Biomedical Engineering Reference
In-Depth Information
distribution study of C-dots. Following tail vein injection, mice were harvested
and frozen sections of different organs were obtained. Bright blue fluorescence of
C-dots was visible in heart, liver, spleen, lung, kidney, intestine as well as in brain
at 6, 16, and 24 h post injection. Out of these, spleen had the brightest blue fluo-
rescence, indicating more uptake. Moreover, the above studies establish the fact
that C-dots follow the same translocation pathway as reported for PEGylated nan-
oparticles. Hence, it can be concluded that C-dots retain their optical performance
and can be used for non-invasive in vivo imaging.
4.2 C-Dots as Theranostic Agents
There have been quite a few reports on the use of C-dots as theranostic agents.
C dots have the ability to sneak through the biological membranes with ease and
deliver the desired therapeutic agent either directly or after some surface modifica-
tion. Electrostatically coated C-dots with a cationic polymer, PEI for enabling the
endosomal escape mediating its delivery in cytoplasm and nucleus. Further, these
were complexed with plasmid DNA (pDNA) for executing gene transfection and
expression. Confocal microscopy images revealed that PEI coated C-dots were
able to accumulate inside the cytoplasm and nucleus and delivered the pDNA to
HeLa cells (Fuller et al. 2008). In yet another study, PEI functionalized carbon
dots (CD-PEI) were used for simultaneous gene delivery and bioimaging. CD-PEI
was able to condense the pDNA in varying weight ratios and hence successfully
transfected COS-7 and HeLa cells. Moreover, the CD-PEI hybrid assembly had
lower cytotoxicity and comparable gene expression relative to control PEI (Liu
et al. 2012). Besides, the fluorescence of C-dots has been used to monitor the
association/dissociation of polymeric carrier/pDNA complex during transfection.
The strategy involved the use of gold (Au) nanoparticles for quenching the fluo-
rescence of C-dots. The surface of C-dots/Au complex was conjugated with PEI.
Association of the whole complex with pDNA resulted in quenching of C-dots
fluorescence. Dissociation of the complex accompanied by the release of pDNA
resulted in fluorescence recovery of C-dots. This enabled the real-time monitoring
of cellular trafficking through simple fluorescence microscopy (Kim et al. 2013).
C-dots have also been shown to have cancer inhibition activity along with the
bioimaging properties. As-prepared C-dots from green tea tend to inhibit growth
of breast cancer cell lines such as MCF-7 and MDA-MB-231 in a dose dependent
manner and showed less toxicity towards MCF-10A normal cells. The production
of reactive oxygen species (ROS) was considered to be the main reason behind
cancer inhibition effect of C-dots. With an increase in C-dots concentration, cel-
lular levels of H
2
O
2
increased and resulted in induction of apoptosis which ulti-
mately led to the killing of cancer cells (Hsu et al. 2013). C-dots prepared from
ginger juice were shown to have anti-cancer activity against HepG2 cancer cells
and low cytotoxicity towards normal cells such as MCF-10A and FL83B cells.
IC50 value of C-dots on HepG2 cells was reported to be 0.35 mg/mL. Western
