Chemistry Reference
In-Depth Information
between cationic polymers and cell membranes [
161
]. PEG is a kind of hydrophilic
flexible, nonionic, and biodegradable polymer. PEG-coated nanoparticles have
been found to be of great potential in therapeutic application for controlled release
of drugs and site-specific drug delivery [
164
-
166
]. In addition, hydrophilic PEG
could form a hydrated outer shell, which can protect the nanoparticles from being
quickly uptaken by the reticuloendothelial system (RES) [
167
], extend the half-
lives of drugs, and change the tissue bio-distribution of drugs.
Some novel thiosemicarbazone-Ch derivatives were prepared and characterized
for their antifungus activity by Qin et al. [
168
]. The results indicated that the
thiosemicarbazone-Ch derivatives possessed great antifungal activity against
S. solani
,
R. solani
,
A. solani
, and
P. asparagi
. On the other hand, Sabaa and his
group [
119
] graft copolymerized poly(
N
-vinyl imidazole) onto CMCh and tested
the prepared copolymer for its antimicrobial activity. The results indicated that the
grafted products have improved the antimicrobial activity of CMCh against
S. aureus
and
E. coli
bacteria and against
F. oxysporum
and
A. fumigatus
fungi.
4.7 Conclusions
Chitosan, the
N
-deacetylated product of the naturally occurring chitin, is a cheap
and nontoxic material, in addition to its biocompatibility and biodegradability. Ch
possesses two active functional groups, the amino and the hydroxyl groups, which
make it easy to be chemically modified to give desirable products for diverse
applications. Modification of Ch can be done by direct interaction with the men-
tioned functional groups through esterification, carboxymethylation, acylation,
Schiff's bases reactions, etc. or through grafting with vinyl or acrylate polymers.
Recently, the increasing importance and interest in chemical modification of Ch by
graft copolymerization became a demand to improve its solubility and widen its
applications. Thermal analyses, scanning electron microscopy, X-ray diffraction,
and spectral analyses are considered to be useful tools for the proof of grafting. The
physical and chemical properties of Ch are greatly altered with the type of modifi-
cation. Ch-grafted copolymers find wide applications as superabsorbent materials,
in metal uptakes, and as ion exchangers, in swelling properties and in forming
hydrogel materials, as well as in pharmaceuticals and in drug delivery systems.
References
1. Pillai CKS, Paul W, Sharma CP (2009) Chitin and chitosan polymers: chemistry, solubility
and fiber formation. Prog Polym Sci 34(7):641-678
2. Khor E (2002) Chitin: a biomaterial in waiting. Curr Opin Solid State Mater Sci 6(4):313-317
3. Van Luyen D, Dm H (1996) In: Salamone J (ed) Polymeric materials encyclopedia, vol 2.
CRC, Boca Raton, FL, p 1208
