Disclosed herein is an improved process for the preparation of nanostructured oxidized/carboxy cellulose with high carboxy content and high yield, by subjecting non-wood, lignocellulose, sugarcane bagasse derived a-cellulose or cotton cellulose to oxidation at suitable temperature, wherein the particle shape is spherical, particle size of synthesized carboxy cellulose is in the range of 1-100 nm and degree of polymerization (DP) is in the range 50-70 Further the present invention provides pharmaceutical composition comprising of nanostructured oxidized/carboxy celluloses preferably 6-carboxy cellulose, and 2,3,6-tricarboxycellulose alone or in association with one or more pharmaceutically acceptable carrier(s) or excipient(s) for treatment of microbial infections. The carboxycelluloses were efficient in stabilizing multi-walled carbon nanotubes and single-walled carbon nanotubes in aqueous media.
