Search

Urease was extracted from several kinds of plant seeds and the kinetic frequency response, the urease activity, Michaelis constants and other kinetic parameters were measured by means of a new device, i.e. a surface acoustic wave (SAW) enzyme sensor system, which was composed of a 61 MHz SAW resonator and a pair of parallel platinum electrodes. Influences such as extracting conditions, pH and temperature and the specificity were also investigated. The method has been successfully applied in the clinical assay of urea in human urine and blood. The results are in agreement with the reported values and also support the clinical diagnosis.

The urea sensor was prepared by combining a surface acoustic wave (SAW) device, in which a SAW resonator operating at 61 MHz and a pair of parallel electrodes were used in series, with urease extracted from green soya bean. The Michaelis constant and maximum reaction rate of the urease were estimated as 2.14 mM and 27.18 kHz min-1, respectively, at pH 7.0 and 25.0 degrees C. Influences of pH, temperature and effectors on the response properties of the SAW urea sensor were investigated. Recovery of the sensor ranged from 95 to 105% and the detection limit of urea was 1.0 micrograms ml-1 (1.7 x 10(-5) M). The proposed sensor has been successfully applied to the rapid determination of urea in human urine samples. The results are consistent with the reported values and also support the clinical diagnosis.

A novel SAW-IDA sensor system was constructed for the first time by connecting the IDA electrodes in series with a SAW resonator. The frequency characteristics of the SAW-IDA sensor in non-aqueous solution were investigated. The effects of the parallel capacitance and cell constant were studied, and were calculated with the circuit network theory. These calculations provide guiding rules for design of the SAW-IDA sensor system. The SAW-IDA sensor was applied to determination of recalcification time and activated partial thromboplastin time of blood plasma. The sensor offers a new and effective way of studying clinical and laboratory haemostasis.

Two methods are described for the determination of l -glutamic acid using a series-electrode piezoelectric quartz crystal sensor. The effect of formaldehyde solution on the frequency shift is discussed. For the calibration curve method, in formaldehyde medium, the detection limit is 3.8 · 10 −5 M, the recovery is 100.4%, the relative standard deviation is 3.32% ( n = 5) and the frequency shift is linear up to 8 · 10 −4 M; in aqueous medium, the above values are 2.0 · 10 −5 M, 99.1%, 3.01% ( n = 6) and 1.1 · 10 −3 M, respectively. The frequencimetric titration method is also described and the lowest titratable concentration of l- glutamic acid is 7.0 · 10 −5 M. The detecting results for tablet samples show good agreement with the values determined by the pharmaceutical method.

A specific and simple method for the determination of arginine was developed by using a new type sensor, a surface acoustic wave (SAW)/conductance sensor system. The assay was based on two coupling reactions involving arginase (E.C. 3.5.3.1) and urease (E.C. 3.5.1.5) with measurement of frequency shift that resulted from the changes of conducting ions produced in the reactions. Arginase was extracted from fresh bovine liver and required no further separation step. The optimum pH (8.5) and reaction medium (Tris-HCl-EDTA, pH 8.5) were determined. We also investigated the influences of reaction medium, pH, temperature, and amount of urease or arginase on the frequency response of the SAW/conductance sensor system. The results were linear up to 4.0 × 10 −4 m of arginine, and the detection limit was 2.0 × 10 −6 m . When the SAW/conductance sensor system was applied to arginine analysis, the results obtained compared well with those of the pharmaceutical method.

A novel and sensitive method for the enzymatic determination of trace amount of mercury ion based on its inhibitory action on urease is proposed. Mercury(II) inhibits the urease-catalysed urea hydrolysis by binding with sulphydryl groups of urease. The inhibited enzymatic reaction is monitored in-situ with a SAW/impedance enzyme transducer which is composed of a SAW resonator oscillating at 61 MHz and a pair of parallel electrodes. The inhibition mechanism of Hg(II) on urease is discussed. The kinetic parameters and inhibition parameters are estimated. The frequency response of the transducer is proportional to mercury concentration over the range of 50-350 ng/mL. The detection limit is 20 ng/mL. The relative standard deviation was 2.9% for six measurements of 150 ng/mL Hg(II). The effect of potential major interferences was investigated. The method was successfully applied to the determination of Hg(II) in waste water and the results obtained by proposed methods compared well with those obtained...

A new type of glutamine biosensor system based on a conductance-surface acoustic wave (SAW) frequency response, in which a SAW resonator oscillating at 61 MHz and a biosensor involving kidney cortex tissue or Escherichia coliform and a pair of parallel electrodes were used, was developed for the determination of glutamine. Glutaminase from porcine kidney or Escherichia coliform was used as a biocatalyst of the hydrolysis reaction of glutamine. There was an excellent linear relationship between the frequency shift response and the glutamine concentration in the range of 6.8 · 10 −4 m to 6.8 · 10 −3 m . The SAW frequency responses obtained from the proposed biosensor system were compared with the conductance response. Some other factors such as pH and selectivity are also discussed.

