Presence Of Platinum Nanoparticles Research Articles

Biocompatibility of Platinum Nanoparticles in Brain ex vivo Models in Physiological and Pathological Conditions.

Platinum nanoparticles (PtNPs) have unique physico-chemical properties that led to their use in many branches of medicine. Recently, PtNPs gathered growing interest as delivery vectors for drugs, biosensors and as surface coating on chronically implanted biomedical devices for improving electrochemical properties. However, there are contradictory statements about their biocompatibility and impact on target organs such as the brain tissue, where these NPs are finding many applications. Furthermore, many of the reported studies are conducted in homeostasis conditions and, consequently, neglect the impact of the pathologic conditions on the tissue response. To expand our knowledge on the effects of PtNPs on neuronal and glial cells, we investigated the acute effects of monodisperse sodium citrate-coated PtNPs on rat organotypic hippocampal cultures in physiological or neuronal excitotoxic conditions induced by kainic acid (KA). The cellular responses of the PtNPs were evaluated through cytotoxic assays and confocal microscopy analysis. To mimic a pathologic scenario, 7-day organotypic hippocampal cultures were exposed to KA for 24 h. Subsequently, PtNPs were added to each slice. We show that incubation of the slices with PtNPs for 24 h, does not severely impact cell viability in normal conditions, with no significant differences when comparing the dentate gyrus (DG), as well as CA3 and CA1 pyramidal cell layers. Such effects are not exacerbated in KA-treated slices, where the presence of PtNPs does not cause additional neuronal propidium iodide (PI) uptake in CA3 and CA1 pyramidal cell layers. However, PtNPs cause microglial cell activation and morphological alterations in CA3 and DG regions indicating the establishment of an inflammatory reaction. Morphological analysis revealed that microglia acquire activated ameboid morphology with loss of ramifications, as a result of their response to PtNPs contact. Surprisingly, this effect is not increased in pathological conditions. Taken together, these results show that PtNPs cause microglia alterations in short-term studies. Additionally, there is no worsening of the tissue response in a neuropathological induced scenario. This work highlights the need of further research to allow for the safe use of PtNPs. Also, it supports the demand of the development of novel and more biocompatible NPs to be applied in the brain.

Sonocatalytic recovery of ceria from graphite and inhibition of graphite erosion by ionic liquid based platinum nanocatalyst

Use of ultrasound as an intensified non-destructive decontamination technique for processing graphite limits its reusability beyond a few number of decontamination cycles due to the exfoliation of graphite due to cavitation effects. The current work establishes that the use of platinum nanoparticles in the leachant reduces the erosion of graphite substrate due to cavitation. It presents an improved way of sonochemical recovery of ceria using a mixture of nitric acid, formic acid and hydrazinium nitrate in the presence of platinum nanoparticles and ionic liquid. The platinum nanoparticles catalyst in ionic liquid prevented the generation of the carbon residue due to the combined effect of denitration and reduced sonication. The presence of the catalyst showed a fivefold increase in dissolution kinetics of ceria as well as absence of graphite erosion, facilitating better chances of graphite recycling than the decontamination without the catalyst. The catalytic approach offers a better recycle strategy for graphite with reduced exfoliation and NOx generation due to denitration, making it a more sustainable decontamination process. Since ceria is used as a surrogate for plutonium oxide, the results can be extended to decontaminate such deposits clearly establishing the utility of the presented results in the nuclear industry.

A Donor-Acceptor [2]Catenane for Visible Light Photocatalysis.

