Amperometric Identification of Single Exosomes and Their Dopamine Contents Secreted by Living Cells.

Dopamine (DA) is an important neurotransmitter, which not only participates in the regulation of neural processes but also plays critical roles in tumor progression and immunity. However, direct identification of DA-containing exosomes, as well as quantification of DA in single vesicles, is still challenging. Here, we report a nanopipette-assisted method to detect single exosomes and their dopamine contents via amperometric measurement. The resistive-pulse current measured can simultaneously provide accurate information of vesicle translocation and DA contents in single exosomes. Accordingly, DA-containing exosomes secreted from HeLa and PC12 cells under different treatment modes successfully detected the DA encapsulation efficiency and the amount of exosome secretion that distinguish between cell types. Furthermore, a custom machine learning model was constructed to classify the exosome signals from different sources, with an accuracy of more than 99%. Our strategy offers a useful tool for investigating single exosomes and their DA contents, which facilitates the analysis of DA-containing exosomes derived from other untreated or stimulated cells and may open up a new insight to the research of DA biology.

Fluorescent Probes Based on AIEgen-Mediated Polyelectrolyte Assemblies for Manipulating Intramolecular Motion and Magnetic Relaxivity.

Uniting photothermal therapy (PTT) with magnetic resonance imaging (MRI) holds great potential in nanotheranostics. However, the extensively utilized hydrophobicity-driven assembling strategy not only restricts the intramolecular motion-induced PTT, but also blocks the interactions between MR agents and water. Herein, we report an aggregation-induced emission luminogen (AIEgen)-mediated polyelectrolyte nanoassemblies (APN) strategy, which bestows a unique "soft" inner microenvironment with good water permeability. Femtosecond transient spectra verify that APN well activates intramolecular motion from the twisted intramolecular charge transfer process. This de novo APN strategy uniting synergistically three factors (rotational motion, local motion, and hydration number) brings out high MR relaxivity. For the first time, APN strategy has successfully modulated both intramolecular motion and magnetic relaxivity, achieving fluorescence lifetime imaging of tumor spheroids and spatio-temporal MRI-guided high-efficient PTT.

Engineering Nanoparticulate Organic Photocatalysts via a Scalable Flash Nanoprecipitation Process for Efficient Hydrogen Production.

Directly converting sunlight into hydrogen fuels using particulate photocatalysts represents a sustainable route for clean energy supply. Organic semiconductors have emerged as attractive candidates but always suffer from optical and exciton recombination losses with large exciton "dead zone" inside the bulk material, severely limiting the catalytic performance. Herein, we demonstrate a facile strategy that combines a scalable flash nanoprecipitation (FNP) method with hydrophilic soluble polymers (PC-PEG5 and PS-PEG5) to prepare highly efficient nanosized photocatalysts without using surfactants. Significantly, a 70-fold enhancement of hydrogen evolution rate (HER) is achieved for nanosized PC-PEG5, and the FNP-processed PS-PEG5 shows a peak HER rate of up to 37.2 mmol h-1 g-1 under full-spectrum sunlight irradiation, which is among the highest results for polymer photocatalysts. A scaling-up production of nanocatalyst is demonstrated with the continuously operational FNP.

Harnessing Hypoxia-Dependent Cyanine Photocages for In†Vivo Precision Drug Release.

Photocaging holds promise for the precise manipulation of biological events in space and time. However, current near-infrared (NIR) photocages are oxygen-dependent for their photolysis and lack of timely feedback regulation, which has proven to be the major bottleneck for targeted therapy. Herein, we present a hypoxia-dependent photo-activation mechanism of dialkylamine-substituted cyanine (Cy-NH) accompanied by emissive fragments generation, which was validated with retrosynthesis and spectral analysis. For the first time, we have realized the orthogonal manipulation of this hypoxia-dependent photocaging and dual-modal optical signals in living cells and tumor-bearing mice, making a breakthrough in the direct spatiotemporal control and in vivo feedback regulation. This unique photoactivation mechanism overcomes the limitation of hypoxia, which allows site-specific remote control for targeted therapy, and expands the photo-trigger toolbox for on-demand drug release, especially in a physiological context with dual-mode optical imaging under hypoxia.

Circularly Polarized Fluorescence Resonance Energy Transfer (C-FRET) for Efficient Chirality Transmission within an Intermolecular System.

