Future - Chitosan Based Hydrogels: Functions and Applications - page 472

has been explained by its capacity to open the tight junction between epithelial cells, thus
facilitating the transport of macromolecular drug through well-organized epithelia via
redistribution of F-actin, a protein of the cytoskeleton which regulates paracellular flow
[ 3 7, 3 8 ] .
The addition of poly(ethylene glycol) significantly decreased both the burst release and
the encapsulation efficiency, whereas the addition of alginate reduced the burst release,
while protein loading remained high [39].
In recent years, it has been demonstrated that chitosan derivatives such as thiolated or
quaternized chitosan have superior mucoadhesive and absorption-enhancing properties.
These chitosan derivatives might be efficient in both soluble and particulate forms. It can
be concluded that so far chitosan-based particles do not fulfill all the criteria needed for
the delivery of therapeutic proteins. Factors such as poor efficacy and avoidance of possi-
ble immunogenicity of therapeutic proteins as well as possible long-term toxicity of chito-
san-based polymers need further investigation.
Chitosan-based systems offer great opportunities for the delivery of protein therapeu-
tics and antigens. To achieve clinical exploitation of chitosan-based formulations of thera-
peutic proteins, some important hurdles need to be cleared. Chitosan-based vaccines have
shown excellent potential in preclinical models and promising results in clinical trials;
however, also for these systems, further optimizations are necessary for obtaining clinical
approval.
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