Photoactivated In Situ Generation of Near Infrared Cyanines for Spatiotemporally Controlled Fluorescence Imaging in Living Cells

Photoactivation Inducing Multifunctional Coupling of Fluorophore for Efficient Tumor Therapy In Situ

Photoactivatable molecules, with high-precision spatialtemporal control, have largely promoted bioimaging and phototherapy applications of fluorescent dyes. Here, the first photoactivatable sensor (BI) is described that can be triggered by broad excitation light (405-660 nm), which further undergoes intersystem crossing and H-atom transfer processes to forming superoxide anion radicals (O2 -• ) and carbon radicals. Particularly, the photoinduced gain of carbon-centered radicals (BI•) allows for radical-radical coupling to afford the combined crosslink product (BI─BI), which would be oxidized in the presence of O2 -• to produce an extended conjugate system with near infrared emission (820 nm). Besides, the photochemically generated product (Cy─BI) possesses ultra-high photothermal conversion efficiency up to 90.9%, which optimized phototherapy potential. What's more, Western Blot assay reveals that both BI and the photoproduct Cy─BI can efficiently inhibit the expression of CHK1, and the irradiation of BI and Cy─BI further induces apoptosis and ultimately enhances the phototherapeutic effects. Thus, the combination of cell cycle block inducing apoptosis, photodynamic therapy and photothermal therapy treatments significantly suppress solid tumor in vivo antitumor efficacy explorations. This is a novel finding in developing photoactivatable molecules, as well as the broad applicability of photoimaging and phototherapy in tumor-related areas.

Free Radical-Mediated Photocyclization of Triphenylphosphindole Oxides for Photoactivated and Self-Reported Lipid Peroxidation

Photocyclization is demonstrated as a powerful tool for building complicated polycyclic molecules. And efficient photocyclization is competent as an artful strategy to develop photo-responsive smart materials. Herein, an efficient free radical-mediated photocyclization for triphenylphosphindole oxide (TPPIO) derivatives to generate tribenzophosphindole oxide (TBPIO) derivatives at ambient condition is reported. The reaction mechanism and substituent effect on photocyclization efficiency are thoroughly investigated. Additionally, photophysical and photochemical properties of TPPIO and TBPIO derivatives are measured for comparison and deeply deciphered by theoretical calculation. TPPIO derivatives own typical aggregation-induced emission feature but barely generate reactive oxygen species (ROS), while TBPIO derivatives experience aggregation-caused quenching but show efficient Type I ROS generation capacity. Further, in vitro experiments demonstrate that this photo-conversion can efficiently occur in situ in living cells to activate photodynamic therapy (PDT) effect to trigger lipid peroxidation with selective fluorescence "light up" in lipid droplet area under continuous irradiation. This work extends the optoelectronically and biologically interesting phosphindole oxide-containing π-conjugated systems through an efficient synthetic strategy, provides in-depth mechanistic descriptions in the aspects of reaction and property, and further presents their great potentials for photoactivated and self-reported PDT.

Acidic pH-Triggered Live-Cell Lysosome Specific Tracking, Ratiometric pH Sensing, and Multicolor Imaging by Visible to NIR Switchable Cy-7 Dyes

We have demonstrated an efficient synthetic route with crystal structures for the construction of acidic pH-triggered visible-to-NIR interchangeable ratiometric fluorescent pH sensors. This bioresponsive probe exhibits pH-sensitive reversible absorption/emission features, low cytotoxicity, a huge 322 nm bathochromic spectral shift with augmented quantum yield from neutral to acidic pH, high sensitivity and selective targeting ability of live-cell lysosomes with ideal pK_a , off-to-on narrow NIR absorption/fluorescence signals with high molar absorption coefficient at acidic lysosomal lumen, and in-situ live-cell pH-activated ratiometric imaging of lysosomal pH. Selective staining and ratiometric pH imaging in human carcinoma live-cell lysosomes were monitored by dual-channel confocal laser scanning microscope using a pH-activatable organic fluorescent dye comprising a morpholine moiety for lysosome targeting and an acidic pH openable oxazolidine ring. Moreover, real-time tracking of lysosomes, 3D, and multicolor live-cell imaging have been achieved using the synthesized pH-activatable probe.

HClO-Activated Near-Infrared Fluorogenic Aza-BODIPY-Bisferrocene Triad with High Turn-on Ratio for In Vivo Biosensing

Optically monitoring hypochlorous acid (HClO) in living body favors diagnosis and study of inflammatory diseases. However, this has been hampered by limited strategies to develop highly fluorogenic tools in the deep-penetration near-infrared spectrum. Herein, a near-infrared aza-BODIPY-bisferrocene triad Fc₂ -CBDP that unexpectedly achieves an exceptionally sensitive and selective fluorescence turn-on (>220-fold) response toward HClO through single-ferrocene oxidation and boron-alkynyl hydrolysis cascade is reported. Mechanism insight shows that Fc₂ -CBDP features "enhanced charge transfer"-caused quenching due to intramolecular bisferrocene electronic coupling, which is decoupled in the reaction with HClO. The utility of Fc₂ -CBDP for intracellular HClO imaging is evaluated and, more importantly, in vivo high-contrast deep-tissue imaging of lymphatic inflammation and colitis is realized. This work provides new insights into both HClO and ferrocene chemistry, and extends the reach of fluorogenic strategies in the near-infrared biosensing.

Monitoring isoniazid metabolism in vivo using a near-infrared fluorescent probe

As a strong nucleophilic substance, hydrazine is widely used in the fields of agriculture, industry, and medicine. Hydrazine compounds usually exist as intermediates of some drugs. Many drugs, such as isoniazid and carbidopa, produce hydrazine metabolites. Hydrazine is a genotoxic substance, which can cause DNA lesions and cancer via long-term exposure. Therefore, it is very important to monitor the level of hydrazine in the human body with high selectivity and sensitivity. Here, we synthesized a near-infrared (NIR) fluorescent probe Cy-HZ based on the hemicyanine skeleton to visualize the metabolism of the drug isoniazid in vivo. The ester group of the probe reacts with hydrazine to generate Cy-H, causing a change in fluorescence. Here, we studied its absorption and fluorescence spectra, the recognition response to hydrazine, the imaging of exogenous hydrazine in cells and the imaging in mice and further applied the probe to monitor the distribution and metabolism of isoniazid.

Real-Time and High-Fidelity Tracking of Lysosomal Dynamics with a Dicyanoisophorone-Based Fluorescent Probe

The development of high-performance probes that can visualize and track the dynamic changes of lysosomes is very important for the in-depth study of lysosomes. Herein, we report that a dicyanoisophorone-based probe (named DCIP) can be used for high-fidelity imaging of lysosomes and lysosomal dynamics. DCIP can be easily prepared and shows strong far-red to near-infrared emissions centered at 653 nm in water with a huge Stokes shift (224 nm), high quantum yield (Φ = 0.15), high pKa value (∼8.79), and good biocompatibility. DCIP also shows good cell permeability and can label lysosomes rapidly with bright fluorescence without a time-consuming washing process before imaging. DCIP also possesses good photostability and negligible background, making it effective for long-term and high spatiotemporal resolution (0.44 s of exposure) imaging of lysosomes. Moreover, DCIP achieved high-fidelity tracking of lysosomal dynamics at an extremely low concentration (1 nM). Finally, we also demonstrated that DCIP could real-time track the interactions of lysosomes with other organelles (damaged mitochondria as a model) and image the drug-escape processes from lysosomes. All of the results show that DCIP holds broad prospects in lysosome-related research.