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Crosstalk between the lysosome and the endoplasmic reticulum (ER) is essential for maintaining intracellular homeostasis and normal physiological activities. However, simultaneously visualizing the lysosome and ER by using a single fluorescent probe is of considerable significance and challenge. In this work, we developed a near-infrared (NIR) pH probe (F–CCOH) by introducing 7-hydroxycoumarin into the curcumin difluoroboron skeleton. The F–CCOH probe presented strong red emission (630 nm) under acidic conditions and NIR emission (755 nm) under basic conditions, which was attributed to the deprotonation of the hydroxyl group on coumarin. Moreover, by monitoring changes in the fluorescent intensity of F–CCOH in two channels, the pH variety of the lysosomes and ER in living cells can be visualized simultaneously. The experimental results showed that pH changes in the lysosome and ER were opposite during dexamethasone-induced apoptosis. This finding is extremely valuable for revealing the crosstalk between lysosome and ER in physiological activities. • F–CCOH exhibits red emission (630 nm) and near-infrared emission (755 nm) under different pH. • F–CCOH can simultaneously target lysosome and endoplasmic reticulum (ER) in living cells. • The pH changes in the lysosome and ER were opposite during dexamethasone-induced apoptosis. [ABSTRACT FROM AUTHOR]

SO 2 and its derivatives (HSO 3 −, SO 3 2−) play a significant important role in many industries and organisms. Based on coumarin and benzopyranose, a promising NIR ratiometric fluorescent probe BAOA (11-oxo-2,2′,3,3′,6,7,7′,8′-octahydro -1H,1′H,5H,6′H,11H- [10,12′-bipyrano [2,3-f] pyrido [3,2,1-ij] quinolin]-13′-ium perchlorate) was designed and developed to detect HSO 3 − rapidly and sensitively. The sensing mechanism was Michael addition reaction, in which, strongly nucleophilic HSO 3 − attacked carbon-carbon double bonds and BAOA-HSO 3 was formed. A superior linear calibration curve between the fluorescence ratio I 490 /I 722 and concentrations of HSO 3 − was obtained in the range of 1.25–8.75 μmol/L and the LOD was figured out as 63.0 nmol/L. Cell experiments showed that BAOA could not only locate mitochondria, lysosomes, ER and Golgi but also detect exogenous HSO 3 − in living cells. A promising NIR ratiometric fluorescent probe for HSO 3 − was designed, which sensing mechanism was nucleophilic HSO 3 − attacking carbon-carbon double bonds resulting from Michael addition reaction. [Display omitted] [ABSTRACT FROM AUTHOR]

Developing nanoplatforms integrating superior fluorescence imaging ability in second near-infrared (NIR-II) window and tumor microenvironment responsive multi-modal therapy holds great potential for real-time feedback of therapeutic efficacy and optimizing tumor inhibition. Herein, we developed a pH-sensitive pyrrolopyrrole aza-BODIPY-based amphiphilic molecule (PTG), which has a balanced NIR-II fluorescence brightness and photothermal effect. PTG is further co-assembled with a vascular disrupting agent (known as DMXAA) to prepare PTDG nanoparticles for combined anti-vascular/photothermal therapy and real-time monitoring of the tumor vascular disruption. Each PTG molecule has an active PT-3 core which is linked to two PEG chains via pH-sensitive ester bonds. The cleavage of ester bonds in the acidic tumor environment would tricker releases of DMXAA for anti-vascular therapy and further assemble PT-3 cores into micrometer particles for long term monitoring of the tumor progression. Furthermore, benefiting from the high brightness in the NIR-II region (119.61 M−1 cm−1) and long blood circulation time (t 1/2 = 235.6 min) of PTDG nanoparticles, the tumor vascular disrupting process can be in situ visualized in real time during treatment. Overall, this study demonstrates a self-assembly strategy to build a pH-responsive NIR-II nanoplatform for real-time monitoring of tumor vascular disruption, long-term tracking tumor progression and combined anti-vascular/photothermal therapy. [ABSTRACT FROM AUTHOR]

A new water-soluble fluorescent probe 1 based on hemicyanine dye is designed for selective detection of glutathione (GSH). Probe 1 shows a tremendous colorimetric and ratiometric fluorescence response toward GSH with high selectivity over cysteine/homocysteine. After nucleophilic aromatic substitution reaction with GSH, probe 1 undergoes an intramolecular aldimine condensation that leads to forming a ring, which is accompanied by 107 and 41 nm red-shifts in the absorption and fluorescence spectra, respectively. Subsequent experiments in living cells indicate that probe 1 has a good photostability and response to mitochondrial GSH level in a ratiometric manner. [ABSTRACT FROM AUTHOR]

