Microwave Heating of Poly(N-isopropylacrylamide)-Conjugated Gold

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Microwave Heating of Poly(N-isopropylacrylamide)-Conjugated Gold Nanoparticles for Temperature-Controlled Display of Concanavalin A Roshan Bharath Vasani, Nayana Janardanan, Beatriz Prieto-Simón, Anna CifuentesRius, Siobhan Julie Bradley, Eli Moore, Tobias Kraus, and Nicolas H. Voelcker ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.5b08765 • Publication Date (Web): 02 Dec 2015 Downloaded from http://pubs.acs.org on December 5, 2015

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ACS Applied Materials & Interfaces

Microwave

Heating

of

Poly(N-

isopropylacrylamide)-Conjugated Nanoparticles

for

Gold

Temperature-Controlled

Display of Concanavalin A Roshan B. Vasani, † Nayana Janardanan, † Beatriz Prieto-Simón, † Anna Cifuentes-Rius, † Siobhan J. Bradley,‡ Eli Moore, † Tobias Kraus§ and Nicolas H. Voelcker *,† †

ARC Centre of Excellence in Convergent Bio-Nano Science and Technology, Future

Industries Institute, University of South Australia, SA 5095, Australia. ‡

§

Future Industries Institute, University of South Australia, SA 5095, Australia INM–Leibniz Institute for New Materials, Campus D2 2, 66123, Germany

KEYWORDS: microwave heating, gold nanoparticles, poly(N-isopropylacrylamide), concanavalin A, controlled display

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ABSTRACT. We demonstrate microwave-induced heating of gold nanoparticles and nanorods. An appreciably higher and concentration-dependent microwave-induced heating rate was observed with aqueous dispersions of the nanomaterials as opposed to pure water and other controls. Grafted with the thermo-responsive polymer poly(Nisopropylacrylamide), these gold nanomaterials react to microwave-induced heating with a conformational change in the polymer shell, leading to particle aggregation. We subsequently covalently immobilize concanavalin A (Con A) on the thermo-responsive gold nanoparticles. Con A is a bio-receptor commonly used in bacterial sensors due to its affinity for carbohydrates on bacterial cell surfaces. The microwave-induced thermal transitions of the polymer reversibly switch on and off the display of Con A on the particle surface and hence the interactions of the nanomaterials with carbohydratefunctionalized surfaces. This effect was determined using linear sweep voltammetry on a methyl-α-D-mannopyranoside functionalized electrode.

1. INTRODUCTION Remote heating of gold nanomaterials has been studied for several potential applications in the medical and biotechnology fields, including cancer therapy,1-7 controlled drug and gene delivery,8-15 and targeted bactericidal applications.16, 17 Remote heating is advantageous for non-invasive and localized in vivo therapies and can be induced by lasers and ultrasonic or electromagnetic fields. A common application is photothermal cancer therapy using lasers. Recent work has focused on the use of radio waves 5, 18-23 mainly because radio waves can penetrate tens of centimeters into the body.5

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The mechanisms underlying radio frequency heating of nanomaterials are not well understood. A recent review classified the literature based on the frequency of radio waves used and distinguished microwave (µ-wave) heating and radio frequency (RF) heating.20 Most of the recent literature in the field focuses on RF heating, possibly due to the development of the Kanzius machine by Therm Med LLC.5-7 This RF generator setup was developed for remote heating of gold nanoparticles in cancer therapy. An ongoing and intense debate exists in the literature on whether gold nanoparticles actually heat up in the RF fields or whether the observed thermal changes are the result of heating of the water, salts, etc. present in the systems.19, 20, 24, 25 The pioneering paper in the field by Hamad-Schifferli et al.21 demonstrated the use of µ-waves to heat gold nanoparticles (GNP) and showed that the heating can be used to control the melting of a DNA hairpin loop coupled to the nanoparticles. The loop rehybridized upon switching off the µ-waves and this could also be repeated several times. Other researchers used µ-wave heating of GNP to cause the dissolution or rapid formation of protein aggregates.26-29 Recently, Vedova et al.18 used GNP conjugated to a fluorophore-modified DNA hairpin loop (a molecular beacon) to demonstrate that the melting of the loop in the µ-wave field led to the movement of the fluorophore away from the fluorescence-quenching gold particle, resulting in the emergence of a fluorescence signal. Kabb et al. measured the temperature of the nano-environment of GNP on µ-wave heating using a ‘polymeric thermometer’.30 They found that the local temperature around the GNP increased by up to 70°C compared to the bulk solution temperature, which increased by up to 40°C. However, the temperature differential decreased drastically at a distance of greater than 2 nm away from the particle surface.

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Thermo-responsive gold nanomaterials are applied in several fields including temperature-dependent aggregation and opacity switching,31, 32 tunable arrays,33 actuators and drug delivery vehicles,8, 10, 34 controlled catalysis35, 36 and reversible ligand display.37 Thermo-responsive properties can be imparted to gold nanomaterials by functionalization with, or embedding them in responsive polymers. A commonly used polymer for this purpose is thermo-responsive poly(n-isopropylacrylamide) (PNIPAM), that undergoes volume-phase transitions at 32 – 38°C, its lower critical solution temperature (LCST).38, 39 Below the LCST, PNIPAM behaves like a hydrophilic polymer and forms hydrogen bonds with water, adopting an elongated coiled structure. Above the LCST, intramolecular hydrogen bonds are entropically favored, causing the collapse and subsequent precipitation of the polymer chains in a process that is completely reversible.38 While several studies have concentrated on the application of radio wave heating of GNP, no research has been conducted on combining this heating phenomenon with the versatility of thermo-responsive materials. The combination of µ-wave heating of GNP with temperature-responsive polymers is powerful and can potentially be used for applications such as remote-controlled display of bio-receptors. Mastrotto et al.37 demonstrated a reversible bio-receptor display system using PNIPAM functionalized GNP. They showed that below the LCST, the swollen PNIPAM shells on GNP prevented the interaction of a ligand on the nanoparticle surface with receptors on cell surfaces. Heating above the LCST facilitated the collapse of the polymer chains and concurrent exposure of the bio-receptor. Lectins, such as concanavalin A (Con A), have been used as bio-receptors in bacterial biosensors.40, 41 These carbohydrate-binding proteins bind to sugars, glycoproteins and glycolipids.42

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Thermal switching of PNIPAM-coated GNP via µ-waves can be used for on-demand spatial and temporal display of Con A. Here, we demonstrate the effective heating of thermo-responsive GNP and gold nanorods (GNR) with µ-waves. We then use this remote heating strategy to control the display of Con A and establish that the nanoparticle constructs can effectively bind carbohydrates in a remote-controlled temperature-responsive and reversible fashion, as a proof of principle to demonstrate the on-demand binding of GNP to cell surface receptors. These nanoparticle constructs could be used for diagnostic and therapeutic applications in the future.

