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PubMed2005

Retention of tannic acid and condensed tannin by Fe-oxide-coated quartz sand.

This paper intends to shed light on the interactions between tannin and mineral soil particles. For that purpose, aqueous solution of condensed tannin (CT) (derived from Black pine (Pinus nigra var. maritima)) and commercially available tannic acid (TA) were added to purified quartz (Qtz) sand and quartz sand coated with either goethite (Gt) or ferrihydrite (Fh). After solvent removal by evaporation the samples were extracted by water. The extracts were analysed for organic carbon, total phenolics and CT. The extractability of the two tannins was small and increased in the order Qtz-Fh < Qtz-Gt < Qtz. For all mineral samples, TA was more extractable than CT. Bonding of tannins to the mineral samples and the partial peptisation of the Fe oxide coatings upon the binding resulted in complex tannin release curves. Our results suggest that the inextractability of tannins from natural soils and the absence of tannins in soil leachates might be caused by strong adsorption on soil minerals such as Qtz and Fe (oxy)(hydr)oxides. The results of competition experiments with mixtures of both tannins demonstrate that the CTs, and TA in particular, can release large amounts of Fe (oxides), suggesting that the tannins are excellent metal-mobilising agents. We therefore suggest that the fate of tannins in the mineral soil environment is highly dependent on the abundance of weakly bonded secondary oxides.

Adsorption↗
PubMed2006

Immobilization of liposomes onto quartz crystal microbalance to detect interaction between liposomes and proteins.

To study the interaction between liposomes and proteins, intact liposomes were immobilized on a metal planar support by chemical binding and/or bioaffinity using a quartz crystal microbalance (QCM). A large decrease in the resonance frequency of quartz crystal was observed when the QCM, modified by a self-assembled monolayer (SAM) of carboxythiol, was added to liposome solutions. The stable chemical immobilization of intact liposomes onto SAM was judged according to the degree with which adsorbed mass depended on the prepared size of liposomes, as well as on the activation time of SAMs when amino-coupling was introduced, where the liposome coverage of electrodes was 69+/-8% in optimal conditions. When avidin-biotin binding was used on amino-coupling liposome layers, liposome immobilization finally reached 168% coverage of the electrode surface. Denatured protein was also successfully detected according to the change in the frequency of the liposome-immobilized QCM. The adsorbed mass of denatured carbonic anhydrase from bovine onto immobilized liposomes showed a characteristic peak at a concentration of guanidine hydrochloride that corresponded to a molten globule-like state of the protein, although the mass adsorbed onto deactivated SAM increased monotonously.

Adsorption↗
PubMed2006

Migration of uranium(IV)/(VI) in the presence of humic acids in quartz sand: a laboratory column study.

The migration behavior of U(IV) and U(VI) in the presence of humic acid was studied in a quartz sand system. Laboratory column experiments were performed using humic acid, U(VI) in humic acid absence, U(IV) and U(VI) in humic acid presence, and for comparison a conservative tracer. In experiments using humic acid, both redox species of U migrate nearly as fast as the conservative tracer. Humic acid accelerates the U(VI) breakthrough compared to the humic acid-free system. There are strong indications for a similar effect on the U(IV) transport. At the same time, a part of U(IV) and U(VI) associated with the humic acid is immobilized in the quartz sand due to humic colloid filtration thus producing a delaying effect. Tailing at a low concentration level was observed upon tracer elution. The experimental breakthrough curves were described by reactive transport modeling using equations for equilibrium and kinetic reactions. The present study demonstrates that humic acids can play an important role in the migration of actinides. As natural organic matter is ubiquitous in aquifer systems, the humic colloid-borne transport of actinides is of high relevance in performance assessment.

Chromatography↗
PubMed2006

Amplification of the antigen-antibody interaction from quartz crystal microbalance immunosensors via back-filling immobilization of nanogold on biorecognition surface.

