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ABSTRACT: A method for probing the interaction process between ionic surfactant and protein was developed with series piezoelectric quartz crystal (SPQC) sensing technique. It was based on the sensitive response of the SPQC sensor to the change in solution conductivity. A new relationship between the sensor response and the properties of ionic species in solution was derived. The method was used to examine the interaction process of two surfactants, cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS), with lysozyme in aqueous solution. The obtained experimental results were in agreement with those of other methods from references. These results had been discussed. It was shown that the new method developed here was a useful and promising tool for probing the ionic surfactant-protein interaction process and might find more applications in similar studies.
Journal of Biochemical and Biophysical Methods 07/2002; 52(1):19-29. · 2.33 Impact Factor
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04/2002;
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04/2002;
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ABSTRACT: The effect of magnetic field on the growth of bacteria was studied with the series piezoelectric quartz crystal (SPQC) sensing technique. The growth situations of Escherichia coli (E. coli) in the absence and presence of different intensities of static magnetic fields were examined and analyzed. The results showed that the growth of E. coli was inhibited due to the presence of magnetic fields. By fitting frequency shift (deltaD) versus time curves according to the frequency shift response equation of SPQC, the relationships between three kinetic growth parameters, i.e., the asymptote A, the maximum specific growth rate mu(m) and lag time lambda, and magnetic field intensity were established. Based on these results, a new response model containing the magnetic field intensity was derived as: delta(f) = 167.7 (7.25 - 7.11B)/[1 + exp[4 x 2.46e(-3.97B)/(7.25 -7.1 IB)] x (4.42 + 16.46B - t) + 2]] The kinetic parameters of bacterial growth obtained from this model are close to those obtained from the logistics popular growth model, in which the concentration of the bacteria was determined by the traditional pour plate count method.
The Analyst 04/2002; 127(3):373-7. · 4.23 Impact Factor
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International Journal of Environmental Analytical Chemistry 01/2002; 82(3):113-122. · 1.16 Impact Factor
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ABSTRACT: A new method for the determination of polymer viscosity-average molecular weights was developed with flow piezoelectric quartz crystal (PQC) viscosity sensing. The experimental setup with a 9 MHz AT-cut quartz crystal and a flow detection cell was constructed and shown to be able to give highly reproducible data under the temperature of 25 ± 0.1°C and the fluid flow rate of 1.3–1.6 mL/min. A response model for PQC in contact with dilute polymer solutions (concentration <0.01 g/mL) was proposed in which the frequency change from the pure solvent, Δfs, follows Δfs = −k6ηl1/2 + k7, where ηl is the absolute viscosity of dilute polymer solution and k6 and k7 are the proportionality constants. This model was examined with poly(ethylene glycol) samples (PEG-20000 and PEG-10000) under the aforementioned experimental conditions using water as solvent. The result was Δfs = −1587ηl1/2 + 1443. Based on this model, the method for the determination of polymer viscosity-average molecular weights, Mη, by flow PQC viscosity sensing was described and examined with an unknown poly(vinyl alcohol) (PVAL) sample. The new method proved to be an attractive and promising alternative for the determination of polymer molecular weights based on the good agreement between the molecular weight determined by the new method (Mη = 58600) for the unknown PVAL sample with that determined by the conventional capillary viscosity method. The new method has some advantages over the conventional viscosity method; for examples, operation is simpler and more rapid; the instruments required are cheaper and portable; the needed sample quantity is smaller; and the experimental setup constructed can be used in continuous measurement. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 63–69, 2001
Journal of Applied Polymer Science 10/2001; 82(1):63 - 69. · 1.29 Impact Factor
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ABSTRACT: A new quartz crystal impedance hyaluronidase sensing technique, which is based on the changes in viscosity and density during the enzymatic hydrolysis of chondroitin sulfate (CS) by hyaluronidase (HAse), is established in this paper. The variations of equivalent circuit parameters of the piezoelectric quartz crystal (PQC) during the enzymatic degradation are discussed. The initial hydrolysis rate of CS by HAse is obtained from the changes in viscosity and density with incubation time. Kinetic parameters (the Michaelis constant Km and the maximum hydrolysis rate Vmax) of the degradation process are estimated by using a linear method of Lineweaver-Burk plot. Km is 2.73 ± 0.20 mg·ml−1 and Vmax is -(5.43 ± 0.38) × 10−4 kg·m−2·s−1/2·min−1.
