Role Of AuNPs Research Articles

Role of AuNPs in Active Food Packaging Improvement: A Review.

There is a worldwide concern about food loss due to reduced shelf life among food science researchers. Hence, it seems that any techniques contributing to improved food packaging are most welcome in the food sector. It has been demonstrated that the administration of nanotechnology-based techniques such as metal-based nanoparticles can fade away the unresolved obstacles in shortened shelf life and environmental concerns. Along with substantial signs of progress in nanoscience, there is a great interest in the usage of green synthesis-based methods for gold nanoparticles as the most advantageous metals, when compared to conventional chemistry-based methods. Interestingly, those aforementioned methods have significant potential to simplify targeted administration of gold nanoparticles due to a large surface-volume ratio, and diminished biohazards, aimed at increasing stability, and induction of anti-microbial or antioxidant properties. However, it is necessary to consider the hazards of gold nanoparticles including migration for food packaging purposes.

The dual role of Au nanoparticles in the surface plasmon resonance enhanced photocatalyst Au/g-C3N4

Gold nanoparticles (Au NPs) are widely utilized to broaden the light absorption of the photocatalysts due to their localized surface plasmon resonance (LSPR). However, the photocatalytic mechanism of Au/photocatalyst heterostructure involving charges transfer and reactive sites is still in dispute. Here, we synthesized a typical system Au/graphite carbon nitride (g-C3N4) and demonstrate that the role of Au NPs in the LSPR enhanced photocatalysis. Under visible light, the photoexcited electrons of g-C3N4 would transfer to Au NPs and reduce protons into hydrogen together with hot electrons of Au NPs. The hot holes of Au NPs would flow to g-C3N4 and oxidize triethanolamine. Therefore, the Au NPs play a dual role, plasma, and cocatalyst, in the LSPR enhanced photocatalyst. When λ > 420 nm, Au /g-C3N4 has hydrogen production of 159.9 μmol g−1 h−1. Our findings confirm the significance of metal plasma in photocatalytic reaction and benefit designing photocatalysts with boosting performance.

Gold nanoparticles improve the embryonic developmental competency of artificially activated mouse oocytes.

Currently, artificial oocyte activation has attracted wide attention in assisted reproduction due to extensive range of applications, particularly in somatic cell nuclear transfer and deriving pluripotent stem cell lines and it is the unique model to determine the role of paternal genome. Numbers of artificial activating agents have been used extensively to induce the oocytes activation; however, embryos developmental competency of artificially activated oocytes is still very low. In the present study, we determined the functional impact of strontium chloride supplementation with gold nanoparticles (AuNPs) in artificial oocytes activation and subsequent embryonic development. Oocytes were activated artificially in the culture medium containing 250 nM AuNPs with constant concentration of strontium chloride 10.00 mM. We found that adding 250 nM AuNPs with constant concentration of strontium chloride (10.00 mM for 3 hr) in culture medium improves the proportion of embryos reaching to the morula and blastocyst stages from 61.00% and 42.00% (controls) to 75.00% and 58.00% (250 nM AuNPs), respectively. In addition, foster mothers receiving AuNPs-treated embryos showed more implantation percentage and pregnancy rate relative to females received control embryos. Finally, embryos treated with 250 nM AuNPs concentration showed no toxic effect in term of blastocyst development. Collectively, our findings suggest the potential role of AuNPs in early embryonic development for mouse oocytes activated artificially and provide new insights in the field of animal biotechnology and assisted reproduction in humans.