2. EXPRIMENTAL SECTION 2.1. Materials Dimethyl formaldehyde (DMF), hydrochloric acid (AR grade), chloroauric acid (HAuCl4), 2 2’-azobisisobutyronitrile (AIBN), sodium citrate, hydrazine monohydrate, Con A, bovine serum albumin (BSA), methyl-α-D-mannopyranoside, divinyl sulfone, cysteamine hydrochloride, mercaptoethanol, as well as the components of buffers (2-(Nmorpholino)-ethanesulfonic acid (MES), phosphate buffered saline (PBS) tablets, sodium carbonate and sodium bicarbonate were all obtained from Sigma-Aldrich (Australia). Diethyl ether (AR grade), nitric acid (70%), Sodium borohydride and sulphuric acid (70%, AR grade) were obtained from Merck, Australia. Acetone and n-hexane (AR grade) were from Ajax Finechem Pty Ltd., Australia and ethanol (AR grade) from Chem Supply, Australia. All these chemicals were used as received without further purification. The NI™ (Non-Interfering™) Protein Assay was from G-biosciences. Screen-printed

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gold electrodes were purchased from DropSens (Spain, ref. 250BT). 2-propanoic acid butyl trithiocarbonate (PABTC) (from Prof. Sebastien Perrier, Key Centre for Polymer Colloids, University of Sydney) was used as received without further purification. Nisopropylacrylamide (NIPAM, Sigma-Aldrich, Australia) was recrystallized from nhexane prior to use. 2.2. Fourier transform infra-red microscopy (FTIR) Spectra were recorded using a Hyperion 1000 FTIR microscope (Bruker Pty. Ltd.) coupled to a mercury-cadmium-telluride (MCT) detector, cooled with liquid nitrogen, in transmission mode. The spectra collected were averages of 64 scans recorded at a resolution of 4 cm-1. Silicon was used as the background. The data was processed using the OPUS 7.2 software. 2.3. Gel permeation chromatography (GPC) Absolute molecular weight measurements of synthesized polymer was performed on a Viscotek GPCmax VE2001 GPC coupled to a Viscotek TDA 305 triple detector array system (Malvern Instruments Ltd, UK) equipped with refractive index, viscometry and light scattering detectors. The detectors were calibrated using a 70 kDa polystyrene standard using tetrahydrofuran (THF) as the eluent. Two Agilent PLgel 5 µm mixed C columns were used for the analysis. 2.4. UV/Vis spectrophotometry An Agilent 8453 UV-Visible spectrophotometer fitted with an Agilent Peltier Temperature Controller (89090A, Agilent, Australia) and a Nanodrop 2000 (Thermo Scientific, Australia) were used to measure UV absorbances. 2.5. Dynamic light scattering (DLS)

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A Malvern Zetasizer nano ZS instrument was used. All the measurements were carried out at 25°C or 50°C with a 60 s equilibration time. Spectra were analyzed by Zetasizer software (7.01 version). 2.6. µ-wave heating system A Wavetek 0.2 – 1100 MHz synthesized signal generator model 2500A coupled to a Lucent SRFU18 RF power amplifier module and a Thruline wattmeter were used to generate the µ-waves in a solenoid of coil length 3 cm and diameter 1.5 cm. All suspensions were exposed to µ-waves of 1 GHz frequency and 18 W power. The heating experiments were carried out in 0.5 mL Eppendorf tubes. A digital multimeter (Digitech QM1575) was used to measure the temperature of the dispersions. IR images were obtained on an FLIR i7 Infra-red Camera (FLIR systems) by placing the camera perpendicular to the surface of the gold dispersions in the Eppendorf tubes and recording a video in the IR spectrum. 2.7. Transmission electron microscopy (TEM) TEM images were obtained using a 200 kV JEOL 2100F (JEOL, Japan) transmission electron microscope operated at 200 kV. Conventional Formvar-coated copper grids of 3 mm diameter were used for sample preparation. A 10 µL drop of the gold nanomaterial dispersions were deposited on the grid and allowed to sit for 10 min. Following this, the excess solution was removed with an absorbent wipe and the grid was allowed to dry. 2.8. Electrochemical measurements Electrochemical measurements were performed on an electrochemical analyzer (CH Instruments, model 600D series) using a three-electrode electrochemical cell. Data

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acquisition and analysis were accomplished using CH Instruments software (CH Instruments, Inc., Austin, TX, US). 2.9. Synthesis of gold nanoparticles GNP of 10 nm diameter with 20% polydispersity (standard deviation of diameter divided by mean diameter) were prepared by chemical reduction. All the glassware used was washed in Aqua Regia (nitric acid: hydrochloric acid in a 1:3 volume ratio) followed by Milli-Q water (resistivity of 18.2 MΩ cm) and dried in an oven at 90°C. Cold Milli-Q water (4°C, 100 mL) was poured into a flask kept on ice and stirred. HAuCl4 (254 µL, 0.1M) was added and stirred for 5 min. Freshly prepared sodium citrate solution (1 mL, 1% w/v in Milli-Q water) was added gradually with stirring. Reduction was conducted at room temperature by quickly adding sodium borohydride solution (1 mL, 0.075% w/v NaBH4 in 1% w/v sodium citrate) to the reaction mixture with a fast stirring rate. The solution turned red instantly upon adding the reducing agent. No further purification steps were performed. The concentration of the GNP dispersion was determined by UV spectroscopy by measuring the maximum absorbance of the surface plasmon resonance (SPR) band using a method described in the literature.43 GNR with a length of 140 nm (10% polydispersity) and a diameter of approximately 62 nm (18% polydispersity) (geometry from SEM, sample size 30) were synthesized using a protocol adapted from Murray et al.44 Briefly, we first prepared a suspension of seed particles by mixing 5 mL of an aqueous solution of 0.5 mM HAuCl4 with 5 mL of an aqueous solution of 0.2 M CTAB. A freshly prepared solution of 0.005 M NaBH4 was added under continuous stirring. The color changed from yellow to brownish yellow after

