Adding Gold Nanoparticles Research Articles

Achieving Low Voltage Plasma Discharge in Aqueous Solution Using Lithographically Defined Electrodes and Metal/Dielectric Nanoparticles.

Because of the high dielectric strength of water, it is extremely difficult to discharge plasma in a controllable way in the aqueous phase. By using lithographically defined electrodes and metal/dielectric nanoparticles, we create electric field enhancement that enables plasma discharge in liquid electrolytes at significantly reduced applied voltages. Here, we use high voltage (10-30 kV) nanosecond pulse (20 ns) discharges to generate a transient plasma in the aqueous phase. An electrode geometry with a radius of curvature of approximately 10 μm, a gap distance of 300 μm, and an estimated field strength of 5 × 106 V/cm resulted in a reduction in the plasma discharge threshold from 28 to 23 kV. A second structure had a radius of curvature of around 5 μm and a gap distance of 100 μm had an estimated field strength of 9 × 106 V/cm but did not perform as well as the larger gap electrodes. Adding gold nanoparticles (20 nm diameter) in solution further reduced the threshold for plasma discharge to 17 kV due to the electric field enhancement at the water/gold interface, with an estimated E-field enhancement of 4×. Adding alumina nanoparticles decorated with Pt reduced the plasma discharge threshold to 14 kV. In this scenario, the emergence of a triple point at the juncture of alumina, Pt, and water results in the coexistence of three distinct dielectric constants at a singular location. This leads to a notable concentration of electric field, effectively aiding in the initiation of plasma discharge at a reduced voltage. To gain a more comprehensive and detailed understanding of the electric field enhancement mechanism, we performed rigorous numerical simulations. These simulations provide valuable insights into the intricate interplay between the lithographically defined electrodes, the nanoparticles, and the resulting electric field distribution, enabling us to extract crucial information and optimize the design parameters for enhanced performance.

One-pot rapid and ultrasensitive sensing strategy for endocrine disruptor bisphenol A using cationic AuNPs and aptamer

A novel Cys-Lys-Arg-Lys-Arg-Lys-Arg peptide-capped cationic gold nanoparticles were synthesized by the utilization of microwave irradiation. The prepared gold nanoparticles along with bisphenol A aptamer have been employed for the development of a colorimetric aptasensor for bisphenol A based on the electrostatic interactions among them and the specific recognizing ability of aptamer. The presence of bisphenol A initiated the formation of bisphenol A-aptamer complex, thus added gold nanoparticles remain stable in the reaction mixture, and corresponding to this very less charge occurs into the surface plasmon resonance peak. Depending on the concentration of bisphenol A, a particular amount of free aptamer was present in the reaction which causes the aggregation of gold nanoparticles, and corresponding to this bisphenol A was detected. Under the optimized conditions, bisphenol A concentrations from 200 to 1000 pM exhibited a good linear correlation (R2 = 0.99581) with a detection limit of 87.04 pM in 7 min. The aptameric ability was studied by replacing the bisphenol A with its other analogues such as bisphenol B, bisphenol F, phenol, and benzophenone, and also in the mixture of all these. The obtained results have shown that the developed aptasensor exhibited five-fold selectivity towards bisphenol A as compared to its other analogues. Utilization of the proposed aptasensor was carried out in mineral water, tap water, and packed juice where the percentage recovery was found from 96.61 to 101.23. Thus, the developed colorimetric aptasensor exhibits excellent advantages of rapidity, simplicity, cost-effectiveness, high selectivity, and sensitivity for bisphenol A.

Plasma-induced nanoparticle aggregation for stratifying COVID-19 patients according to disease severity

Stratifying patients according to disease severity has been a major hurdle during the COVID-19 pandemic. This usually requires evaluating the levels of several biomarkers, which may be cumbersome when rapid decisions are required. In this manuscript we show that a single nanoparticle aggregation test can be used to distinguish patients that require intensive care from those that have already been discharged from the intensive care unit (ICU). It consists of diluting a platelet-free plasma sample and then adding gold nanoparticles. The nanoparticles aggregate to a larger extent when the samples are obtained from a patient in the ICU. This changes the color of the colloidal suspension, which can be evaluated by measuring the pixel intensity of a photograph. Although the exact factor or combination of factors behind the different aggregation behavior is unknown, control experiments demonstrate that the presence of proteins in the samples is crucial for the test to work. Principal component analysis demonstrates that the test result is highly correlated to biomarkers of prognosis and inflammation that are commonly used to evaluate the severity of COVID-19 patients. The results shown here pave the way to develop nanoparticle aggregation assays that classify COVID-19 patients according to disease severity, which could be useful to de-escalate care safely and make a better use of hospital resources.

