Biomedical Engineering Reference
In-Depth Information
Fig. 12 (a) Chemical
structure of poly(sarcosine)-
b
-poly(
g
-methyl
L
-glutamate)
copolymer.
(b) Bioluminescence image
of tumor-bearing mouse after
administration of
D
-luciferin.
(c) In vivo cancer imaging
using NIRF-labeled
peptosome. Fluorescence
image after 1 day of
administration of the labeled
peptosome. Reprinted from
[
239
] with permission
a
O
O
H
N
HO
N
N
H
O
n
m
O
O
Image
Min = 0
c
b
Max = 5.4366e+0.7
40
35
30
25
20
Color Bar
Min = 2e+0.7
Max = 4e+0.7
inherent peptide functionality provides a new approach for design of multifunc-
tional polymersomes for DDS.
On the other hand, Kataoka and coworkers have developed a novel type of
polypeptide-based polymersome composed of PEG-
b
-PAsp and PEG-
b
-poly
[(5-aminopentyl)-
a
,
b
-aspartamide] with a nonionic PEG block and anionic or
cationic polypeptide blocks [
210
,
240
]. These block copolymers do not rely on
amphiphilicity for self-assembly, but rather simple mixing of a pair of opposite and
equally charged block copolymers results in a stable PIC membrane that forms
polymersomes (“PICsomes”). Since PICsome membranes do not have a hydro-
phobic core, they have an increased permeability to hydrophilic compounds with
molecular weights below 450 Da. Furthermore, PICsomes with crosslinked mem-
brane through covalent bonds showed tuning of permeability, enhanced stability
under physiological conditions, and long blood circulation time in mice [
241
].
Kimura and coworkers have also developed hybrid-type polymersomes com-
posed of polysarcosine-
b
-PLA (“lactosomes”) [
242
-
243
]. The lactosomes are fully
biodegradable due to the equipped metabolic pathway for sarcosine and lactic acid.
Hence, the lactosome is preferred for in vivo applications rather than for in vitro
studies. Indeed, they have demonstrated a potential utility of lactosomes as a
contrast agent for in vivo liver tumor imaging [
243
]. Lactosomes labeled with
indocyanine green showed high escape ability from RES, were found to be stable in
