Electrochemical microsystem with porous matrix packed-beds for enzyme analysis

The enzyme activity was determined using a freeze-dried substrate-bovine serum albumin (BSA) matrix packed in a micro flow channel. The device used in the analysis consisted of a glass chip with an amperometric l-glutamate sensor and a polydimethylsiloxane (PDMS) sheet with a micro flow channel. Glutamic oxaloacetic transaminase (GOT), glutamic pyruvic transaminase (GPT), and γ-glutamyl transpeptidase (γ-GTP) were used as the test enzymes, and a reaction product, l-glutamate, was detected using an integrated l-glutamate sensor. The very porous structure of the matrix and very fine substrate precipitates facilitated the smooth introduction of a sample solution and the rapid dissolution of the substrates. The device was demonstrated to be more effective than other devices with different flow channel structures. In one device, the substrates were precipitated on the wall of the flow channel in an atmosphere at room temperature. In another device, the enzyme solution and the substrate solution were mixed in a Y-shaped flow channel. The initial rate of the current increase was much higher with the freeze-dried substrates. The novel device could also be used to determine the activities of the enzymes in human serum samples. The relationship between the slope of the response curve and the enzyme activities was linear up to 100 U l−1 for GOT, 100 U l−1 for GPT, and 300 U l−1 for γ-GTP. The device could also be used for the analysis of enzyme kinetics by changing the amount of the loaded substrates.