Name: synthesis of aptamer-pei-g-peg modified gold nanoparticles loaded with doxorubicin for targeted drug delivery
Uploaded: 2020-06-23T13:30:00
Description: Watch this Scientific Journal Video about Synthesis of Aptamer-PEI-g-PEG Modified Gold Nanoparticles Loaded with Doxorubicin for Targeted Drug Delivery at JoVE.com

This research was funded by the National Natural Science Foundation of China (31700840); the Key Scientific Research Project of Henan Province (18B430013, 18A150049). This research was supported by the Nanhu Scholars Program for Young Scholars of XYNU. The authors would like to thank bachelor student Zebo Qu from the College of Life Sciences in XYNU for his helpful works. The authors would like to acknowledge the Analysis &#38; Testing Center of XYNU for the use of their equipment.

CAUTION: Make sure to consult all relevant material safety data sheets (MSDS) before using all chemicals. Several of the chemicals used for preparing copolymer and nanoparticles are acutely toxic. Nanoparticles also have potential hazards. Make sure to use all appropriate safety practices and personal protective equipment, including gloves, lab coat, hoods, full-length pants, and close-toed shoes.
1. Synthesis of double-carboxyl polyethylene glycol (CT-PEG)33
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M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gold+nanoparticles+in+delivery+applications.">Gold nanoparticles in delivery applications.</a> Advanced Drug Delivery Reviews. 60 (11), 1307-1315 (2008).</li><li>Vandghanooni, S., Eskandani, M., Barar, J., Omidi, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Antisense+LNA-loaded+nanoparticles+of+star-shaped+glucose-core+PCL-PEG+copolymer+for+enhanced+inhibition+of+oncomiR-214+and+nucleolin-mediated+therapy+of+cisplatin-resistant+ovarian+cancer+cells.">Antisense LNA-loaded nanoparticles of star-shaped glucose-core PCL-PEG copolymer for enhanced inhibition of oncomiR-214 and nucleolin-mediated therapy of cisplatin-resistant ovarian cancer cells.</a> International Journal of Pharmaceutics. 573, 118729 (2020).</li><li>Andghanooni, S., Eskandani, M., Barar, J., Omidi, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=AS1411+aptamer-decorated+cisplatin-loaded+poly(lactic-co-glycolic+acid)+nanoparticles+for+targeted+therapy+of+miR-21-inhibited+ovarian+cancer+cells.">AS1411 aptamer-decorated cisplatin-loaded poly(lactic-co-glycolic acid) nanoparticles for targeted therapy of miR-21-inhibited ovarian cancer cells.</a> Nanomedicine. 13 (21), 2729-2758 (2018).</li><li>Palmieri, D., 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=Human+anti-nucleolin+recombinant+immunoagent+for+cancer+therapy.">Human anti-nucleolin recombinant immunoagent for cancer therapy.</a> Proceedings of the National Academy of Sciences of the United States of America. 112 (30), 9418-9423 (2015).</li><li>Pichiorri, F., 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=In+vivo+NCL+targeting+affects+breast+cancer+aggressiveness+through+miRNA+regulation.">In vivo NCL targeting affects breast cancer aggressiveness through miRNA regulation.</a> Journal of Experimental Medicine. 210 (5), 951-968 (2013).</li><li>Hou, S., McCauley, L. 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X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synthesis+and+erosion+properties+of+PEG-containing+polyanhydrides.">Synthesis and erosion properties of PEG-containing polyanhydrides.</a> Macromolecular Bioscience. 7 (5), 620-628 (2007).</li><li>Nie, L., 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=Injectable+Vaginal+Hydrogels+as+a+Multi-Drug+Carrier+for+Contraception.">Injectable Vaginal Hydrogels as a Multi-Drug Carrier for Contraception.</a> Applied Sciences. 9 (8), 1638 (2019).</li><li>Zou, P., Suo, J., Nie, L., Feng, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Temperature-responsive+biodegradable+star-shaped+block+copolymers+for+vaginal+gels.">Temperature-responsive biodegradable star-shaped block copolymers for vaginal gels.</a> Journal of Materials Chemistry. 22 (13), 6316-6326 (2012).</li><li>Etrych, T., &#352;ubr, V., Laga, R., &#344;&#237;hov&#225;, B., Ulbrich, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Polymer+conjugates+of+doxorubicin+bound+through+an+amide+and+hydrazone+bond:+Impact+of+the+carrier+structure+onto+synergistic+action+in+the+treatment+of+solid+tumours.">Polymer conjugates of doxorubicin bound through an amide and hydrazone bond: Impact of the carrier structure onto synergistic action in the treatment of solid tumours.</a> European Journal of Pharmaceutical Sciences. 58, 1-12 (2014).</li><li>Safari, F., Tamaddon, A. 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The 1H NMR spectrum (Figure 2) confirm the successful synthesis of CT-PEG copolymer and PEI-g-PEG copolymer. The molecular weights of PEG and PEI were 1,000 and 1,200, respectively. Additionally, the EDC/NHS catalytic system was used to synthesize PEI-g-PEG copolymer via amide reactions. It should be noted that if the molecular weights of PEG and PEI changed for synthesizing PEI-g-PEG copolymer, then the reaction time and catalytic system needs to be reevaluated. Also, the reactio...

