Nanosponges are recently developed hyper-cross-linked cyclodextrin polymers nanostructured to form 3-dimensional networks; they are obtained by reacting cyclodextrin with a cross-linker such as carbonyldiimidazole. Nanosponges can be synthesized in neutral or acidic forms, depending in turn on the agent used as cross-linker. They are solid nanoparticles and can be prepared in crystalline form with spherical shape using an ultrasound-assisted preparation method. The average diameter of a nanosponge is below 1 mu m but fractions below 500 nm can be selected. Nanosponges can encapsulate various types of molecules by forming inclusion and non-inclusion complexes. In this study We used dexamethasone as model molecule; up to 35% could be incorporated. Nanosponges could be used to increase aqueous solubility of poorly water-soluble drugs, to remove pollutants from contaminated water, or as nanocarriers for biomedical applications. (C) Koninklijke Brill NV, Leiden, 2009