Name: electroactive polymer nanoparticles exhibiting photothermal properties
Uploaded: 2016-01-08T14:00:01
Description: Watch this Scientific Journal Video about Electroactive Polymer Nanoparticles Exhibiting Photothermal Properties at JoVE.com

This work was funded in part by the Texas Emerging Technology Fund (Startup to TB), the Texas State University Research Enhancement Program, the Texas State University Doctoral Research Fellowship (to TC), the NSF Partnership for Research and Education in Materials (PREM, DMR-1205670), The Welch Foundation (AI-0045), and National Institutes of Health (R01CA032132).

Caution: Please consult all relevant Safety Data Sheets (SDS) before use. Several of the reagents used in these syntheses are potentially hazardous. Please use all appropriate safety practices including personal protective equipment (safety glasses, gloves, lab coat, long pants, and closed-toe shoes), and perform syntheses in fume hoods. Lithiation is particularly hazardous and should only be performed by properly trained individuals with supervision.
1. Monomer Synthesis
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In this work, electroactive polymer NPs have been synthesized as potential PTT agents for cancer treatment. The preparation of the NPs is described, starting with the synthesis of the monomers followed by emulsion polymerization. While the preparation of NPs using electroactive polymers such as EDOT and pyrrole has been described before, this paper describes the preparation of polymeric NPs starting with unique extended conjugation monomers, demonstrating that this process can be extended to larger, more complex monomers...

Electroactive polymers change their properties (color, conductivity, reactivity, volume, etc.) in the presence of an electric field. The rapid switching times, tunability, durability, and lightweight characteristics of electroactive polymers have led to many proposed applications, including alternative energy, sensors, electrochromics, and biomedical devices. Electroactive polymers are potentially useful as flexible, light-weight battery and capacitor electrodes.1 Applications of electroactive polymers in electrochromic devices include glare-reduction systems for buildings and automobiles, sunglasses, protective eyewear, optical storage devices, and smart textiles.2-5 Smart windows can reduce energy requirements by blocking specific wavelengths of light on-demand and protecting interiors of homes and automobiles. Smart textiles can be used in clothing to help protect against UV radiation.6 Electroactive polymers have also begun to be used in medical devices. Among electroactive polymers used in biomedical devices, polypyrrole (PPy), polyaniline (PANI), and poly(3,4-ethylenedioxythiophene) (PEDOT) are among the most common. For example, these types of polymers are commonly used as transducers in biosensor devices.7 Applications in therapeutic delivery have also shown promise; studies have demonstrated the release of drugs and therapeutic proteins from devices prepared from electroactive polymers.8-12 More recently, electroactive polymers have been used as therapeutic agents in photothermal therapy.13-15 In photothermal therapy, photothermal agents must absorb light in the near-infrared (NIR) region (~ 700&#8722;900 nm), also known as the therapeutic window, where light has the maximum depth of penetration in tissue, typically up to 1 cm.16,17 In this range, biological chromophores such as hemoglobin, oxygenated hemoglobin, lipids, and water have little-to-no absorbance, which enables light to penetrate easily. When photothermal agents absorb light in this therapeutic window, the photoenergy is converted to photothermal energy.
Irvin and co-workers have previously reported alkoxy-substituted bis-EDOT benzene monomers that were synthesized using Negishi coupling.18 Negishi coupling is a preferred method for carbon-carbon bond formation. This process has many advantages, including the use of organozinc intermediates, which are less toxic and tend to have higher reactivity than other organometallics used.19,20 Organozinc compounds are also compatible with a wide range of functional groups on the organohalides.20 In the Negishi coupling reaction, an organohalide and organometal are coupled through the use of a palladium(0) catalyst.20 In the work presented herein, this cross coupling method is utilized in the synthesis of 1,4-dialkoxy-2,5-bis(3,4-ethylenedioxythienyl) benzene (BEDOT-B(OR)2) monomers. These monomers can then be easily polymerized electrochemically or chemically to yield polymers that are promising candidates for use in biomedical applications.
Conventional methods for preparation of colloidal polymeric suspensions in aqueous solutions for biomedical applications typically involve the dissolution of bulk polymers followed by nanoprecipitation or emulsion-solvent evaporation techniques.21,22 In order to produce NPs of poly(BEDOT-B(OR)2), a bottom-up approach is demonstrated here where the NPs are synthesized via in situ emulsion polymerization. Emulsion polymerization is a process that is easily scalable and is a relatively fast method for NP preparation.22 Studies using emulsion polymerization to produce NPs of other electroactive polymers have been reported for PPy and PEDOT.15,23,24 PEDOT NPs, for example, have been prepared using spray emulsion polymerization.24 This method is difficult to reproduce, and typically yields larger, micron-sized particles. The protocol described in this article explores the use of a drop-sonication method to reproducibly prepare 100-nm polymer NPs.
In this protocol, electroactive polymers tailored to absorb light in the NIR region similar to previously reported poly(BEDOT-B(OR)2) are synthesized and characterized to demonstrate their potential in electrochromic devices and as PTT agents. First, the protocol for the synthesis of the monomers via Negishi coupling is described. The monomers are characterized using NMR and UV-Vis-NIR spectroscopy. The preparation of NP colloid suspensions via oxidative emulsion polymerization in aqueous media is also described. The procedure is based on a two-step emulsion polymerization process previously described by Han et al. that is applied to the different monomers. A two-surfactant system is used to control the NP monodispersity. A cell viability assay is used to evaluate cytocompatibility of the NPs. Lastly, the potential of these NPs to act as PTT transducers is demonstrated by irradiation with a NIR laser.