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approximately 2 min. This seed solution was aged for 30 min and added to a growth solution. To prepare the growth solution, 7 g of CTAB (0.037 M CTAB in the final growth solution) and 1.234 g sodium oleate were dissolved in 250 mL water at approximately 50°C. 18 mL of an aqueous 4 mM AgNO3 was added after the solution had cooled to 30°C and the mixture was kept at this temperature for 15 min. While stirring, 250 mL of an aqueous 1 mM HAuCl4 was added and stirred at 700 rpm for 90 min. The solution became colorless, and 1.5 ml HCl (37 wt. %) was added and stirred for 15 min at 400 rpm. An amount of 1.25 mL of 0.064 M aqueous solution of ascorbic acid was added under fast stirring. This growth solution was mixed with 0.4 mL of seed solution under rapid stirring and kept at 30°C for more than 12 h to ensure that all precursors had been deposited on the seed particles. The particles were centrifuged down at 7,000 rpm for 30 min, the pellet was suspended in 10 mL distilled water and stored in the fridge. Particles were used without further purification. The concentration of the GNR was determined following a protocol described in the literature.45

2.10. Synthesis of PNIPAM by RAFT polymerization NIPAM (500 mg, 4.42 x 10-3 mol), PABTC (13.8 mg, 5.8 x 10-5 mol) and AIBN (9.5 mg, 5.8 x 10-5 mol) were combined with nitrogen purged DMF (5 mL) in a sealed flask under constant stirring and the reaction mixture was purged with nitrogen for 30 min. An initial sample (0.1 mL) was taken using a degassed syringe. Immediately afterwards, the flask was immersed in a preheated oil bath set to 70°C with stirring at 400 rpm. Kinetic

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samples (0.1 mL) were taken out at definite intervals using a degassed syringe to analyze conversions and reaction rates. The polymerization was quenched after 24 h by removal from the oil bath and exposure to air. Polymer samples were purified by precipitation into diethyl ether from DMF twice and were dried in an oven at 60°C overnight. Heterotelechelic α-thiol-ω-carboxy terminated PNIPAM (HS-PNIPAM-COOH) was produced by aminolysis of the thiocarbonylthio end group of the polymer using hydrazine monohydrate. A two-fold molar excess of hydrazine monohydrate (relative to polymer) was added to 5 mL of polymer in DMF solution and heated to 40°C for 40 min in a glove box with constant stirring. The carboxyl group on the polymer comes from the R-group of the chain transfer agent. Following the reaction, the HS-PNIPAM-COOH was isolated by precipitation into diethyl ether. 2.11. Procedure for grafting of HS-PNIPAM-COOH on gold nanomaterials An aqueous solution of HS-PNIPAM-COOH (25 mg/mL) was added to 2 mL of GNP or GNR dispersions (0.08 mM). The reaction was allowed to proceed for a week, where the polymer bound to the gold via the thiol end group. The polymer-coated gold nanoparticles were purified by centrifuging at 2000 rpm for 2 min using centrifuge filters (10,000 MW cut-off; Sartorius Stedim Biotech, Vivaspin 2). The temperature during centrifugation was maintained below 10°C to avoid precipitation of polymer. The PNIPAM-GNP and PNIPAM-GNR were resuspended in water and centrifuged again. This step was repeated 5-6 times to ensure complete removal of any unbound polymer. 2.12. Measurement of LCST of PNIPAM The LCST of the PNIPAM and PNIPAM-GNP was determined by measuring the transmission of 1 mg/mL aqueous solutions of PNIPAM on a UV-Vis spectrometer using

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a heating rate of 0.5°C/min and 1 min equilibration time. The transmission measurements were made from 25°C to 70°C. The sigmoidal curve obtained was used to identify the LCST of PNIPAM. 2.13. Preparation of Con A-modified GNP, PNIPAM-GNP and PNIPAM-GNR Prior to its use, Con A was activated by incubation for 6 h in 0.1 M phosphate buffered saline (PBS) at pH 7 supplemented with 0.1 M KCl, 0.1 mM CaCl2 and 0.1 mM MnCl2. Ca2+ and Mn2+ ions are required to provide Con A with its proper structure and function.46 Con A was covalently bound to PNIPAM-GNP and PNIPAM-GNR. The carboxyl terminal groups of PNIPAM were activated by incubating PNIPAM-GNP and PNIPAMGNR in a 32 mM EDC and 42 mM NHS solution in 0.1 M MES buffer, pH 4.5, for 30 min. A 30 min-centrifugation step at 21,500 rpm and 4°C was performed to eliminate the excess of EDC and NHS. Activated particles were re-suspended in 8 mg /mL Con A solution to allow covalent binding during 1 h-incubation at room temperature. An additional 1 h 30 min centrifugation at 21,500 rpm was required to eliminate the excess of unbound Con A. Con A-modified particles were re-suspended in 0.1 M PBS. GNP with adsorbed Con A were prepared by incubating GNP lacking PNIPAM in a 15 µg/mL solution of Con A for 2 h in a 0.2 M disodium phosphate – 0.1 M citric acid buffer solution at pH 6. The particles were centrifuged at 12,800 rpm for 30 min to separate them from the excess Con A and resuspended in 0.1 M PBS. A colorimetric protein assay was performed to corroborate the modification of the gold nanomaterials with covalently bound Con A. The assay was performed in triplicate, using BSA as protein standard. A Universal Protein Precipitating Agent (UPPA™) was added to several dilutions of the prepared Con A modified nanomaterials to precipitate proteins.

