Jinzhong Zhang

Development of a thickness shear mode acoustic sensor based on an electrosynthesized molecularly imprinted polymer using an underivatized amino acid as the template

The preparation and characterization of electrosynthesized poly(o-phenylenediamine) (iPoPD) as a molecular imprinting material were studied by an in situ quartz crystal impedance method. The changes of delta f0, delta R1, delta L1 and delta C0 suggest that the polymer film was compact and rigid. The thickness shear mode (TSM) acoustic sensor modified with this material exhibits molecular recognition ability to the template molecule of DL-phenylalanine. In the range 2-20 mM, a linear relationship between the frequency shift delta f0 and logC was found from the calibration graph. Scatchard analysis of the relevant calibration graph offers information on the equilibrium of the binding interaction and the recognition sites. Using this electropolymerization technology, the preparation of the sensor was very simple and the reproducibility of preparation was very good. In particular, it offers possibilities for sensor miniaturization.

Effect of static magnetic field on growth of Escherichia coli and relative response model of series piezoelectric quartz crystal

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.

Monitoring for adsorption of human serum albumin and bovine serum albumin onto bare and polystyrene-modified silver electrodes by quartz crystal impedance analysis

The adsorption of human serum albumin (HSA) and bovine serum albumin (BSA) from PBS (pH 7.4) onto bare and polystyrene (PS)-modified silver electrodes was in situ monitored using quartz crystal impedance analysis. The adsorption characteristics of HSA and BSA were discussed by analyzing piezoelectric parameter simultaneous responses. Experimental results indicated that for both HSA and BSA, the amount adsorbed on bare silver was more than that on PS-modified surface. The BSA amount adsorbed on the two surfaces was more than that of adsorbed HSA. A kinetic model was developed to describe the adsorption process and fitted to the experimental data of frequency shift. It was shown that HSA adsorption could be described by a kinetic equation involving two consecutive reactions. At lower concentration, BSA adsorption only involved the first reaction. At higher concentration, BSA adsorption on PS-modified surface involved two consecutive reactions. All fitted results were well in agreement with the corresponding experimental results. The regression values of reaction rate constants for the HSA and BSA adsorption were obtained. These data exhibited difference in adsorption kinetics under different conditions.

Interaction process between ionic surfactant and protein probed by series piezoelectric quartz crystal technique

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.

Monitoring Environmental WasteWater Using A Piezoelectric Impedance Microbial Sensing Technique

A new method was proposed for monitoring antibiotics and other pollutants based on the assessment of the growth of Staphylococcus aureus (S. aureus) with a piezoelectric impedance analysis technique. During the growth process of S. aureus, the motional resistance variation ( jR1) increases and the frequency shift ( jf) of the piezoelectric quartz crystal (PQC) decreases correspondingly. The two responses can conveniently be used in process analysis. Under the given experimental conditions, a linear relationship between the resistance detection time (RDT) and logarithm value of the concentration of penicillin was obtained in the range of 0.01-10 µg/ml with a detection limit of 4 2 10-3µg/ml. Other antibiotics and pollutants also have the similar linear relationships. The proposed method is simple, convenient and sensitive. Particularly, it does not need the immobilization of the microorganism. This method was used for monitoring of wastewater from a hospital.

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.

A new piezoelectric response model for protein adsorption kinetics at a solid-liquid interface

Abstract A piezoelectric response model on the protein adsorption kinetics at a solid–liquid interface was derived. It was based on the adsorption mechanism of two consecutive reactions and the fact that the thickness-shear-mode acoustic wave sensor responses to the mass accumulation on the sensor surface during the protein adsorption. This model was used to fit the experimental data of frequency shift for the lysozyme adsorption processes onto bare and thioglycollic acid (TGC)-modified silver electrode surfaces and those for the adsorption of bovine serum albumin (BSA) and human serum albumin (HSA) onto bare silver electrode surface. The fitted results were fairly consistent with the corresponding experimental data. The obtained regression values of rate constants, k1 and k2, for the lysozyme adsorption on bare silver surface were 5.93×10−2 and 7.1×10−4 s−1, respectively. And those for the lysozyme adsorption on TGC-modified surface were 7.46×10−2 and 1.46×10−3 s−1, respectively. The values of k1 and k2 for BSA adsorption on bare silver were 1.68×10−2 and 4.52×10−4 s−1, and those for HSA adsorption on bare silver were 2.13×10−2 and 4.06×10−3 s−1, respectively. These results exhibited the difference in adsorption kinetics for these systems.