Characterization of gels containing hydrophobically modified chitosan

It is well known that the system monoolein (MO) - sodium monooleate (NaO) – water shows the spontaneous formation of unilamellar vesicles in the dilute corner of its phase diagram. These vesicles, with dimensions ranging between 1000 and 8000 Å are nowadays widely investigated because of their potential use as drug carrier. On the other hand, chitosan, a polysaccharide obtained by the alkaline hydrolysis of chitin, can be chemically modified by grafting on it a large variety of molecules with hydrophobic or hydrophilic properties. In the former case it is possible to tune its hydrophobic properties, inserting aliphatic chains of different length and operating on their crowding on the chitosan backbone. The contemporary presence in acidic water of these vesicles and C12-chitosan, obtained by grafting a C12 aliphatic chain, gives rise to the formation of a gel. We think that the aliphatic chains inserted on the chitosan backbone could penetrate into the vesicular double layer of the monoolein (MO) - sodium monooleate (NaO) – water vesicles, with the formation of a system with very different characteristics with respect to those shown by the aqueous vesicles and the C12- chitosan solution. The structural characterization has been performed by means of EPR and SANS measurements allowing obtaining microscopic information about the vesicular aggregates.