Biomedical Engineering Reference
In-Depth Information
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Figure 6.4
Illustration of pH and reduction dual-bioresponsive polymersomes based
on PEG-SS-PDEA diblock copolymer for facile loading and triggered
intracellular release of proteins. (Reproduced from Zhang et al.
33
with
permission from the American Chemical Society.)
We have devised robust dual-responsive polymersomes based on a
temperature-sensitive PEO-b-poly(acrylic acid)-b-poly(N-isopropylacrylamide)
(PEO-PAA-PNIPAM) triblock copolymer and crosslinked with cystamine via
carbodiimide chemistry.
34
The crosslinked polymersomes, while showing
remarkable stability against dilution and decrease of temperature, were
otherwise rapidly dissociated into monomers under reductive conditions
mimicking an intracellular environment. These polymersomes provided
efficient protein loading and triggered intracellular protein release, resulting
in appreciable apoptosis of cancer cells.
35
Grubbs et al. reported that ABC
triblock copolymers with PEO as the A block, temperature-sensitive PNIPAM
or poly(ethylene oxide-stat-butylene oxide) as the B block, and polyisoprene as
the C block underwent reversible transitions from spherical micelles to
polymersomes upon increasing the temperature to above their lower critical
solution temperature (LCST).
36,37
Kim et al. recently reported monosacchar-
ide-responsive polymersomes for controlled release of insulin by sugars under
physiologically relevant pH conditions.
38
Dmochowski et al. prepared photoactive composite polymersomes by
incorporating horse spleen ferritin (HSF) in the aqueous interior and a
bis[(porphinato)zinc] (PZn
2
) chromophore in the membrane of PEO-b-PBD
block copolymer vesicles.
39
The polymersomes were deformed and destructed
on the minute timescale upon exposure to near-UV to near-IR light. Meier
et al. developed photosensitive polymersomes based on the block copolymer
PMCL
76
-ONB-PAA
16
with the light-sensitive nitrobenzene (ONB) group in
between the two blocks. Under UV irradiation the ONB groups could be
cleaved,
resulting
in
polymersome
disruption
and
the
release
of
the
encapsulated fluorescein and proteins (Figure 6.5).
40