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After centrifugation at 10,000 rpm for 5 min, the supernatant was removed. The nanoparticles were re-suspended in a copper alkaline solution: the copper ions bind to the protein, while the unbound copper ions absorb at 480 nm. The measured absorbance values were inversely proportional to the amount of protein. 2.14. Procedure for heating of gold nanomaterials using µ-waves Dispersions of GNP or GNR in a 0.5 mL Eppendorf tube were placed in the solenoid coil attached to the µ-wave heating system. Initial temperature was noted using a digital multimeter. All dispersions were exposed to 18 W of µ-wave power at 1 GHz. The temperature was recorded every 2 min for 10 min using the digital multimeter. 2.15. Electrode preparation and saccharide modification Gold electrodes were electrochemically cleaned in 0.5 M H2SO4 by scanning the potential between 0 and +1.6 V at 100 mV/s for eight cycles. Clean gold electrodes were exposed overnight at 4°C to 20 µL of 1 mM aqueous cysteamine solution to introduce amine groups on the electrode surface. After modification, the electrodes were rinsed with water to remove weakly adsorbed molecules. To block the vacant places within the self-assembled monolayer, a 1 h-incubation with 1 mM mercaptoethanol was performed. Amino groups of the bound cysteamine were activated using a 30 min-incubation with 10% divinyl sulfone (v/v) in 0.1 M carbonate buffer, pH 9.6.47 Activated amino groups were incubated with a 0.5 M methyl-α-D-mannopyranoside solution in carbonate buffer to immobilize the saccharide onto the electrode surface. The modified electrodes were blocked by 1 h-incubation with 10% BSA solution (m/v) in PBS. 2.16. Electrochemical detection protocol for Con A-saccharide binding

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GNP can be electrochemically detected by (a) direct detection based on stripping voltammetry, or (b) indirect detection of the gold ions released after acidic dissolution.48 Here, we use the direct electrochemical detection of GNP via linear sweep voltammetry (LSV). Determination of the electrochemical oxidation of gold nanoparticles to AuCl4was facilitated by the large surface area and the availability of many oxidizable gold atoms in each nanoparticle. 20 µL of Con A-modified PNIPAM-GNP or PNIPAM-GNR were incubated under different conditions (temperature and time) onto the saccharidemodified electrodes. Upon incubation, electrodes were thoroughly washed with PBS prior to the electrochemical detection of the nanoparticles bound by means of lectincarbohydrate interactions. LSV measurements were performed between -0.3 and +1.7 V (vs. Ag/AgCl) at 0.05 V/s in 0.1 M H2SO4. The first LSV was recorded for each electrode, and three electrodes were used for each temperature and incubation time. LSV data were corrected by subtraction of the voltammograms obtained prior to incubation with Con A modified gold nanomaterials. The presence of an oxidation peak between +0.9 and +1.0 V was assigned to gold nanomaterials bound to the carbohydrate sensor surface through affinity interactions.

3. RESULTS AND DISCUSSIONS In the following sections of this report, we describe the fabrication of PNIPAMfunctionalized thermo-responsive gold nanomaterials including GNP and their modification with Con A (Figure 1A). We then examine the effect of the µ-wave irradiation on the gold nanomaterials and demonstrate the application of this system for

µ-wave controlled display of Con A (Figure 1B).

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Figure 1. A) Schematic representation of the fabrication procedure to prepare Con Amodified thermo-responsive GNP. Citrate-capped GNP were incubated with heterotelechelic PNIPAM (HS-PNIPAM-COOH) to form the thermo-responsive polymer coating. The carboxy functionality on the PNIPAM-GNP was then used to immobilize Con A via EDC/NHS chemistry. A similar procedure was used for GNR. B) Illustration of the µ-wave controlled Con A display on GNP. In the absence of the µ-waves, the expanded polymer prevents the interaction of the Con A with a methyl-α-Dmannopyranoside-functionalized electrode. Upon irradiation with µ-waves, the GNP heat up and cause the collapse of the PNIPAM layer, resulting in exposure of the Con A and binding to the electrode surface.

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3.1. Synthesis and characterization of gold nanomaterials. GNP of 10 nm diameter were prepared via chemical reduction of HAuCl4 with NaBH4 in the presence of sodium citrate. GNR of approximate dimensions 140 nm x 62 nm were also used to study the effect of nanoparticle geometry on the heating properties in µ-wave fields. Figure 2a, c display TEM and HR-TEM images of the GNP and GNR samples prior to PNIPAM modification. The polymerization of NIPAM was performed using reversible-addition fragmentation chain transfer (RAFT) polymerization with PABTC as chain transfer agent and AIBN as the initiator. RAFT polymerization was used in order to obtain polymers with controlled molecular weight and low polydispersity index. Figure 3a shows the GPC trace of the PNIPAM polymer showing a Mn of 6,320 g/mol with a low polydispersity index of 1.13, characteristic of RAFT polymerization. The lower critical solution temperature (LCST) of the polymer was estimated by measuring the transmittance of the solution on heating between 25°C and 50°C (Figure 3b). The LCST was found to be 38°C for the as prepared polymer.

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Figure 2. TEM images showing a) GNP, b) PNIPAM-GNP, c) GNR and d) PNIPAMGNR. The insets show high resolution images of the nanomaterials. (Scale bars of a and b = 50 nm, c and d = 100 nm, inset a and b = 10 nm, and inset c and d = 20 nm). Heterotelechelic α-thiol-ω-carboxy terminated PNIPAM (HS-PNIPAM-COOH) was produced by aminolysis of the thiocarbonylthio end group on the polymer chains using hydrazine monohydrate. The carboxyl group present at the other end of the polymer chain stems from the R-group of the PABTC. Figure 3c shows the UV spectra of the PNIPAM chains in solution before and after aminolysis. Prior to the reaction, the dithioester group present in PABTC showed a strong absorbance at 306 nm due to the π-π* transition of

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the thiocarbonyl bond.49, 50 During aminolysis, the dithioester group was converted to a thiol group, leading to the disappearance of the peak upon completion of aminolysis. The resulting polymer was then mixed with dispersions of citrate-capped GNP and GNR to start the ligand exchange reaction. This reaction proceeded during one week under constant stirring, following the protocol described by Zhu et al.31 Once completed, unreacted polymer was removed from the GNP and GNR by multiple centrifugal filtration steps. TEM images of the PNIPAM-modified nanomaterials were captured at low and high magnifications and are displayed in Figure 2b and d. In the insets, a corona of polymer is clearly visible around the modified nanomaterials, measuring 1.6 +/- 0.3 nm on the PNIPAM-GNP samples and 4.9 +/- 0.5 nm on the PNIPAM-GNR samples.

