An enzyme electrode with response independent of the thickness of the enzyme layer

The common biosensor geometry where the immobilisation matrix is cast directly over the electrode has been shown, using a numerical model, to be highly sensitive to the thickness of the biorecognition layer. An alternative geometry where a permeable electrode is located on the solution side of the matrix, such that the substrates must pass through the electrode before being able to react with the enzyme, was shown to give a thickness independent response. The theoretical conclusions for this geometry appear to be verified by initial experimental results. The alternative geometry was successfully employed in the development of an electrochemical formaldehyde biosensor.