Shinichiro Gondo

Studies on dynamic behavior of the biosensor based on immobilized glucoamylase-glucose oxidase membrane

Frequency response of the glucose/maltose biosensors based on immobilized glucoamylase and glucose oxidase membranes of different thickness were investigated with the sinusoidal signal generator of substrate concentration. The results were modeled by the serial combination of the dead time and the first order response blocks, and time constants and dead times were estimated. The estimated value of time constant ranged from 4.5 to 13.2 s and that of the dead time from 3.2 to 7.7 s with the tendency that both time constant and dead time increase as membrane thickness increases and number of enzymatic reaction steps increases.

Effects of nonionic surfactants on electrochemical behavior of ubiquinone and menaquinone incorporated in a carbon paste electrode.

A carbon paste electrode, in which the carbon particles were coated with a thin layer of a nonionic surfactant (NIS), was constructed with a pasting liquid containing ubiquinone (UQ) or menaquinone (MQ). It has revealed that the layer acts not only as a diffusion barrier but also as a matrix for the redox reaction of quinones at electrode surface, and its effects on the electrochemical behavior of quinones depend on both the physico-chemical structure of a surfactant and the kind of quinones. Further, such a modification was applied to the preparation of an enzyme electrode in which the quinone molecule act as a redox mediator and the influences on the sensitivity of the glucose biosensor was demonstrated.

Glucose Sensor Based on Ubiquinone-Modified Carbon Paste Electrode

Abstract Two types of carbon paste electrodes containing ubiquinone (CoQ) and glucose oxidase (GOD) were constructed, and their electrochemistry and amperometric response to substrate were investigated. For one type of electrode in which the surface of carbon particles was covered with a part of CoQ molecules added, it was found that the CoQ adsorbed on the carbon particles exerted an insulating effect on the electrode reaction. For the other type of electrode in which the surface was preadsorbed with GOD and most of CoQ was dissolved in the liquid paraffin phase, it was demonstrated that CoQ served as an electron transfer mediator. The latter electrode showed amperometric responses to glucose in the applied potential range 300 – 500 mV and a linear response in the range 0.2 – 4.0 mM in an electrolyte solution (pH 7.0).

Sinusoidal signal generator for the study of dynamic behavior of biosensors

Abstract The generator of sinusoidal signals of substrate concentration was developed using two sets of twin cylinders. The generator can generate the sinusoidal wave of substrate concentration of required frequency and amplitude by the adjustment of feeding substrate concentration and of the frequency and stroke of reciprocal motion of plungers. The performance characteristic of the generator developed were investigated. The generator was applied to the study of frequency response of a glucose sensor based on immobilized glucose oxidase membrane. The frequency response of the glucose sensor was modeled, as the first approximation, by the first order system with dead time.

Immobilization of enzyme to platinum electrode and its use as enzyme electrode

A glucose electrode was fabricated by immobilizing glucose oxidase covalently onto a platinized platinum electrode. The sensor showed rapid response with response time of 2—4 s, and also the linear response to the glucose concentration, ranging from 2 x 10-3 to 5 mM. The sensitivity was found to be correlated with the surface area of a base electrode used.

Glucose sensor with immobilized glucose oxidase-glucose isomerase membrane

Abstract A glucose sensor, i.e., an oxygen detection electrode with immobilized glucose oxidase, has been studied by several researchers as a novel analytical technique which can simplify tedious steps in conventional methods of glucose determination. In a glucose sensor of such construction, any glocuse oxidase inhibition will impair the performance characteristics of the sensor, sometimes seriously. Assuming the competitive inhibition of α-D-glucose on the oxidation of β-D-glucose catalyzed by glucose oxidase, the rate equation including the inhibition term was derived with the object of improving the performance of the glucose sensor by eliminating the glucose oxidase inhibition. In our experimental investigation, glucose isomerase was used as an enzyme which consumes α-D-glucose as a substrate. Glucose oxidase and glucose isomerase were immobilized with solubilized collagen fibrils as supporting material in two ways. One involved a single layered structure where two enzymes were immobilized on the same membrane. The other procedure involved a double layered structure where each enzyme was immobilized separately on each layer of a double layered membrane. These membranes were attached to the dissolved oxygen sensor to provide a glucose sensor. In the case of the double layered membrane, the glucose isomerase layer was arranged to face the outer glucose solution. The limitation of sensor response enhancement on increasing the amount of glucose oxidase used for immobilization per unit mass of supporting material, was overcome by the addition of glucose isomerase. The stability of the sensor was also improved remarkably. The double layered membrane was superior to the single layered membrane both in response and stability. This new type of glucose sensor with a double layered, immobilized, two enzyme membrane was applied successfully to the determination of glucose in a maltose hydrolysis reactor.

Frequency Response of the Glucose Sensor Based on Immobilized Glucose Oxidase Membrane

Frequency response of the glucose sensor based on the immobilized glucose oxidase membrane was investigated experimentally by giving the sinusoidal change of glucose concentration to the glucose sensor and observing its output signal. Observed values of gains and phase lags of the frequency response of the glucose sensor followed the frequency response model of the first-order with dead time; The time constant and also the dead time were estimated and found to decrease as the amount of enzyme immobilized in the membrane increased and the thickness of the membrane decreased.

Hydrolysis of soluble starch by rotary disc of immobilized glucoamylase

Abstract Immobilized glucoamylase sheet was prepared using soluble collagen prepared from cow hide powder as the support material. The immobilized glucoamylase sheet was attached to the rotary disc and the rates of hydrolysis of maltose and soluble starch in the tank were measured. Qualitative discussions are made of the effect of stirring speed of immobilized enzyme disc on the overall reaction rate.

Rotary Multidisc Reactor of Collagen Supported Immobilized Glucoamylase

A rotary multidisc reactor of immobilized glucoamylase was constructed; and the hydrolysis rates of maltose (Katayama Kagaku Co., Japan) and soluble starch (Katayama Kagaku Co., Japan) were measured. The parameters included in the kinetic equation were estimated for these reaction systems.