DSB and SSB damages by 0.1–20 MeV protons enhanced by high-Z nanoparticles computed using Geant4-DNA

The interaction of protons in the energy range of 0.1 to 20 MeV with water sphere, as the target volume, containing DNA molecules has been simulated using Geant4-DNA toolkit. PDB format of DNA was used as DNA molecules were distributed randomly inside the target volume. The number of DNA damage is calculated in the absence of nanoparticles. Then the simulation has been repeated in the presence of 3 different nanoparticles (gold, gadolinium and iodine), in the identical physical and geometric conditions. The number of DNA damages without nanoparticles was in agreement with previous studies. Simulations results demonstrate that adding gold nanoparticles leads to increase damage yields in DNA. Increase of the yield between 10% to 50% were observed for SSB and DSB. Enhancement of the yield damage in the case of gadolinium and iodine nanoparticles was observed to be 4% and 9% less than that of gold nanoparticles.

WITHDRAWN: Design and evaluation of a novel Kaolin-chitosan/gold nanocomposite for the treatment of human lung cancer

• Kaolin-CS/Au nanocomposite have antioxidant potentials against free radicals DPPH. • Kaolin-CS/Au nanocomposite have anti-human lung cancer properties. Kaolin-chitosan (Kaolin-CS) is an interesting bio composite with applications in formulating the anticancer supplements. Thus, the purpose of this study is to prepare Kaolin-CS/Au nanocomposite by adding gold nanoparticles (Au NPs) to modify Kaolin with chitosan. The significance of this study is the novel initiative to combine the gold nanoparticle with inexpensive kaolin clay and utilization of them as anticancer agent. Through transmission electron microscopy, we found that the presence of CS could effectively prevent the agglomeration of gold nanoparticles on the surface of Kaolin. The Kaolin-CS/Au nanocomposite were characterized by electron microscopy (SEM and TEM), energy dispersive X-ray spectroscopy (EDX), elemental mapping, X-ray diffraction (XRD) and inductively coupled plasma-optical emission spectroscopy (ICP-OES). In the cellular and molecular part of the recent study, the treated cells with Kaolin-CS/Au nanocomposite were assessed by MTT assay for 48h about the cytotoxicity and anti-human lung carcinoma properties on normal (HUVEC) and lung carcinoma cell lines i.e. NCI-H661, NCI-H1563, and NCI-H1299. The IC50 of Kaolin-CS/Au nanocomposite were 138, 144, and 138 µg/mL against NCI-H661, NCI-H1563, and NCI-H1299 cell lines, respectively. The viability of malignant lung cell lines reduced dose-dependently in the presence of Au NPs-Kaolin nanocomposite.

Nanocomposite Conductive Bioinks Based on Low-Concentration GelMA and MXene Nanosheets/Gold Nanoparticles Providing Enhanced Printability of Functional Skeletal Muscle Tissues.

There is a growing need to develop novel well-characterized biological inks (bioinks) that are customizable for three-dimensional (3D) bioprinting of specific tissue types. Gelatin methacryloyl (GelMA) is one such candidate bioink due to its biocompatibility and tunable mechanical properties. Currently, only low-concentration GelMA hydrogels (≤5% w/v) are suitable as cell-laden bioinks, allowing high cell viability, elongation, and migration. Yet, they offer poor printability. Herein, we optimize GelMA bioinks in terms of concentration and cross-linking time for improved skeletal muscle C2C12 cell spreading in 3D, and we augment these by adding gold nanoparticles (AuNPs) or a two-dimensional (2D) transition metal carbide (MXene nanosheets) for enhanced printability and biological properties. AuNP and MXene addition endowed GelMA with increased conductivity (up to 0.8 ± 0.07 and 0.9 ± 0.12 S/m, respectively, compared to 0.3 ± 0.06 S/m for pure GelMA). Furthermore, it resulted in an improvement of rheological properties and printability, specifically at 10 °C. Improvements in electrical and rheological properties led to enhanced differentiation of encapsulated myoblasts and allowed for printing highly viable (97%) stable constructs. Taken together, these results constitute a significant step toward fabrication of 3D conductive tissue constructs with physiological relevance.