Colored charge-transfer complexes can be formed by the association between electron-rich donor and electron-deficient acceptor molecules, bringing about the narrowing of HOMO-LUMO energy gaps so that they become capable of harnessing visible light. In an effort to facilitate the use of these widespread, but nonetheless weak, interactions for visible light photocatalysis, it is important to render the interactions strong and robust. Herein, we employ a well-known donor-acceptor [2]catenane-formed by the mechanical interlocking of cyclobis(paraquat-p-phenylene) and 1,5-dinaphtho[38]crown-10-in which the charge-transfer interactions between two 4,4'-bipyridinium and two 1,5-dioxynaphthalene units are enhanced by mechanical bonding, leading to increased absorption of visible light, even at low concentrations in solution. As a result, since this [2]catenane can generate persistent bipyridinium radical cations under continuous visible-light irradiation without the need for additional photosensitizers, it can display good catalytic activity in both photo-reductions and -oxidations, as demonstrated by hydrogen production-in the presence of platinum nanoparticles-and aerobic oxidation of organic sulfides, such as l-methionine, respectively. This research, which highlights the usefulness of nanoconfinement present in mechanically interlocked molecules for the reinforcement of weak interactions, can not only expand the potential of charge-transfer interactions in solar energy conversion and synthetic photocatalysis but also open up new possibilities for the development of active artificial molecular shuttles, switches, and machines.

Synthesis and Physicochemical Properties of Pt on TiO2 nanotubes as electro catalyst for Methanol Oxidation Reaction

In this paper, TiO2 nanotubes were synthesized electrochemically by anodization of pure Ti sheet in 0.5% HF and annealed in N2 atmosphere to obtain (TONTs-N2) then the platinum was deposited on the support TONTs-N2 by chemical deposition method using NaBH4 as reducing agents to obtain the electrocatalyst Pt-B/TONTs-N2.
 The physicochemical characterizations of Pt-B/TONTs-N2 were performed by scanning electron microscopy (SEM), X-ray diffraction (XRD analysis.
 The catalyst Pt-B/TONTs-N2 was electrochemically characterized in basic solution of methanol by cyclic voltammetry (CV) measurement. XRD characterization indicates the presence of platinum nanoparticles with diameter less than 54.8 nm and regularly combined into TiO2 nanotubes. Pt-B/TONTs-N2 catalyst exhibited a remarkably high electrocatalytic activity and has high electrocatalytic stability for methanol electrocatalytic oxidation reaction.
 In addition, the Pt-B/TONTs-N2 catalyst exhibits better poison tolerance and higher methanol oxidation current density than that reported for Pt/carbon catalyst.
 This suggests that the Pt-B/TONTs-N2 catalyst supported on TONTs-N2 has promising potential applications in electro catalyst reactions.
 Pt supported on the conductive support TONTs-N2 is used as electrocatalyst in alkaline fuel cells. Results showed best improvement in physico-chemical properties of these catalysts in comparison with previous studies.

Mechanistic Studies on TiO2 Photoelectrochemical Radical Cation [2 + 2] Cycloadditions

In addition to electrochemical and photochemical approaches, the photoelectrochemical method using semiconductors as photoelectrodes is a third type of approach in the field of synthetic organic chemistry that enables precise control of single electron transfer (SET) reactions. Herein, we report mechanistic studies on TiO2 photoelectrochemical redox neutral reactions, where both reductive and oxidative SET are involved, using radical cation [2 + 2] cycloadditions as models. In the presence of platinum nanoparticles or molecular oxygen as electron sink or electron acceptor, respectively, the mechanistic details for the photoelectrochemical reactions can be investigated because the excited electron at the conduction band of TiO2 is removed.

Electrodiffusion Characteristics of Halloysite-Modified Bilayer Membranes

Diffusion permeability and electrical conductivity have been studied for bilayer perfluorinated MF-4SC membranes modified with halloysite nanotubes (HNTs) containing noble metal nanoparticles (NPs) deposited onto their surface. It has been found that the diffusion permeability of the bilayer membranes depends on their orientation with respect to an electrolyte flow: the diffusion flux is higher when the modified side of the membrane faces a flow. The study of the electrodiffusion characteristics of HNT-modified bilayer perfluorinated membranes has resulted in the factors being revealed that have the strongest influence on the development of the asymmetry of their current–voltage curves. It has been found that, to obtain a membrane with a fortiori asymmetric properties, it is necessary to synthesize a material the layers of which differ from each other in only one component—either HNTs or metal NPs. The efficiency of the modified membranes as polymer electrolytes for hydrogen-air fuel cells has been determined, and it has been shown that the modification with HNTs reduces the specific power of a fuel cell, while the presence of platinum NPs on a nanotube surface increases this parameter. The reason for the increase in the specific power is the catalytic activity of platinum NPs in the interaction between oxygen and hydrogen in the membrane bulk, which leads to the self-humidifying of the membrane and a decrease in its ohmic resistance.