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		<tr height="42">
			<td height="42" style="height:42px;width:291px;">2 mm diameter platinum working electrode</td>
			<td style="width:171px;">CH Instruments</td>
			<td style="width:119px;">CH102</td>
			<td style="width:167px;">Polished using very fine sandpaper</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:291px;">3,4-ethylenedioxythiophene</td>
			<td>Sigma-Aldrich</td>
			<td style="width:119px;">483028</td>
			<td style="width:167px;">Purified by vacuum distillation</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:291px;">3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide (MTT) 98%</td>
			<td>Alfa Aesar</td>
			<td style="width:119px;">L11939</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;">505 Sonic Dismembrator</td>
			<td>Fisher Scientific&#8482;&#160;</td>
			<td style="width:119px;">FB505110</td>
			<td style="width:167px;">1/8 &#8220; tip and rated at 500 watts</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:291px;">808 nm laser diode</td>
			<td>ThorLabs</td>
			<td style="width:119px;">L808P1WJ</td>
			<td style="width:167px;">Rated at 1 W</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:291px;">Acetonitrile anhydrous 99%</td>
			<td>Acros</td>
			<td style="width:119px;">61022-0010</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:291px;">Avanti J-26 XPI</td>
			<td>Beckman Coulter</td>
			<td style="width:119px;">393127</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:291px;">Bromohexane 98%</td>
			<td>MP Biomedicals</td>
			<td style="width:119px;">202323</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:291px;">Dialysis (100,000) MWCO</td>
			<td>SpectrumLabs</td>
			<td style="width:119px;">G235071</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:291px;">Dimethyl sulfoxide 99% (DMSO)</td>
			<td>BDH</td>
			<td style="width:119px;">BDH1115</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:291px;">Dimethylformamide anhydrous (DMF) 99%</td>
			<td>Acros</td>
			<td style="width:119px;">326870010</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:291px;">Dodecyl benzenesulfonate (DBSA)&#160;</td>
			<td>TCI</td>
			<td style="width:119px;">D0989</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Dulbecco&#8217;s modified eagle medium (DMEM)&#160;</td>
			<td>Corning</td>
			<td style="width:119px;">10-013 CV</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;">EMS 150 TES sputter coater</td>
			<td style="width:171px;">Electron Microscopy Sciences</td>
			<td style="width:119px;"></td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:291px;">Ethanol (EtOH) 100%</td>
			<td>BDH</td>
			<td style="width:119px;">BDH1156</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:291px;">ethyl 4-bromobutyrate (98%)</td>
			<td>Acros</td>
			<td style="width:119px;">173551000</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:291px;">Ethyl acetate 99%</td>
			<td>Fisher</td>
			<td style="width:119px;">UN1173</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Fetal bovine serum (FBS)</td>
			<td>Corning</td>
			<td style="width:119px;">35-010-CV</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:291px;">Helios NanoLab 400</td>
			<td>FEI</td>
			<td style="width:119px;"></td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:291px;">Hexane</td>
			<td>Fisher</td>
			<td style="width:119px;">H306-4</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:291px;">Hydrochloric acid (HCl)</td>
			<td>Fisher</td>
			<td style="width:119px;">A142-212</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:291px;">Hydroquinone 99.5%</td>
			<td>Acros</td>
			<td style="width:119px;">120915000</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:291px;">Hydrozine anhydrous 98%</td>
			<td>Sigma-Aldrich</td>
			<td style="width:119px;">215155</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:291px;">Indium tin oxide (ITO) coated galss</td>
			<td>Delta Technologies</td>
			<td style="width:119px;">CG-41IN-CUV</td>
			<td style="width:167px;">4-8 &#937;/sq</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:291px;">Iron chloride 97% FeCl3</td>
			<td>Sigma-Aldrich</td>
			<td style="width:119px;">157740</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:291px;">Magnesium sulfate (MgSO4)</td>
			<td>Fisher</td>
			<td style="width:119px;">593295</td>
			<td style="width:167px;">Dried at 100 oC</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:291px;">SKOV-3</td>
			<td>ATCC</td>
			<td style="width:119px;">HTB-26</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:291px;">Methanol</td>
			<td>BDH</td>
			<td style="width:119px;">BHD1135</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:291px;">n-Butlithium (2.5 M)&#160;</td>
			<td>Sigma-Aldrich</td>
			<td style="width:119px;">230707</td>
			<td style="width:167px;">Pyrophoric</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:291px;">Poly(styrenesulfonate-co-malic acid) (PSS-co-MA) 20,000 MW</td>
			<td>Sigma-Aldrich</td>
			<td style="width:119px;">434566</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:291px;">Potassium carbonate</td>
			<td>Sigma-Aldrich</td>
			<td style="width:119px;">209619</td>
			<td style="width:167px;">Dried at 100 oC</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:291px;">Potassium hydroxide</td>
			<td>Alfa Aesar</td>
			<td style="width:119px;">A18854</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:291px;">Potassium iodide</td>
			<td>Fisher</td>
			<td style="width:119px;">P410-100</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:291px;">RO-5 stirplate</td>
			<td>IKA-Werke</td>
			<td style="width:119px;"></td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:291px;">SC4000 IR camera</td>
			<td>FLIR</td>
			<td style="width:119px;"></td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:291px;">Synergy H4 Hybrid Reader</td>
			<td>Biotek</td>
			<td style="width:119px;"></td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:291px;">Tetrabutylammonium perchlorate (TBAP) 99%</td>
			<td>Sigma-Aldrich</td>
			<td style="width:119px;">3579274</td>
			<td style="width:167px;">Purified by recrystallization in ethyl acetate</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:291px;">Tetrahydrofuran anhydrous (THF) 99%</td>
			<td>Sigma-Aldrich</td>
			<td style="width:119px;">401757</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:291px;">tetrakis(triphenylphosphine) 
			palladium(0)</td>
			<td>Sigma-Aldrich</td>
			<td style="width:119px;">216666</td>
			<td style="width:167px;">Moisture sensitive</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:291px;">Thermomixer</td>
			<td>Eppendorf</td>
			<td style="width:119px;"></td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:291px;">USB potentiostat/galvanostat</td>
			<td>WaveNow</td>
			<td style="width:119px;">AFTP1</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:291px;">Zetasizer Nano Zs</td>
			<td>Malvern</td>
			<td style="width:119px;"></td>
			<td style="width:167px;">Optical Arrangment 175o</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:291px;">Zinc chloride (1 M) ZnCl2</td>
			<td>Acros</td>
			<td style="width:119px;">370057000</td>
			<td style="width:167px;"></td>
		</tr>
	</tbody>
</table>

