Antibody analyte interaction, immunoassay method specificity

There is a continuing demand for fast and simple analytical methods for the determination of many clinical, biochemical and environmental analytes. In this respect, immunoassays and immunosensors that rely on antibody-antigen interactions provide a promising means of analysis owing to their specificity and sensitivity. High specificity... 

Another application that microfiuidic bioreactors have been used for is in immunoassays. These are based on antigen-antibody interactions and are a powerful technique because these interactions have very high selectivity and are extremely sensitive. Typically, an immunoassay is performed by immobilizing one of the binding partners placed within the system. The corresponding pair is then incubated within the device. The advantage of this approach is the ability to very specifically concentrate molecules on the active surface of the device. This enables enhanced reaction efficiencies, simplified analytical procedures, and reduced consumption of reagents. These immunoassay methods are often coupled with separation methods such as capillary electrophoresis in order to further increase the utility of the method [10]. 

Immunological methods make use of antibodies as analytical tool for detecting a plethora of clinical, environmental, and food-relevant analytes. The special features that had made immunoassay widely increased in the last decades are the highly sensitivity and specificity of the antibody-antigen interaction. Although enzyme-linked immunosorbent assay (ELISA), currently performed in microtiter plates is the most common technique, a variety of assay types can be performed depending of the analytes or samples. 

The model immunoassay is the enzyme-linked immunosorbent assay (ELISA) in which a non-specific capture antibody is bound to a surface, such as a multi-well plate or small tube [13]. In the basic form of ELISA, a second antibody tagged with an enzyme interacts specifically with the analyte. The enzyme assay produces a colored product that is read with a spectrophotometer. There are many variations on the basic immunoassay format that serve to increase sensitivity, specificity, linear range, and speed. Many commercial instruments have been developed to take advantage of various technologies for reporter molecules. The immunoassay may be coupled to an electronic sensor and transducer, such as a surface acoustical wave (SAW) sensor. Electrochemiluminescence (ECL) is a method in which the detector antibody is tagged with a ruthenium-containing chelate [13-15]. When the tag is... 

Due to the high specificity and sensitivity of immunoassays, there are bioanalytical methods for the measurement of an analyte of interest, with little or without preconcentration or purification of the samples. The principle behind immunoassays is based on an interaction between an antibody and a corresponding antigen, and the detection of the specific interaction using radiolabels (247), enzyme, fluorescent and luminescent compounds (178, 179,181,183), electroactive markers (177,180, 228, 248), or nanomaterials (249-251). 

Immunoassays are an analytical technique based on the highly specific interaction between an antibody and an antigen. Due to their ability to measure trace amounts of analyte in complex matrices, immunoassays are widely used in clinical, pharmaceutical, and environmental chemistry. Person and Yalow were the first to use antibodies as an analytical tool, reporting picogram detection of insulin [131]. Immunoassays are the primary method used in diagnosing diseases such as acquired immunodeficiency syndrome (AIDS) [132], cysticerocosis [133], and schistosomiasis [134, 135]. Due to their widespread use, growth in the field has been tremendous over the past decades. 

When the concentration of the analyte in the biological solution is too lowfor detection using spectrophotometry, more sensitive methods such as immunoassays are used for the measurement. Immunoassays utilize antibodies developed against the analyte of interest. Since the antigen and the antibody have a very specific interaction and has very high affinity toward each other, the resulting detection system also has a very high sensitivity. A specific example, the enzyme linked immunosorbent assay (ELISA), will be described here. 

The specific interaction antigens (analytes) and antibodies (reagents) used for analytical methods generally known as immunoassays are reflected quantitatively by changes in the activity or signal yielded by an appropriate label. The inception of HA in the immunological field results in faster and more reproducible assays. Examples are given in Table 7. 

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