Capped Platinum Nanoparticles Research Articles

Assessing anticancer properties of PEGylated platinum nanoparticles on human breast cancer cell lines using in-vitro assays

This study describes the in-vitro cytotoxic effects of PEG-400 (Polyethylene glycol-400)-capped platinum nanoparticles (PEGylated Pt NPs) on both normal and cancer cell lines. Structural characterization was carried out using x-ray diffraction and Raman spectroscopy with an average crystallite size 5.7 nm, and morphological assessment using Scanning electron microscopy (SEM) revealed the presence of spherical platinum nanoparticles. The results of energy-dispersive x-ray spectroscopy (EDX) showed a higher percentage fraction of platinum content by weight, along with carbon and oxygen, which are expected from the capping agent, confirming the purity of the platinum sample. The dynamic light scattering experiment revealed an average hydrodynamic diameter of 353.6 nm for the PEGylated Pt NPs. The cytotoxicity profile of PEGylated Pt NPs was assessed on a normal cell line (L929) and a breast cancer cell line (MCF-7) using the 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay. The results revealed an IC50 of 79.18 μg ml−1 on the cancer cell line and non-toxic behaviour on the normal cell line. In the dual staining apoptosis assay, it was observed that the mortality of cells cultured in conjunction with platinum nanoparticles intensified and the proliferative activity of MCF-7 cells gradually diminished over time in correlation with the increasing concentration of the PEGylated Pt NPs sample. The in vitro DCFH-DA assay for oxidative stress assessment in nanoparticle-treated cells unveiled the mechanistic background of the anticancer activity of PEGylated platinum nanoparticles as ROS-assisted mitochondrial dysfunction.

Sub lethal levels of platinum nanoparticle cures plasmid and in combination with carbapenem, curtails carbapenem resistant Escherichia coli

Drug resistance traits are rapidly disseminated across bacteria by horizontal gene transfer, especially through plasmids. Plasmid curing agents that are active both in vitro and in vivo will resensitize Multi Drug Resistant (MDR) bacteria to antimicrobial agents. Pectin capped platinum nanoparticles (PtNPs) at sub MIC (20 µM) concentration was effective, in causing loss of Extended Spectrum Beta Lactamase (ESBL) harboring plasmid as evidenced by, absence of plasmid in agarose gel and by a concomitant (16–64 fold) drop in MIC for cell wall inhibitors ceftriaxone and meropenem, in carbapenem resistant Escherichia coli (CREC). Interestingly, the plasmid cured strain exhibited small colony morphology and displayed slower growth both in vitro and in vivo. Complementation of cured strain with plasmid from the wild type strain restored resistance towards meropenem and ceftriaxone. Relative to wild type, plasmid cured strain displayed 50% reduction in biofilm formation. Plasmid curing also occurred in vivo in infected zebrafish with curing efficiency of 17% for nanoparticle + meropenem treatment. PtNPs + meropenem reduced bioburden of CREC in infected zebrafish by 2.4 log CFU. Mechanistic studies revealed that nanoparticle interacted with cell surface and perturbed inner membrane integrity. PtNPs did not induce ROS, yet it caused plasmid DNA cleavage, as evidenced by gyrase inhibition assay. Our study for the first time reveals that PtNPs as plasmid curing agent can resensitize MDR bacteria to selective antimicrobial agents in vivo.

Jacalin capped platinum nanoparticles confer persistent immunity against multiple Aeromonas infection in zebrafish

Bacterial resistance is a major clinical problem, which is compounded by both a lack of new antibiotics and emergence of multi- and extremely-drug resistant microbes. In this context, non-toxic nanoparticles could play an important role in conferring protection against bacterial infections and in this study we have made an attempt to show the usefulness of jacalin capped platinum nanoparticles in protecting zebrafish against multiple infections with Aeromonas hydrophila. Our results also indicate that use of nanoparticles promotes adaptive immune response against the pathogen, so much so that zebrafish is able to survive repetitive infection even after twenty one days of being treated with jacalin-capped platinum nanoparticles. This is significant given that platinum salt is not antibacterial and jacalin is non-immunogenic. Our study for the first time reveals a novel mechanism of action of nanoparticles, which could form an alternate antibacterial strategy with minimal bacterial resistance.

