The sensitivity of optical biosensors where the detection takes place on a planar gold surface can be improved by making the surface porous. The porosity 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 acetate. A protein, streptavidin, was adsorbed into the formed porous layer and 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 ellipsometric response was obtained compared with a planar gold surface. The dependency of porosity and layer thickness was explained with a mathematical model of the gold/porous gold/protein/solution system. Copyright (C) 2000 Elsevier Science S.A.The sensitivity of optical biosensors where the detection takes place on a planar gold surface can be improved by making the surface porous. The porosity 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 acetate. A protein, streptavidin, was adsorbed into the formed porous layer and 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 ellipsometric response was obtained compared with a planar gold surface. The dependency of porosity and layer thickness was explained with a mathematical model of the gold/porous gold/protein/solution system.

A quartz crystal microbalance can be used as a biosensor if biological receptor molecules (ligands) are attached to the crystal. To improve the sensitivity, the surface area of the gold electrodes on the crystal was increased by rendering the electrodes porous. This increased the response up to a factor of 3. A protein model system with human anti-myoglobin as ligand and sheep skeletal myoglobin at different concentrations as analyte was used. The quartz crystal was mounted in a flow-cell, where immobilisation, binding and regeneration of the surface were carried out. The kinetics of the model system was monitored under various experimental conditions.

In this paper we report on the fabrication of an affinity biochip with a matrix of 900 targets for detection with imaging ellipsometry. Two methods of fabrication of chips are shown: one based on wet etching of a silicon surface and the other on the preparation of so-called tension wells on the silicon surface. The dispensing of reagents and ligands was performed using a pipetting robot equipped with a micro-capillary, a syringe pump and micro-stepping motors. Measurements were performed on the chips in real time with carbohydrate model substances selected for six common lectins. Affinity binding was shown for three of the tested model substances.