Preparation and Characteristics of Organic Thin Membrane for Biosensor

Abstract

A polyvinylbutyral (PVB) membrane was applied to the surface of a silicon nitride which is the gate insulator of the ISFET (Ion Sensitive Field Effect, Transistor). The membrane exhibited good adhesive properties and was used for urease immobililation. The water content of the membrane was 27.6% with- a thickness of 23 μm. The surface structure of the membrane was observed by scanning electron microscopy, which revealed a regular porous microfilter arrangement with a mean pore diameter of 0.25 μm. Immobilized urease activity in this membrane was approximately 20% higher than when a urease-triacetylcellulose membrane was used.
H⁺-ATPase in biologic al membrane is known as an enzyme to produce or hydrolyze, ATP. The ATP-FET sensor was constructed using immobilized H⁺-ATPase' PVB m embrane. A linear relationship was obtained between the initial rate of change of the 'differential gate output voltage and the logarithm of the ATP concentration over the range 0.2-1.0mmol⋅dm^-3- ATP. The optimum pH was 9.0 at 40°C. The selectivity was good. The ATP sensing system exhibited a response to 1 mmol⋅dm^-3 ATP for at least two weeks.
Human serum albumin has the minus charge at pH 7.0, The immuno-FET sensor was constructed. Anti-human serum albumin was immobilized on the, ISFET using PVB membrane. Binding of the human serum albumin to, , the anti-human serum albumin caused a decrease in the differential gate output voltage of the system. This response is attributed to the minus charge of human serum albumin. A linear relationship was obtained in the range 0.01-1 mg⋅ml^-1