A wireless magnetoelastic α-amylase sensor

A remote query, inexpensive and hence readily disposable α-amylase biosensor is described. The sensor is fabricated by immobilizing a layer of starch gel on a thick-film ribbon-like magnetoelastic sensor. In response to an ac magnetic field the magnetoelastic sensor replies with a return magnetic field, the characteristic resonance frequency of which is inversely dependent upon the attached mass load of the sensor. When exposed to α-amylase the resonance frequency of the starch gel-immobilized sensor increases in proportion to the starch hydrolyzation by α-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 to α-amylase. The sensor described here can detect 75 to 125 U/ml α-amylase, as well as 0.02–0.2% methamidophos, and 0.3–8 mmol/l urea.