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 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.

The captopril/Chitosan gelatin net-polymer microspheres ( Cap/CGNPMs) were prepared using Chitosan ( CS) and gelatin ( Gel) by the methods of emulsification. A cross linked reagent alone or in combination with microcrystalline cellulose (MCC) was added in the process of preparation of microspheres to eliminate dose dumping and burst phenomenon of microspheres for the improvement of the therapeutic efficiency and the decrease of the side effects of captopril ( Cap) . The results indicate that CapPCGNPMs have a spherical shape , smooth surface morphology and integral inside structure and no adhesive phenomena and good mobility , and the size distribution is mainly f rom 220 to 280 μm. Researches on the Cap release test in vitro demonstrate that Cap/CGNPMs are of the role of retarding release of Cap compared with Cap ordinary tablets ( COT) , embedding ratio ( ER) , drug loading ( DL) , and swelling ratio ( SR) , and release behaviors of CGNPMS are influenced by process conditions of preparation such as experimental material ratio ( EMR) , composition of cross linking reagents. Among these factors , the EMR (1/4) , CLR ( FOR + TPP) and 0. 75 % microcrystalline cellulose (MCC) added to the microspheres are the optimal scheme to the preparation of Cap/CGNPMs. The Cap/CGNPMs have a good characteristic of sustained release of drug , and the process of emulsification and cross-linking process is simple and stable. The CGNPMs is probable to be one of an ideal sustained release system for water-soluble drugs.

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.

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