Name: methionine functionalized biocompatible block copolymers for targeted plasmid dna delivery
Uploaded: 2019-08-06T12:30:00
Description: Watch this Scientific Journal Video about Methionine Functionalized Biocompatible Block Copolymers for Targeted Plasmid DNA Delivery at JoVE.com

This research was supported by the National Key Research and Development Program of China (No. 2016YFC0905900), National Natural Science Foundation of China (Nos. 81801827, 81872365), Basic Research Program of Jiangsu Province (Natural Science Foundation, No. BK20181086), and Jiangsu Cancer Hospital Scientific Research Fund (No. ZK201605).

1. Synthesis of BNHEMA polymer (PBNHEMA)
<ol>
	<li>Dissolve 1.87 g of N, N-bis(2-hydroxyethyl)methacrylamide (BNHEMA) in 1 mL of distilled water in a polymerization bottle. 
	NOTE: The polymerization bottle is a round-bottom flask with a rubber stopper and a magnetic stirrer.</li>
	<li>Dissolve 0.03 g of 4-cyanopentanoic acid dithiobenzoate (CTP) and 0.02 g of 4,4&#8217;-azobis (4-cyanovalericacid ) (ACVA) in 0.5 mL of 1,4-dioxane in a 5 mL beaker. Then, add the CTP and ACVA solution to the polym...

<ol>
	<li>Flotte, T. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gene+and+Cell+Therapy+in+2018:+A+Look+Ahead.">Gene and Cell Therapy in 2018: A Look Ahead.</a> Human Gene Therapy. 29, 1-1 (2018).</li><li>Huang, W., 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=Nanomedicine-based+combination+anticancer+therapy+between+nucleic+acids+and+small-molecular+drugs.">Nanomedicine-based combination anticancer therapy between nucleic acids and small-molecular drugs.</a> Advanced Drug Delivery Reviews. 115, 82-97 (2017).</li><li>Wu, Y., 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=Reversing+of+multidrug+resistance+breast+cancer+by+co-delivery+of+P-gp+siRNA+and+doxorubicin+via+folic+acid-modified+core-shell+nanomicelles.">Reversing of multidrug resistance breast cancer by co-delivery of P-gp siRNA and doxorubicin via folic acid-modified core-shell nanomicelles.</a> Colloids &amp; Surfaces B Biointerfaces. 138, 60-69 (2016).</li><li>Quader, S., Kataoka, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nanomaterial-Enabled+Cancer+Therapy.">Nanomaterial-Enabled Cancer Therapy.</a> Molecular Therapy. 25, 1501-1513 (2017).</li><li>Wu, Y., 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=Multivalent+methionine-functionalized+biocompatible+block+copolymers+for+targeted+siRNA+delivery+and+subsequent+reversal+effect+on+adriamycin+resistance+in+human+breast+cancer+cell+line+MCF-7/ADR.">Multivalent methionine-functionalized biocompatible block copolymers for targeted siRNA delivery and subsequent reversal effect on adriamycin resistance in human breast cancer cell line MCF-7/ADR.</a> Journal of Gene Medicine. 19, e2969 (2017).</li><li>Szwarc, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=‘Living’+Polymers.">‘Living’ Polymers.</a> Nature. 178, 168-169 (1956).</li><li>Szwarc, M., Rembaum, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Polymerization+of+methyl+methacrylate+initiated+by+an+electron+transfer+to+the+monomer.">Polymerization of methyl methacrylate initiated by an electron transfer to the monomer.</a> Journal of Polymer Science. 22 (100), 189-191 (1956).</li><li>Mukhopadhyay, R. D., Ajayaghosh, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Living+supramolecular+polymerization.">Living supramolecular polymerization.</a> Science. 349, 241 (2015).</li><li>Ozkose, U. U., Altinkok, C., Yilmaz, O., Alpturk, O., Tasdelen, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In-situ+preparation+of+poly(2-ethyl-2-oxazoline)/clay+nanocomposites+via+living+cationic+ring-opening+polymerization.">In-situ preparation of poly(2-ethyl-2-oxazoline)/clay nanocomposites via living cationic ring-opening polymerization.</a> European Polymer Journal. 88, 586-593 (2017).</li><li>Wu, W., Wang, W., Li, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Star+polymers:+Advances+in+biomedical+applications.">Star polymers: Advances in biomedical applications.</a> Progress in Polymer Science. 46, 55-85 (2015).</li><li>Boyer, 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=Copper-Mediated+Living+Radical+Polymerization+(Atom+Transfer+Radical+Polymerization+and+Copper(0)+Mediated+Polymerization):+From+Fundamentals+to+Bioapplications.">Copper-Mediated Living Radical Polymerization (Atom Transfer Radical Polymerization and Copper(0) Mediated Polymerization): From Fundamentals to Bioapplications.</a> Chemical Reviews. 116, 1803-1949 (2016).</li><li>Keddie, D. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+guide+to+the+synthesis+of+block+copolymers+using+reversible-addition+fragmentation+chain+transfer+(RAFT)+polymerization.">A guide to the synthesis of block copolymers using reversible-addition fragmentation chain transfer (RAFT) polymerization.</a> Chemical Society Reviews. 43, 496-505 (2014).</li><li>Wu, Y., 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=Guanidinylated+3-gluconamidopropyl+methacrylamide-s-3-aminopropyl+methacrylamide+copolymer+as+siRNA+carriers+for+inhibiting+human+telomerase+reverse+transcriptase+expression.">Guanidinylated 3-gluconamidopropyl methacrylamide-s-3-aminopropyl methacrylamide copolymer as siRNA carriers for inhibiting human telomerase reverse transcriptase expression.</a> Drug Delivery. 20, 296-305 (2013).</li><li>Qin, Z., Liu, W., Guo, L., Li, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Studies+on+Guanidinated+N-3-Aminopropyl+Methacrylamide-N-2-Hydroxypropyl+Methacrylamide+Co-polymers+as+Gene+Delivery+Carrier.">Studies on Guanidinated N-3-Aminopropyl Methacrylamide-N-2-Hydroxypropyl Methacrylamide Co-polymers as Gene Delivery Carrier.</a> Journal of Biomaterials Science, Polymer Edition. 23, 1-4 (2012).</li><li>Friedman, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Applications+of+the+Ninhydrin+Reaction+for+Analysis+of+Amino+Acids,+Peptides,+and+Proteins+to+Agricultural+and+Biomedical+Sciences.">Applications of the Ninhydrin Reaction for Analysis of Amino Acids, Peptides, and Proteins to Agricultural and Biomedical Sciences.</a> Journal of Agricultural and Food Chemistry. 52, 385-406 (2004).</li><li>Habuchi, S., Yamamoto, T., Tezuka, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synthesis+of+Cyclic+Polymers+and+Characterization+of+Their+Diffusive+Motion+in+the+Melt+State+at+the+Single+Molecule+Level.">Synthesis of Cyclic Polymers and Characterization of Their Diffusive Motion in the Melt State at the Single Molecule Level.</a> Journal of Visualized Experiments. (115), 1-9 (2016).</li><li>Rao, D. A., Nguyen, D. X., Mishra, G. P., Doddapaneni, B. S., Alani, A. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Preparation+and+Characterization+of+Individual+and+Multi-drug+Loaded+Physically+Entrapped+Polymeric+Micelles.">Preparation and Characterization of Individual and Multi-drug Loaded Physically Entrapped Polymeric Micelles.</a> Journal of Visualized Experiments. 102, 1-5 (2015).</li></ol>

