Biomedical Engineering Reference
In-Depth Information
ligands at the periphery of H40 play a significant role in active targeting at the
dangerous cancer cells.
5.3.3 Imaging
During the clinical drug research and development phase, there are narrow
choices for evaluating pharmaceutical and pharmacological properties of new
drugs. Among them, molecular imaging, which aims at direct/indirect
visualization of biomarkers and biological processes in living organisms,
becomes a robust tool to survey in vivo drug behavior during both the
preclinical and clinical phases of discovery and development. Hence, the
combination of anticancer therapy along with real time in vivo imaging of the
targeted cancer cells is very promising for delivery systems in the clinical arena.
Through this noninvasive functionalization, the determination of therapeutic
responses of the HBP-based delivery systems can be detected and tracked in
vivo anytime, which is conducive to pharmacokinetic research. The imaging
functionalization renders the HBP-based delivery system broader applications
for observing and further modulating the delivery system in vivo. In fact, the
panorama of the physiological environment and the concrete process of
metabolism in tumor tissues can be viewed by means of molecular imaging.
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Likewise, proper labeling of these HBP delivery systems allows noninvasive
and continuous visualization and tracking of their delivery kinetics and
biodistribution in vivo. Generally speaking, optical probes or contrast agents of
imaging includes quantum dots (e.g. CdS and CdTe), organic dyes (e.g. near-
infrared fluorescent molecules), bioluminescent proteins (green fluorescent
protein), and conjugated polymers. How to design these components into
HBP-based delivery systems requires reasonable methods. Blue photolumines-
cence was monitored in an aqueous solution of biodegradable hyperbranched
poly(amino ester)s by Liu et al., which is an inherent merit of these HBPs.
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Chen et al. also synthesized the luminescent hyperbranched poly(amido
amine)s (HPAMAMs).
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Different amounts of b-cyclodextrin (b-CD) were
fastened onto the terminal of HPAMAMs by Michael addition, thus obtain-
ing HPAMAM-CDs. Owing to the existence of numerous amino groups,
HPAMAM-CDs could be exploited as nonviral gene delivery vectors, and
the corresponding gene transfection could be visualized by utilization of the
HPAMAM-CDs' photoluminescence. As expected, the cellular uptake and gene
transfection processes could be tracked by flow cytometry and CLSM without
any fluorescent labeling. HPAMAM-CDs with numerous amine groups had
high DNA condensation ability, realizing effective gene transfection. Moreover,
the inner cavities of b-CDs in HPAMAM-CDs could encapsulate drugs through
host-guest interaction. Therefore, the HPAMAM-CDs may have potential
application in the combination of gene therapy and chemotherapy, and also
provide the imaging function. There are other approaches to offer visualization
of cancer cells, such as introducing QDs into the cavities of HBPs
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constructing amphiphilic hyperbranched conjugated polymers.
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Although the
