Porous silicon layers with a one-dimensional lateral gradient in pore size are prepared by electrochemical etching and characterized by spectroscopic ellipsometry in the visible to near-infrared region. The ellipsometer is equipped with a micro-spot option giving a lateral resolution of approximately 100 μm. By matching multiple-layer-model calculations to the laterally-resolved variable angle of incidence spectroscopic ellipsometry data, the thickness variation along the gradient as well as the in-depth porosity profile is mapped. Upon exposure to a protein solution, protein adsorption occurs on top of the porous silicon layer. At the high-porosity region of the gradient also penetration of protein molecules into the porous layer takes place. Ellipsometry data are recorded after protein exposure and variations of protein adsorption along the porous silicon gradient is modeled as well as the in-depth profile of protein penetration.

One common problem when putting something inside the body is a fast response from the body defending it from the intruder. Here the researchers are struggling with finding biocompatible materials, which act in a predicted and non-harmful way. In the drug delivery area the idea is to find a good solution of giving a patient its daily medication in a convenient way. The ideal would be to have a unit that could deliver the drug automatically when needed in the dose needed. By high trough putscreening, finding of potential drugs or molecules related to diseases takes much less time. Here a large surface area to which the substance of interest can attach is preferable to be able to use as little analyte as possible and still have a high sensitivity.

To be able to realize the applications mentioned above a basic understanding of how proteins interact with surfaces must be developed.The aim of this thesis has been to investigate the adsorption of proteins into and on porous silicon.

Porous silicon was chosen as the porous material to work with because porous silicon has been shown to be bioactive and produce hydroxyapatite upon incubation in simulated body fluid. It is also a material with large surface area, which is convenient to use in the chiparea as well as in drug delivery.

Gradients in pore size and porous layer thickness were etched in silicon and used in protein adsorption experiments together with homogeneous porous layers. The adsorbed amounts of protein were determined at different pH, different protein concentrations as well as for porous silicon prepared with different etching conditions.

The results show that the morphology of the porous layer influence the protein uptake, indicating that more protein is found for larger pore sizes as well as for thicker porous layers. A minimum pore size of 5.5 nm in radius was found for albumin penetration. An increase in protein concentration up to 10 mg/ml albumin resulted in more proteins loaded into the porous silicon layer. The refractive index spectrum of carbonic anhydrase and location of the protein in porous silicon were also determined.