Biomedical Engineering Reference
In-Depth Information
Fig. 4
(
a
) cryo-TEM images of vesicle wall structures at pH 10.4, 8.53, 7.63, 6.22, 5.65, and 3.40,
respectively; (
b
) schematic illustrations of the three-layered wall structures at corresponding pH
values; (
c
) the chemical structure of the triblock copolymer used to form the breathing polymer-
somes. (Reproduced from ref Yu et al.
2009
)
The increase of the thickness of the two PS layers is a result of an increasing
incompatibility and an accompanying sharpening of the interface between the PS
layers and the PDEA layer. Starting at a pH slightly below 6, progressive swelling
of the PDEA layer with decreasing pH induces a cracking of the two PS layers and
also a sharp increase of the vesicle size and the wall thickness.
For applications in chemical and gene therapy, pH-induced release based on poly-
base blocks may permit the delivery of drugs and genes into the cytosol via endolyso-
somal acidification and escape. Battaglia et al. recently prepared biomimetic pH
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