Self-assembly of N-maleoylchitosan in aqueous media

N-maleoylchitosan (NMCS) is a biocompatible derivative of chitosan, but its solubility in water is dependent on the degree of maleoyl substitution. In this study, the NMCS sample with a maleoyl substitution degree of 70% was synthesized by the reaction of maleic anhydride and the amino groups of chitosan. The resulting NMCS can be ready to dissolve in water over a wide pH range (from 2 to 9). The aggregation behavior of NMCS in aqueous media was studied by steady-state fluorescence spectroscopy, viscometric, field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). The critical aggregation concentration (CAC) of NMCS in water is found to be 0.05-0.06mg/mL. With increasing NMCS concentration to approximately 0.5mg/mL, which is 10 times of the CAC, NMCS molecules self-assemble to fiber-like aggregates with an averaged diameter of approximately 2.5microm and length of more than 100microm. The driving force for the aggregation is attributed to the hydrophobic interaction as evident from isothermal titration calorimetry (ITC) study. These fiber-like aggregates might have potential applications in tissue engineering scaffold.