Enzyme and Microbial Technology. 08/2001;
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ABSTRACT: A new quartz crystal impedance sensing technique for the assay of hyaluronidase (HAse) activity is presented. It is based on the changes in viscosity and density during the enzymatic hydrolysis of hyaluronic acid (HA) by HAse. The variations of equivalent circuit parameters of piezoelectric quartz crystal (PQC) during the enzymatic degradation are discussed. The motional resistance shift curves indicate that the viscosity of the test solutions decreases during the hydrolysis process. The initial hydrolysis rates of HA are obtained from changes in viscosity and density as a function of incubation time. Kinetic parameters (the Michaelis constant Km and the maximum hydrolysis rate Vmax) of the degradation reaction are estimated by using a linear Lineweaver–Burk plot in this work. The Km was 0.44±0.03 mg·ml−1 and the Vmax was −(5.29±0.36)×10−3 kg·m−2·s−1/2·min−1.
Talanta 02/2001; · 3.79 Impact Factor
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ABSTRACT: A novel method for monitoring of mutagenic process of dimethyl sulfate to Salmonella typhimurium strain (TA100) was proposed by using piezoelectric quartz crystal impedance (PQCI) analysis technique. The time courses of responses piezoelectric impedance parameters for a quartz crystal in a culture system were simultaneously obtained and discussed. It was found that the motional resistance variation (ΔRm) increases and frequency shift (Δf) of PQC sensor decreases correspondingly during the mutagenic process of the bacteria. These parameters could reflect the variations of viscosity and density of culture system. By fitting ΔRm versus time curves toward Gompertz bacterial growth model, we obtained and discussed the bacterial growth parameters for both normal growth and mutagenic process. The experiments showed that the proposed method could provide real time and multidimensional impedance information to the monitoring of mutagenic process.
Talanta 01/2001; · 3.79 Impact Factor
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ABSTRACT: A method for determination of lysozyme with a Bulk Acoustic Wave (BAW) viscosity sensor is presented. It is based on the
bacteriolytic action of lysozyme on Micrococcus lysodeikeicus (M. lysodeikeicus) and the response of the sensor to the viscosity and density change of this process. There was a good correlation between
the frequency shift and the concentration of lysozyme in the range 10–100 μg/ml. The content of lysozyme in human saliva was
determined by this method and the results obtained were in good agreement with those from the conventional turbidimetric method.
This method has an advantage over the conventional turbidimetric method in that the amount of sample needed is smaller, the
procedure is simpler and the concentration range of the bacterium suspension which can be used in the detection was extended.
Microchimica Acta 10/1999; 132(1):61-65. · 3.03 Impact Factor
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ABSTRACT: By using ion chromatography with series bulk acoustic wave detection, a method for the determination of copper in human blood plasma has been developed. The advantages of the good selectivity of ion chromatography and the highly sensitive response of SBAW have been combined to improve detection limit, accuracy and reproducibility. The detection limit (3) of the method to copper is 0.3 g/ml. The relative standard deviation for the determination of 1.0 g/ml of copper is 2.1% (n=7). For the IC analysis, the analytical column is a Shim-pack IC C1 column, and the mobile phase is 4.0 mM tartaric acid/2.0 mM ethylenediamine solution with pH 4.2. This system has been applied to the determination of Cu in blood plasma from healthy people or patients with renal failure.
