4 research outputs found
Structure-Switching Aptamer Triggering Hybridization Chain Reaction on the Cell Surface for Activatable Theranostics
The ability to probe low-abundance
biomolecules or transport a
high-load drug in target cells is essential for biology and theranostics.
We develop a novel activatable theranostic approach by using a structure-switching
aptamer triggered hybridization chain reaction (HCR) on the cell surface,
which for the first time creates an aptamer platform enabling real-time
activation and amplification for fluorescence imaging and targeting
therapy. The aptamer probe is designed not to initiate HCR in its
free state but trigger HCR on binding to the target cell via structure
switching. The HCR not only amplifies fluorescence signals from a
fluorescence-quenched probe for activatable tumor imaging but also
accumulates high-load prodrugs from a drug-labeled probe and induces
its uptake and conversion into cisplatin in cells for selective tumor
therapy. An in vitro assay shows that this approach affords efficient
signal amplification for fluorescence detection of target protein
tyrosine kinase-7 (PTK7) with a detection limit of 1 pM. Live cell
studies reveal that it provides high-contrast fluorescence imaging
and highly sensitive detection of tumor cells, while renders high-efficiency
drug delivery into tumor cells via an endocytosis pathway. The results
imply the potential of the developed approach as a promising platform
for early stage diagnosis and precise therapy of tumors
Graphitic Carbon Nitride Nanosheets-Based Ratiometric Fluorescent Probe for Highly Sensitive Detection of H<sub>2</sub>O<sub>2</sub> and Glucose
Graphitic carbon
nitride (g-C<sub>3</sub>N<sub>4</sub>) nanosheets, an emerging graphene-like
carbon-based nanomaterial with high fluorescence and large specific
surface areas, hold great potential for biosensor applications. Current
g-C<sub>3</sub>N<sub>4</sub> nanosheets based fluorescent biosensors
majorly rely on single fluorescent intensity reading through fluorescence
quenching interactions between the nanosheets and metal ions. Here
we report for the first time the development of a novel g-C<sub>3</sub>N<sub>4</sub> nanosheets-based ratiometric fluorescence sensing strategy
for highly sensitive detection of H<sub>2</sub>O<sub>2</sub> and glucose.
With <i>o</i>-phenylenediamine (OPD) oxidized by H<sub>2</sub>O<sub>2</sub> in the presence of horseradish peroxidase (HRP), the
oxidization product can assemble on the g-C<sub>3</sub>N<sub>4</sub> nanosheets through hydrogen bonding and π–π stacking,
which effectively quenches the fluorescence of g-C<sub>3</sub>N<sub>4</sub> while delivering a new emission peak. The ratiometric signal
variations enable robust and sensitive detection of H<sub>2</sub>O<sub>2</sub>. On the basis of the glucose converting into H<sub>2</sub>O<sub>2</sub> through the catalysis of glucose oxidase, the g-C<sub>3</sub>N<sub>4</sub>-based ratiometric fluorescence sensing platform
is also exploited for glucose assay. The developed strategy is demonstrated
to give a detection limit of 50 nM for H<sub>2</sub>O<sub>2</sub> and
0.4 ÎĽM for glucose, at the same time, it has been successfully
used for glucose levels detection in human serum. This strategy may
provide a cost-efficient, robust, and high-throughput platform for
detecting various species involving H<sub>2</sub>O<sub>2</sub>-generation
reactions for biomedical applications
Tumor-Targeted Graphitic Carbon Nitride Nanoassembly for Activatable Two-Photon Fluorescence Imaging
Unique
physicochemical characteristics of graphitic carbon nitride
(g-CN) nanosheets suit them to be a useful tool for two-photon fluorescence
bioimaging. Current g-CN nanosheets based imaging probes typically
use the “always-on” design strategies, which may suffer
from increased fluorescence background and limited contrast. To advance
corresponding applications, g-CN nanosheets based activatable two-photon
fluorescence probes remain to be explored. For the first time, we
developed an activatable two-photon fluorescence probe, constructed
from a nanoassembly of g-CN nanosheets and hyaluronic acid (HA)–gold
nanoparticles (HA–AuNPs), for detection and imaging of hyaluronidase
(HAase) in cancer cells. The deliberately introduced HA in our design
not only functions as the buffering layer for stabilizing AuNPs and
inducing corresponding self-assembly on g-CN nanosheets but also as
a pilot for targeting HA receptors overexpressed on cancer cell surfaces.
Our results show that the developed nanoassembly enables specific
detection and activatable imaging of HAase in cancer cells and deep
tissues, with superb signal-to-background ratio and high sensitivity.
This nanoassembly can afford a promising platform for highly specific
and sensitive imaging of HAase and for related cancer diagnosis
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Enhancement of the Intrinsic Peroxidase-Like Activity of Graphitic Carbon Nitride Nanosheets by ssDNAs and Its Application for Detection of Exosomes
The
present work investigates the capability of single-stranded
DNA (ssDNA) in enhancing the intrinsic peroxidase-like activity of
the g-C<sub>3</sub>N<sub>4</sub> nanosheets (NSs). We found that ssDNA
adsorbed on g-C<sub>3</sub>N<sub>4</sub> NSs could improve the catalytic
activity of the nanosheets. The maximum reaction rate of the H<sub>2</sub>O<sub>2</sub>-mediated TMB oxidation catalyzed by the ssDNA-NSs
hybrid was at least 4 times faster than that obtained with unmodified
NSs. The activity enhancement could be attributed to the strong interaction
between TMB and ssDNA mediated by electrostatic attraction and aromatic
stacking and by both the length and base composition of the ssDNA.
The high catalytic activity of the ssDNA-NSs hybrid permitted sensitive
colorimetric detection of exosomes if the aptamer against CD63, a
surface marker of exosome, was employed in hybrid construction. The
sensor recognized the differential expression of CD63 between the
exosomes produced by a breast cancer cell line (MCF-7) and a control
cell line (MCF-10A). Moreover, a similar trend was detected in the
circulating exosomes isolated from the sera samples collected from
breast cancer patients and healthy controls. Our work sheds lights
on the possibility of using ssDNA to enhance the peroxidase-like activity
of nanomaterials and demonstrates the high potential of the ssDNA-NSs
hybrid in clinical diagnosis using liquid biopsy