ABSTRACT
Enzyme FET (Field effect transister) is a kind of new device developed recently, which is made through the combination of semiconductor and biological technology. Enzyme FET with differential output can provide automatic compensation for some external factors, e.g. variations of temperature and pH in bulk solution. By using differential measurement, drift of the output voltage with decreased time, and the sensor being miniaturized through the use of "pseudo-reference electrode". Differential model penicillin-ENFET was constructed by modifying one of the dual ISFET gate with a membrane of cross-linked bovine serum albumin (BSA)-penicillinase and the other with a membrane of cross-linked BSA. It responded linearly to penicillin in 0.01M and 0.02M phosphate buffer with sensitivities of 6.5-7.0mV/mM and 3.2-3.6mV/mM over the concentration ranges of 0.5-14mM and 0.5-25mM, respectively. When immersed in 0.01M phosphate buffer and stored in 4 degrees C, this detector had a life time of over 6 months with only a slight decline of output. Accumulative total usage times of the detector could be over one thousand. Finally, the practical applications of differential model penicillin-ENFET in assaying penicillin concentration of fermentation broth are concerned.