Optical and Thermal Properties of Laser-Ablated Platinum Nanoparticles Graphene Oxide Composite.

Platinum nanoparticles were synthesized in graphene oxide aqueous solution using a laser ablation technique to investigate the effect of optical linear, nonlinear and thermal properties of platinum-graphene oxide nanocomposite solution. The samples were prepared with different ablation times. The platinum nanoparticles that formed a spherical shape on the surface of graphene oxide solution were authenticated using UV-visible spectrum and transmission electron microscopy patterns. The particle size decreased with increasing ablation time, and the concentration and volume fraction of samples were increased. To obtain the optical linear, nonlinear and thermal properties of platinum-graphene oxide nanocomposite solution, UV-visible spectroscopy, Z-scan, thermal lens and photoacoustic techniques were used. Consequently, the linear and nonlinear refractive indices increased with an increase in the volume fraction of platinum nanoparticles. It was observed from the spatial self-phase modulation patterns that, the optical nonlinear property of the graphene oxide was enhanced in the presence of platinum nanoparticles, and the nonlinearity increased with an increase in the volume fraction of platinum nanoparticles inside the graphene oxide solution. The thermal diffusivity and thermal effusivity of platinum nanoparticles graphene oxide were measured using a thermal lens and photoacoustic methods, respectively. The thermal diffusivity and thermal effusivity of samples were in the range of 0.0341 × 10−5 m2/s to 0.1223 × 10−5 m2/s and 0.163 W s1/2 cm−2 K−1 to 0.3192 W s1/2 cm−2 K−1, respectively. Consequently, the platinum enhanced the optical and thermal properties of graphene oxide.

Visible-light driven hydrogen production using chlorophyll derivatives conjugated with a viologen moiety in the presence of platinum nanoparticles.

The utilization of the light-harvesting and electron-transferring function of chlorophylls (Chls) has received attention for visible-light driven hydrogen production. In this work, a series of Chl derivatives based on pyropheophorbide-a (Pyro-a) conjugated with a viologen moiety, including a Pyro-a methyl ester directly bonded with the viologen at the 3-position 1, its 31-methylene analog 2 and Pyro-a connected with the viologen in the 17-substituent 3, were synthesized from chemical modification of naturally occurring Chl-a and characterized in terms of their photochemical and photophysical properties. As the photoexcited singlet state of the Pyro-a moiety was strongly quenched by the viologen moiety in a molecule, the effective photoinduced intramolecular electron transfer from Pyro-a to the bonded viologen moiety occurred. Moreover, these molecules were applied as a photosensitizer in the system for visible-light driven hydrogen production with platinum nanoparticles via intramolecular reduction of the bonded viologen moiety. Efficient photoreduction of external methyl viologen and successive hydrogen production on platinum nanoparticles were achieved using the synthetic conjugate of Pyro-a with the viologen moiety as a photosensitizer. In particular, effective visible-light driven hydrogen production was accomplished using 3 and platinum nanoparticles via the reduction of external methyl viologen.

Platinum Nanoparticles Decrease Reactive Oxygen Species and Modulate Gene Expression without Alteration of Immune Responses in THP-1 Monocytes.

Platinum nanoparticles (PtNPs) attract great attention due to their efficient catalysis and good degree of cytocompatibility, but information about their effects on the human immune system is still missing. Monocytes are key cells of the innate immune system and the understanding of their reactions to PtNPs is crucial in view of any feasible application to human pathologies. Here, we evaluate the internalization of citrate-coated PtNPs into THP-1 monocytes and its consequences on immune cell responses. We found that the presence of intracellular PtNPs efficiently reduce reactive oxygen species (ROS) without affecting cell viability. The physiological expression of the immune receptors Cluster of Differentiation 14 (CD14), CD11b, CC-Chemokine Receptor 2 (CCR2) and CCR5 and the expression of cytokines and chemokines are not compromised by the presence of PtNPs within THP-1 cells. On the other hand, the treatment with PtNPs modulates the transcription of sixty genes, some of them involved in lipopolysaccharide (LPS) signaling in different cells. However, the treatment with PtNPs of monocytes does not compromise the LPS-induced increase of cytokines in THP-1 monocytes in vitro. Our results demonstrate that citrate-coated PtNPs are non-toxic, perform efficient intracellular reactive oxygen species (ROS) scavenging activity and possess good immune-compatibility, suggesting them as feasible synthetic enzymes for applications in nanomedicine.

