Immunoassay clinical matrices

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. 

Assay application. At this point major differences appear between the historical use of clinical immunoassays and the potential applications of environmental and pesticide immunoassays. Most clinical assays have been applied to simple or well defined and consistent matrices such as urine or serum. In contrast, most matrices likely to be analyzed for pesticides are more complex, less well defined, and more variable. The potential for serious problems with matrix effects in the environmental field is far greater than most clinical immunoassays have encountered. The application of immunoassays to environmental analysis requires sampling strategies, cleanup procedures, and data handling fundamentally similar to those presently in use in any good analytical lab. The critical factor in the success of immunochemical technology will likely be competence... 

The ideal PK immunoassay standard curve, which is nonlinear and heteroscedastic, is derived from solutions of well-characterized macromolecules added to a relatively nonreactive sample matrix. However, rarely does one encounter an ideal situation when describing bioanalytical methodology, thus developing and validating analytical methods for macromolecules, and analyzing samples from preclinical or clinical trials must include an evaluation of these variables and possibly many others. Careful consideration must be given to the topics described in this chapter to achieve the goal of accurate and reproducible quantification of biotherapeutics necessary for pharmacokinetic analysis. 

Immunoassay plays an important role in clinical analysis. It is followed by electrometric techniques polarography and electrometric sensors (ion-selective membrane electrodes, or ISME, and biosensors). Because of the complexity of the matrix, spectrometric techniques must precede the separation technique (extraction or chromatographic techniques). The best reliability for clinical analysis is achieved by using immunoassay methods and electrochemical sensors. Because of the possibility of assaying the activity of the ions continuously and without any prior separation, electrochemical... 

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Although they depend on special evaluation techniques, immunoassays based on signal production via chemi- and bioluminescence are successful [58]. In clinical chemistry, this type of signal production has already gained acceptance. This is, however, not the case in environmental analysis because of the often uncontrolled interaction of matrix components with the luminescence-producing enzyme. 

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