Aggregation-induced Emission Fluorescent Probe Research Articles

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.

Unfolded Protein-Based Sandwich AIE Probe Imparts High Fluorescent Contrast for Pan-Cancer Surgical Navigation.

Fluorescence imaging-guided navigation for cancer surgery has a promising clinical application. However, pan-cancer encompasses a wide variety of cancer types with significant heterogeneity, resulting in the lack of universal and highly contrasted fluorescent probes for surgical navigation. Here, we developed an aggregation-induced emission (AIE) probe (MI-AIE-TsG, MAT) with dual activation for pan-cancer surgical navigation. MAT weakly activates fluorescence by targeting the SUR1 protein on the endoplasmic reticulum (ER) through the TsG group. Subsequently, the sulfhydryl groups on the unfolded proteins, which are highly enriched in cancer ER, react with the maleimide (MI) of MAT through the thiol-ene click reaction, further enhancing the fluorescence. The formation of a SUR1-MAT-unfolded protein sandwich complex reinforces the restriction of intramolecular motion and eliminates photoinduced electron transfer of MAT, leading to high signal-to-noise (9.2) fluorescence imaging and use for surgical navigation of pan-cancer. The generally high content of unfolded proteins in cancer cells makes MAT imaging generalizable, and it currently has proven feasibility in ovarian, cervical, and breast cancers. Meanwhile, MAT promotes cellular autophagy by hindering protein folding, thereby inhibiting cancer cell proliferation. This generalizable, high-contrast AIE fluorescent probe spans the heterogeneity of pancreatic cancer, enabling precise pancreatic cancer surgery navigation and treatment.

A near-infrared aggregation-induced emission photosensitizer targeting mitochondria for depleting Cu2+ to trigger light-activated cancer cells oncosis

Abnormally high levels of copper in tumors stimulate malignant proliferation and migration of cancer cells, which proposes a formidable challenge for the thorough therapy of malignant tumors. In this work, we developed a reliable, mitochondria-targeted near-infrared aggregation-induced emission fluorescent probe, TTQ-Th, whose thiourea moiety specifically could recognize mitochondria even both upon loss of mitochondrial membrane potential or in fixated cells, and can capture copper overexpressed by tumor cells, leading to severe copper deficiency. In parallel, TTQ-Th can generate sufficient reactive oxygen species (ROS) upon photoexcitation, while copper deficiency inhibits expression of related copper-based enzymes, resulting in a decline in ATP production. Such energy deficiency, combined with reduced MMP and elevated oxidative stress can lead to critical cell oncosis. Both in vitro and intracellular experiments can illustrate that the elevated ROS has remarkable damage to tumor cells and contributes to the elimination of the primary tumor, while copper deficiency further hinder tumor cell migration and induces G0/G1 cell cycle arrest in a dose-dependent manner, which is an efficacious strategy for the treatment of malignant tumors.

A turn-on AIE fluorescent probe with large Stokes shift for peroxynitrite detection and imaging in living cells

Peroxynitrite (ONOO−), as an important reactive oxygen species (ROS), plays a significant role in pathological and physiological processes, and abnormal levels of ONOO− will lead to many diseases. Thus, novel fluorescent probe for detecting ONOO− is in urgent need. Herein, we constructed a probe TPPB with aggregation-induced emission (AIE) characteristic based on triphenylamine and boronate group. The probe TPPB possesses remarkable performances including high selectivity in the presence of other ROSs, low detection limit (32 nM) and large Stokes shift (215 nm) toward ONOO−. Besides, probe TPPB shows low cytotoxicity and good imaging ability of ONOO− in living cells.

An aggregation-induced emission fluorescent probe for highly sensitive and selective detection and imaging of Hg2+ in living cells

Mercury ions (Hg2+), as one of heavy transition metals (HTM), is a highly toxic metal that is hazardous to human health. Here an aggregation-induced emission (AIE) fluorescent probe is designed for the highly sensitive and selective detection of Hg2+. The probe is engineered with a tetraphenylethene (TPE) derivative as the fluorophore and thiopropionic acid as the site of recognition for Hg2+. Due to the different solubilities of the probe AIE-COOH and its corresponding product after reaction with Hg2+. The probe demonstrates a maximum detection limit of 22 nM and a fast response time of ∼100 s. Simultaneously, AIE-COOH exhibits outstanding detectivity and hypersensitivity for the detection of Hg2+ in aqueous solutions. These characteristics demonstrate that AIE-COOH hold a great potential in environmental, food and biological systems. Moreover, we have also successfully applied it to Hg2+ fluorescence imaging in in living cells.

A Novel Aggregation-Induced Emission Fluorescent Probe for Detection of β-Amyloid Based on Pyridinyltriphenylamine and Quinoline-Malononitrile.

