The rheological injectability of N-succinyl-chitosan solutions.

The viscosity of a set of N-succinyl-chitosan (NSC) solutions was characterized near the 0.2Pas rheological injectability limit. This is believed to be the first such report in the open literature. Viscosity was characterized at physiological pH and ionic strength as a function of NSC degree of substitution, NSC concentration, temperature, and shear rate. NSC was synthesized via Yamaguci's method and characterized using H-NMR, membrane osmometry, TGA and isothermal vacuum drying. NSC synthesis results were shown to fit a reproducible log-linear correlation and both optimum drying temperature and thermal decomposition temperature were found to be a function of NSC degree of substitution. Viscosity results were explained using Katchalsky's full model for polyampholyte ionization combined with a charge induced excluded volume model proposed by Higgs. The model predicted a polyelectrolyte/polyampholyte transition which agreed well with experimental data. For minimally injectable formulations a maximum in primary amine concentration is expected at 32sub% amine NSC.