SERS detection of thrombin by protein recognition using functionalized gold nanoparticles.

We present a method based on surface-enhanced Raman spectroscopy and exploiting a protein-protein recognition process able to detect thrombin at subpicomolar concentrations. Gold nanoparticles (NPs) were capped with a bifunctional molecule capable of forming a covalent link with the aromatic residues of the protein moiety. The typical vibrations of the diazo bond established between the bifunctional molecule and the target protein are found to be selectively enhanced by the conjugated gold NPs, and therefore constitutes the Raman marker. After the interaction of functionalized NPs with antithrombin as a sensitive recognition element, immobilized on a capture substrate, we have detected thrombin at a concentration of about 10(-13) M.