Affinity biosensors proteins

Figure 17. Schematic representation of the affinity biosensor construction and the proposed operational principle and voltammetric traces for affinity sensor signalling a biotin-functionalized surface before (A) and after (B) target protein (antibiotin IgG-HRP) association and precipitation reaction steps. Voltammetric measurements were performed in 0.1 M phosphate buffer (pH 7.0),containing 0.1 mM ferrocene methanol as a signal tracer. Inset charge coupled device (CCD) camera images of a sensor surface upon signalling reactions (Adapted from Refs. [176] [177]).

DNA or RNA aptamers - the single stranded nucleic acids with high affinity to proteins or to other low and macromolecular compounds, which is comparable with that of antibodies. These special characteristics open new routes in biosensor assembling for further practical applications, such as detection of toxicants in food or environment. 

The well-studied biotin-streptavidin system with its extremely high binding affinity (K 10 M" ) is chosen to illustrate the attributes of these LSPR-based nanoscale affinity biosensors. The biotin-streptavidin system has been studied in great detail by SPR spectroscopy and serves as an excellent model system for the LSPR nanosensor. Streptavidin, a tetrameric protein, can bind up to four biotinylated molecules (i.e. antibodies, inhibitors, nucleic acids, etc.) with minimal impact on its biological activity and, therefore, will provide a ready pathway for extending the analyte accessibility of the LSPR nanobiosensor. 

Li, Y.L, et al. (2006) Reversible immobilization of proteins with streptavidin affinity tags on a surface plasmon resonance biosensor chip. Anal Bioanal Chem. 386, 1321-6. 

Surface-bound, neutral, hydrophilic polymers such as polyethers and polysaccharides dramatically reduce protein adsorption [26-28], The passivity of these surfaces has been attributed to steric repulsion, bound water, high polymer mobility, and excluded volume effects, all of which render adsorption unfavorable. Consequently, these polymer modified surfaces have proven useful as biomaterials. Specific applications include artificial implants, intraocular and contact lenses, and catheters. Additionally, the inherent nondenaturing properties of these compounds has led to their use as effective tethers for affinity ligands, surface-bound biochemical assays, and biosensors. 

Zeder-Lutz, G., Altschuh, D., Geysen, H. M., Trifilieff, E., Sommermeyer, G., Van and Rcgenmortel, M. H. V. Monoclonal antipeptide antibodies - Affinity and kinetic rate constants measured for the peptide and the cognate protein using a biosensor technology. Molec. Immunol. 1993, 30, 145-155. 

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