Being the major public health problem worldwide, cancer is widely characterized as having a low cure rate, high recurrence rate, and high mortality rate1,2. Current conventional anti-cancer methods include surgery, chemotherapy, and radiotherapy3, among which chemotherapy is the primary treatment for cancer patients in the clinic4. Clinical used anticancer drugs mainly include paclitaxel (PTX)5 and doxorubicin (DOX)6,7. DOX, an antineoplastic drug, has been broadly applied in clinical chemotherapy, due to the advantages of cancer cytotoxicity and inhibition of cancer cell proliferation8,9. However, DOX causes cardiotoxicity10,11, and the short half-life of DOX restricts its application in the clinic12. Therefore, degradable drug carriers are needed to load DOX and subequently release in a controlled fashion to a targeted area.
Nanoparticles have been widely used in targeted drug delivery systems and have several advantages in cancer treatment (i.e., sizeable surface-to-volume ratio, small size, ability to encapsulate various drugs, and tunable surface chemistry, etc.)13,14,15. In particular, gold nanoparticles (AuNPs) have been widely used in biological and biomedical applications, such as photothermal cancer therapy16,17. The unique properties of AuNPs, such as facile synthesis and general surface functionalization, have excellent prospects in the clinical field of cancer therapy18. Also, AuNPs have been used to identify drug delivery strategies, diagnose tumors, and overcome resistance in many studies19,20.
Notwithstanding, AuNPs need to be further tailored to overcome drug resistance via high local release at tumor lesions through enhanced permeation and retention (EPR), such as the targeting and accessibility properties. Polymer functionalized AuNPs have exhibited unique advantages, such as improved water solubility of hydrophobic anticancer drugs and prolonged circulation time21,22. Various biocompatible polymers have been used for AuNP coatings, such as polyethylene glycol (PEG), polyethyleneimine (PEI), hyaluronic acid, heparin, and xanthan gum. Then the stability, as well as the payload, of AuNPs is improved well23. Specifically, PEI is a highly branched polymer that is composed of many repeating units of primary, secondary, and tertiary amines24. PEI has excellent solubility, low viscosity, and a high degree of functionality, which is suitable for coating on AuNPs.
On the other hand, anti-cancer drugs need to be delivered to cancer cells directly with improved loading efficiency, and with lower toxicity for treating primary and advanced metastatic tumors25. Targeted ligands have great potential for anti-cancer drug targeted delivery systems26. Its selectivity for target molecule binding confers anti-cancer drug targeting specificity and increases drug enrichment in diseased tissues27. More ligands include antibodies, polypeptides, and small molecules. Compared to other ligands, nucleic acid aptamers can be synthesized in vitro and are easy to modify. AS1411 is an unmodified 26 bp phosphodiester oligonucleotide that forms a stable dimeric G-tetramer structure to specifically bind to an overexpressed target nuclear protein receptor on cancer cells28,29,30. AS1411 inhibits the proliferation of many cancer cells but does not affect the growth of healthy cells31,32. As a result, AS1411 has been used to fabricate an ideal targeted drug delivery system.
In this study, a PEI-g-PEG copolymer is synthesized via an amide reaction, then PEI-g-PEG copolymer coated gold nanoparticles (PEI-g-PEG@AuNPs) are fabricated. Additionally, DOX and AS1411 are sequentially linked to the prepared PEI-g-PEG@AuNPs, as shown in Figure 1. This detailed protocol is intended to help researchers avoid many of the common pitfalls associated with the fabrication of new PEI-g-PEG@AuNPs loaded with DOX and AS1411.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>4-Dimethylaminopyridine</td>
