Surface modification chemistry based on the electrostatic adsorption of poly-L-arginine onto alkanethiol modified gold surfaces

The reaction between the arginine's guanidino group and alpha-dicarbonyl functionalities was used to develop a novel surface modification chemistry. The first modification step consists of the electrostatic adsorption of a poly-L-arginine layer onto ionizable alkanethiol modified gold surfaces. The strongly basic character of the guanidino group of the arginine residues (pK(a) > 12) guarantees the robust attachment of the polypeptide to negatively charged gold surfaces until very high pH. By varying the pH of the solution from which poly-L-arginine is electrostatically adsorbed, it is possible to control the amount deposited. The availability of the surface guanidino groups of the poly-L-arginine layer for further derivatization with alpha-dicarbonyl reaction probes, yielding stable heterocyclic condensation adducts, is demonstrated. In addition, the reaction with the heterobifunctional reagent p-azidophenyl glyoxal (APG) provides a surface terminated with a photosensitive aryl azide group which was employed for the photochemical immobilization of proteins to the surface. The application of this surface modification chemistry to immobilize antibodies is demonstrated.