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Zwitterionic nanocrystals were prepared by TEMPO-mediated oxidation, partial deacetylation, and subsequent mechanical disintegration of α-chitin. The pH dependence of the morphology, transparency, and viscosity of the nanocrystals were evaluated. After those reactions, the carboxylate and amino group contents of the chitin derivative were 0.45 and 1.26 mmol/g, respectively. After mechanical treatment, the water dispersion consisted of nanocrystals approximately 250 nm long and 10nm thick. Under acidic and basic conditions, the water dispersions were highly transparent. On the other hand, under neutral conditions, the dispersion was turbid due to the ionic interaction between the cationic and anionic groups on the nanocrystal surface. Although the surface zwitterionic nanocrystals collected from acidic and basic dispersion were randomly oriented due to electrostatic repulsions, nanocrystals formed aggregates in neutral water due to the cationic and anionic interaction between them. Nanocrystals in neutral water had higher viscosity than those in acidic and basic water, since ionic interaction caused nanocrystal networks to form in water., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Synthesis of a highly regioselective amphiprotic chitosan derivative was achieved by click chemistry. The Huisgen cycloaddition between 6-azido-6-deoxy-N-pthaloyl-chitosan and methyl propiolate was successfully carried out in the presence of Cu(I) catalyst. After the reaction, both the phthaloyl protecting group and methyl group were completely removed by hydrazine. FT-IR and NMR spectroscopy as well as elemental analysis strongly support the structural uniformity of the desired amphiprotic chitosan derivative, which has both a carboxylic group with a 1,4-triazole linker at the C-6 position and an amino group at the C-2 position per repeating unit. The amphiprotic chitosan derivative was soluble under both acidic and basic aqueous conditions. In contrast, it formed nanoparticle under neutral condition due to the interaction between the positive (-NH(3)(+)) and negative (-COO(-)) ions on the chitosan derivative., (Copyright © 2012 Elsevier B.V. All rights reserved.)

The in vitro drug-release behavior of chitosan-carboxymethyl dextran nanoparticles (CDNP) containing cefmetazole, 5-fluorouracil (5-FU) or indocyanine green (ICG), and the in vitro effect of CDNP on mouse B16 melanoma cell proliferation and in vivo modulation effect of CDNP on serum cytokines and spleen lymphocytes in mice were evaluated in this study. Drug-loaded CDNP were prepared by embedding (for cefmetazole or 5-FU) and absorption (for ICG), and the particle size was increased with increased drug association efficiency (AE) and decreased surface amino group content. Prolonged release of cefmetazole (540 min) or 5-FU (360 min) from CDNP was observed when compared to that of nanoparticle-free cefmetazole (210 min) or 5-FU (50 min), and the release of cefmetazole or 5-FU from CDNP98 (CDNP made with 98% degree of deacetylation (DD) chitosan) was slower than from CDNP78 (CDNP made with 78% DD chitosan). High AE (72.0-98.6%), undetectable surface amino group content and dramatically increased particle size (1076.9-1506.0 nm) of ICG-loaded CDNP with undetectable release of ICG within 48 h revealed the good affinity between ICG and CDNP. Twenty-five to 100 μg/ml of CDNP elicited dose-dependent inhibitory effects on B16 tumor cell proliferation, and CDNP98 was more effective than CDNP78. CDNP78 regulated serum IL-17 level in up-regulating IL-4, IL-6, IL-10, IL-23 and TGF-β within 3 h; on the other hand, CDNP98 significantly down-regulated TGF-β and had no induction effect on IL-23 within 24 h. In addition, reduced IL-17 was observed in CDNP at 24 h. CDNP98 was more effective than CDNP78 in stimulating mouse splenic T CD4(+), TCD8(+) and NK cell proliferation within 24 h, while CDNP78 was superior to CDNP98 in stimulating B CD19(+) cells. The ability of CDNP to be the drug carrier and to enhance both humoral and cell-mediated immune response in this study demonstrated its promising potential to be applied as biomedical material.

Chitosan-carboxymethyl dextran nanoparticles (CHI-CMD NPs) were prepared by the formation of polyelectrolyte complex via the interaction of the positive charged amino group of chitosan and the negative charged carboxyl group of carboxymethyl dextran. Biocompatible organic reagents such as lactic acid, phosphate-buffered saline, and carbonate-bicarbonate buffer were used to make CHI-CMD NPs. The pH value of narrowly distributive CHI-CMD NP suspension was close to the physiological value of 6.8, which made it possible for it to be directly applied in an in vitro test without further additional operations. In the presence of sugars (30 mM), the colloidal stability of CHI-CMD NPs could be extended to 5 to 7 days when the particle size could be maintained within a nanometer scale, while the addition of xylose or lactose was found to most effectively extend the colloidal stability of CHI-CMD NPs to 10 days. Scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction analysis revealed that the structural integrity of CHI-CMD NPs was not destroyed after high steam pressure sterilization (121 degrees C, 30 min), which confirmed the autoclavable property of CHI-CMD NPs.