Biomedical Engineering Reference
In-Depth Information
polymer is a non-viral vector which has enhanced absorption, controlled
release and bioadhesive properties. h e modii ed derivatives of chitosan
possess added advantages such as increased solubility, mucoadhesivity and
many other functional advantages [15].
Each route of administration depends on the biopharmaceutical being
administered and the intended target [117]. As a result of chitosan's mucoad-
hesivity, the polymer can possibly remain in contact with the gastrointestinal
tract for a longer period of time. h is may result in an increase in the bioavail-
ability of the biopharmaceutical being administered. Modii cations of chito-
san and its derivatives can be made to overcome some of the disadvantages
associated with the various administration routes [15]. Vectors can be conju-
gated to the polymer to allow for targeted delivery of the biopharmaceutical.
h ese vectors can be biologically active substances (BAS) where the method
of conjugation depends on several factors such as the mechanism of thera-
peutic ef ect, the ideal i nal structure of the biopolymer and the nature of the
BAS [118]. Chitosan-based nanoparticles have been used in the transport of
peptides, antigens and plasmid DNA among others. Studies have shown that
these nanoparticles enhance drug absorption, promote mucosal immunisa-
tion and gene expression. Chitosan-hybrids NPs have been used as carriers as
these particles protect the entrapped biopharmaceuticals from degradation,
improve cellular uptake and can be delivered
via
dif erent administration
routes (oral, nasal and pulmonary) [119]. Triggered release is also an impor-
tant point to consider when designing delivery agents. h is refers to the
release of a BAS in response to stimuli such as pH or temperature changes.
Other factors which also af ect release of active substances are exposure to
redox species, certain biomolecules, ions, electric i elds or light [120]. Zhang
et al.
synthesized a dibenzaldehyde-functionalized chitosan-based hydrogel
whose response to various stimuli was investigated [121]. h is hydrogel was
also used to encapsulate small molecules and proteins whose release could be
controlled by exposure to various stimuli [121]. A dual responsive chitosan
terpolymer (poly[(2-dimethylamino)ethyl methacrylate] and poly(N-iso-
propylacrylamide)) was recently synthesized using a combination of Atom
transfer radical polymerization (ATRP) and click chemistry. h is polymer
reacted to pH and temperature changes making it an ideal candidate for
gene/drug delivery and triggered release applications [122].
Targeted drug delivery may also involve bio-imaging. h ere is a great
need for non-invasive imaging methods for the study of pathological con-
ditions within the body. Chitosan has been studied as a delivery agent,
which can also be utilized for bio-imaging applications. Potara
et al.
syn-
thesized chitosan-silver nanotriangles labelled with
p
-aminothiophenol.
h ese nanoparticles were utilized as a multi-response contrast agent for
