Intracellular pH is closely related with many biological processes, including cellular proliferation, apoptosis, endocytic processes, signal transduction, and enzymatic activity. The use of fluorescent probes has become an essential method for intracellular pH detection, but existing fluorescent probes have substantial limitations, such as requiring tedious synthetic preparation, suffering from an inappropriate response range and insufficiently long emission wavelength. In this work, a red emissive two‐photon fluorescence probe based on carbon dots (pH‐CDs) is fabricated using a facile one‐pot hydrothermal method for the monitoring of intracellular pH. pH‐CDs possess a variety of superior properties, including high selectivity, excellent photostability, and low cytotoxicity. Furthermore, they exhibit a pH‐sensitive response in the range of 1.0–9.0 and a linear range of 3.5–6.5, which is desirable for tracking the pH value in living cells. It is demonstrated that the pH‐dependent fluorescence signal is regulated via switching between aggregation and disaggregation of CDs. More importantly, pH‐CDs can be successfully applied to sense and visualize pH fluctuation in cells, tissue, and zebrafish. These findings suggest that the as‐prepared pH‐CDs probe has significant potential for practical application in living systems.
Simultaneous imaging of mitochondrial viscosity and hydrogen peroxide in Alzheimer's disease by a single near-infrared fluorescent probe with a large Stokes shift.
A clear elucidation
of a disease-related viscosity change in vivo
is significant yet highly challenging as well. Fluorescence imaging
in the second near-infrared region (NIR-II, 1000–1700 nm) has
gained increasing attention for observation in living organisms, but
a viscosity-activatable fluorescent probe emitting at this region
remains a vacancy. Herein, we report the first panel of a viscosity-activated
NIR-II emissive fluorescent probe WD-X. By embedding
different substituents into the WD-X platform and screening,
we obtained an ideal probe, WD-NO
2
, which displayed the best combination of properties, including a
31-fold fluorescence enhancement in response to viscosity, insensitivity
to environments (pH, polarity), and relatively high quantum yield
(1.6% in glycerol). WD-NO
2
was
successfully applied to track the variation of viscosity in diabetes-induced
liver injury in vivo.
Activatable
second near-infrared (NIR-II) fluorescent probes that
can be lighted up by specific targets have attracted great attention
because of their high specificity and resolution, which hold great
promise in deep-tissue imaging. However, such probes were relatively
rarely reported so far, and the emission maximum is still limited
(mainly located at 900–1000 nm). To solve the problem, herein,
we proposed a flexible strategy to modulate the emission wavelength
of NIR-II fluorescent probes, and four proof-of-concept probes (WH-1, WH-2, WH-3, and WH-4) based on D−π-A molecular skeleton were obtained. These
probes can be activated by H2S and the emission maximum
located from 925 to 1205 nm, which was attributed to the cooperation
of elongating the π-conjugated system and enhancing the electron-donating
ability of the donor region. In these probes, WH-3 exhibited
the combination of long excitation/emission (925/1140 nm) and moderate
quantum yield as well as high sensitivity toward H2S, enabling
us to track and image H2S in vivo with
high contrast. We expected that such a molecular design strategy will
become an important approach to developing activatable NIR-II fluorescent
probes with long emission.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.