Synthesis and self‐assembly study of zwitterionic amphiphilic derivatives of chitosan

New zwitterionic derivatives of chitosan (CH) were synthesized through the Michael addition reaction of 1-(3-sulfopropyl)-2-vinylpyridine hydroxide (SPP) with primary amines of deacetylated CHs (with weight-average molecular weights of 46 and 216 kDa) to obtain SPP-substituted CHs. The hydrophilic derivatives were subsequently modified with 2.1, 4.6, and 9.7% of dodecyl groups [degree of substitution by dodecyl groups (DSDod)]. The SPP-substituted CH derivatives were characterized by 1H-NMR, Fourier transform infrared spectroscopy, and gel permeation chromatography. Aqueous solutions of SPP-substituted CH samples remained clear, independently of the pH (3.0 < pH < 12.0). The self-association study of the amphiphilic derivatives was performed in aqueous buffered solution at pH 5.0 and 7.4, and the critical aggregation concentration values varied from 5.6 × 10−3 to 0.02 g/L. The measurements of dynamic light scattering and ζ potentials showed that the self-assembly behavior was dependent on the pH and DSDod. At pH 7.4, the measured ζ potentials were near zero, and colloidal stability was provided by the hydrated zwitterionic shell of the aggregates. Transmission electron microscopy revealed spherelike microsized particles of broad distribution. The amphiphilic SPP-substituted CH samples were shown to be nontoxic with a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay performed with HeLa cells. The remarkable water solubility and nontoxicity displayed by the new SPP-substituted CH derivatives showed promising properties for the design of CH-based biomaterials and nanoparticles. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44176.