ABSTRACT
SPR biosensors are used to measure interactions in real
time between an analyte in solution and a biomolecular
recognition element (ligand) immobilized on the SPR sen-
sor surface. Typical ligands include antibodies, enzymes,
hormones receptors, or DNA strands. The sensor chip
consists of a glass slide coated with a thin gold film
which is usually covered with a flexible polymer to
which biomolecules may be covalently linked using a
well-defined chemistry (Fig. 1). Carboxymethyl-modified
dextran has been widely used among the numerous
polymers available. Immobilization of the ligand molecule
on the polymer can be achieved by adsorption, cross-
linking, covalent bonding, entrapment, or encapsulation.
SPR optical sensors allow transfer of the energy carried by
photons of polarized incident light to electrons in the metal
covering sensor surface. The energy transfer in such a
sensor chip results in creation of a plasmon, a group of
free-oscillating electrons in the metal thin surface.
Modification of the plasmon resonance is achieved by
changing of the physical properties of the aqueous layer
close to the biosensor surface when the target analyte
interacts with its partner (ligand) immobilized on the
