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.

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 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。

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.