Piezoelectric Quartz Crystal Impedance Analysis Research Articles

Binding Studies of L-Tryptophan to Human Serum Albumin with Nanogold-Structured Sensor by Piezoelectric Quartz Crystal Impedance Analysis

Nanogold-modified sensor was constructed and applied to study the binding of L-tryptophan to human serum albumin (HSA) in situ by piezoelectric quartz crystal impedance (PQCI) analysis. It was interesting that the as-prepared nanogold modified sensor was more sensitive and biocompatible than bare gold electrode. The frequency changes due to protein adsorption on the nanogold-modified sensor might be described as a sum of two exponential functions and detailed explanation was given. Additionally, the kinetics of the binding process was also investigated. The binding constant (K) and the number of binding site (n) for the binding process without competitor are fitted to be 1.07 x 10(4) (mol l(-1))(-1) s(-1) and 1.13, respectively, and 2.24 x 10(3) (mol l-(1))(-1) s(-1) and 1.18, respectively for the binding process with competitor.

Study on Degradation Characteristics of Chitosan by Pepsin with Piezoelectric Quartz Crystal Impedance Analysis Technique

Piezoelectric quartz crystal impedance analysis technique was applied to study the chitosanolytic activity of pepsin. The method is based on the viscosity-density reduction of chitosan solution during the enzymatic degradation process. Experiments examined the time courses of the variations of motional resistance (deltaR1) for a quartz crystal. By comparing the deltaR1 response curves under different degradation conditions, the effects of pH, temperature, enzyme and substrate concentration on the chitosanolytic activity of pepsin was investigated in detail. The results suggest that the optimum pH and temperature were 4.6 and 55 degrees C, respectively. Increasing aptly the enzyme or substrate concentration was in favor of the degradation of chitosan. Moreover, the influence of the degree of deacetylation (DD) on the enzymatic degradation was studied. The result indicates that chitosan with a lower DD was easier to be degrade compared with chitosan with a higher DD. Also, it was found that there was a good linear relationship between the deltaR1 response and the DD value. The regression equation was deltaR1 = 0.058 x DD-6.795 and the correlation coefficient was 0.987.

Study on the interaction between DNA and protein induced by anticancer drug carboplatin

The interaction of DNA and human serum albumin (HSA) in the presence of anticancer drug carboplatin was studied with piezoelectric quartz crystal impedance (PQCI) and electrochemistry techniques. In the PQCI analysis, the correlative parameters including the frequency ( f 0), the motional resistance ( R m), and the static capacitance ( C 0) in the experiment were obtained and discussed in detail. Additionally, the kinetics parameters of the cross-linking process were investigated and a response kinetics model was deduced. The values of association rate constant k 1, dissociation rate constant k −1 and the reaction equilibrium constant K were estimated to be 1.895 (mg/ml) −1 s −1, 4.7 × 10 −5 s −1 and 4.03 × 10 4 (mg/ml) −1, respectively. Furthermore, cyclic voltammetry (CV) and electrochemical AC impedance techniques were employed to testify the cross-linking process.

Scanning Electrochemical Microscopy in Combination with Piezoelectric Quartz Crystal Impedance Analysis for Studying the Growth and Electrochemistry as Well as Microetching of Poly(o-phenylenediamine) Thin Films

The combination of scanning electrochemical microscopy (SECM) with piezoelectric quartz crystal impedance (PQCI) analysis was proposed as a novel multiparameter method for investigating the cyclic voltammetric growth of poly(o-phenylenediamine) (PoPD) thin films at Au electrodes in aqueous solutions of various pH values and the potentiostatic microetching (localized degradation) of these films in 0.10 mol/L aqueous H2SO4 for comparative examinations on polymer porosity and stability. Two potential-sweep ranges, -0.4 to 0.9 (I) and 0 to 0.9 (II) V versus SCE, and four solutions, acidic (A, 0.20 mol/L H2SO4 + 0.10 mol/L Na2SO4; B, 0.10 mol/L H2SO4 + 0.20 mol/L Na2SO4), neutral (C, 0.10 mol/L PBS + 0.20 mol/L Na2SO4, pH 7.2), and alkaline (D, 0.20 mol/L NaOH + 0.20 mol/L Na2SO4) aqueous solutions, were selected for PoPD growth. The pH increase for the polymerization solution increased the molar percentage of polyaniline-like chains in PoPD, as quantified from the current peaks at approximately 0.6 V versus a saturated calomel electrode (SCE) for the oxidation of -NH2 groups in as-prepared PoPD (grown from solutions C and D) during their redox switching in 0.10 mol/L aqueous H2SO4 for the first time. The unusual PQCI responses observed at negative potentials (potential range I) in the first several potential cycles during the cyclic voltammetric growth of PoPD in acidic and neutral solutions have been reasonably explained as being due to the precipitation/dissolution of the poorly soluble phenazinehydrine charge-transfer complexes developed during redox switching of oligomers for the first time, which brought about much less compact PoPD films and their higher degradability than those grown in the same solution but over potential range II. SECM, scanning electron microscopy (SEM), and piezoelectric quartz crystal (PQC) frequency were used to estimate the sizes of etched microscale spots. In addition, the x-, y-, or z-axis movement of a Pt microelectrode of 25-mum diameter near the PQC electrode was found to influence negligibly the PQCI responses in 1.0 mol/L aqueous Na2SO4 containing K4Fe(CN)6 up to 0.10 mol/L, and a new protocol of dynamically electrodepositing silver microwires via the chemical-lens method was proposed for examining the local mass-sensitivity distribution on the PQC surface.