Figure 3. a) GPC trace of the synthesized PNIPAM, b) LCST measurements of heterotelechelic PNIPAM before aminolysis, PNIPAM-GNP and Con A-PNIPAM-GNP, c) absorbance of heterotelechelic PNIPAM solution (in the absence of GNP) before and after aminolysis showing the disappearance of the peak at 306 nm and d) FTIR of (i) PNIPAM-GNP and (ii) PNIPAM-GNR.

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FTIR spectroscopy was used to further confirm the functionalization of the GNP and GNR with PNIPAM. Figure 3d(i) and (ii) show the IR traces of the functionalized GNP and GNR, respectively. Characteristic peaks at 1556 cm-1, 1653 cm-1 and 3320 cm-1 were observed that correspond to the amide I and amide II bands and the N-H stretching vibration mode of the amide, respectively. Bands at 1374 cm-1 and 1390 cm-1 were attributed to the symmetrical deformation of the isopropyl group of PNIPAM. A set of three peaks between 2900 and 3000 cm-1, as well as, the peak at 1463 cm-1 correspond to the C-H vibration modes.51 Indirect confirmation of successful PNIPAM functionalization of the GNP was obtained by studying the LCST transition of the polymer coated GNP. We observed a reduction in the transition temperature of the grafted polymer as compared to free polymer (35°C instead of 38°C) (Figure 3b). This reduction in transition temperature has been previously reported in the literature.31, 52 Gibson et al. suggested that the difference in the mass fraction between the nanoparticles and the grafted polymer affects the stability of the colloid and results in a reduction of the temperature at which the aggregation occurs.52 Additionally, an increase in the LCST upon Con A modification of the PNIPAM-GNP to 41°C was also observed (Figure 3b). This change can be attributed to the hydrophilicity of the bulky end group which can alter the LCST of PNIPAM.53 3.2. µ-wave heating of GNP. The capability of the µ-wave field to heat the GNP was tested against several controls including water, a 1 % citrate solution, HAuCl4 in 1 % sodium citrate solution and NaBH4 in 1 % citrate solution. These controls were selected as they were the precursors used to prepare the GNP and may be present in the final dispersion. The solutions were transferred into an Eppendorf tube and placed into the

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centre of the solenoid. Measurements of the temperature were taken every 2 min using a thermocouple. The results, plotted in Figure 4a, indicate that whilst all the tested solutions showed increases in temperature, a clear difference in the heating rate was evident between the GNP sample (2.9°C/min) and the controls (1 µm was observed when the PNIPAM-GNP sample was heated above the LCST of PNIPAM. In contrast, GNP without polymer displayed a hydrodynamic diameter of 11.5 +/- 3.2 nm with no significant change on heating. After removal of the µ-wave source, the dispersion rapidly cooled below the LCST of the polymer and became transparent again (Figure 6d).

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Figure 6. a) µ-wave heating traces showing change in temperature starting from ambient, of GNP, PNIPAM-GNP, GNR and PNIPAM-GNR with particle concentrations of 19.3 nM. Images of PNIPAM-GNP dispersion after b) 0 min, c) 4 min of µ-wave exposure and d) after switching off the µ-wave source. 3.3. Reversible Con A display. An electrochemical assay was set up to demonstrate the potential of µ-wave heating to control the display of a receptor immobilized onto PNIPAM-GNP and PNIPAM-GNR, and thereby regulate the binding of the receptormodified nanomaterials to a carbohydrate ligand-functionalized electrode (concept

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depicted in Figure 1B). First, PNIPAM-GNP and PNIPAM-GNR were modified with the lectin Con A by covalent binding. We performed a colorimetric protein assay to assess the efficiency of the modification protocol. Results showed that both GNP and GNR featured similar concentrations of covalently bound Con A (52 and 56 µg/mL, respectively). Note that TEM images of the Con A-modified PNIPAM-GNP (Con APNIPAM-GNP) showed no observable differences to PNIPAM-GNP (Figure S1).

Con A is a carbohydrate-binding protein with affinity towards α-D-mannosyl and α-Dglucosyl groups, which are commonly present on the membranes of gram negative bacteria. Therefore, cysteamine-modified gold electrodes were activated with divinyl sulfone and reacted with methyl-α-D-mannopyranosideCon A-PNIPAM-GNP and Con A-PNIPAM-GNR were incubated on methyl-α-D-mannopyranoside-modified electrodes for 30 min, either at RT or at 50°C. Linear sweep voltammograms in Figure 7a show an oxidation peak between +0.9 and +1.0 V for the samples incubated at elevated temperature, corresponding to oxidation of gold nanomaterials attached via ligandreceptor interactions onto the electrode surface. This oxidation peak was absent for samples incubated at RT. To demonstrate the role of PNIPAM in the temperaturedependent display of Con A, Con A-GNP were prepared by adsorbing Con A directly onto GNP and incubated with saccharide-modified electrodes below and above the LCST (Figure S2). The particles showed binding to the saccharide-modified surface both at RT and 50˚C. Therefore, Con A-PNIPAM-GNP binding to methyl-α-D-mannopyranoside upon heating (50°C or µ-wave), but not after incubation at RT, can only be attributed to PNIPAM switching. Additionally, we observed that PNIPAM-GNP and PNIPAM-GNR

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with no Con A (negative control) did not bind to the electrodes. We hypothesize that, below the LCST, a large fraction of Con A is buried within the expanded PNIPAM layer and is prevented from interaction with the electrode surface. However, above the LCST, the PNIPAM contracts to form globules on the GNP surface with no space for the Con A to be ‘hidden’, resulting in binding of the Con A-PNIPAM-GNP/GNR to the saccharidemodified electrodes. Next, we investigated if binding of Con A-PNIPAM-GNP and Con A-PNIPAM-GNR could be induced by µ-wave irradiation for 30 s. Voltammograms in Figure 7b clearly show the attachment of the nanomaterials that were exposed for 30 s to µ-wave irradiation, while insignificant signals were detected in the absence of µ-wave irradiation. The µ-wave heating results described in the previous section were based on measuring the temperature changes of the nanomaterial dispersion. We showed that 4 min of µ-wave irradiation were required to raise the temperature of the dispersion above the LCST of PNIPAM (when starting from RT) and induce aggregation of the polymer-modified nanomaterials, which was evident from the dispersion becoming opaque. However, the results of the electrochemical experiments obtained here suggest that the nanomaterials, in fact, heat very rapidly, raising the temperature of their micro-environment above the LCST much faster. This leads to the collapse of the polymer shell and the display of the Con A immobilized on the polymer.

