4 research outputs found
Dual-Mode Gold Nanocluster-Based Nanoprobe Platform for Two-Photon Fluorescence Imaging and Fluorescence Lifetime Imaging of Intracellular Endogenous miRNA
Bioimaging is widely used in various fields of modern
medicine.
Fluorescence imaging has the advantages of high sensitivity, high
selectivity, noninvasiveness, in situ imaging, and so on. However,
one-photon (OP) fluorescence imaging has problems, such as low tissue
penetration depth and low spatiotemporal resolution. These disadvantages
can be solved by two-photon (TP) fluorescence imaging. However, TP
imaging still uses fluorescence intensity as a signal. The complexity
of organisms will inevitably affect the change of fluorescence intensity,
cause false-positive signals, and affect the accuracy of the results
obtained. Fluorescence lifetime imaging (FLIM) is different from other
kinds of fluorescence imaging, which is an intrinsic property of the
material and independent of the material concentration and fluorescence
intensity. FLIM can effectively avoid the fluctuation of TP imaging
based on fluorescence intensity and the interference of autofluorescence.
Therefore, based on silica-coated gold nanoclusters (AuNCs@SiO2) combined with nucleic acid probes, the dual-mode nanoprobe
platform was constructed for TP and FLIM imaging of intracellular
endogenous miRNA-21 for the first time. First, the dual-mode nanoprobe
used a dual fluorescence quencher of BHQ2 and graphene oxide (GO),
which has a high signal-to-noise ratio and anti-interference. Second,
the dual-mode nanoprobe can detect miR-21 with high sensitivity and
selectivity in vitro, with a detection limit of 0.91 nM. Finally,
the dual-mode nanoprobes performed satisfactory TP fluorescence imaging
(330.0 ÎĽm penetration depth) and FLIM (Ď„ave = 50.0 ns) of endogenous miR-21 in living cells and tissues. The
dual-mode platforms have promising applications in miRNA-based early
detection and therapy and hold much promise for improving clinical
efficacy
Quench-Shield Ratiometric Upconversion Luminescence Nanoplatform for Biosensing
Upconversion nanoparticles (UCNPs)
possess several unique features,
but they suffer from surface quenching effects caused by the interaction
between the UCNPs and fluorophore. Thus, the use of UCNPs for target-induced
emission changes for biosensing and bioimaging has been challenging.
In this work, fluorophore and UCNPs are effectively separated by a
silica transition layer with a thickness of about 4 nm to diminish
the surface quenching effect of the UCNPs, allowing a universal and
efficient luminescence resonance energy transfer (LRET) ratiometric
upconversion luminescence nanoplatform for biosensing applications.
A pH-sensitive fluorescein derivative and Hg<sup>2+</sup>-sensitive
rhodamine B were chosen as fluoroionphores to construct the LRET nanoprobes.
Both showed satisfactory target-triggered ratiometric upconversion
luminescence responses in both solution and live cells, indicating
that this strategy may find wide applications in the design of nanoprobes
for various biorelated targets
Near Infrared Graphene Quantum Dots-Based Two-Photon Nanoprobe for Direct Bioimaging of Endogenous Ascorbic Acid in Living Cells
Ascorbic
acid (AA), as one of the most important vitamins, participates
in various physiological reactions in the human body and is implicated
with many diseases. Therefore, the development of effective methods
for monitoring the AA level in living systems is of great significance.
Up to date, various technologies have been developed for the detection
of AA. However, few methods can realize the direct detection of endogenous
AA in living cells. In this work, we for the first time reported that
near-infrared (NIR) graphene quantum dots (GQD) possessed good two-photon
fluorescence properties with a NIR emission at 660 nm upon exciting
with 810 nm femtosecond pulses and a two-photon (TP) excitation action
cross-section (δΦ) of 25.12 GM. They were then employed
to construct a TP nanoprobe for detection and bioimaging of endogenous
AA in living cells. In this nanosystem, NIR GQDs (NGs), which exhibited
lower fluorescence background in living system to afford improved
fluorescence imaging resolution, were acted as fluorescence reporters.
Also CoOOH nanoflakes were chosen as fluorescence quenchers by forming
on the surface of NGs. Once AA was introduced, CoOOH was reduced to
Co<sup>2+</sup>, which resulted in a “turn-on” fluorescence
signal of NGs. The proposed nanoprobe demonstrated high sensitivity
toward AA, with the observed LOD of 270 nM. It also showed high selectivity
to AA with excellent photostability. Moreover, the nanoprobe was successfully
used for TP imaging of endogenous AA in living cells as well as deep
tissue imaging
Bispyrene–Fluorescein Hybrid Based FRET Cassette: A Convenient Platform toward Ratiometric Time-Resolved Probe for Bioanalytical Applications
Pyrene
excimer possesses a large Stokes shift and long fluorescence
lifetime and has been widely applied in developing time-resolved biosensing
systems to solve the autofluorescence interference problems in biological
samples. However, only a few of pyrene excimer-based small molecular
probes have been reported so far. Ratiometric probes, on the other
hand, can eliminate interferences from environmental factors such
as instrumental efficiency and environmental conditions by a built-in
correction of the dual emission bands but are ineffective for endogenous
autofluorescence in biosystems. In this work, by combining the advantages
of time-resolved fluorescence technique with ratiometric probe, we
reported a bispyrene–fluorescein hybrid FRET cassette (<b>PF</b>) as a novel ratiometric time-resolved sensing platform
for bioanalytical applications, with pH chosen as a biorelated target.
The probe <b>PF</b> showed a fast, highly selective, and reversible
ratiometric fluorescence response to pH in a wide range from 3.0 to
10.0 in buffered solution. By employing time-resolved fluorescence
technique, the pH-induced fluorescence signal of probe <b>PF</b> can be well-discriminated from biological autofluorescence background,
which enables us to detect pH in a range of 4.0–8.0 in cell
media within a few seconds. It has also been preliminarily applied
for ratiometric quantitative monitoring of pH changes in living cells
with satisfying results. Since many fluorescein-based fluorescence
probes have been developed, our strategy might find wide applications
in design ratiometric time-resolved probes for detection of various
biorelated targets