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.

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.

Different molecular weight (MW) chitosans (5.5

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.