Highly Sensitive Glucose Sensor Based on Organic Electrochemical Transistor with Modified Gate Electrode.

An organic electrochemical transistor (OECT) with a glucose oxidase (GOx) and poly(n-vinyl-2-pyrrolidone)-capped platinum nanoparticles (Pt NPs) gate electrode was successfully integrated with a microfluidic channel to act as a highly sensitive chip-based glucose sensor. The sensing mechanism relies on the enzymatic reaction between glucose and GOx followed by electrochemical oxidation of hydrogen peroxide (H2O2) produced in the enzymatic reaction. This process largely increases the electrolyte potential that applies on PEDOT:PSS channel and causes more cations penetrate into PEDOT:PSS film to reduce it to semi-conducting state resulting in lower electric current between the source and the drain. The extremely high sensitivity and low detection limit (0.1μM) of the sensor was achievable due to highly efficient Pt NPs catalysis in oxidation of H2O2. Pt NPs were deposited by a bias-free two-step dip coating method followed by a UV-Ozone post-treatment to enhance catalytic ability. A polydimethylsiloxane (PDMS) microfluidic channel was directly attached to the OECT active layer, providing a short detection time (~1min) and extremely low analyte consumption (30μL). Our sensor has great potential for real-time, noninvasive, and portable glucose sensing applications due to its compact size and high sensitivity.

Facile and green synthesis of phytochemicals capped platinum nanoparticles and in vitro their superior antibacterial activity

The increase in the severe infectious diseases and resistance of the majority of the bacterial pathogens to the available drug is a serious problem now a day. In order to overcome this problem it is necessary to develop new therapeutic agents which are non-toxic and more effective to inhibit these microbial pathogens. For this purpose the plant extract of highly active medicinal plant, Taraxacum laevigatum was used for the synthesis of platinum nanoparticles (PtNPs) to enhance its bio-activities. The surface plasmon resonance peak appeared at 283nm clearly represent the formation of PtNPs. The results illustrate that the bio-synthesized PtNPs were uniformly dispersed, small sized (2–7nm) and spherical in shape. The green synthesized PtNPs were characterized by UV–vis spectroscopy, XRD, TEM, SEM, EDX, DLS and FTIR. These nanoparticles were tested against gram positive bacteria (Bacillus subtilis) and gram negative bacteria (Pseudomonas aeruginosa). The bio-synthesized PtNPs were examined to be more effective against both of the bacteria. The results showed, that the zone of inhibition of PtNPs against P. aeruginosa was 15 (±0.5) mm and B. subtilis was 18 (±0.8) mm. The most significant outcome of this examination is that PtNPs exhibited strong antibacterial activity against P. aeruginosa and B. subtilis which have strong defensive system against several antibiotics.

Bioelectronics: Highly Sensitive Metabolite Biosensor Based on Organic Electrochemical Transistor Integrated with Microfluidic Channel and Poly(N‐vinyl‐2‐pyrrolidone)‐Capped Platinum Nanoparticles (Adv. Mater. Technol. 5/2016)

Bioelectronics: Highly Sensitive Metabolite Biosensor Based on Organic Electrochemical Transistor Integrated with Microfluidic Channel and Poly(N‐vinyl‐2‐pyrrolidone)‐Capped Platinum Nanoparticles (Adv. Mater. Technol. 5/2016)

Highly Sensitive Metabolite Biosensor Based on Organic Electrochemical Transistor Integrated with Microfluidic Channel and Poly(N‐vinyl‐2‐pyrrolidone)‐Capped Platinum Nanoparticles

