A novel enzyme immunoassay based on potentiometric measurement of molecular adsorption events by an extended-gate field-effect transistor sensor.

We developed a novel enzyme immunoassay based on a potentiometric measurement of molecular adsorption events by using an extended-gate field-effect transistor (FET) sensor. The adsorbing rate of a thiol compound on a gold surface was found to depend on the concentration of the compound. To construct an electrochemical enzyme immunoassay system by using the sensor, the enzyme chemistry of acetylcholinesterase (AChE) to generate a thiol compound was used and combined with the enzyme-linked immunosorbent assays (ELISA). After the AChE-catalyzed reaction, the amount of the antigen was obtained by detecting the adsorbing rate of the generated thiol compound on the gold electrode using the FET sensor. The measurement stability was also found to improve when a high frequency voltage of 10 kHz or more was superimposed to the reference electrode. The signal corresponding to a range between 1 and 250 pg/mL of Interleukin 1 beta was obtained by the FET sensor when a voltage of 1 MHz was superimposed onto the reference electrode. The FET sensor based ELISA used in this measurement technique can successfully detect Interleukin 1 beta at concentrations as low as 1 pg/mL.