Narrow Results

Metal nanoparticles have the ability to localize and strongly enhance the incident electromagnetic field due to the surface plasmon polariton. The coupling between AuNPs and ZnO thin films affects their emission properties. In this study, we prepared the ZnO/Al₂O₃/AuNPs multilayer films, and investigated the effect of spacer layer on enhancement and quenching of photoluminescence by surface plasmon. The emission intensities of the thin films vary when Al₂O₃ space layer with different thickness was embedded in the ZnO/Au films, consistent with theoretical predictions. The photoluminescence modulation is also made via controlling the polarization of the excitation source. The photoluminescence anisotropy of these systems shows that enhanced photoluminescence can be achieved through coupling of the emission from ZnO with the surface plasmon resonance of AuNPs.

In recent days, the number of cancer cases is escalating promptly around the world. In general, conventional ablation methods, encompassing comprehensive drawbacks, are employed to cure cancer. At present, photo thermal therapy (PTT) is showing great promise to the treatment of cancer. However, the effective implementation of this technology is utmost challenging as several parameters affect the tumor surroundings. In this work, the effects of different parameters on the performance of PTT have been thoroughly investigated by considering a realistic model of human tissue underneath the skin using a finite element solver, COMSOL Multiphysics. Two different conditions, with and without considering gold nanoparticles at tumor site, are investigated where a laser beam is used as a source of energy. Fluence rate, temperature distribution, and thermal damage are highlighted in this work. It is observed that by utilizing a miniature needle with integrated waveguide and gold nanoparticles, a tumor can be effectively eradicated along with assuaging the conventional drawbacks of PTT. This study would also be useful for designing operative PTT for different parts of human tissue.

We investigate the effect of gold nanoparticles capped by Citrate (Au-CA) and 3-MPA (Au-MPA) addition into PEDOT:PSS as an anode buffer layer (ABL) in the structure of an inverted hybrid solar cell. The localized surface plasmon resonance (LSPR) excited in AuNP is expected to accelerate the transfer of holes to the anode (Ag), increasing the mobility of charge carriers in this type of solar cell. The measured UV–visible absorption spectra show typical representation of the PEDOT:PSS mixtures, which changed due to modification of Au-NP’s concentrations. The maximum absorption peak of Au-CA solution ($d=\sim 13.8$nm) is located around 522nm, while Au-MPA solution ($d=\sim 25.7$nm) is located around 528nm. These peaks are found to be red-shifted including the absorbance intensity increased when they are modified with that of PEDOT:PSS. Under the illumination of 100mW/cm² simulated solar irradiation, the fabricated solar cell device exhibits an increase of Power Conversion Efficiency (PCE) value from 1.02% to 2.38% for the device with the addition of 20.0v/v% Au-CA and to 2.44% for the device with the addition of 2.0v/v% of Au-MPA. In our case, the enhancement of open circuit voltage ($V_{\mathrm{\text{OC}}}$) and short circuit current density ($J_{\mathrm{\text{SC}}}$) together occurs as a result of localized electric field effects from AuNP that influence charge transport and also the work function at the interface between PEDOT:PSS and the Ag-electrode. In our result, the fabricated solar cell with the addition of Au-MPA into the device structure shows a better performance efficiency of about 2.44% in comparison to the device with the addition of Au-CA of about 2.38%.

JAPAN – Nanomaterial wrap for improved tissue imaging.

USA – Test strips for cancer detection get upgraded with nanoparticle bling.

SINGAPORE – A*STAR’s IMB discovers ELABELA protects against cardiovascular malformations in mice.

SINGAPORE – NUS scientists combine antimalarial drug with light sensitive molecules for promising treatment of cancer.

INDIA – A novel antifungal molecule discovered in bacteria.

MALAYSIA – Fermenting fish to reduce cholesterol.

We have studied the construction and electronic characteristics of a series of devices made from gold microgap electrodes, gold nanoparticles and conjugated oligothiophene dithiols. The formations of gold nanoparticle/oligothiophene dithiol composites on gold surface were monitored by quartz crystal microbalance (QCM) using gold electrode coated crystal oscillator. The formation speed was the fastest for terthiophene dithiol followed by hexathiophene and nanothiophene dithiols, the latter two showed almost the same formation speed. The current–voltage (I/V) curves of these devices were measured at various temperatures to show that at high temperature (>200 K) they were almost straight line; at lower temperature they became parabolic, and at 4 K a completely blocked region appeared between -12 to +12 V. We attributed the parabolic I/V curve to a tunneling mechanism and the blocked region to the Coulomb blockade phenomena.

