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PubMed1984

Decreased airway responsiveness to histamine in gold salt-treated guinea pigs.

The effect of gold salts on airway responsiveness was examined because gold salts appear to be effective in relieving asthmatic symptoms. Seventeen guinea pigs were administered an intramuscular injection of 1 mg of gold sodium thiomalate once a week, and 10 control animals were administered an injection of saline. Three months after the start of the injections, guinea pigs administered gold salt demonstrated significantly decreased airway responsiveness to histamine assessed by respiratory flow patterns and resistance. Some guinea pigs in each group were sacrificed 3 mo after the start of injections, and cyclic nucleotides were measured in the trachea, lung homogenates, and the plasma. No difference was found in the level of adenosine cyclic 3', 5'-monophosphate or guanosine cyclic 3',5' -monophosphate in gold salt-treated animals and control animals. The way in which gold salt alleviates the symptoms of bronchial asthma is discussed on the basis of the results.

Airway Resistance↗
PubMed1993

Transpalatal insertion of radioactive gold grain for the treatment of persistent and recurrent nasopharyngeal carcinoma.

PURPOSE: To evaluate the efficacy of radioactive gold grain implant via the split palate approach in the control of locally recurrent or persistent nasopharyngeal carcinoma. METHODS AND MATERIAL: Forty-three patients, 10 for persistent NPC, 28 for first relapse in the nasopharynx, and five for second relapse in the nasopharynx, were treated. The diameter of the tumors at the time of gold grain implant ranged from 0.5 to 5 cm, the number of gold grains inserted varied from 4 to 14, the median number was seven. RESULTS: There was no significant difference in the control of the primary tumor for persistent disease (80% at 5 years), first relapse (61% at 5 years) and second relapse (80% at 3 years), p = 0.8845. The difference in survival between the three subgroups of patients, however, was highly significant (p = 0.0040). Thirty patients had CT evaluation before gold grain implant and the tumor was found confined to the nasopharynx in 21, in the remaining nine patients erosion of the sphenoid sinus or other parts of the base of skull was noted. The difference in the control between those patients with tumors confined to the nasopharynx and those patients with extranasopharyngeal extension of tumor almost reached statistical significance (81% and 44% respectively at 5 years, p = 0.0554). For the six patients who developed local recurrence after gold grain implant and were evaluable for the pattern of failure, the recurrent tumors were considered originating from another region of the nasopharynx in four, and in-field failure in the other two cases. CONCLUSION: Radioactive gold grain implant as salvage treatment provides satisfactory control of persistent and recurrent nasopharyngeal carcinoma. The local control was better when the tumor was localized to the nasopharynx, thus underlines the importance of close follow-up for early recognition of relapse and persistent tumor. However, such patients still suffered from high incidence of regional and distant failure, the pathophysiology and management of which require further investigation.

Adult↗
PubMed2004

A protein A-based orientation-controlled immobilization strategy for antibodies using nanometer-sized gold particles and plasma-polymerized film.

A novel protein A (PA)-based strategy for the orientation-controlled immobilization of antibodies using nanometer-sized gold (Nano-gold) particles and an amine-terminated plasma-polymerized film (PPF) has been proposed. A quartz crystal microbalance was fabricated, accordingly, coupling with haptoglobin (HP) antibody followed by HP immunoassay, as a model test system. The crystal was modified with plasma-polymerized n-butyl amine film to deposit Nano-gold particles and PA, on which HP antibodies were immobilized. The surface topology of the as-prepared crystal was characterized by use of scanning electron microscopy. In contrast to the traditional flat gold surface, the assembled Nano-gold particle monolayer could allow PA molecules bound with higher bioactivity and loading amount (density), achieving better antibody-binding capabilities. Results indicate that immunosensors prepared using the developed PPF-Nano-gold-PA binding procedure exhibit increased analytical performance compared with those produced using the direct PA binding procedure and the PPF-based glutaraldehyde cross-linking procedure. A HP serum concentration as low as 0.41 nM can be determined by this new system. Regenerated simply by rinsing in the acid buffer, the proposed sensor can achieve up to 11 assay cycles without significant loss of sensitivity.

Animals↗
PubMed2006

Optical detection of DNA hybridization based on fluorescence quenching of tagged oligonucleotide probes by gold nanoparticles.