Microchimica Acta 01/1999; 130(3):191-195. · 3.03 Impact Factor
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Analytical Letters 01/1998; 31(2):207-219. · 1.02 Impact Factor
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ABSTRACT: Based on the linear relationship between the conductivity of an aqueous solution and the piezoelectric quartz sensor frequency, it was derived that under certain experimental conditions the frequency shift should show a linear dependence on concentration for common acids and aspirin. This verified experimentally. A calibration model for the simultaneous determintaion of aspirin (ASA) and salicylic acid (SA) was established. The usefulness of the technique was evaluated by the analysis of mixtures of known composition using a P-matrix calibration method. The average relative errors were 0.81% for ASA and 1.63% for SA.
Analytica Chimica Acta.
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ABSTRACT: A novel capacitive immunosensor was successfully developed for the direct detection of transferrin based on an ultrathin γ-alumina sol–gel-derived film and gold nanoparticles. The thin film was formed and air-dried by dripping Al2O3 sol with a microliter syringe on a gold electrode modified with a self-assembled mercaptoacetic acid (MAA) monolayer. After defects in the film were blocked with a long-chain alkylthiol, gold nanoparticles were deposited on the surface of the modified film via a potential step from +1.1 to 0.0 V (versus Ag|AgCl|KCl) for 15 s in a 0.5 M H2SO4 solution containing 0.1 mM HAuCl4. Finally, the antibody was immobilized on the gold nanoparticles under the optimized experimental conditions. The capacitive sensor prepared by the present method can provide high sensitivity because of the ultrathin inorganic film with high permittivity and good biocompatibility of gold nanoparticles. Compared with a capacitive immunoassay based on antibody-embedded ultrathin γ-alumina sol–gel-derived films, the novel immunosensor presented a lower detection limit of 0.05 ng/ml and a wider linear response range of 1–75 ng/ml for transferrin detection. The prepared procedure of the novel immunosensor also provided a new approach to fabrication of capacitive immunosensors.
Sensors and Actuators B: Chemical.
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ABSTRACT: Electrochemical methods were applied to study the anodic behavior of gold and its associated elements, e.g., silver, copper, nickel and iron, in alkaline thiourea solution in the absence and presence of Na2SO3. Gold is difficult to dissolve in alkaline thiourea solution because of the passivation of elemental sulfur produced by the irreversible decomposition of thiourea. However, addition of Na2SO3 accelerates the selective dissolution of gold in alkaline thiourea solution. The additive Na2SO3 improves the stability of thiourea in alkaline media, enhances the anodic polarization current of gold greatly, and does not change the passivation states of the associated elements of gold in alkaline thiourea solution. The reaction order of the anodic dissolution of gold in alkaline thiourea solution is 1.65 with respect to Na2SO3, over the Na2SO3 concentration range of 0.01 mol/l to 0.5 mol/l at the potential of 0.34 V vs. NHE. The studies on the kinetics of the dissolution of gold in alkaline thiourea solution show that the Na2SO3 reduces the dissolution potential of gold, and decreases the apparent reaction activation energy of gold dissolution.
Hydrometallurgy 53(3):255-266. · 2.03 Impact Factor
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ABSTRACT: A simple, inexpensive, on-line bulk acoustic wave (BAW) DNA biosensor is proposed. DNA is immobilized onto an Ag-plated surface rather than the conventional Au surface. Thioglycollic (TGC) acid is used as an active coating for DNA immobilization. The immobilization of DNA and the different binding behavior of ds-DNA and ss-DNA are investigated. The result of the enzyme immunoassay also verifies that DNA is successfully immobilized onto the Ag surface. The experimental relationship between Δfs and the amount of added DNA on the TGC acid modified BAW sensor surface is presented. This novel DNA biosensor is used to monitor the whole process of UV-C induced DNA damage in vitro and to get the real-time frequency response curves. Results show that the UV-C damage in aqueous solution exhibits an apparent tendency towards strand breaks.
Analytica Chimica Acta.
