Xuezhen Song

Simultaneous Near-Infrared and Two-Photon In Vivo Imaging of H2O2 Using a Ratiometric Fluorescent Probe based on the Unique Oxidative Rearrangement of Oxonium

A new ratiometric fluorescent H2 O2 probe, benzopyrylium-coumarin (BC), is designed by using an oxonium moiety as the unique H2 O2 response site. The BC probe exhibits an extremely large emission shift of 221 nm in response to H2 O2 , and is successfully applied for the simultaneous near-infrared and two-photon imaging of H2 O2 in living cells, mouse-liver tissues, and zebrafish.

A tumor-targeting and lysosome-specific two-photon fluorescent probe for imaging pH changes in living cells

Lysosomal pH is closely related to the metastasis and apoptosis of cancer cells. Detecting lysosomal pH changes in cancer cells could be helpful for analyzing tumor progressions and in-depth study of the roles of lysosomes in tumor invasion and metastasis. Herein, we describe a novel tumor-targeting and lysosome-specific two-photon fluorescent probe (BN-lys) for imaging pH changes for the first time. Biotin was employed as the tumor-targeting module, and morpholine was selected as the lysosome-specific group and the pH site to control the fluorescence by photoinduced electron transfer (PET) mechanism. With a pKa value of 5.36, BN-lys showed a fast and reversible fluorescence response to pH. Under the guidance of the biotin group, BN-lys displayed strong one-photon and two-photon fluorescence responses to lysosomal pH in cancer cells, while it displayed weak fluorescence in normal cells. Furthermore, BN-lys could be applied for the imaging of chloroquine-stimulated lysosomal pH changes in living cells. These features demonstrate that this probe could have practical applications in biological research.

Two-photon red-emissive fluorescent probe for imaging nitroxyl (HNO) in living cells and tissues

Nitroxyl (HNO) plays important roles in the regulation of many physiological and pathological processes, and can serve as a potential therapeutic agent for cardiovascular disease. The development of HNO detection in living systems is greatly important for in-depth studies of its biosynthesis and activities. Herein, we describe a novel two-photon red-emissive fluorescence probe (RP) for imaging HNO in living cells and tissues. RP was based on a red-emissive dye, Rho, and showed no fluorescence. When responding to HNO, RP can emit red fluorescence with the emission wavelength at 638 nm. RP exhibited a sensitive and selective response to HNO. Theoretical calculations demonstrated that the overlaps between the HOMO and LUMO were large for Rho and tiny for RP, consistent with the absorption and fluorescence properties of Rho and RP. Assisted by three-dimensional (3D) imaging, the two-photon imaging of HNO with red emission color in living tissues was successfully performed.

Construction of a ratiometric fluorescent probe with an extremely large emission shift for imaging hypochlorite in living cells

Hypochlorite is one of the important reactive oxygen species (ROS) and plays critical roles in many biologically vital processes. Herein, we present a unique ratiometric fluorescent probe (CBP) with an extremely large emission shift for detecting hypochlorite in living cells. Utilizing positively charged α,β-unsaturated carbonyl group as the reaction site, the probe CBP itself exhibited near-infrared (NIR) fluorescence at 662nm, and can display strong blue fluorescence at 456nm when responded to hypochlorite. Notably, the extremely large emission shift of 206nm could enable the precise measurement of the fluorescence peak intensities and ratios. CBP showed high sensitivity, excellent selectivity, desirable performance at physiological pH, and low cytotoxicity. The bioimaging experiments demonstrate the biological application of CBP for the ratiometric imaging of hypochlorite in living cells.