A detailed EIS study of boron doped diamond electrodes decorated with gold nanoparticles for high sensitivity mercury detection

This work compares the electrochemical impedance response of polished and unpolished boron doped diamond (BDD) electrodes, during mercury detection measurements. For each substrate type both bare electrodes and electrodes decorated with average diameter 30 nm AuNPs were used, to investigate the role of AuNPs during mercury sensing with diamond electrodes. In square wave anodic stripping voltammetry (SWASV) measurements for mercury detection, the mercury ions in the electrolyte are deposited onto, then stripped from the diamond electrode surface. To investigate the different electrode performances during these steps, the EIS measurements were made at the deposition and stripping potentials, alongside scans at open circuit potential for comparison. The performance of the electrodes is assessed in terms of their electron transfer rate (k0). The electrodes decorated with AuNPs are shown to have lower capacitance and higher reactivity than the bare pBDD and BDD electrodes, until the mercury concentration in the electrolyte is < 500 µM, when the sp2/sp3 carbon ratio at the surface of the electrodes has a greater influence on the sensitivity for mercury detection than the presence of AuNPs.

Selective Oxidation of Transient Organic Radicals in the Presence of Gold Nanoparticles.

The ability of gold nanoparticles (AuNPs) to catalyze reactions involving radicals is poorly studied. However, AuNPs are used in applications where chemical reactions involving transient radicals occur. Herein, we investigate AuNPs’ catalytic effect on 2-propanol oxidation and acetanilide hydroxylation in aqueous solutions under ionizing radiation at room temperature. In both cases, the presence of AuNPs led to selective oxidation of organic radicals, significantly changing the products’ composition and ratio. Based on these observations, we stress how AuNPs’ catalytic activity can affect the correctness of reactive oxygen species concentration determination utilizing organic dyes. We also provide a discussion on the role of AuNPs’ catalytic activity in the radiosensitization effect actively studied for radiotherapy.

The role of AuNPs on the photocatalytic degradation enhancement in MoO3-based heterostructures

In this work, gold nanoparticles (AuNPs) on MoO3-nanorods (MoO3-Nr) and MoO3-micro-rods (MoO3-Mr) array were directly obtained by thermal oxidation on a Mo foil coated with Au. A highly reproducible heterostructure (MoO3/AuNPs) array was achieved and the physical properties were studied by X-ray diffraction, electron microscopy, electron diffraction, and Raman spectroscopy. The MoO3-Nr were obtained with an average diameter of 60.1 nm, while two size distribution of AuNPs were identified: 9.4 nm and 80.1 nm. The MoO3-Nr/AuNPs arrays were achieved when a temperature ≥700 °C was used. By analyzing methylene blue (MB) degradation, we determined that the photodegradation of MB by MoO3-Nr/AuNPs follows the step-by-step N-dealkylation path. We observed that AuNPs increase dramatically the degradation efficiency and the photocatalytic reproducibility across MB degradation cycles.

Gold Nanoparticles Inhibit Colorectal Cancer Liver Metastasis through Inhibiting the TGF-β Pathway

Introduction: The application of gold nanoparticles (AuNPs) to the management of cancer is currently the new breakthrough in cancer research. However, the role of AuNPs on tumor growth and metastasis in colon cancer and the mechanism by which AuNPs regulate tumor growth and liver metastasis in colorectal cancer (CRCLM) are unclear. Method: We established two TGF-β inducible luciferase colon cancer cell line and orthotopic colon cancer and liver metastasis animal models. We also overexpressed or knockdown Smad4, an important transduction factor of the TGF-β signaling pathway, to explore the molecular mechanism by which AuNPs regulate CRCLM. Results: AuNPs inhibited TGF-β secretion of colon cancer, and downregulated the downstream reporter genes of TGF-β signaling pathway. AuNPs inhibited cell proliferation, migration and invasion in vitro, and reduced tumor growth and liver metastasis in vivo. ERK, P38 MAPK and AKT was inactivated by AuNPS, leading to down-regulation of VEGF secretion and Vimentin while up-regulation of E-Cadherin. When Smad4 was knockdown, cells were significantly more sensitive to AuNPs treatment. The TGF-β inducible luciferase cell line were established, and used for liver metastasis animal models. Mice were treated with the TGF-β receptor inhibitors, and the results showed that this model could observe the activation of TGF-β signaling pathway as well as tumor progression in vivo. Conclusions: These results provided evidences that AuNPs inhibit CRCLM through inhibiting the TGF-β pathway. This research provided theoretical evidences for the clinical use of AuNPs for the treatment of colon cancer or CRCLM.