A new quartz crystal microbalance immunoassay method based on a novel transparent immunoaffinity reactor was developed for clinical immunoassay. To construct such an affinity reactor, resonators with a frequency of 10 MHz were fabricated by affinity binding of functionalized gold nanoparticles (nanogold) to quartz crystal with immobilized specific ligand for the label-free analysis of the affinity reaction between a ligand and its receptor. [Recombinant human tumor markers, carcinoembryonic antigen (CEA) was chosen as a model ligand.] The binding of target molecules onto the immobilized antibodies decreased the sensor's resonant frequency, and the frequency shift was proportional to the CEA concentration in the range of 3.0-50 ng/ml with a detection limit of 1.5 ng/ml at a signal/noise ration of 3. A glycine-HCl solution (pH 2.3) was used to release antigen-antibody complexes from the biorecognition surface. Good reusability was exhibited. Moreover, spiking various levels of CEA into normal human sera was diagnosed using the proposed immunoassay. Analytical results show the precision of the developed immunoassay is acceptable, implying a promising alternative approach for detecting CEA in clinical immunoassay. Compared with the conventional enzyme-linked immunosorbent assay, the proposed immunoassay system was simple and rapid without multiple labeling and separation steps. Importantly, the proposed immunoassay system could be further developed for the immobilization of other antigens or biocompounds.

Antibodies↗
PubMed2001

A comparison of international silica (alpha-quartz) calibration standards by Fourier transform-infrared spectrophotometry.

Seven international silica (alpha-quartz) standards were examined for relative purity to the US National Institute of Standards and Technology (NIST) Standard Reference Material (SRM) 1878 Respirable alpha-quartz by Fourier Transform-Infrared Spectrophotometry (FT-IR). The standards examined have been used in North America, the UK, Australia and Germany. The 189 samples analyzed included NIST-SRM 1878, Min-U-Sil 5, Ottawa Silica Sand, Sikron F-600, A9950 (AUST 1), DQ12-Robock, DQ12-Bergbau. Size distributions of the standards were determined by Coulter Counter to be broadly similar with equivalent spherical volume median diameter ranging between 1.2 and 3 microm. The results showed the standards to differ by as much as 30% in relative purity. Consequently, an internationally agreed upon calibration standard is urgently needed. Min-U-Sil 5 based NIST-SRM 1878 or Sikron F-600 are the two most likely candidates. Any agreed standard must have a well characterized size distribution and closely match the respirable dust criteria. It should also be studied by both infrared spectrophotometry and X-ray diffraction techniques.

Calibration↗
PubMed1998

Surface chemistry and quartz hazard.

The variability of quartz hazard is related to the characteristics of particulate toxicants. Although these have the same chemical composition, they exist in various forms and surface states, each one eliciting different biological responses. On the basis of data from the literature, surface chemical properties are associated to the subsequent stages reported by Donaldson and Borm (1998) in the mechanistic model proposed for quartz carcinogenicity. Surface radicals and iron-derived reactive oxygen species (ROS) are implicated in oxidative stress, considered to be the key event in the development of fibrosis and lung cancer. Other chemical functionalities related to cytotoxicity, however, modulate the overall pathogenicity by regulating transport and clearance. The chemical features deriving from the intrinsic characteristics of a silica dust--e.g. its origin--as well as those generated by external factors--e.g. contaminants, associated minerals--are discussed in relation to their possible role in the pathogenic mechanism.

Fibrosis↗
PubMed2000

Induction of superoxide in glioma cell line U87 stimulated with lipopolysaccharide and interferon-gamma: ESR using a new flow-type quartz cell.

The production of superoxide and nitric oxide induced in U87 glioma treated with lipopolysaccharide (LPS) and interferon-gamma (IFN-gamma) was examined by electron spin resonance (ESR) spectroscopy using a newly designed flow-type quartz cuvette without detaching cells from the culture plate. ESR spectra of 2,2,6, 6-tetramethyl-4-hydroxy-1-piperidinyloxy (TEMPOL) with U87 cells on a quartz culture plate were measured at 15 min intervals. The signal intensity of TEMPOL decreased in the presence of U87 cells at the pseudo-first order rate. The signal decay was accelerated in the U87 cells treated with LPS/IFN-gamma for 24 h, and was suppressed in the presence of superoxide dismutase and catalase. By the spin-trapping method, nitric oxide from U87 cells pretreated with LPS/IFN-gamma for 24 h was measured by the ESR, but only a weak signal of nitric oxide adducts was detected. Further, the nitrite and nitrate levels in the medium did not increase for 24 h. By the ESR measurement of cells on culture plates without detachment stress, it was found that the production of superoxide was induced by LPS/IFN-gamma, but that of nitric oxide was not, in U87 glioma cells.

Catalase↗
PubMed2003

Sorption of tributyltin onto a natural quartz sand.

