Hollow Nanocapsules in Biomedical Imaging Applications - Nanotechnology for Biomedical Imaging and Diagnostics - page 100

drug carriers for intracellular and intranuclear drug delivery but also act as a contrast
agent in cancer cell imaging and in lighting up the nucleus, which results in a type of
polymer hybrid nanosphere that can execute tumor cell imaging and anticancer drug
delivery at the same time [90].
Polymersomes based on polyanionic block copolymers labeled with a NIRF
were obtained by the Discher group [91] to quantify biodistribution in live mice and
excised organs. It was shown that NIRF allows imaging of polymersomes in freshly
excised organs using wavelengths available on any epifluorescence microscope.
And additionally, authors mentioned that method allowed for the observation of the
interaction between NIRF-labeled carriers and live cells in their native tissue
microenvironment.
Novel polymer-lipid hybrid nanovesicles were produced from the aqueous coas-
sembly of the diblock copolymer, poly(ethylene oxide)-block-polybutadiene (PEO-
PBD), and the phospholipid, hydrogenated soy phosphatidylcholine (HSPC) [92].
The PEg-based vesicles were functionalized with either folic acid or anti-HER2/neu
affibodies as targeting ligands to confer specificity for cancer cells. Authors showed
that nanovesicles prepared from polymer-lipid blends led to significant improve-
ment in cell binding compared to nanovesicles prepared from block copolymer alone
in both in vitro cell studies and murine tumor models.
Hydrophobically modified maghemite (γ-Fe 2 O 3 ) nanoparticles were encapsulated
within the membrane of poly(trimethylene carbonate)-b-poly(l-glutamic acid)
(PTmC-b-PgA) block copolymer vesicles using a nanoprecipitation process [93].
These superparamagnetic hybrid self-assemblies display enhanced contrast prop-
erties that open potential applications for mRI. They can also be guided in a magnetic
field gradient. The feasibility of controlled drug release by radio-frequency magnetic
hyperthermia was demonstrated in the case of encapsulated DOX molecules, show-
ing the viability of the concept of magneto-chemotherapy. These magnetic polymer-
somes can be used as efficient multifunctional nanocarriers for combined therapy
and imaging.
Authors [94] demonstrated how a membrane-impermeable Ru II -based light-switch
complex that usually binds to nuclear DNA can be successfully rerouted to specifi-
cally target mitochondria in live cells by employing a biocompatible, pH-sensitive
polymersome vector.

4.5 coNclusioNs

The main focus of this chapter discussion was polymer capsules with high aspect
ratio of their diameters to thickness of the walls. The small thickness of the walls is
critical for increasing the payload capacity of NCs and for rapid mass transfer of
molecules through the capsule shell. Vesicle-templated synthesis is particularly suit-
able for creation of NCs with nanometer-thin walls and controlled permeability
characteristics.
The LBL approach is an attractive approach to the fabrication of well-defined
microcapsules, and starting materials are typically commercially available. One