The occurrence and transmission of chirality is a fascinating characteristic of nature. However, the intermolecular transmission efficiency of circularly polarized luminescence (CPL) remains challenging due to poor through-space energy transfer. We report a unique CPL transmission from inducing the achiral acceptor to emit CPL within a specific liquid crystal (LC)-based intermolecular system through a circularly polarized fluorescence resonance energy transfer (C-FRET), wherein the luminescent cholesteric LC is employed as the chirality donor, and rationally designed achiral long-wavelength aggregation-induced emission (AIE) fluorophore acts as the well-assembled acceptor. In contrast to photon-release-and-absorption, the chirality transmission channel of C-FRET is highly dependent upon the energy resonance in the highly intrinsic chiral assembly of cholesteric LC, as verified by deliberately separating the achiral acceptor from the chiral donor to keep it far beyond the resonance distance. This C-FRET mode provides a de novo strategy concept for high-level information processing for applications such as high-density data storage, combinatorial logic calculation, and multilevel data encryption and decryption.

Comparative Study of the Nutritional Properties of 67 Potato Cultivars (Solanum tuberosum L.) Grown in China Using the Nutrient-Rich Foods (NRF11.3) Index.

The overall nutritional properties of tubers from 67 potato cultivars were systematically evaluated in this study by adopting the Nutrient-Rich Foods (NRF11.3) Index Model. The macronutrients including dry matter, crude protein, total dietary fiber, and starch contents were found to be in the range of 14.8-30.5 g/100 g fresh weight, 5.71-12.0, 1.99-3.39, and 56.0-75.5 g/100 g dry weight, respectively. Additionally, the amounts of vitamin C, K and Fe were 22.6-86.6, 1457-3111, and 1.40-5.06 mg/100 g dry weight, respectively. The NRF11.3 index model has a score of 66.4-102 per 100 kcal for male and 70.8-107 per 100 kcal for female over 18 years old. This model was utilized to determine the macrocomponents and micronutrients of diverse potato cultivars and aid in comprehensive nutritional study on potato as a desirable raw material for staple food processing to human nutrition and daily intake.

High-Performance Quinoline-Malononitrile Core as a Building Block for the Diversity-Oriented Synthesis of AIEgens.

In vivo fluorescent monitoring of physiological processes with high-fidelity is essential in disease diagnosis and biological research, but faces extreme challenges due to aggregation-caused quenching (ACQ) and short-wavelength fluorescence. The development of high-performance and long-wavelength aggregation-induced emission (AIE) fluorophores is in high demand for precise optical bioimaging. The chromophore quinoline-malononitrile (QM) has recently emerged as a new class of AIE building block that possesses several notable features, such as red to near-infrared (NIR) emission, high brightness, marked photostability, and good biocompatibility. In this minireview, we summarize some recent advances of our established AIE building block of QM, focusing on the AIE mechanism, regulation of emission wavelength and morphology, the facile scale-up and fast preparation for AIE nanoparticles, as well as potential biomedical imaging applications.

Spatio-Temporally Reporting Dose-Dependent Chemotherapy via Uniting Dual-Modal MRI/NIR Imaging.

Unpredictable in vivo therapeutic feedback of hydroxyl radical (. OH) efficiency is the major bottleneck of chemodynamic therapy. Herein, we describe novel Fenton-based nanotheranostics NQ-Cy@Fe&GOD for spatio-temporally reporting intratumor . OH-mediated treatment, which innovatively unites dual-channel near-infrared (NIR) fluorescence and magnetic resonance imaging (MRI) signals. Specifically, MRI signal traces the dose distribution of Fenton-based iron oxide nanoparticles (IONPs) with high-spatial resolution, meanwhile timely fluorescence signal quantifies . OH-mediated therapeutic response with high spatio-temporal resolution. NQ-Cy@Fe&GOD can successfully monitor the intracellular release of IONPs and . OH-induced NQO1 enzyme in living cells and tumor-bearing mice, which makes a breakthrough in conquering the inherent unpredictable obstacles on spatio-temporally reporting chemodynamic therapy, so as to manipulate dose-dependent therapeutic process.

A Sequential Dual-Lock Strategy for Photoactivatable Chemiluminescent Probes Enabling Bright Duplex Optical Imaging.