This study introduced a series of BNHEMA-b-APMA block polymer cationic gene carriers. These block polymers were synthesized via the reversible addition-fragmentation chain transfer (RAFT) method. The hydrophilic segment BNHEMA was introduced to improve solubility. Methionine and guanidine groups were modified to improve the target ability and transfection efficiency5. The APMA chain content increased and guanidinylation in mBG copolymer reduced the particle size of mBG/pDNA polyplexes. The particl...

In recent years, gene therapy has emerged for the therapeutic delivery of nucleic acids as drugs to treat all kinds of diseases1. The development of gene drugs including plasmid DNA (pDNA) and small interfering RNA (siRNA) relies on the stability and efficiency of the drug delivery system (DDS)2. Among all DDS, cationic polymer carriers have the advantages of good stability, low immunogenicity, and facile preparation and modification, which give cationic polymer carriers broad application prospects3,4. For practical applications in biomedicine, researchers must find a cationic polymer carrier with high efficiency, low toxicity, and good targeting ability5. Among all polymer carriers, block copolymers are one of the most widely used drug delivery systems. Block copolymers are intensively studied for their self-assembly property and abilities to form micelles, microspheres, and nanoparticles in drug delivery5. Block copolymers can be synthesized via living polymerization or click chemistry methods.
In 1956, Szwarc et al. raised the topic of living polymerization, defining it as a reaction without chain-breaking reactions6,7. Since then, multiple techniques had been developed to synthesize polymers using this method; thus, living polymerization is viewed as a milestone of polymer science8. Living polymerization can be classified into living anionic polymerization, living cationic polymerization, and reversible deactivation radical polymerization (RDRP)9. Living anionic/cationic polymerizations have a limited scope of application due to their strict reaction conditions10. Controlled/living radical polymerization (CRP) has mild reaction conditions, convenient disposition, and good yield and has thus been a major research focus in recent years11. In CRP, active propagation chains are reversibly passivated into dormant ones to reduce the concentration of free radicals and avoid the bimolecular reaction of propagating chain radicals. The addition polymerization can continue only if the inactive dormant propagating chains are reversibly animated into chain radicals. As one of the most promising forms of living radical polymerization, reversible addition-fragmentation chain transfer (RAFT) polymerization is a method applicable to yield block polymers with controlled molecular weight and structure, narrow molecular weight distribution, and carrying functional groups12. The key to successful RAFT polymerization is the effect of chain transfer agents, usually dithioesters, which possess very high chain transfer constant.
In this paper, a RAFT polymerization method was designed to prepare BNHEMA-b-APMA block polymer, taking 4,4&#8217;-azobis(4-cyanovaleric acid) (ACVA) as an initiating agent and 4-cyanopentanoic acid dithiobenzoate (CTP) as a chain transfer agent. RAFT polymerization was used twice to introduce BNHEMA into the cationic polymer carriers. Subsequently, the amine groups in the APMA chain were modified with methionine and the guanidinylation reagent 1-amidinopyrazole hydrochloride. Making the use of the positive charges of the guanidinylation reagent and methacrylamide polymer skeleton structure, the cellular uptake efficiency of the obtained block polymer carriers was improved.

