The Research On Magnetoelastic Biosensor And Its Application In Biochemical Analysis

This dissertation focuses on the magnetoealstic biosensor and its applications in biochemical analysis. In response to a time varying magnetic field, the magnetoelastic sensor efficiently couples and translates magnetic energy to mechanical energy. The elastic energy mechanically deforms the sensor, causing it mechanically vibrate along to its length. If the frequency of the ac field is equal to the mechanical resonance frequency of the sensor, the vibration amplitude is maximum, and the sensor vibrates at its characteristic resonance frequency that shifts in response to mass loading. Since the sensor material is also magnetostrictive, the mechanical oscillation in turn generates a magnetic flux that can be remotely detected using a pick-up coil. The sensor is totally passive. No physical connections between the sensor and the detection system are required, nor is any internal power required. The wireless nature of the magnetoelastic sensor makes it a powerful candidate for in situ and in vivo analysis.In this dissertation, three kinds magnetoelastic biosensors were developed:(1)α-Amylase biosensor. The sensor is fabricated by immobilizing a layer of starch gel on the thick-film ribbon-like magnetoelastic sensor. When exposed toα-amylase the resonance frequency of the starch gel-immobilized sensor increases in proportion to the starch hydrolyzation byα-amylase allowing for its quantification. The starch-immobilized sensor can also be used for the detection of urea and methamidophos based on the inhibition of urea and methamidophos toα-amylase. The sensor described here can detect 75 U/ml to 125 U/ml ofα-amylase, as well as 0.02~0.2% of methamidophos, and 0.3~8 mmol/l of urea.(2) Trypsin sensor. The trypsin sensor is fabricated by first coating a magnetoelastic ribbon-like sensor with a pH-sensitive and then upon it a layer of trypsin. The trypsin-catalyzed hydrolysis of N-α-benzoyl-L-arginine ethyl ester (BAEE) decreases the ambient pH, resulting in the pH-responsive polymer shrinking, and consequently the resonance frequency of the sensor increasing due to the decreased mass loading. The kinetic parameters of both the immobilized and free trypsin are measured. Immobilization of trypsin resulted in the enzyme activity decreasing by about 50%.(3) A wireless mass-sensitive magnetoelastic biosensor for convenient and sensitive detection of acid phosphatase (ACP). The measurement is based on the enzymatic hydrolysis of 5-bromo-4-chloro-3-indolyl phosphate (BCIP),producing a...