Dual-Functional AIE Fluorescent Probe for Visualization of Lipid Droplets and Photodynamic Therapy of Cancer.

Abnormal lipid droplets (LDs) are known to be intimately bound with the occurrence and development of cancer, allowing LDs to be critical biomarkers for cancers. Aggregation-induced emission luminogens (AIEgens), with efficient reactive oxygen species (ROS) production performance, are prime photosensitizers (PSs) for photodynamic therapy (PDT) with imaging. Therefore, the development of dual-functional fluorescent probes with aggregation-induced emission (AIE) characteristics that enable both simultaneous LD monitoring and imaging-guided PDT is essential for concurrent cancer diagnosis and treatment. Herein, we reported the development of a novel LD-targeting fluorescent probe (TDTI) with AIE performance, which was expected to realize the integration of cancer diagnosis through LD visualization and cancer treatment via PDT. We demonstrated that TDTI, with typical AIE characteristics and excellent photostability, could target LDs with high specificity, which enables the dynamic tracking of LDs in living cells, specific imaging of LDs in zebrafish, and the differentiation of cancer cells from normal cells for cancer diagnosis. Meanwhile, TDTI exhibited fast ROS generation ability (achieving equilibrium within 60 s) under white light irradiation (10 mW/cm2). The cell apoptosis assay revealed that TDTI effectively induced growth inhibition and apoptosis of HeLa cells. Further, the results of PDT in vivo indicated that TDTI had a good antitumor effect on the tumor-bearing mice model. Collectively, these results highlight the potential utility of the dual-functional fluorescent probe TDTI in the integrated diagnosis and treatment of cancer.

Synthesis of a Red-Emitting Polarity-Sensitive Fluorescent Probe Based on ICT and Visualization for Lipid Droplet Dynamic Processes.

Abnormal lipid droplets (LDs) have been recognized as critical factors in many diseases because they are metabolically active and dynamic organelles. Visualization for LD dynamic processes is fundamental for elucidating the relationship of LDs and related diseases. Herein, a red-emitting polarity-sensitive fluorescent probe (TPA-CYP) based on intramolecular charge transfer (ICT) was proposed, which was constructed by employing triphenylamine (TPA) and 2-(5,5-dimethyl-2-cyclohex-1-ylidene)propanedinitrile (CYP) as electron donor and acceptor moiety, respectively. The spectra results underlined the excellent characteristics of TPA-CYP, such as high polarity sensitivity (Δf = 0.209 to 0.312), strong solvatochromic effect (λem 595-699 nm), and the large Stokes shifts (174 nm). Moreover, TPA-CYP exhibited a specific ability to target LDs and effectively differentiated cancer cells and normal cells. Surprisingly, TPA-CYP had been successfully applied to dynamic tracking of LDs, not only in inflammation induced by lipopolysaccharide (LPS), the process of oxidative stress, but also in live zebrafish. We believe that TPA-CYP could serve as a powerful tool to gain insight into the dynamics of LDs and to understand and diagnose LD-associated diseases.

TICT-Based Microenvironment-Sensitive Probe with Turn-on Red Emission for Human Serum Albumin Detection and for Targeting Lipid Droplet Imaging.

Fluorescent probes sensitive to microenvironment have always been fascinating due to their tremendous advantages in tracking changes in the pathophysiological microenvironment and potential application in the early diagnosis of related diseases. In this study, a fluorescent luminogen, triphenylamine-thiophene-rhodanine (TPA-TRDN), with high sensitivity to changes in polarity and viscosity was designed and could be applied to detecting human serum albumin (HSA) in actual urine, as well as lipid droplets (LDs) in cells and in vivo with turn-on red emission. TPA-TRDN could selectively detect HSA with fast response (10 min), superior sensitivity (LOD 0.34 µg/mL, about 60-fold fluorescence enhancement), and wide detection range (0.00-0.30 mg/mL). The detection mechanism was demonstrated: TPA-TRDN encountered the hydrophobic IB domain of HSA, leading to the inhibition of the twisted intramolecular charge transfer (TICT) phenomenon and intramolecular rotation. Moreover, TPA-TRDN demonstrated satisfactory ability to identify cancer cells and noncancer cells by microenvironment-guided specific LD bioimaging. This evidence indicated that TPA-TRDN has promising application in the microenvironment-related biomedical field and clinical diagnosis.

