Biosensors Based on Immobilization of Proteins in Supramolecular Assemblies for the Detection of Environmental Relevant Analytes

Methods to immobilize proteins are of particular relevance for biosensing. In biosensors, proteins have to be assembled according to suitable architectures on solid surfaces such as electrodes, optical windows, or the organic semiconductor layer of electronic devices and their integrity and activity have to be preserved. This chapter deals with the use of immobilized proteins in several types of biosensors. The importance of molecular architecture control, particularly with synergistic combination of proteins and "other" material, is evidenced. Different methodologies for protein assembly are described, highlighting the environmental applications of the protein based biosensors. Results from the literature, grouped into large areas covering optical and electrochemical biosensors and also sensing exploiting field-effect transistors, are reported. Layer by layer (LbL) immobilization of proteins on the transparent substrate of optical biosensors is proposed for its advantageous control of molecular architecture and versatility to accommodate layers having different functionalities. Covalent immobilization is evaluated as an alternative process for the controlled incorporation of the recognition element on/into the electrode surface, in the case of electrochemical transducers. Finally, the integration of immobilized proteins in electronic devices is presented, especially in the context of using field-effect transistors (FETs) for biosensing. It is hoped that this survey may assist researchers in choosing materials, molecular architectures, and detection principles, which may be tailored for specific applications.