A novel system for the detection of DNA hybridization in a homogeneous format is developed. This method is based on fluorescence quenching by gold nanoparticles used as both nanoscaffolds for the immobilization of capture sequences and nanoquenchers of fluorophores attached to detection sequences. The oligonucleotide-functionalized gold nanoparticles are synthesized by derivatizing the colloidal gold solution with 5'-thiolated 12-base oligonucleotides. Introduction of sequence-specific target DNAs (24 bases) into the mixture containing dye-tagged detection sequences and oligonucleotide-functionalized gold nanoparticles results in the quenching of carboxytetramethylrhodamine-labeled DNA fluorescence because DNA hybridization occurs and brings fluorophores into close proximity with oligonucleotide-functionalized gold nanoparticles. The quenching efficiency of fluorescence increases with the target DNA concentration and provides a quantitative measurement of sequence-specific DNA in sample. A linearity is obtained within the range from 1.4 to 92 nM. The target sequence is detected down to 2 nM. This new system not only overcomes many of the drawbacks inherent in radioisotopic measurement or enzyme-linked assay but also avoids the requirement for the stem-loop structure compared with conventional molecular beacons. Furthermore, the background signal that is defined as fluorescence quenching arising from electrostatic attraction between positively charged fluorophores and negatively charged gold nanoparticles is comparatively low due to electrostatic repulsion between negatively charged oligonucleotides. In addition, this is a homogeneous assay that can offer the potential to be monitored in real time, be amenable to automation, eliminate washing steps, and reduce the risk of contamination.

Biosensing Techniques↗
PubMed2005

Patterned networks of mouse hippocampal neurons on peptide-coated gold surfaces.

Patterned networks of hippocampal neurons were generated on peptide-coated gold substrates prepared by microscope projection photolithography and microcontact printing. A 19 amino acid peptide fragment of laminin A (PA22-2) that includes the IKVAV cell adhesion domain was used to direct patterns of cell adhesion in primary culture. Microscale grid patterns of peptide were deposited on gold-coated glass cover slips by soft lithography using "stamps" fashioned from polydimethylsiloxane. Strong coordination bonding between gold atoms on the surface and the sulfur atoms of the N-terminal cysteine residues supported stable adhesion of the peptide, which was confirmed by immunofluorescence using anti-IKVAV antiserum. Dispersed hippocampal cells isolated from neonatal mouse pups were grown on peptide-patterned gold substrates for 7 days. Neurons preferentially adhered to peptide-coated regions of the gold surface and restricted their processes to the peptide patterns. Whole cell recordings of neurons grown in patterned arrays revealed an average membrane potential of -50 mV, as well as the presence of voltage-gated ion conductances. Peptide-modified gold surfaces serve as convenient and effective substrates for growing ordered neural networks that are compatible with existing multi-electrode array recording technology.

Animals↗
PubMed2005

Direct mediatorless electron transport between the monolayer of photosystem II and poly(mercapto-p-benzoquinone) modified gold electrode--new design of biosensor for herbicide detection.

Photosystem II (PSII) modified gold electrodes have been prepared providing mediatorless electron transport on the basis of electrodeposited conductive layer poly-mercapto-p-benzoquinone (polySBQ). Such electrodes are suitable in construction of biosensors for PSII inhibiting herbicides. PolySBQ layer was synthesized on (i) screen-printed gold electrodes and (ii) gold microelctodes in an array on silicon substrate, by electrochemical-oxidation of sulpho-p-benzoquinone (SBQ) at +650 mV versus Ag/AgCl. The basic properties of polySBQ layer were characterized using linear sweep voltammetry and atomic force microscopy (AFM). The typical redox response for quinones was observed. The optimal length of the polymer providing direct electron transfer (DET) was found to be very close to 30 nm. PSII particles isolated from the thermophilic cyanobacteria Synechococcus bigranulatus were physically adsorbed on the polySBQ covered gold electrodes. The generation of photocurrent was observed at E=+250 mV (versus Ag/AgCl) without addition of any mediator. The basic properties of DET were studied. We concluded that: (i) PSII active in DET is immobilized in form of monolayer; (ii) the charge transport from PSII to gold working electrode (AuWE) is fast and dominated by the rate of the enzymatic reaction; (iii) polySBQ layer drains electrons from the Q(A) pocket of the photosystem since the electrode activity is inhibited by specific inhibitor, i.e. diuron (DCMU); (iv) the stability of the photosystem immobilized on gold electrodes by using polySBQ is comparable to the stability of PSII in solution under the same experimental conditions; (v) the inhibition of the photosystem by herbicide DCMU follows the sigmoid dependence; (vi) I(50) as well as limit of detection (LOD) show an improved sensitivity compared to other published biosensing systems using PSII as bioactive part.

Adsorption↗
PubMed2004

Optimizing mechanical properties of laser-welded gold alloy through heat treatment.

