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PubMed2006

Quartz crystal microbalance immunosensors for environmental monitoring.

This paper presents discussion of quartz crystal microbalance (QCM) immunosensors for environmental monitoring. Factors limiting the practical application of antibodies to analytical problems are also presented. Among several candidates for the QCM immunosensor device, selected QCM devices and oscillating circuits were tested thoroughly and developed to obtain highly stable and sensitive frequency signals. The biointerface of QCM immunosensor was designed and controlled to immobilize antibody on the QCM surface, to reduce non-specific binding and to suppress denaturation of immobilizing antibody by self-assembled monolayer technique and artificial phospholipid (2-methacryloyloxyethyl phosphorylcholine (MPC)) polymer. MPC polymer as a antibody-stabilizing reagent was added to reduce non-specific binding of the antigen solution and stabilize the immunologic activity of the antibody-immobilized QCM. In addition, it provides examples for detection and quantitation of environmental samples using QCM immunosensors. The analytical results for fly ash extracted samples of dioxins using the QCM immunosensor indicated a good relationship with GC/MS methods. The integrating protocols of the competitive immunoassay and signal-enhancing step are for detecting low molecular analytes with extremely low detection limits using an QCM immunosensor. Furthermore, its detect limitation was extended from 0.1 to 0.01 ng/ml by the signal-enhancing step when the anti-bisphenol-A antibody conjugated MPC polymeric nanoparticles was used. The QCM immunosensor method has demonstrated its effectiveness as an alternative screening method for environmental monitoring because these results were compared with results obtained through environmental monitoring methods such as ELISA and GC/MS.

Biosensing Techniques↗
PubMed2006

Application of peptide probe for evaluating affinity properties of proteins using quartz crystal microbalance.

This study proved a possibility of a peptide probe for evaluating affinity properties of proteins. We have designed and synthesized three different peptide probes, H-Ala3-(Gly-Pro5)3-Gly-OH (peptide A), H-Ala3-(Gly-Pro5)-Gly-OH (peptide B) and H-Ala3-Gly-OH (peptide C) for testing their affinities to profilin. Each peptide probe was immobilized on a quartz crystal microbalance (QCM) sensor. The QCM sensor with the peptide A showed a 93 Hz decrease of resonant frequency which indicated profilin bound to the QCM sensor in a single layer. In a successive reaction with actin, the QCM analysis resulted in a 123 Hz decrease of resonant frequency which showed actin bound to the QCM sensor. A fluorescence microscope image of the sensor surface exhibited clear fluorescence after binding a rhodamine labeled actin on the sensor surface. These results supported stepwise reactions of profilin binding to the peptide A and actin binding to profilin. In the three peptide probes, the peptide A showed the highest affinity to profilin, i.e., sequence dependent affinity was confirmed.

Actins↗
PubMed2004

Transport of anthracene and benz(a)anthracene through iron-quartz and three aquifer materials in laboratory columns.

In groundwater systems, dissolved natural organic matter (NOM) can influence the mobility of organic contaminants by altering the contaminant behavior in water and solid phases. The transport of anthracene and benz(a)anthracene (B(a)A) was studied in the presence and absence of NOM and/or soil organic matter (SOM) in column experiments. The results show that sorption are related to the properties of polycyclic aromatic hydrocarbons (PAHs), NOM and SOM. In the Fe-quartz media, the amount of NOM (20 mg/l) in solution had a little effect on increasing the apparent solubility of anthracene and countering increased anthracene sorption. In the natural (Bemidji) soil, Suwannee river fulvic acid (SRFA, 20 mg/l) and Suwannee river humic acid (SRHA) in water did not compete with SOM for anthracene, indicating that SOM has higher partition efficiency for anthracene. It was also observed that slow diffusion through an organic phase apparently caused most of the observed tailing in column breakthrough curves (BTCs). Even though the fOC of washed Bemidji sediment was very low, the transport of B(a)A was retarded significantly, however, and the transport of B(a)A was shown to be facilitated by dissolved NOM.