Facile Synthesis of a Tailored-Designed Au/Pt Nanoanode for Enhanced Formic Acid, Methanol, and Ethylene Glycol Electrooxidation

The recent revolution in nanoscience and global energy demand have motivated research in liquid fuel cells (LFCs) due to their enhanced efficiency, moving flexibility, and reduced contamination. In line with this advancement, a glassy carbon (GC) electrode was modified with platinum (PtNPs) and gold (AuNPs) nanoparticles to fabricate a nanosized anode for formic acid, methanol, and ethylene glycol electrooxidation (abbreviated, respectively, to FAO, MO, and EGO), of the key anodic reactions of LFCs. The deposition sequence of the catalyst’s layers was important where the Au/Pt/GC electrode (in which PtNPs were directly deposited onto the GC surface followed by AuNPs—surface coverage ≈ 32%) exhibited the best catalytic performance. The catalytic performance of the Au/Pt/GC anode excelled (at least threefold) its value obtained at the Pt/GC anode with regard to FAO and EGO, if the oxidation peak currents were compared. This enhancement got reduced to 1.4 times in the case of MO, but the large decrease (− 220 mV) in the onset potential of MO provided compensation. The role of AuNPs in the Au/Pt/GC catalyst was principal in boosting its catalytic performance as it immunized the underlying PtNPs against CO poisoning which is associated with the release of CO as an intermediate during the oxidation. Interestingly, AuNPs succeeded in interrupting the contiguity of the Pt surface sites required for CO adsorption during FAO, MO, and EGO and, thus, presage preventing the deterioration of the catalytic performance of their corresponding LFCs.

AuNPs-PCL nanocomposite accelerated abdominal wound healing through photothermal effect and improving cell adhesion

Accelerating wound healing with modified biomaterial has been an attracting field in both material science and medicine. Enhanced cell adhesion could be acquired by improving surface hydrophilicity, which contributes to accelerating wound healing. Chemical reaction has been used for surface modification, but this study used a simple and nontoxic method to improve the hydrophilicity. Polycaprolactone (PCL) scaffold has been regarded as promising material for wound healing while its surface is hydrophobic. Our study demonstrated enhanced hydrophilicity of PCL with AuNPs coating. AuNPs has good biocompatibility and excellent photothermal effect. The coating of AuNPs not only improved the cell adhesion, but also gave PCL the ability to inhibit the growth of bacteria. Animal study showed that the nanocomposites decreased lymphocytes and neutrophils, increased neovascularization and accelerated the abdominal wound healing, which was attributed to improved hydrophilicity and the antibacterial ability. In conclusion, we demonstrated that the nanocomposite could be used as a potential scaffold for cell adhesion and wound healing, and the role of AuNPs was highlighted as a kind of outstanding supplement.

Microkinetic Modeling of Homogeneous and Gold Nanoparticle-Catalyzed Oxidation of Cyclooctene

Small gold nanoparticles (AuNPs) have recently shown potential to act as a catalyst for oxidation reactions mediated by free radicals, with their role postulated to be facilitating hydrogen abstraction by gold superoxo species and/or activation of hydroperoxides. Cyclooctene oxidation using molecular oxygen as the oxidant at 373 K showed high selectivity to the epoxide product, cyclooctene oxide, with either tert-butyl hydroperoxide as an initiator or in the presence of small AuNPs (5–8 atoms). While previous studies have investigated the mechanism leading to high epoxide selectivity using density functional theory, a full microkinetic model was developed in this work using automated network generation to determine the relative contributions of elementary reactions and the role of AuNPs. A cycle of radical addition of peroxy and alkoxy radicals with subsequent epoxidation reactions can justify the observed activity and selectivity to epoxide at multiple temperatures and initiator concentrations. The alcoh...