Inkjet printing technology has emerged as major contender for large area electronics. The major challenge for this technology is the development of suitable conductive ink to obtain high quality patterns with desired electrical conductivity comparable to metals. The conductive ink should have good film formability on the flexible substrate as well as lower annealing temperature compatible with plastic substrates. Gold nano particle (AuNP) is the material of choice due to its very low sintering temperature in addition to excellent electrical property and resistance to corrosion. We have synthesized the butanethiol encapsulated Au-NP by the Brust method. We demonstrate a sintering temperature as low as 150°C for butanethiol capped gold nanoparticles of size less than 2 nm. The conductive gold films obtained after transformation have been investigated using four point probe method to measure sheet resistance as a function of process time. We show that the electrical properties degrade as annealing time increases. The reason for changes in electrical property has been investigated using SEM, TEM and XRD. The decrease in conductivity is traced to the formation of large micron sized gold crystallites on the film surface at temperatures as low as 160°C.

Hybrid nanomaterials consisting of functionalized fullerene and gold nanoparticle (NP) have been synthesized. Fullerene was functionalized by citric acid and used as reducing and capping agent for preparation of gold NPs. Functionalization of fullerene by use of citric acid was performed by enzymatic and thermal approaches. The core-shell structures containing gold NPs as core and fullerene as shell (gold/fullerene) were prepared. It was found that method and density of functionalization of fullerene effect final structure and therefore their physicochemical property of hybrid nanomaterial dramatically. Ultraviolet-visible (UV-Vis) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, dynamic light scattering (DLS), atomic force microscopy (AFM), transmission electron microscopy (TEM) were used to analyze the structure of the synthesized hybrid nanomaterial and also study their self-assembly and physicochemical properties. Effect of the size, structure and morphology (e.g., agglomeration) of the synthesized hybrid nanomaterial on their UV-Vis absorption behavior has been also verified by theoretical modeling.

In this computational study, the interaction between a single layer graphene sheet and a gold nanoparticle is investigated employing molecular dynamics (MD) simulation at room temperature. The interactions between the graphene and gold nanoparticle were explored for three different types of gold nanoparticle, namely, bare gold nanoparticle, methyl terminated alkane thiol-coated gold nanoparticle and hydroxy terminated alkane thiol-coated gold nanoparticle. The interactions between the graphene and gold nanoparticle have resulted in the adsorption of gold nanoparticle on the surface of graphene. The structural properties of the graphene–gold hybrid nanostructures were found to be influenced by the capping layer of the gold nanoparticle.

Reported was a novel amperometric immunosensor based on layer-by-layer (LbL) assembled polyethylenimine/gold nanoparticles/poly (acrylic acid) (PEI/AuNPs/PAA) multilayer. The assembly process was in situ monitored by surface plasmon resonance (SPR) technique. Anti-goat IgG as a capture antibody was covalently immobilized on the outermost PAA layer of the multilayer to construct an immunosensor. A target protein, goat IgG was electrochemically detected with alkaline phosphatase-conjugated anti-goat IgG (ALP-anti-goat IgG) as a recognition antibody. Electrochemical investigations suggest that the incorporation of AuNPs facilitates the electron transfer between the underlying electrode and the redox species in solution, and thus enhances the electrochemical signals and in turn improves the immunosensing performance. A detection limit of 100 pg mL^-1 with a dynamic range of five orders of magnitude was achieved. Due to the protein-friendly environment and the protein resistance of the polyelectrolyte multilayer, the resulting immunosensor demonstrates excellent storage stability, satisfying assay specificity.