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Figure 7. Linear sweep voltammograms performed between +0.3 and +1.3 V in 0.1 M H2SO4, after incubation of Con A-PNIPAM-GNP (grey) and Con A-PNIPAM-GNR (black) onto methyl-α-D-mannopyranoside-modified electrodes. a) 30 min incubation at RT or at 50°C; and b) 30 s incubation at RT or under µ-wave heating. Voltammograms for controls using unmodified PNIPAM-GNP/GNR have been included as reference. 4. CONCLUSIONS In conclusion, we have studied the heating properties of gold nanomaterials when exposed to µ-wave fields. The gold nanomaterial dispersions show an appreciably higher and concentration-dependent heating rate compared to solutions without the nanomaterials. No noticeable difference in heating rates was observed between GNP and GNR. PNIPAM modification of the gold nanomaterials was successfully achieved and the modified nanomaterials displayed reversible temperature-responsive aggregation properties. We showed that the reversible aggregation of the modified nanomaterials could also be triggered by exposure to µ-wave fields. Furthermore, as proof of principle of the temperature-controlled display of bio-receptors, electrochemical detection of gold nanoparticles was used to prove the binding of Con A-modified PNIPAM-GNP and

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PNIPAM-GNR to carbohydrate-modified electrodes in response to the µ-wave fields. The described nanoparticle constructs exhibiting on-demand display of bioreceptors could be used for applications in diagnosis and therapy in the future.

ASSOCIATED CONTENT Supporting Information. TEM image of Con A-PNIPAM-GNP and linear sweep voltammograms of Con A-GNP. This material is available free of charge via the Internet at http://pubs.acs.org.

AUTHOR INFORMATION Corresponding Author * Tel: +61-8-83025508. Email: [email protected]

Author Contributions All authors have given approval to the final version of the manuscript.

Funding Sources Funding support from the Wound Management Innovation Co-operative Research Centre is kindly acknowledged. NHV kindly acknowledges fellowship support from the Alexander von Humboldt Foundation.

Notes The authors declare no competing financial interest.

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ACKNOWLEDGMENT The authors would like to thank Marc Cirera for the graphical illustrations in Figure 1 and the TOC and Dr. Nobuyuki Kawashima for help with the acquisitions of the TEM images.

REFERENCES (1)

Wang, Y.; Black, K. C. L.; Luehmann, H.; Li, W.; Zhang, Y.; Cai, X.; Wan, D.;

Liu, S.-Y.; Li, M.; Kim, P.; Li, Z.-Y.; Wang, L. V.; Liu, Y.; Xia, Y. Comparison Study of Gold Nanohexapods, Nanorods, and Nanocages for Photothermal Cancer Treatment. ACS Nano 2013, 7 (3), 2068-2077. (2)

Choi, W.; Sahu, A.; Kim, Y.; Tae, G. Photothermal Cancer Therapy and Imaging

Based on Gold Nanorods. Ann Biomed Eng 2012, 40 (2), 534-546. (3)

Huang, X.; El-Sayed, M. A. Gold Nanoparticles: Optical Properties and

Implementations in Cancer Diagnosis and Photothermal Therapy. J. Adv. Res. 2010, 1 (1), 13-28. (4)

Jain, S.; Hirst, D. G.; O'Sullivan, J. M. Gold Nanoparticles as Novel Agents for

Cancer Therapy. The British Journal of Radiology 2012, 85 (1010), 101-113. (5)

Kruse, D. E.; Stephens, D. N.; Lindfors, H. A.; Ingham, E. S.; Paoli, E. E.;

Ferrara, K. W. A Radio-Frequency Coupling Network for Heating of Citrate-Coated Gold Nanoparticles for Cancer Therapy: Design and Analysis. Ieee Transactions on BioMedical Engineering 2011, 58 (7), 2002-2012.

30


Page 30 of 38

Page 31 of 38

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(6)

Glazer, E. S.; Curley, S. A. Radiofrequency Field-Induced Thermal Cytotoxicity

in Cancer Cells Treated with Fluorescent Nanoparticles. Cancer 2010, 116 (13), 32853293. (7)

Glazer, E. S.; Zhu, C.; Massey, K. L.; Thompson, C. S.; Kaluarachchi, W. D.;

Hamir, A. N.; Curley, S. A. Noninvasive Radiofrequency Field Destruction of Pancreatic Adenocarcinoma Xenografts Treated with Targeted Gold Nanoparticles. Clin. Cancer Res. 2010, 16 (23), 5712-5721. (8)

Santos, G. M.; Zhao, F.; Zeng, J.; Shih, W.-C. Characterization of Nanoporous

Gold Disks for Photothermal Light Harvesting and Light-Gated Molecular Release. Nanoscale 2014, 6 (11), 5718-5724. (9)

Terentyuk, G.; Panfilova, E.; Khanadeev, V.; Chumakov, D.; Genina, E.;

Bashkatov, A.; Tuchin, V.; Bucharskaya, A.; Maslyakova, G.; Khlebtsov, N.; Khlebtsov, B. Gold Nanorods with a Hematoporphyrin-Loaded Silica Shell for Dual-Modality Photodynamic and Photothermal Treatment of Tumors in Vivo. Nano Res. 2014, 7 (3), 325-337. (10) Pissuwan, D.; Niidome, T.; Cortie, M. B. The Forthcoming Applications of Gold Nanoparticles in Drug and Gene Delivery Systems. J. Controlled Release 2011, 149 (1), 65-71. (11) Everts, M.; Saini, V.; Leddon, J. L.; Kok, R. J.; Stoff-Khalili, M.; Preuss, M. A.; Millican, C. L.; Perkins, G.; Brown, J. M.; Bagaria, H.; Nikles, D. E.; Johnson, D. T.; Zharov, V. P.; Curiel, D. T. Covalently Linked Au Nanoparticles to a Viral Vector: Potential for Combined Photothermal and Gene Cancer Therapy. Nano Lett. 2006, 6 (4), 587-591.