Synthesis of Platinum nanoparticles by Gamma Radiolysis

The synthesis of Platinum (Pt) nanoparticles by gamma irradiation is presented. The 0.1 M Pt solution of different concentration was prepared from K2PtCl4. The platinum aqueous solutions were irradiated by gamma radiation at a dose of 70, 90 and 120 kGy. The findings show the effect of irradiation on PtII solutions with different concentrations. The big black particles that are fairly agglomerated when the concentration was above 0.0050 M were observed. The UV-Vis spectrum of Pt of different concentrations shows a strong absorption peak at the wavelength 261 nm after irradiation, which indicates the presence of platinum nanoparticles. Furthermore, FTIR, XRD and HRTEM images also confirmed the presence of the nanoparticles produced by Radiolysis. The size of the Pt nanoparticles was found to be 7.39 nm.

Electrochemically Reduced Water Delays Mammary Tumors Growth in Mice and Inhibits Breast Cancer Cells Survival In Vitro.

Electrochemical reduced water (ERW) has been proposed to have beneficial effects on human health due to its rich content of H2 and the presence of platinum nanoparticles with antioxidant effects. Many studies have demonstrated that ERW scavenging properties are able to reduce the damage caused by oxidative stress in different experimental models. Although few in vivo studies have been reported, it has been demonstrated that ERW may display anticancer effects by induction of tumor cells apoptosis and reduction of both angiogenesis and inflammation. In this study, we show that ERW treatment of MCF-7, MDA-MB-453, and mouse (TUBO) breast cancer cells inhibited cell survival in a time-dependent fashion. ERW decreased ErbB2/neu expression and impaired pERK1/ERK2 and AKT phosphorylation in breast cancer cells. In addition, ERW treatment induced apoptosis of breast cancer cell lines independently of the status of p53 and ER and PR receptors. Our in vivo results showed that ERW treatment of transgenic BALB-neuT mice delayed the development of mammary tumors compared to the control. In addition, ERW induced a significant prolongation of tumor-free survival and a reduction in tumor multiplicity. Overall, these results suggest a potential beneficial role of ERW in inhibiting cancer cells growth.

Nonlinear optical response of platinum nanoparticles and platinum ions embedded in sapphire.

We report on the fabrication of sapphire samples containing platinum nanoparticles (Pt-NPs) and platinum ions (Pt-ions) and the investigation of their third-order nonlinear (NL) optical properties. The presence of Pt-NPs was confirmed by electronic microscopy and by the linear absorption spectrum that shows a localized surface plasmon band centered at 290 nm. A sample without NPs but containing Pt-ions was also studied. The absorptive and refractive contributions to the nonlinearity were studied using the z-scan technique with 100 fs pulses at 800nm. The experiments revealed a NL refractive index, +3.8×10-13 < n2 < +1.3×10-12cm2/W and NL absorption coefficient (β < 9.3 cm/GW). The results show enhancement of about five orders of magnitude with respect to the NL refractive index of sapphire.

Utilising solution dispersed platinum nanoparticles to direct the growth of electrodeposited platinum nanostructures and its influence on the electrocatalytic oxidation of small organic molecules

The electrodeposition of platinum nanostructures on glassy carbon electrodes in the absence and presence of platinum nanoparticles in the electrolyte is reported. It is found that the presence of platinum nanoparticles has a significant influence of the morphology of the platinum electrodeposited onto the electrode surface. Even though the morphology of the materials is affected, the overall surface area is similar. The electrochemical behaviour of the platinum nanostructures is investigated in 1M H2SO4 where distinct differences are observed in the exposed surface sites for platinum electrodeposited in the presence of nanoparticles. The influence of these surface sites is then studied for a variety of electrocatalytic reactions such as methanol and ethylene glycol oxidation and the hydrogen evolution reaction. In the case of organic molecule oxidation reactions, the platinum structures created using platinum nanoparticles in the electrodeposition solution exhibited earlier onset potentials and increased current densities compared to those that were electrodeposited in their absence.