This work reports on the synthesis and characterization of a new gold nanoparticle-zinc phthalocyanine system, AuNP-S(^tBu)₃ZnPc, prepared by a ligand exchange reaction of tetraoctylammonium bromide with a novel unsymmetrically substituted zinc phthalocyanine which contains one thioester group in the peripheral position [AcS(^tBu)₃ZnPc]. The AuNP-S(^tBu)₃ZnPc hybrid was characterized using UV-vis and ¹H NMR spectroscopies. Transmission electron microscopy allowed the estimation of the size, which was calculated to be ~5 nm. AuNPs-S(^tBu)₃ZnPc conjugate showed much lower fluorescence quantum yield values than the AcS(^tBu)₃ZnPc demonstrating either an energy or electron transfer from the ZnPc to the AuNP. The AuNP-S(^tBu)₃ZnPc hybrid has been anchored to a TiO₂ semiconducting layer using lipoic acid. A solid configuration of TiO₂-lipoic acid-AuNP-S(^tBu)₃ZnPc has been prepared by anchoring lipoic acid to the TiO₂ (TiO₂-LA) and introducing later the TiO₂-LA with free thiol groups in a toluene solution of AuNP-S(^tBu)₃ZnPc. We have also observed by UV-vis and fluorescence measurements the importance of the ZnPc in avoiding AuNP aggregation on the TiO₂ surface.

Prostate cancer is a leading health burden, the third most common cancer in a man. High accuracy detection and screening methods with a suitable biomarker can significantly reduce the risk of mortality. Prostate specific antigen (PSA) is the efficient and acceptable biomarker due to its level of increment in the biological fluid with the prostate cancer patient. This research was focused to establish a sensitive method of PSA detection by using gold nanoparticle (GNP) conjugated PSA specific aptamer on interdigitated mini-electrode. GNP allowed to capture higher number of aptamers on the surface and enhanced the interaction of PSA. This good detection method can determine PSA at 45aM with the sensitivity of 30aM. A linear range was noticed from 60 until 2000 aM on the regression curve at $y=0.1568x+0.143$; $R^2=0.955$. Moreover, spiking PSA in human serum enhances the current response with increasing PSA concentrations. This method of determination helps to quantify the PSA level and diagnose the prostate cancer at different stages.

Discrete biomolecule-nanoparticle (NP) conjugates play paramount roles in nanofabrication, in which the key is to get the precise molar extinction coefficient of NPs. By making best use of the gift from a specific separation phenomenon of agarose gel electrophoresis (GE), amphiphilic polymer coated NP with exact number of bovine serum albumin (BSA) proteins can be extracted and further experimentally employed to precisely calculate the molar extinction coefficient of the NPs. This method could further benefit the evaluation and extraction of any other dual-component NP-containing bio-conjugates.

Gold nanoparticles (AuNPs) used for therapeutic applications preferentially accumulate in the liver following exposure. However, uptake and clearance by hepatic cells are not well understood. Time-dependent intracellular localization, uptake and clearance of 30 nm AuNPs were monitored in primary rat hepatocytes and liver sinusoidal endothelial cells (LSECs). Confocal Raman microscopy studies demonstrated the differences in the localization of AuNPs in hepatic cells over a 24 h period. The uptake of unmodified AuNPs over 24 h was 17% and 55% for hepatocytes and LSECs. The uptake of poly(ethylene glycol)-coated AuNPs was 3% and 1% over 24 h in hepatocytes and LSECs, respectively. Both cell types expelled approximately 60–70% of intracellular AuNPs within seven days. AuNP accumulation resulted in the disruption of the pericanalicular actin between adjoining hepatocytes. These trends suggest that AuNPs may affect actin organization, which could impair hepatic function long term.

Gold nanoparticles (AuNPs) as one of the most stable metal nanoparticles have demonstrated extensive applications in recent years. In this review, the synthetic methods to AuNPs were discussed, which included citrate reduction, Brust–Schiffrin method, ligand-stabilized AuNPs and so on, followed with the synthetic mechanisms. Special emphasis was made on polymer modified AuNPs in biomedical applications, especially for polymer/AuNPs conjugated in the field of cancer therapy and early diagnosis. The applications based on optoelectronic properties, which was related to surface plasmon resonance (SPR) effect, were also summarized as biosensors for labeling and detection.