31



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(12) Poon, L.; Zandberg, W.; Hsiao, D.; Erno, Z.; Sen, D.; Gates, B. D.; Branda, N. R. Photothermal Release of Single-Stranded DNA from the Surface of Gold Nanoparticles through Controlled Denaturating and Au−S Bond Breaking. ACS Nano 2010, 4 (11), 6395-6403. (13) Alkilany, A. M.; Thompson, L. B.; Boulos, S. P.; Sisco, P. N.; Murphy, C. J. Gold Nanorods: Their Potential for Photothermal Therapeutics and Drug Delivery, Tempered by the Complexity of Their Biological Interactions. Adv. Drug Delivery Rev. 2012, 64 (2), 190-199. (14) Bikram, M.; Gobin, A. M.; Whitmire, R. E.; West, J. L. Temperature-Sensitive Hydrogels with Sio2–Au Nanoshells for Controlled Drug Delivery. J. Controlled Release 2007, 123 (3), 219-227. (15) de Puig, H.; Cifuentes Rius, A.; Flemister, D.; Baxamusa, S. H.; HamadSchifferli, K. Selective Light-Triggered Release of DNA from Gold Nanorods Switches Blood Clotting on and Off. PLoS One 2013, 8 (7), e68511. (16) Huang, W.-C.; Tsai, P.-J.; Chen, Y.-C. Functional Gold Nanoparticles as Photothermal Agents for Selective-Killing of Pathogenic Bacteria. Nanomedicine 2007, 2 (6), 777-787. (17) Zharov, V. P.; Mercer, K. E.; Galitovskaya, E. N.; Smeltzer, M. S. Photothermal Nanotherapeutics and Nanodiagnostics for Selective Killing of Bacteria Targeted with Gold Nanoparticles. Biophys. J. 2006, 90 (2), 619-627. (18) Vedova, P. D.; Ilieva, M.; Zhurbenko, V.; Mateiu, R.; Faralli, A.; Dufva, M.; Hansen, O. Gold Nanoparticle-Based Sensors Activated by External Radio Frequency Fields. Small 2015, 11 (2), 248-256.

32


Page 32 of 38

Page 33 of 38

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(19) Sassaroli, E.; Li, K. C. P.; Neill, B. E. O. Radio Frequency Absorption in Gold Nanoparticle Suspensions: A Phenomenological Study. J. Phys. D: Appl. Phys. 2012, 45 (7), 075303. (20) Collins, C. B.; McCoy, R. S.; Ackerson, B. J.; Collins, G. J.; Ackerson, C. J. Radiofrequency Heating Pathways for Gold Nanoparticles. Nanoscale 2014, 6 (15), 8459-8472. (21) Hamad-Schifferli, K.; Schwartz, J. J.; Santos, A. T.; Zhang, S.; Jacobson, J. M. Remote Electronic Control of DNA Hybridization through Inductive Coupling to an Attached Metal Nanocrystal Antenna. Nature 2002, 415 (6868), 152-155. (22) Cardinal, J.; Klune, J. R.; Chory, E.; Jeyabalan, G.; Kanzius, J. S.; Nalesnik, M.; Geller, D. A. Noninvasive Radiofrequency Ablation of Cancer Targeted by Gold Nanoparticles. Surgery 2008, 144 (2), 125-132. (23) Corr, S. J.; Raoof, M.; Mackeyev, Y.; Phounsavath, S.; Cheney, M. A.; Cisneros, B. T.; Shur, M.; Gozin, M.; McNally, P. J.; Wilson, L. J.; Curley, S. A. Citrate-Capped Gold Nanoparticle Electrophoretic Heat Production in Response to a Time-Varying Radio-Frequency Electric Field. J. Phys. Chem. C 2012, 116 (45), 24380-24389. (24) Kim, H. K.; Hanson, G. W.; Geller, D. A. Are Gold Clusters in Rf Fields Hot or Not? Science 2013, 340 (6131), 441-442. (25) Li, D.; Jung, Y. S.; Tan, S.; Kim, H. K.; Chory, E.; Geller, D. A. Negligible Absorption of Radiofrequency Radiation by Colloidal Gold Nanoparticles. J. Colloid Interface Sci. 2011, 358 (1), 47-53.

33



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(26) Kogan, M. J.; Bastus, N. G.; Amigo, R.; Grillo-Bosch, D.; Araya, E.; Turiel, A.; Labarta, A.; Giralt, E.; Puntes, V. F. Nanoparticle-Mediated Local and Remote Manipulation of Protein Aggregation. Nano Lett. 2006, 6 (1), 110-115. (27) Bastus, N. G.; Kogan, M. J.; Amigo, R.; Grillo-Bosch, D.; Araya, E.; Turiel, A.; Labarta, A.; Giralt, E.; Puntes, V. F. Gold Nanoparticles for Selective and Remote Heating of Beta-Amyloid Protein Aggregates. Mater. Sci. Eng., C 2007, 27 (5–8), 12361240. (28) Araya, E.; Olmedo, I.; Bastus, N. G.; Guerrero, S.; Puntes, V. F.; Giralt, E.; Kogan, M. J. Gold Nanoparticles and Microwave Irradiation Inhibit Beta-Amyloid Amyloidogenesis. Nanoscale Res. Lett. 2008, 3 (11), 435-443. (29) Aslan, K.; Geddes, C. D. Microwave-Accelerated Ultrafast Nanoparticle Aggregation Assays Using Gold Colloids. Anal. Chem. 2007, 79 (5), 2131-2136. (30) Kabb, C. P.; Carmean, R. N.; Sumerlin, B. S. Probing the Surface-Localized Hyperthermia of Gold Nanoparticles in a Microwave Field Using Polymeric Thermometers. Chem. Sci. 2015, 6 (10), 5662-5669. (31) Zhu, M.-Q.; Wang, L.-Q.; Exarhos, G. J.; Li, A. D. Q. Thermosensitive Gold Nanoparticles. J. Am. Chem. Soc. 2004, 126 (9), 2656-2657. (32) Yusa, S.-i.; Fukuda, K.; Yamamoto, T.; Iwasaki, Y.; Watanabe, A.; Akiyoshi, K.; Morishima, Y. Salt Effect on the Heat-Induced Association Behavior of Gold Nanoparticles Coated with Poly(N-Isopropylacrylamide) Prepared Via Reversible Addition−Fragmentation Chain Transfer (Raft) Radical Polymerization. Langmuir 2007, 23 (26), 12842-12848.