electroactive polymer nanoparticles exhibiting photothermal properties

A method for the synthesis of electroactive polymers is demonstrated, starting with the synthesis of extended conjugation monomers using a three-step process that finishes with Negishi coupling. Negishi coupling is a cross-coupling process in which a chemical precursor is first lithiated, followed by transmetallation with ZnCl2. The resultant organozinc compound can be coupled to a dibrominated aromatic precursor to give the conjugated monomer. Polymer films can be prepared via electropolymerization of the monomer and characterized using cyclic voltammetry and ultraviolet-visible-near infrared (UV-Vis-NIR) spectroscopy. Nanoparticles (NPs) are prepared via emulsion polymerization of the monomer using a two-surfactant system to yield an aqueous dispersion of the polymer NPs. The NPs are characterized using dynamic light scattering, electron microscopy, and UV-Vis-NIR-spectroscopy. Cytocompatibility of NPs is investigated using the cell viability assay. Finally, the NP suspensions are irradiated with a NIR laser to determine their effectiveness as potential materials for photothermal therapy (PTT).

The reaction protocol yielding M1 and M2 is shown in Figure 1. The monomers can be characterized by 1H and 13C NMR spectroscopy, melting point, and elemental analysis. The 1H NMR spectrum provides information regarding the connectivity of atoms and their electronic environments; thus, it is routinely used to verify that reactions have been completed successfully. Negishi coupling reactions involve coupling of the phenyl ring to the EDOT, c...

Watch this Scientific Journal Video about Electroactive Polymer Nanoparticles Exhibiting Photothermal Properties at JoVE.com

Electroactive Polymer Nanoparticles Exhibiting Photothermal Properties

A protocol is presented for the synthesis and preparation of nanoparticles consisting of electroactive polymers.

A method for the synthesis of electroactive polymers is demonstrated, starting with the synthesis of extended conjugation monomers using a three-step ...