Anthracenes↗
PubMed2004

Investigation of the effects of Au-colloid modification on cobalt hexacyanoferrate film growth and mass transport by electrochemical quartz crystal microbalance.

The growth of cobalt hexacyanoferrate (CoHCF) films on bare and Au-colloid-modified electrodes in nitrate or sulfate solutions was monitored by electrochemical quartz crystal microbalance. The average efficiency of CoHCF film growth for Au colloid modified electrodes is 23 and 12 ng cm(-2) s(-1) in KNO3 and K2SO4 solutions, respectively, while those values for the bare gold electrode are 15 and 9 ng cm(-2) s(-1), respectively. In K2SO4 solution, the apparent molar masses for the Au-colloid-modified electrode at lower and higher potential is 58.4 and 37.3 g mol(-1), respectively, which is larger than those for the bare gold electrode (51.7 and 26.3 g mol(-1), respectively). The respective results were also obtained in KNO3 solution. Furthermore, the difference of the apparent molar masses at lower and higher potential for Au-colloid-modified electrodes is smaller than that for bare gold electrodes in the same electrolyte. Additionally, the mechanism of charge propagation is dependent on different anions in electrolyte solutions at higher potentials where the second redox reaction of CoHCF occurs. Therefore, the existence of Au colloids can accelerate CoHCF film growth and weaken the effect of anions on mass transport.

Journal Article↗
PubMed2005

Mass and charge balance in self-assembled multilayer films on gold. Measurements with optical reflectometry and quartz crystal microbalance.

This work aimed to the determination of weight uptakes and charge balance in the course of successive deposition of polyelectrolytes, using the so-called self-assembled multilayer technique. Polyelectrolytes were the quaternized polydimethylaminoethyl methacrylate chloride, (MADQUAT) and poly(acrylic acid) (PAA). Experiments were made at pH 5.5 in NaCl solutions between 10(-3) and 10(-1) M. Deposits (5 bilayers) on a gold substrate were monitored using a quartz crystal microbalance (QCM) and optical fixed-angle reflectometry. Analysis of data lead to the determination of the sensitivity factor of the reflectometric output. QCM allowed the direct measurement of weight uptakes in 10(-3) and 10(-2) M solutions, while the viscoelastic properties of the film did not look appropriate for the measurement in 10(-1) M solutions. The layer-by-layer uptakes and charge balances in 10(-3) and 10(-2) M solutions revealed a large contribution of the counterions in the neutralization of the electrical charge in the film, more so for the highly charged MADQUAT polymer. The difference between two successive polymer charge densities increased significantly with the layer number and the electrolyte concentration. The increase of NaCl concentration induced an increase of MADQUAT but reversely a decrease of PAA deposits. The results were consistent with the determining influence of the salt in polyelectrolyte adsorption, both with regards to the concentration and the type of ions that has been well demonstrated in the literature. This work also draws attention to the role of small ions in the structural and application properties of self-assembled multilayer films.

Journal Article↗
PubMed2006

Improving the quality of the quartz fiber postcore bond using sodium ethoxide etching and combined silane/adhesive coupling.

The influence of different silane/dentin adhesives on the microtensile bond strengths of a hybrid composite to sodium ethoxide-etched quartz fiber posts was investigated. A prehydrolyzed silane was applied without an adhesive and compared to two-component systems in which hydrolysis of the silane occurred after mixing with the acidic monomer present in the dentin adhesives. Nanoleakage along post/core interfaces was examined after silver nitrate tracer penetration using scanning electron microscopy. Higher interfacial strengths and more uniform adaptation between the etched fiber post surface and the composite core were recorded after post treatment with silane/adhesive couplings. The combination of silane with two-step self-etch adhesives improves the chemical retention of composites around etched fiber posts with minimal nanoleakage. Although the one-step self-etching adhesive/silane combination enhances post adhesion, the extensive nanoleakage provides channels for rapid water sorption that may expedite hydrolytic degradation of the post/core interface.

Composite Resins↗
PubMed2006

Detection of Ebola virus envelope using monoclonal and polyclonal antibodies in ELISA, surface plasmon resonance and a quartz crystal microbalance immunosensor.

