PEG micelles without drug appear as a transparent liquid, whereas DOX-PA DSPE-PEG micelles appear as a red liquid, which is due to the DOX-PA loaded in the micelles. The mean particle size for blank DSPE-PEG micelles is around 17.0 nanometers.The loading of DOX-PA increased micell particle size slightly, with a mean particle size for DOX-PA DSPE-PEG micelles of around 25.7 nanometers. A concentration dependent reduction in cell viability was achieved by treating DU145 cells with free doxorubicin, free DOX-PA, or DOX-PA micelles. Although free doxorubicin is more effective than free DOX-PA or DOX-PA micelles at lower concentrations, DOX-PA groups showed greater reduction in cell viability than free doxorubicin at higher concentrations.Also, there appear to be no significant difference between DOX-PA and DOX-PA micelles at both higher and lower concentrations. After watching this video, you should have a good understanding of how to prepare the micell formulations with a film dispersion method. It's important to remember that the method described can be used to prepare micell with different drugs and carrier materials.The design of carrier material is critical to improve the formulation performance. Following this procedure, the micell formulation can be further evaluated in vivo with animal tumor models to test the anticancer activity.

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