Thick film biosensors for metabolites in undiluted whole blood and plasma samples.

The new electrochemical thick film biosensors from Roche Diagnostics are presented. Following considerations about the principal requirements that biosensors have to fulfil to be useful for diagnostic purposes, the basic design of these thick film biosensors is shown. In this paper, the new generation of biosensors for glucose, lactate and urea are presented, as well as data from a new biosensor for creatinine. All biosensors are designed for multiple use, at minimum 500 samples or 1 week in-use (depending on type of enzyme used), for determinations in undiluted whole blood or plasma, with extra electrodes to compensate for interferences. The sensors are integrated in a disposable cassette requiring 38 microtl sample volume. The analytical ranges of the sensors scope well with the normal and pathological concentrations of metabolites in human blood, e.g. for glucose 0.5-40.0 mmol/L. Both biosensors and interference-compensating electrodes are developed to have a cycle time of 90 s maximum. Method comparison diagrams show excellent correlation of results obtained by biosensors compared to results achieved by reference methods. In addition, the possibility of urea and creatinine determinations in diluted urine is presented.