			<td>Macklin</td>
			<td>D807273</td>
			<td></td>
		</tr>
		<tr>
			<td>A549 cell</td>
			<td></td>
			<td>ATCC CCL-185TM</td>
			<td></td>
		</tr>
		<tr>
			<td>AS1411</td>
			<td>BBI Life Sciences Corporation</td>
			<td></td>
			<td>5&#39;-d (TTTGGTGGTGGTGGTTGTGGTGGTGGTGG) FL-AS1411 (fluorophore-labeled AS1411)</td>
		</tr>
		<tr>
			<td>Anhydrous Tetrahydrofuran (THF)</td>
			<td>SinoPharm Chemical Reagent Co., Ltd</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Cell counting kit-8 (CCK-8)</td>
			<td>Sigma Aldrich</td>
			<td>96992-500TESTS-F</td>
			<td></td>
		</tr>
		<tr>
			<td>Dichloromethane</td>
			<td>Traditional Chinese medicine</td>
			<td>80047318</td>
			<td></td>
		</tr>
		<tr>
			<td>Diethyl ether (Et2O)</td>
			<td>SinoPharm Chemical Reagent Co., Ltd</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Dimethyl sulfoxide</td>
			<td>Macklin</td>
			<td>D806645</td>
			<td></td>
		</tr>
		<tr>
			<td>Dulbecco&#39;s modified Eagle&#39;s medium (DMEM)</td>
			<td>Sigma Aldrich</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Doxorubicin hydrochloride</td>
			<td>Rhawn</td>
			<td>R017518</td>
			<td></td>
		</tr>
		<tr>
			<td>Ether absolute</td>
			<td>Traditional Chinese medicine</td>
			<td>80059618</td>
			<td></td>
		</tr>
		<tr>
			<td>Field Emission Transmission Electron Microscope</td>
			<td>FEI Company</td>
			<td>Tecnai G2 F 20</td>
			<td></td>
		</tr>
		<tr>
			<td>Gold(III) chloride trihydrate</td>
			<td>Rhawn</td>
			<td>R016035</td>
			<td></td>
		</tr>
		<tr>
			<td>Laser Particle-size Instrument</td>
			<td>Malvern Instruments Ltd</td>
			<td>ZetasizerNanoZS/Masterszer3000E</td>
			<td></td>
		</tr>
		<tr>
			<td>Microplate Reader</td>
			<td>Molecular Devices</td>
			<td>SpectraMax 190</td>
			<td></td>
		</tr>
		<tr>
			<td>N-(3-Dimethylaminopropyl)-N&#39;-ethylcarbodiimide hydrochloride</td>
			<td>Macklin</td>
			<td>N808856</td>
			<td></td>
		</tr>
		<tr>
			<td>N-Hydroxysuccinimide</td>
			<td>Macklin</td>
			<td>H6231</td>
			<td></td>
		</tr>
		<tr>
			<td>NMR software</td>
			<td>Delta 5.2.1</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Nuclear Magnetic Resonance Spectrometer</td>
			<td>JEOL</td>
			<td>JNM-ECZ600R/S3</td>
			<td></td>
		</tr>
		<tr>
			<td>Origin 8.5</td>
			<td>OriginLab</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Penicillin</td>
			<td>Sigma Aldrich</td>
			<td>V900929-100ML</td>
			<td></td>
		</tr>
		<tr>
			<td>Phosphate-buffered saline</td>
			<td>Sigma Aldrich</td>
			<td>P4417-100TAB</td>
			<td></td>
		</tr>
		<tr>
			<td>Poly(ethylene glycol)</td>
			<td>Sigma Aldrich</td>
			<td>81188</td>
			<td>BioUltra, average Mn ~ 1000</td>
		</tr>
		<tr>
			<td>Poly (ethyleneimine) solution</td>
			<td>Sigma Aldrich</td>
			<td>482595</td>
			<td>average Mn ~ 1200, 50 wt.% in H2O</td>
		</tr>
		<tr>
			<td>Sodium borohydride, powder</td>
			<td>Acros</td>
			<td>C18930</td>
			<td></td>
		</tr>
		<tr>
			<td>Streptomycin</td>
			<td>Sigma Aldrich</td>
			<td>85886-10ML</td>
			<td></td>
		</tr>
		<tr>
			<td>Succinic anhydride</td>
			<td>Traditional Chinese medicine</td>
			<td>30171826</td>
			<td></td>
		</tr>
		<tr>
			<td>Tetrahydrofuran</td>
			<td>Traditional Chinese medicine</td>
			<td>40058161</td>
			<td></td>
		</tr>
		<tr>
			<td>Triethylamine</td>
			<td>Traditional Chinese medicine</td>
			<td>80134318</td>
			<td></td>
		</tr>
		<tr>
			<td>UV/VIS/NIR Spectrometer</td>
			<td>Lambda950</td>
			<td>Lambda950</td>
			<td></td>
		</tr>
		<tr>
			<td>X-ray Photoelectron Spectrometer</td>
			<td>Thermo&#8194;Fisher&#8194;Scientific</td>
			<td>K-ALPHA 0.5EV</td>
			<td></td>
		</tr>
	</tbody>
</table>