<table>
<tbody>
<tr>
<td>1-hydroxybenzotriazole</td>
<td>Macklin Biochemical Co., Ltd,China</td>
<td>H810970</td>
<td>&ge;97.0%</td>
</tr>
<tr>
<td>1,4-dioxane</td>
<td>Sinopharm chemical reagent Co., Ltd, China</td>
<td>10008918</td>
<td>AR</td>
</tr>
<tr>
<td>1-amidinopyrazole Hydrochloride</td>
<td>Aladdin Co., Ltd., China</td>
<td>A107935</td>
<td>98%</td>
</tr>
<tr>
<td>1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride</td>
<td>Aladdin Co., Ltd., China</td>
<td>E106172</td>
<td>AR</td>
</tr>
<tr>
<td>4,4&#x2019;-azobis(4-cyanovaleric acid)</td>
<td>Aladdin Co., Ltd., China</td>
<td>A106307</td>
<td>Analytical reagent (AR)</td>
</tr>
<tr>
<td>4-cyano-4-(phenylcarbonothioylthio)pentanoic Acid</td>
<td>Aladdin Co., Ltd., China</td>
<td>C132316</td>
<td>&#x003E;97%(HPLC)</td>
</tr>
<tr>
<td>Acetate</td>
<td>Sinopharm chemical reagent Co., Ltd, China</td>
<td>81014818</td>
<td>AR</td>
</tr>
<tr>
<td>Acetone</td>
<td>Sinopharm chemical reagent Co., Ltd, China</td>
<td>10000418</td>
<td>AR</td>
</tr>
<tr>
<td>Agarose</td>
<td>Aladdin Co., Ltd., China</td>
<td>A118881</td>
<td>High resolution</td>
</tr>
<tr>
<td>Ascorbic acid</td>
<td>Aladdin Co., Ltd., China</td>
<td>A103533</td>
<td>AR</td>
</tr>
<tr>
<td>DMSO</td>
<td>Aladdin Co., Ltd., China</td>
<td>D103272</td>
<td>AR</td>
</tr>
<tr>
<td>Ethylene glycol</td>
<td>Aladdin Co., Ltd., China</td>
<td>E103319</td>
<td>AR</td>
</tr>
<tr>
<td>N-(3-aminopropyl)methacrylamide hydrochloride</td>
<td>Aladdin Co., Ltd., China</td>
<td>N129096</td>
<td>&ge;98.0%(HPLC)</td>
</tr>
<tr>
<td>N,N-bis(2-hydroxyethyl)methacrylamide</td>
<td>ZaiQi Bio-Tech Co.,Ltd, China</td>
<td>CF259748</td>
<td>&ge;98.0%(HPLC)</td>
</tr>
<tr>
<td>Ninhydrin</td>
<td>Aladdin Co., Ltd., China</td>
<td>N105629</td>
<td>AR</td>
</tr>
<tr>
<td>PBS buffer</td>
<td>Aladdin Co., Ltd., China</td>
<td>P196986</td>
<td>pH 7.4</td>
</tr>
<tr>
<td>Plasmid DNA</td>
<td>BIOGOT Co., Ltd, China</td>
<td>pDNA-EGFP</td>
<td>pDNA-EGFP</td>
</tr>
<tr>
<td>Plasmid DNA</td>
<td>BIOGOT Co., Ltd, China</td>
<td>Pdna</td>
<td>pDNA</td>
</tr>
<tr>
<td>Sodium carbonate decahydrate</td>
<td>Aladdin Co., Ltd., China</td>
<td>S112589</td>
<td>AR</td>
</tr>
<tr>
<td>Trimethylamine</td>
<td>Aladdin Co., Ltd., China</td>
<td>T103285</td>
<td>AR</td>
</tr>
</tbody>
</table>

methionine functionalized biocompatible block copolymers for targeted plasmid dna delivery

Reversible addition-fragmentation chain transfer (RAFT) polymerization integrates the advantages of radical polymerization and living polymerization. This work presents the preparation of methionine functionalized biocompatible block copolymers via RAFT polymerization. Firstly, N,N-bis(2-hydroxyethyl)methacrylamide-b-N-(3-aminopropyl)methacrylamide (BNHEMA-b-APMA, BA) was synthesized via RAFT polymerization using 4,4&#8217;-azobis(4-cyanovaleric acid) (ACVA) as an initiating agent and 4-cyanopentanoic acid dithiobenzoate (CTP) as the chain transfer agent. Subsequently, N,N-bis(2-hydroxyethyl)methacrylamide-b-N-(3-guanidinopropyl)methacrylamide (methionine grafted BNHEMA-b-GPMA, mBG) was prepared by modifying amine groups in APMA with methionine and guanidine groups. Three kinds of block polymers, mBG1, mBG2, and mBG3, were synthesized for comparison. A ninhydrin reaction was used to quantify the APMA content; mBG1, mBG2, and mBG3 had 21%, 37%, and 52% of APMA, respectively. Gel permeation chromatography (GPC) results showed that BA copolymers possess molecular weights of 16,200 (BA1), 20,900(BA2), and 27,200(BA3) g/mol. The plasmid DNA (pDNA) complexing ability of the obtained block copolymer gene carriers was also investigated. The charge ratios (N/P) were 8, 16, and 4 when pDNA was complexed completely with mBG1, mBG2, mBG3, respectively. When the N/P ratio of mBG/pDNA polyplexes was higher than 1, the Zeta potential of mBG was positive. At an N/P ratio between 16 and 32, the average particle size of mBG/pDNA polyplexes was between 100-200 nm. Overall, this work illustrates a simple and convenient protocol for the block copolymer carrier synthesis.