OBJECTIVE: The goal of this work was to improve the mechanical strength of laser-welded gold alloy with age-hardenability at intraoral temperature. METHODS: The gold alloy was cast conventionally in plate patterns (0.5 mm x 3.0 mm x 20 mm). After bench-cooling the mold to room temperature (as-cast state), transverse sections of the plate were made at mid-span. They were butted against one another and welded using Nd:YAG laser (current: 320 A; time: 10 ms; spot diameter: 1 mm). Three laser pulses were applied from both sides to cover the joint width (3.0 mm) of the specimens before or after solution heat treatment at 700 degrees C/5 min. Uncut control specimens (non-welded) were also prepared. After solution treatment, two different heat treatments were given the laser-welded specimens: high-temperature aging at 250 degrees C/15 min, or intraoral aging at 37 degrees C/3 days. Control specimens underwent all of the heat treatments after solution treatment. Tensile testing was conducted at a crosshead speed of 2 mm/min and a gauge length of 10 mm. RESULTS: Solution treatment of the gold alloy before laser-welding did not improve the mechanical strength of laser-welded gold alloy after high-temperature aging or intraoral aging. The joint strengths of laser-welded gold alloy were improved only by solution heat treatments after laser-welding and subsequent aging treatment at high or intraoral temperatures. SIGNIFICANCE: The results of this study indicated that laser-welded cast gold alloy prostheses aged at high or intraoral temperatures produce high strength when they are solution-treated after laser-welding.

Dental Soldering↗
PubMed2006

Vacuum metal deposition: visualisation of gold agglomerates using TEM imaging.

Vacuum metal deposition (VMD) is a well-established technique that can be used for the development of latent fingermarks on a range of polymer surfaces, including polyethylene (PE) bags exposed to harsh environmental conditions. The technique has also proved to be effective on difficult semi-porous surfaces such as the polymer banknotes in circulation in Australia and in an increasing number of other countries. VMD is a two-stage technique. In the first stage, a small amount of gold is deposited under high vacuum onto the exhibit. This is then followed by the deposition, onto the gold layer, of a much thicker layer of zinc. Normal VMD development is characterised by zinc depositing all over the surface except on the fingermark ridges themselves. A phenomenon of reverse development (zinc on the ridges but not on the surface) has been reported by many authors. Recent studies indicated that this phenomenon might occur on low-density polyethylene (LDPE) when the amount of deposited gold is above an optimum quantity. The results suggested that the size of the gold agglomerates formed on the surface of the polymer plays a critical role. This preliminary study was aimed at visualising, by transmission electron microscopy (TEM), the formation of gold agglomerates on polymer surfaces to gain an appreciation of how the density and size of these agglomerates changes with an increasing amount of evaporated gold.

Dermatoglyphics↗
PubMed2004

Immobilization of biogenic gold nanoparticles in thermally evaporated fatty acid and amine thin films.

We have recently demonstrated the biological synthesis of gold nanoparticles by the reduction of aqueous chloroaurate ions by the fungus Fusarium oxysporum and with extract of geranium (Pelargonium graveolens) leaf. In this paper, we demonstrate the immobilization of biogenic gold nanoparticles in lipid thin films deposited by thermal evaporation. The charge on the gold nanoparticles synthesized by both the fungus and the geranium plant extract is used to facilitate their immobilization in both anionic and cationic lipid thin films. A rough estimate of the isoelectric point of the proteins capping the gold nanoparticles synthesized using the fungus could be made by pH-dependent microgravimetry studies of the immobilization process. An interesting size and shape selectivity in the immobilized gold nanoparticles is observed in the lipid thin films. The biogenic gold nanoparticle-lipid composite films were characterized using quartz crystal microgravimetry, UV-vis absorption spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and transmission electron microscopy.

Amines↗
PubMed2005

Morphology study of gold-chitosan nanocomposites.

Gold nanoparticles were prepared in the presence of chitosan via reduction of HAuCl4 with sodium borohydride. The gold-chitosan nanocomposite was formed by adsorbing chitosan molecules onto the gold nanoparticle surfaces. The resulting gold nanoparticles were characterized by transmission electron microscopy and UV-vis spectroscopy. Morphology of gold-chitosan nanocomposite films was investigated by polarized optical microscopy. The morphology of chitosan crystal cast from the prepared nanocomposite was much different from that cast from chitosan solution due to the possible nucleation of gold nanoparticles. A branched-like structure or a cross-linked needle-like structure could be formed in nanocomposite films with different casting volumes.

Adsorption↗
PubMed2006

PEG-modified gold nanorods with a stealth character for in vivo applications.

