Surface Plasmon Resonance imaging applied to immunosensing

The Surface Plasmon Resonance (SPR) technique is considered by many researchers as a very attractive approach for immunosensor development. By proper chemical modification of the gold surface, this technique avoids the use of a tracer material, such as a radioisotope, fluorophore, or enzyme, to identify the specific analyte, thus allowing kinetic analysis of biointeracting systems. However, the technique has found limited applications for the direct assay of complex biological samples due to the variable degree of non-specific binding that may occur along with the primary antigen-antibody reaction. This work describes a possible approach for the development of a new class of SPR based assays where non-specific binding effects could be minimised The principle relies on selective UV inactivation of a gold surface coated with either antibody or antigen molecules. It is shown that under proper conditions it is possible to synthesize a surface with a predefined two-dimensional variation of immunoactivity. Following exposure to a positive sample, image contrast under SPR illumination of the immunoactivated surface would be indicative of a positive reaction The degree of SPR image contrast can be quantified and is a measure of the analyte concentration in solution. The approach minimises non-specific binding effects, and the principle can be extended for the development of immunoassays for large scale testing of complex biological samples.