The overall goal of this protocol is to prepare conductive polymer nanoparticles that exhibit photothermal properties, and evaluate their cytotoxicity. Conductive polymer nanoparticles are ideal agents for photothermal therapy because they absorb light in the near infrared range and convert it to heat to kill cancer cells. The main advantage of polymeric phototherapy agents is that they can be tailored to tune their absorption properties by a compatibility and tumor targeting ability to enable effective non-invasive localized cancer therapy.The polymers we are using for photothermal therapy can also be used for alternative energy applications, sensors and electrochromics. Individuals new to this method may struggle because the reaction is sensitive to moisture. A good understanding of airless synthesis techniques is essential.Visual demonstration of cell culture assays is critical as sterile techniques are difficult to master. All multi-role play assays require accuracy and consistency to achieve proper results. To a three-neck, round-bottom flask secure a septum, a condenser fitted with an inlet control adapter, and a gas outlet control adapter.Connect the gas outlet adapter to a bubbler. Next, connect the inlet adapter to an argon Shlenk line with thick-walled PVC tubing. Begin the flow of argon into the reaction flask, and let the gas flow for several minutes.After turning on the vacuum, use a Bunsen burner to flame dry the reaction, and then purge the apparatus with argon. Repeat this twice more to achieve an airless environment. Use a syringe to add one point zero seven grams of EDOT to the apparatus through the septum.Add 20 milliliters of Tetrahydrofuran into the flask and stir. Prepare a dry ice acetone bath in a Low-form Dewar flask, and chill the EDOT flask for 15 minutes at minus 78 degrees Celsius. Then drop wise at 11 millimoles of n-butyllithium in hexanes while maintaining a temperature of minus 78 degrees Celsius.After complete addition, stir for an additional hour. Extreme caution must be taken when handling organolithium reagents. These solutions are exceptionally hazardous, and should only be handled by someone who has been extensively trained in their use.Remove the dry ice acetone bath. And, immediately begin a drop wise addition of 14 point 13 milliliters of a one Molar Zinc Chloride solution, stirring for one hour at room temperature. Next, add four millimoles of one four Dialkoxy two five Dibromobenzene, and 80 micromoles of palladium tetrakis triphenylphosphine to the reaction.Begin re-fluxing the reaction at 75 degrees Celsius with an oil bath. Each day, use a syringe to take a small sample of the reaction mixture. Precipitate the sample into two milliliters of one Molar hydrochloric acid, and use two milliliters of dichloromethane to extract the material.Spot the extract on a silica thin layer chromatography, or TLC plate, alongside pre-made solutions of purified EDOT and the corresponding one four Dialkoxy two five Dibromobenzene. Use a 60 to 40 solution of ethyl acetate and hexanes to develop the plate in a glass chamber. Once the reaction is complete, in three to five days, cool the reaction to room temperature.Add 10 milliliters of one Molar hydrochloric acid followed by 20 milliliters of dichloromethane to quench the reaction. Transfer the reaction work-up to a separatory funnel, and isolate the organic layer. Wash the organics with deionized water until the water washes are no longer acidic.Next, dry the organics over 15 grams of magnesium sulfate. After filtering off the solid, remove the solvent using a rotary evaporator to yield a yellow orange solid. In a glass vile, prepare one milliliter of two percent weight by volume PSS-co-MA in water, and add a small stir bar.Prepare a 16 milligram per milliliter solution of monomer in chloroform and transfer 100 microliters of it into a microcentrifuged tube. Dissolve 30 milligrams of dodecylbenzene sulfonic acid in the microcentrifuge tube, and then use an automatic vortex mixer for 30 to 60 minutes to homogenize the solution. Next, add the homogenized organic phase in 10 microliter aliquot to the two percent PSS-co-MA solution every 60 seconds.After complete addition, dilute the solution with two milliliters of water and remove the stir bar. Place the emulsion in an ice bath, and then use a probe to sonicate emlusion with two 10 second intervals at an amplitude of 30 percent. Remove the vial from the ice bath, and replace the stir bar to continue mixing the emulsion.Next, add three point eight microliters of a one hundred milligrams per milliliter aqueous solution of iron chloride to the monomer emulsion, and stir for one hour to yield polymer nanoparticles stabilized with PSS-co-MA. Transfer the nanoparticles suspension into a seven milliliter centrifuge tubes, and centrifuge the suspension at 75, 600 times G for three minutes. Finally, recover the supernatant, and dialyze in water for 24 hours using 100 kilodalton molecular weight cut-off dialysis tubing.Culture SCOV three ovarian cancer cells in DMEMs supplemented with 10 percent fetal bovine serum at 37 degrees Celsius and five percent carbon dioxide in T 75 flasks. After dissociating and counting cells using standard protocols, feed cells at a density of 5, 000 cells per well in a 96 well plate. Incubate the cells for 24 hours at 37 degrees Celsius and five percent carbon dioxide.Immediately before use, delude the nanoparticles suspension into full growth medium at a concentration of one milligram per milliliter. Filter the nanoparticles suspension through a sterile zero point two micrometer filter. Then dilute the suspension to the desired exposure concentrations with full growth medium supplemented with one percent penicillin streptomycin.Gently remove the medium from each well and replace with 100 microliters of the nanoparticles suspension at various exposure concentrations. After incubating the cells, carefully remove the solution, and then replace the medium with 100 microliters of sterile filtered zero point five milligrams per milliliter MTT solution. Incubate the cells for two to four hours in the incubator.Then examine the cells under a microscope to check for formation of Formazan crystals. Carefully remove the MTT solution and replace it with 100 microliters of dimethyl sulfoxide. Place the plate on a shaker and mix for several minutes.Finally, measure the absorbents of each well at 590 nanometers and 700 nanometers. These values correspond to the peak absorbents of Formazan product and a baseline respectively. The resulting monomers can be characterized by hydrogen and carbon 13 NMR spectroscopy.Negishi coupling reactions attach the phenyl ring to the EDOT causing the phenyl proton peak to shift from seven point one PPM to seven point eight PPM. The theyenel proton also shifts up field to six point five PPM. The four protons on the ethylenedioxy bridge carbons split into two sets of multiplets at four point three PPM.The carbon 13 NMR spectrum exhibits peaks at one 70, one 45, one 40 and one 13 for the thyenel carbons, and one 50, one 20, and one 12 for the phenylene carbons. The cital compatibility of polymer nanoparticles is determined using an MTT cell viability assay. Within the nanaparticle concentration range of zero point two three to 56 micrograms per milliliter, then nanoparticles do not decrease cell viability to less than 90 percent of the control.Typically a reduction in cell viability of less than 20 percent is consisdered acceptable. Once mastered, it takes about a week to synthesize the Monomer, another week to purify it, and less than a day to prepare and purify the nanoparticles. The citotoxicity study can be completed in two and a half days from cell seeding to the conclusion of the assay.While attempting in vitro cell studies, it is critical to follow proper aseptic techniques. Additional studies such as live dead assays, microscopy studies, and in vivo biodistribution, and photothermal ovulation studies can be performed with the nanoparticles prepared through these protocols to better understand their potential as photothermal agents for cancer therapy.