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.

1H NMR spectroscopy was used to confirm the successful synthesis of CT-PEG polymer and PEI-g-PEG copolymers (Figure 2). Figure 2a shows that the methylene proton signal at &#948; = 3.61 ppm and carboxyl proton signal at &#948; = 2.57 ppm confirm the successful synthesis of CT-PEG polymers. Figure 2b shows that the methylene proton signal of PEG at &#948; = 2.6 ppm and proton signal of PEI at <em...

Watch this Scientific Journal Video about Synthesis of Aptamer-PEI-g-PEG Modified Gold Nanoparticles Loaded with Doxorubicin for Targeted Drug Delivery at JoVE.com

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

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 ...

Because of the drug resistance and toxicity, the use of doxorubicin is limit in the clinic. This protocol provides a degradable carrier for keeping the release of this therapeutic agent. The advantage of this method is that the synthesized carrier can be used to deliver the drug directly to cancer cells, inducing cell death in the cancer cells only.For CT-PEG synthesis, first add 1.46 grams of succinic anhydride and 209 milligrams of 4-dimethylaminopyridine to a 100 milliliter round bottom flask. Next, add 15 milliliters of anhydrous tetrahydrofuran to the flask and fit a glass stopper into the flask, before incubating the reaction for 30 minutes at zero degrees Celsius. During the incubation, add 4.208 grams of PEG, 1.8 milliliters of triethylamine and 15 milliliters of anhydrous tetrahydrofuran to a new flask and close the flask with a glass stopper.At the end of the incubation, use a syringe under nitrogen atmosphere to slowly transfer the second solution to the first flask. Stir the new solution for two hours at zero degrees Celsius, before continuing the reaction at room temperature overnight. The next morning, use a rotary evaporator at 40 degrees Celsius and 0.1 megapascals to concentrate the reaction solution and to remove the tetrahydrofuran solvent.After an hour, dissolve the reaction solution in 15 milliliters of 1.325 gram per milliliter of dichloromethane at room temperature, before adding 15 milliliters of cold diethyl ether to obtain the PEG diacid precipitation product. Then remove the solvent via filter paper and dry the precipitate under vacuum for 48 hours at room temperature. For PEI-g-PEG copolymer synthesis, add 305.47 milligrams of the CT-PEG precipitate and five milliliters of DMSO to a new flask and stir the reaction at room temperature until the CT-PEG is fully dissolved.Next, dissolve 49.46 milligrams of EDC in five milliliters of DMSO and add the solution to the flask. Stir the reaction for 30 minutes at room temperature, before dissolving 29.69 milligrams of N-Hydroxysuccinimide and five milliliters of DMSO and adding the resulting solution to the flask. Continue to stir the reaction for three hours at room temperature.Near the end of the incubation, dissolve 28.6 microliters of PEI into 10 milliliters of DMSO and add the solution drop wise to the flask. Stir the reaction at room temperature for at least three days. At the end of the incubation, transfer the reacted solution to a dialysis bag with a 1000 molecular weight cutoff and place the bag into a one liter beaker containing 500 milliliters of ultra pure water as the dialysate.At the end of the dialysis, transfer the solution to a dialysis bag with a 10, 000 molecular weight cutoff and placed the bag into a one liter beaker with 500 milliliters of ultra pure water as the dialysate. At the end of the second dialysis, use a rotary evaporator at 40 degrees Celsius and 0.1 megapascals to concentrate the solution and freeze dry the sample to obtain the PEI-g-PEG powder. For the coating of gold nanoparticles with the PEI-g-PEG product, dissolve five milligrams of the prepared PEI-g-PEG in five milliliters of ultra pure water in a new flask and fit the flask with a glass stopper.Add 100 milliliters of 0.3 millimolar auric chloride solution to the flask and stir the solution for three hours at room temperature. The colors should change immediately from light yellow to dark yellow. At the end of the incubation, add one milliliter of one milligram per milliliter of sodium borohydride solution to the flask.The color should change immediately from dark yellow to golden yellow, and stir the solution for an additional three hours at room temperature. Then dialyze the reaction product with a 1000 molecular weight cutoff dialysis bag for three days as demonstrated to obtain the PEI-g-PEG coated gold nanoparticle solution. For grafting of doxorubicin to the PEI-g-PEG coated gold nanoparticles.Add one milliliter of 2.2 milligram per milliliter doxorubicin solution and 20 milliliters of the PEI-g-PEG coated gold nanoparticle solution to a new flask and fit the flask with a glass stopper. Next, dissolve 0.727 milligrams of EDC in one milliliter of ultra pure water and add the EDC solution to the flask. Dissolve 0.437 milligrams of N-Hydroxysuccinimide in one milliliter of ultra pure water, and add the N-Hydroxysuccinimide solution to the flask for a one hour incubation with stirring at room temperature.At the end of the incubation, dialyze the reaction product in a 1000 molecular weight cutoff dialysis bag for three days as demonstrated to obtain the doxorubicin g-PEI-g-PEG coated gold nanoparticle solution. For grafting of the AS1411 aptamer to the DOX-g-PEI-g-PEG. Add 20 milliliters of the doxorubicin DOX-g-PEI-g-PEG coated gold nanoparticle solution to an approximately four optical density concentration of AS1411.Dissolve 28.76 milligrams of EDC in one milliliter of ultra pure water and add the EDC solution to the flask. Dissolve 17.27 milligrams of N-Hydroxysuccinimide in one milliliter of ultra pure water and add the N-Hydroxysuccinimide solution to the flask for a one hour incubation with stirring at room temperature. Then dialyze the reaction product in a 1000 molecular weight cutoff dialysis bag for three days as demonstrated to obtain AS1411-g-Doxorubicin-g-PEI-g-PEG coated gold nanoparticles.Proton NMR spectroscopy can be used to confirm the successful synthesis of CT-PEG polymer and PIE-g-PEG copolymers. Ultra violet spectroscopy can be conducted to determine the successful functionalization and gradual loading of prepared copolymer on gold nanoparticles. X-ray photo electron spectroscopy can be used to investigate the chemical bond of co-polymer on gold nanoparticles.Dynamic light scattering can be performed to determine the size distribution of the prepared nanoparticles. In this analysis, transmission electron microscopy revealed non-clustered nanoparticles with a uniform morphology. Cell viability analysis revealed a decrease in A549 cell numbers over time and in response to increasing concentrations of nanoparticle.Compare to the free doxorubicin group, the cell numbers increased, however, indicating a reduced toxicity. Further, analysis of the doxorubicin release profile reveals that the sustained release of doxorubicin from functionalized nanoparticles caused a decrease in A549 cells. The PEI-g-PEG copolymer preparation and AS1411 grafting steps are important for success for implementation of the procedure.The same drug carrier can be achieved by grafting AS1411 before grafting drugs, but the drug loading efficiency will be decreased.

