Guangxue Feng

Mitochondria‐Targeted Cancer Therapy Using a Light‐Up Probe with Aggregation‐Induced‐Emission Characteristics

Subcellular organelle-specific reagents for simultaneous tumor targeting, imaging, and treatment are of enormous interest in cancer therapy. Herein, we present a mitochondria-targeting probe (AIE-mito-TPP) by conjugating a triphenylphosphine (TPP) with a fluorogen which can undergo aggregation-induced emission (AIE). Owing to the more negative mitochondrial membrane potential of cancer cells than normal cells, the AIE-mito-TPP probe can selectively accumulate in cancer-cell mitochondria and light up its fluorescence. More importantly, the probe exhibits selective cytotoxicity for studied cancer cells over normal cells. The high potency of AIE-mito-TPP correlates with its strong ability to aggregate in mitochondria, which can efficiently decrease the mitochondria membrane potential and increase the level of intracellular reactive oxygen species (ROS) in cancer cells. The mitochondrial light-up probe provides a unique strategy for potential image-guided therapy of cancer cells.

Ultrabright Organic Dots with Aggregation‐Induced Emission Characteristics for Real‐Time Two‐Photon Intravital Vasculature Imaging

Ultrabright organic dots with aggregation-induced emission characteristics (AIE dots) are prepared and shown to exhibit a high quantum yield, a, large two-photon absorption cross-section, and low in vivo toxicity. Real-time two-photon intravital blood vascular imaging in various tissues substantiates that the AIE dots are effective probes for in vivo vasculature imaging in a deep and high-contrast manner.

A fluorescent light-up probe with “AIE + ESIPT” characteristics for specific detection of lysosomal esterase

We report a fluorescent light-up probe AIE-Lyso-1 for in situ visualization of lysosomal esterase activity. The probe is based on a salicyladazine fluorogen, which is conjugated with esterase reactive acetoxyl groups and lysosome-targeting morpholine moieties. The probe has characteristics of both aggregation-induced emission (AIE) and excited-state intramolecular proton transfer (ESIPT), which shows significant advantages, such as lysosome-specific targeting, no self-quenching at high concentration, excellent light-up ratio, large Stokes shift, low cytotoxicity, and high specificity to esterase. It has also been used for in situ monitoring of lysosomal esterase activity and tracking lysosomal movements in living cells, which has great potential for the diagnosis of Wolman disease caused by deficiency of lysosomal esterase.

Bright Far-Red/Near-Infrared Conjugated Polymer Nanoparticles for In Vivo Bioimaging

A highly emissive far-red/near-infrared (FR/NIR) fluorescent conjugated polymer (CP), poly[(9,9-dihexylfluorene)-co-2,1,3-benzothiadiazole-co-4,7-di(thiophen-2-yl)-2,1,3-benzothiadiazole] (PFBTDBT10) is designed and synthesized via Suzuki polymerization. Formulation of PFBTDBT10 using 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)-2000] (DSPE-PEG2000 ) and DSPE-PEG5000-folate as the encapsulation matrix yielded CP-loaded DSPE-PEG-folic acid nanoparticles (CPDP-FA NPs) with bright FR/NIR fluorescence (27% quantum yield) and a large Stokes shift of 233 nm in aqueous solution. CPDP-FA NPs show improved thermal/photostabilities and larger Stokes shifts as compared to commercially available quantum dots (Qdot 655) and organic dyes such as Alexa Fluor 555 and Rhodamine 6G. In vivo studies of CPDP-FA NPs on a hepatoma H22 tumor-bearing mouse model reveal that they could serve as an efficient FR/NIR fluorescent probe for targeted in vivo fluorescence imaging and cancer detection in a high contrast and specific manner. Together with the negligible in vivo toxicity, CPDP-FA NPs are promising FR/NIR fluorescent probes for future in vivo applications.

Ultrabright organic dots with aggregation-induced emission characteristics for cell tracking.

Noninvasive fluorescence cell tracking provides critical information on the physiological displacement and translocation of actively migrating cells, which deepens our understanding of biomedical engineering, oncological research, stem cell transplantation and therapies. Non-viral fluorescent protein transfection based cell tracing has been widely used but with issues related to cell type-dependent expression, lagged readout, immunogenicity and mutagenesis. Alternative cell tracking methods are therefore desired to attain reliable, stable, and efficient labeling over a long time. In this work, we have successfully developed ultra-bright organic dots with aggregation-induced emission (AIE dots) and demonstrated their capabilities for cellular imaging and cell tracking. The AIE dots possess high fluorescence, super photostability, and excellent cellular retention and biocompatibility. As compared to commonly used pMAX-GFP plasmid labeling approach, the organic AIE dots showed excellent cell labeling on all tested human cell lines and superior tracing performance, which opens up new opportunities in the cell-based immunotherapies and other related biological researches.

Fluorescence bioimaging with conjugated polyelectrolytes

This review summarizes the recent developments in fluorescent conjugated polyelectrolytes (CPEs) in bioimaging. The CPEs discussed include linear-, hyperbranched-, and polyhedral oligomeric silsesquioxanes (POSS)-based derivatives. Originating from their special optical properties, good photostability, low cytotoxicity, ease of bioconjugation and tuneable size, CPEs have shown wide applications in in vitro and in vivo protein and cell imaging, drug tracking and gene delivery. Moreover, some CPEs also possess antibacterial and anticancer characteristics as well as apoptosis imaging functions. Finally, this review discusses the future outlook of CPEs in bioimaging applications.

