Cancer stem cells
(CSCs) are progenitor cells that contribute to
treatment-resistant phenotypes during relapse. CSCs exist in specific
tissue microenvironments that cell cultures and more complex models
cannot mimic. Therefore, the development of new approaches that can
detect CSCs and report on specific properties (e.g., stem cell plasticity)
in their native environment have profound implications for studying
CSC biology. Herein, we present AlDeSense, a turn-on fluorescent probe
for aldehyde dehydrogenase 1A1 (ALDH1A1) and Ctrl-AlDeSense, a matching
nonresponsive reagent. Although ALDH1A1 contributes to the detoxification
of reactive aldehydes, it is also associated with stemness and is
highly elevated in CSCs. AlDeSense exhibits a 20-fold fluorescent
enhancement when treated with ALDH1A1. Moreover, we established that
AlDeSense is selective against a panel of common ALDH isoforms and
exhibits exquisite chemostability against a collection of biologically
relevant species. Through the application of surface marker antibody
staining, tumorsphere assays, and assessment of tumorigenicity, we
demonstrate that cells exhibiting high AlDeSense signal intensity
have properties of CSCs. Using these probes in tandem, we have identified
CSCs at the cellular level via flow cytometry and confocal imaging,
as well as monitored their states in animal models.
The mixed-valent oxo-bridged ruthenium complex [(HCO)(NH)Ru(μ-O)Ru(NH)(OCH)], known as Ru360, is a selective inhibitor of mitochondrial calcium uptake. Although this compound is useful for studying the role of mitochondrial calcium in biological processes, its widespread availability is limited because of challenges in purification and characterization. Here, we describe our investigations of three different synthetic methods for the preparation of a functional analogue of this valuable compound. We demonstrate that this analogue, isolated from our procedures, exhibits potent mitochondrial calcium uptake inhibitory properties in permeabilized HeLa cells and in isolated mitochondria.
Detection of nitroxyl (HNO), the transient one-electron reduced form of nitric oxide, is a significant challenge owing to its high reactivity with biological thiols (with rate constants as high as 10 M s). To address this, we report a new thiol-based HNO-responsive trigger that can compete against reactive thiols for HNO. This process forms a common N-hydroxysulfenamide intermediate that cyclizes to release a masked fluorophore leading to fluorescence enhancement. To ensure that the cyclization step is rapid, our design capitalizes on two established physical organic phenomena; the alpha-effect and the Thorpe-Ingold effect. Using this new trigger, we developed NitroxylFluor, a selective HNO-responsive fluorescent probe. Treatment of NitroxylFluor with an HNO donor results in a 16-fold turn-on. This probe also exhibits excellent selectivity over various reactive nitrogen, oxygen, and sulfur species and efficacy in the presence of thiols (e.g., glutathione in mM concentrations). Lastly, we successfully performed live cell imaging of HNO using NitroxylFluor.
Controlled light-mediated delivery of biological analytes can enable the investigation of highly reactivity molecules within living systems. As many biological effects are concentration dependent, it is critical to determine the location, time, and quantity of analyte donation. In this work, we have developed the first photoactivatable donor for formaldehyde (FA). Our optimized photoactivatable donor, photoFAD-3, is equipped with a fluorescence readout that enables monitoring of FA release with a concomitant 139-fold fluorescence enhancement. Tuning of photostability and cellular retention enabled quantification of intracellular FA release through cell lysate calibration. Application of photoFAD-3 uncovered the concentration range necessary for arresting wound healing in live cells. This marks the first report where a photoactivatable donor for any analyte has been used to quantify intracellular release.
Few
xanthene-based near-infrared (NIR) photoacoustic (PA) dyes
with absorbance >800 nm exist. As accessibility to these dyes requires
long and tedious synthetic steps, we designed a NIR dye (XanthCR-880) with thienylpiperidine donors and a xanthene acceptor that is accessible
in 3–4 synthetic steps. The dye boasts a strong PA signal at
880 nm with good biological compatibility and photostability, yields
multiplexed imaging with an aza-BODIPY reference dye, and is detected
at a depth of 4 cm.
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.