Sensitivity control of ion-selective biosensors by electrophoretically mediated analyte transport

We present a new method for changing the sensitivity of any microsensor tha t functions by converting an ion into an uncharged molecule which is subseq uently detected. The method is based on attraction or repulsion of ions fro m the sensor tip by an applied potential. We have named the principle elect rophoretic sensitivity control (ESC), and it was used to enhance the perfor mance of microscale NO3- biosensors. Applying positive ESC potentials made it possible to increase the sensitivity by a factor of up to 20, whereas ne gative ESC potentials decrease the sensitivity by a factor of up to 1000. T he upper limit for sensitivity enhancement in the tested NO3- biosensors wa s set by a tendency of bacteria in the sensor tip to be electrophoretically transported away at high positive ESC potentials. The possibility for decr easing the sensitivity by applying negative ESC potentials offers a conveni ent method for performing a zero check even when the analyte is present. (C ) 1999 Elsevier Science B.V. All rights reserved.