Immunosensors automation

Immunosensors promise to become principal players ia chemical, diagnostic, and environmental analyses by the latter 1990s. Given the practical limits of immunosensors (low ppb or ng/mL to mid-pptr or pg/mL) and their portabiUty, the primary appHcation is expected to be as rapid screening devices ia noncentralized clinical laboratories, ia iatensive care faciUties, and as bedside monitors, ia physicians offices, and ia environmental and iadustrial settings (49—52). Industrial appHcations for immunosensors will also include use as the basis for automated on-line or flow-injection analysis systems to analyze and control pharmaceutical, food, and chemical processing lines (53). Immunosensors are not expected to replace laboratory-based immunoassays, but to open up new appHcations for immunoassay-based technology. 

Enzyme immunosensors are used in flow injection systems and Hquid chromatography to provide automated on-line analyses (71—73). These systems are capable of continuously executing the steps involved in the immunoassays, including the binding reactions, washing, and the enzyme reaction, in about 10 minutes. 

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. 

The presented examples of recent achievements in immunosensor development show the tremendous progress in this field. Detection limits lower continuously, miniaturized setups by keeping the possibility of automated production progressed, and procedures for detection are constantly simplified. Direct immobilization of the receptor antibody by photochemical reactions enables the production of ready to use immunosensors in few steps. With photovoltaic components, time consuming and expensive labeling procedures of the analyte can be avoided. 

Tschmelak, J., G. Proll, and G. Gauglitz. 2004. Verification of performance with the automated direct optical TIRF immunosensor (River Analyser) in single and multi-analyte assays with real water samples. Biosens. Bioelectron. 20 743-752. 

Gonzalez-Martinez, M.A., S. Morais, R. Puchades, et al. 1997. Development of an automated controlled-pore glass flow-through immunosensor for carbaryl. Anal. Chim. Acta 347 199-205. 

Antibody-based, fully automated immunosensors for small molecules have been used to detect explosives (see Refs. [11,12]) and biological warfare agents (see Refs. [13,14]), and can be used to analyse drinking water and extracts at hazardous waste sites (for examples, see Refs. [15-17]). In the following section, we will discuss how the addition of electrochemical detection has broadened the capabilities of such devices. 

Abdel-Hamid et al. [122] used a flow-injection amperometric immunofll-tration assay system for the rapid detection of total E. coli and Salmonella. Disposable porous nylon membranes served as a support for the immobilization of anti- ]. coli or anti-Salmonella antibodies. The assay system consists of a flow-injection system, a disposable filter-membrane, and an amperometric sensor. A sandwich immunoassay specifically and directly detected 50 cells ml total E. coli or 50 cells ml Salmonella. The immunosensor can be used as a highly sensitive and automated bioanalytical device for the rapid quantitative detection of bacteria in food and water. 

Insulin-Uke growdi factor-1 (IGF-1) Automated SPR-based immunosensor Ipgl-i milk - [152]... 

Marquette C. A., Coulet P. R., and Blum L. J., Semi-automated membrane based chemiluminescent immunosensor for flow injection analysis of okadaic acid in mussels. Anal. Chim. Acta., 398, 173-182, 1999. 

The majority of conventional immunosensors uses the 96-well microtitre plate format, which is somewhat cumbersome for use in automated operation, and... 

Portability, time of analysis and automation are important issues for environmental sensors. Collection and transportation of samples to the laboratory adds to the cost of analysis. Solutions to these issues have been addressed in this volume in Chapters 9, 17 and 18, that report developments of a screen printed disposable electrode for organophosphate pesticides, a compact self-standing immunosensor for bacteria, and spot assay for glucose, respectively. In a recent report development of an enzyme electrode for the remote monitoring, with a very fast response time, of organophosphate pesticides was reported (23). An automated prototype immunosensor... 

Figure 19 An automated meso-scale electrochemical immunosensor system with the components (a) microbead reser-voirs, (b) rinse buffer reservoir, (c) conjugate (Ab ) reservoir, (d) enzyme substrate reservoir, (e) valves, (f) electromagnets, (g) central micro-fluidic silicone channel, (h) rotary pump.

Dominguez, R.B., Hayat, A., Sassolas, A. et al. (2012) Automated flow-through amperometric immunosensor for highly sensitive and on-line detection of okadaic acid in mussel sample. Talanta, 99, 232-237. 

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