Agglutination Assays

Kim IK, Bunz UHF (2006) Modulating the sensory response of a conjugated polymer by proteins an agglutination assay for mercury ions in water. J Am Chem Soc 128 2818-2819... 

B. Grille , M. Gaboyard, J. Baudry, and J. Bibette A New Magnetic Agglutination Assay for Detection of the Hepatitis B Surface Antigen. Clin. Chem. 50, A152 (2004). 

Fluorescence forms the basis of a wide variety of assays, particularly those that are im-munologically based. IgG has been quantitated in bovine milk using a solid-phase agglutination assay using fluorescein isothiocyanate (FITC)-labeled rabbit anti-bovine IgG as the detection antibody (Losso et al., 1993). Such assays are both repeatable and rapid. 

Here, the antibody-antigen reactions are observed indirectly by use of labels which are attached to either the antibody or antigen. The labels can be conjugated covalently and include radioisotopes, enzymes, labeled second antibodies, fluorescent tags, luminescent molecules and phages (12, 41, 45, 48). The use of labels helps in increasing the sensitivity of the assays considerably compared to the precipitation or agglutination assays. 

The detection system employed for monitoring antibody interactions with antigens will depend on the type of IA performed. The majority are batch systems and are performed off-line. Quantification is achieved by either measuring the absorbance with spectrophotometer, excitation or emission with flourometer, radioactivity decay with a scintillation counter or visualization of direct precipitation. Typical formats used include microtiter plates or membranes or dipsticks or gels. The assay time can range from less than a minute for precipitation/agglutination assays to minutes for the dipsticks onfield assays and hours for microtiter plate-based laboratory assays (48). 

Hynes, S.O., Hirmo, S., Wadstrom, T., Moran, A.P. Differentiation of Helicobacter pylori isolates based on lectin binding of cell extracts in an agglutination assay. J Clin Microbiol 37 (1999) 1994-1998. 

Detecting and assaying lectins are made possible by the ability of lectins to agglutinate red blood cells. The specificity of lectins is in terms of the simple sugars that inhibit the agglutination assay. Some lectins, of course, recognize somewhat more complex carbohydrate structures. Table 2 gives alist of some lectins to illustrate the features of this class of proteins. 

Inactivation of the HA can also be followed by the HA titer before and after heat treatments. However, it is more difficult to accurately determine a difference of half a well in an agglutination assay, whereas half the absorbance in an ELISA assay is accurately determined. 

Other analytical methods of clinical interest that employ antibodies include cytochemical and agglutination assays. 

Laboratory findings reflect the degree of vomiting, diarrhea, or both. Transient rises in liver enzymes may be seen in 60% of children hospitalized for rotavirus diarrhea. The WBC count is usually normal. Stools rarely contain blood or leukocytes. Rotavirus detection in stool samples is possible with an enzyme immunoassay and a latex agglutination assay, both of which are available commercially. 

Gasparyan VK (2005) Hen egg immunoglobulin Y in colloidal gold agglutination assay Comparison with rabbit immunoglobulin G. J Clin Lab Anal 19 124-127... 

Carefully pour off the supernatant into a graduated cylinder avoiding the loose pellet. Note the volume and save 2 mL for protein and agglutination assays. 

Microinjection Moiding for Microfiuidics Appiications, Fig. 9 Details of micFochaimel netwmk of electroplated nickel mold insert (a) and injection molded part for agglutination assays (b) (Reprinting with permission) [18]... 

The fact that conjugated polymers are powerful tools in agglutination assays was first demonstrated by the exposure of biotinylated PPE 129 to avidin or streptavidin. Streptavidin binds to 129 and leads to agglutination and complete disappearance of the fluorescence in solution. Instead, a highly fluorescent pellet is formed. If 129 is treated with streptavidin-coated PS spheres, well-defined aggregates are formed. If similar biotinylated PPEs were treated with streptavidin, efficient energy transfer occurred when the streptavidin was labeled with Texas Red dye [127-129]. 

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