electroactive-polymer-nanoparticles-exhibiting-photothermal-properties

Research

JoVE Journal

Engineering

Micropunching Lithography for Generating Micro- and Submicron-patterns on Polymer Substrates

Conducting polymers have attracted great attention since the discovery of high conductivity in doped polyacetylene in 19771. They offer the advantages of low weight, easy tailoring of properties and a wide spectrum of applications2,3. Due to sensitivity of conducting polymers to environmental conditions (e.g., air, oxygen, moisture, high temperature and chemical solutions), lithographic techniques present significant technical challenges when working with these materials4. For example, current photolithographic methods, such as ultra-violet (UV), are unsuitable for patterning the conducting polymers due to the involvement of wet and/or dry etching processes in these methods. In addition, current micro/nanosystems mainly have a planar form5,6. One layer of structures is built on the top surfaces of another layer of fabricated features. Multiple layers of these structures are stacked together to form numerous devices on a common substrate. The sidewall surfaces of the microstructures have not been used in constructing devices. On the other hand, sidewall patterns could be used, for example, to build 3-D circuits, modify fluidic channels and direct horizontal growth of nanowires and nanotubes.
A macropunching method has been applied in the manufacturing industry to create macropatterns in a sheet metal for over a hundred years. Motivated by this approach, we have developed a micropunching lithography method (MPL) to overcome the obstacles of patterning conducting polymers and generating sidewall patterns. Like the macropunching method, the MPL also includes two operations (Fig. 1): (i) cutting; and (ii) drawing. The "cutting" operation was applied to pattern three conducting polymers4, polypyrrole (PPy), Poly(3,4-ethylenedioxythiophen)-poly(4-styrenesulphonate) (PEDOT) and polyaniline (PANI). It was also employed to create Al microstructures7. The fabricated microstructures of conducting polymers have been used as humidity8, chemical8, and glucose sensors9. Combined microstructures of Al and conducting polymers have been employed to fabricate capacitors and various heterojunctions9,10,11. The "cutting" operation was also applied to generate submicron-patterns, such as 100- and 500-nm-wide PPy lines as well as 100-nm-wide Au wires. The "drawing" operation was employed for two applications: (i) produce Au sidewall patterns on high density polyethylene (HDPE) channels which could be used for building 3D microsystems12,13,14, and (ii) fabricate polydimethylsiloxane (PDMS) micropillars on HDPE substrates to increase the contact angle of the channel15.

A micropunching lithography approach is developed to generate micro- and submicron-patterns on top, sidewall and bottom surfaces of polymer substrates. It overcomes the obstacles of patterning conducting polymers and generating sidewall patterns. This method allows rapid fabrication of multiple features and is free of aggressive chemistry.

