Biomedical Engineering Reference
In-Depth Information
traditional vaccine adjuvants, chitosan was equipotent to IFA and superior to
aluminum hydroxide. Mechanistic studies revealed that chitosan exhibited at
least two characteristics that may allow it to function as an immune adjuvant.
First, the viscous chitosan solution created an antigen depot. More specii -
cally, less than 9 % of a protein antigen, when delivered in saline, remained
at the injection site at er 8 hrs. However, more than 60 % of a protein antigen
delivered in chitosan remained at the injection site for 7 days. Second, chi-
tosan induced a transient 67 % cellular expansion in draining lymph nodes.
h e expansion peaked between 14 and 21 days at er chitosan injection and
diminished as the polysaccharide was degraded. h e results envisage chito-
san as a promising and safe platform for parenteral vaccine delivery.
Because of its mucoadhesive properties, chitosan has also been explored
as an adjuvant for mucosal vaccination by oral and intranasal route [146,
147]. h e mechanisms of vaccine action enhancement by chitosan are
believed to be due to both, retention of vaccine in the mucosal passages
via mucoadhesion, and opening of endothelial cell junctions for paracellu-
lar transport of vaccine. Augmentation in immunogenicity of co-adminis-
tered antigens and stimulation of immune system has been widely studied
for a variety of antigens and for various routes (Table 6.5).
6.8
Chitosan as Wound Healing Accelerator
h e history of chitin and its derivatives as wound healing accelerators began
with the studies of Prudden, et al [178]. h ey noticed that the shark cartilage
accelerated wound healing and suggested that glucosamine, which is a com-
ponent of shark cartilage, functioned mainly as a healing accelerator. Hence,
chitosan, a copolymer of N-acetyl-D-glucosamine and D-glucosamine has
been scrutinised for the wound healing activity [179-184].
Wound healing process comprises of i ve overlapping stages that involve
complex biochemical and cellular processes. h ese are described as hae-
mostasis, inl ammation, migration (epithelial cells and i broblasts, mac-
rophages), proliferation (granulation tissue formation, collagen synthesis,
vascular tissue formation, epithelisation) and maturation (remodelling)
phases [185]. h is involves the i ne tuning of complex interactions among
cells, extracellular matrix components and signaling compounds.
Chitosan accelerates various activities in the wound healing process, as
ini ltration of inl ammatory cells [186] chemoattraction [187-189], func-
tions of polymorph neutrophils [phagocytosis, production of osteopontin
[190], tumor necrosis factor-α, interleukin (IL)-1, IL-8, IL-12, leukotriene
B4, macrophage inl ammatory protein (MIP)-1a and MIP-1b [191-193]
