Human serum albumin was adsorbed into porous silicon layers with thickness up to 3 pm and with different mean pore radius in the range 4.5-10 nm. The adsorbed amount of protein was quantified by I-125 radioactive labeling techniques and ellipsometry. The results show that albumin penetrated into the pores when the mean pore radius was larger than 5.5 nm, but could not totally occupy the available surface area when the layer thickness was larger than I mum. Loading of albumin both into porous layers and onto plane silicon as a function of albumin concentration was also investigated. These measurements show that loading of protein increased with protein concentration at least up to 10 mg/ml for porous silicon and up to I mg/ml for plane silicon. The maximum deposition into the type of porous layers used here was 28 mug/cm(2), compared to 0.36 mug/cm(2) for plane silicon. (C) 2003 Elsevier Inc. All rights reserved.