The aim of this study is to understand the sorption of tributyltin (TBT) onto natural quartz sand by classical batch experiments and spectroscopic surface analyses. At pH<6, the major species of TBT is the cation TBT(+). Due to the presence of both the cationic part and the butyl chains, TBT should present amphiphilic properties. For concentrations lower than 40 microM, TBT sorption occurs as a homovalent 1:1 cation exchange between either H(+) or Na(+) and TBT(+). The increasing affinity of TBT with respect to the different materials follows the series kaolinite<<natural sand<treated sand<pure quartz. From XPS analyses, where the chemical environment of Sn did not change, indicating possible complete reversibility of the TBT sorption, it seems that inner-sphere surface complexes could be formed due to the increase in the 3d-level binding energy. At TBT concentrations higher than 100 microM, we showed by flotation experiments and XPS analysis that the surface becomes hydrophobic. After one monolayer was formed, the TBT sorption could thus be due to hydrophobic interaction between the butyl chains of the sorbed TBT and those of the TBT still available from the bulk solution. This mechanism is consistent with surface condensation and the shape of the sorption isotherm.

Absorption↗
PubMed2001

Quartz strip resonators as a temperature sensor.

The miniature frequency-temperature sensor in the form of a small quartz strip vibrating in the thickness-shear mode with the resonant frequency in the range from 4 to 8 MHz is considered. Y-cut strips rotated in the range from 0 degrees to 27 degrees are the subject of the study. The temperature coefficients of the resonance frequency for the different rotation angles are given. The different temperature dependence of the resonant frequency of the quartz temperature sensors vibrating on the fundamental and harmonic frequency of the thickness-shear modes is pointed out.

Quartz↗
PubMed2002

The effect of irradiation wavelength bandwidth and spot size on the scraping depth and temperature rise in composite exposed to an argon laser or a conventional quartz-tungsten-halogen source.

OBJECTIVES: The purpose of this study was to investigate the effect of the spectral distribution of the curing irradiation near the maximum excitation wavelength of the photo-initiator and the effect of the irradiation spot size on the scraping depth-of-cure and temperature rise in a resin composite for both an argon laser and a quartz-tungsten-halogen lamp. METHODS: Using bandpass filters, the spectral outputs of an argon laser and a quartz-tungsten-halogen lamp were restricted to pass selected wavelengths on to a commercial camphorquinone-based resin composite and the depth-of-cure, using scraping methods, was measured. The temperature rise in composite was measured for some of the above-mentioned sources. The spot sizes for both sources were varied and the scraping depth was measured. Lateral curing or the extent of curing away from the focused spot was also measured. RESULTS: For constant power density and exposure time, an irradiation spectral distribution closer to the photo-initiator excitation peak yielded a higher scraping depth than a broadband spectral distribution for both sources. Under similar conditions, the argon laser resulted in a lower temperature rise in the composite than the lamp. For the same total energy imparted to the resin composite, the scraping depth increased with reducing spot size of the curing irradiation. Furthermore lateral curing of the composite well beyond the irradiation spot size was observed. SIGNIFICANCE: The spectral and spatial characteristics of the curing irradiation need to be carefully considered as these affect the scraping depth-of-cure and temperature rise in a resin composite.

Argon↗
PubMed2002

Detection of two orchid viruses using quartz crystal microbalance (QCM) immunosensors.

Quartz crystal microbalance (QCM) immunosensors are based on the principle that adsorption of substances on the surface of a quartz crystal changes its resonance oscillation frequency. A QCM immunosensor was developed for the detection of both cymbidium mosaic potexvirus (CymMV) and odontoglossum ringspot tobamovirus (ORSV) by pre-coating the QCMs with virus-specific antibodies. Upon binding of virions in either purified form or crude sap of infected orchids with the immobilised virus antibodies, the increase in mass at the QCM surface resulted in a reduction in the frequency of resonance oscillation in a manner dependent upon the amount of virus bound. The QCM was able to detect as low as 1 ng each of the two orchid viruses. This detection sensitivity is comparable to enzyme linked immunosorbent assay (ELISA) but the assay is faster. This immunoassay was shown to be specific, sensitive, rapid and economical, thus providing a viable alternative to virus detection methods. This is the first report using QCM immunosensors to detect plant viruses.

Antibodies, Viral↗
PubMed1999

Application of the quartz crystal microbalance to the monitoring of Staphylococcus epidermidis antigen-antibody agglutination.