Chemiluminescence (CL)-based technologies have revolutionized in vivo monitoring of biomolecules. However, significant technical hurdles have limited the achievement of trigger-controlled, bright, and enriched CL signal. Herein, a dual-lock strategy uses sequence-dependent triggers for bright optical imaging with real-time fluorescent signal and ultra-sensitive CL signal. These probes can obtain an analyte-triggered accumulation of stable pre-chemiluminophore with aggregation-induced emission (AIE), and then the pre-chemiluminophore exhibits a rapid photooxidation process (1,2-dioxetane generation) by TICT-based free-radical addition, thereby achieving an enrichment and bright CL signal. The dual-lock strategy expands the in vivo toolbox for highly accurate analysis and has for the first time allowed access to accurately sense and trace biomolecules with high-resolution, dual-mode of chemo-fluoro-luminescence, and three-dimensional (3D) imaging in living animals.

Rational Design of Near-Infrared Aggregation-Induced-Emission-Active Probes: In Situ Mapping of Amyloid-ß Plaques with Ultrasensitivity and High-Fidelity.

High-fidelity mapping of amyloid-ß (Aß) plaques is critical for the early detection of Alzheimer's disease. However, in vivo probing of Aß plaques by commercially available thioflavin derivatives (ThT or ThS) has proven to be extremely limited, as evident by the restriction of enrichment quenching effect, low signal-to-noise ( S/ N) ratio, and poor blood-brain barrier (BBB) penetrability. Herein, we demonstrate a rational design strategy of near-infrared (NIR) aggregation-induced emission (AIE)-active probes for Aß plaques, through introducing a lipophilic π-conjugated thiophene-bridge for extension to NIR wavelength range with enhancement of BBB penetrability, and tuning the substituted position of the sulfonate group for guaranteeing specific hydrophilicity to maintain the fluorescence- off state before binding to Aß deposition. Probe QM-FN-SO3 has settled well the AIE dilemma between the lipophilic requirement for longer emission and aggregation behavior from water to protein fibrillogenesis, thus making a breakthrough in high-fidelity feedback on in vivo detection of Aß plaques with remarkable binding affinity, and serving as an efficient alternative to the commercial probe ThT or ThS.

AND-Logic Based Fluorescent Probe for Selective Detection of Lysosomal Bisulfite in Living Cells.

Sulfur dioxide (SO2) plays significant roles in regulating cell apotosis and inflammation. However, there are complex interactions between small biomolecules in cells, and the identification of these coexisting biomarkers remains a challenge. Herein, we report an AND logic gate based fluorescent probe (NY-Lyso), operating by responding to pH differences between organelles in cell and selectively reacting with bisulfite (HSO3-). This approach allows the fluorescence of the probe to remain silent under neutral or alkaline conditions, notably, is activated by costimulation of lower pH and bisulfite. Furthermore, it was confirmed to be biocompatible and could be employed to monitor HSO3- in lysosomes of living cells. The proposed method demonstrated more practical and outstanding capabilities in targeted and real-time monitoring, providing an effective optical tool for biomarker sensing.

Fluorescence Imaging of Alzheimer's Disease with a Flat Ensemble Formed between a Quinoline-Malononitrile AIEgen and Thin-Layer Molybdenum Disulfide.

The sensitive imaging of amyloid-ß (Aß) peptides is important for the timely detection of neurodegenerative diseases, such as Alzheimer's disease (AD). Although clinically the diagnosis of AD relies on the use of radiolabeled imaging reagents, herein we report the simple construction of a "flat ensemble" formed between a quinoline-malononitrile AIEgen (EDS) and thin-layer molybdenum disulfide (2D MoS2 ) for the sensitive detection of Aß by means of fluorescence-based techniques. Self-assembly between EDS and 2D MoS2 in aqueous buffer solution produces the flat ensemble, and the subsequent interaction of the material ensemble with oligomeric and aggregated Aß peptides leads to up to 19-fold enhanced fluorescence of EDS. The ensemble is also applicable for staining Aß aggregates in vivo.

A fast-response and highly specific Si-Rhodamine probe for endogenous peroxynitrite detection in living cells.

Peroxynitrite (ONOO-) is involved in a variety of physiological and pathological processes. We designed and synthesized a fluorescent probe SiNH based on Si-rhodamine. The nanoprobe SiNH encapsulated within the amphiphilic copolymer exhibited fast response within 10 s, and it was highly specific for ONOO- in aqueous solution. It is demonstrated that the nanoprobe SiNH is applicable for real-time tracing of endogenous ONOO- in living cells.

