Over the past 10 years, it has become possible to use the ISFET device as a cellular probe. The advantages of the ISFET, as opposed to conventional microelectrodes are (i) the possibility of measuring metabolic activity (via small pH changes in the culture media); (ii) the local amplification of the signal yielding less interference and noise and (iii) the possibility to multiplex transistor ar...

During recent decades increasing interest has been shown in the development of biosensors based on ion sensitive field effect transistors (ISFETs). Many ISFET– based pH sensors have been already commercialized and attempts have also been made to commercialize ISFETbased biosensors for applications in the fields of medical, environmental, food safety, military and biotechnology areas. The growin...

An integrated and new interface circuit with temperature compensation has been developed to enhance the ISFET readout circuit stability. The bridge-type floating source circuit suitable for sensor array processing has been proposed to maintain reliable constant drain–source voltage and constant drain current (CVCC) conditions for measuring the threshold voltage variation of ISFET due to the cor...

A cationic surfactant ion-selective field-effect transistor (cationic surfactant-ISFET) has been developed based on the tetraphenylborate derivative known as sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate. The cationic surfactant-ISFET shows an almost Nernstian response to tetradecyldimethylbenzylammonium chloride (Zephiramine) over a concentration range between 1.0 x 10(-6) M and 1.0 x ...

The operation of a pH (Hþ ion concentration) sensitive ion-sensitive field-effect transistor (ISFET) microsystem with a sensitivity of 40– 45 mV=pH is demonstrated. This system has two identical ISFETs as the inputs to a pair of ISFET operational transconductance amplifiers (IOTAs) arranged in a novel differential architecture. The IOTAs have different sized p-MOSFET load transistors that enabl...

Biofilm formation in microfluidic channels is difficult to detect because sampling volumes are too small for conventional turbidity measurements. To detect biofilm formation, we used an ion-sensitive field-effect transistor (ISFET) measurement system to measure pH changes in small volumes of bacterial suspension. Cells of Micrococcus luteus (M. luteus) were cultured in polystyrene (PS) microtub...

The extracellular ionic microenvironment has a close relationship to biological activities such as by cellular respiration, cancer development, and immune response. A system composed of ion-sensitive field-effect transistors (ISFET), cells, and program-controlled fluidics has enabled the acquisition of real-time information about the integrity of the cell membrane via pH measurement. Here we ai...

Electronic circuit simulation programs like SPICE have built-in models for semiconductor devices like MOSFET and BJT. However, they do not provide models for electrochemical sensors like ISFETs (Ion-Sensitive Field-Effect Transistors). This paper presents a behavioral macromodel for ISFET-based pH-sensors implemented using PSPICETM. The macromodel is then utilized to present a comparative analy...

The ion-step measuring method was used to determine absolute heparin concentrations in PBS and blood plasma with a Ta2O5 ISFET on to which a monolayer of protamine had been immobilized. Heparin is a highly negatively charged polysaccharide, which is used clinically to delay the clotting of blood. Protamine acts as an affinity ligand for heparin. The response of the ISFET system on a step-wise i...