Biomedical Engineering Reference
In-Depth Information
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Figure 9.3
Ibuprofen release profiles of different micelles at 38 uC. Curves 1, 2, and 3
correspond to micelles with only PEG in the corona but different ratios of
4VP to AA units as 0.7, 1.0, and 1.4, respectively. Curves 4, 5, and 6 are
the release profiles of complex micelles with a mixed corona; the weight
content of PEG-b-P4VP in curves 4, 5, and 6 are 30, 50, and 70%,
respectively.
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micelles without a collapsed PNIPAM shell the variation of 4VP/AA ratios did
not have a marked influence on the release profiles, which demonstrates a good
and similar permeability of the P4VP/PAA complex layer with different
compositions. However, a distinct decrease of drug release rate was observed
in the presence of collapsed PNIPAM, which covered the P4VP/PAA surface
and blocked the diffusion of drugs. Only the PEG channels acted as a
passageway for drug release. An increase in PNIPAM content resulted in a
decrease of drug release rate due to increased coverage of the P4VP/PAA
surface and a decreased amount of PEG channels.
Shell crosslinking of the drug-loaded micelles is frequently used to enhance
their stability during blood circulation, prevent premature drug release, endow
them with programmed disassembly of the nanocarriers, and also allow drug
release at target sites. Wooley et al.
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synthesized a series of shell-crosslinked
knedel-like (SCK) nanoparticles for use as multifunctional imaging and
therapeutic agents. The SCKs were constructed by a procedure that involved
the supramolecular assembly of amphiphilic block copolymers into micelles,
followed by covalent crosslinking throughout the shell layer. SCKs have been
investigated as candidates for targeted biomedical applications due to their
variable compositions, tunable sizes, and exceptional stability to avoid
spontaneous disassembly at concentrations below the critical micelle concen-
tration (CMC) or under challenging conditions as occur in vivo.
Wooley et al.
10
also reported cationic shell-crosslinked knedel-like (cSCK)
nanoparticles
(Figure 9.4)
for
highly
efficient
gene
and
oligonucleotide
