Here we describe an ion sensitive field effect transistor (ISFET) biosensor, which was designed to
monitor directly the surface charge of structurally altered maltose binding protein (MBP) upon
stimulation with maltose. This study is the first report of the application of a FET biosensor to the
monitoring of conformationally changed proteins. Consequently, a significant drop in current on
the basis of the charge-dependent capacitance measurement has been clearly observed in response
to maltose, but not for the glucose control, thereby indicating that the substrate-specific conformational
properties of the target protein could be successfully monitored using the ISFET. Collectively,
our results clearly suggest that ISFET provide a high fidelity system for the detection of maltoseinduced
structural alterations in MBP.