ABSTRACT
Enzymatic biosensors provide fast detection, very good selectivity, and high sensitivity. The construction of functional mediator (e.g., protein)–containing layers on the transducer is critical to promote electron transfer between enzymes and the electrode surface by facilitating redox mediator activity. The control of layer thickness, sequence, density, and roughness is critical for functionality. However, well-established techniques such as the Langmuir–Blodgett method and molecular self-assembly are not used for protein immobilization because water-soluble proteins have difficulty spreading on the air–water surface. In contrast, layer-by-layer (LBL) adsorption techniques based on the electrostatic force between polyelectrolytes and proteins are able to create ultrathin multicomponent architectures by simply alternating adsorption in cationic and anionic polyelectrolytes. The characterization of multicomponent films by using a quartz crystal microbalance (QCM) and atomic force microscopy (AFM) is also described.
