Biomedical Engineering Reference
In-Depth Information
50 wt% of PLGA in the micelle shell, a retardation of drug release is obvious
because of increased coverage of the PPO core by PLGA domains and
decreased PEG channels. The observed channel effect induced by the phase
separation of micellar coronas is interesting, because the channels can be
constructed and destructed within a narrow pH range without losing colloidal
stability.
Oral administration of ionic drugs generally encounters significant
fluctuation in plasma concentration due to the large variation of pH value
in the gastrointestinal tract and the pH-dependent solubility of ionic drugs.
Polymeric complex micelles with charged channels on the surface provided an
effective way to reduce the difference in the drug release rate upon change in
pH value. Shi et al.
22
reported complex micelles with charged channels for
controlled release of ionic drugs (Figure 9.15). The complex micelles were
prepared by self-assembly of PCL-b-PAsp and PCL-b-PNIPAM in water at
room temperature, with PCL as the core and PAsp/PNIPAM as the mixed
d
n
4
y
3
n
g
|
7
Figure 9.15
(A) Illustration of the release of ibuprofen from PCL-b-PAsp/PCL-b-
PNIPAM complex micelles at 37 uC. (B) Illustration of the contraction
of PAsp chains of PCL-b-PAsp/PCL-b-PNIPAM complex micelles due
to the decrease of pH values.
22
