Immunosensors nonspecific adsorption

A major disadvantage is that the direct sensor detection cannot distinguish between the sensor response to the specific analyte binding from the response to a possible nonspecific adsorption of other compounds. The nonspecific fouling from blood or blood serum seems to be one of the main barriers for practical application of immunosensors in medical diagnostics. 

The main problems that require more research and optimization of immunosensor design are nonspecific adsorption of coexisting substances, further involvement of genetic engineering in production of novel antibodies, and search for the same purpose of smaller proteins with antibody properties (e.g., anticalins). 

Fig. 9. Reflectometric immunosensor. (a) Construction scheme (b) dependence of the measuring signal on layer thickness upon reaction between adsorbed immunoglobulin G (IgG) and anti-IgG. (Gelatin is added to suppress nonspecific adsorption on the free silicon surface.) (Redrawn from Welin et al., 1984).

The same authors developed a much more robust label-free impedimetric immunosensor, based on the same IDpE arrays conveniently derivatized through covalent procedures to ensure reliability and to prevent nonspecific adsorption [42]. Atrazine-BSA was covalently immobilized on the surface of the IDpEs previously activated with (3-glycidoxypropyl)trimethoxysilane via the side chain amino groups of lysines or arginines with the epoxy groups on the device surface. Before, the gold electrodes were blocked... 

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