Bioactivities of Chitosan and Its Derivatives - Chitosan Based Hydrogels: Functions and Applications - page 147

pouches, which were prepared subcutaneously on the dorsal surface of mice, in order to
induce local inflammation. Chitosan gel beads retaining PS were then implanted into the
APs to investigate the therapeutic efficacy of sustained PS release against local inflamma-
tion. In vivo PS release from chitosan gel beads was governed by both diffusion of the drug
and degradation of the gel matrix. Sustained drug release by chitosan gel beads allowed
the supply of the minimum effective dose and facilitated prolonged periods of local drug
presence. Inflammation indexes were significantly reduced after implantation of chitosan
gel beads when compared with injection of PS suspension. Thus, extension of the duration
of drug activity by chitosan gel beads resulted in improved therapeutic efficacy. These
observations indicate that chitosan gel beads are a promising biocompatible and biode-
gradable vehicle for the treatment of local inflammation [149].
3.4.2 Antiulcer
3.4.2.1 Antiulcer Function of Chitosan
An ulcer is a sore or hole in the lining of the stomach or duodenum (the first part of the small
intestine). It occurs as a result of a disturbance of the natural balance between aggressive
acid-pepsin and mucosal defence-mucosal turnover. Ulcers induced by a mixture of HCl
and ethanol has been reported to show many metabolic and morphological aberrations in
the gastric mucosa of experimental animals similar to those observed in human peptic ulcer
[150]. Chitosan and their oligomers have been found to promote antiulcer, especially in the
phases of proliferation and matrix formation. It has been demonstrated that chitosan has
numerous pharmacological actions, and it can be prepared as membrane, scaffold, powder,
and so on. Histological findings indicate that chitosan membrane stimulates the migration
of inflammatory cells and promotes cellular organization. Since 1980, chitosan and its deriv-
atives have been used in skin ulcer management products in Japan [151]. It is well established
that chitosan attracts neutrophils in vitro and in vivo [152,153] and that neutrophils accelerate
ulcer healing by inciting a quicker, more aggressive inflammation. Azad et al. [154] used
chitosan membrane as a wound-healing dressing and found that the chitosan mesh mem-
brane showed a positive effect on re-epithelialization and regeneration of the granular layer.
Figure 3.15 confirms that the chitosan mesh membrane is a potential substitute for human
wound dressing. In the chitosan mesh membrane area, collagen fibers started to mature and
consolidate in thicker and more mature fibers, and were oriented and distributed more regu-
larly. In the control Bactigras, the fibers remained in a young, less-pronounced form.
3.4.2.2 Promoting Ulcer Healing of Chitosan
The quality of ulcer healing is closely related to growth factors, local blood circulation,
prostaglandin, and Helicobacter pylori ( H. pylori ) infection. The administration of basic
fibroblast growth factor (bFGF), a potent angiogenic and fibroblastic growth factor, to pres-
sure ulcers may especially benefit those of advanced age because of the biological deficien-
cies associated with aging. Guo et al. [155] administered chitosan, chitosan with sucralfate,
and chitosan with ranitidine as oral drugs, to investigate the effect of chitosan on the qual-
ity of ulcer healing of gastric ulcer in rats and its possible mechanism. After 14 days, the
size of the ulcer decreased significantly, and the expressions of EGF and bFGF in the three
experimental groups were significantly higher than those in the placebo and ranitidine
groups ( Figures 3.16 and 3.17). It was concluded that chitosan has a synergistic effect with
sucralfate and ranitidine in promoting the quality of ulcer healing.