This collaborative study with the school of pharmacy group of Navarra, Spain is part of a large EU funded FP7 project which aim is to develop new nanoparticulate drug delivery systems capable of penetrating the mucus barrier. This proposal focuses on the effects of base polymers (precursor for nanoparticle fabrication) and protolithic enzymes on the gel structure of shear-compliant and shear-resistant mucus.In this experiment, changes in mucus gel structure induced by precursor polymers and enzymes will be investigated using SANS2D and OFFSPEC (spin-echo mode). This combination of instruments will enable us to characterize the interactions in terms of polymer/polymer interaction and the effects of these interactions on the structure of the larger gel network. Information extracted from this experiment will provide the means to design potent nanoparticulate formulations.