Real-Time Tracking and In Vivo Visualization of ß-Galactosidase Activity in Colorectal Tumor with a Ratiometric Near-Infrared Fluorescent Probe.

Development of "smart" noninvasive bioimaging probes for trapping specific enzyme activities is highly desirable for cancer therapy in vivo. Given that ß-galactosidase (ß-gal) is an important biomarker for cell senescence and primary ovarian cancers, we design an enzyme-activatable ratiometric near-infrared (NIR) probe (DCM-ßgal) for the real-time fluorescent quantification and trapping of ß-gal activity in vivo and in situ. DCM-ßgal manifests significantly ratiometric and turn-on NIR fluorescent signals simultaneously in response to ß-gal concentration, which makes it favorable for monitoring dynamic ß-gal activity in vivo with self-calibration in fluorescent mode. We exemplify DCM-ßgal for the ratiometric tracking of endogenously overexpressed ß-gal distribution in living 293T cells via the lacZ gene transfection method and OVCAR-3 cells, and further realize real-time in vivo bioimaging of ß-gal activity in colorectal tumor-bearing nude mice. Advantages of our system include light-up ratiometric NIR fluorescence with large Stokes shift, high photostability, and pH independency under the physiological range, allowing for the in vivo real-time evaluation of ß-gal activity at the tumor site with high-resolution three-dimensional bioimaging for the first time. Our work provides a potential tool for in vivo real-time tracking enzyme activity in preclinical applications.

Enabling Light Work in Helical Self-Assembly for Dynamic Amplification of Chirality with Photoreversibility.

Light-driven transcription and replication are always subordinate to a delicate chirality transfer. Enabling light work in construction of the helical self-assembly with reversible chiral transformation becomes attractive. Herein we demonstrate that a helical hydrogen-bonded self-assembly is reversibly photoswitched between photochromic open and closed forms upon irradiation with alternative UV and visible light, in which molecular chirality is amplified with the formation of helixes at supramolecular level. The characteristics in these superhelixes such as left-handed or right-handed twist and helical length, height, and pitch are revealed by SEM and AFM. The helical photoswitchable nanostructure provides an easily accessible route to an unprecedented photoreversible modulation in morphology, fluorescence, and helicity, with precise assembly/disassembly architectures similar to biological systems such as protein and DNA.

Förster Resonance Energy Transfer Switchable Self-Assembled Micellar Nanoprobe: Ratiometric Fluorescent Trapping of Endogenous H2S Generation via Fluvastatin-Stimulated Upregulation.

H2S produced in small amounts by mammalian cells has been identified in mediating biological signaling functions. However, the in situ trapping of endogenous H2S generation is still handicapped by a lack of straightforward methods with high selectivity and fast response. Here, we encapsulate a semi-cyanine-BODIPY hybrid dye (BODInD-Cl) and its complementary energy donor (BODIPY1) into the hydrophobic interior of an amphiphilic copolymer (mPEG-DSPE), especially for building up a ratiometric fluorescent H2S nanoprobe with extraordinarily fast response. A remarkable red-shift in the absorption band with a gap of 200 nm in the H2S response can efficiently switch off the Förster resonance energy transfer (FRET) from BODIPY1 to BODInD-Cl, subsequently recovering the donor fluorescence. Impressively, both the interior hydrophobicity of supramolecular micelles and electron-withdrawing nature of indolium unit in BODInD-Cl can sharply increase aromatic nucleophilic substitution with H2S. The ratiometric strategy based on the unique self-assembled micellar aggregate NanoBODIPY achieves an extremely fast response, enabling in situ imaging of endogenous H2S production and mapping its physiological and pathological consequences. Moreover, the amphiphilic copolymer renders the micellar assembly biocompatible and soluble in aqueous solution. The established FRET-switchable macromolecular envelope around BODInD-Cl and BODIPY1 enables cellular uptake, and makes a breakthrough in the trapping of endogenous H2S generation within raw264.7 macrophages upon stimulation with fluvastatin. This study manifests that cystathione γ-lyase (CSE) upregulation contributes to endogenous H2S generation in fluvastatin-stimulated macrophages, along with a correlation between CSE/H2S and activating Akt signaling pathway.

Recent progress in the development of near-infrared fluorescent probes for bioimaging applications.

