microspheres , having a size lower than 1μ and comprising a biocompatible polysaccharidic polymer , are prepared with a process comprising the precipitation of polymer induced by means of a supercritical antisolvent . these microspheres are used as vehicling agents or carriers in the preparation of pharmaceutical compositions administrable by oral , nasal , pulmonary , vaginal or rectal route . these microspheres can also be advantageously used as vehicling agent or carriers in the preparation of pharmaceutical compositions for the treatment of human diseases associated with genic defects , for the preparation of diagnostics and in the agro - alimentary industry .