A surface acoustic wave (SAW) urease sensor system was developed in which a SAW resonator oscillating at 61 MHz and a pair of parallel electrodes were utilized by coupling with urease extracted from pumpkin seeds. The Michaelis constant and the maximum reaction rate of urease were estimated as 2.08 × 10 −3 mol/1 and 8.85 kHz/min, respectively, at pH 7.5 and 25.0 ° C. The analytical characteristics of the urease sensor system, including influences of pH, temperature on frequency response, calibration curves, reproducibility, selectivity over enzymatic interferences were determined. The recovery of the sensor system ranged from 96 to 105% and the experimental detection limit of urea was 0.50 μg/ml (i.e., 8.3 × 10−6 M, S N = 3 ). The SAW urease sensor system possesses the characteristics of good reproducibility and specificity. It has been successfully applied to the analysis of urea in human blood samples. The assay results are consistent with the results tested by conventional colorimetry and also support clinical diagnosis.

A modified algorithm, the iterative Kalman filter, for the analysis of enzymic kinetic data was investigated and successfully applied to the determination of urea in human blood by a urease catalytic reaction. This reaction was monitored with a novel sensor, the surface acoustic wave enzyme sensor system recently proposed by our laboratory. The results were compared with those provided by a calibration graph and classical colorimetry methods. In contrast to these conventional methods, the iterative extended-Kalman filter is shown to be an excellent data analysis method for enzyme kinetic analysis. The urease kinetic parameters were also estimated according to the iterative Kalman filtering results.

A conductivity cell employing a 61 MHz surface acoustic wave resonator-based measurement circuit was applied to the detection of the urea/urease reaction. The kinetic enzymatic parameters of the urease were estimated from the frequency shifts. The effects of pH, temperature and inhibitor on the response of the enzyme conductivity measurement system were investigated. The system was applied to rapid determination of urea in small urine samples. The lowest detection limit of urea was 30 ng/ml.

The circuit network theory was applied to analyse a surface acoustic wave (SAW) impedance system constructed from a 61-MHz SAW resonator and a pair of conductive electrodes in series. Two oscillation equations were derived and used to explain the effects of solution capacitance and cell constant on the frequency characteristics. The effects of the solution density and the viscosity on the frequency response of the SAW impedance system were also investigated. The SAW impedance system can be applied to conductivity measurements in solution with a high concentration background of foreign electrolytes.

2-Diformylmethylene-1,3-diselenole was prepared and condensed with dithiolium phoshonium bromides and dithiolium phosphonates in the presence of base to give dendralene-type vinylogs of TTF bearing a 1,3-diselenole moiety. The electrochemistry of these dendrimers was studied. SEEPR measurements were also carried out. Calculations were carried out on the radical cations and correlated with the EPR values.

To introduce a new method using calcium phosphate cement/Danshen drug delivery system for avascular necrosis of femoral head and to evaluate its clinical outcome.From May 2000 to June 2005, 48 patients (54 hips) with avascular necrosis of femoral head were treated with calcium phosphate cement/Danshen drug delivery system implantation in the involved femoral head. There were 32 males (36 hips) and 16 females (18 hips) with an average age of 38.7 years (26-62 years). Twenty-one cases had the history of drinking or smoking, 15 cases had the history of receivihg hormonotherapy and 2 had the history of injury in hip joint. The disease course was 2-32 months. According to standard of Association Research Circulation Osseous (ARCO) staging, 9 hips were classified as stage I, 31 as stage II and 14 as stage III The operation consisted of removal of necrotic bone under weight-loading cartilage and the implantation of calcium phosphate cement/Danshen drug delivery system, all manipulations were done through a bone tunnel in trochanter. The function of hip joint were evaluated and X-ray films were taken pre- and post-operatively.No phlebothrombosis of leg and foreign body action occurred in all cases, and incision healed by first intention. The postoperative follow-up averaged 42.5 months, ranging from 22 to 73 months. According to the evaluation criterion of Dandong 1995 for adult avascular necrosis of femoral head, the results were excellent in 33 hips, good in 17, fair in 3 and poor in 1, the excellent and good rate was 92.6%.This method is relatively simple with less invasion, it not only improves the microcirculation of femoral head by local application of traditional Chinese medicine, but also provide mechanic buttress in the weight-loaded area, which is beneficial to repair and reconstruction of femoral head. It may be a choice of minimally invasion surgery for femoral head necrosis.