synthesis-aptamer-pei-g-peg-modified-gold-nanoparticles-loaded-with

Research

JoVE Journal

Chemistry

Template Directed Synthesis of Plasmonic Gold Nanotubes with Tunable IR Absorbance

A nearly parallel array of pores can be produced by anodizing aluminum foils in acidic environments1, 2. Applications of anodic aluminum oxide (AAO) membranes have been under development since the 1990's and have become a common method to template the synthesis of high aspect ratio nanostructures, mostly by electrochemical growth or pore-wetting. Recently, these membranes have become commercially available in a wide range of pore sizes and densities, leading to an extensive library of functional nanostructures being synthesized from AAO membranes. These include composite nanorods, nanowires and nanotubes made of metals, inorganic materials or polymers 3-10. Nanoporous membranes have been used to synthesize nanoparticle and nanotube arrays that perform well as refractive index sensors, plasmonic biosensors, or surface enhanced Raman spectroscopy (SERS) substrates 11-16, as well as a wide range of other fields such as photo-thermal heating 17, permselective transport 18, 19, catalysis 20, microfluidics 21, and electrochemical sensing 22, 23. Here, we report a novel procedure to prepare gold nanotubes in AAO membranes. Hollow nanostructures have potential application in plasmonic and SERS sensing, and we anticipate these gold nanotubes will allow for high sensitivity and strong plasmon signals, arising from decreased material dampening 15.

Solution-suspendable gold nanotubes with controlled dimensions can be synthesized by electrochemical deposition in porous anodic aluminum oxide (AAO) membranes using a hydrophobic polymer core. Gold nanotubes and nanotube arrays hold promise for applications in plasmonic biosensing, surface-enhanced Raman spectroscopy, photo-thermal heating, ionic and molecular transport, microfluidics, catalysis and electrochemical sensing.

A nearly parallel array of pores can be produced by anodizing aluminum foils in acidic environments1, 2. Applications of anodic aluminum oxide (AAO) ...

