Carboxymethyl chitosan (CM-chitosan) was prepared by chemical reaction with monochloroacetic acid under various conditions, and the chemical structure was analyzed by IR and NMR. The water solubility of the CM-chitosans had close relationships to the modifying conditions and the degree of carboxymethylation. The CM-chitosans, prepared at temperatures of 0-10 8C were soluble in water. But the CM-chitosan prepared between 20 and 60 8C were insoluble in the water at near-neutral pH. The water insolubility of CM-chitosans at various pHs varied with the degree of carboxymethylation. The increase in reaction temperature increased the fraction of carboxymethylation and increased the insolubility at lower pHs; the increase of the ratio of water/isopropanol in the reaction solvent decreased the fraction of carboxymethylation and increased the insolubility at higher pHs.

The protonation constants of chitosans with different molecular weight (Mw) and degree of deacetylation were demonstrated by the modified Henderson-Hasselbalch model and Hogfeldt’s three-parameter model. The protonation constants pKa of chitosan showed a slightly decreasing from 6.51 to 6.39 when the molecular weight changing from 1370 to 60 kDa. The degree of deacetylation showed a greatly effect on pKa values, which were increased from 6.17 to 6.51 with the degree of deacetylation decreasing from 94.6 to 73.3%. The degree of deacetylation influenced the balance of hydrophobic interactions and hydrogen bondings on chitsoan. The fitting of the titration data to both two methods showed that Hogfeldt’s three-parameter model provided a better agreement. The results obtained in this paper allowed to a better understanding of some physicochemical mechanisms and biological properties of chitosan.

In a new approach to the preparation of solid chitosan acetate, the dependence of solubility of chitsoan acetate on the mole ratio of acetic acid to GlcN residues of chitosan was evaluated from turbidity. The structure of the product chitosan acetate was characterized by titration and FT-IR. It was demonstrated that the chitosan acetate with high solubility retained the structure and antibacterial activity of chitosan. The antibacterial activities against Escherichia coli (Gram negative) and Staphylococcus aureus (Gram positive) have been exhibited by a special kind of agar and further investigated by optical density method. It was found that chitosan acetate at a concentration of 0.1% (m/V) exhibited some antibacterial activity but some of the bacteria did still grow. With a concentration of 0.15% (m/V), there were nearly no bacteria grown. Electron micrographs revealed bacterial action patterns of chitosan acetate towards E. coli and S. aureus.

Chitosan was modified by coupling with linoleic acid through the 1-ethyl-3-(3-dimethylaminopropyl)- carbodiimide-mediated reaction to increase its amphipathicity for improved emulsification. The micelle formation of linoleic acid-modified chitosan in the 0.1 M acetic acid solution was enhanced by O/W emulsification with methylene chloride, an oil phase. The fluorescence spectra indicate that without emulsification the self-aggregation of LA-chitosan occurred at the concentration of 1.0 g/L or above, and with emulsification, self-aggregation was greatly enhanced followed by a stable micelle formation at 2.0 g/L. The addition of 1 M sodium chloride promoted the self-aggregation of LA-chitosan molecules both with and without emulsification. The micelles of LA-chitosan formed nanosize particles ranging from 200 to 600 nm. The LA-chitosan nanoparticles encapsulated the lipid soluble model compound, retinal acetate, with 50% efficiency.

Membranes were prepared from chitosan with different molecular weights by a casting method. The molecular affinity and permeability of the membranes for sodium chloride, glucose, tyrosine, and bovine serum protein were measured at 4

A noval cellulose acetate/chitosan multimicrospheres (CACM) was prepared by the method of w/o/w emulsion. The concentration of cellulose acetate (CA) and the ratio of CA/chitosan (CS) had influence on the CACM size, and appearance. Ranitidine hydrochloride loading, and releasing efficiency in vitro were investigated. The optimal condition for preparation of the microspheres was CA concentration at 2% and the ratio of CA/CS at 3/1. The microspheres size was 200-350 μm. The appearance of microspheres was spherical, porous, and nonaggregated. The highest loading efficiency was 21%. The ranitidine release from the CACM was 40% during 48 hr in buffers.

In this study, different molecular weight CM-chitosans were prepared and the effects on the growth and collagen secretion of normal skin fibroblasts and keloid fibroblasts were investigated in vitro. CM-chitosan promoted the proliferation of the normal skin fibroblast significantly but inhibited the proliferation of keloid fibroblast. The higher CM-chitosan concentration had a higher initial effect and the lower CM-chitosan concentration had a longer affecting time to the normal skin fibroblast. The lower molecular weight CM-chitosan had significant twofold activities. The CM-chitosan could reduce the ratio of type I/III collagen in keloid fibroblast by inhibiting the secretion of collagen type I; and had no effect on the secretion of types I and III collagen in the normal skin fibroblast. r 2002 Elsevier Science Ltd. All rights reserved.

Different molecular weight (MW) chitosans (5.5

The main aim of this study was to compare two microspheres, chitosan (CTS) and CTS/β-cyclodextrin (β-CD), made by spray-drying, as pulmonary sustained drug-delivery carriers. Theophylline (TH) was used as a model drug. The characteristics of the microspheres and in vitro release were studied. The yield of CTS/β-CD microspheres was 46.1%, which was higher than that of the CTS microspheres (36.5%). The drug loads of the CTS and CTS/β-CD microspheres were 22.7 and 21.1%, respectively, whereas the encapsulation efficiencies were 90.7 and 91.4%, respectively. The distribution of 50% [(diameter) d (0.5)] of the CTS microspheres was below 6.49 mm and that of the CTS/β-CD microspheres was below 4.90 mm. Scanning electron microscopy showed that both microspheres yielded a spherical shape with smooth or wrinkled surfaces. Fourier transform infrared spectroscopy demonstrated that the carbonyl group of TH formed hydrogen bonds with the amide group of CTS and the hydroxyl group of b-CD. The swelling ability of the two microspheres was more than three times their weight, and their humidity rates attained equilibrium within 24 h. The ciliary beat movement times of CTS and CTS/β-CD microspheres were 493.00 and 512.33 min, respectively, which indicated that the two microspheres effectively reduced the ciliotoxicity and possessed better adaptability. In vitro release of TH from CTS/β-CD microspheres was slower than that from CTS microspheres at pH 6.8 and provided a sustained release of 72.0% within 12 h. The results suggest that CTS/β-CD microspheres are a promising carrier for sustained release for pulmonary delivery. 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1183-1190, 2007

通过玻璃流延法制备不同分子质量的壳聚糖及羧甲基壳聚糖膜，以体外培养的人皮肤成纤维细胞作为对象，利用膜的浸渍液培养及膜表面直接培养法研究比较了两种多糖膜的细胞相容性。实验发现两种多糖膜的浸渍液对细胞均无毒性效应，生物安全性是小分子质量膜好于大分子质量膜，羧甲基壳聚糖膜好于壳聚糖膜。皮肤成纤维细胞在壳聚糖膜上的生长受到抑制，生长一段时间后细胞有聚集和脱落现象，而羧甲基壳聚糖膜上细胞能很好地贴附、生长，没有聚集和脱落现象。结果表明羧甲基壳聚糖膜具有比壳聚糖膜更优越的细胞相容性。