Spherical aggregates obtained from N-carboxymethylation and acetylation of chitosan

Chitosan is a biopolymer with great industrial potential. However, solubility in aqueous solutions limits some applications. In this paper, the N-carboxymethylation (CM) of chitosan generated five derivatives namely, N -carboxymethylchitosan (NCMC) 1, NCMC2, NCMC3, NCMC4, and NCMC5, from 10.1% to 80% of CM. Afterwards, a new NCMC6 (∼60% of CM) was acetylated to produce the NCMCAc derivate. The modifications were confirmed by 13 C nuclear magnetic resonance. A globular conformation to NCMC derivatives was confirmed by association of static and dynamic light scattering in which the form factor ( ρ ) is ∼1.3 in phosphate buffer (pH 7.4). The NCMCAc showed a ρ of 0.75, which is characteristic of dense spheres. Topographical analyses were performed by atomic force microscopy images in which dense spheres were observed. The critical aggregation concentration (CAC) was determined using pyrene as a hydrophobic fluorescent probe. For NCMC1–6 and NCMCAc, a CAC of 1.0 and 0.1 mg mL −1 were, respectively, observed. NCMC1–6 and NCMCAc showed a globular and dense spherical conformation, respectively.