Immunoassay sol-particle

Sol particle immunoassay was developed by Leuvering et al. of the Organon group (L6). They used inorganic (metal) colloidal particles as a label... 

The first immunoassay performed in a capillary driven system was reported in 1978 [67]. Based on this technique, the commonly known over-the-counter pregnancy test was introduced into the market in the middle of the 80 s. Today, this microfluidic platform is commonly designated as a lateral flow test (LAT) [14]. Other terms are test strip , immunochromatographic strip , immunocapillary tests or sol particle immunoassay (SPIA) [68]. Astonishingly, hardly any publications from a microfluidic point of view or in terns of material classification exist, and apparently many company secrets are kept unpublished [69]. 

Figure 20 shows a calibration curve for a sufficiently rapid and technically simple quantitative sol-particle immunoassay (SPIA [18]). The assay is based on biospecific aggregation of 15-nm gold conjugates to Protein A due to interaction with hIgG molecules. We have found a direct correlation between the amount of the second added protein initiating aggregation and the spectral position of the extinction maximum. 

Enzyme immunoassays, in a card-test format, are also used for screening carcasses by testing of urine for specific antimicrobial residues such as sulfadimidine and chloramphenicol. The sol particle immunoassay uses adsorption of specific antibodies to dyed colloidal particles (e.g., carbon) as a mechanism for making directly visible the presence of residues (i.e., antigen) in the sample. A lateral flow membrane device is used to identify residue-positive samples through the absence of color formation at the test capture zone (Figure 5). 

Sol-particle immunoassay (SPIA) Metal atoms (i) Visible response (ii) Colorimetry Simple labelling (30)... 

Other methods with potential application in sensor development include certain enzyme immunoassays and sol-particle immunoassay. The enzyme methods that are potentially useful are those where the detection of the enzyme is carried out with a substrate that produces colour that may be determined colorimetrically, or a substrate that produces fluorescence. 

The method of sol-particle immunoassay uses colloidal metal particles as the label. Typically these labels have been colloidal gold and colloidal silver. Detection in this type of assay is carried out visually, colorimetrically or by atomic absorption spectroscopy with electrothermal atomization. The colorimetric methods obviously offer potential in sensor development and the detection limits in the pmol 1 range are useful. 

Diagnostic sol particle immunoassay microscopy labelling reagents Chemical and biosensing Nanoscale electronics Homogeneous catalysis High-order nonlinear optical susceptibility... 

J. H. W. Leuvering, B. C. Goverde, P. Thai and A. Schuurs. A Homogeneous Sol Particle Immunoassay for Human Chorionic- Gonadotropin Using Monoclonal-Antibodies. Journal of Immunological Methods 60 (1-2), 9-23 (1983). 

A typical immunoassay format in a flow-through device has an antibody covalently coupled to the surface of a porous matrix. When the patient sample is added to the matrix, the analyte of interest binds to the antibody. Addition of a second labeled antibody forms a sandwich and traps the label at the position of the first antibody. If the label is gold sol particles or colored latex, the label is directly visualized or quantified by reflectance spectrophotometry in a separate reader, Another important feature of this type of technology is the incorporation of a built-in quality monitor that indicates positive if all the reagents have been stored and the device operated correctly. In all these different formats,... 

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