PH sensitive release of doxorubicin anticancer drug from gold nanocomposite hydrogel based on poly(acrylic acid) grafted onto salep biopolymer

In this manuscript, synthesis, characterization, swelling behavior, and drug delivery performance of a gold nanocomposite hydrogel (GNH) based on poly(acrylic acid) grafted onto salep, as a biocompatible polymer, are described. Gold nanoparticles (AuNPs) as nanometer base, ammonium persulfate as an initiator, N,N-methylenebisacrylamide as a crosslinker, and acrylic acid as pH sensitive monomer were employed for the preparation of entitled GNH in aqueous solution and their amounts were optimized to reach the highest water absorbance. The synthesized GNHs were fully characterized by using FTIR spectroscopy, thermogravimetric analysis, EDAX spectrum, SEM, TEM, and AFM images, and a mechanism for superabsorbent hydrogel nanocomposite formation was suggested. Swelling kinetics in double-distilled water and the absorbency were also investigated. Furthermore, the on–off switching behaviors of the nanocomposite at different pHs were investigated. Doxorubicin hydrochloride is a chemotherapeutic drug and a hydrophilic molecule, with nitrogen and oxygen in its chemical structure. Because nitrogen and oxygen can bind to gold surfaces with high affinity, most frequently nitrogen- and oxygen-modified ligands are used as stabilizing agents, which interact with the surface of the AuNPs by formation of Au–nitrogen and Au–oxygen bonds. This Au nanoparticle–drug conjugate can be incorporated into the bio-based hydrogel matrices to make a hydrogel nanocomposite system. The pH response of this GNH makes it suitable for acting as a controlled drug delivery system. Furthermore, the role of AuNPs in effective release of doxorubicin is discussed by comparing the release in hydrogel and nanocomposite systems.

Role of Organic Carbonyl Moiety and 3-Aminopropyltrimethoxysilane on the Synthesis of Gold Nanoparticles Specific to pH- and Salt-Tolerance

The synthesis of gold nanoparticles (AuNPs) having better dispersibility and catalytic ability than the conventional AuNPs is the challenging task. The fact that aldehydes and ketones results in the formation of catalytic hybrid material with amino functionalized silanes directed the use of carbonyl functional group (aldehydes and ketones) specifically formaldehyde, acetaldehyde, acetone and t-butyl methyl ketone alongwith 3-aminopropyltrimethoxysilane (3-APTMS) to meet such requirement. Accordingly, a comparative study on the synthesis of 3-APTMS and organic reducing agent mediated synthesis of AuNPs are reported herein. The findings reveal that 3-APTMS capped gold ions are converted into AuNPs with precise control of pH- and salt- sensitivity. The major findings reveal the following: (1) 3-APTMS being amphiphilic, dispersibility of as prepared AuNPs largely depends on the organic reducing agents. (2) An increase in the hydrocarbon content of the reducing agent facilitate the dispersibility of AuNPs in organic solvent whereas decrease of the same increases the dispersibility in water, (3) AuNPs made through aldehydic reducing agents (formaldehyde and acetaldehyde) have relatively better salt and pH tolerance as compared to ketonic reducing agents (acetone, t-butyl methyl ketone), and (4) an increase in 3-APTMS concentrations imparts better salt- and pH- resistant property to AuNPs irrespective of organic reducing agents. A typical example on the role of AuNPs in homogeneous catalysis during potassium ferricyanide mediated oxidation of ascorbic acid is also reported.

Gold nanoparticles supported on mesoporous silica: origin of high activity and role of Au NPs in selective oxidation of cyclohexane.

Homogeneous immobilization of gold nanoparticles (Au NPs) on mesoporous silica has been achieved by using a one-pot synthesis method in the presence of organosilane mercapto-propyl-trimethoxysilane (MPTMS). The resultant Au NPs exhibited an excellent catalytic activity in the solvent-free selective oxidation of cyclohexane using molecular oxygen. By establishing the structure-performance relationship, the origin of the high activity of mesoporous supported Au catalyst was identified to be due to the presence of low-coordinated Au (0) sites with high dispersion. Au NPs were confirmed to play a critical role in the catalytic oxidation of cyclohexane by promoting the activation of O2 molecules and accelerating the formation of surface-active oxygen species.