β-amyloid is an important pathological feature of Alzheimer's disease. Its abnormal production and aggregation in the patient's brain is an important basis for the early diagnosis and confirmation of Alzheimer's disease. In this study, a novel aggregation-induced emission fluorescent probe, PTPA-QM, was designed and synthesized based on pyridinyltriphenylamine and quinoline-malononitrile. These molecules exhibit a donor-donor-π-acceptor structure with a distorted intramolecular charge transfer feature. PTPA-QM displayed the advantages of good selectivity toward viscosity. The fluorescence intensity of PTPA-QM in 99% glycerol solution was 22-fold higher than that in pure DMSO. PTPA-QM has been confirmed to have excellent membrane permeability and low toxicity. More importantly, PTPA-QM exhibits a high affinity towards β-amyloid in brain sections of 5XFAD mice and classical inflammatory cognitive impairment mice. In conclusion, our work provides a promising tool for the detection of β-amyloid.

Tb3+-Based Off-On Fluorescent Platform for Multicolor and Dosage-Sensitive Visualization of Bacterial Spore Marker.

Developing a novel strategy for the sensitive and rapid detection of pathogenic bacterial spores in field or on-site settings will be helpful in minimizing their potential threats to human health, environmental safety, and food safety. In this study, Tb3+ was combined with glutathione (GSH)-modified copper nanoclusters (CuNCs), and an aggregation-induced emission (AIE) fluorescent probe based on Tb-GSH-CuNCs was fabricated for dipicolinic acid (DPA, a pathogenic bacterial spore marker) sensing. Making use of the competitive binding of Tb3+ between GSH-CuNCs and DPA, a multicolor sensing of DPA was facilely realized without introducing fluorescent materials as the reference. Due to an "off-on" response mechanism of the AIE fluorescent probe, this multicolor response to DPA exhibited a feature of rich color gradients and highly discriminative color change, allowing a dosage-sensitive visual quantification of DPA. The DPA with a concentration even as low as 0.5 μM can still be identified by the naked eye. Moreover, together with a smartphone app, which can extract the R (red), G (green), and B (blue) values from the probe system, a portable platform can be established for sensitive DPA quantification in the range of 0.5-70 μM, showing great potential for the practical monitoring of DPA in field or on-site settings.

Novel fluorescent probe for sequential recognition of Zn2+ and pyrophosphate in aqueous based on aggregation-induced emission

A new fluorescent probe (E)-4-(4-([2,2′:6′,2′'-terpyridin]-4′-yl)styryl)-1-dodecylpyridin-1-ium (TPy-SD), with the aggregation-induced emission (AIE) property in aqueous solution, has been synthesized and characterized. The new probe, TPy-SD exhibited excellent selectivity and sensitivity towards Zn2+ with a relatively low detection limit (1.76 × 10−7 M). The addition of Zn2+ is thought to disrupt the AIE property of TPy-SD, thereby leading to a fluorescence blue shift. Interestingly, the complex of probe TPy-SD with Zn2+ (Zn (II) TPy-SD), with molar ratio of 1:1, can be used as a simple, sensitive, and rapid means for the detection of pyrophosphates (PPi) in solution (water/DMSO = 99:1). As evidenced by transmission electron microscopy (TEM), dynamic light scattering (DLS) and fluorescence emission spectroscopy, this detection is thought to be due to the strong affinity between PPi and Zn2+, which brings out Zn2+ from the coordination cavity of chemical sensor TPy-SD, thus realizing the detection and recognition of PPi. Therefore, the new AIE fluorescent probe can be used as a dual probe for the detection of cations and anions.

De novo design of a novel AIE fluorescent probe tailored to autophagy visualization via pH manipulation

BackgroundMacroautophagy is an essential cellular self-protection mechanism, and defective autophagy has been considered to contribute to a variety of diseases. During the process, cytoplasmic components are transported via autophagosomes to acidic lysosomes for metabolism and recycling, which represents application niches for lysosome-targeted fluorescent probes. Additionally, in view of the complexity of the autophagy pathway, it entails more stringent requirements for probes suitable for monitoring autophagy. Meanwhile, aggregation-induced emission (AIE) fluorescent probes have been impressively demonstrated in the biomedical field, which bring fascinating possibilities to the autophagy visualization.MethodsWe reported a generalizable de novo design of a novel pH-sensitive AIE probe ASMP-AP tailored to lysosome targeting for the interpretation of autophagy. Firstly, the theoretical calculation was carried out followed by the investigation of optical properties. Then, the performance of ASMP-AP in visualizing autophagy was corroborated by starvation or drugs treatments. Furthermore, the capability of ASMP-AP to monitor autophagy was demonstrated in ex vivo liver tissue and zebrafish in vivo.ResultsASMP-AP displays a large stokes shift, great cell permeability and good biocompatibility. More importantly, ASMP-AP enables a good linear response to pH, which derives from the fact that its aggregation state can be manipulated by the acidity. It was successfully applied for imaging autophagy in living cells and was proved capable of monitoring mitophagy. Moreover, this novel molecular tool was validated by ex vivo visualization of activated autophagy in drug-induced liver injury model. Interestingly, it provided a meaningful pharmacological insight that the melanin inhibitor 1-phenyl-2-thiourea (PTU)-induced autophagy was clearly presented in wild-type zebrafish.ConclusionsASMP-AP offers a simple yet effective tool for studying lysosome and autophagy. This is the first instance to visualize autophagy in zebrafish using a small-molecule probe with AIE characters, accurate lysosome targeting and simultaneous pH sensitivity. Ultimately, this novel fluorescent system has great potential for in vivo translation to fuel autophagy research.Graphical

