A novel amperometric immunosensor based on the micro electromechanical systems （MEMS） technology, using protein A and self-assembled monolayers （SAMs） for the orientation-controlled immobilization of antibodies, has been developed. Using MEMS technology, an ＂Au, Pt, Pt＂ three-microelectrode system enclosed in a SU-8 micro pool was fabricated. Employing SAMs, a monolayer of protein A was immobilized on the cysteamine modified Au electrode to achieve the orientation-controlled immobilization of the human immunoglobulin （HIgG） antibody. The immunosensor aimed at low unit cost, small dimension, high level of integration and the prospect of a biosensor system-on-a-chip. Cyclic voltammetry and chronoamperometry were conducted to characterize the immunosensor. Compared with the traditional immunosensor using bulky gold electrode or screen-printed electrode and the procedure directly binding protein A to electrode for immobilization of antibodies, it had attractive advantages, such as miniaturization, compatibility with CMOS technology, fast response （30 s）, broad linear range （50-400 pg/L） and low detection limit （10 pg/L） for HIgG. In addition, this immunosensor was easy to be designed into micro array and to realize the simultaneously multi-parameter detection.
One of today's challenges is the integration of ISFETs in chemical and biochemical Microsystems.This article presents a full integration of ISFET chip containing the ISFET/REFET(reference FET) pair,ISFET/REFET amplifiers,bias current generator,as well as a reference electrode structure,all integrated on the same chip based on CMOS technology.The sensor chip was fabricated in a standard 0.35μm CMOS process(Chartered Semiconductor,Singapore).The extra post processing steps have been developed and added for depositing membranes.Finally,the pH response of the integrated sensor was measured with the interface circuit.
