Control of Thermogelation Properties of Hydrophobically-Modified Methylcellulose

Abstract

Aqueous solutions that undergo reversible thermosensitive gelation around body temperature were developed based on hydrophobically-modified methyl cellulose (HMMC). The approach involved HMMC as the main component of aqueous compositions to provide a system with fast gelling properties, which has not been accomplished with aqueous solutions of unmodified methyl cellulose (MC). MC was modified with the stearyl group as a hydrophobic modifier by controlling the degree of modification. The gelation rate of aqueous solutions containing identical amounts of HMMC and NaCl increased as the temperature increased. The HMMC solutions gelled at a fixed temperature and concentration range, while the unmodified MC solutions did not show sol-to-gel transition. In addition, HMMC solutions exhibited much faster gelation than MC solutions at given polymer and NaCl concentrations. The HMMC/NaCl solutions exhibited the reversible gel-to-sol transition upon cooling below 25°C. The rate of sol-to-gel transition at body temperature, and the reversible gel-to-sol transition at room temperature, were modulated by adjusting the concentration of HMMC and NaCl, respectively. The HMMC/NaCl compositions provided a simple system for accurate control of the thermogelling temperature and the thermogelation rates.