Ebola virus (EBOV) Zaire, Sudan, as well as Ivory Coast are virulent human EBOV species. Both polyclonal and monoclonal antibodies (MAbs) were developed against soluble EBOV envelope glycoprotein (GP) for the study of EBOV envelope diversity and development of diagnostic reagents. Three EBOV Sudan-Gulu GP peptides, from the N-terminus, mid-GP, and C-terminus regions were used to immunize rabbits for the generation of anti-EBOV polyclonal antibodies. Polyclonal antisera raised against the C-terminus peptide could detect both Sudan-Gulu as well as Zaire GPs, while anti-N and mid-region peptide polyclonal sera recognized only EBOV Sudan-Gulu GP. Of the three anti-EBOV GP mouse MAbs produced, MAb 15H10 recognized all human EBOV GP species tested (Zaire, Sudan and Ivory Coast), and as well as reacted with the Reston non-human primate EBOV GPs. In addition, MAb 15H10 bound virion-associated GP of all known EBOV species. MAb 17A3 recognized GPs of both EBOV Sudan-Gulu and Zaire, while MAb 6D11 recognized only EBOV Sudan-Gulu GP. To detect EBOV GP, these antibody reagents were used in ELISA, surface plasmon resonance and in a quartz crystal microbalance immunosensor. Thus, polyclonal and monoclonal antibodies can be used in combination to identify and differentiate both human and non-human primate EBOV GPs.

Animals↗
PubMed2006

Selective coupling of HE11 and TM01 modes into microfabricated fully metal-coated quartz probes.

We report computational and experimental investigations on injection and transmission of light in microfabricated fully Aluminum-coated quartz probes. In particular, we show that a selective coupling of either the HE(11) or the TM(01) mode can be carried out by injecting focused linearly or radially polarized beams into the probe. Optical fields, emitted by the probe after a controlled injection, are characterized in intensity and phase with the help of an interferometric technique. With the help of near-field measurement, we finally demonstrate that a longitudinally polarized spot localized at the tip apex is actually produced when the TM(01) mode is coupled into the probe.

Journal Article↗
PubMed2006

The determination of electrical parameters of quartz crystal resonators with the consideration of dissipation.

Recently, as the dissipation of quartz crystal through material viscosity is being considered in vibrations of piezoelectric plates, we have the opportunity to obtain electrical parameters from vibration solutions of a crystal plate representing an ideal resonator. Since the solutions are readily available with complex elastic constants from Mindlin plate equations for thickness-shear vibrations, the calculation of resistance and other parameters related to both mechanical deformation and electrical potential is straightforward. We start with the first-order Mindlin plate equations of a piezoelectric plate for the thickness-shear vibration analysis of a simple resonator model. The electrical parameters are derived with emphasis on the resistance that is related to the imaginary part of complex elastic constants, or the viscosity. All the electrical parameters are frequency dependent, enabling the study of the frequency behavior of crystal resonators with a direct formulation. Through the full consideration of complications like partial electrodes and supporting structures, we should be able obtain electrical parameters for practical applications in resonator design.

Journal Article↗
PubMed2001

Adsorption of liposomes and emulsions studied with a quartz crystal microbalance.

The adsorption from phospholipid liposome solutions (1.2%) and phospholipid stabilized oil-in-water emulsions (20% purified soybean oil) with the same phospholipid liposome concentration, has been followed by means of a quartz crystal microbalance allowing the simultaneous determination of changes in resonance frequency and energy dissipation. Both the fundamental resonance frequency and the third overtone were used for following the interfacial processes. The adsorption from the liposome solution resulted in formation of a phospholipid bilayer with an additional and incomplete outer layer of liposomes. The outer layer was removed by dilution leaving a bilayer of phospholipids on the surface. The adsorption process observed from the concentrated emulsion solution was considerably more complex. A slow spreading process that also resulted in some expulsion of material from the interface followed the rapid initial adsorption of emulsion droplets. After rinsing with water a phospholipid bilayer was retained on the surface.

Journal Article↗
PubMed2003

Study of adsorption and viscoelastic properties of proteins with a quartz crystal microbalance by measuring the oscillation amplitude.