Conducting polymers have attracted great attention since the discovery of high conductivity in doped polyacetylene in 19771. They offer the advantages of ...

Optical Trapping of Nanoparticles

Optical trapping is a technique for immobilizing and manipulating small objects in a gentle way using light, and it has been widely applied in trapping and manipulating small biological particles. Ashkin and co-workers first demonstrated optical tweezers using a single focused beam1. The single beam trap can be described accurately using the perturbative gradient force formulation in the case of small Rayleigh regime particles1. In the perturbative regime, the optical power required for trapping a particle scales as the inverse fourth power of the particle size. High optical powers can damage dielectric particles and cause heating. For instance, trapped latex spheres of 109 nm in diameter were destroyed by a 15 mW beam in 25 sec1, which has serious implications for biological matter2,3.
A self-induced back-action (SIBA) optical trapping was proposed to trap 50 nm polystyrene spheres in the non-perturbative regime4. In a non-perturbative regime, even a small particle with little permittivity contrast to the background can influence significantly the ambient electromagnetic field and induce a large optical force. As a particle enters an illuminated aperture, light transmission increases dramatically because of dielectric loading. If the particle attempts to leave the aperture, decreased transmission causes a change in momentum outwards from the hole and, by Newton's Third Law, results in a force on the particle inwards into the hole, trapping the particle. The light transmission can be monitored; hence, the trap can become a sensor. The SIBA trapping technique can be further improved by using a double-nanohole structure.
The double-nanohole structure has been shown to give a strong local field enhancement5,6. Between the two sharp tips of the double-nanohole, a small particle can cause a large change in optical transmission, thereby inducing a large optical force. As a result, smaller nanoparticles can be trapped, such as 12 nm silicate spheres7 and 3.4 nm hydrodynamic radius bovine serum albumin proteins8. In this work, the experimental configuration used for nanoparticle trapping is outlined. First, we detail the assembly of the trapping setup which is based on a Thorlabs Optical Tweezer Kit. Next, we explain the nanofabrication procedure of the double-nanohole in a metal film, the fabrication of the microfluidic chamber and the sample preparation. Finally, we detail the data acquisition procedure and provide typical results for trapping 20 nm polystyrene nanospheres.

The following setup approach details low power optical trapping of dielectric nanoparticles using a double-nanohole in metal film.

Optical trapping is a technique for immobilizing and manipulating small objects in a gentle way using light, and it has been widely applied in trapping ...

Preparation and Friction Force Microscopy Measurements of Immiscible, Opposing Polymer Brushes

Solvated polymer brushes are well known to lubricate high-pressure contacts, because they can sustain a positive normal load while maintaining low friction at the interface. Nevertheless, these systems can be sensitive to wear due to interdigitation of the opposing brushes. In a recent publication, we have shown via molecular dynamics simulations and atomic force microscopy experiments, that using an immiscible polymer brush system terminating the substrate and the slider surfaces, respectively, can eliminate such interdigitation. As a consequence, wear in the contacts is reduced. Moreover, the friction force is two orders of magnitude lower compared to traditional miscible polymer brush systems. This newly proposed system therefore holds great potential for application in industry. Here, the methodology to construct an immiscible polymer brush system of two different brushes each solvated by their own preferred solvent is presented. The procedure how to graft poly(N-isopropylacrylamide) (PNIPAM) from a flat surface and poly(methyl methacrylate) (PMMA) from an atomic force microscopy (AFM) colloidal probe is described. PNIPAM is solvated in water and PMMA in acetophenone. Via friction force AFM measurements, it is shown that the friction for this system is indeed reduced by two orders of magnitude compared to the miscible system of PMMA on PMMA solvated in acetophenone.

The methodology to perform friction force microscopy experiments for contacting brushes is presented: Two polymer brushes that are grafted from (a) substrates and (b) colloidal probes are slid to show that, by using two contacting immiscible brush systems, friction in sliding contacts is reduced compared to miscible brush systems.

Solvated polymer brushes are well known to lubricate high-pressure contacts, because they can sustain a positive normal load while maintaining low ...

Advanced Compositional Analysis of Nanoparticle-polymer Composites Using Direct Fluorescence Imaging

The fabrication of polymer-nanoparticle composites is extremely important in the development of many functional materials. Identifying the precise composition of these materials is essential, especially in the design of surface catalysts, where the surface concentration of the active component determines the activity of the material. Antimicrobial materials which utilize nanoparticles are a particular focus of this technology. Recently swell encapsulation has emerged as a technique for inserting antimicrobial nanoparticles into a host polymer matrix. Swell encapsulation provides the advantage of localizing the incorporation to the external surfaces of materials, which act as the active sites of these materials. However, quantification of this nanoparticle uptake is challenging. Previous studies explore the link between antimicrobial activity and surface concentration of the active component, but this is not directly visualized. Here we show a reliable method to monitor the incorporation of nanoparticles into a polymer host matrix via swell encapsulation. We show that the surface concentration of CdSe/ZnS nanoparticles can be accurately visualized through cross-sectional fluorescence imaging. Using this method, we can quantify the uptake of nanoparticles via swell encapsulation and measure the surface concentration of encapsulated particles, which is key in optimizing the activity of functional materials.