PHAN-THIEN-TANNER NANOFLUID FLOW WITH GOLD NANOPARTICLES THROUGH A STENOTIC ELECTROKINETIC AORTA: A STUDY ON THE CANCER TREATMENT

The present study deals with a new novel scheme to cure a deadly disease, i.e., cancer, by adding gold nanoparticles (AuNPs) in the blood. Gold nanoparticles have promising properties that make them supreme compared with other nanoparticles for drug delivery. The hyaluronic acid-coated cisplatin conjugated AuNPs have been used to transport cisplatin into the targeted place and gained a synergistic impact by utilizing laser treatment. The Phan-Thien-Tanner (PTT) fluid model is contemplated to examine the rheology of blood moving through a tapered artery along with stenosis. Two forms of the PTT fluid model have been discussed explicitly to analyze the flow pattern. First, the impact of electrostatic potential and constriction of gold nanoparticles are considered. Second, lubrication theory is applied to formulate mathematical modeling. The resulting nonlinear system in the implicit forms is solved numerically using the Rung-Kutta-Merson scheme (RKMS) with a combination of shooting technique. The impact of velocity, wall shear stress, temperature, and nanoparticle concentration is deliberated against numerous leading parameters. A comparative analysis is also shown through graphs betwixt exponential and linearized models. Moreover, different cases of arteries have also been discussed through graphs. It is noticed that the effects of electroosmotic parameter m and the Brownian motion diffusion parameter Br will oppose the fluid motion, which enhances the shear stress. The thermophoresis and Brownian motion parameters generate a higher temperature, further rising by the golden nanoparticles because of their sizeable atomic number. A significant change in the gold nanoparticle concentration is noticed after increasing the Joule heating parameter because the gold nanoparticles absorb the internal heat and lean to propagate in the converse stream.

Evaluation of dose enhancement with gold nanoparticles in kilovoltage radiotherapy using the new EGS geometry library in Monte Carlo simulation

<abstract><sec> <title>Purpose</title> <p>This study compared the dose enhancement predicted in kilovoltage gold nanoparticle-enhanced radiotherapy using the newly developed EGS lattice and the typical gold-water mixture method in Monte Carlo simulation. This new method considered the gold nanoparticle-added volume consisting of solid nanoparticles instead of a gold-water mixture. In addition, this particle method is more realistic in simulation.</p> </sec><sec> <title>Methods</title> <p>A heterogeneous phantom containing bone and water was irradiated by the 105 and 220 kVp x-ray beams. Gold nanoparticles were added to the tumour volume with concentration varying from 3–40 mg/mL in the phantom. The dose enhancement ratio (DER), defined as the ratio of dose at the tumour with and without adding gold nanoparticles, was calculated by the gold-water mixture and particle method using Monte Carlo simulation for comparison.</p> </sec><sec> <title>Results</title> <p>It is found that the DER was 1.44–4.71 (105 kVp) and 1.27–2.43 (220 kVp) for the gold nanoparticle concentration range of 3–40 mg/mL, when they were calculated by the gold-water mixture method. The DER was slightly larger and equal to 1.47–4.84 (105 kVp) and 1.29–2.5 (220 kVp) for the same concentration range, when the particle method was used. Moreover, the DER predicted by both methods increased with an increase of nanoparticle concentration, and a decrease of x-ray beam energy.</p> </sec><sec> <title>Conclusion</title> <p>The deviation of DER determined by the particle and gold-water mixture method was insignificant when considering the uncertainty in the calculation of DER (2%) in the nanoparticle concentration range of 3–40 mg/mL. It is therefore concluded that the gold-water mixture method could predict the dose enhancement as accurate as the newly developed particle method.</p> </sec></abstract>

Photocurrent enhancement estimation of P3HT:PCBM:Au films as a function of gold nanoparticles concentration

This report provides a method to estimate how much the photocurrents can be increased by adding gold nanoparticles in P3HT:PCBM films, without having to carry out the complex process of fabricate a whole cell. The tuning effect of varying the gold nanoparticle concentration on optical properties of these films was analyzed by measuring optical absorption. To estimate the contribution of the optical absorption variation, theoretical photocurrents generated for these films as active layers were calculated using a photonic flux density equation. With this methodology, it is possible to estimate the amount of energy that can be harvest with a given gold nanoparticle concentration. Improvements up to 26% were obtained compared with films without added gold nanoparticles.

