Catalysis-based biosensors

In enzyme-based biosensors, the enzyme reacts selectively with its substrate. The detailed mode of action of enzymes can be found in any standard biochemistry book, and here we will remind only the basic enzyme catalysis mechanism, which is as follows [20, 21] ... 

A biosensor based on mediator-free CYP2B4 catalysis by immobilizing monomer-ized CYP2B4 in montmorillonite was studied by Shumyantseva [222], When substrates were added to air saturated buffer solution, there was an increase in the reduction current. A typical concentration dependence measured in chronamperometry is shown for aminopyrine and benzphetamine (Fig. 17.4). The reaction was inhibited by metyrap-one. This indicates the catalytic activity of CYP2B4 in the presence of substrate. 

Nanocomposites based on polymers and nanoparticles (NPs) are diverse and versatile functional materials, with applications ranging from electronic device fabrication to biosensors and catalysis [1-7]. The controllable polymer chain length, tunable NP size and core materials, and various side-chain and ligand functionahzation enable these macromolecular building blocks... 

In the development and application of biosensors based on enzymes several factors required for the catalytic process have to be taken into account, which are either directly involved in catalysis or influence the formation of the enzyme-substrate complex. They are designated coenzymes, prosthetic groups, and effectors. 

The majority of the biosensors that have been reported are based on the deposition of biologically active species such as enzymes and antibodies at the surface of an electrochemical or optical transducer. The most common principle is to identify the analyte by use of a chemically selective enzyme. The enzyme-substrate reaction produces a secondary chemical signal by means of catalysis, e.g. H" or H2O2. This signal is then recognized and quantitatively converted to an electrical signal, e.g. a potential, a current, or a change of absorption or fluorescence, by a suitable transducer. 

An important application of CyD complexes is in the field of mediated electrocatalysis and bioelectrocatalysis. Detection of a target analyte using a biosensor based on a redox enzyme is well recognized as a more convenient solution than one based on the electrochemistry of reaction products. An ideal mediator for electrocatalysis should be soluble in water or easily anchored on an electrode surface. CyDs have often been employed in solubilizing hydrophobic molecules used either as mediators in catalysis or occurring as the products of catalytic reactions. In the latter case, their role was to avoid fouling of the electrode surface. 

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