Biomedical Engineering Reference
In-Depth Information
When used as drug delivery vehicles, different parts of the CSC micelles play
important roles themselves. The micelle core is used as a reservoir for the
loaded drug. The shell layer is usually endowed with a responsiveness, which is
used to control and/or environmentally trigger drug release. The hydrophilic
corona of PEG either stabilizes the micelles from aggregation or prevents them
from premature clearance in blood circulation.
Shi et al.
7
reported CSC complex micelles as contractive ''nanopumps'' for
thermo-sensitive release of drugs, as shown in Figure 9.2. The complex micelles
were obtained from PS-b-PNIPAM-b-PAA [PAA 5 poly(acrylic acid)]
micelles and PEG-b-P4VP block copolymers via the strong electrostatic
interaction and hydrogen bonding between PAA and P4VP blocks in water.
The PS block formed the core and the PAA/P4VP complex shell functioned as
a semi-permeable membrane which could control the permeation of small
molecules. Between the core and the shell, the large fluid-filled space that was
formed with the thermo-responsive PNIPAM gel could retain the loaded drug
for a long period of time. With increasing temperature, the shrinkage of the
PNIPAM coils pumped the drug out of the complex micelles.
Other CSC complex micelles with surface channels were also reported by Shi
et al.
8
for controlled drug release. An O/W emulsion with an oil phase of
dichloroethane and a PAA surface was prepared and followed by deposition of
PNIPAM-b-P4VP and PEG-b-P4VP through the interaction between PAA
and P4VP. PEG channels were formed upon collapse of PNIPAM above its
lower critical solution temperature (LCST). Ibuprofen was encapsulated by
using a dichloroethane solution of the drug. The PAA/P4VP complex layer was
swollen and permeable for small molecules, while the PEG channels played a
key role in controlling drug release. As indicated in Figure 9.3, for the complex
d
n
4
y
3
n
g
|
7
CSC micelles as contractive ''nanopumps'' for controlled drug release.
7
Figure 9.2