Comparison of Colorimetric Analyses to Determine Cortisol in Human Sweat.

Colorimetric analysis, which relies on a chemical reaction to facilitate a change in visible color, is a great strategy for detecting cortisol, which is necessary to diagnose and manage the wide variety of diseases related to the hormone, because it is simple in design, inexpensive, and reliable as a standard cortisol analysis technique. In this study, four different colorimetric cortisol analyses that use various chromogens, which include sulfuric acid, Porter–Silber reagent, Prussian blue, and blue tetrazolium, are studied. Modifications to the classic Porter–Silber method are made by increasing the carbon content of the alcohol and adding gold nanoparticles, which result in a twofold increase in reaction rate and a slight decrease in the limit of detection (LoD). After a comparison of the reaction rate, LoD, dynamic range, characteristic peaks, and color stability of all methods, blue tetrazolium demonstrates a low LoD (97 ng/mL), broad dynamic range (0.05–2 μg/mL), and quick reaction rate (color development as fast as 10 min), which are well within the requirements for human biofluids. Cortisol in artificial saliva and sweat and in human sweat was determined while confirming that no excipients or other biomarkers interfered with the reactions. Twenty-one human sweat samples were tested using blue tetrazolium and revealed a significant difference between male and female apocrine cortisol concentrations and showed a highly significant difference between apocrine and eccrine cortisol concentrations. Colorimetric methods of cortisol can compete with existing electrochemical sensors because of their similar accuracy and detection range in certain wearable biosensor applications. The simplicity of colorimetric methods advances potential applications in skin-interfaced bio-electronics and point-of-care devices.

Inkjet-printed lasing silk text on reusable distributed feedback boards

Inkjet printing is an attractive bottom-up microfabrication technology owing to its simplicity, ease of use, and low cost. This method is particularly suitable for patterning of biomaterials because biofunctionality and bioactivity can be preserved during the patterning process in the absence of harsh conditions such as heat, UV radiation, and plasma. However, it is still challenging to apply this technology to biomaterial-based soft photonics, which requires precise control over morphology and uniformity to confine photons efficiently. This study introduces inkjet printing to create silk protein patterns to emit/guide a single-mode distributed feedback (DFB) laser on a single platform. A thin TiO2 coated grating enables coherent feedback of the generated photons for any shape of the printed silk pattern. The lasing wavelength can be adjusted by adding gold nanoparticles to the silk/dye ink. Photonic components of lasers and waveguides are drawn on a DFB board, and the lasing light can be extracted through adjacent waveguides. The printed components can be reformed by post modification (water-removal and reprinting). Additionally, optically absorptive melanin nanoparticles placed on the waveguide can attenuate the propagating light, thus adding utility for sensing applications. This allows a new method to fabricate cost-effective, easily functionalized, and versatile biomaterial photonic chips for advanced sensing and diagnosis.

Evaluation of New Film Based on Chitosan/Gold Nanocomposites on Antibacterial Property and Wound‐Healing Efficacy

Chitosan (CS) is a natural polymer with applications in wound restorations and coatings for artificial implants. However, the lack of antimicrobial activity restricts its further application. Thus, the purpose of this study is to prepare CS/AuNPs film by adding gold nanoparticles (AuNPs) to modify chitosan. Through transmission electron microscopy, we found that the presence of CS can effectively prevent the agglomeration of nanoparticles. Furthermore, through the CCK experiment, we found that AuNPs at a certain concentration can improve the adhesion and proliferation of cells, which has also been proved in animal experiments, including gross appearance, histological observations, and immunofluorescence staining. Such findings support the feasibility of using the film as a promising candidate for tissue engineering of skin in a near future.

