Real-time monitoring of hydrophobic aggregation reveals a critical role of cooperativity in hydrophobic effect.

The hydrophobic interaction drives nonpolar solutes to aggregate in aqueous solution, and hence plays a critical role in many fundamental processes in nature. An important property intrinsic to hydrophobic interaction is its cooperative nature, which is originated from the collective motions of water hydrogen bond networks surrounding hydrophobic solutes. This property is widely believed to enhance the formation of hydrophobic core in proteins.

Photocontrolled SiRNA Delivery and Biomarker-Triggered Luminogens of Aggregation-Induced Emission by Up-Conversion NaYF:YbTm@SiO Nanoparticles for Inducing and Monitoring Stem-Cell Differentiation.

Controlling the differentiation of stem cells and monitoring cell differentiation has attracted much research interest since the discovery of stem cells. In this regard, a novel near-infrared (NIR) light-activated nanoplatform is obtained by encapsulating the photoactivatable caged compound (DMNPE/siRNA) and combining a MMP13 cleaved imaging peptide-tetrapheny-lethene (TPE) unit conjugated with the mesoporous silica-coated up-conversion nanoparticles (UCNPs) for the remote control of cell differentiation and, simultaneously, for the real-time monitoring of differentiation. Upon NIR light illumination, the photoactivated caged compound is activated, and the siRNA is released from UCNPs, allowing controlled differentiation of stem cells by light.

An AIE-based bioprobe for differentiating the early and late stages of apoptosis mediated by HO.

A bioprobe, TPE-ZnBDPA, with aggregation-induced emission characteristics was designed and synthesized to differentiate the early and late stages of apoptosis mediated by HO. TPE-ZnBDPA does not respond to healthy cells, but it selectively lights up the membrane of apopotic cells in both stages with brighter fluorescence in the late apoptotic stage.

A photostable AIEgen for nucleolus and mitochondria imaging with organelle-specific emission.

Dynamic visualization of the morphology of membrane-bound organelles offers useful insights for studying various intracellular activities. Fluorescent probes with superior specificity and photostability are desirable for long-term tracking of these processes. In this work, we present the design and synthesis of an α-cyanostilbene derivative, abbreviated as ASCP, with the aggregation-induced emission (AIE) characteristic, and its application in cell imaging.

A near-infrared AIEgen for specific imaging of lipid droplets.

A new near-infrared AIE luminogen (TPE-AC) with high specificity, good biocompatibility and excellent photostability is designed and synthesized for lipid droplet (LD) imaging in cells. TPE-AC can monitor the process of LD accumulation in cells, thus making it potential for the diagnosis of early-stage fat-related diseases.

Using AIE Luminogen for Long-term and Low-background Three-Photon Microscopic Functional Bioimaging.

Fluorescent probes are one of the most popularly used bioimaging markers to monitor metabolic processes of living cells. However, long-term light excitation always leads to photobleaching of fluorescent probes, unavoidable autofluorescence as well as photodamage of cells. To overcome these limitations, we synthesized a type of photostable luminogen named TPE-TPP with an aggregation induced emission (AIE) characteristic, and achieved its three-photon imaging with femtosecond laser excitation of 1020 nm.

A Luminogen with Aggregation-Induced Emission Characteristics for Wash-Free Bacterial Imaging, High-Throughput Antibiotics Screening and Bacterial Susceptibility Evaluation.

A luminogen with aggregation-induced emission characteristics is reported for bacterial imaging and antibiotics screening studies. The luminogen can light up bacteria in a wash-free manner, which simplifies the imaging process and increases its accuracy in bacterial detection. It can also be applied to high-throughput screening of antibiotics and fast evaluation of bacterial susceptibility, giving reliable results in less than 5 h.

Long-term two-photon neuroimaging with a photostable AIE luminogen.

In neuroscience, fluorescence labeled two-photon microscopy is a promising tool to visualize ex vivo and in vivo tissue morphology, and track dynamic neural activities. Specific and highly photostable fluorescent probes are required in this technology. However, most fluorescent proteins and organic fluorophores suffer from photobleaching, so they are not suitable for long-term imaging and observation.

Light-enhanced bacterial killing and wash-free imaging based on AIE fluorogen.

The rapid acquisition of antibiotic resistance poses difficulties in the development of effective methods to eliminate pathogenic bacteria. New bactericides, especially those do not induce the emergence of resistance, are thus in great demand. In this work, we report an aggregation-induced emission fluorogen, TPE-Bac, for bacterial imaging and elimination.

Detection of oligomers and fibrils of α-synuclein by AIEgen with strong fluorescence.

We report a fluorophore, TPE-TPP, with AIE characteristics which is utilized as a fluorescence probe to monitor the α-synuclein (α-Syn) fibrillation process. Compared with ThT, TPE-TPP shows a higher sensitivity in the detection of α-Syn oligomers as well as fibrils with a stronger fluorescence. The performance of TPE-TPP was evaluated using fluorescence, AFM, dot blot, and SEC.

Biosensing by luminogens with aggregation-induced emission characteristics.

Fluorescent biosensors are powerful analytical tools for studying biological events in living systems. Luminescent materials with aggregation-induced emission (AIE) attributes have attracted much research interest and have been identified as a novel class of luminogens to develop fluorescent turn-on biosensors with superior sensitivity. In this Tutorial Review, we present an overview of the AIE phenomenon and its mechanism.

Specific imaging and tracking of mitochondria in live cells by a photostable AIE luminogen.

