An enzyme immunosensor for the electrochemical determination of the tumor antigen α-fetoprotein

A specific sensor for a tumor antigen, α-fetoprotein (AFP) can be prepared from a membrane with immobilized antibody and an oxygen probe with a permeable teflon membrane. Anti-AFP antibody is covalently immobilized on a membrane prepared from cellulose triacetate, 1,8-diamino-4-aminomethyloctane and glutaraldehyde. The sensor is applied to enzyme immunoassay based on competitive antigen-antibody reaction with catalase-labelled antigen. After competitive binding of free and catalase-labelled AFP, the sensor is examined for catalase activity by amperometric measurement after addition of hydrogen peroxide. AFP can be determined in the range 10^-11–10^-8 g ml^-1.