Chemistry Reference
In-Depth Information
4.6.3
In Pharmaceuticals and Biomedicals Field
A novel copolymer of Ch-g-poly(
p
-dioxanone) (Ch-g-PDO) was synthesized by
Liu et al. [
112
] in bulk by ring-opening polymerization of
p
-dioxanone (PDO)
initiated by the hydroxyl group or amino group of Ch using stannous octanoate
(SnOct
2
) as catalyst. The feed ratio of Ch to PDO had great influence on the degree
of substitution (DS) and the degree of polymerization (DP) of the copolymer. The
in vitro release behavior of ibuprofen (IBU) indicated that the copolymers seem to
be a promising vehicle for controlling delivery drugs.
In recent years, nonviral cationic vectors have been applied to protect the DNA
from degradation based on the condensation of negatively charged DNA into
compact particles essentially by electrostatic interactions [
137
,
138
]. To improve
the safety of gene transfer vectors, the materials used for preparing cationic
polymers must be biocompatible and biodegradable [
139
], with high stability and
favorable biocompatibility [
95
]. Ch was first applied in the effort of gene delivery
[
140
] and widely acknowledged as one of the most attractive cationic vectors [
141
].
However, the transfection efficiency of Ch poly plexes are poor, and among all
those efforts to solve this problem, direct grafting of Ch with poly(ethylenimine)
(PEI) was considered to be one of the most prominent methods [
142
-
144
]. With a
substantial increased charge density [
145
,
146
], the modified Ch polymer creates a
hydrophilic exterior that reduces interactions of the cationic vector with plasma
proteins and erythrocytes. The transfection efficiency may depend on several
factors, such as the chemical composition of the synthetic polymer and the nano-
particle size of the complex [
147
]. The conjugation mechanism and grafting ratios
of PEI are two influential factors contributing to the obtained properties of Ch-g-
PEI [
148
].
A novel Ch-g-PEI copolymer with bio-cleavage disulfide linkages between Ch
chains and PEI grafts was synthesized, characterized, and examined as a potential
nonviral gene vector [
107
]. The obtained results showed that the bio-reducible
Ch-g-PEI copolymer could be used as a promising nonviral gene carrier due to its
excellent properties. Scheme
4.8
represents the synthesis of Ch-g-PEI copolymer
with the disulfide linkage between Ch and PEI.
Duan and his coworkers [
108
] have studied the graft copolymerization of rosin-
(2-acryloyloxy) ethyl ester (RAEE) onto Ch, with the aim to examine the prepared
copolymer as carrier for fenoprofein calcium, and their controlled release behavior
in artificial intestinal juice. They came to the conclusion that the rate of release of
fenoprofein calcium from the carrier of Ch-g-PRAEE copolymer becomes very
slower than that of Ch in artificial intestinal juice. A promising approach for
sustained pulmonary drug delivery system has been achieved by the work of El-
Sherbiny et al. [
149
]. In their study, poly(
D
,
L
-lactic-co-glycolic acid) (PLGA)
nanoparticles encapsulated in amphiphilic Ch-g-PEG copolymer-based hydrogel
microspheres were developed and evaluated as a new potential carrier system for
sustained pulmonary delivery of curcumin.