The role of gold nanoparticles in the structural and electrical properties of Cs/PVP blend

Pure gold nanoparticles (AuNPs) were prepared using a laser ablation technique. Nanocomposite films of chitosan (Cs) and polyvinyl pyrrolidone PVP blend embedded different concentrations of pure gold nanoparticles were prepared by the casting method. The structural, morphological, thermal and electrical properties of Cs/PVP–AuNPs nanocomposite were characterized and investigated before and after adding gold nanoparticles. The X-ray diffraction revealed the degree of crystallinity of Cs/PVP blend was decreased after the addition of gold nanoparticles. The intensity of some IR bands was changed due to the chemical interaction between the blend and AuNPs. Transmission electron microscope images of the samples which contain the gold nanoparticles show the spherical particles of nanogold with a size range nearly 5–30 nm. The thermogravimetric (TG) analysis shows an enhancement of the thermal stability of the films after the addition of AuNPs. The activation energy was calculated from the TG curves using Coats–Redfern and Broido methods. The AC electrical properties were studied from 100 Hz to 5 MHz with different temperatures. The values for dielectric constant (e′) and dielectric loss (e″) were decreased with an increase in both frequency and temperature.

Efficient CO (carbon monoxide) oxidation using gold catalysts supported on WO3/titanate protonated nanotubes

WO3/titanate protonated nanotubes used to disperse gold nanoparticles were prepared by the deposition-precipitation with urea method and tested in CO oxidation reaction. Remarkably enhanced CO oxidation activity was achieved with the addition of gold nanoparticles with respect to WO3/NT and Au/NT catalysts. XPS and H2/TPR showed that when the samples were activated at 400 °C under hydrogen treatment, gold was present in the metallic Au0 form and tungsten as W5+ and W6+ species; likewise, the addition of tungsten to the tubular morphology led to the formation of vacancies and new adsorption sites, preserving the structure at up to 400 °C. The interaction between WO3 and the titanate nanotubes was improved by adding gold nanoparticles with sizes around 1 and 3 nm under hydrogen treatment, increasing the content of reduced W5+ species that promoted the CO oxidation at low temperatures. The 2Au-3WO3/NT catalyst was active from 0 °C and showed temporary stability at room temperature.

An investigation of the effect of gold nanoparticles with different concentrations on increasing absorbed dose: an empirical and simulation study

AbstractPurposeThe purpose of this study was to determine the dose enhancement factor (DEF) of gold nanoparticles in a dosimeter gel and construct percentage depth dose curves, using the Optical CT system and the Monte Carlo simulation model, to determine the effect of increasing the dose caused by increasing the concentration of gold nanoparticles at depths in the gel.Materials and methodsThe Magic-f Gel was made based on the relevant protocol in the physics lab. To determine the amount of the increase in the absorbed dose, the gold nanoparticles were added to the gel and irradiated. An increase in the dose after adding nanoparticles to the gel vials was estimated both with the Optical CT system and by the Monte Carlo simulation method.ResultsDose enhancement curves for doses of 2, 4 and 6 Gy were prepared for gel vials without adding nanoparticles, and nanoparticle gels at concentrations 0·17, 3 and 6 mM. Also, the DEF was estimated. For the 0·17 mM molar gel, the DEF for 2, 4 and 6 Gy was 0·7, 0·743 and 0·801, respectively. For the 3 mM gel, it was 1·98, 2·5 and 2·2, and for the 6 mM gel, it was 37·4, 4·24 and 4·71, respectively.ConclusionThe enhancement of the dose after adding gold nanoparticles was confirmed both by experimental data and by simulation data.

Efficiency improvement of up-conversion process of plasmonic-enhanced Er-doped-NaYF4 nanoparticles under IR excitation.

The up-conversion process is extensively studied because of its wide variety of applications such as bioimaging, energy harvesting, and optical sensors. However, the optical conversion efficiency is still relatively low and needs to be improved. Therefore, this paper introduces a detailed study of improving the up-conversion emission efficiency through adding plasmonic metallic nanostructures to the up-conversion optical centers. Our idea is to couple the optical plasmonic resonance with the visible emission of the optical centers under IR excitation. The optical centers are erbium ions hosted by fluoride low-phonon environment. Our calculations consider most possible transitions that can occur between the optical centers; tri-valent erbium ions, through Judd-Ofelt analysis. In addition, the effect of changing some parametric values is discussed, such as irradiance, and multi-phonon relaxations, to show their optimum values which correspond to best quantum yield efficiency. By increasing the diameter of added gold nanoparticles (Au NPs), the probability of occupation has been increased, and consequently, both the luminescence and up-conversion efficiency have been increased.