Potentiometric sulfite biosensor based on entrapment of sulfite oxidase in a polypyrrole film on a platinum electrode modified with platinum nanoparticles

The surface of a platinum electrode has been modified with platinum nanoparticles (PtNPs) and the enzyme sulfite oxidase (SOx), was entrapped on its surface in an ultrathin polypyrrole (PPy) film. The PtNPs, with a diameter of 30–40 nm, were deposited on the Pt electrode by cycling the electrode potential 20 times from -200 to 200 mV at a sweep rate of 50 mV.s-1. Morphological evidence of the successful incorporation of SOx and the presence of PtNPs were obtained by scanning electron microscopy. Also, the electrochemical behavior of the PtNPs/PPy-SOx film was examined by cyclic voltammetry, chronopotentiometry, electrochemical impedance spectroscopy and potentiometry. Under optimized conditions, the biosensor achieved a sensitivity of 57.5 mV.decade-1, a linear response that extends from 0.75 to 65 μM of sulfite, a detection limit of 12.4 nM, and a response time of 3–5 s. The biosensor was successfully applied to the determination of sulfite in wine and beer samples.

Polyaniline-Pt and polypyrrole-Pt nanocomposites: Effect of supporting type and morphology on the nanoparticles size and distribution

The size and the distribution of platinum nanoparticles on the polyaniline-Pt (PANI-Pt) and polypyrrole-Pt (PPy-Pt) nanocomposites are extremely sensitive to the polymer matrix morphology. This is observed when the polymer matrix morphology was changed from nanofibers to nanotubes. TEM results showed platinum nanoparticles with size diameter as low as 2nm in the case of polpyrrole nanofiber and polyaniline nanofiber matrices. In addition, FTIR and UV–vis results showed that polyaniline matrix with different morphologies, nanofibers and nanotubes, presented different chemical structures, which resulted in a different size and distribution of the platinum nanoparticles, as it was observed from the SEM, platinum X-ray mapping and TEM results. The DSC thermal analysis results showed that the presence of platinum nanoparticles in the polymer matrix resulted in a greater thermal stability when compared to the polymer matrix. It was the first time that the effect of PANI and PPy morphology on the platinum dispersion and distribution is demonstrated.

Visible-Light-Driven Photoproduction of Hydrogen Using Rhodium Catalysts and Platinum Nanoparticles with Formate

Photochemical hydrogen production is carried out using molecular Rh complexes and sodium formate in the presence of platinum nanoparticles (PtNPs) in aqueous buffer solution. Visible-light-driven photocatalytic reactions for hydrogen production with and without nicotinamide adenine dinucleotide (NAD+) follow two different pathways. Complex [Cp*Rh(bpy)(OH2)]2+ selectively reduces NAD+ to generate NADH using formate as a proton and electron donor and the chemically generated NADH is sequentially used by PtNPs upon photoactivation of eosin Y to produce hydrogen. However, hydrogen is also produced in photoreactions of the Rh catalyst and PtNPs with formate in the absence of NAD+ and eosin Y. The second pathway for hydrogen production was performed under the conditions without NAD+ and eosin Y and derived from a direct electron transfer from in situ generated rhodium(III)-hydride species to photoexcited PtNPs. The direct electron transfer from the rhodium-hydride species to visible-light-driven PtNPs was first...

