Biomedical Engineering Reference
In-Depth Information
drug (i.e., protein) loading is low and the carrier is difficult to manufacture, which have led
to reduced yield and increased manufacturing costs [175].
Chitosan has been recently highlighted for its unique features in pharmaceutical for-
mulations, especially in DDSs such as micro/nanoparticles and hydrogels for mucosal
and vaccine delivery. It is particularly well suited for the formulation of drugs such as
peptides, proteins, RNA, and DNA, offering unique functionalities such as mucoadhe-
siveness, enhanced bioavailability, enhanced cross-ing of biological barriers, bioresorb-
ability, targeting power, and easy and robust processing into various forms [176].
Unfortunately, despite the high number of published studies, chitosan is not approved by
the FDA for any product in drug delivery [177]. Some companies are conducting trials to
develop chitosan-based DDS products. For example, West Pharmaceutical Services, Inc.
has developed ChiSys™, a versatile transmucosal delivery system based on chitosan to
deliver leuprolide for the treatment of prostate cancer [173]. Several human trials have
been carried out on ChiSys™ for delivering a range of compounds from small molecules
and peptides to proteins and vaccines, and a higher bioavailability of drugs and few
adverse effects have been reported to date [173]. With the aim of developing chitosan-
based DDS products approved by FDA in the future and enabling the provision of health
benefits over current formulations, more clinical trials need to be carried out and more
precautions, that is, purification of chitosan, shape/geometries/size of the vehicle, biodis-
tribution, and degradability, should be taken [177].
6.9 Conclusions
Owing to their well-documented biocompatibility, biodegradability, low toxicity, mucoad-
hesivity, pH-sensitivity, and so on, as well as the merits of hydrogels, chitosan-based
hydrogels in various geometries have long been used as DDSs. Additionally, because of
the chemical activity of the amine groups along the macromolecules, chitosans are modi-
fied and an impressive number of chitosan derivatives have been developed to broaden the
applications of chitosan-based gels as drug delivery carriers. The approach of chemical
modification of chitosan or grafting chitosan with other functional materials such as
stimuli-responsive polymers, cyclodextrins, and biomolecules is of potential importance
in drug delivery fields since the resulting materials exhibit an improved drug loading
capacity and sustained release behavior along with other unique properties such as stim-
uli-sensitivity, good mechanical strength, and so on. Today, the most attractive and signifi-
cant drug delivery such as environment stimuli-controlled delivery, targeted or specific
local delivery, as well as tough drug delivery such as delivery of macromolecules, hydro-
phobic drugs, bioactive molecules, DNA, gene, and vaccine are all achieved by using chi-
tosan-based gel DDSs. These kinds of hydrogels are becoming one of the most significant
and promising DDSs.
However, extensive research is still necessary to demonstrate the safety of novel chito-
san derivatives. Clinical trials should be given emphasis to optimize chitosan-based for-
mulations for DDSs with a broad range of therapeutic applications. With a better
understanding of the fundamental loading and release criteria of different therapeutics as
well as the mechanisms of action of novel chitosan-based hydrogel carriers, further opti-
mizations of these systems can be made by researchers, and chitosan hydrogel DDSs could
be applied clinically in the near future to relieve the suffering of patients.
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