Gold nanorods prepared in hexadecyltrimethylammonium bromide (CTAB) solution are expected to provide novel materials for photothermal therapy and photo-controlled drug delivery systems. Since gold nanorods stabilized with CTAB show strong cytotoxicity, we developed a technique to modify these with polyethyleneglycol (PEG) for medical applications. PEG-modification was achieved by adding mPEG-SH in the CTAB solution, then, excess CTAB was removed by dialysis. PEG-modified gold nanoparticles showed a nearly neutral surface, and had little cytotoxicity in vitro. Following intravenous injection into mice, 54% of injected PEG-modified gold nanoparticles were found in blood at 0.5 h after intravenous injection, whereas most of gold was detected in the liver in the case of original gold nanorods stabilized with CTAB.

Animals↗
PubMed2005

Gold nanoparticles: catalyst for the oxidation of NADH to NAD(+).

Nicotinamide adenine dinucleotide is an important coenzyme involved in the production of ATP, the fuel of energy, in every cell. It alternates between the oxidized form NAD(+) and the reduced form dihydronicotinamide adenine dinucleotide (NADH) and serves as a hydrogen and electron carrier in the cellular respiratory processes. In the present work, the catalytic effect of gold nanoparticles on the oxidization of NADH to NAD(+) was investigated. The addition of gold nanoparticles was found to quench the NADH fluorescence intensities but had no effect on the fluorescence lifetime. This suggested that the fluorescence quenching was not due to coupling with the excited state, but due to changing the ground state of NADH. The intensity of the 340 nm absorption band of NADH was found to decrease while that of the 260 nm band of NAD(+) was found to increase as the concentration of gold nanoparticles increased. This conversion reaction was further supported by nuclear magnetic resonance and mass spectroscopy. The effect of the addition of NADH was found to slightly red shift and increase the intensity of the surface plasmon absorption band of gold nanoparticles at 520 nm. This gives a strong support that the conversion of NADH to NAD(+) is occurring on the surface of the gold nanoparticles, i.e. NADH is surface catalyzed by the gold nanoparticles. The catalytic property of this important reaction might have important future applications in biological and medical fields.

Catalysis↗
PubMed2004

Effects of gold on testicular steroidogenic and gametogenic functions in immature male albino rats.

The present study was undertaken to evaluate the effects of gold chloride, a metallic earth salt, on steroidogenic and gametogenic functions of testis in immature rats. Immature rats of Wistar strain, were injected (s.c.) with gold chloride at the dose of 0.3 mg and 0.5 mg/kg body weight/day for 26 days. All the treated animals along with the vehicle-treated controls were sacrificed 24 hours after last injections. Testicular steroidogenic activity was evaluated by measuring the activities of two steroidogenic key enzymes, Delta5-3beta-hydroxysteroid dehydrogenase (Delta5-3beta-HSD) and 17-beta hydroxysteroid dehydrogenase (17-beta HSD). Gametogenic capacity was determined by counting the number of germ cells at stage VII of seminiferous cycle. Plasma levels of testosterone (T) was measured by radioimmunoassay (RIA). Administration of gold chloride at a dose of 0.3 mg/ kg body weight for 26 days led to insignificant changes of testicular Delta5-3beta-HSD,17beta-HSD activities and gametogenesis along with plasma T. In contrast 0.5 mg gold chloride treatment for 26 days caused a significant increase in plasma T (p < 0.001) along with stimulation of testicular Delta5-3beta-HSD activity (p < 0.001) and 17beta-HSD activity (p < 0.001). Gametogenic activity exhibited a significant increase in the number of step 7 spermatids (7Sd) (p < 0.001) at stage VII of seminiferous cycle when compared to control. The results of our experiment suggest that gold chloride treatment might be associated with significant stimulatory effects on testicular activities. Furthermore, since hormonal changes, altered steroidogenic enzymes and gametogenic activities were evident to a specific dose of gold chloride treatment, our data may have some clinical implication on the stimulation of fertility.

17-Hydroxysteroid Dehydrogenases↗
PubMed1999

Effect of washers on reverse torque displacement of dental implant gold retaining screws.

STATEMENT OF THE PROBLEM: Gold screw loosening is a frequent problem that affects dental implants. PURPOSE: This study determined the effect of spring washers on gold screw displacements during applied removal torque in dental implants. MATERIAL AND METHODS: A 3-unit fixed partial denture was cast in semiprecious alloy and fixed to 2 dental implants with gold-retaining screws. Implants were embedded in acrylic resin and restrained from movement. A miniature load sensor was attached to a torque controller handpiece to accurately measure the time and torque needed to completely loosen the gold screws. Rotational displacements were calculated for 4 experimental setups, involving washers placed on (a) both, (b) the mesial, (c) the distal, and (d) no implants. Screw displacement data were compared between implants in all 4 combinations by means of paired t tests. RESULTS: Gold screws with underlying conical spring washers underwent on average up to 35% (14.1 microm) more rotational displacement during applied removal torque than those without washers. CONCLUSION: Inclusion of a conical spring washer significantly increased the amount of rotational displacement needed to completely loosen an implant gold retaining screw.

