Biomedical Engineering Reference
In-Depth Information
10 mmol L
21
dithiothreitol (DTT), which mimic the reductive intracellular
environment after uptake by cells. Cell viability tests indicated that the
bioinspired PC-based micelles showed excellent biocompatibility, thus
promising great potential for applications in the field of nanocarrier systems.
d
n
4
y
3
n
g
|
7
10.4 CBMA-Based Polymers for Drug Delivery
Little attention has been paid to CB-based polymers in the area of
hemocompatible materials in recent years. However, their easy processing,
extraordinary stability, and the abundant carboxylate anions of PCBs for the
attachment of targeting ligands, therapeutic drugs, and diagnostic labels
through conventional NHS/EDC chemistry make PCBs ideal candidates for
''theranostics''. If the PC-based polymer could be considered as a mimic of cell
membranes, CB-based polymers should be a mimic of soluble proteins. The
COO
2
group is the key negative group on protein surfaces, while NH
3
+
is
major positive group to balance the negative charge. Although the CBMA-
based polymer mainly provides charge by the quaternary ammonium group, it
has been proved that the positive charge from other types of amine groups also
could form materials to resist nonspecific protein adsorption.
60
Remarkably,
the advantage in functionalization of CB-based polymers is superior to other
''nonfouling'' materials, even in the category of zwitterionic materials. The
functional groups, carboxylate anions, are available abundantly and always
stay at the top of the protection layer of CBMA-based polymers. This is
different from the additional immobilizable units in MPC-based polymers,
where the amount and surface abundance of the immobilizable units always
need to be considered, as well as the ''nonfouling'' property altered by the
leftover groups.
To demonstrate these advantages, the high stability and targeting efficiency
of CB-protected nanoparticles (NPs) has been demonstrated by Cao et al.
18
They designed and developed PLGA-PCB block copolymers that self-
assemble into NPs with a PLGA core and a PCB shell (Figure 10.5). The
strong hydration of zwitterionic CBs and the sharp hydrophilicity/hydro-
phobicity difference between the PLGA core and the PCB shell give the NP
systems high stability in biological media. In their work, no size increase of
PLGA-PCB NPs in a phosphate buffered saline (PBS) solution of 10 wt%
bovine serum albumin (BSA) or 100% fetal bovine serum (FBS) solution at 37
uC was observed during the 13-hour study, while unmodified PLGA NPs
severely aggregated immediately after mixing with these media (Figure 10.5).
Furthermore, a long-term study of PLGA-PCB NPs showed that these
particles maintain their original size over 5 days in both 10 wt% BSA and
100% FBS media.
Zhang et al.
61
prepared a multifunctional and degradable nanogel based on
pCBMA. The nanogels encapsulating both a model drug (fluorescently labeled
dextran) and an imaging reagent (monodisperse Fe
3
O
4
nanoparticles) have a
hydrodynamic size of about 110 nm in saline solution and their size remained
