Surface plasmon resonance optical detection systems

Biosensors offer a unique solution to vitamin B12 analysis in terms of specificity and time-saving commercial biosensors are available in several forms such as autoanalysers, manual laboratory instruments and portable (handheld) devices. One biosensor system, Biacore Q, is based on optical detection— the surface plasmon resonance (SPR) technique for vitamin Bi2 analysis. 

Immunosensors have been developed commercially mostly for medical purposes but would appear to have considerable potential for food analysis. The Pharmacia company has developed an optical biosensor, which is a fully automated continuous-flow system which exploits the phenomenon of surface plasmon resonance (SPR) to detect and measure biomolecular interactions. The technique has been validated for determination of folic acid and biotin in fortified foods (Indyk, 2000 Bostrom and Lindeberg, 2000), and more recently for vitamin Bi2. This type of technique has great potential for application to a wide range of food additives but its advance will be linked to the availability of specific antibodies or other receptors for the various additives. It should be possible to analyse a whole range of additives by multi-channel continuous flow systems with further miniaturisation. 

Direct detection biosensors utilize direct measurement of the biological interaction. Such detectors typically measure physical changes (e.g., changes in optical, mechanical, or electrical properties) induced by the biological interaction, and they do not require labeling (i.e., label free) for detection. Direct biosensors can also be used in an indirect mode, typically to increase their sensitivity. Direct detection systems include optical-based systems (most common being surface plasmon resonance) and mechanical systems such as quartz crystal resonators. 

Presented experimental results suggest that application of herbicide-binding protein in sensor technology has a high potential. Several detection systems were tested in combination with D1 protein electrochemical (amperometry and cyclic voltammetry), optical (surface plasmon resonance and ellipsometty) and assays (ELISA and D1 protein- containing liposomes and DELFIA fluori-metric assay). The main mechanisms of D1 action are either on the ability of herbicides to replace the plastoquinone molecule in D1 protein and in this way change the electrochemical and optical... 

Jakubik WP, Urbanczyk MW, Kochowski S, Bodzenta J (2003) Palladium and phthalocyanine bilayer films for hydrogen detection in a surface acoustic wave sensor system. Sens Actuators B 96 321-328 Jung CC, Saaski EW, McCrae DA (1998) Fiber optic hydrogen sensor. In Jung CC, Udd E (eds) Proceedings of the SPIE, Fourth Pacific Northwest Fiber Optic Sensor Workshop, vol 3489, pp 9-15 Kashyap R, Nemova G (2009) Surface plasmon resonance-based fiber and planar waveguide sensors. J Sensors 2009 645162... 

Various physical transducers can be used to detect interaction of the immobilized DNA probe with the analyte. Commonly used detection systems include optical (MarvUc, 1997 Jordan, 1997 Lee, 2001), electrochemical (Wang, 2001 Palecek, 2001) or mass sensitive devices (Storri, 1998 Ebara, 2000). Considering the growing number of potential applications, simphcity and low cost are some of the major design parameters in both microarray and other biosensor apphcations. Therefore, increased attention has been given to relatively simple detection or sensing techniques such as fluorescence measurements. This method offers faster assays without the need for specific substrate properties such as in the mass-sensitive quartz-crystal microbalance (Storri, 1998 Ebara, 2000) or in more complex optical techniques such as surface plasmon resonance (Jordan, 1997 Lee, 2001). 

Fluorescence measurements and detection can either be made under steady-state or time-resolved conditions. Some of the commonly used measurement techniques focus on changes in optical properties such as fluorescence intensity quenching, phase fluorometry (lifetime), polarization, surface plasmon resonance (SPR), and evanescent waves. Here, we will present detector systems based for (a) fluorescence intensity quenching and (b) phase fluorometry in detail. A few example references of integrated optical sensor systems based on the various optical measurement techniques are given in Table 1 and the reader is encourage to review those papers if more details are desired. 

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