Here we present a reliable method to monitor the incorporation of nanoparticles into a polymer host matrix via swell encapsulation. We show that the surface concentration of cadmium selenide quantum dots can be accurately visualized through cross-sectional fluorescence imaging.

The fabrication of polymer-nanoparticle composites is extremely important in the development of many functional materials. Identifying the precise ...

Inkjet-printed Polyvinyl Alcohol Multilayers

Inkjet printing is a modern method for polymer processing, and in this work, we demonstrate that this technology is capable of producing polyvinyl alcohol (PVOH) multilayer structures. A polyvinyl alcohol aqueous solution was formulated. The intrinsic properties of the ink, such as surface tension, viscosity, pH, and time stability, were investigated. The PVOH-based ink was a neutral solution (pH 6.7) with a surface tension of 39.3 mN/m and a viscosity of 7.5 cP. The ink displayed pseudoplastic (non-Newtonian shear thinning) behavior at low shear rates, and overall, it demonstrated good time stability. The wettability of the ink on different substrates was investigated, and glass was identified as the most suitable substrate in this particular case. A proprietary 3D inkjet printer was employed to manufacture polymer multilayer structures. The morphology, surface profile, and thickness uniformity of inkjet-printed multilayers were evaluated via optical microscopy.

An inkjet printer was used to manufacture polyvinyl alcohol multilayers. Polyvinyl alcohol water-based ink was formulated, and the main physical properties were investigated.

Inkjet printing is a modern method for polymer processing, and in this work, we demonstrate that this technology is capable of producing polyvinyl alcohol ...

Subsurface Defect Localization by Structured Heating Using Laser Projected Photothermal Thermography

The presented method is used to locate subsurface defects oriented perpendicularly to the surface. To achieve this, we create destructively interfering thermal wave fields that are disturbed by the defect. This effect is measured and used to locate the defect. We form the destructively interfering wave fields by using a modified projector. The original light engine of the projector is replaced with a fiber-coupled high-power diode laser. Its beam is shaped and aligned to the projector&#39;s spatial light modulator and optimized for optimal optical throughput and homogeneous projection by first characterizing the beam profile, and, second, correcting it mechanically and numerically. A high-performance infrared (IR) camera is set up according to the tight geometrical situation (including corrections of the geometrical image distortions) and the requirement to detect weak temperature oscillations at the sample surface. Data acquisition can be performed once a synchronization between the individual thermal wave field sources, the scanning stage, and the IR camera is established by using a dedicated experimental setup which needs to be tuned to the specific material being investigated. During data post-processing, the relevant information on the presence of a defect below the surface of the sample is extracted. It is retrieved from the oscillating part of the acquired thermal radiation coming from the so-called depletion line of the sample surface. The exact location of the defect is deduced from the analysis of the spatial-temporal shape of these oscillations in a final step. The method is reference-free and very sensitive to changes within the thermal wave field. So far, the method has been tested with steel samples but is applicable to different materials as well, in particular to temperature sensitive materials.

This method aims at locating vertical subsurface defects. Here, we couple a laser with a spatial light modulator and trigger its video input to heat a sample surface deterministically with two anti-phased modulated lines while acquiring highly resolved thermal images. The defect position is retrieved from evaluating thermal wave interference minima.

The presented method is used to locate subsurface defects oriented perpendicularly to the surface. To achieve this, we create destructively interfering ...

Fabrication of Polymer Microspheres for Optical Resonator and Laser Applications

This paper describes three methods of preparing fluorescent microspheres comprising &#960;-conjugated or non-conjugated polymers: vapor diffusion, interface precipitation, and mini-emulsion. In all methods, well-defined, micrometer-sized spheres are obtained from a self-assembling process in solution. The vapor diffusion method can result in spheres with the highest sphericity and surface smoothness, yet the types of the polymers able to form these spheres are limited. On the other hand, in the mini-emulsion method, microspheres can be made from various types of polymers, even from highly crystalline polymers with coplanar, &#960;-conjugated backbones. The photoluminescent (PL) properties from single isolated microspheres are unusual: the PL is confined inside the spheres, propagates at the circumference of the spheres via the total internal reflection at the polymer/air interface, and self-interferes to show sharp and periodic resonant PL lines. These resonating modes are so-called "whispering gallery modes" (WGMs). This work demonstrates how to measure WGM PL from single isolated spheres using the micro-photoluminescence (&#181;-PL) technique. In this technique, a focused laser beam irradiates a single microsphere, and the luminescence is detected by a spectrometer. A micromanipulation technique is then used to connect the microspheres one by one and to demonstrate the intersphere PL propagation and color conversion from coupled microspheres upon excitation at the perimeter of one sphere and detection of PL from the other microsphere. These techniques, &#181;-PL and micromanipulation, are useful for experiments on micro-optic application using polymer materials.

