The “Chemistry NAWAROS group” at BOKU University was amongst the first groups that started re-search on cellulosic aerogels as the “young, third generation” of aerogels. Basic studies aiming at the preparation of highly porous aerogels from different pulps revealed that the fragile, open-porous struc-ture of alcogels can be largely retained if supercritical carbon dioxide (scCO2) is used in the final dry-ing step. This technique was later adapted for converting shaped bacterial cellulose (BC) aquogels into ultra-lightweight aerogels that quantitatively retained shape and porosity. Cellulose phosphate (CP) aerogels were prepared for the first time via the Lyocell approach and have been tested with regard to hemocompatibility, growth and differentiation of skeletal stem cells. Based on previous work, the proposed project is intended to a) study the intriguing surface effects that distinguish bacterial cellulose aerogels from those obtained by regenerating plant cellulose from solu-tion, b) understand the distinct differences in retaining the fragile network structure during scCO2 dry-ing for the two types of aerogels, c) advance basic concepts (use of porogens, surfactants, templating, scCO2 antisolvent precipitation, chemical modification, cross-linking etc.) for tailoring the properties (porosity, aggregate microstructure, hemocompatibility, mechanical and chemical properties) of cellu-losic aerogels, d) to further develop analytical techniques for characterizing porous soft matter of such low densities (down to 5 mg cm-3), and e) to investigate the tailored cellulosic aerogels regarding their use in selected biomedical applications. The application of mechanically sufficiently stable, cellulose phosphate-based hemocompatible aero-gels with spread porosity including a sufficient percentage of macropores with diameters in the range of 50 = x = 400 μm as a novel cell scaffolding material for bone grafting is one main target of the proposed project. The envisaged work has been motivated by several recent findings: 1) cellulose phosphates can be safely processed to aerogels via the Lyocell route 2) cellulose phosphates are hemocompatible and non-toxic in cultured human osteoblasts and fibroblasts, 3) cellulose phosphorylation (moderate DS only) is a pre-requisite to biomineralization, i.e. the formation of calcium deficient hydroxyapatite (cdHap), 4) moderate calcification activates blood platelets without inducing an inflammatory response, 5) calcified cellulose phosphates support robust growth and spontaneous osteogenic differentiation of skeletal stem cells. Tailoring the properties of cellulosic aerogels for controlled release of bioactive compounds is a second main objective of the proposed work. Preliminary studies have shown that bioactive compounds can be homogenously loaded into cellulose aerogels by scCO2 antisolvent precipitation. Full retention of porosity and quantitative rewettability of BC aerogels render them promising matrices for controlled release application in wound treatment, skin care or drug dehabituation. Through a better understanding of the above-mentioned microstructural differences and hitherto puzzling surface effects it is expected that aerogels from commercial pulps can also be used in a multitude of applications (catalysis, filters, separation techniques, etc.) beyond the controlled release of bioactive compounds.