| New forms of low crystallinity cellulose excipients; low crystallinity powder cellulose (LCPC), low crystallinity bead cellulose (LCBC), and hydrated low crystallinity cellulose (HLCC) have been developed. HLCC was prepared using phosphoric acid to decrystallize and depolymerize cellulose. The decrystallization is prevalent at lower temperature, and the depolymerization at higher temperature. The reaction was first order, with an activation energy of 25.2 kcal/mol. Based on the mechanisms, the reaction was optimized. LCPC was prepared from the HLCC by dehydration and drying, and LCBC by spray drying.; The product was cellulose, confirmed by FTIR and ESCA, with a degree of polymerization ranged 60 to 150 units.; LCPC and LCBC have been evaluated as improved direct compression tablet binder and disintegrant, compared with microcrystalline cellulose, MCC. LCPC and LCBC were highly agglomerated with submicron particles. The sorption isotherm of LCPC was slightly higher than MCC. LCPC and LCBC demonstrated greatly reduced crystallinity, higher enthalpy of immersion and surface area. A Heckel plot demonstrated plastic deformation of LCPC with a lower mean yield pressure. LCPC tablets demonstrated strong fusion of particles and a stronger crushing strength than MCC, while LCBC demonstrated a capillary structure, fast water penetration and disintegration. The superior crushing strength of the LCPC tablets is ascribed to the extensive hydrogen bond formation and the enhanced true contact area. The fast disintegration of LCBC tablets is the result of a strong interaction with water, capillary action, the release of elastic energy and enthalpy of immersion, as well as a lack of excipient entanglement.; When compressed with a difficultly compressible drug, acetaminophen, or a sparingly soluble drug, griseofulvin, LCPC and LCBC produced superior tablets which were stronger tablets and disintegrated faster, compared with MCC or commercial tablets.; HLCC has been evaluated as a suspending and film forming agent in topical formulations. With submicron particle sizes and strong interactions with water, HLCC is suspendable and sprayable in water and alcohol, and does not cake if settled. HLCC can form transparent, uniform, and tight films by coalescence. HLCC does not form color reactions with drugs containing amino groups. |