Plasmonic-Ceria Nanoparticles as Fluorescence Intensity and Lifetime Quenching Optical Sensor.

Ceria nanoparticles have been recently used as an optical fluorescent material with visible emission under ultraviolet excitation, due to the formation of trivalent cerium ions with corresponding oxygen vacancies. This paper introduces the enhancement of both fluorescence emission and lifetime through adding gold nanoparticles. The reason is due to possible coupling between the plasmonic resonance of gold nanoparticles and the fluorescence emission of ceria that has been achieved, along with enhanced formation of trivalent cerium ions. Both factors lead to higher fluorescence intensity peaks and shorter fluorescence lifetimes. As an application, gold-ceria nanoparticles have been used as an optical sensing material for lead particles in aqueous media based on fluorescence quenching. Stern-Volmer constant of in-situ gold-ceria nanoparticles is found to be 2.424 M−1, with a relative intensity change of up to 40% at 0.2 g/L.

Impact of plasmonic nanoparticles on up-conversion luminescence and efficiency of erbium-doped ceria nanoparticles under 780 nm excitation

Up-conversion process is being widely studied due to its enormous applications such as bioimaging, energy harvesting, and optical sensors. However, the low conversion efficiency can limit these applications. In this paper, a detailed study about the effect of using plasmonic metallic nanostructures is presented, aiming to support the up-conversion process under 780 nm excitation. The targeted material is erbium-doped ceria material due to its promising optical properties along with the relatively low-phonon nature of ceria host. At an average distance of 0.67 nm between Er ions, the efficiency can be improved from 1.58% to 13.52% for green emission and from 0.007% to 0.234% for the red one, which corresponds to 30-fold and 8.5-fold, respectively. Also, some other parameters such as irradiance and multi-phonon relaxations and their impact on the efficiency, according to the added gold nanoparticles are studied. Such promising modeling results could help in further studies regarding the addition of metallic nanoparticles to improve the quantum conversion efficiency due to its plasmonic effect.

K+ colorimetric detection in the nanomolar range based on K+-aptamer quadruplex-NPs association

This report presents a sensitive, proximity binding-induced DNA hybridization-based colorimetric assay for detecting K+ in aqueous solution. The detection mechanism is based on the fact that DNA1 and DNA2 were designed to contain the two K+ binding aptamers, the target K+ can interact with a segments of the two different DNAs to form G-quadruplex/K+ complexes and prompt DNA hybridization, thus the subsequently added gold nanoparticles (AuNPs) can be captured by the 5′ terminus of DNA1 and DNA2 through Au-S binding, leading to the aggregation of AuNPs. The color of the AuNPs changed from green to yellow and red under dark-field microscopy observation. By use of the dark-field images of the AuNPs, the lowest detectable concentration for K+ was measured to be 0.18 nM according to the 3σ/k rule. This assay allowed the detection of K+ in real serum samples. The results in detecting K+ from serum samples via this method agreed well with those from buffer.

Enhanced Optical Collection of Micro- and Nanovesicles in the Presence of Gold Nanoparticles.

We describe a process for collecting micro- and nanovesicles on a glass substrate using the optical pressure of a laser beam. The laser beam was focused on a glass substrate that sandwiched a solution containing vesicles prepared using a phospholipid. The optical pressure generated at the surface of the vesicles pulled them into the center of the beam where they formed an aggregate on the glass surface. The vesicles prepared with a buffer solution were successfully collected via adsorption onto the glass surface, whereas the vesicles prepared with pure water exhibited no such tendency. The time required to collect a certain amount of vesicles was inversely proportional to their concentration. To enhance the collection efficiency, we added gold nanoparticles to the vesicle solution. The addition of gold nanoparticles into the solution reduced the collection time to one-tenth of that without it, and this was attributed to thermal mixing promoted by the heat generated by the absorption from the gold nanoparticles in the solution, as well as to an enhancement of light scattering induced by the gold nanoparticles. The optical collection of vesicles coupled with gold nanoparticles shows a promise for the collection of trace amounts of extracellular vesicles in biological fluids.