Near-infrared (NIR) fluorescent dyes have emerged as promising modalities for monitoring the levels of various biologically relevant species in cells and organisms. The use of NIR probes enables deep photon penetration in tissue, minimizes photo-damage to biological samples, and produces low background auto-fluorescence from biomolecules present in living systems. The number of new analyte-responsive NIR fluorescent probes has increased substantially in recent years as a consequence of intense research efforts. In this tutorial review, we highlight recent advances (2010-2013) made in the development and applications of NIR fluorescent probes. The review focuses on NIR fluorescent probes that have been devised to sense various biologically important species, including ROS/RNS, metal ions, anions, enzymes and other related species, as well as intracellular pH changes. The basic principles involved in the design of functional NIR fluorescent probes and suggestions about how to expand applications of NIR imaging agents are also described.

Far-Red and Near-IR AIE-Active Fluorescent Organic Nanoprobes with Enhanced Tumor-Targeting Efficacy: Shape-Specific Effects.

The rational design of high-performance fluorescent materials for cancer targeting in vivo is still challenging. A unique molecular design strategy is presented that involves tailoring aggregation-induced emission (AIE)-active organic molecules to realize preferable far-red and NIR fluorescence, well-controlled morphology (from rod-like to spherical), and also tumor-targeted bioimaging. The shape-tailored organic quinoline-malononitrile (QM) nanoprobes are biocompatible and highly desirable for cell-tracking applications. Impressively, the spherical shape of QM-5 nanoaggregates exhibits excellent tumor-targeted bioimaging performance after intravenously injection into mice, but not the rod-like aggregates of QM-2.

In vivo and in situ tracking cancer chemotherapy by highly photostable NIR fluorescent theranostic prodrug.

In vivo monitoring of the biodistribution and activation of prodrugs is urgently required. Near infrared (NIR) fluorescence-active fluorophores with excellent photostability are preferable for tracking drug release in vivo. Herein, we describe a NIR prodrug DCM-S-CPT and its polyethylene glycol-polylactic acid (PEG-PLA) loaded nanoparticles as a potent cancer therapy. We have conjugated a dicyanomethylene-4H-pyran derivative as the NIR fluorophore with camptothecin (CPT) as the anticancer drug using a disulfide linker. In vitro experiments verify that the high intracellular glutathione (GSH) concentrations in tumor cells cause cleavage of the disulfide linker, resulting in concomitantly the active drug CPT release and significant NIR fluorescence turn-on with large Stokes shift (200 nm). The NIR fluorescence of DCM-S-CPT at 665 nm with fast response to GSH can act as a direct off-on signal reporter for the GSH-activatable prodrug. Particularly, DCM-S-CPT possesses much better photostability than ICG, which is highly desirable for in situ fluorescence-tracking of cancer chemotherapy. DCM-S-CPT has been successfully utilized for in vivo and in situ tracking of drug release and cancer therapeutic efficacy in living animals by NIR fluorescence. DCM-S-CPT exhibits excellent tumor-activatable performance when intravenously injected into tumor-bearing nude mice, as well as specific cancer therapy with few side effects. DCM-S-CPT loaded in PEG-PLA nanoparticles shows even higher antitumor activity than free CPT, and is also retained longer in the plasma. The tumor-targeting ability and the specific drug release in tumors make DCM-S-CPT as a promising prodrug, providing significant advances toward deeper understanding and exploration of theranostic drug-delivery systems.

Development of a small molecule probe capable of discriminating cysteine, homocysteine, and glutathione with three distinct turn-on fluorescent outputs.

The simultaneous discrimination of Cys, Hcy, and GSH by a single probe is still an unmet challenge. The design and synthesis of a small molecule probe MeO-BODIPY-Cl (BODIPY=boron dipyrromethene) is presented, which can allow Cys, Hcy, and GSH to be simultaneously discriminated on the basis of three distinct fluorescence turn-on responses. The probe reacts with these thiols to form sulfenyl-substituted BODIPY, which is followed by intramolecular displacement to yield amino-substituted BODIPY. The kinetic rate of the intramolecular displacement reaction determines the observed different sensing behavior. Therefore, the probe responds to Cys, Hcy, and GSH with fluorescence turn-on colors of yellow, yellow and red, and red, respectively. With this promising feature in hand, the probe was successfully used in imaging of Cys, Hcy and GSH in living cells.