The change in solution properties due to the agglutination of an antigen with its specific antibody has previously been used as a marker of infection. This method has been modified to allow the binding activity between species to be followed using the frequency response of a quartz crystal microbalance (QCM). The Bayston agglutination plate assay for Staphylococcus epidermidis has been modified to allow the electrode of a QCM to act as a direct sensor for the change in solution properties as agglutination occurs. Antibody and antigen were introduced to the crystal surface and the agglutination process was followed as a change in crystal resonant frequency. Serum, known to be infected with the organism, gave a titre of 3.9x10(-2)% v/v (-118 Hz, +/-12 SD, N = 9) matching that given by triplicate plate assay. Uninfected serum gave no frequency changes at this concentration, yielding a titre of 2.5x10(-2)% v/v again matching the plate titre (N = 3). Infected serum gave responses 40 times faster then those of the uninfected serum. The piezoelectric quartz crystal method gave a positive or negative diagnosis in <15 min compared with the 24 h required for the plate assay.

Agglutination Tests↗
PubMed2000

Piezoelectric quartz crystal based label-free analysis for allergy disease.

This work presents a piezoelectric (Pz) quartz crystal based label-free quantification of total IgE and allergen-specific IgE in human sera for allergy testing. An evaluation of the different brands of crystals was first initiated with respect to variability in mass sensitivity, frequency measurement reliability and stability, and surface roughness. Thereafter, for total IgE quantification. a direct assay format was adopted. By means of thioctic acid (TA) and coupling reagents, anti-human IgE antibodies were immobilized on AT-cut Pz crystals (10 MHz). The modified crystals could detect serum IgE directly corresponding to a downward frequency shift. The results showed that silver-coated crystals as compared with their gold-coated counterparts provided approximately 1.5 times higher mass detection sensitivity for total IgE in the range of 5-300 IU/ml with a linear regression line, y = 1.8957 x + 1.5603, R2 = 0.995. For the detection of allergen-specific IgE, a sandwiched assay format was used. As the allergen-modified sensor surface captured various classes of associated antibodies (IgE, IgG, etc) and interfering serum proteins as well, the initial frequency shift downwards caused by sera sample incubation would not be proportional to specific IgE levels. Thus, following sample incubation, a second incubation step with secondary anti-human IgE was added to recognize IgE from other bound substances. The frequency shift after secondary antibody binding reflected the amount of allergen-specific IgE proportionally. Compared with 10 MHz crystals, the 20 MHz counterparts provided approximately four times higher mass detection sensitivity for allergen specific IgE in the range of 0.15-17.5 IU/ml with a linear regression line, y = 50.525 x + 107.777, R2 = 0.954. Total IgE and allergen specific IgE assay results of real patients' sera using the Pz sensors agreed well with those obtained by commercially available test kits with correlation coefficient 0.96-0.98. The possibility of regenerating the quartz crystals for further re-use was also dealt with.

Allergens↗
PubMed2002

Glow-discharge treated piezoelectric quartz crystals as immunosensors for HSA detection.

The aim of this study is to develop an immunoaffinity sensor based on piezoelectric crystals for human serum albumin (HSA) detection in aqueous media. Quartz crystals were treated with ethylene diamine (EDA) plasma in a glow-discharge apparatus in order to substitute amino groups on their surfaces. Then anti-HSA antibodies were immobilized via these amino groups by using glutaraldehyde (GA) as cross-linker. Immobilization of the antibody on the quartz crystal was examined for different pH, antibody concentration and treatment time. The optimum conditions for anti-HSA immobilization were evaluated by the measurements of the activity of the surface against HSA. The optimum values of pH, antibody concentration and treatment time were found 6.2, 0.15 mg/ml and 2 h, respectively. For detection of HSA into the solution, two methods were used. In the first (dip and dry) method, the frequency shifts were measured in air after the 1 h interaction of the anti-HSA immobilized crystals with HSA solution. In the other (direct) method, the frequency shifts were followed continuously for 60 min. while the probe was immersed in the HSA solution. An increase for the frequency shifts was observed with increasing of HSA concentration of 16-128 microg/ml. Both the immobilization and antibody-interaction conditions were found important on the extend of these specific interaction. The relations between the HSA concentrations and frequency shifts were exponential in both methods.

Adsorption↗
PubMed2004

A novel piezoelectric quartz micro-array immunosensor based on self-assembled monolayer for determination of human chorionic gonadotropin.

