The enzymes are less compatible with the QCM signal transduction. Changes in the reaction with low-molecular substrates do not provide significant mass changes, even though insoluble products can be produced. The peroxidase-based disruption of the polymeric substrate involved in the surface layer is a rare exception (Karousos et al. 2002 ). In the biosensor, 3.3′-diaminobenzidine was enzymatically converted into an insoluble product. The reaction was applied for the