34


Page 34 of 38

Page 35 of 38

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(33) Karg, M.; Hellweg, T.; Mulvaney, P. Self-Assembly of Tunable Nanocrystal Superlattices Using Poly-(Nipam) Spacers. Adv. Funct. Mater. 2011, 21 (24), 4668-4676. (34) Sershen, S. R.; Mensing, G. A.; Ng, M.; Halas, N. J.; Beebe, D. J.; West, J. L. Independent Optical Control of Microfluidic Valves Formed from Optomechanically Responsive Nanocomposite Hydrogels. Adv. Mater. 2005, 17 (11), 1366-1368. (35) Wang, Y.; Wei, G.; Wen, F.; Zhang, X.; Zhang, W.; Shi, L. Synthesis of Gold Nanoparticles Stabilized with Poly(N-Isopropylacrylamide)-Co-Poly(4-Vinyl Pyridine) Colloid and Their Application in Responsive Catalysis. J. Mol. Catal. A: Chem. 2008, 280 (1–2), 1-6. (36) Jiang, X.; Xiong, D. A.; An, Y.; Zheng, P.; Zhang, W.; Shi, L. Thermoresponsive Hydrogel of Poly(Glycidyl Methacrylate-Co-N-Isopropylacrylamide) as a Nanoreactor of Gold Nanoparticles. J. Polym. Sci., Part A: Polym. Chem. 2007, 45 (13), 2812-2819. (37) Mastrotto, F.; Caliceti, P.; Amendola, V.; Bersani, S.; Magnusson, J. P.; Meneghetti, M.; Mantovani, G.; Alexander, C.; Salmaso, S. Polymer Control of Ligand Display on Gold Nanoparticles for Multimodal Switchable Cell Targeting. Chem. Commun. 2011, 47 (35), 9846-9848. (38) Schild, H. G. Poly (N-Isopropylacrylamide): Experiment, Theory and Application. Prog. Polym. Sci. 1992, 17 (2), 163-249. (39) Vasani, R. B.; Cole, M. A.; Ellis, A. V.; Voelcker, N. H., Stimulus-Responsive Polymers at Nano-Interfaces. In Nanomaterials for Life Sciences: Polymeric Nanomaterials, Kumar, C. S. S. R., Ed. Wiley-VCH: Weinheim, Germany, 2011; Vol. 10, pp 59 - 103.

35



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(40) Shen, Z.; Huang, M.; Xiao, C.; Zhang, Y.; Zeng, X.; Wang, P. G. Nonlabeled Quartz Crystal Microbalance Biosensor for Bacterial Detection Using Carbohydrate and Lectin Recognitions. Anal. Chem. 2007, 79 (6), 2312-2319. (41) Ertl, P.; Mikkelsen, S. R. Electrochemical Biosensor Array for the Identification of Microorganisms Based on Lectin−Lipopolysaccharide Recognition. Anal. Chem. 2001, 73 (17), 4241-4248. (42) Disney, M. D.; Seeberger, P. H. The Use of Carbohydrate Microarrays to Study Carbohydrate-Cell Interactions and to Detect Pathogens. Chemistry & Biology 2004, 11 (12), 1701-1707. (43) Liu, X.; Atwater, M.; Wang, J.; Huo, Q. Extinction Coefficient of Gold Nanoparticles with Different Sizes and Different Capping Ligands. Colloids Surf., B 2007, 58 (1), 3-7. (44) Ye, X.; Zheng, C.; Chen, J.; Gao, Y.; Murray, C. B. Using Binary Surfactant Mixtures to Simultaneously Improve the Dimensional Tunability and Monodispersity in the Seeded Growth of Gold Nanorods. Nano Lett. 2013, 13 (2), 765-771. (45) Orendorff, C. J.; Murphy, C. J. Quantitation of Metal Content in the SilverAssisted Growth of Gold Nanorods. J. Phys. Chem. B 2006, 110 (9), 3990-3994. (46) Kashimoto, E.; Sazaki, G.; Hasegawa, K.; Nakada, T.; Miyashita, S.; Komatsu, H.; Sato, K.; Matsuura, Y.; Tanaka, H. Crystallization Studies on a Concanavalin a Crystal with High-Index Faces. J. Cryst. Growth 1998, 186 (3), 461-470. (47) Bucur, B.; Danet, A. F.; Marty, J.-L. Versatile Method of Cholinesterase Immobilisation Via Affinity Bonds Using Concanavalin a Applied to the Construction of a Screen-Printed Biosensor. Biosens. Bioelectron. 2004, 20 (2), 217-225.

36


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Page 37 of 38

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(48) Castañeda, M. T.; Alegret, S.; Merkoçi, A. Electrochemical Sensing of DNA Using Gold Nanoparticles. Electroanalysis 2007, 19 (7-8), 743-753. (49) Li, M.; De, P.; Gondi, S. R.; Sumerlin, B. S. End Group Transformations of RaftGenerated Polymers with Bismaleimides: Functional Telechelics and Modular Block Copolymers. J. Polym. Sci., Part A: Polym. Chem. 2008, 46 (15), 5093-5100. (50) Willcock, H.; O'Reilly, R. K. End Group Removal and Modification of Raft Polymers. Polym. Chem. 2010, 1 (2), 149-157. (51) Vasani, R. B.; McInnes, S. J. P.; Cole, M. A.; Jani, A. M. M.; Ellis, A. V.; Voelcker, N. H. Stimulus-Responsiveness and Drug Release from Porous Silicon Films Atrp-Grafted with Poly(N-Isopropylacrylamide). Langmuir 2011, 27 (12), 7843-7853. (52) Gibson, M. I.; Paripovic, D.; Klok, H.-A. Size-Dependent Lcst Transitions of Polymer-Coated Gold Nanoparticles: Cooperative Aggregation and Surface Assembly. Adv. Mater. 2010, 22 (42), 4721-4725. (53) Xia, Y.; Burke, N. A. D.; Stöver, H. D. H. End Group Effect on the Thermal Response of Narrow-Disperse Poly(N-Isopropylacrylamide) Prepared by Atom Transfer Radical Polymerization. Macromolecules 2006, 39 (6), 2275-2283.

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TOC image

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Microwave Heating of Poly(N-isopropylacrylamide)-Conjugated Gold

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