Organic electrochemical transistors (OECTs) are used as highly sensitive glucose and lactate sensors by modifying the gate electrode with glucose oxidase/lactate oxidase and poly(n‐vinyl‐2‐pyrrolidone)‐capped platinum nanoparticles (Pt NPs). The Pt NPs are deposited by using a two‐step dip coating method without bias instead of the conventional electrodeposition method and followed by an UV‐Ozone post treatment to enhance the catalytic ability of the Pt NPs. The modified OECT sensors have extremely high sensitivity, and can achieve a detection limit of glucose and lactate down to 10−7 and 10−6m, respectively. A polydimethylsiloxane microfluidic channel is successfully integrated with the OECT sensors, which provides a compact chip size of the sensors, a short detection time of around 1 min and extremely low consumption of analyte (30 L). The cross talk between individual sensors in multianalyte sensing devices is also reduced by the dual microfluidic channel structure. Practical applications, such as for detecting glucose in saliva, can therefore be realized, and a prototype of a portable glucose sensor has been successfully created in this study. This portable glucose sensor has excellent potential for real‐time and noninvasive glucose sensing applications.

Effects of SOD/catalase mimetic platinum nanoparticles on radiation-induced apoptosis in human lymphoma U937 cells

Since polyacrylic acid capped platinum nano-particles (nano-Pts) are known to have a unique ability to quench superoxide (O2(-)) and hydrogen peroxide (H2O2), the anti-oxidant activity of nano-Pts against apoptosis induced by x-irradiation in human lymphoma U937 cells was investigated. DNA fragmentation assay, Annexin V-FITC/PI by flow cytometry and Giemsa staining revealed a significant decrease in apoptosis induced by 10 Gy, when cells were pre-treated with nano-Pts in a dose-dependent manner. Pre-treatment with nano-Pts significantly decreased radiation-induced reactive oxygen species (ROS) production, Fas expression and loss of mitochondrial membrane potential as determined by flow-cytometry. Furthermore, western blot analysis also showed that the expression of cleaved caspase-3, Bid and cytosolic cytochrome-c were significantly reduced in nano-Pts pretreated cells. Due to the catalase mimetic activity of nano-Pts, these results indicate that pre-treatment of U937 cells with nano-Pts significantly protect radiation-induced apoptosis by inhibiting intracellular ROS (mainly H2O2), which plays a key role in the induction of apoptosis, because of no practical observation of intracellular O2(-) formation.

PVP stabilized Pt nano particles catalyzed de-oxygenation of phenoxazine group by hydrazine in physiological buffer media: surfactant competes with reactants for the same surface sites

PVP capped platinum nano particles (PNP) of 5 nm diameter were prepared and characterized as homogeneous and of spherical nature. At physiological pH range (6.0-8.0), these PNP catalyze the deoxygenation of phenoxazine group containing resazurin (1) by hydrazine. The observed rate constants (k(o)), increase linearly with [PNP] at constant [1] and [Hydrazine]; but first increase and then after reaching a maximum it decrease with increase in [1] as well as in [Hydrazine]. The k(o) values increase linearly with 1/[H(+)] indicating N(2)H(4) as the reducing species that generates from the PNP assisted deprotonation of N(2)H(5)(+). The kinetic observations suggest Langmuir-Hinshelwood type surface reaction mechanism where both 1 and hydrazine are adsorbed on nano particles surface and compete for the same sites. Interestingly, the surfactant molecules, polyvinylpyrrolidone (PVP), though do not take part into reduction reaction but having same type of functional groups as reactants, competes with them for the same surface sites. Adsorption on PNP with same type of functional group is further supported by the FTIR spectra of Pt-PVP and Pt-1. Thus on increasing [PVP], k(o) decreases linearly and only when [PVP] is held constant, the plot of k(o) vs. [PNP] passes through the origin indicating the insignificance of uncatalyzed reaction. The plot of ln k(o) vs. [1] or [Hydrazine] shows two different linear zones with different exponent values with respect to [1] and [Hydrazine]. This indicates that along with the complex heterogeneous surface adsorption processes, the mutual interactions between the reactants are also changing with the relative concentrations of reactants or, in general, with the molar ratio ([Hydrazine]/[1]).