BNHEMA was fed according to the objective degree of polymerization shown in Table 1; the synthesis procedure of mBG is shown in Figure 1. Firstly, BNHEMA homopolymer was prepared via the reversible addition-fragmentation chain transfer (RAFT) method in the water-dioxane system, using 4-cyanopentanoic acid dithiobenzoate as a chain transfer agent. Secondly, PBNHEMA was used as a chain transfer agent to prepare BNHEMA-b-APMA block polymer. APMA monomer was fed accordi...

Watch this Scientific Journal Video about Methionine Functionalized Biocompatible Block Copolymers for Targeted Plasmid DNA Delivery at JoVE.com

Methionine Functionalized Biocompatible Block Copolymers for Targeted Plasmid DNA Delivery

This work presents the preparation of methionine functionalized biocompatible block copolymers (mBG) via the reversible addition-fragmentation chain transfer (RAFT) method. The plasmid DNA complexing ability of the obtained mBG and their transfection efficiency were also investigated. The RAFT method is very beneficial for polymerizing monomers containing special functional groups.

Reversible addition-fragmentation chain transfer (RAFT) polymerization integrates the advantages of radical polymerization and living polymerization. This ...

Cationic polymer drug carriers have the advantages of good stability, low immunogenicity, and facile preparation and modification. Here, we offer a rapid and simple method for its synthesis. Reversible addition-fragmentation chain transfer polymerization method is a method applicable to yield block polymers with controlled molecular weight and structure and carrying functional groups.These drug carriers can simultaneously carry different drugs to achieve the collaborate treatment of cancer, inflammation, and other diseases. IFT polymerization is a classic method, and this protocol gives an example of its application in gene therapy. The key to the success for synthesis of this polymer is to precisely control the reaction temperature.It is more advisable to use an oil bath than a water bath. To begin this procedure, obtain a round-bottom flask with a rubber stopper and a magnetic stirrer to be used as the polymerization bottle. Dissolve 1.87 grams of bis-hydroxy HEMA in one milliliter of distilled water in the polymerization bottle.In a five-milliliter beaker, dissolve 0.03 grams of CTP and 0.02 grams of ACVA in 0.5 milliliters of 1, 4-dioxane. Add this mixture to the polymerization bottle. Then, use a condensate trap to freeze the solution in the polymerization bottle.Fix the bottle to the iron support, and use a conduit tripped with a needle to vacuumize and inject nitrogen into the reaction mixture. Then, seal the polymerization bottle, and thaw the solution at room temperature for 30 minutes. Repeat this freeze-pump-thaw cycle three times.After this, place the bottle into an oil bath at 70 degrees Celsius and let the solution react for 24 hours under the nitrogen atmosphere. The next day, chill the polymerization bottle at zero degrees Celsius and open the rubber stopper to terminate the polymerization reaction. Next, precool acetone in a refrigerator at negative 20 degrees Celsius for two hours, and mix it with the reaction solution in the polymerization bottle at a ratio of 50 to one.Centrifuge this mixture at 8, 200 times g for 10 minutes to remove the acetone and collect the precipitate. To purify the synthesized poly bis-hydroxy HEMA, dissolve the collected precipitate in two milliliters of pure water. Then, mix it with 100 milliliters of precooled acetone at a ratio of one to 50.Centrifuge the solution at 8, 200 times g for 10 minutes to collect the precipitate. Repeat this purification process of dissolving, mixing, and centrifuging the precipitate three times. First, dissolve 0.96 grams of APMA and 0.93 grams of the purified poly bis-hydroxy HEMA in five milliliters of distilled water in a 10-milliliter beaker.Dissolve 0.01 grams of ACVA in 0.5 milliliters of 1, 4-dioxane, and add this to the APMA and poly bis-hydroxy HEMA solution. Transfer this mixture to a polymerization bottle, and ventilate with dry nitrogen for one hour. Then, put the polymerization bottle into an oil bath at 70 degrees Celsius, and let it react for 24 hours under the nitrogen atmosphere.The next day, chill the polymerization bottle at zero degrees Celsius and open the rubber stopper to terminate the polymerization process solution. To begin, seed MCF-7 cells into the wells of a six-well plate at a density of 20, 000 cells per well. Culture the cells in a humidified incubator at 37 degrees Celsius with 5%carbon dioxide for 12 hours.After this, replace the culture medium with the fresh culture medium containing cationic polymer and pDNA polyplex polyplexes of different ratio of nitrogen-to-phosphorus ratios. Culture the cells for six hours, and then replace the medium with two milliliters of fresh RPMI 1640 medium. Continue culturing for 48 hours.Then, collect the cells, and use a flow cytometer to detect the green fluorescence. In this study, methionine-functionalized biocompatible block copolymers are prepared via the reversible addition-fragmentation chain transfer method, and the plasmid DNA complexing ability of the obtained mBG and their transfection efficiency is investigated. The average particle size and zeta potential of mBG/pDNA polyplexes are 124 nanometers and plus 15.7 millivolts, respectively, at an N-to-P ratio of 16.Electrophoretic retardation reveals that pDNA with an N-to-P ratio of zero can move without restraint in the agarose gel and is observed as a stripe in the gel imager. When pDNA is complexed with mBG, the movement of pDNA is retarded, and subsequently, the brightness of the band is reduced. This shows that mBG can completely complex the pDNA when the N to P is higher than four.The cytotoxicity of the mBG/pDNA polyplexes is then measured using the standard MTT assay These results show that mBG/pDNA polyplexes have cytotoxicity than PEI/pDNA polyplexes at the N-to-P ratios of four, eight, 16, and 32. As can also be seen, the cytotoxicity of the mBG/pDNA polyplexes increases with increased N-to-P ratio. This increased cytotoxicity is a result of the positively charged GPMA component.The N-to-P ratio used in the pDNA transfection experiment is selected according to the cytotoxicity results. The transfection abilities of mBG1, mBG2, and mBG3 are compared by measuring the GFP fluorescence intensity, and the results showed that mBG3 is the optimal gene carrier. It is important to exhaust air from the silt round-bottom flask and maintain the reaction temperature.The obtained polymer drug carriers can be applied to the co-delivery of chemotherapy drugs and gene drugs to synergistically treat drug-resistant cancer. The molecular mechanism of combination of gene drugs and chemotherapeutic drugs can be further explored for the treatment of drug-resistant tumors. Acetone is rated as low toxic for its acute toxicity.Keys, inhalation or contact with eyes or skin should be avoided. Avoid to the risk of scalding during the heating procedure.

