Synthesis Characterization of Nanocellulose and Surface Modified Nanocellulose for Various Pharmaceutical Applications

Abstract

Cellulose is a polysaccharide composed of linear glucan chains linked together by and#946;-1,4-glycosidic bonds with cellobiose residues as the repeating unit at different degrees of polymerization (DP) and packed into microfibrils which are held together by intramolecular hydrogen bonds as well as intermolecular van der waal forces. These cellulose fibrils serve as the primary phase of reinforcement for bacteria, algae, certain marine organisms (such as tunicates), trees, plants, and some types of algae. Certain bacteria release cellulose fibrils, which help to form an exterior network structure. newlineCrystalline cellulose exists in several types of polymorphs (I, II, III, and IV). Cellulose I is crystalline cellulose that is naturally produced by a variety of organisms (trees, plants, tunicates, algae, and bacteria). It is also known as natural cellulose. Cellulose I is thermodynamically metastable and can be converted to polymorphs II or III. The most stable cellulose polymorphs among all are type II and they can be produced by two processes: regeneration (solubilization and recrystallization) and mercerization (aqueous sodium hydroxide treatments). Cellulose II has monoclinic structure and is used to prepare transparent films. newlineCellulose chains are organized in a pattern known as quotparallel upquot in both Iand#945; and Iand#946; unit cells. The 1-to-4 linkage (1-4 linkage) throughout the length of the cellulose chain alters how nearby chains interact with one another because the cellulose repeat unit has a distinct structure on each side of the 1-4 linkage. When all the cellulose chains are arranged in 1 4 in the same direction, the word quotparallelquot is used. Contrarily, quotantiparallelquot refers to the alternate stacking of cellulose chains in the directionality of 1 to 4 links between various hydrogen bonding planes. newlineAlthough polymorph has been documented for cellulose, X-ray diffraction analysis indicates that native cellulose occurs as cellulose I, a mixture of polymorph Iand#945; and Iand#946;.