Protocols for the synthesis of microspheres from polymers, the manipulation of microspheres, and micro-photoluminescence measurements are presented.

This paper describes three methods of preparing fluorescent microspheres comprising &#960;-conjugated or non-conjugated polymers: vapor diffusion, ...

Production and Characterization of Vacuum Deposited Organic Light Emitting Diodes

A method for producing simple and efficient thermally-activated delayed fluorescence organic light-emitting diodes (OLEDs) based on guest-host or exciplex donor-acceptor emitters is presented. With a step-by-step procedure, readers will be able to repeat and produce OLED devices based on simple organic emitters. A patterning procedure allowing the creation of personalized indium tin oxide (ITO) shape is shown. This is followed by the evaporation of all layers, encapsulation and characterization of each individual device. The end goal is to present a procedure that will give the opportunity to repeat the information presented in cited publication but also using different compounds and structures in order to prepare efficient OLEDs.

A protocol for the production of simple structured organic light-emitting diodes (OLEDs) is presented.

A method for producing simple and efficient thermally-activated delayed fluorescence organic light-emitting diodes (OLEDs) based on guest-host or exciplex ...

Installation Method to Enhance Quality Control for Fiber Reinforced Polymer Spike Anchors

Fiber reinforced polymer (FRP) anchors are a promising way to enhance the performance of externally-bonded FRPs applied to existing structures, as they can delay or even prevent debonding failure. However, a major concern faced by designers is the premature failure of the anchors due to stress concentration. Poor installation quality and preparation of the clearance holes can result in stress concentration that provokes this premature failure. This paper deals with an installation method that aims to reduce the impact of the stress concentration and to provide a proper quality control of the preparation of the drill hole. The method involves three parts: the drilling and cleaning of the holes, the smoothing of the hole edges with a customized drill bit, and the installation of the anchor itself, including the impregnation of the anchor dowel and its insertion. Anchor fans (the free length of the spikes) are then bonded to the external FRP reinforcement. For the end anchorage, and in the case of reinforcements with multiple plies, it is recommended that the anchor fan be inserted between two plies to assist the stress-transfer mechanism. 
The proposed procedure is complemented with a design approach for spike anchors, based on an extensive database. It is proposed that the design follow a number of steps, namely: selection of the anchor diameter and subsequent tensile strength of the connector (that is to say, the anchor before fanning out the free end), evaluation of the reduction in the tensile strength due to bending, provision of enough embedment to prevent slippage failure, and consideration of the number and spacing of anchors for a given reinforcement. In this sense, it should be noted that further research is needed in order to obtain a general expression for the contribution of spike anchors to overall bond strength of FRP reinforcements.

This manuscript presents a method for controlling the quality of installation for spike anchors designed to delay delamination of externally bonded fiber reinforced polymers. The protocol includes the preparation of the drill hole and the insertion process. The most influential parameters on the efficiency of the anchors are discussed.

Fiber reinforced polymer (FRP) anchors are a promising way to enhance the performance of externally-bonded FRPs applied to existing structures, as they ...

Application of a Coupling Agent to Improve the Dielectric Properties of Polymer-Based Nanocomposites

In this work, an easy, low-cost, and widely applicable method was developed to improve the compatibility between the ceramic fillers and the polymer matrix by adding 3-aminopropyltriethoxysilane (KH550) as a coupling agent during the fabrication process of BaTiO3-P(VDF-CTFE) nanocomposites through solution casting. Results show that the use of KH550 can modify the surface of ceramic nanofillers; therefore, good wettability on the ceramic-polymer interface was achieved, and the enhanced energy storage performances were obtained by a suitable amount of the coupling agent. This method can be used to prepare flexible composites, which is highly desirable for the production of high-performance film capacitors. If an excessive amount of coupling agent is used in the process, the non-attached coupling agent can participate in complex reactions, which leads to a decrease in dielectric constant and an increase in dielectric loss.

Here, we demonstrate a simple and low-cost solution-casting process to improve the compatibility between the filler and the matrix of polymer-based nanocomposites using surface modified BaTiO3 fillers, which can effectively enhance the energy density of the composites.

In this work, an easy, low-cost, and widely applicable method was developed to improve the compatibility between the ceramic fillers and the polymer ...