methionine-functionalized-biocompatible-block-copolymers-for-targeted

Research

JoVE Journal

Chemistry

Microwave-assisted Intramolecular Dehydrogenative Diels-Alder Reactions for the Synthesis of Functionalized Naphthalenes/Solvatochromic Dyes

Functionalized naphthalenes have applications in a variety of research fields ranging from the synthesis of natural or biologically active molecules to the preparation of new organic dyes. Although numerous strategies have been reported to access naphthalene scaffolds, many procedures still present limitations in terms of incorporating functionality, which in turn narrows the range of available substrates. The development of versatile methods for direct access to substituted naphthalenes is therefore highly desirable.
The Diels-Alder (DA) cycloaddition reaction is a powerful and attractive method for the formation of saturated and unsaturated ring systems from readily available starting materials. A new microwave-assisted intramolecular dehydrogenative DA reaction of styrenyl derivatives described herein generates a variety of functionalized cyclopenta[b]naphthalenes that could not be prepared using existing synthetic methods. When compared to conventional heating, microwave irradiation accelerates reaction rates, enhances yields, and limits the formation of undesired byproducts.
The utility of this protocol is further demonstrated by the conversion of a DA cycloadduct into a novel solvatochromic fluorescent dye via a Buchwald-Hartwig palladium-catalyzed cross-coupling reaction. Fluorescence spectroscopy, as an informative and sensitive analytical technique, plays a key role in research fields including environmental science, medicine, pharmacology, and cellular biology. Access to a variety of new organic fluorophores provided by the microwave-assisted dehydrogenative DA reaction allows for further advancement in these fields.

Microwave-assisted intramolecular dehydrogenative Diels-Alder (DA) reactions provide concise access to functionalized cyclopenta[b]naphthalene building blocks. The utility of this methodology is demonstrated by one-step conversion of the dehydrogenative DA cycloadducts into novel solvatochromic fluorescent dyes via Buchwald-Hartwig palladium-catalyzed cross-coupling reactions.

Functionalized naphthalenes have applications in a variety of research fields ranging from the synthesis of natural or biologically active molecules to ...

Synthesis and Characterization of Functionalized Metal-organic Frameworks

Metal-organic frameworks have attracted extraordinary amounts of research attention, as they are attractive candidates for numerous industrial and technological applications. Their signature property is their ultrahigh porosity, which however imparts a series of challenges when it comes to both constructing them and working with them. Securing desired MOF chemical and physical functionality by linker/node assembly into a highly porous framework of choice can pose difficulties, as less porous and more thermodynamically stable congeners (e.g., other crystalline polymorphs, catenated analogues) are often preferentially obtained by conventional synthesis methods. Once the desired product is obtained, its characterization often requires specialized techniques that address complications potentially arising from, for example, guest-molecule loss or preferential orientation of microcrystallites. Finally, accessing the large voids inside the MOFs for use in applications that involve gases can be problematic, as frameworks may be subject to collapse during removal of solvent molecules (remnants of solvothermal synthesis). In this paper, we describe synthesis and characterization methods routinely utilized in our lab either to solve or circumvent these issues. The methods include solvent-assisted linker exchange, powder X-ray diffraction in capillaries, and materials activation (cavity evacuation) by supercritical CO2 drying. Finally, we provide a protocol for determining a suitable pressure region for applying the Brunauer-Emmett-Teller analysis to nitrogen isotherms, so as to estimate surface area of MOFs with good accuracy.

