Biomedical Engineering Reference
In-Depth Information
a
b
CH2-CH-COOC
2
H
5
CH
2
OH
CH
2
OH
NH
CO
O
COOCH
3
COOH
O
O
OH
O
O
O
OH
O
m
n
O
O
NH
2
NH
C=O
OH
OH
OH
m
n
I
OH
OH
CH
3
OH
CH
3
C
CH
3
HO
500 nm
Fig. 8 Preparation of amphiphilic polysaccharide. Chemical structures of deoxycholic acid-
modified chitosan (a) and Phe-modified pectin (pectin-
graft
-Phe) (b). SEM image of nanoparticles
prepared from pectin-
graft
-Phe (c)
hydrophobically modified chitosans with deoxycholic acids (Fig.
8a
)[
83
,
84
].
The size of self-aggregates varied in the range of 130-300 nm in diameter,
and their structures were found to depend strongly on the molecular weight of
chitosan. To explore the potential applications of self-aggregates as a gene
delivery carrier, complexes between chitosan self-aggregates and pDNA were
prepared. The complex formation had a strong dependency on the size and
structure of chitosan self-aggregates and significantly influenced the transfection
efficiency of cells. It is expected that these approaches to control the size and
structure of chitosan-derived self-aggregates will have a wide range of
applications in gene delivery. Also, Kida et al. reported that novel polysaccha-
ride-based nanoparticles were successfully prepared by the self-assembly of
amphiphilic pectins, which were easily synthesized by the reaction of pectins
with Phe as hydrophobic group (Fig.
8b
)
85
]. Pectin is a polymer of
D
-galacturonic acid. The galacturonic acid molecule has a carboxyl group on
C5, some of which are esterified to form methyl esters. The pectin-
graft
-Phe
could form about 200 nm-sized nanoparticles (Fig.
8c
), and were able to retain
entrapped protein in the nanoparticles for one week without any significant
leakage.
2.4 Polyion Complex Nanoparticles
Polymer complexes associated with two or more complementary polymers are
widely used in potential applications in the form of particles, hydrogels, films, and
membranes. In particular, a polyion complex (PIC) can be easily formed when
oppositely charged polyelectrolytes are mixed in aqueous solution and interact via
