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 0.05–0.06 mg/mL. With increasing NMCS concentration to ∼0.5 mg/mL, which is 10 times of the CAC, NMCS molecules self-assemble to fiber-like aggregates with an averaged diameter of ∼2.5 μm and length of more than 100 μm. 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.