Preparation and Characterization of SDF-1&#945;-Chitosan-Dextran Sulfate Nanoparticles

Chitosan (CS) and dextran sulfate (DS) are charged polysaccharides (glycans), which form polyelectrolyte complex-based nanoparticles when mixed under appropriate conditions. The glycan nanoparticles are useful carriers for protein factors, which facilitate the in vivo delivery of the proteins and sustain their retention in the targeted tissue. The glycan polyelectrolyte complexes are also ideal for protein delivery, as the incorporation is carried out in aqueous solution, which reduces the likelihood of inactivation of the proteins. Proteins with a heparin-binding site adhere to dextran sulfate readily, and are, in turn, stabilized by the binding. These particles are also less inflammatory and toxic when delivered in vivo. In the protocol described below, SDF-1&#945; (Stromal cell-derived factor-1&#945;), a stem cell homing factor, is first mixed and incubated with dextran sulfate. Chitosan is added to the mixture to form polyelectrolyte complexes, followed by zinc sulfate to stabilize the complexes with zinc bridges. The resultant SDF-1&#945;-DS-CS particles are measured for size (diameter) and surface charge (zeta potential). The amount of the incorporated SDF-1&#945; is determined, followed by measurements of its in vitro release rate and its chemotactic activity in a particle-bound form.

Preparation and Characterization of SDF-1&amp;#945;-Chitosan-Dextran Sulfate Nanoparticles

The objective of this protocol is to incorporate SDF-1&#945;, a stem cell homing factor, into dextran sulfate-chitosan nanoparticles. The resultant particles are measured for their size and zeta potential, as well as the content, activity, and in vitro release rate of SDF-1&#945; from the nanoparticles.

Chitosan (CS) and dextran sulfate (DS) are charged polysaccharides (glycans), which form polyelectrolyte complex-based nanoparticles when mixed under ...

A Simple Method for the Size Controlled Synthesis of Stable Oligomeric Clusters of Gold Nanoparticles under Ambient Conditions

Reducing dilute aqueous HAuCl4 with sodium thiocyanate (NaSCN) under alkaline conditions produces 2 to 3 nm diameter nanoparticles. Stable grape-like oligomeric clusters of these yellow nanoparticles of narrow size distribution are synthesized under ambient conditions via two methods. The delay-time method controls the number of subunits in the oligoclusters by varying the time between the addition of HAuCl4 to alkaline solution and the subsequent addition of reducing agent, NaSCN. The yellow oligoclusters produced range in size from ~3 to ~25 nm. This size range can be further extended by an add-on method utilizing hydroxylated gold chloride (Na+[Au(OH4-x)Clx]-) to auto-catalytically increase the number of subunits in the as-synthesized oligocluster nanoparticles, providing a total range of 3 nm to 70 nm. The crude oligocluster preparations display narrow size distributions and do not require further fractionation for most purposes. The oligoclusters formed can be concentrated &#62;300 fold without aggregation and the crude reaction mixtures remain stable for weeks without further processing. Because these oligomeric clusters can be concentrated before derivatization they allow expensive derivatizing agents to be used economically. In addition, we present two models by which predictions of particle size can be made with great accuracy.

We describe a simple method for producing highly stable oligomeric clusters of gold nanoparticles via the reduction of chloroauric acid (HAuCl4) with sodium thiocyanate (NaSCN). The oligoclusters have a narrow size distribution and can be produced with a wide range of sizes and surface coats.

Reducing dilute aqueous HAuCl4 with sodium thiocyanate (NaSCN) under alkaline conditions produces 2 to 3 nm diameter nanoparticles. Stable grape-like ...

Hydroquinone Based Synthesis of Gold Nanorods

Gold nanorods are an important kind of nanoparticles characterized by peculiar plasmonic properties. Despite their widespread use in nanotechnology, the synthetic methods for the preparation of gold nanorods are still not fully optimized. In this paper we describe a new, highly efficient, two-step protocol based on the use of hydroquinone as a mild reducing agent. Our approach allows the preparation of nanorods with a good control of size and aspect ratio (AR) simply by varying the amount of hexadecyl trimethylammonium bromide (CTAB) and silver ions (Ag+) present in the "growth solution". By using this method, it is possible to markedly reduce the amount of CTAB, an expensive and cytotoxic reagent, necessary to obtain the elongated shape. Gold nanorods with an aspect ratio of about 3 can be obtained in the presence of just 50 mM of CTAB (versus 100 mM used in the standard protocol based on the use of ascorbic acid), while shorter gold nanorods are obtained using a concentration as low as 10 mM.