Novel catalytic gas sensors based on functionalized nanoparticle layers

Abstract A thermal hydrogen gas sensor with a new type of catalytic layer based on films made of dodecylamine (DDA) capped platinum nanoparticles (DDA capped PtNPs) is presented here. These nanoparticles – prepared by a colloidal synthetic approach – offer, due to their ligand shell, a higher stability and a better adhesion to substrates and show lower agglomeration. Working principle of the sensing elements, consisting of two thermopiles and a central heater placed on a silicon nitride membrane, is the thermoelectric effect. By deposition of the ligand capped nanoparticles on the heated junction of one thermopile, hydrogen can be detected due to a change of the thermopile thermovoltage resulting from the reaction heat released during catalytic H 2 oxidation. A second thermopile was used as a reference element. In order to determine the influence of the organic ligands on the sensor activity, unprotected platinum nanoparticles (unprotected PtNPs) were also used as catalyst. Both approaches, the uncovered and functionalized platinum nanoparticles, have been characterized and exposed to different hydrogen concentrations. Results point towards a strong agglomeration of unprotected nanoparticles resulting in low output signals, whereas for the ligand capped nanoparticles a linear and reproducible output signal with a sensitivity up to 6.4 mV/1000 ppm hydrogen was observed.

Mg/Al layered double hydroxide-Pt nanoparticle composite by delamination-restacking route

Platinum nanoparticle intercalated magnesium–aluminum layered double hydroxide (LDH) composite was prepared by restacking the colloidal dispersion of organically modified LDH in the presence of preformed oleylamine capped platinum nanoparticles in n-butanol. The resultant nanocomposite was characterized using powder X-ray diffraction (PXRD), infrared (IR) spectroscopy, transmission electron microscopy (TEM), selected area electron diffraction and energy dispersive X-ray spectroscopy (EDX). The PXRD pattern of the composite indicates an expanded interlayer due to the intercalation of the Pt-nanoparticles into the LDH interlayer region. PXRD patterns along with the IR spectra confirm the formation of the precursors and the composite. TEM image of Pt-nanoparticles shows spherical particles with an average particle size of ~3 nm and that of the composite shows dispersed Pt-nanoparticles on the LDH matrix. The presence of Pt, Mg and Al in the composite is indicated in the EDX data.

Polymerase chain reaction efficiency improved by water soluble β-cyclodextrins capped platinum nanoparticles

Metal nanoparticles can be used in polymerase chain reaction methodology to optimize DNA amplification. In this paper, the effect of water soluble β-cyclodextrins capped platinum nanoparticles on polymerase chain reaction efficiency was reported for the first time. The capped nanoparticles were prepared by photochemical reduction of Platinum-acetylacetonate in presence of β-cyclodextrins. The PCR efficiency was evaluated in presence of different amounts of both capped nanoparticles and capping agent (β-cyclodextrins) as reference.The results demonstrated that the capped nanoparticles were able to increase the polymerase chain reaction efficiency mainly by metal thermal efficiency mechanism, whereas the capping agents themselves do not influence the DNA amplification. Capped nanoparticles are very promising for the efficiency improvement of Polymerase Chain Reaction, determining sensitivity improvement and allowing the reduction of the reagent's sample concentration.