Synthesis, activation, and characterization of intentionally designed metal-organic framework materials is challenging, especially when building blocks are incompatible or unwanted polymorphs are thermodynamically favored over desired forms. We describe how applications of solvent-assisted linker exchange, powder X-ray diffraction in capillaries and activation via supercritical CO2 drying, can address some of these challenges.

Metal-organic frameworks have attracted extraordinary amounts of research attention, as they are attractive candidates for numerous industrial and ...

Functionalization of Single-walled Carbon Nanotubes with Thermo-reversible Block Copolymers and Characterization by Small-angle Neutron Scattering

We demonstrate a protocol for single-walled carbon nanotube functionalization using thermo-sensitive PEO-PPO-PEO triblock copolymers in an aqueous solution. In a carbon nanotube/PEO105-PPO70-PEO105 (poloxamer 407) aqueous solution, the amphiphilic poloxamer 407 adsorbs onto the carbon nanotube surfaces and self-assembles into continuous layers, driven by intermolecular interactions between constituent molecules. The addition of 5-methylsalicylic acid changes the self-assembled structure from spherical-micellar to a cylindrical morphology. The fabricated poloxamer 407/carbon nanotube hybrid particles exhibit thermo-responsive structural features so that the density and thickness of poloxamer 407 layers are also reversibly controllable by varying temperature. The detailed structural properties of the poloxamer 407/carbon nanotube particles in suspension can be characterized by small-angle neutron scattering experiments and model fit analyses. The distinct curve shapes of the scattering intensities depending on temperature control or addition of aromatic additives are well described by a modified core-shell cylinder model consisting of a carbon nanotube core cylinder, a hydrophobic shell, and a hydrated polymer layer. This method can provide a simple but efficient way for the fabrication and in-situ characterization of carbon nanotube-based nano particles with a structure-tunable encapsulation.

A method for the functionalization of carbon nanotubes with structure-tunable polymeric encapsulation layers and structural characterization using small-angle neutron scattering is presented.

We demonstrate a protocol for single-walled carbon nanotube functionalization using thermo-sensitive PEO-PPO-PEO triblock copolymers in an aqueous ...

Self-assembling Morphologies Obtained from Helical Polycarbodiimide Copolymers and Their Triazole Derivatives

A facile method for the preparation of polycarbodiimide-based secondary structures (e.g., nano-rings, &#34;craters,&#34; fibers, looped fibers, fibrous networks, ribbons, worm-like aggregates, toroidal structures, and spherical particles) is described. These aggregates are morphologically influenced by extensive hydrophobic side chain-side chain interactions of the singular polycarbodiimide strands, as inferred by atomic force microscopy (AFM) and scanning electron microscopy (SEM) techniques. Polycarbodiimide-g-polystyrene copolymers (PS-PCDs) were prepared by a combination of synthetic methods, including coordination-insertion polymerization, copper(I)-catalyzed azide alkyne cycloaddition (CuAAC) &#34;click&#34; chemistry, and atom transfer radical polymerization (ATRP). PS-PCDs were found to form specific toroidal architectures at low concentrations in CHCl3. To determine the influence of a more polar solvent medium (i.e., THF and THF/EtOH) on polymer aggregation behavior, a number of representative PS-PCD composites have been tested to show discrete concentration-dependent spherical particles. These fundamental studies are of practical interest to the development of experimental procedures for desirable architectures by directed self-assembly in thin film. These architectures may be exploited as drug carriers, whereas other morphological findings represent certain interest in the area of novel functional materials.

Here, we present a protocol to prepare and visualize secondary structures (e.g., fibers, toroidal architectures, and nano-spheres) derived from helical polycarbodiimides. The morphology characterized by both atomic force microscopy (AFM) and scanning electron microscopy (SEM) was shown to depend on molecular structure, concentration, and the solvent of choice.

A facile method for the preparation of polycarbodiimide-based secondary structures (e.g., nano-rings, &#34;craters,&#34; fibers, looped fibers, fibrous ...

Synthesis of a Thiol Building Block for the Crystallization of a Semiconducting Gyroidal Metal-sulfur Framework

We present a method for preparing thioester molecules as the masked form of the thiol linkers and their utilization for accessing a semiconducting and porous metal-dithiolene network in the highly ordered single crystalline state. Unlike the highly reactive free-standing thiols, which tend to decompose and complicate the crystallization of metal-thiolate open frameworks, the thioester reacts in situ to provide the thiol species, serving to mitigate the reaction between the mercaptan units and the metal centers, and to improve crystallization consequently. Specifically, the thioester was synthesized in a one-pot procedure: an aromatic bromide (hexabromotriphenylene) reacted with excess sodium thiomethoxide under vigorous conditions to first form the thioether intermediate product. The thioether was then demethylated by the excess thiomethoxide to provide the thiolate anion that was acylated to form the thioester product. The thioester was conveniently purified by standard column chromatography, and then used directly in the framework synthesis, wherein NaOH and ethylenediamine serve to revert in situ the thioester to the thiol linker for assembling the single-crystalline Pb(II)-dithiolene network. Compared with other methods for thiol synthesis (e.g., by cleaving alkyl thioether using sodium metal and liquid ammonia), the thioester synthesis here uses simple conditions and economical reagents. Moreover, the thioester product is stable and can be conveniently handled and stored. More importantly, in contrast to the generic difficulty in accessing crystalline metal-thiolate open frameworks, we demonstrate that using the thioester for in situ formation of the thiol linker greatly improves the crystallinity of the solid-state product. We intend to encourage broader research efforts on the technologically important metal-sulfur frameworks by disclosing the synthetic protocol for the thioester as well as the crystalline framework solid.

