Capillary electrophoretic immunoassay

W Thormann, M Lanz, J Caslavska, P Siegenthaler, R Portmann. Screening for urinary methadone by capillary electrophoretic immunoassays and confirmation by capillary electrophoresis mass spectrometry. Electrophoresis 19 57-65, 1998. 

J Caslavska, D Allemann, W Thormann. Analysis of urinary drugs of abuse by a multianalyte capillary electrophoretic immunoassay. J Chromatogr A 838 197-211, 1999. 

Taylor, J., Picelli, G., Harrison, D.J., An evaluation of the detection limits possible for competitive capillary electrophoretic immunoassays. Electrophoresis 2001, 22, 3699-3708. 

Babu CV, Chung BC, Lho DS, Yoo YS. Capillary electrophoretic competitive immunoassay with laser-induced fluorescence detection for methionine-enkephalin. J Chromatogr A 2006 1111 133-8. Jackman R, Everest DJ, Schmerr MJ, Khawaja M, Keep P, Docherty J. Evaluation of a precUnical blood test for scrapie in sheep using immunocapiUary electrophoresis. J AOAC Int 2006 89 720-7. 

Wuilloud, R.G. et al.. The potential of inductively coupled plasma-mass spectrometric detection for capillary electrophoretic analysis of pesticides. Electrophoresis, 26,1598, 2005. Morozova, V.S., Levashova, A.I., and Eremin, S.A., Determination of pesticides by enzyme immunoassay, /. Anal. Chem., 60, 202, 2005. 

CAE employing antibodies or antibody-related substances is currently referred to as immunoaf-hnity capillary electrophoresis (lACE), and is emerging as a powerful tool for the identification and characterization of biomolecules found in low abundance in complex matrices that can be used as biomarkers, which are essential for pharmaceutical and clinical research [166]. Besides the heterogeneous mode utilizing immobilized antibodies as described above, lACE can be performed in homogeneous format where both the analyte and the antibody are in a liquid phase. Two different approaches are available competitive and noncompetitive immunoassay. The noncompetitive immunoassay is performed by incubating the sample with a known excess of a labeled antibody prior to the separation by CE. The labeled antibodies that are bound to the analyte (the immuno-complex) are then separated from the nonbound labeled antibody on the basis of their different electrophoretic mobility. The quantification of the analyte is then performed on the basis of the peak area of the nonbonded antibody. 

One of the earliest efforts of qualitative measurement of a protein (human serum albumin) in a microchip-based device was based on bead agglutination in a microchamber (approximately lOjaL). Subsequently, several quantitative immunoassays have been performed using microchip electrophoretic systems that permit separation and quantitation of free- and bound-labeled antigens in competitive assays (see Chapter 5). Most are carried out in channels micro-machined into fused silica substrates. Early work on quantitative assays achieved measurement of cortisol in serum.The assay used cortisol labeled with fluorescein and an argon laser detector at 488 nm and required only 80 pL of a 40x dilution of serum as the sample. Other capillary electrophoresis-based assays for a variety of antibodies have also been developed that include immunoglobulins (IgG, IgA, and IgM), antibovine serum albumin, and antiestradiol. ... 

Electrophoretic analysis of proteins was one of the first methods transitioned to capillaries in clinical laboratories—this is highlighted in Chapter 2 by Hempe. Unfortunately, protein analysis has not made the same transition to microchips. This is due to the difficulties in implementing a ultraviolet (UV) absorbance method on microchips, the method normally utilized for proteins detection on CE. A number of fluorescent methods have been employed both for standard separations as well as for immunoassay analyses that utilize separations. Two-dimensional separations have also been performed on microchips,as reviewed in Chapter 33 by Lee, and these might have clinical significance at some point in the future. 

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