Investigation of double stranded DNA damage induced by quercetin–copper(II) using piezoelectric quartz crystal impedance technique and potentiometric stripping analysis

DNA damage by quercetin–Cu 2+ was monitored in real time by piezoelectric quartz crystal impedance (PQCI) technique. In the PQCI analysis, the frequency change was caused mainly by the changes in density–viscosity of DNA solution in the damage course. The influences of DNA, Cu 2+, and quercetin concentrations on the motional resistance change (Δ R m) were investigated in detail. The results showed that quercetin exhibited pro-oxidative damage at lower concentrations while anti-oxidative protection at higher concentrations, and Δ R m exhibited a linear relationship in the DNA concentration range from 200 to 1600 μg/ml. Potentiometric stripping analysis (PSA) was also used to observe the electrochemical behavior of damaged DNA. From PSA, a new peak at 0.84 V and a higher peak at 1.06 V were discovered, which suggested that more purines were exposed to the electrode surface during the damage course. In agarose-gel electrophoresis, catalase and biquinoline were found to effectively inhibit DNA damage, therefore, a possible damage mechanism was proposed.

Real-time investigation of the interaction between primaquine phosphate and bovine serum albumin (BSA) by piezoelectric quartz crystal impedance analysis

Real-time investigation of the interaction between primaquine phosphate and bovine serum albumin by the piezoelectric quartz crystal impedance (PQCI) analysis was carried out for the first time. Three kinds of electrodes were investigated. Compared with bare gold (Au) electrode, the gold electrode self-assembled of nanogold colloids exhibits maintained biocompatibility, increased capacity and more bioactivity. Additionally, on the basis of the multi-dimensional information provided by the PQCI analysis, the real-time interaction information and the kinetics of the binding process was investigated and a response model was deduced. At 37 °C, the binding rate ( k 1), dissociation rate ( k −1) and equilibrium constants ( K a) were 4.19×10 2 (mol l −1) −1 s −1, 1.01×10 −3 s −1 and 4.15×10 5 (mol l −1) −1 for the electrode modified by nanogold particles; 3.83×10 2 (mol l −1) −1 s −1, 9.70×10 −4 s −1 and 3.95×10 5 (mol l −1) −1 for the bare gold electrode, respectively.

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 1.66×10 6 mol l −1 and 1.28, respectively.

Real-Time Monitoring of Activated Bleomycin-Induced Cleavage of DNA with Piezoelectric Quartz Crystal Impedance Analysis

A novel process analysis method, with a piezoelectric quartz crystal impedance technique based on the mass effect, for real-time monitoring the activated Bleomycin-induced cleavage of DNA process was proposed. The DNA-coated piezoelectric sensor was in contact with Bleomycin solution at the existence of H2O2 and Fe3+. The optimized experimental condition was determined through the experiments about the effect of pH and ionic strength. The experimental results indicated that activity of Bleomycin is maximal when pH = 8.0 and the ionic strength is low. Under the chosen experimental condition, Bleomycin concentration, which was in the range of 40–250 µg mL−1, had an effect on the interaction, while Fe3+ concentration did not. And then the results about other antibiotics, Cefradine, Streptomycin, Benzylpenicillin, Doxycycline, Acetylspiramycin, showed that these antibiotics did not show the same behavior like Bleomycin.

Corrigendum to “Monitoring of mutagenic process with piezoelectric quartz crystal impedance analysis”: [Talanta 53 (2000) 525–533

Corrigendum to “Monitoring of mutagenic process with piezoelectric quartz crystal impedance analysis”: [Talanta 53 (2000) 525–533

Real-time monitoring of formaldehyde-induced DNA-lysozyme cross-linking with piezoelectric quartz crystal impedance analysis.

A novel method for monitoring, in real time, the formaldehyde (FA)-induced DNA-protein cross-linking process with the piezoelectric quartz crystal impedance (PQCI) technique is proposed. The method was used to monitor FA-induced DNA-lysozyme cross-link formation. Lysozyme was directly immobilized on the silver electrode surface of a piezoelectric quartz crystal by adsorption. The lysozyme-coated piezoelectric sensor was in contact with FA and DNA solutions. The time courses of the resonant frequency and equivalent circuit parameters of the sensor during the cross-linking were simultaneously obtained and are discussed in detail. On the basis of the feature of the multi-dimensional information provided by the PQCI technique, it was concluded that the observed frequency decrease could be mainly ascribed to the mass increase resulting from the cross-linking. According to the frequency decrease with time, the kinetics of the cross-linking process were quantitatively studied. A piezoelectric response model for the cross-linking was theoretically derived. Fitting the experimental data to the model, the kinetic parameters, such as the binding and dissociation rate constants (k(1) and k(-1)) and the cross-linking equilibrium constant (Ka), were determined. At 37 degrees C, the k(1), k(-1) and Ka values obtained were 7.0 (+/-0.1) x 10(-5) (microg ml(-1))(-1) s(-1), 6.6 (+/-0.1) x 10(-3) s(-1) and 1.06 (+/-0.02) x 10(-2) (microg ml(-1))(-1), respectively.

Monitoring of mutagenic process with piezoelectric quartz crystal impedance analysis

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 (Δ R m) increases and frequency shift (Δ f) 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 Δ R m 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.