Here, we present a one-pot, transition-metal-free synthesis of thiols and thioesters from aromatic halides and sodium thiomethoxide, followed by the preparation of single crystals of a metal-dithiolene network using thiol species generated in situ from the more stable and tractable thioester.

We present a method for preparing thioester molecules as the masked form of the thiol linkers and their utilization for accessing a semiconducting and ...

Preparation of Poly(pentafluorophenyl acrylate) Functionalized SiO2 Beads for Protein Purification

We demonstrate a simple method to prepare poly(pentafluorophenyl acrylate) (poly(PFPA)) grafted silica beads for antibody immobilization and subsequent immunoprecipitation (IP) application. The poly(PFPA) grafted surface is prepared via a simple two-step process. In the first step, 3-aminopropyltrimethoxysilane (APTMS) is deposited as a linker molecule onto the silica surface. In the second step, poly(PFPA) homopolymer, synthesized via the reversible addition and fragmentation chain transfer (RAFT) polymerization, is grafted to the linker molecule through the exchange reaction between the pentafluorophenyl (PFP) units on the polymer and the amine groups on APTMS. The deposition of APTMS and poly(PFPA) on the silica particles are confirmed by X-ray photoelectron spectroscopy (XPS), as well as monitored by the particle size change measured via dynamic light scattering (DLS). To improve the surface hydrophilicity of the beads, partial substitution of poly(PFPA) with amine-functionalized poly(ethylene glycol) (amino-PEG) is also performed. The PEG-substituted poly(PFPA) grafted silica beads are then immobilized with antibodies for IP application. For demonstration, an antibody against protein kinase RNA-activated (PKR) is employed, and IP efficiency is determined by Western blotting. The analysis results show that the antibody immobilized beads can indeed be used to enrich PKR while non-specific protein interactions are minimal.

Preparation of Polypentafluorophenyl acrylate Functionalized SiO2 Beads for Protein Purification

A protocol for the preparation of poly(pentafluorophenyl acrylate) (poly(PFPA)) grafted silica beads is presented. The poly(PFPA) functionalized surface is then immobilized with antibodies and used successfully for the protein separation through immunoprecipitation.

We demonstrate a simple method to prepare poly(pentafluorophenyl acrylate) (poly(PFPA)) grafted silica beads for antibody immobilization and subsequent ...

Synthesis of Monodisperse Cylindrical Nanoparticles via Crystallization-driven Self-assembly of Biodegradable Block Copolymers

The production of monodisperse cylindrical micelles is a significant challenge in polymer chemistry. Most cylindrical constructs formed from diblock copolymers are produced by one of three techniques: thin film rehydration, solvent switching or polymerization-induced self-assembly, and produce only flexible, polydisperse cylinders. Crystallization-driven self-assembly (CDSA) is a method which can produce cylinders with these properties, by stabilizing structures of a lower curvature due to the formation of a crystalline core. However, the living polymerization techniques by which most core-forming blocks are formed are not trivial processes and the CDSA process may yield unsatisfactory results if carried out incorrectly. Here, the synthesis of cylindrical nanoparticles from simple reagents is shown. The drying and purification of reagents prior to a ring-opening polymerization of &#949;-caprolactone catalyzed by diphenyl phosphate is described. This polymer is then chain extended by methyl methacrylate (MMA) followed by N,N-dimethyl acrylamide (DMA) using reversible addition&#8722;fragmentation chain-transfer (RAFT) polymerization, affording a triblock copolymer that can undergo CDSA in ethanol. The living CDSA process is outlined, the results of which yield cylindrical nanoparticles up to 500 nm in length and a length dispersity as low as 1.05. It is anticipated that these protocols will allow others to produce cylindrical nanostructures and elevate the field of CDSA in the future.

Crystallization-driven self-assembly (CDSA) displays the unique ability to fabricate cylindrical nanostructures of narrow length distributions. The organocatalyzed ring-opening polymerization of &#949;-caprolactone and subsequent chain extensions of methyl methacrylate and N,N-dimethyl acrylamide are demonstrated. A living CDSA protocol that produces monodisperse cylinders up to 500 nm in length is outlined.

The production of monodisperse cylindrical micelles is a significant challenge in polymer chemistry. Most cylindrical constructs formed from diblock ...