A sensitive and selective red fluorescent probe for imaging of cysteine in living cells and animals

Cysteine (Cys) is one of the important semi-essential amino acids, which often participates in many enzymatic reactions and has lots of biological functions. Herein, we present a sensitive and selective red fluorescent probe (RCys) for detecting Cys in living cells and animals. RCys utilized a rhodamine derivative as the fluorescent platform, and employed acrylate as the response site for Cys. When RCys responded to Cys, a significant turn-on red fluorescence at 638 nm was observed. RCys displayed obvious fluorescence response to Cys in a short time, and exhibited favorable selectivity to Cys over other thiols including GSH and Hcy. The biological applications demonstrated that RCys can be applied for the imaging of Cys in living cells and animals.

Dual turn-on fluorescence signal-based controlled release system for real-time monitoring of drug release dynamics in living cells and tumor tissues

Controlled release systems with capabilities for direct and real-time monitoring of the release and dynamics of drugs in living systems are of great value for cancer chemotherapy. Herein, we describe a novel dual turn-on fluorescence signal-based controlled release system (CDox), in which the chemotherapy drug doxorubicin (Dox) and the fluorescent dye (CH) are conjugated by a hydrazone moiety, a pH-responsive cleavable linker. CDox itself shows nearly no fluorescence as the fluorescence of CH and Dox is essentially quenched by the C=N isomerization and N-N free rotation. However, when activated under acidic conditions, CDox could be hydrolyzed to afford Dox and CH, resulting in dual turn-on signals with emission peaks at 595 nm and 488 nm, respectively. Notably, CDox exhibits a desirable controlled release feature as the hydrolysis rate is limited by the steric hindrance effect from both the Dox and CH moieties. Cytotoxicity assays indicate that CDox shows much lower cytotoxicity relative to Dox, and displays higher cell inhibition rate to cancer than normal cells. With the aid of the dual turn-on fluorescence at different wavelengths, the drug release dynamics of CDox in living HepG2 and 4T-1 cells was monitored in double channels in a real-time fashion. Importantly, two-photon fluorescence imaging of CDox in living tumor tissues was also successfully performed by high-definition 3D imaging. We expect that the unique controlled release system illustrated herein could provide a powerful means to investigate modes of action of drugs, which is critical for development of much more robust and effective chemotherapy drugs.

A unique red-emitting two-photon fluorescent probe with tumor-specificity for imaging in living cells and tissues

Tumor-specific imaging can provide an attractive approach for the early detection and prognosis of cancer, as well as the precise image-guided tumor-removal surgery. Herein, we describe a unique red-emitting two-photon fluorescent probe (N-BN) for tumor-specific imaging. N-BN utilized Nile Red as the red-emitting two-photon fluorophore and employed biotin as the tumor-specific ligand. In the presence of a variety of biomolecules or in different pH buffers, the fluorescence intensity of N-BN at 655nm showed no noticeable change. N-BN exhibited the remarkable two-photon absorption cross sections of 15.4g under excitation at 800nm. Under the guidance of biotin, N-BN can be applied for the imaging of biotin-receptor positive cancer cells over biotin-negative cells under red-emitting one- and two-photon manners. Assisted by high-definition three-dimensional imaging, the living tumor tissues loaded with N-BN could display strong red two-photon fluorescence with a penetration depth of about 90µm. Moreover, the in vivo and ex vivo imaging studies intuitively revealed that N-BN could track the tumor with highly tumor-specific property by a near-infrared manner.

A cancer cell-specific fluorescent probe for imaging Cu2 + in living cancer cells

Monitoring copper level in cancer cells is important for the further understanding of its roles in the cell proliferation, and also could afford novel copper-based strategy for the cancer therapy. Herein, we have developed a novel cancer cell-specific fluorescent probe for the detecting Cu2+ in living cancer cells. The probe employed biotin as the cancer cell-specific group. Before the treatment of Cu2+, the probe showed nearly no fluorescence. However, the probe can display strong fluorescence at 581nm in response to Cu2+. The probe exhibited excellent sensitivity and high selectivity for Cu2+ over the other relative species. Under the guidance of biotin group, could be successfully used for detecting Cu2+ in living cancer cells. We expect that this design strategy could be further applied for detection of the other important biomolecules in living cancer cells.