Amperometric microcell for enzyme activity measurements

A small-volume cell was developed for enzyme activity measurements. The cell contained a detector chip, which was prepared using photolithographic and electrochemical techniques. The enzyme-catalyzed reaction takes place in a thin film inside the cell, and the concentration changes are followed in time with an amperometric detector. The combination of the thin-layer reaction medium and surface detection allows achievement of high sensitivity with very low sample volumes. The cell can be prepared as an inexpensive single-shot test device. The analytical performance of the cell was checked with several enzymes of clinical importance. Demonstration measurements were made with robust glucose oxidase. Then, an analytical procedure was worked out for the measurement of putrescine oxidase activity, an indicator for premature rupture of the amniotic membrane. Finally, two different reaction schemes were investigated for the activity determination of the myocardial infarction marker, creatine kinase.