Electrophoretic Deposition of Poly(N-Vinyl-2-Pyrrolidone)-Capped Platinum Nanoparticles on Fluorine-Doped Tin Oxide Glass as a Counter Electrode for Dye-Sensitized Solar Cells

Electrophoretic Deposition of Poly(N-Vinyl-2-Pyrrolidone)-Capped Platinum Nanoparticles on Fluorine-Doped Tin Oxide Glass as a Counter Electrode for Dye-Sensitized Solar Cells

Shape Changes of Pt Nanoparticles Induced by Deposition on Mesoporous Silica

Polyvinylpyrollidone (PVP)-capped platinum nanoparticles (NPs) are found to change shape from spherical to flat when deposited on mesoporous silica substrates (SBA-15). Transmission electron microscopy (TEM), small-angle X-ray scattering (SAXS), and extended X-ray absorption fine structure (EXAFS) analyses are used in these studies. The SAXS results indicate that, after deposition, the 2 nm NPs have an average gyration radius 22% larger than in solution, while the EXAFS measurements indicate a decrease in first neighbor co-ordination number from 9.3 to 7.4. The deformation of these small capped NPs is attributed to interactions with the surface of the SBA-15 support, as evidenced by X-ray absorption near-edge structure (XANES).

Nanocomposite electrodes based on pre-synthesized organically capped platinum nanoparticles and carbon nanotubes. Part II: Determination of diffusion area for oxygen reduction reflects platinum accessibility

In this paper we report the determination of the diffusion area for oxygen reduction in porous electrode structure having a controlled platinum loading and based on capped platinum electrocatalysts and carbon nanotubes. Such a parameter is expected to be higher than the macroscopic geometrical area of the active porous layer. The oxygen diffusion area is determined by cyclic voltammetry after impregnation of the electrode structure by the electrolyte, and using the equations available for peak potential and peak current as a function of scan speed for irreversible redox couple. First it is found first that the oxygen diffusion area is dependent on the total amount of platinum in the electrode. Second, for a given platinum loading, the diffusion area is higher when the mass ratio of platinum to carbon nanotube decreases. This point indicates that the accessibility of platinum capped electrocatalyst is better in such cases. It is thus concluded that the oxygen diffusion area determination in porous electrode structures may be used to characterize the accessibility of the capped electrocatalysts for oxygen reduction. Even if this area is different in nature from the one calculated by Hydrogen Underpotential Deposition, we believe that its determination might be of interest for the characterization of porous electrodes structures in which the electrocatalyst is combined with a finely divided carbon support.

Active targeting of cancer cells using folic acid-conjugated platinum nanoparticles

Interaction of nanoparticles with human cells is an interesting topic for understanding toxicity and developing potential drug candidates. Water soluble platinum nanoparticles were synthesized via reduction of hexachloroplatinic acid using sodium borohydride in the presence of capping agents. The bioactivity of folic acid and poly(vinyl pyrrolidone) capped platinum nanoparticles (Pt-nps) has been investigated using commercially available cell lines. In the cell viability experiments, PVP-capped nanoparticles were found to be less toxic (>80% viability), whereas, folic acid-capped platinum nanoparticles showed a reduced viability down to 24% after 72 h of exposure at a concentration of 100 μg ml(-1) for MCF7 breast cancer cells. Such toxicity, combined with the possibility to incorporate functional organic molecules as capping agents, can be used for developing new drug candidates.

Evidence for high performances of low Pt loading electrodes based on capped platinum electrocatalyst and carbon nanotubes in fuel cell devices

Recently we reported the preparation and electrochemical behaviour of porous electrodes based on the controlled combination of carbon nanotubes and capped platinum nanoparticles towards oxygen reduction. Due to the organic crown of the nanoparticles, the electrodes exhibited low hydrogen underpotential deposition (H upd) electroactive surface areas but significant activity towards oxygen reduction was recorded down to very low platinum loadings of few μg/cm 2. While the presence of organic stabilizing material, at the surface of the electrocatalyst synthesized by wet chemistry, may be considered as a potential drawback in fuel cell community, we present in this paper results showing that our capped electrocatalyst associated with carbon nanotubes can be used without any pre-treatment and exhibit high performances in fuel cell devices, in spite of low platinum loadings. Beyond the practical interest of such capped nanoparticles in fuel cell technology demonstrated here, fundamental question related to the high performances of the capped electrocatalyst are still opened and are currently under investigation.

