Ronghui Wang

Immobilization of DNA on silver surface of bulk acoustic wave sensor and its application to the study of UV-C damage

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.

Enzymatic assay of acid phosphatase and microanalysis of Cu2+ and Ag+ with a SAW-impedance sensor

Abstract Using adenosine-5′-monophosphate (5′-AMP) as a substrate, the surface acoustic wave (SAW)-impedance sensor has been successfully applied to detection of acid phosphatase and microanalysis of Cu 2+ and Ag + . The assay of acid phosphatase is based on the change in conductance of the solution caused by enzymatic reaction between 5′-AMP and acid phosphatase. The microanalysis of Cu 2+ and Ag + is based on its inhibitory action on enzyme. The Michaelis constant and the corresponding maximum initial rate are estimated to be 4.49 × 10 −3 mol l −1 and 8,841 Hz min −1 , respectively, at pH 4.5 and 28°C. The recovery of the sensor system ranges from 97.9–107.0% (n = 6). The experimental detection limit of enzyme is 0.7 mU ml −1 . The inhibition of Cu 2+ and Ag + is a noncompetitive one. The possible inhibition mechanism is discussed. The kinetic parameters and inhibition parameters are estimated. The detection limits of Cu 2+ and Ag + is 7.6 × 10 −7 m and 2.0 × 10 −8 M . Some other factors such as temperature, pH value, and active energy are also discussed.

Bovine serum albumin as a means to immobilize DNA on a silver-plated bulk acoustic wave DNA biosensor.

A simple, inexpensive, on-line bulk acoustic wave (BAW) DNA biosensor is proposed by using an Ag-plated surface rather than the conventional Au surface. Bovine serum albumin (BSA) is used as an active coating for DNA immobilization. Impedance analysis reveals that the film composed of didodecyl dithiono-oxamide (DDDTO) and BSA can dramatically enhance the amount of immobilized DNA. Detection of dissociation and hybridization of immobilized DNA is demonstrated as an example of the potential application of this type of acoustic wave DNA biosensor in clinical practice.

Surface acoustic wave enzyme sensor applied to the kinetic assay of acid phosphatase

The acid phosphatase hydrolysis of phenylphosphoric acid (at pH 5 and at 25 °C) with a new type of liquid-immersion surface acoustic wave enzyme sensor (SAW) is described. A mathematical model was derived to estimate the kinetic parameters and to determine the concentrations of enzyme and substrate. The inhibition of the product to the enzyme activity was involved in the model. The Michaelis constant was estimated to be 1.17 × 10–4 mol l–1. The recovery of the sensor system was 97.4–104.4%(n= 6). The effects of temperature and pH on the enzyme activity were discussed. The proposed model compared favourably with the linear method which indicated that the model gave more precise results.

Enzymatic Determination of Organo-Phosphorus Pesticides with a Surface Acoustic Wave Impedance Sensor

Abstract A novel and sensitive method, based on the inhibition of the lipase-catalyzed hydrolysis by combining hydroxyle groups of lipase with organophosphorous pesticide, is proposed for the enzymatic determination of organophosphorous pesticide. The inhibited enzymatic reaction is monitored with an SAW/impedance enzyme transducer, which is composed of an SAW resonator, oscillating at 61 MHz, and a pair of parallel electrodes. Employing the method described, the frequency response of the transducer is proportional to organophosphorus pesticide concentration over the range of 227ng/mL - 2.27μg/mL; the detection limit is 76ng/mL. The effects of temperature, pH, incubation, and solvent are also investigated. The method was successfully applied to the determination of dichlovors residues in the root, stem, and blade of Chinese cabbage.

Determination of dipyridamole by modified extraction-gravimetry with a surface acoustic wave resonator sensor

A simple and sensitive extraction-gravimetric method for the determination of dipyridamole is presented. The method is based on the extraction of free dipyridamole with chloroform, after neutralization with a basic agent, followed by measurement of the frequency shift response of the specially designed surface acoustic wave resonator sensor after evaporation of the extractant from the surface of the resonator. The frequency shift response was proportional to the amount of dipyridamole in the range 0.065-1.12 micrograms. Experimental parameters and the effect of interfering substances on the assay of dipyridamole were also examined in this study. The method was applied to the determination of dipyridamole in tablets.

Bulk acoustic wave biological detection of cefotaxime sodium

Abstract A bulk acoustic wave (BAW) impedance sensor has been applied to rapid determination of in vitro concentrations of cefotaxime sodium. The method based on the growth frequency curve of Proteus Morganii, inhibited by cefotaxime sodium, is continuously monitored by using a BAW impedance sensor. The growth kinetic parameter, e.g. asymptote or maximum frequency shift (AF, Hz), estimated by fitting a modified Gompertz model to the growth frequency curve, is proportional to the logarithm of antibiotic concentration. The proposed method exhibits a favourable response to 0.25 – 20.0 μg mL−1 cefotaxime sodium with a detection limit of 0.03 μg mL−1, and the recoveries range from 97.3 to 107.5% (n=9). The results are in good agreement with those obtained by the conventional disk diffusion test (DDT) method. The effects of temperature and pH on the determination are discussed and in vitro susceptibility to cefotaxime of the genus Proteus has been investigated in detail. On leave from Department of Mathematics,...

Rapid determination of dimethoate with a surface acoustic wave impedance sensor system

Based on the principle of enzyme inhibition, a novel and sensitive lipase biosensor to determine organophosphorus pesticide is presented. Contact of the enzyme with pesticide samples results in specific inhibition of enzyme activity. Sensor calibration was possible by correlating the inhibition of enzyme activity with various concentrations of pesticide compound in a buffer solution. The sensor was successfully used to determine pesticide concentrations ranging from a low of 167ng/ml to 1.34μg/ml, and the detection limit is 81ng/ml. The effects of temperature, pH value, incubation time and solvent were also investigated. The sensor was also applied to the determination of dimethoate residues in the peel and flesh of tomato.

Determination of Organophosphorus Pesticides Based on the Inhibition of Lipase with a Surface Acoustic Wave Sensor System

Abstract A convenient and sensitive method based on the inhibition of the lipase-catalyzed hydrolysis by binding hydroxyl groups of lipase with organophosphorus pesticide is described for the enzymatic determination of organophosphorus pesticides. Employing the method proposed, the frequency response is proportional to organophosphorus pesticide concentration over the range of 250 ng/ml∼1.25 μg/ml. the detection limit is 58 ng/ml. The effects of temperature, pH value, incubation time and solvent are also investigated.

Rapid determination of ribonuclease and microanalysis of heparin with a SAW/conductance sensor

A new method using a surface acoustic wave (SAW)/conductance sensor has been described in this paper for rapid determination of ribonuclease (RNase) and microanalysis of heparin. The assay of RNase is based on the change in conductance of the solution caused by enzymatic reaction between ribonucleic acid (RNA) and RNase and the analysis of heparin is based on its inhibitory action on RNase. A linear relationship between frequency response and enzyme concentration is obtained and the detection limit of RNase is evaluated to be 0.17 mug ml(-1). The recovery of the sensor system ranges from 95.8 to 105.0%. The inhibition of heparin is a competitive one and the possible inhibition mechanism is discussed. The kinetic parameters and inhibition parameters are estimated. The calibration graph is rectilinear for </= 8 mug ml(-1) of heparin and the detection limit is 0.1 mug ml(-1). The influence of pH value on the inhibition of RNase by heparin has been investigated and the effects of Ca(2+), Mg(2+) are also discussed.