Real-time monitoring vascular responses is crucial for evaluating the therapeutic effects of vascular-targeted photodynamic therapy (V-PDT). Herein, we developed a highly-stable and bright aggregation induced emission (AIE) fluorophore (PTPE3 NP) for dynamic fluorescence (FL) imaging of vascular dysfunction beyond 1300 nm window during V-PDT. The superior brightness (ϵ max Φ f>1000 nm ≈ 180.05 M−1 cm−1) and high resolution of PTPE3 NP affords not only high-clarity images of whole-body and local vasculature (hindlimbs, mesentery, and tumor) but also high-speed video imaging for tracking blood circulation process. By virtue of the NPs' prolonged blood circulation time (t 1/2 ≈ 86.5 min) and excellent photo/chemical (pH, RONS) stability, mesenteric and tumor vascular dysfunction (thrombosis formation, vessel occlusion, and hemorrhage) can be successfully visualized during V-PDT by FL imaging for the first time. Furthermore, the reduction of blood flow velocity (BFV) can be monitored in real time for precisely evaluating efficacy of V-PDT. These provide a powerful approach for assessing vascular responses during V-PDT and promote the development of advanced fluorophores for biological imaging. [ABSTRACT FROM AUTHOR]

Carbon dots (CDs) have emerged as promising nanomaterials for bioimaging-guided photodynamic therapy (PDT). However, designing red-emissive CDs (RCDs) with tunable type I and type II reactive oxygen species (ROS) generation to simultaneously meet PDT applications in aerobic and hypoxic scenarios still remain major challenges. Herein, three types of RCDs with maximum emission at approximately 680 nm are successfully prepared. It is noteworthy that they exhibit the adjustable ROS production with equal superoxide anion (via type I PDT) and incremental singlet oxygen (via type II PDT). Detailed structural and optical characterizations along with theoretical calculation reveal that the unique type I/II ROS formation mainly depends on the core sizes and surface states of RCDs, which determine their identical redox potentials and tapering energy gaps between singlet- and triplet states, respectively. Additionally, due to the inherent mitochondria targeting capability, RCDs enable themselves to induce cell programmed death via activating mitochondrion-mediated apoptotic pathways. This work exploits the unprecedented RCDs with tunable type I and type II ROS generation that could ensure highly efficient tumor eradication both in vitro and in vivo, even under the harsh tumor microenvironment, providing a new prospect for CDs as nanophotosensitizers to conquer the limitations of single type PDT. Red emissive carbon dots with tunable reactive oxygen species generation are prepared to achieve highly efficient fluorescence imaging-guided type I/II photodynamic therapy via activating mitochondrion-mediated apoptotic pathways of cancer cells, providing a new prospect for carbon dots as nanophotosensitizers to conquer the limitations of single type PDT. [Display omitted] [ABSTRACT FROM AUTHOR]

Two asymmetrical benzoxanthene dyes (BP-1 and BP-2) were designed and synthesized by a convenient one-step procedure from naphthaldehyde and m -aminophenol precursors. These dyes showed long-wavelength absorption, near-infrared emission (>650 nm), and large Stokes shifts (>90 nm) because of the asymmetrical introduction of the benzene ring into the xanthene structure. BP-1 exhibited high fluorescence quantum yield in organic solvents, whereas BP-2 showed very weak fluorescence due to the photoinduced electron transfer of 9-substituted groups. Cell experiments indicated that BP-1 with crescent-shape structure showed lower cytotoxicity and higher photostability than BP-2 and could rapidly stain RNA in nucleoli at low concentration. [Display omitted] • Two asymmetrical benzoxanthene dyes were synthesized by a convenient one-step procedure. • The dyes showed long-wavelength absorption, near-infrared emission and large Stokes shifts. • BP-1 could stained RNA in nucleoli rapidly with low cytotoxicity and good photostability. • BP-2 showed a very weak fluorescence and cytotoxicity due to 9-substituted groups. [ABSTRACT FROM AUTHOR]

Solvents exhibit different color reactions via regulation of the structure, kinetics, and charge distribution of organic compound molecules. In recent years, solvatochromic probes have good application prospects in the fields of chemistry and biology. In this work, we synthesized three fluorescent probes (PBIC–C, PAIC-C, PPIC-C) sensitive to solvent polarity. We have studied the photophysical properties (spectra, quantum yield, and fluorescence lifetime under different solvents) of these probes. The isomerization nature was verified by nuclear magnetic titration. In order to further confirm our guess, we also performed theoretical calculations, and the results were roughly the same as the experimental results. In addition, cell imaging tests revealed that the designed probes could be used as dual intracellular mitochondria/lysosome-targeting fluorescent probes for biological applications. [Display omitted] • The probes exhibit sharp color changes in different polar solvents. • The probes show relatively high fluorescence quantum yields. • The probes achieve dual targeting of mitochondrials and lysosomes. [ABSTRACT FROM AUTHOR]