Biomedical Engineering Reference
In-Depth Information
hydrophilic
(ionic)
hydrophobic
PDP-
b
-PLA (10%)
w/o/w emulsion
protein
PLGA (90%)
PEG-
b
-PLA + PLGA
PLGA
PGK-
b
-PLA + PLGA
Fig. 8 Preparation of biodegradable microspheres entrapping proteins using amphiphilic
PDP-
b
-PLA block copolymers as biodegradable polymeric surfactants, and SEM images of their
cross-sections. Reprinted from [
182
] with permission
drug (paclitaxel; PTX) to liver [
185
]. Saeed et al. reported the ATRP of poly
(ethylene glycol) methacrylate (PEGMA) using PLGA having a bromide terminal
to give PLGA-based amphiphilic block copolymer. They then prepared NSs from
the block copolymer and PLGA, immobilizing a folic acid derivative as a homing
device by click chemistry, and reported that the obtained multifunctional NSs
was useful for gene delivery [
186
]. Liu et al. reported preparation of MSs from
PNIPAAm-
b
-PLA block copolymer containing BSA as model drug, and showed
that the release rate of BSA from the MSs could be accelerated by temperature
change [
187
].
4 Polymer Micelles
Polymer micelles are nanometer sized (usually several tens of nanometers)
self-assembled particles having a hydrophobic core and hydrophilic outer shell
composed of amphiphilic AB- or ABA-type block copolymers, and are utilized
as drug delivery vehicles. The first polymer micelle-type drug delivery vehicle
was made of PEG-
b
-poly(aspartic acid) (PEG-
b
-PAsp), immobilizing the hydro-
phobic anticancer drug DXR [
188
-
191
]. After this achievement by Kataoka et al., a
great amount of research on polymer micelles has been carried out, and there are
several reviews available on the subject [
192
-
194
].
As described above, the most common hydrophilic polymer combined with
aliphatic polyesters to prepare polymer micelles is PEG. Although there have been
many reports on the polymer micelles of PEG-
b
-aliphatic polyesters, only few recent
examples are introduced in this review. Shin et al. reported the therapeutic potential
of PEG-
b
-PLA micelles entrapping multiple anticancer drugs of poor solubility in