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ABSTRACT: A new method utilizing a series piezoelectric quartz crystal (SPQC) sensor was used to monitor the gelation of Tachypleus amebocyte lysate (TAL) and this reaction was applied to determine the Escherichia coliform (E. coli). The technique depended on the change of conductivity and permittivity during the course of gelation. This method was rapid and sensitive. Some factors affecting the determination were discussed. Results showed that the frequency shift was linearly related to the logarithm of E. coli concentration in the range of 2.1×104–2.1×108 cells/ml. The correlation coefficient is 0.993. This SPQC-TAL method was compared with the standard pour plate counts (PPCs). The proposed method for detection of E. coli is much faster and simpler than the traditional methods.
Analytica Chimica Acta.
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ABSTRACT: A new technique termed the “pulse galvanostatic method (PGM)” is described for constructing a glucose sensor by electropolymerization of m-phenylenediamine in the phosphate buffer solution containing m-phenylenediamine and glucose oxidase (GOx). The conditions for fabrication of the poly(m-phenylenediamine) glucose oxidase (PMPD GOx) electrode were optimized as follows: ton/toff, 1; frequency, 10; mean current density, 1 mA cm−2; concentration of the GOx, 5 g l−1. The morphology of PMPD GOx electrode prepared by PGM under the optimized conditions shows porous structure. The PMPD GOx electrode has short response time, high response current, good selectivity and stability. The maximum response current density and Michaelis–Menten constant of the PMPD GOx electrode, based on the calculation of the kinetic parameters, are 231.4 μA cm−2 and 15.33 mM, respectively.
Sensors and Actuators B: Chemical.
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ABSTRACT: In this paper, a hydroxyapatite-modified carbon ionic liquid electrode (HAP-CILE) for the simultaneous determination of lead and cadmium was developed. The hydroxyapatite which combines with ionic liquid plays an important role in remarkable responses of metals. Trace analysis of the selected heavy metals was performed by square-wave anodic stripping voltammetry (SWASV). The oxidation of two metals yielded well-defined, separated square-wave peak currents. The peak currents at about −0.34 V for Pb2+ and −0.88 V for Cd2+ were measured. The affecting factors containing supporting electrolyte, pH of solution, accumulation time, deposition potential, amount of hydroxyapatite and possible interferences were investigated. The sensor exhibited linear behavior in the range of 1 × 10−9 mol L−1 to 1 × 10−7 mol L−1 for lead and cadmium (correlation coefficients: 0.995 and 0.997, respectively) with detection limits of 2 × 10−10 mol L−1 for lead and 5 × 10−10 mol L−1 for cadmium. The results indicate that the sensor is sensitive and effective for the simultaneous determination of lead and cadmium.
Sensors and Actuators B: Chemical.
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ABSTRACT: A novel method was proposed for fabrication of a carbon nanotubes/poly(1,2-diaminobenzene) nanoporous composite based electrode. The poly(1,2-diaminobenzene) was deposited onto the surface of a glassy carbon electrode (GCE) modified with multi-wall carbon nanotubes (MWNTs) via multipulse chronoamperometric electropolymerization (MCE) process. Compared with the composite prepared by conventional electropolymerization (CE), the electronic and ionic transport capacity of the MCE-based composite were significantly improved due to its unique nanoporous structure. The surface of the composite-modified GCE was characterized with scanning electron microscopy (SEM) and cyclic voltammetry (CV). The nanoporous MCE-based electrode was applied to determination of NADH at a much low potential of 70 mV, and a linear range from 2.0 μM to 4.0 mM was observed with fast response (within 5 s) and a lower detection limit of 0.5 μM (based on S/N = 3). In comparison, a narrow linear range from 5.0 μM to 2.0 mM, slower response (up to 15 s) and a higher detection limit of 3.0 μM (based on S/N = 3) was obtained with the electrode prepared by CE. The wider linear range, lower detection limit and fast response of the MCE-based electrode implies that the new method proposed can provide more excellent platforms for sensitive electrochemical sensing and biosensing.
Sensors and Actuators B: Chemical.