This paper describes a protocol for the synthesis of gold nanorods, based on the use of hydroquinone as reducing agent, plus the different mechanisms for controlling their size and aspect ratio.

Gold nanorods are an important kind of nanoparticles characterized by peculiar plasmonic properties. Despite their widespread use in nanotechnology, the ...

Rapid Nanoprobe Signal Enhancement by In Situ Gold Nanoparticle Synthesis

The use of nanoprobes such as gold, silver, silica or iron-oxide nanoparticles as detection reagents in bioanalytical assays can enable high sensitivity and convenient colorimetric readout. However, high densities of nanoparticles are typically needed for detection. The available synthesis-based enhancement protocols are either limited to gold and silver nanoparticles or rely on precise enzymatic control and optimization. Here, we present a protocol to enhance the colorimetric readout of gold, silver, silica, and iron oxide nanoprobes. It was observed that the colorimetric signal can be improved by up to a 10000-fold factor. The basis for such signal enhancement strategies is the chemical reduction of Au3+ to Au0. There are several chemical reactions that enable the reduction of Au3+ to Au0. In the protocol, Good&#39;s buffers and H2O2 are used and it is possible to favor the deposition of Au0 onto the surface of existing nanoprobes, in detriment of the formation of new gold nanoparticles. The protocol consists of the incubation of the microarray with a solution consisting of chloroauric acid and H2O2 in 2-(N-morpholino)ethanesulfonic acid pH 6 buffer following the nanoprobe-based detection assay. The enhancement solution can be applied to paper and glass-based sensors. Moreover, it can be used in commercially available immunoassays as demonstrated by the application of the method to a commercial allergen microarray. The signal development requires less than 5 min of incubation with the enhancement solution and the readout can be assessed by naked eye or low-end image acquisition devices such as a table-top scanner or a digital camera.

Rapid Nanoprobe Signal Enhancement by In Situ Gold Nanoparticle Synthesis

In this work, a protocol for signal enhancement of nanoprobe-based biosensing is presented. The protocol is based on the reduction of chloroauric acid onto the surface of existing nanoprobes that consist of gold, silver, silica or iron-oxide nanoparticles.

The use of nanoprobes such as gold, silver, silica or iron-oxide nanoparticles as detection reagents in bioanalytical assays can enable high sensitivity ...

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.

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 ...

Synthesis and Characterization of Amphiphilic Gold Nanoparticles

Gold nanoparticles covered with a mixture of 1-octanethiol (OT) and 11-mercapto-1-undecane sulfonic acid (MUS) have been extensively studied because of their interactions with cell membranes, lipid bilayers, and viruses. The hydrophilic ligands make these particles colloidally stable in aqueous solutions and the combination with hydrophobic ligands creates an amphiphilic particle that can be loaded with hydrophobic drugs, fuse with the lipid membranes, and resist nonspecific protein adsorption. Many of these properties depend on nanoparticle size and the composition of the ligand shell. It is, therefore, crucial to have a reproducible synthetic method and reliable characterization techniques that allow the determination of nanoparticle properties and the ligand shell composition. Here, a one-phase chemical reduction, followed by a thorough purification to synthesize these nanoparticles with diameters below 5 nm, is presented. The ratio between the two ligands on the surface of the nanoparticle can be tuned through their stoichiometric ratio used during synthesis. We demonstrate how various routine techniques, such as transmission electron microscopy (TEM), nuclear magnetic resonance (NMR), thermogravimetric analysis (TGA), and ultraviolet-visible (UV-Vis) spectrometry, are combined to comprehensively characterize the physicochemical parameters of the nanoparticles.

Amphiphilic gold nanoparticles can be used in many biological applications. A protocol to synthesize gold nanoparticles coated by a binary mixture of ligands and a detailed characterization of these particles is presented.

Gold nanoparticles covered with a mixture of 1-octanethiol (OT) and 11-mercapto-1-undecane sulfonic acid (MUS) have been extensively studied because of ...

