Electrochemical biosensors principle

Later on, such S-layer-based sensing layers were also used in the development of optical biosensors (optodes), where the electrochemical transduction principle was replaced by an optical one [97] (Fig. 10c). In this approach an oxygen-sensitive fluorescent dye (ruthenium(II) complex) was immobilized on the S-layer in close proximity to the glucose oxidase-sensing layer [97]. The fluorescence of the Ru(II) complex is dynamically quenched by molecular oxygen. Thus, a decrease in the local oxygen pressure as a result of... 

Superoxide electrochemical sensors and biosensors principles, development and applications... 

Superoxide Electrochemical Sensors and Biosensors Principles, Development and Applications... 

Electrochemical biosensors based on well known and therefore most common transducing principles have been investigated intensively for the last 30 years. 

Grieshaber D, MacKenzie R, Voros J, Reimhult E (2008) Electrochemical biosensors -sensor principles and architectures. Sensors 8 1400-1458... 

Coupling between a biologically catalyzed reaction and an electrochemical reaction, referred to as bioelectrocatalysis, is the constructional principle for enzyme-based electrochemical biosensors. This means that the flow of electrons from a donor through the enzyme to an acceptor must reach the electrode in order for the corresponding current to be detected. In case a direct electron transfer between the active site of an enzjane and an electrode is not possible, a small molecular redox active species, e.g. hydrophobic ferrocene, meldola blue and menadione as well as hydrophilic ferricyanide, can be used as an electron transfer mediator. This means that the electrons from the active site of the enzyme reduce the mediator molecule, which, in turn, can diffuse to the electrode, where it donates the electrons upon oxidation. When these mediator molecules are employed for coupling of an enzymatic redox reaction to an electrode at a constant potential, the resulting application can be referred to as mediated amperometry or mediated bioelectrocatalysis. 

BLM systems have been accepted as models of natural biomembranes for applications in medicine, industry, and clinical laboratories. BLMs have therefore been studied extensively in combination with various proteins, and are an excellent choice for the basis for development of electrochemical biosensors. The principles behind the development of BLM-based biosensors are quite simple. The sensing element should be biocompatible and should have a structure similar to a biomembrane. Chemically selective proteins may then be embedded into the membranes with substantial retention of binding activity. The simplest way to test transducer function is by using ligand-receptor binding interactions... 

As mediators different molecules can be applied, e.g. ferrocene, mthenium (111) hexamine or tetrathiafulvalene, which are reoxidized on an electrochemical electrode, preferably carbon (Cass et al. 1984). Such electrochemical working principle allows the miniaturization of a biosensor using screen-printed or thin-film electrodes with adsorbed or immobilized enzymes also facilitating mass production for creating disposable glucose sensors with revenues of several million euros per anno. 

Electrochemical detection has been regarded as particularly appropriate strategy for microfluidic chip systems. Electrochemical biosensors in microfluidic chips enable high sensitivity, low detection limits, reusability, and long-term stability. And the detection mechanism and instmmentation for realization are simple and cost-effective. These valuable features have made electrochemical devices receive considerable attention [20,94,95]. The electrochemical detectors are commercially available for a variety of analyses [96]. The review written by Wang summarized the principles of electrochemical biosensors, important issues, and the state-of-the-art [97]. Lad et al. described recent developments in detecting creatinine by using electrochemical techniques [98]. 

In general, electroanalytical detection principles can be divided into three potentiometry, amperometry, and conductometry (or impedometry). Potentiostats used for electrochemical biosensors are mostly equipped with amperometric and... 

Superoxide Electrochemical Sensors and Biosensors Principles, Development and Applications carbon fiber 10 xm in diameter-------------------------------... 

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