These can both disrupt antigen/antibody Volasertib clinical binding and deposit high mass on the surface, potentially distorting immunoassay signals.This review will examine the general principles and parameters of small molecule immunoassays and how others have designed their immunosensor systems using SPR transduction. Specific classes of target small molecule antigens of particular interest are then investigated, namely steroids, toxins and food components, drugs and explosive residues, before some general comments are made on possible future directions in small molecule SPR immunosensor research. A summary of some SPR immunoassays of small molecules is given in Table 1.Table 1.A summary of some SPR immunoassays of small molecules, giving the target analyte, the sample medium, reported limit of detection (LOD) and method of enhancement (if used).

Note that researchers often use different methods for calculating LOD.2.?General Principles and Immunosensor Assay FormatsWhen developing small molecule immunobiosensors for use with SPR transduction, one must first consider the structure and assembly of the sensing surface. The small molecule antigen can be immobilized to the gold surface Inhibitors,Modulators,Libraries via the commonly used carboxymethyl dextran polymer layers. These layers are functionalized with carboxylic acid groups that allow covalent attachment of antigen or antigen derivatives containing an amino group through the formation of an amide bond. Steroid hormones have been conjugated using this technique in a convenient in-situ flow-through immobilization technique within the biosensor by attaching a linker at a point on the antigen distant from existing functional Inhibitors,Modulators,Libraries groups [4].

The resulting functionalized surfaces can withstand up to more Inhibitors,Modulators,Libraries than 1,100 binding and regeneration cycles [4]. They use hydrophilic oligoethylene glycol (OEG) linkers which can project the antigen into Inhibitors,Modulators,Libraries the aqueous fluid stream and allow for optimal antibody binding [4,7]. Binding is also optimized through careful selection of the position of conjugation on the steroid so that linkers are attached distant from existing functional groups [7].Another key consideration is the method of signal generation. With antigen-immobilized formats, the primary antibody can provide the signal but studies using steroid GSK-3 antigens have also employed secondary antibodies to further enhance the signal strength with enhancements of 6�C8 times the primary antibody binding signal [4] (Figure 3).

In addition to this enhancement approach, gold nanoparticles have been used to further enhance signal by adding more b
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