Hydrogen Sulfide Triggered Charge-Reversal Micelles for Cancer-Targeted Drug Delivery and Imaging

Currently, the development of polymeric micelles combining diagnosis and targeted therapy is theoretically and practically significant in cancer treatment. In addition, it has been reported that cancer cells can produce large amounts of hydrogen sulfide (H₂S) and their survival depends on the content of H₂S. In this study, a series of <i>N</i>-(2-hydroxyethyl)-4-azide-1,8-naphthalimide ended amphiphilic diblock copolymer poly­(2-hydroxyethyl methacrylate)-<i>block</i>-poly­(methyl methacrylate) (N₃-Nap-PHEMA-<i>b</i>-PMMA-N₃) micelles were prepared. Around cancer tissues, the N₃-Nap-PHEMA₄₅-<i>b</i>-PMMA₄₂-N₃ micelles exhibited dual characteristics of monitoring H₂S and H₂S triggered charge reversal with the reduction of the azido group. The surface charge of N₃-Nap-PHEMA₄₅-<i>b</i>-PMMA₄₂-N₃ micelles reversed from negative to positive after monitoring H₂S. With H₂S triggered charge reversal, the cellular uptake of DOX-loaded N₃-Nap-PHEMA₄₅-<i>b</i>-PMMA₄₂-N₃ micelles was effectively enhanced through electrostatic attraction mediated targeting, and a fast doxorubicin (DOX) release rate was observed. The MTT assay demonstrated that N₃-Nap-PHEMA₄₅-<i>b</i>-PMMA₄₂-N₃ micelles were biocompatible to HeLa cells, and DOX-loaded N₃-Nap-PHEMA₄₅-<i>b</i>-PMMA₄₂-N₃ micelles showed enhanced cytotoxicity in HeLa cells in the presence of H₂S. Furthermore, in vivo fluorescence imaging and biodistribution experiments revealed that DOX-loaded N₃-Nap-PHEMA₄₅-<i>b</i>-PMMA₄₂-N₃ micelles could provide good tumor imaging and accumulate in tumor tissue. Therefore, N₃-Nap-PHEMA₄₅-<i>b</i>-PMMA₄₂-N₃ micelles can be used as a promising platform for tumor diagnosis and therapy

Discriminating Live and Dead Cells in Dual-Color Mode with a Two-Photon Fluorescent Probe Based on ESIPT Mechanism

Discrimination of live and dead cells is an important task in biological, pathological, medical, and pharmaceutical studies. In this work, we have developed a novel fluorescent probe <b>DACA</b> that can discriminate live and dead cells in a dual-color mode for the first time. <b>DACA</b> can stain dead cells with blue fluorescence peaked at 440 nm, while it can also label live cells with orange emission peaked at 570 nm. Compared with one-color fluorescent probes, such a dual-color probe can efficiently avoid false positive results from cellular autofluorescence and misleading signals brought by inhomogeneous staining, and thus can supply more accurate information in biological applications. By means of <b>DACA</b>, the health status of tumor cells pretreated by H₂O₂ and ultraviolet radiation has been successfully detected and imaged. Moreover, <b>DACA</b> and the hydrolyzed product exhibit excellent two-photon properties. Live and dead cells, as well as the zebrafishes, have been discriminated with dual emission colors under one- and two-photon microscope. These results demonstrate that <b>DACA</b> is a powerful tool for dual-color distinguishing live and dead cells in vitro and in vivo

Two-Photon and Deep-Red Emission Ratiometric Fluorescent Probe with a Large Emission Shift and Signal Ratios for Sulfur Dioxide: Ultrafast Response and Applications in Living Cells, Brain Tissues, and Zebrafishes

Sulfur dioxide (SO₂) is a dangerous environmental pollutant. Excessive intake of it may cause some respiratory diseases and even lung cancer. The development of effective methods for detection of SO₂ is of great importance for the environment and physiology. Herein, we have designed and synthesized a novel two-photon (TP) and deep-red emission ratiometric fluorescent probe (<b>CP</b>) for detection of SO₂. Notably, the novel probe <b>CP</b> exhibited ultrafast response to SO₂ in less than 5 s and displayed a great emission shift (195 nm) and a large emission signal ratio variation (enhancement from 0.1347 to 100.14). In addition, the unique probe was successfully employed for imaging SO₂ not only in the mitochondria of living cells but also in brain tissues and zebrafishes

Dual Site-Controlled and Lysosome-Targeted Intramolecular Charge Transfer–Photoinduced Electron Transfer–Fluorescence Resonance Energy Transfer Fluorescent Probe for Monitoring pH Changes in Living Cells

Acidic pH is a critical physiological factor for controlling the activities and functions of lysosome. Herein, we report a novel dual site-controlled and lysosome-targeted intramolecular charge transfer–photoinduced electron transfer–Fluorescence resonance energy transfer (ICT–PET–FRET) fluorescent probe (CN-pH), which was essentially the combination of a turn-on pH probe (CN-1) and a turn-off pH probe (CN-2) by a nonconjugated linker. Coumarin and naphthalimide fluorophores were selected as donor and acceptor to construct the FRET platform. Hydroxyl group and morpholine were simultaneously employed as the two pH sensing sites and controlled the fluorescence of coumarin and naphthalimide units by ICT and PET, respectively. The sensing mechanism of CN-pH to pH was essentially an integration of ICT, PET, and FRET processes. Meanwhile, the morpholine also can serve as a lysosome-targeted group. By combining the two data analysis approaches of the ratios of the two emission intensities (<i>R</i>) and the reverse ratio <i>R</i>′ (<i>R</i>′ = 1/<i>R</i>), the fluorescent ratio of CN-pH can show proportional relationship to pH values in a very broad range from pH 4.0 to 8.0 with high sensitivity. The probe has been successfully applied for the fluorescence imaging of the lysosomal pH values, as well as ratiometrically visualizing chloroquine-stimulated changes of intracellular pH in living cells. These features demonstrate that the probe can afford practical application in biological systems

Coumarin-Based Turn-On Fluorescence Probe for Specific Detection of Glutathione over Cysteine and Homocysteine

We have prepared a turn-on fluorescent probe for biothiols based on bromoketo coumarin (<b>KC-Br</b>). The emission intensity of the coumarin chromophore is modulated by both the heavy atom effect and internal charge transfer (ICT) process. The probe <b>KC-Br</b> is intrinsically nonfluorescent; however, after being reacted with thiols, the bromide moiety is substituted by the −SH group, which elicits a significant fluorescence increase. We surmised the free −NH₂ group would further react with carbonyl in the Cys/Hcy-substituted intermediate product yielding to Schiff base compound <b>KC-Cys</b>/<b>KC-Hcy</b>, but not in compound <b>KC-GSH</b>. The ICT effect has a stronger influence in compound <b>KC-GSH</b> than that in compound <b>KC-Cys</b>/<b>KC-Hcy</b>, resulting in compound <b>KC-GSH</b> having a stronger fluorescence. Thus, the probe has a good selectivity for GSH over other various biologically relevant species and even two other similar biothiols (Cys/Hcy) and could image glutathione (GSH) in living cells. We expect the design concept presented in this work would be widely used for the design of fluorescent probes for distinguishing among biothiols