Penicillin-ISFET Biosensor And Signal Conditioning Circuit

Penicillin, one of the most common antibiotics, is widely used to treat animals'inflammation and infection for its low price, easy access and strong sterilizing ability. If the animal is slaughtered or milked before penicillin is metabolized completely, it will result in penicillin residue in the animal foods. Once people eat these foods, penicillin residue remains in these foods would induce forming the anti-antibiotics bacterium, and it also would cause anaphylaxis in hypersensitive people. In industry, penicillin residue in fermenting milk would restrain the growth of the zymogens. It's of high social economic value to establish a fast detection method in many fields, such as detecting penicillin residue to control animal food safety, safeguarding consumers'health and protecting industry's production.This thesis analyzes the deficiency of the past method of penicillin residue detection, and proposes a new method-biosensors based on ion-sensitive field-effect transistors(ISFET). This method is easy to operate, and sample does not need to do the pretreatment, and its detection speed is very fast, and it has high accuracy. Based on the structure of ISFET, the paper analyzes the mechanism of ISFET from chemical angle, and develops the expression between potential of the interface and concentration of H+. Thus the author gets the factors which influence the sensitivity of ISFET and the range of linearity. In terms of the characteristics of ISFET, comparing with MOSFET, the paper infers the equation of voltage and current, and develops a Simulation Program with Integrated Circuit Emphasis (SPICE) model which can describe the electrics behavior of ISFET. According to the simulation test, this model could reflect the voltage and current characteristics of ISFET effectively. In the measurement patterns of sensor, by the comparison with several methods, the author finally chooses the current measurement, and designs signal conditioning circuit.As a very important branch of biosensor, ISFET-biosensor has very high sensitivity, high selectivity, easy integration and miniaturization. So it has prodigious superiority in the fields of intellectualization, online and real time analysis.