Microchip immunoassay

Figure 8 (a) Immunoassay microchip with microbeads, (b) Cross section image... 

Arenkov, P., Kukhtin, A., Gemmell, A., Voloshchuk, S., Chupeeva, V., and Mirzabekov, A. (2000). Protein microchips Use for immunoassay and enzymatic reactions. Anal. Biochem. 278, 123-131. 

Apart from immunoassays, enzyme assays can also be used to detect certain substrates in a clinical diagnostic setting. The benefits of performing enzymatic assays on microchips are the analytical power and minimal reagent use in microfluidic systems combined with the selectivity and amplification factors that come with biocatalysis. 

J. Wang, A. Ibanez, and M.P. Chatrathi, Microchip-based amperometric immunoassays using redox tracers. Electrophoresis 23, 3744—3749 (2002). 

Several successful attempts were done to transfer classical CEIA to a microchip-based format. This kind of miniaturization is a trend that can overcome the limitations of CE in high-throughput systems. On-chip CE offers both parallel analysis of samples and short separation times. Koutny et al. showed the use of an immunoassay on-chip (32). In this competitive approach fluorescein-labeled cortisol was used to detect unlabeled cortisol spiked to serum (Fig. 8). The system showed good reproducibility and robustness even in this problematic kind of sample matrix. Using serum cortisol standards calibration and quantification is possible in a working range of clinical interest. This example demonstrated that microchip electrophoretic systems are analytical devices suitable for immunological assays that can compete with common techniques. 

LB Koutny, D Schmalzing, TA Taylor, M Fuchs. Microchip electrophoretic immunoassay for serum cortisol. Anal Chem 68 18-22, 1996. 

Different immunoassays have been developed in CE microchips for detecting immunoglobulins, such as mouse IgG. Enzymatic (alkaline phosphatase) [39] or electroactive (ferrocene) [38] labelled anti-mouse... 

This chapter focuses on the approach we followed for developing a novel electrochemical sensor platform based on disposable polymer microchips with integrated microelectrodes for signal transduction. It presents the development of the so-called Immuspeed technology, which is dedicated to quantitative immunoassays with reduced time-to-results as well as sample and reagent volumes. Prior to presenting the specific characteristics of Immuspeed, the basic principles integrated in this platform are first presented and illustrated with reference to... 

As an example of microchip-based electrochemical immunoassays, we describe here the protocol established for the analysis of interleukin IB by enzyme linked immunosorbent assay (ELISA) with amperometric detection at the sub-pM level in DiagnoSwiss microfluidic chip called Immuchip . 

An interesting application of microchip CE is the analysis of serum cortisol immunoassays that have been performed off-chip prior to their injection [64]. Separation and quantitation of the free and bound labeled antigen could be achieved in less than 30 s and allowed the determination of serum cortisol in the clinical range of interest. 

Very recently, von Heeren et al. [59] have performed MECC separations with SCCE. In particular, these authors demonstrated the application of microchip MECC to biologically relevant samples such as labeled urine. A competitive immunoassay for monitoring patient serum levels of theophylline was carried... 

Research on microchip protein analysis has been very active for cellular protein functional assay, clinical diagnostics, and proteomics studies. Once again, the microfluidic technology plays an important role in protein assays. Immunoassay, protein separation, and enzymatic assay will be described in detail in subsequent sections. 

Chiem, N., Harrison, D.J., Microchip-based capillary electrophoresis for immunoassays analysis of monoclonal antibodies and theophylline. Anal. Chem. 1997, 69, 373-378. 

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. 

Wang, J., Ibanez, A., Chatrathi, M.P., Escarpa, A., Electrochemical enzyme immunoassays on microchip platforms. Anal. Chem. 2001, 73, 5323-5327. 

Sato, K., Tokeshi, M., Kimura, H., Kitamori, T., Determination of carcinoembry-onic antigen in human sera by integrated bead-bed immunoassay in a microchip for cancer diagnosis. Anal. Chem. 2001, 73(6), 1213-1218. 

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