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.

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.

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

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

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.