Multi-layered nanocomposite dielectrics for high density organic memory devices

We fabricated organic memory devices with metal-pentacene-insulator-silicon structure which contain double dielectric layers comprising 3D pattern of Au nanoparticles (Au NPs) and block copolymer (PS-b-P2VP). The role of Au NPs is to charge/discharge carriers upon applied voltage, while block copolymer helps to form highly ordered Au NP patterns in the dielectric layer. Double-layered nanocomposite dielectrics enhanced the charge trap density (i.e., trapped charge per unit area) by Au NPs, resulting in increase of the memory window (ΔVth).

Photovoltaic Performance of Plasmonic Thin Films with Different Structure of Au and TiO2

Metal-oxide nanostructures with Surface Plasmon Resonance (SPR) have been introduced to improve the light absorption ability of dye sensitized solar cells (DSSCs) so that the energy conversion efficiency can be enhanced. It should be noted that the structure of metal nanoparticles and the oxide substrate greatly influence the performance of the solar cells, both to utilize SPR to the fullest and to overcome the drawbacks such as charge recombination involved with metal nanopar- ticles. We studied the morphology of spin-coated thin films with different structures of Au and TiO2, FTO/TiO2/Au NPs, FTO/Au NPs/TiO2 and FTO/TiO2/Au/TiO2 and examined the surface plasmon resonance effect on the light absorption ability and energy conversion behavior of dye sensitized solar cells with the as fabricated thin films as photo anodes. Electrode with Au NPs loaded on the top of TiO2 thin film showed improved optical absorption in the visible region compared to the control sample of TiO2 due to the surface plasmon resonance of Au NPs. However, the dye sensitized TiO2-Au NPs films showed decreased photocurrent under illumination due to the charge recombination caused by bare Au NPs. On the other hand, when Au NPS were loaded beneath the TiO2 film, the plasmonic electrode exhibited a 37% enhancement and increased incident photon-to-photocurrent efficiency (IPCE) in consistent with the improvement in absorption spectrum. To further confirm the role of Au NPs in the plasmonic films, the sandwich-like structure of TiO2-Au-TiO2 was introduced, behaving improved photovoltaic performance compared to the control TiO2 electrode. Such results reveal that the design of structure can be of great importance to identify the favorably enhanced direction of plasmonic structure resulting from plasmonic scattering to trap light which confines light within the active TiO2 layer to promote DSSCs. Dipole Discrete Approximation (DDA) simu- lation feedback supported the experimental results. This concept is applicable to potential plasmonic devices for DSSCs. Keywords plasmonic thin film; metal nanostructure; DSSC; photovoltaic performance

An Intrinsic Therapy of Gold Nanoparticles in Focal Cerebral Ischemia-Reperfusion Injury in Rats

Ischemic stroke is a leading cause of death and disability, and the treatment options are limited. Recent studies demonstrated that the promising applications of gold nanoparticles (Au-NPs) as intrinsic therapeutics; however, little is known about the effect of Au-NPs on cerebral ischemia-reperfusion (I/R) injury. In this paper, the role of Au-NPs on cerebral I/R injury in the rat middle cerebral artery occlusion (MCAO) model was investigated using citrate-capped 5 nm and 20 nm Au-NPs. It was found that 20 nm Au-NPs administration led to remarkable amelioration of neurologic deficits and infarction volumes. Further research revealed that 20 nm Au-NPs elevated the production of anti-inflammatory cytokines, as well as inhibited I/R induced activation of astrocytes and microglias. Moreover, the expressions of anti-apoptotic proteins were up-regulated and the pro-apoptotic molecules were down-regulated in the post-ischemic brains. These effects were opposite in 5 nm group. The above results showed that the neuroprotection of 20 nm Au-NPs was attributable to its anti-inflammatory and anti-apoptotic effect. This study could provide a novel strategy for the treatment of cerebral I/R injury.