Dental Prosthesis, Implant-Supported↗
PubMed2003

Emissions and environmental implications of mercury from artisanal gold mining in North Sulawesi, Indonesia.

In artisanal gold mining practiced in North Sulawesi Island, Indonesia, gold is separated from ore by the use of mercury, which forms an amalgam with gold. All related processes are undertaken with a low level of technical knowledge and skills, no regulation, and with disregard for the safety of human and environment health. The situation is generating serious potential health and environmental risks in the area. As part of an ongoing monitoring program, total mercury concentrations were examined in water, bottom sediment and fish samples from three main rivers in Talawaan Watershed, which receives drainage from gold mining practices. Monitoring began in May-June 2000, almost 2 years after artisanal gold mining had begun. At that time, the mercury concentration in the sediment was generally low, except in places close to the gold processing plants. In the present study, a more systematic sampling and analysis was conducted in May-June 2001. Bottom surface sediments, water, and fish samples were collected at 12 sites along the three main rivers in the watershed. In addition, one site outside the watershed was sampled to serve as a control. Sample collections were conducted in three phases in duplicate, with two-week intervals between each phase. The mercury concentration observed in this study indicated that an increase took place along the three main rivers in the watershed. Solutions to this problem must be formulated as soon as possible in order to avoid a major health, economic, and ecological disaster arising from the continuing discharge of Hg. The present study proposes that mercury dispersion occur downstream of the mining.

Animals↗
PubMed2001

Amperometric detection of DNA hybridization on a gold surface depends on the orientation of oligonucleotide chains.

We tested the possibility of amperometric detection of DNA hybridization on a gold surface influenced by the immobilization of oligonucleotide giving different orientations of single stranded DNA relative to the gold surface. The DNA sensor was fabricated by chemisorption of 18-mer oligonucleotide modified by a phosphorothioate group either at its 3' or both 3' and 5' terminal. After immobilization of oligonucleotide to the gold support, the sensor was immersed in 11-mercaptoundecanoic acid (MUA) solution. Further chemisorption of MUA resulted in approximately 10-fold increase of resistance of the organic layer. Addition of complementary oligonucleotide resulted in an increase of conductivity for DNA sensor oriented perpendicular to the gold support (DNA with one thiol group), while the conductance decreased for DNA sensor with single stranded DNA oriented parallel to the gold support (with DNA modified by thiol groups at both 3' and 5' terminals). Addition of non-complementary chain resulted a slight decrease or no change of sensor conductivity. The hybridization process at both types of DNA orientations is not cooperative and can be described by Langmuir isotherms. The hybridization event on gold support has been confirmed by mass detection using the quartz crystal microbalance technique.

Base Sequence↗
PubMed1998

Genetic control of delayed-type hypersensitivity to gold antigens in mice.

The genetic control of delayed-type hypersensitivity (DTH) to both gold(I) and gold(III) antigens was investigated in various strains of mice. Most mouse strains, with the exception of those with the major histocompatibility complex I-Ab allele, showed a marked DTH response to each antigen; the magnitude of the response to gold(III) was greater than that of the response to gold(I). Moreover, the high responsive trait was dominant. The DTH footpad response was mediated by CD4+ 8-, Ia- T cells. However, CD8+ T cells did not suppress footpad swelling. These results indicate that gold(I) and gold(III) can both stimulate a DTH response in mice.

Adoptive Transfer↗
PubMed2000

Nature of immobilized antibody layers linked to thioctic acid treated gold surfaces.

Utilization of 125I-labeled IgG enables an investigation of protein immobilized to gold electrodes sputter deposited on microporous nylon membranes, including the precise nature of the surface-protein bond (i.e. covalent or non-specific adsorption), physical location of the immobilized protein (i.e. on the surface of the gold electrode or within the pores of the membrane), and the amount of protein immobilized. This is accomplished by comparing the mass of protein immobilized to gold surfaces that have been treated in several different fashions, as well as, deposition of the gold on nylon membranes that have been treated differently. It is shown that these microporous gold electrodes, proposed previously for conducting novel non-separation electrochemical enzyme immunoassays, consist of multiple protein layers non-specifically adsorbed. Approximately, half of the total adsorbed protein is immobilized to the gold surface with the remaining protein bound within the pores on the nylon membrane.

Adsorption↗