Sensitivity studies for specific binding reactions using the biotin/streptavidin system by evanescent optical methods

Biosensing by optical waveguide spectroscopy based on localized surface plasmon resonance of gold nanoparticles used as a probe or as a label

“…Granular features with an apparent height of 2-3 nm, which is comparable to the length of Sulfo-NHS-LC-LC-Biotin, were observed for biotinylated OWG surface (Fig. 4b), and projected features measuring 4-5 nm in height, which is approximately equal to the size of a streptavidin molecule [47,48], appeared after the biotin-streptavidin binding reaction (Fig. 4c).…”

“…The amount of streptavidin molecules bound to biotinylated OWG was also examined by fluorescence measurement for a specimen treated with a solution containing 1 lg/mL of FITC-conjugated streptavidin. As a result, the number of immobilized streptavidin molecules was estimated to be equal to 3.24 Â 10 10 molecules/cm 2 , which corresponds to the surface coverage of 0.635 % calculated by assuming a sphere of 5 nm in diameter for an individual streptavidin molecule [47,48]. This coverage seems quite low, but streptavidin molecules do not adsorb physically in a multilayer fashion.…”

Immobilization of streptavidin onto biotin-functionalized Langmuir–Schaefer binary monolayers chemisorbed on gold

“…The very high specific binding affinity (K a ∼ 10 13 -10 15 M −1 ) [11] between streptavidin and its ligand biotin makes this system a very attractive model for studying surface recognition processes. Previous studies using biotinylated lipids at the air-liquid and solid-liquid interfaces have demonstrated the specific and rapid binding of streptavidin to biotin [12][13][14][15][16][17][18]. Streptavidin has a well-known ability to assemble into optically anisotropic two-dimensional (2D) crystals at these interfaces [18][19][20][21] The prerequisite for the 2D protein crystallization is the mobility (lateral diffusion) of proteins at the interface.…”

Surface plasmon resonance immuno assays – A perspective

“…Other approaches for a more efficient immobilisation of the antibodies at the surface have focussed on the specific modification of the antibody outside the SPR environment. A clear example of such approach is the biotinylation of antibodies that later on are flown across an avidin CM5 sensor surface [26]. In this approach it is wise to remember that the biotinylation still incorporates an element of randomness to the approach, that it is performed outside the SPR monitoring system, and usually requires $100-fold more antibody.…”