Homogeneous fluoroimmunoassays

B. Reck, K. Himmelspach, N. Opitz, and D. W. Lubbers, Possibilities and limitations of continuous thyroxine measurement in an optode using the principle of homogeneous fluoroimmunoassay, Analyst 113, 1423-1426(1988). 

All of the homogeneous fluoroimmunoassay systems suffer from the possibility of background interference from other drugs and metabolites. Enzyme labels may be inhibited by endogenous molecules, and there may be fluorescence enhancement or quenching from the same sources. This may be overcome by careful choice of assay conditions and the use of high dilutions of the biological sample. 

Among homogeneous fluoroimmunoassays based on conventional fluorimetry, substrate-labeled fluoro-immunoassay is another alternative for both hapten and protein determination using a fluorescent label. As in other homogeneous competitive immunoassays, the sensitivity is limited by the serum background fluorescence and the limited amount of tracer that can be used. 

Mathis G (1993) Rare earth cryptates and homogeneous fluoroimmunoassays with human sera. Clin Chem 39 1953-1959... 

Bailey, M. R Rocks, B. F. Riley, C. Homogeneous fluoroimmunoassay using Lucifer Yellow VS determination of albumin plasma. Ann. Clin. Biochem. 1984, 21, 59-63. 

G Barnard, F. Kohen, H. Mikola, and T. Lovgren, Measurement of estrone-3-glucuronide in urine by rapid, homogeneous time-resolved fluoroimmunoassay, Clin. Chem. 35, 555-559 (1989). 

Methods for the Detection of Antigens/Antibodies Equilibrium and kinetic inhibition assays based upon fluorescence polarization, 70, 3 fluorescence excitation transfer immunoassay (FETI), 70, 28 indirect quenching fluoroimmunoassay, 70, 60 the homogeneous substrate-labeled fluorescent immunoassay, 70, 79 fluorescence immunoassays using plane surface solid phases (FIAPS), 70, 87. 

Wang, G., J. Yuan, K. Matsumoto, et al. 2001. Homogeneous time-resolved fluoroimmunoassay of bensulfuron-methyl by using terbium fluorescence energy transfer. Talanta 55 1119-1125. 

Fig. 13. Structure of TBP-Eu3+ and principle of TRACE homogeneous time-resolved fluoroimmunoassays.

Fluoroimmunoassay These assays rely on the use of fluorescence-emitting labels. Typically, antibodies labelled with afluorophore are used, for example, fluorescein isothiocyanate. After washing, measured fluorescence relates to the amount of antigen. Another useful variant is called the homogeneous fluorescent polarization immunoassay that is commonly used to measure dmgs and analytes. 

A variety of immunoassay techniques employ changes in the fluorescent properties of molecules to measure drug concentrations. Labelling of drugs with such molecules avoids the hazards of working with radioisotopes. Fluoroimmunoassays (FIA) also offer enhanced sensitivity in comparison to enzyme immunoassays they may be homogeneous or heterogeneous. 

Hemmila, L, Malminen, O., Mikola, H., and Lovgren, T. (1988). Homogeneous Time-Resolved Fluoroimmunoassay of Thyroxine in Serum. Clin. Chem. 34 2320-2322. 

An example for a homogeneous assay system is the polarization fluoroimmunoassay (PFIA). PFIA measures the increased polarization of fluorescence when a fluorophore-labeled hapten (tracer) is bound by a specific Ab, and the decreased signal when free analyte competes... 

Keywords Fluoroimmunoassays High throughput screening Homogeneous time-resolved fluorescence Lanthanide chelates Lanthanide cryptates... 

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