The adsorption kinetics of protein A, BSA, IgG, and fibronectin has been investigated using a homemade quartz crystal microbalance. Information about the energy losses appearing in the system is measured by the maximal oscillation amplitude and the dissipation factor. Only the maximal oscillation amplitude allows us to distinguish the different contributions of liquid and mass to the total frequency shift. The adsorption of proteins has been performed on Ti and Au surfaces at different concentrations. The amount of irreversible adsorbed protein A and IgG increases with increasing bulk concentrations. On Au more proteins adsorb, but their biological activity is reduced in comparison to Ti. Protein A forms a first monolayer in a few seconds, which shows practically no energy losses, and following this a second monolayer is formed. The adsorption rate for the second monolayer is much smaller and energy losses are present. Fibronectin is forming a very viscoelastic system, whose mechanical properties are affected by immersion in different buffer solutions.

Adsorption↗
PubMed2003

Piezoelectric quartz crystal impedance and electrochemical impedance study of HSA-diazepam interaction by nanogold-structured sensor.

Human serum albumin (HSA) was immobilized on the surface of colloidal Au and exposed to diazepam. Colloidal Au were at first self-assembled on the gold electrode through the thiol groups of a 1,6-hexanedithiol monolayer. The real-time course of the resonant frequency and equivalent circuit parameters of the sensor during the protein-diazepam binding was determined for the first time by piezoelectric quartz crystal impedance (PQCI). On the basis of the multidimensional information provided by the PQCI analysis, it was concluded that the decrement of the observed frequency was mainly ascribable to the mass loading on the sensor surface. Compared with a bare gold electrode, the gold electrode self-assembled from nanogold colloids exhibits maintained biocompatibility, increased capacity, and more bioactivity. Cyclic voltammetry and electrochemical impedance techniques were used to investigate the immobilization of HSA and the interaction between HSA and diazepam. Results testified that gold colloid could play the role of an efficient electron-conducting tunnel and have a very high ratio of surface to volume. Additionally, the kinetics of the binding process was investigated. The estimated binding constant (K) and the number of binding site (n) on one HSA molecule were 1.66 x 10(6) mol l(-1) and 1.28, respectively.

Journal Article↗
PubMed2003

Determination of coupled solvent mass in quartz crystal microbalance measurements using deuterated solvents.

A simple method is described for determining of the contribution of hydrodynamically coupled solvent to the adsorbed film mass determined in a quartz crystal microbalance (QCM) when operated in liquid. The method requires no additional apparatus and utilizes the change in QCM resonant frequency response between measurements made in non-deuterated and deuterated solvents. The mass of coupled water in a polymer film has been determined and is found to agree with that determined by XPS analysis of the dried polymer film.

Journal Article↗
PubMed2003

The importance of temperature and viscosity effects for surfactant adsorption measurements made using the electrochemical quartz crystal microbalance.

The measurement of adsorbed surfactant is important to fields such as corrosion inhibition, metal cleaning, and separation technologies. The electrochemical quartz crystal microbalance (EQCM) is an important tool that can be used to measure adsorbed surfactant. However, such measurements are subject to significant temperature and viscosity effects that must be appropriately considered. This paper discusses the effect of temperature and viscosity on EQCM measurements in solution environments and the ability of the EQCM to measure surfactant adsorption.

Journal Article↗
PubMed2002

Water sorption isotherms and enthalpies of water sorption by lysozyme using the quartz crystal microbalance/heat conduction calorimeter.