A high-frequency and micro-amplitude vibration based micromanipulator is proposed, which is composed of a micro-motion parallel mechanism having three pure translational degrees of freedom and a micro-vibration unit having one degree of freedom. The micro-vibration unit is fixed on movable platform of the parallel mechanism, and an glass operational needle is connected with the micro-vibration unit. The needle can perform micro operational tasks while the movable platform of parallel mechanism moves in a large region and the unit vibrates with high frequency and micro amplitude. The kinematic and structural parameters of the micro-motion mechanism and vibration unit are designed, the PZT actuators are chosen, and a micromanipulator prototype is fabricated. An experiment system is set up in which the micromanipulator is adopted as a main module. The performance of micromanipulator is validated through two initial operational experiments, one is the vibrational injection of cow oocyte, another is the windowing of cow oocyte membrane, the results of experiments show that the micromanipulator can complete these operations successfully.

A novel micro-dissection manipulator based on ultrasonic vibration is presented in this paper, which uses the 3-RUU pure translational parallel mechanism as its main mechanism, here R, U respectively stand for revolute and universal joint. A vibration unit is fixed on the movable platform of the mechanism and a needle connected to the unit can perform task of micro-dissection for micro living organism by means of piercing as it moves with the platform. Kinematics of the micromanipulator is analyzed based on pseudo rigidity body model (PRBM) method, its kinematic dimensions are identified from performance atlas utilizing the method of dimension model (MODM). Moreover, flexure hinges are designed to create the flexure-based compliance mechanism. Static and dynamic performances of the solid model are analyzed with finite element method. The simulation result illustrates that motion of solid model is coincident to that of PRBM basically, and after a proper frequency of the vibration unit is chosen according to natural frequencies of the solid model the micromanipulator can avoid resonance effectively and implement accurate motion.

This paper presents the inverse kinematic and dynamic analyses of the 3UPS-UP parallel mechanism with three degrees of freedom. For inverse kinematics, the kinematic constraint equations of the movable platform are established according to the structural character of the passive sub-chain, based on which the closed-form inverse kinematic formulas of the mechanism are obtained. In inverse dynamic analysis, the mechanism is decomposed into two parts through cutting the three spherical joints connecting the base and movable platforms, then the constraint forces acting on the parted joints are determined using the force or moment equilibrium's of both the active and passive sub-chains. Finally, the analytic expressions of actuator driving force are derived by means of the force equilibrium of the upper links of active sub-chains.

To study the pattern extrahepatic arteriy supply to hepatocellular carcinoma and catheterization technique for interventional therapy.Routine celiac and superior mesenteric artery angiography was done before transcatheter arterial chemoembolization (TACE) for 78 collateral arterial pathways of 62 hepatocellular carcinoma patients. Super selective catheterization and transcatheter dual arterial chemoembolization (TDACE) to extrahepatic arterial and hepatic arteries were performed.Extrahepatic blood supply was found in 43.1% of hepatocellular carcinoma patients. There was close correlation between extrahepatic arterial blood supply and location of tumor. Success rate of super selective extrahepatic artery catheterization was 71.8% by the combined use of RH, Cobra and SP catheters. Follow-up studies revealed reduction of tumor and complete dense deposition of lipiodol.Ample extrahepatic arterial blood supply is found in hepatocellular carcinoma. Transcatherdual arterial chemoembolization is effective, necessary and feasible for hepatocellular carcinoma with extrahepatic arterial blood supply.

An extended set of equations which describe coupled arginase-urease reactions is presented. The mathematical treatment leads to the development of new equations which relate the lag-time required for the concentration of urea to reach a defined fraction of its steady-state concentration to the kinetic parameters of the enzymes, when the steady-state concentration of urea is small compared to its Michaelis constant value, the coupled arginase-urease reaction was monitored with a surface acoustic wave (SAW) enzyme sensor system, to couple the biochemical selectivity of enzymes with the sensitivity of SAW sensors. The proposed theoretical expressions were verified experimentally. The kinetic parameters of urease and arginase (extracted directly from bovine liver) were examined under theoretical guidance. Dependence of the lag-time of the coupled enzyme reaction on the concentrations of urease and arginase is also described.

A new type of surface acoustic wave sensor system for assaying the activity of pancreatic lipase has been proposed. The assay of this enzyme is based on the change in conductance of the solution caused by the release of a fatty acid, using triolein as a substrate. A linear relationship between frequency response and enzyme concentration is obtained. Kinetic parameters of pancreatic lipase, i.e., the Michaelis constant for triolein and the corresponding maximum initial rate, are estimated to be 5.46 mM and 7551.6 Hz/min, respectively. The effects of temperature and pH value are also investigated.