Synthesis of a new environment-sensitive fluorescent probe based on TICT and application for detection of human serum albumin and specific lipid droplets imaging.

Environment-sensitive fluorescent probes have always been as forceful tools to understand the pathophysiological processes of relevant diseases. In this work, a new fluorescent probe with typical D-π-A structure was designed and showed high sensitivity to polarity and viscosity changes. DPAR could selectively detect human serum albumin (HSA) with turn-on orange emission in aqueous PBS buffer (pH 7.4), which showed advantages such as rapid response (4 min), high sensitivity (LOD 0.98 µg/mL). Therefore, it was successfully used for achieving HSA levels in urine samples and HSA imaging in HeLa cells. DPAR also exhibited the capability to recognize the cancer cells over the normal cells by lower polarity guided lipid droplets (LDs) imaging (in green emission channel). The detection mechanism for HSA and cancer diagnosis was convinced that DPAR encountered the lower-polarity and higher-viscosity microenvironment, resulting in the confinement of the TICT process and intramolecular rotation. These facts showed that DPAR had good application prospects in environment-related biomedical research and clinical diagnosis.

Development of a piperazinyl-NBD-based fluorescent probe and its dual-channel detection for hydrogen sulfide.

To selectively detect H2S based on the thiolysis reaction of 7-nitro-1,2,3-benzoxadiazole (NBD), amines attracted increasing attention since NBD amine is regarded as a new H2S reaction site. Herein, a novel fluorescent probe, triphenylamine piperazine NBD (TPA-Pz-NBD), was developed. The results showed that it exhibited high selectivity towards H2S via fluorescence spectroscopy and solution color. Furthermore, TPA-Pz-NBD not only detected H2S by a dual-channel, turn-on fluorescence signal at 500 nm and turn-off fluorescence signal at 545 nm, respectively, but also displayed a wide detection range of 0-125 µM. In addition, living cell imaging results indicated that TPA-Pz-NBD holds potential for the detection of intracellular H2S.

A red emitting fluorescent probe based on TICT for selective detection and imaging of HSA.

A red emitting fluorescence probe, TPA-CPO, based on twisted intra-molecular charge transfer (TICT) was designed and synthesized. The spectra results displayed that TPA-CPO could sense HSA with excellent properties including significant fluorescence enhancement, long emission wavelength, large stokes shift, and wide linear range. The recognition mechanism was proved that TPA-CPO could bind to domain IB of HSA and its TICT process was suppressed by utilizing hydrophobic cavity and low polarity of HSA. TPA-CPO bind to domain IB instead of common drug sites of HSA could effectively avoid interference from most drugs. The selective response of TPA-CPO allowed quantitative detection of HSA with sensitivity limit of 13.65 µg/mL. What's more, it successfully achieved HSA imaging in HeLa cells.

A turn-on fluorescence probe for hydrogen sulfide in absolute aqueous solution.

A turn-on hydrogen sulfide (H2S) fluorescence probe, 4-{2-[4-(2,4-dinitrophenoxy)-phenyl]-vinyl}-1-methyl-pyridinium iodide (DPPVP), based on the thiolysis reaction of dinitrophenyl ethers (DNP) has been proposed. Pyridinium structure enhanced the water solubility of DPPVP, which could quickly respond to H2S in absolute PBS solution and the fluorescence spectra of DPPVP at 520 nm were turned on by H2S. The spectra results exhibited that DPPVP could sensitively detect H2S with satisfied linear range (0-40 µM) and detection limit (13.4 nM). The high selectivity for H2S against biothiols was attributed to the significant difference in the pKa and the molecular size. Moreover, DPPVP has been successfully used for detecting H2S in vegetable.