Microparticle immunoassay

Initial screening tests for the previously listed drugs are typically immunoassays (e.g., EMIT, FPIA, CEDIA, microparticle immunoassay, and RIA see Chapter 9). These assays are calibrated at established cutoff concentrations. Specimens yielding responses greater than the cutoff (threshold) value are considered positive, whereas values below the cutoff are considered negative. Cutoff values are not synonymous with assay detection limits. Instead the... 

Bouma S, Worobec S, Baker A, Dubler R, Frias E, Ginsburg S, et al. Performance of automated chemiluminescent paramagnetic microparticle immunoassays for estradiol, progesterone, and testosterone on the Abbott 1200 system. Clin Chem 1997 43 S171. 

Assay principle Radioimmunoassay (RIA) Microparticle enzyme immunoassay (MEIA)... 

Fig. 31 (A) Principle of a sandwich immunoassay using FDA particulate labels. The analyte is first immobilized by the capture antibody preadsorbed on the solid phase (a) and then exposed to antibody-coated microparticle labels (b). Every microparticle contains 108 FDA molecules. High signal amplification is achieved after solubilisation, release, and conversion of the precursor FDA into fluorescein molecules by the addition of DMSO and NaOH (c). (B) Calibration curves of IgG-FDA microcrystal labels with increasing surface coverage of detector antibody (a-d) compared with direct FITC-labeled detector antibody (e). The fluorescence signals increase with increasing IgG concentration. FDA microcrystals with a high IgG surface coverage (c,d) perform better than those with lower surface coverage (a,b). (Reprinted with permission from [189]. Copyright 2002 American Chemical Society)...

The Abbott IMx , a dedicated commercial immunoassay analyzer that employs FPIAs for small molecules, can also determine larger analytes by a fluorescence-based microparticle capture enzyme immunoassay (MEIA).(44) In this system, antibody-coated0.47- mlatexparticles are used for both sandwich and competitive assays, and alkaline phosphatase conjugates that bind to the particles cleave 4-methylumbelliferyl phosphate to generate the fluorophore. 

The availability of MIP microparticles through this synthetic method has also stimulated the development of analytical techniques that make use of them as sensing elements. Apart from competitive radioassays [30] and immunoassays [32], which were already performed with ground bulk polymers, the small, regular size of the beads prepared by dispersion/precipitation polymerisation enables their use in CEC [45, 46], scintillation proximity assays [35], fluorescent polarisation assays [47], and chemiluminescence imaging [48]. 

Holt D, Moreton M, Laamanen K, Johnston A (2005) A microparticle enzyme immunoassay to measure sirolimus. Transplant Proc 37 182-184... 

Figure 10. Proposed Adaptation of a Fluorescence Energy Transfer Immunoassay to the Microparticle Sensor Design. A mixture of two different microparticles, each containing different reagents, are entrapped physically in the polyacrylamide layer. The reagents released from the microparticles set up a competition reaction between the free and labeled antigens for the available binding sites of labeled-antibody. The immunocomplexes formed have different emission spectra, allowing quantitation of free antigen concentration.

We have measured FSH in unextracted urine on an AxSYM random-access immunoassay analyzer (Abbott laboratories, Abbott Park, IL) with a MEIA (microparticle enzyme immuno assay) reagent kit. In order to correct for dilution, creatinine was measured, and the urinary FSH was normalized for creatinine concentration. Urine and serum samples were obtained from 40 women between 32 and 55 years of age. All women were healthy, except for a benign gynecological illness for which they were admitted to our hospital. All women had normal renal function. On the day of operation, we took six serum samples from each patient, each at least an hour apart, in order to calculate the mean serum FSH concentration. During the same day, we collected an early-morning urine sample, 24-h urine sample, and a random void urine sample. 

Yang, W., Trau, D., Renneberg, R., Yu, N. T., and Caruso, F. (2001). Layer-by-Layer construction of novel biofunctional fluorescent microparticles for immunoassay applications. J. Colloid Interface Sci. 234 356-362. 

P. Sahn, P.J. Taylor, P.I. Pillans, Analytical performance of microparticle enzyme immunoassay and LC-MS-MS in the determination of sirolimus in whole blood, Clin. Chem., 45 (1999) 2278. 

STN9 Levinson, S.S., Burch, P.A., Goldman, J.O. and Forgiel, D. (1991). Microparticle enzyme immunoassay and fluorescence polarization for thyroid evaluation. Clin. Chem. 37, 943, Abstr. 161. 

STN17 Raymond, A., Evans, I., Bowen, T., Trundle, S., Benham, M., Trundle, D. and Longhurst, S. (1991). Evaluation of a microparticle enzyme immunoassay for free thyroxine. Clin. Chem. 37, 963, Abstr. 253. 

An immunophilin binding assay was developed for Siro measurement and an investigational microparticle enzyme immunoassay was used in two phase III clinical trials. Currently, there is no available automated immunoassay, although assays of this type are in development. 

Sequential Competitive Binding Microparticle Capture Immunoassay... 

Some on-site drug test devices use dye-conjugated, drug-specific antibodies in place of microparticles. Otherwise, test principles are the same as those for the microparticle capture immunoassay. Test devices in this format include AccuSign (Princeton Biomeditech Corp., Princeton, N.J.) and Syva Rapid Test (Dade Behring, Newark, Del.). 

Novotny M, Bogacz J, Peters TK, Mallas T, LaFoe M, Isom L, et al. Development of an automated random/continuous access microparticle enzyme immunoassay (MEIA) for the determination of hTSH on the Abbott AxSYM automated immunoassay system. CHn Chem 1996 42 S180. 

In addition to these electrokinetic phenomena, electrostatic interactions among the microparticles due to their induced dipole are also observable [23]. The electrostatic interaction force, Fdipoie = r Sm Q fcM E [44], can make the particles form a structure like perl chain by attractive forces in the direction of an electric field, and a crystalline structure with a regular distances among the particles by repulsive forces in the plane perpendicular to the electric field. These electrostatic attractive and repulsive interactions can interfere with the precise control of microparticles using lab-on-a-display. On the other hand, we can utilize these phenomena for several applications such as a manufacture of self-assembled micropattem structures, a study about interactions between two cells, and a bead-based immunoassay. 

GC = gas chromatography (interferences primarily with older methods) HPLC = high-pressure liquid chromatography lA = immunoassay SC = spectrochemical TLC = thin-layer chromatography EC = electrochemical EZ = enzymatic EE = flame emission MEIA = microparticle enzymatic immunoassay. 

In an in vitro study, plantain (Plantago major) extract from capsules, liquid extract, or dry leaf did not affect the results of digoxin assays when using fluorescence polarization immunoassay or microparticle enzyme immunoassay. Note that contamination of plantain with Digitalis lanata has been reported. ... 

Asian or Chinese ginseng (Panax ginseng) and Siberian ginseng (Eleu-therococcus senticosus) have both been found to interfere with some digoxin assays including fluorescence polarisation immunoassay (FPIA) and microparticle enzyme immunoassay (MEIA). ... 

Kamyshny, A. and S. Magdassi (2000). Fluorescence immunoassay based on fluorescer microparticles. Colloids and Surfaces B Biointerfaces 18(1) 13-17. 

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