Efficient Synthesis of All-Carbon Quaternary Centers via the Conjugate Addition of Functionalized Monoorganozinc Bromides

The conjugate addition of organometallic reagents to &#945;,&#946;-unsaturated carbonyls represents an important method to generate C&#8211;C bonds in the preparation of all-carbon quaternary centers. Though conjugate additions of organometallic reagents are typically performed utilizing highly reactive organolithium or Grignard reagents, organozinc reagents have garnered attention for their enhanced chemoselectivity and mild reactivity. Despite numerous recent advances with more reactive diorganozinc and mixed diorganozinc reagents, the generation of all-carbon quaternary centers via the conjugate addition of functionalized monoorganozinc reagents remains a challenge. This protocol details a convenient and mild &#8220;one-pot&#8221; preparation and copper mediated conjugate addition of functionalized monoorganozinc bromides to cyclic &#945;,&#946;-unsaturated carbonyls to afford a broad scope of all-carbon quaternary centers in generally excellent yield and diastereoselectivity. Key to the development of this technology is the utilization of DMA as a reaction solvent with TMSCl as a Lewis acid. Notable advantages to this methodology include the operational simplicity of the organozinc reagent preparation afforded by the utilization of DMA as a solvent, as well as an efficient conjugate addition mediated by various Cu(I) and Cu(II) salts. Moreover, an intermediate silyl enol ether can be isolated utilizing a modified workup procedure. The substrate scope is limited to cyclic unsaturated ketones, and the conjugate addition is impeded by stabilized (e.g., allyl, enolate, homoenolate) and sterically encumbered (e.g., neopentyl, o-aryl) monoorganozinc reagents. Conjugate additions to five- and seven-membered rings were effective, albeit in lower yields compared with six-membered ring substrates.

A simple and practical protocol for the efficient conjugate addition of functionalized monoorganozinc bromides to cyclic &#945;,&#946;-unsaturated carbonyls to furnish all-carbon quaternary centers was developed.

The conjugate addition of organometallic reagents to &#945;,&#946;-unsaturated carbonyls represents an important method to generate C&#8211;C bonds in the ...

18F-Labeling of Radiotracers Functionalized with a Silicon Fluoride Acceptor (SiFA) for Positron Emission Tomography

The para-substituted di-tert-butylfluorosilylbenzene structural motif known as the silicon-fluoride acceptor (SiFA) is a useful tag in the radiochemist&#39;s toolkit for incorporating radioactive [18F]fluoride into tracers for use in positron emission tomography. In comparison to conventional radiolabeling strategies, isotopic exchange of fluorine-19 from SiFA with [18F]fluoride is carried out at room temperature and requires minimal reaction participants. The formation of by-products is thus negligible, and purification is greatly simplified. However, while the precursor molecule used for labeling and the final radiolabeled product are isotopically discrete, they are chemically identical and are thus inseparable during purification procedures. The SiFA tag is also susceptible to degradation under the basic conditions arising from the processing and drying of [18F]fluoride. The &#39;4 drop method&#39;, wherein only the first 4 drops of eluted [18F]fluoride are used from the solid-phase extraction, reduces the amount of base in the reaction, facilitates lower molar amounts of precursor, and reduces degradation.

18F-Labeling of Radiotracers Functionalized with a Silicon Fluoride Acceptor SiFA for Positron Emission Tomography

The synthesis of fluorine-18 (18F) labeled radiopharmaceuticals for positron emission tomography typically requires months of experience. When incorporated into a radiotracer, the silicon-fluoride acceptor (SiFA) motif enables a simple 18F-labeling protocol that is independent of costly equipment and preparatory training, while reducing precursor quantity needed and utilizing milder reaction conditions.

The para-substituted di-tert-butylfluorosilylbenzene structural motif known as the silicon-fluoride acceptor (SiFA) is a useful tag in the ...

Synthesis of Aptamer-PEI-g-PEG Modified Gold Nanoparticles Loaded with Doxorubicin for Targeted Drug Delivery

Due to drug resistance and toxicity in healthy cells, use of doxorubicin (DOX) has been limited in clinical cancer therapy. This protocol describes the designing of poly(ethylenimine) grafted with polyethylene glycol (PEI-g-PEG) copolymer functionalized gold nanoparticles (AuNPs) with loaded aptamer (AS1411) and DOX through amide reactions. AS1411 is specifically bonded with targeted nucleolin receptors on cancer cells so that DOX targets cancer cells instead of healthy cells. First, PEG is carboxylated, then grafted to branched PEI to obtain a PEI-g-PEG copolymer, which is confirmed by 1H NMR analysis. Next, PEI-g-PEG copolymer coated gold nanoparticles (PEI-g-PEG@AuNPs) are synthesized, and DOX and AS1411 are covalently bonded to AuNPs gradually via amide reactions. The diameter of the prepared AS1411-g-DOX-g-PEI-g-PEG@AuNPs is ~39.9 nm, with a zeta potential of -29.3 mV, indicating that the nanoparticles are stable in water and cell medium. Cell cytotoxicity assays show that the newly designed DOX loaded AuNPs are able to kill cancer cells (A549). This synthesis demonstrates the delicate arrangement of PEI-g-PEG copolymers, aptamers, and DOX on AuNPs that are achieved by sequential amide reactions. Such aptamer-PEI-g-PEG functionalized AuNPs provide a promising platform for targeted drug delivery in cancer therapy.

In this protocol, doxorubicin-loaded AS1411-g-PEI-g-PEG modified gold nanoparticles are synthesized via three-step amide reactions. Then, doxorubicin is loaded and delivered to target cancer cells for cancer therapy.

Due to drug resistance and toxicity in healthy cells, use of doxorubicin (DOX) has been limited in clinical cancer therapy. This protocol describes the ...