Biocompatible Green and Red Fluorescent Organic Dots with Remarkably Large Two-Photon Action Cross Sections for Targeted Cellular Imaging and Real-Time Intravital Blood Vascular Visualization.

Fluorescent organic dots are emerging as promising bioimaging reagents because of their high brightness, good photostability, excellent biocompatibility, and facile surface functionalization. Organic dots with large two-photon absorption (TPA) cross sections are highly desired for two-photon fluorescence microscopy. In this work, we report two biocompatible and photostable organic dots fabricated by encapsulating tetraphenylethene derivatives within DSPE-PEG matrix. The two organic dots show absorption maxima at 425 and 483 nm and emit green and red fluorescence at 560 and 645 nm, with high fluorescence quantum yields of 64% and 22%, respectively. Both organic dots exhibit excellent TPA property in the range of 800-960 nm, affording upon excitation at 820 nm remarkably large TPA cross sections of 1.2×10(6) and 2.5×10(6) GM on the basis of dot concentration. The bare fluorophores and their organic dots are biocompatible and have been used to stain living cells for one- and two-photon fluorescence bioimagings. The cRGD-modified organic dots can selectively target integrin αvβ3 overexpressing breast cancer cells for targeted imaging. The organic dots are also applied for real-time two-photon fluorescence in vivo visualization of the blood vasculature of mouse ear, providing the spatiotemporal information about the whole blood vascular network. These results demonstrate that the present fluorescent organic dots are promising candidates for living cell and tissue imaging.

Light-up Bioprobe with Aggregation-induced Emission Characteristics for Real-time Apoptosis Imaging in Target Cancer Cells

Specific bioprobes that are capable of real-time and targeted monitoring and imaging of cancer cell apoptosis are highly desirable for cancer diagnosis and the evaluation of cancer therapy efficacy. In this work, an asymmetric fluorescent light-up bioprobe with aggregation-induced emission (AIE) characteristics was designed and synthesized by the conjugation of two different hydrophilic peptides, caspase-specific Asp-Glu-Val-Asp (DEVD) and cyclic Arg-Gly-Asp (cRGD), onto a typical AIE luminogen of a tetraphenylsilole (TPS) unit. The asymmetric probe is almost non-emissive in aqueous solution and its fluorescence is significantly switched on in the presence of caspase-3. The fluorescence turn-on is due to the cleavage of the DEVD moiety by caspase-3, and the aggregation of released TPS-cRGD residues, which restricts the intramolecular rotations of TPS phenyl rings and populates the radiative decay channels. Application of the asymmetric light-up probe for real-time targeted imaging of cancer cell apoptosis is successfully demonstrated using integrin αvβ3 receptor overexpressing U87MG human glioblastoma cells as an example. The probe shows specific targeting capability to U87MG cancer cells by virtue of the efficient binding between cRGD and integrin αvβ3 receptors and is able to real-time monitor and image cancer cell apoptosis in a specific and sensitive manner.

A fluorescent light-up probe based on AIE and ESIPT processes for β-galactosidase activity detection and visualization in living cells

A novel fluorescent probe SA-βGal is reported here with light-up response to β-galactosidase. SA-βGal possesses the β-galactopyranoside group to react with β-galactosidase and releases the fluorescent salicylaldehyde azine with both aggregation induced emission (AIE) and excited-state intramolecular proton transfer (ESIPT) characteristics. The linear fluorescent response enables the in vitro quantification of β-galactosidase activity in a range of 0-0.1 U mL-1 with a detection limit of 0.014 U mL-1. The probe exhibits significant advantages, such as no self-quenching at high concentrations, a large Stokes shift (190 nm) and high specificity to β-galactosidase with an excellent light-up ratio of 820 fold. Moreover, thanks to its good retention in living cells, the application of SA-βGal for the imaging of cellular β-galactosidase was also achieved with high contrast.

Precise Two‐Photon Photodynamic Therapy using an Efficient Photosensitizer with Aggregation‐Induced Emission Characteristics

Two-photon photodynamic therapy (PDT) is able to offer precise 3D manipulation of treatment volumes, providing a target level that is unattainable with current therapeutic techniques. The advancement of this technique is greatly hampered by the availability of photosensitizers with large two-photon absorption (TPA) cross section, high reactive-oxygen-species (ROS) generation efficiency, and bright two-photon fluorescence. Here, an effective photosensitizer with aggregation-induced emission (AIE) characteristics is synthesized, characterized, and encapsulated into an amphiphilic block copolymer to form organic dots for two-photon PDT applications. The AIE dots possess large TPA cross section, high ROS generation efficiency, and excellent photostability and biocompatibility, which overcomes the limitations of many conventional two-photon photosensitizers. Outstanding therapeutic performance of the AIE dots in two-photon PDT is demonstrated using in vitro cancer cell ablation and in vivo brain-blood-vessel closure as examples. This shows therapy precision up to 5 µm under two-photon excitation.