Tracking the dynamics of mitochondrial morphology has attracted much research interest because of its involvement in early stage apoptosis and degenerative conditions. To follow this process, highly specific and photostable fluorescent probes are in demand. Commercially available mitochondria trackers, however, suffer from poor photostability.

A dual functional AEE fluorogen as a mitochondrial-specific bioprobe and an effective photosensitizer for photodynamic therapy.

We report a dual functional aggregation-enhanced emission (AEE) molecule, TPE-IQ, which could target and illuminate mitochondria in both live and fixed cells with superb selectivity and high signal-to-noise ratio. More intriguingly, TPE-IQ can serve as a photosensitizer to generate reactive oxygen species (ROS) in the mitochondria region to induce cell apoptosis.

A fluorescent light-up probe with AIE characteristics for specific mitochondrial imaging to identify differentiating brown adipose cells.

We report the design and synthesis of a specific mitochondrial fluorescent probe AIE-MitoGreen-1 with AIE characteristics to monitor the mitochondrial morphology changes and identify the differentiation process of living brown adipose cells. The probe AIE-MitoGreen-1 has significant advantages such as high cellpermeability, good mitochondrial retention, low background fluorescence, large Stokes shift, and low toxicity.

A selective glutathione probe based on AIE fluorogen and its application in enzymatic activity assay.

In this work, we design and synthesize a malonitrile-functionalized TPE derivative (TPE-DCV), which can react with thiol group through thiol-ene click reaction, leading to the fluorescence change of the system. Combined with the unique AIE property, TPE-DCV can selectively detect glutathione (GSH) but not cysteine or homocysteine. As the cleavage of GSSG with the aid of glutathione reductase produces GSH, which turns on the fluorescence of TPE-DCV, the ensemble of TPE-DCV and GSSG can thus serve as a label-free sensor for enzymatic activity assay of glutathione reductase.

Superior fluorescent probe for detection of cardiolipin.

Cardiolipin (CL) is a unique phospholipid found in mitochondrial inner membrane. It is a key component for mitochondrial function in both respiration and apoptosis. The level of CL is an important parameter for investigating these intracellular events and is a critical indicator of a number of diseases associated with mitochondrial respiratory functions.

Conjugated polyelectrolytes with aggregation-enhanced emission characteristics: synthesis and their biological applications.

Conjugated polyelectrolytes are promising candidates for the construction of fluorescent bioprobes. In this study, a series of water-soluble fluorescent polyelectrolytes have been designed and synthesized by means of the quaternization of their tetraphenylethene-containing polyyne precursors. The polyynes can be facilely prepared through Hay-Glaser polycoupling in high yields (up to 99%) with high molecular weights (up to 38,900).

Highly fluorescent and photostable probe for long-term bacterial viability assay based on aggregation-induced emission.

Long-term tracking of bacterial viability is of great importance for monitoring the viability change of bacteria under storage, evaluating disinfection efficiency, as well as for studying the pharmacokinetic and pharmacodynamic properties of antibacterials. Most of the conventional viability dyes, however, suffer from high toxicity and/or poor photostability, making them unsuitable for long-term studies. In this work, an aggregation-induced emission molecule, TPE-2BA, which can differentiate dead and living bacteria and serve as a highly fluorescent and photostable probe for long-term viability assay.

Water-soluble tetraphenylethene derivatives as fluorescent "light-up" probes for nucleic acid detection and their applications in cell imaging.

The detection of nucleic acids, such as DNA and RNA, plays a significant role in genetic engineering, forensics, and bioinformatics. Traditional nucleic acid probes are mainly intercalators, which are potential mutagens, or groove binders that show high preference only for double-stranded DNA. We herein present two versatile fluorescent probes for nucleic acid detection and visualization.

Full-range intracellular pH sensing by an aggregation-induced emission-active two-channel ratiometric fluorogen.

Intracellular pH (pHi) is an important parameter associated with cellular behaviors and pathological conditions. Sensing pHi and monitoring its changes in live cells are essential but challenging due to the lack of effective probes. We herein report a pH-sensitive fluorogen for pHi sensing and tracking.

A photostable AIE luminogen for specific mitochondrial imaging and tracking.

Tracking the dynamics of mitochondrial morphology has attracted much research interest because of its involvement in early stage apoptosis and degenerative conditions. To follow this process, highly specific and photostable fluorescent probes are in demand. Commercially available mitochondria trackers, however, suffer from poor photostability.

Monitoring and inhibition of insulin fibrillation by a small organic fluorogen with aggregation-induced emission characteristics.

Amyloid fibrillation of proteins is associated with a great variety of pathologic conditions. Development of new molecules that can monitor amyloidosis kinetics and inhibit fibril formation is of great diagnostic and therapeutic value. In this work, we have developed a biocompatible molecule that functions as an ex situ monitor and an in situ inhibitor for protein fibrillation, using insulin as a model protein.

Fluorogenic Zn(II) and chromogenic Fe(II) sensors based on terpyridine-substituted tetraphenylethenes with aggregation-induced emission characteristics.

Terpyridine-containing tetraphenylethenes (TPEs) are synthesized and their optical and metal sensing properties are investigated. They are practically nonluminescent in the solution state but become highly emissive as nanoparticle suspensions in poor solvents or thin films in the solid state, demonstrating a novel phenomenon of aggregation-induced emission (AIE). The emission of the nanoaggregates of TPEs is pH-sensitive: it is decreased and eventually quenched upon protonation of their terpyridine units because of their AIE nature.