Gold Nanoparticle Modified Carbon Fiber Microelectrodes for Enhanced Neurochemical Detection

For over 30 years, carbon-fiber microelectrodes (CFMEs) have been the standard for neurotransmitter detection. Generally, carbon fibers are aspirated into glass capillaries, pulled to a fine taper, and then sealed using an epoxy to create electrode materials that are used for fast scan cyclic voltammetry testing. The use of bare CFMEs has several limitations, though. First and foremost, the carbon fiber contains mostly basal plane carbon, which has a relatively low surface area and yields lower sensitivities than other nanomaterials. Furthermore, the graphitic carbon is limited by its temporal resolution, and its relatively low conductivity. Lastly, neurochemicals and macromolecules have been known to foul at the surface of carbon electrodes where they form non-conductive polymers that block further neurotransmitter adsorption. For this study, we modify CFMEs with gold nanoparticles to enhance neurochemical testing with fast scan cyclic voltammetry. Au3+ was electrodeposited or dipcoated from a colloidal solution onto the surface of CFMEs. Since gold is a stable and relatively inert metal, it is an ideal electrode material for analytical measurements of neurochemicals. Gold nanoparticle modified (AuNP-CFMEs) had a stability to dopamine response for over 4 h. Moreover, AuNP-CFMEs exhibit an increased sensitivity (higher peak oxidative current of the cyclic voltammograms) and faster electron transfer kinetics (lower &#916;EP or peak separation) than bare unmodified CFMEs. The development of AuNP-CFMEs provides the creation of novel electrochemical sensors for detecting fast changes in dopamine concentration and other neurochemicals at lower limits of detection. This work has vast applications for the enhancement of neurochemical measurements. The generation of gold nanoparticle modified CFMEs will be vitally important for the development of novel electrode sensors to detect neurotransmitters in vivo in rodent and other models to study neurochemical effects of drug abuse, depression, stroke, ischemia, and other behavioral and disease states.

In this study, we modify carbon-fiber microelectrodes with gold nanoparticles to enhance the sensitivity of neurotransmitter detection.

For over 30 years, carbon-fiber microelectrodes (CFMEs) have been the standard for neurotransmitter detection. Generally, carbon fibers are aspirated into ...

Nanoparticle Tracking Analysis of Gold Nanoparticles in Aqueous Media through an Inter-Laboratory Comparison

In the field of nanotechnology, analytical characterization plays a vital role in understanding the behavior and toxicity of nanomaterials (NMs). Characterization needs to be thorough and the technique chosen should be well-suited to the property to be determined, the material being analyzed and the medium in which it is present. Furthermore, the instrument operation and methodology need to be well-developed and clearly understood by the user to avoid data collection errors. Any discrepancies in the applied method or procedure can lead to differences and poor reproducibility of obtained data. This paper aims to clarify the method to measure the hydrodynamic diameter of gold nanoparticles by means of Nanoparticle Tracking Analysis (NTA). This study was carried out as an inter-laboratory comparison (ILC) amongst seven different laboratories to validate the standard operating procedure&#8217;s performance and reproducibility. The results obtained from this ILC study reveal the importance and benefits of detailed standard operating procedures (SOPs), best practice updates, user knowledge, and measurement automation.

The protocol described here aims to measure the hydrodynamic diameter of spherical nanoparticles, more specifically gold nanoparticles, in aqueous media by means of Nanoparticle Tracking Analysis (NTA). The latter involves tracking the movement of particles due to Brownian motion and implementing the Stokes-Einstein equation to obtain the hydrodynamic diameter.

In the field of nanotechnology, analytical characterization plays a vital role in understanding the behavior and toxicity of nanomaterials (NMs). ...

Gold Nanoparticle Synthesis

Gold nanoparticles (Au nanoparticles) that are ~12 nm in diameter were synthesized by rapidly injecting a solution of 150 mg (0.15 mmol) of tetrachloroauric acid in 3.0 g (3.7 mmol, 3.6 mL) of oleylamine (technical grade) and 3.0 mL of toluene into a boiling solution of 5.1 g (6.4 mmol, 8.7 mL) of oleylamine in 147 mL of toluene. While boiling and mixing the reaction solution for 2 hours, the color of the reaction mixture changed from clear, to light yellow, to light pink, and then slowly to dark red. The heat was then turned off, and the solution was allowed to gradually cool down to room temperature for 1 hour. The gold nanoparticles were then collected and separated from the solution using a centrifuge and washed three times; by vortexing and dispersing the gold nanoparticles in 10 mL portions of toluene, and then precipitating the gold nanoparticles by adding 40 mL portions of methanol and spinning them in a centrifuge. The solution was then decanted to remove any remaining byproducts and unreacted starting materials. Drying the gold nanoparticles in a vacuum environment produced a solid black pellet; which could be stored for long periods of time (up to one year) for later use, and then redissolved in organic solvents such as toluene.

A protocol for synthesizing ~12 nm diameter gold nanoparticles (Au nanoparticles) in an organic solvent is presented. The gold nanoparticles are capped with oleylamine ligands to prevent agglomeration. The gold nanoparticles are soluble in organic solvents such as toluene.