A novel multi-channel 2 x 5 model of piezoelectric quartz micro-array immunosensor has been developed for quantitative detection of human chorionic gonadotropin (hCG) in serum or urine samples. Every crystal unit of the fabricated piezoelectric hCG micro-array immunosensor can oscillate independently without interfering each other. A 2 x 5 model of micro-array immunosensor as compared with a one-channel immunosensor can provide eight times higher detection speeds for hCG assay. The anti-hCG antibody is deposited on the gold electrode's surface of 10 MHz quartz AT-cut crystal by self-assembled technique using sulfosuccinimidyl 6-[3'-(2-pyridyldithio) propionamido] hexanoate (Sulfo-LC-SPDP), and serves as an antibody recognizing layer. The highly ordered self-assembled monolayers (SAM) ensure well-controlled surface structure and offer many advantages to the performance of the sensor. Compared with conventional antibody immobilization methods, the amount and the reaction activity of antibody monolayer coated by the SAM binding are bigger than those by the SPA method, and less non-specific binding caused by other analytes in sample is found. Under the optimized experimental conditions, the results showed that micro-array immunosensor quantitatively detected serum or urine hCG in the range of 2.5-500 mIU/ml with high precision (CV<5%); other hormones in human serum and urine did not interfere with the determination markedly. Serum and urine samples of 60 patients were detected by the micro-array immunosensor, and the results agreed well with those given by the commercial radioimmunoassay test kit, with correlation coefficient of 0.92. After regeneration with urea solution the coated immunosensor can be reused five times without appreciable loss of activity.

Biosensing Techniques↗
PubMed1998

Thiolated Salmonella antibody immobilization onto the gold surface of piezoelectric quartz crystal.

An improved antibody-coated sensor system based on quartz crystal microbalance analysis on Salmonella spp. was developed making use of thiolated antibody immobilization onto one gold electrode of the piezoelectric quartz crystal surface. The best results in sensitivity and stability were obtained with the thin layer of a thiol-cleavable, heterobifunctional cross-linker, sulfosuccinimidyl 6-[3-(2-pyridyldithio)propionamido]hexanoate (sulfo-LC-SPDP). The long bridge of this reagent could function as a spacer, facilitating antibody-Salmonella interaction on the gold electrode. After the addition of a S. typhimurium suspension into a reaction cell with 0.1 M sodium phosphate buffer, pH 7.2, the resonant frequency decreased conspicuously. The time required for maximum frequency shift was about 30-90 min. Sensor response was observed for the microbial suspensions ranging from 9.9 x 10(5) to 1.8 x 10(8) CFU/ml.

Antibodies, Bacterial↗
PubMed1999

Quartz crystal microbalance (QCM) as a device for the screening of phage libraries.

An immunosensing system based on a quartz crystal microbalance (QCM) is presented for the selection of both antigen specific recombinant antibodies and antigen specific human pancreatic secretory trypsin inhibitor (hPSTI) mutants isolated from large phage libraries. The QCM was integrated into a flow injection analysis system for the straightforward analysis of large sample numbers. Measurements were performed using a biotinylated antigen immobilized by streptavidin onto the gold surface of the quartz crystal and phages displaying recombinant antibodies or hPSTI mutants. The results obtained by the QCM were in accordance to those of a well established enzyme linked immunosorbent assay (ELISA). Therefore, the QCM is well suited for the detection of single high affinity clones isolated from large phage display libraries.

Bacteriophages↗
PubMed1994

Investigation of specific binding of antifluorescyl antibody and Fab to fluorescein lipids in Langmuir-Blodgett deposited films using quartz crystal microbalance methodology.

Antifluorescyl IgG antibody and Fab binding to two fluorescein-conjugated lipids was measured using the quartz crystal microbalance methodology. By use of the Langmuir-Blodgett technique, the fluorescein lipids, which were diluted to 5% in a L-alpha-dipalmitoyl phosphatidylethanolamine (DPPE) matrix, were deposited directly onto one gold electrode of the quartz crystal. Binding to films containing the fluorescein hapten was significantly enhanced compared to films of the pure DPPE matrix lipid, indicating that binding occurred primarily through a specific interaction. Association constants were 40-300 times less than for binding to haptens free in solution. Binding of IgG to the lipid in which the hydrocarbon chains and the fluorescein hapten were linked via a hydrophilic spacer was approximately 7 times as great as to the lipid containing no spacer. IgG binding to the lipid containing the spacer was increased 1.5-4.4 times compared to Fab binding for the same lipid. Equilibrium binding curves and kinetic measurements are analyzed quantitatively and compared.

Animals↗