Biorecognition process

The branched polysaccharide dextran is assembled with alkanethiol-modified gold nanoparticles and the resulting nanocomposite is then functionalized to facilitate the specific binding of target biomolecules. This biorecognition process can be easily detected by particle plasmon resonance (PPR), based on the optical properties of gold nanoparticles [163]. 

In recent years many efforts have been made to develop immunochemical techniques integrating the recognition elements and the detection components, in order to obtain small devices with the ability to carry out direct, selective, and continuous measurements of one or several analytes present in the sample. In this context biosensors can fulfill these requirements. Biosensors are analytical devices consisting of a biological component (enzyme, receptor, DNA, cell, Ab, etc.) in intimate contact with a physical transducer that converts the biorecognition process into a measurable signal (electrical or optical) (see Fig. 4). In... 

The cantilever deflection, Az, generated by a surface stress change, Act, (due to a biorecognition process, for example) depends on the microcantilevers dimensions (length L and thickness h) and its material s properties (Young s modulus E and Poisson coefficient v) following the Stoney s equation ... 

Fig. 4 Schematic representation of a generic biosensor with the essential components (biorecognition element, transducer, and electronic part involved in data processing and display)...

An electrochemical immunosensor includes a transducer (a current-conductive strip deposited on a polymer substrate) and a biorecognition substance (an antigen or antibodies) immobilized on the transducer surface. The formation of an immune complex and localization of non-antigen-specific antibodies (proteins) on this complex, which are usually labeled with enzymes, and a substrate in the solution, generates an active species capable of generating an electrochemical response. The sequential process, the use of enzymes, and occasionally unstable substrates limit and complicate a wide-scale application of such sensors. 

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