Gold nanoparticles (AuNPs) as one of the most stable metal nanoparticles have demonstrated extensive applications in recent years. This paper will give a focus on the AuNPs as biosensors, due to their inertness, unique optical properties, high surface area, and various surface functionalization methods. Synthesis of AuNps and the surface functionalization will be discussed in the first part. The size, shape, and stability can be controlled by different synthetic methods, while reductant usually needed. By surface functionalization with different molecules such as polymers, nucleic acids, and proteins, AuNPs will aggregate when specified molecule linkages showing up enables selective detections. The application in biosensing to detect proteins, oligonucleotide, glucose, and heavy metals will be exemplified, followed by the summary and future perspective part in the conclusion.

Triple-negative breast cancer (TNBC) is the most aggressive sub-type of breast cancer, mainly affecting premenopausal women. As it neither expresses hormone receptors nor overexpresses HER2 receptors, it is difficult to tackle this deadly disease effectively. It is a well-known fact that phytochemicals have remarkable therapeutic potential in the prevention and treatment of different disorders. One of the well-known phytochemicals, ellagic acid (EA) has shown better efficacy in the prevention and treatment of cancer in many preclinical and clinical settings. Therefore, in this study, ellagic acid gold nanoparticles (EA-AuNp) were synthesized and characterized to passively target TNBC cells through EPR effect. EA-AuNp were prepared using the direct reduction method and characterized by UV–Visible spectroscopy, DLS, XRD, EDX, TEM and FT-IR spectra. We found that it significantly suppressed the TNBC cell proliferation (IC${}_{50}$ 12 $\mu$g/ml) compared to EA alone (IC${}_{50}$ 36 $\mu$g/ml). Flow cytometry and live and dead assays revealed that EA-AuNp induced more cell death in TNBC cells compared to EA alone. Further, western blot analysis substantiated that EA-AuNp induced apoptosis by regulating the expression of Bcl-2, survivin, caspase 3 and caspase 9. In conclusion, EA-AuNp has high anti-cancer potential and additional preclinical and clinical studies are highly recommended.

Gold nanoparticles (GNPs) are widely used in chemical sensing, drug delivery, biomedical imaging, and photothermal therapy due to their strong and size-tunable surface plasmon resonance, fluorescence, and easy-surface functionalization. In this study, we investigated the effects of water-dispersed GNPs on the cytotoxicity and differentiation of human bone marrow mesenchymal stem cells (hBMSCs) and the associated death pathway. The results showed that the viability of hBMSCs was dependent upon the size of GNPs. Further, GNPs at the smallest size exhibited the highest cytotoxicity after treatment for 5 days and also substantially suppressed the number of colony-forming unit-fibroblast (CFU-F) of hBMSCs after continuous exposure for 21 days. Although large and medium sizes of GNPs had minor cytotoxicity to the cells, the sizes of CFU-F formed in the groups treated with GNPs at medium and large sizes were smaller compared to the control group. Further study of the cell death pathway using GNPs at medium size found that GNPs triggered hBMSCs necrosis, possibly by oxidative stress after GNPs were endocytosed. In addition, GNPs exerted the inhibitory effects on induced osteogenesis and adipogenesis of hBMSCs. Alkaline phosphatase (ALP) activity and calcium mineralization during osteogenic induction as well as the accumulation of triacylglycerides in adipogenic hBMSCs were repressed significantly by coculturing with GNPs at medium size. Our results suggest that the application of GNPs as long-term tracers for the activities of mesenchymal stem cells (MSCs) should be carefully evaluated.

We have studied the construction and electronic characteristics of a series of devices made from gold microgap electrodes, gold nanoparticles and conjugated oligothiophene dithiols. The formations of gold nanoparticle/oligothiophene dithiol composites on gold surface were monitored by quartz crystal microbalance (QCM) using gold electrode coated crystal oscillator. The formation speed was the fastest for terthiophene dithiol followed by hexathiophene and nanothiophene dithiols, the latter two showed almost the same formation speed. The current–voltage (I/V) curves of these devices were measured at various temperatures to show that at high temperature (>200 K) they were almost straight line; at lower temperature they became parabolic, and at 4 K a completely blocked region appeared between -12 to +12 V. We attributed the parabolic I/V curve to a tunneling mechanism and the blocked region to the Coulomb blockade phenomena.