Oral Delivery of Proteins and Peptides: Concepts and Applications - Challenges in Delivery of Therapeutic Genomics and Proteomics - page 500

Bioadhesive Materials Properties Characteristics

Chitosan a linear polysaccharide
composed of randomly distributed
-(1-4)-linked D-glucosamine
(deacetylated unit) and N -acetyl-D-
glucosamine (acetylated unit)

l Prepared from chitin of crabs and lobsters by N-
deacetylation with alkali
l  dilutes acids to produce a linear polyelectrolyte
with a high positive charge density and forms salts
with inorganic and organic acids such as glutamic
acid, hydrochloric acid, lactic acid, and acetic acid.
l The amino group in chitosan has a p K a value of
 6.5; thus, chitosan is positively charged and
soluble in acidic to neutral solutions with a charge
density dependent on pH and the %DA-value.

l Mucoadhesive agent due to either secondary chemical
bonds, such as hydrogen bonds, or ionic interactions
between the positively charged amino groups of
chitosan and the negatively charged sialic acid
residues of mucus glycoproteins or mucins
l Possesses cell-binding activity due to polymer
cationic polyelectrolyte structure and to the negative
charge of the cell surface
l Biocompatible and biodegradable
l Excellent gel-forming and film-forming ability
l Widely used in controlled delivery systems such as
gels, membranes, and microspheres
l Chitosan enhances the transport of polar drugs across
epithelial surfaces. Purified qualities of chitosans
are available for biomedical applications. Chitosan
and its derivatives such as trimethylchitosan (where
the amino group has been trimethylated) have been
used in nonviral gene delivery. Trimethylchitosan,
or quaternised chitosan, has been shown to transfect
breast cancer cells. As the degree of trimethylation
increases, the cytotoxicity of the derivative increases.
At approximately 50% trimethylation, the derivative
is the most efficient at gene delivery. Oligomeric
derivatives (3-6 kDa) are relatively nontoxic and have
good gene delivery properties.

Carrageenan an anionic
polysaccharide, extracted from the
red seaweed Chondrus crispus

l Available in sodium, potassium, magnesium,
calcium, and mixed cation forms
l Three structural types: iota, kappa, and lambda,
differing in solubility and rheology

l All solutions are pseudoplastic with some degree of
yield value. Certain ca-Iota solutions are thixotropic.
Lambda is non-gelling, kappa produces brittle gels;
Iota produces elastic gels. All solutions