Chemiluminescence microfluidic system on a chip to determine vitamin B1 using platinum nanoparticles triggered luminol–AgNO3 reaction

A novel and sensitive chemiluminescence (CL) method on a microchip has been presented for the determination of vitamin B1 (VB1). The microchip was fabricated by soft lithographic procedure using polydimethyl siloxane (PDMS) having four inlets and one outlet with a 200μm wide, 250μm height, 6mm diameter and 100mm long microchannel. The method is based on the enhanced CL intensity of luminol by its oxidation with AgNO3 in the presence of platinum nanoparticles (PtNPs). It was found that the oxidation of luminol with AgNO3 by PtNPs produced strong CL signal at about 425nm which meant that the luminophore was still 3-aminopthalate. The CL intensity of the luminol–AgNO3–PtNPs system was further increased with the addition of VB1. Under optimum conditions, the CL intensity was increased by increasing the concentration of VB1 in the range of 1.0×10−7 to 4.0×10−5molL−1 with a correlation coefficient of 0.9992. The limit of detection was found to be 4.8×10−9molL−1 with the relative standard deviation of 1.06%. The method was successfully applied to determine VB1 in vitamin B1 tablets and vitamin B complex tablets. The interaction mechanism of the CL system has been proposed by UV–vis spectra and CL emission spectra.

Ophthalmic Application of Poly(HEMA)s Containing Nanoparticles and Dimethylacrylamide

High functional ophthalmic lens materials, poly(HEMA-co-MMA)s were prepared by the copolymerization of HEMA, MMA, MA, EDGMA, and N,N-dimethylacrylamide in the presence of platinum nanoparticles with antimicrobial properties. The hydrophilic monomer N,N-dimethylacrylamide has excellent biocompatibility and oxygen transmissibility. The combination where platinum nanoparticles were added produced a colorless transparent lens. The water contents were in the range of 36.68-44.08% and the refractive index was measured to be in the range of 1.424-1.436. Meanwhile, the oxygen transmissibility ranged from 11.13 x 10(-11) to 17.63 x 10(-11) (cm2/sec) (mlO2/ml x mm Hg) increased with increasing the addition ratio of N,N-dimethylacrylamide. The physical properties measurements of the produced polymers showed that the nanoparticles did not show significant effect on the water content and refractive index of the hydrogel contact lens, but the materials effected to reduce oxygen permeability to a certain extent. The copolymers have excellent oxygen permeability, indicating that the material can be used to fabricate hydrogel contact lenses with high oxygen transmissibility.

Enhanced activity of chaperonin GroEL in the presence of platinum nanoparticles

The chaperonin protein GroEL was mixed with varying concentrations of K2PtCl4 followed by a 20-fold concentration of sodium borohydride to afford GroEL–platinum nanoparticle complexes in a ratio of between 1:25 and 1:2,000. Typical colour change, from colourless or pale yellow to brown, occurred that was dependent on the amount of platinum present. These complexes were characterised by UV/Vis, inductively coupled plasma optical emission spectroscopy, Fourier transform infra red, transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy. TEM analysis revealed that the size of nanoparticles increased as the molar ratio of platinum to GroEL increased with an average size diameter of 1.72–3.5 nm generated with GroEL–platinum molar ratios of 1:125–1:2,000. Fourier-transform infrared spectroscopy (FTIR) spectra showed no distinct changes in the structure of GroEL but confirmed that the nanoparticles were attached to the protein. The effect of platinum nanoparticles on the ATPase activity of GroEL showed an activity of 5.60 μmol min−1 ml−1 (87 % increase over a control) at the molar ratio of GroEL–platinum nanoparticles of 1:25.

Catalytic dissolution of ceria under mild conditions

The dissolution of ceria is studied through a catalytic reduction process involving platinum nanoparticles in mild conditions at near ambient temperature. The deposition of platinum nanoparticles is made by sonication (Ar, 18 W cm−2, 20 kHz), and further dissolution is studied as a function of different parameters such as stirring, sonication, dissolution media and temperature. The dissolution is evaluated using UV-vis spectrophotometry, ICP-AES, and SEM. The quantitative dissolution of ceria can be performed in HNO3–HCOOH–[N2H5][NO3], HNO3–[N2H5][NO3] or H2SO4–HCOOH mixtures at 40 °C. Nevertheless, it is shown that the combined use of ultrasound with nitric media in the presence of platinum nanoparticles can lead to passivating phenomena resulting in a decrease of the dissolution rate.