Porous gold surfaces for biosensor applications

The sensitivity of optical biosensors where the detection takes place on a planar gold surface can be improved by making the surface porous. The poros ity allows a larger number of ligands per surface area resulting in larger optical shifts when interacting with specifically binding analyte molecules . The porous gold was deposited as a thin layer on a planar gold surface by electrochemical deposition in a solution of tetrachloroaurate and lead ace tate. A protein, streptavidin, was adsorbed into the formed porous layer an d the time course of the adsorption was monitored by in-situ ellipsometry. When the porous layer was 500 nm in thickness a six-fold increase of the el lipsometric response was obtained compared with a planar gold surface. The dependency of porosity and layer thickness was explained with a mathematica l model of the gold/porous gold/protein/solution system. (C) 2000 Elsevier Science S.A. All rights reserved.