Nanocomposite electrodes based on pre-synthesized organically capped platinum nanoparticles and carbon nanotubes. Part I: Tuneable low platinum loadings, specific H upd feature and evidence for oxygen reduction

A bottom-up approach is used here to combine carbon nanotubes synthesized by CVD and organically capped platinum nanoparticles electrocatalyst exhibiting a direct electrochemical activity towards oxygen reduction. Both nano-objects are handled in liquid suspension and are associated together in a controlled way. The nanocomposite liquid dispersions can be precisely controlled in terms of platinum nanoparticles to carbon nanotubes weight ratios (NP/NT) which correspond to different coverages of nanotubes by nanoparticles. Electrodes with low to ultra-low platinum loadings can then be prepared on porous fuel cell carbon supports by filtration. The direct electrochemical activity towards aqueous oxygen reduction reaction (ORR) of electrodes with platinum loadings ranging from about 1 to 60 μg/cm 2 is reported without any activation step in order to keep the features of the nanoparticles intact. Before that, we studied the responses obtained when impregnating our hydrophobic electrodes by a voltamperometric gas consumption procedure. These responses are also dependent of the composition of our electrodes. Whereas our results are of particular interest with respect to the optimization of platinum loading in fuel cell electrodes, the specific behaviour of these capped platinum nanoparticles towards proton adsorption–desorption reveals the difficulty to determine reliable active surface area with related regard to the platinum loading and point to the necessity to determine other characteristic parameters for the electrodes.

Sum Frequency Generation and Catalytic Reaction Studies of the Removal of Organic Capping Agents from Pt Nanoparticles by UV−Ozone Treatment

We report the structure of the organic capping layers of platinum colloid nanoparticles and their removal by UV-ozone exposure. Sum frequency generation vibrational spectroscopy (SFGVS) studies identify the carbon-hydrogen stretching modes on poly(vinylpyrrolidone) (PVP) and tetradecyl tributylammonium bromide (TTAB)-capped platinum nanoparticles. We found that the UV-ozone treatment technique effectively removes the capping layer on the basis of several analytical measurements including SFGVS, X-ray photoelectron spectroscopy, and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The overall shape of the nanoparticles was preserved after the removal of capping layers, as confirmed by transmission electron microscopy (TEM). SFGVS of ethylene hydrogenation on the clean platinum nanoparticles demonstrates the existence of ethylidyne and di-σ-bonded species, indicating the similarity between single-crystal and nanoparticle systems.

Oxygen reduction of pre-synthesized organically capped platinum nanoparticles assembled in mixed Langmuir–Blodgett films: Evolutions with the platinum amount and leveling after fatty acid removal

Mixed Langmuir–Blodgett (LB) films based on crown derivatized platinum nanoparticles (NPs) and fatty acid showed a direct electrochemical activity toward oxygen reduction reaction (ORR) in acidic medium. This paper reports on the original and strong effects observed in the electrochemical response of these two-phase systems towards oxygen reduction by varying the Pt amount in the mixed LB films. The easy manipulation of pre-synthesized organically capped nanoparticles, combined with the features of the Langmuir–Blodgett technique allows good control of the platinum loading in the films. Pt loadings are set by changing the number of deposited monolayers and/or their nanoparticle density. Loading variations induce strong modifications in the voltammograms and are considered in terms of the relative weight of the two phases: platinum nanoparticles and fatty acids. We point out the strong influence of the environment of platinum nanoparticles towards their electrocatalytical behaviour. Various effects, such as electrical resistance of the nanostructures are considered. Evolution of the peak current density ratios from O 2 and [Fe(CN) 6] 3−/4− probes as a function of platinum loading in mixed films could suggest a possible change in the dominating number of electrons exchanged in the ORR. The effect of the fatty acid phase is definitely demonstrated by the leveling of the electrochemical responses after its elimination from the thin film structures. The electrochemical response is then likely governed by only the organic crown of the particles, which controls the ultimate local environment of the platinum particles. In such a situation, the optimized platinum loading is found to be 2.4 μg cm −2.