The water sorption isotherm and the water vapor activity dependence of the enthalpy of water sorption Delta(sorp)Hdegrees of lysozyme have been measured at 25 degrees C. A thin film of lysozyme of mass 250 microg was exposed to H2O/N2 mixtures in a quartz crystal microbalance/heat conduction calorimeter (QCM/HCC). The QCM/HCC is a new gravimetric/calorimetric method that measures simultaneously and with high precision the mass change and the corresponding heat flow in a thin film exposed to a gas. Delta(sorp)Hdegrees for lysozyme agrees with previous determinations, although hysteresis effects are evident in the data. No van't Hoff analysis is necessary because sorption enthalpies are measured calorimetrically. The water vapor activity dependence of Delta(sorp)Hdegrees agrees with that measured previously by Bone. As the water content of the lysozyme film drops below 10 mass%, Delta(sorp)Hdegrees becomes more exothermic, indicating that water is being bound to the charged or highly polar groups of the solvent-accessible surface of lysozyme. The dynamics of water uptake and release from lysozyme thin films are much slower than in polymer films of comparable thickness. Because the QCM/HCC operates with sub-milligram samples, any protein is now amenable to study by this technique.

Calorimetry↗
PubMed2001

Investigation of thin films formed from liposome suspensions on quartz substrate.

The stability of thin wetting films formed from 0.15 M NaCl solutions containing small unilamellar dimyristoylphosphatidylcholine (DMPC) vesicles of different concentrations on quartz surface has been investigated by the microinterferometric method. The intensity of monochromatic light reflected from both film surfaces has been recorded as a function of the time of film thinning. Two temperatures were used in the experiments (20 and 35 degrees C). Films containing 10(-3), 5x10(-3) and 10(-2) mg/ml DMPC were unstable and ruptured, while films with 10(-1) and 1 mg/ml DMPC were stable. Film stability was explained on the basis of hydrophobic interactions. Film thickness dependence on time was calculated. The kinetics of film thinning did not obey Reynolds equation and a linearization was observed in co-ordinates ln(h) as a function of time. This phenomenon was explained by a non-homogeneous thinning process, which might be due to the existence of some areas of different structure of the DMPC adsorption layers.

Journal Article↗
PubMed2000

ESR dating of a quartz single crystal from the Menderes Massif in Turkey

Electron spin resonance (ESR) has been employed to date the most recent geological metamorphism by use of a large quartz single crystal extracted from the metamorphic region of Menderes Massif (MM) in Western Turkey. The ESR spectra showed two paramagnetic centers: Al and Ti centers. The former was used for dating, since the latter was already saturated by natural radiation. The age, estimated to be 1.8+/-0.5 Ma, does not agree with the previous age evaluated by isotopic dating techniques suggesting that the thermal or geothermal stressing history of the metamorphic region must have changed the apparent ESR age. A detailed annealing experiment at various temperatures was performed to investigate the influence of thermal annealing in the past and the resulting life time was calculated to be 8.4 x 10(4) a for the Al center, the lifetime for Ti being shorter than that for Al. The lifetime of Al is thus shorter than its ESR measured age. The discrepancy can be explained in terms of the present-day annual dose or 238U, 232Th, and 40K, concentrations being much smaller than the previous annual doses under severe environmental conditions, such as erosive, natural chemical etching and weathering processes.

Journal Article↗
PubMed2000

Retrospective dosimetry: estimation of the dose to quartz using the single-aliquot regenerative-dose protocol.

We report on the application of the single-aliquot regenerative-dose protocol to retrospective dosimetry, using the optically stimulated luminescence (OSL) from quartz extracted from fired bricks. These bricks had previously been exposed to enhanced levels of ionising radiation while part of inhabited structures in the Chernobyl area. The time dependence of the OSL signals is considered first and we conclude that it is most appropriate to use the initial part of the OSL signal for dose estimation, after subtraction of a slowly varying background component. It is then shown that this signal meets the fundamental requirement of the single-aliquot regenerative-dose protocol, in that any change in the luminescence recombination probability can be corrected for by using the OSL response to a fixed test dose. The response of a particular aliquot is examined after three different treatments (untreated, reset by exposure to light and reset by heating to 500 degrees C) and it is shown that, after sensitivity correction, the dose-response curves are indistinguishable up to 10 Gy. The routine application of the protocol is then described and dose estimates are shown to be insensitive to preheat temperature and test-dose size. Finally, dose-depth profiles are presented for two bricks. These profiles demonstrate that the high precisions (approximately 1%) obtained using the regenerative-dose protocol are reflected in smooth dose-depth dependencies.

Construction Materials↗