Flow injection immunoassay system

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. 

H. Ishida, M. Maeda, and A. Tsuji, Enzyme Immunoassay of a-Fetoprotein Based on Chemiluminescence Reaction Using a Flow Injection Analysis System [in Japanese]. Rinsho Kagaku, 13 (1984) 129. 

In this study two different flow-injection immunoassays are presented as well as the flexible automation system CAFCA (Computer Assisted Flow Control Analysis), which has been used for their control, uptake measurement, evaluation and visualization. Both immunoassays (a heterogeneous and a homogeneous assay) are based on the principles of flow-injection analysis and were developed for reliable, fast monitoring of relevant proteins in animal cell cultivation processes. Off-line applications of measurements of medium samples as well as online application during a mammalian cell cultivation are presented. All results are compared to results obtained with ELISA (Enzyme Linked Immunosorbend Assay). The requirements of the automation of flow-injection immunoassays with respect to their flexible control are discussed. 

New immunoassay concepts were described in which immobilized affinity ligands are used in unique flow-through systems (flow-injection immunoassay, FIIA). These systems are exclusively heterogeneous. Both immobilization of a specific antibody or a hapten on the solid support is possible. In most cases the scheme of the assay used is based on a sequential competitive enzyme immu-noas.say procedure [66], [67],... 

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. 

As a process analytical solution, these extrinsic reactive approaches necessitate an extrinsic optode (see later discussion), an on-line sample conditioning system or an at-Une solution such as a flow injection analysis (FIA) system or other autonomous solutions. Reaction kinetics, post analysis cleanup such as rejuvenating a substrate (optode, immobilized based immunoassays, etc.) among other complexities are additional considerations for these types real-time analysis methods. ... 

The use of capillaries to run immunoassay reactions was presented in the 1980s and 1990s by Halsall group [8] for the detection of atrazine. The system was based on a flow injection analysis protocol where different solutions (sample, conjugate) were injected and reacted in the capillary itself the affinity-captured enzyme conjugate then reacted with a substrate solution injected in the capillary prior to detection. The reacted substrate solution was then pushed towards an electrode for amperometric detection. The authors showed that the incubation time reached equilibrium after about 20 min, but they worked with a capillary of 360 pm diameter. In order to really reduce the incubation time below lmin, we developed disposable polymer chips with an internal diameter of 40 pm (almost one order of magnitude smaller than... 

Cheng, S.B., Skinner, C.D., Harrison, D.J., Integrated serial dilution on a microchip for immunoassay sample treatment and flow injection analysis. Micro Total Analysis Systems 98, Proceedings pTAS 98 Workshop, Banff, Canada, 13-16 Oct. 1998, 157-160. 

Silzel, J.W. Cercek, B. Dodson, C. Tsay, T. Obremski, R.J. Mass-sensing, multianalyte microarray immunoassay with imaging detection. Clin. Chem. 1998,44 (9), 2036-2043. Pollema, C.H. Ruzicka, J. Flow injection renewable surface immunoassay a new approach to immunoanalysis with fluorescence detection. Anal. Chem. 1994, 66(11), 1825-1831. Sole, S. Alegret, S. Cespedes, F. Fabregas, E. Diez-Caballero, T. Flow injection immunoanalysis based on a magnetoimmunosensor system. Anal Chem. 1998, 70 (8), 1462-1467. 

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. 

DA Palmer, et al. Flow injection electrochemical enzyme immunoassay for theophylline using a protein-A immunoreactor and /t-aminophenyl phosphate// -aminophenol as the detection system. Analyst 117 1679, 1992. 

Immunoassay is a very sensitive technique that can be applied in environmental chemistry and food chemistry, and is very often used in clinical chemistry. By inclusion of immunoassay in the flow injection system, precise control of reaction times can be achieved compatibility with any heterogeneous or homogeneous format, and detector, good accuracy, and reproducibility are assured the analysis time decreases and the analytical process becomes more flexible.243... 

The future use of coated piezoelectric devices as immunochemical sensors, even directly in the liquid phase, is very promising and could be considered a very competitive alternative to other types of immunoassay. Only this technique and that of surface plasmon resonance provide labelless methods for the direct study of antigen-antibody reactions, and their analytical possibilities. The devices can be easily automated or combined with flow injection systems, extending their capability of continuous and repeated assays. This raises an exciting possibility of using crystal arrays to assay for different analytes in complex samples with an on-line display of the results. 

M. Maeda and A. Tsuji, Enzymatic Immunoassay of a-Fetoprotein, Insulin and 17-a-Hydroxyprogesterone Based on Chemiluminescence in a Flow-Injection System. Anal. Chim. Acta, 167 (1985) 231. 

ABEI produces ECL when oxidized at 1.0 V versus Ag/AgCl in alkaline aqueous solution. In contrast to luminol, ABEI labels do not markedly lose their CL efficiency when conjugated with proteins. ECL immunoassays with a flow injection analysis (FIA) system using ABEl-isothiocyanate as a label were proposed, which have a better performance than either single-radial immunodiffusion or nephelometric immunoassays. ABEI can also be used as an oligonucleotide marker to label a DNA probe. The intensity of the ABEI ECL was linearly related to the concentration of the complementary sequence in the range 96-96 nM, and the detection limit was down to 30 pM. 

A variation of flow-injection analysis, sequential-injection analysis (SIA), has recently been introduced. Contrary to flow-injection analysis, where the components are injected into a continuous flowing stream, in SIA injections are done sequentially directly into the reactor/detector system. The instrumental setup usually consists of a syringe pump in combination with an electronically controlled multi-port valve. SIA systems have been shown to be more flexible regarding injection volumes and injection times. This technology has been demonstrated to be very efficient for carrying out immunoassays. Both fluorescence and chemiluminescence immunoassays have already been carried out with this technique. 

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