The design of fluorescent molecular platforms capable of responding to multiple analytes is a topic of great interest. Herein, the use of a Zn -complexed unsymmetrical squaraine dye, Sq-Zn , as a chemical platform for recognizing structurally distinct analytes is reported. The squaraine ring is substituted on one side with a dipicolylamine unit, which acts as the metal ion receptor, whereas the other part of the molecule carries a dibutylaniline moiety, which is an electron donor. The molecular system is unique because it can respond specifically to different types of analytes, namely, atmospheric carbon dioxide, cyclic phosphates, and picric acid. Moreover, the interaction of these analytes can be monitored colorimetrically and fluorimetrically, which favors both qualitative and quantitative analyses. The distinct response towards cyclic and linear phosphates, as well as the selective response towards picric acid, among the various nitroaromatic compounds was achieved with sensitivity at the ppm level. The flexible coordination offered by Zn plays a significant role in the discrimination of these analytes with high specificity. Dye Sq-Zn introduced herein is a single-molecule construct that can be used for the selective and sensitive response towards analytes of environmental and biological relevance.
Organelle-targeted photosensitizers (PSs) having luminescence properties are potential theranostic agents for simultaneous luminescence imaging and photodynamic therapy. Herein, we report a water-soluble luminescent cyclometalated Ir complex, Ir-Bp-Ly, as a lysosome-targeted theranostic probe. Ir-Bp-Ly exhibits exceptional photophysical properties, with good triplet-state quantum yield (0.90), singlet oxygen generation quantum yield (0.71 at pH 4), and long lifetime (1.47 μs). Interestingly, Ir-Bp-Ly localizes mostly in lysosomes due to the presence of morpholine units, suggesting its potential use as a lyso-tracker. Ir-Bp-Ly displays a notable PDT effect in C6 glioma cells, efficiently generating reactive oxygen species owing to close proximity between the energy levels of its triplet state and those of molecular oxygen ( O ). The mechanism of cell death has been studied through caspase-3/7 and flow cytometry analyses, which clearly established the apoptotic pathway.
A two-component hybrid system consisting of organic dye nanoparticles (ash) and a protein (blue) at different ratios allows for the design of narrow range tunable nanoprobes for sensing and imaging of pH variations in live cells through ratiometric signalling.
Fluorescent probes for simultaneous detection of multiple organelle specific analytes in cancer cells are essential for bioimaging applications. During abnormalities in cells, among other important parameters (metal ions, reactive oxygen species (ROS), enzymes, etc.) pH and Zn2+ are also altered in cells. Herein, we report the formation of nanoparticles of the fluorescent molecules based on carbazole‐bipyridine conjugates (CBL1‐3) and their use as nanoprobes to simultaneously detect Zn2+ and pH variations in lysosome. Upon increasing the pH from 4–6, these probes form nanoparticles with increased size and enhanced fluorescence at 510 nm. Among CBL1‐3, nanoparticles of CBL2 upon Zn2+ binding, exhibit pH responsive intensity change only at lysosomal pH window at 610 nm and become silent above pH 7. Fluorescent imaging experiments on cancer cells revealed that the CBL2 nanoprobe is capable of localizing at lysosomes and facilitates the detection of endogenous Zn2+ and pH variations. Furthermore, the lysosomal Zn2+ variation with external stimuli induced programmed cell death was visualized using the nanoprobe.
Organelle‐targeted photosensitizers with luminescence properties are potential theranostic agents for simultaneous imaging and photodynamic therapy. Described herein is a cyclometalated IrIII complex, Ir‐Bp‐Ly, that exhibits high triplet quantum yield and singlet‐oxygen‐generation efficiency. The close‐proximity energy levels between triplet energy states of Ir‐Bp‐Ly and molecular oxygen favors efficient singlet oxygen and reactive oxygen species (ROS) generation. The good lysosomal specificity of Ir‐Bp‐Ly leads to its increased efficacy as a photodynamic therapeutic and imaging agent. More information can be found in the Full Paper by A. Ajayaghosh et al. on page 10999 ff.
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