Multimode evaluating the fluctuation of lipid droplets polarity in acute kidney injury and tumor models

Lipid droplets (LDs) polarity changes are closely associated with the occurrence and development of various diseases. Simultaneously observing the LDs polarity fluctuations through fluorescence intensity, fluorescence wavelength, and fluorescence lifetime could greatly improve the accuracy of different pathological processes. We herein present a novel multimode two-photon aggregation-induced emission fluorescent probe (TP-LDs) for sensitively detecting the polarity changes in LDs. TP-LDs showed good photostability and high selectivity for LDs even at low concentrations. Furthermore, TP-LDs could detect the LDs polarity changes in the acute kidney injury (AKI) cell model and distinguish lung cancer cells and normal cells through fluorescence intensity, fluorescence lifetime, and fluorescence wavelength. Moreover, for the first time, we revealed LDs polarity changes in the AKI mouse model and its treatment. Most importantly, TP-LDs can differentiate tumor tissues from normal tissues in the A549 tumor-bearing mouse model and distinguish normal lung tissues from cancerous tissues in humans. Thus, the multimode polarity-sensitive fluorescent probe holds a robust tool for AKI and tumor evaluation in cells and animals as well as provides new insights into lung cancer diagnosis in clinical.

A novel red AIE fluorescent probe for ratiometric detection of carbon monoxide in vitro and in vivo.

As a significant signaling gas molecule, carbon monoxide (CO) has a crucial impact on various physiological and pathological processes in organisms, particularly in oxidative stress processes. Hence, designing and synthesizing a fluorescent probe that can effectively image CO in vivo holds immense significance. In this work, under the guidance of density functional theory (DFT) and time-dependent density functional theory (TDDFT), we designed and synthesized a red aggregation-induced emission (AIE) fluorescent probe THBTA-CO for CO detection and imaging. The fluorescent probe displayed green fluorescence emission at 535 nm before the CO response. However, upon CO response, with the involvement of Pd2+, the probe emitted red fluorescence at 630 nm. Furthermore, we successfully demonstrated the potential of THBTA-CO in visualizing both exogenous and endogenous CO in living cells. Significantly, THBTA-CO was effectively employed to image CO in lipopolysaccharide (LPS)-induced oxidative stress in mice. These findings convincingly establish THBTA-CO as a promising fluorescent probe for CO sensing and imaging, thereby facilitating a better understanding of CO's role in biomedical research.

A new ratiometric AIE fluorescent probe for detecting cysteine in food samples and imaging in the biological system

l-Cysteine (Cys) plays a vital part in the food industry and biological processes. Herein, a novel ratiometric fluorescent probe NFA with aggregation-induced emission (AIE) property was developed to discriminate Cys from Hcy and GSH. The probe showed a ratiometric fluorescence response to Cys with the emission wavelength shifted from 450 nm to 495 nm. Probe NFA possessed good advantages in the detection of Cys including wide linear range (0–100 μM), low detection limit (0.21 μM), and rapid response time (within 2 min). Compared with previous reports, this is the first ratiometric probe that achieves the quantitative detection of Cys in different food samples in real-time (cabbage, bamboo shoots, lotus root, garlic, apple, pear, milk powder, and liquid milk). Moreover, NFA is successfully applied for ratiometric image endogenous and exogenous Cys in HeLa cells and zebrafish which demonstrated its practical biological application.

A novel aggregation-induced emission fluorescent probe to visualize peroxynitrite levels during Golgi stress

Peroxynitrite (ONOO-), an endogenous reactive oxygen species (ROS), can cause a variety of diseases in organisms at high levels. Golgi oxidative stress produces a large number of ROS, and the quantitative detection of various ROS is of great significance to study Golgi oxidative stress. Therefore, accurate detection of ONOO- level in Golgi is important to reveal the mechanism of ONOO- in living organisms. Here, we developed a Golgi-targeted aggregation-induced emission (AIE) fluorescent probe Gol-ONOO- to detect ONOO- in cells. The probe Gol-ONOO- has the advantages of instant response to ONOO-, high selectivity, low detection limit (250 nM) and large Stoke's shift (180 nm). Most importantly, the probe Gol-ONOO- monitored the increase of ONOO- level caused by monensin-induced oxidative stress in the Golgi apparatus, and it was the first time to realize ONOO- imaging in the Golgi apparatus.

A novel AIE fluorescent probe for the monitoring of aluminum ions in living cells and zebrafish.

A novel fluorescent probe BTD with aggregation induced emission (AIE) characteristics for the monitoring of Al3+ was developed. This fluorescent probe could be used to detect Al3+ in aqueous solution under mild conditions, along with high sensitivity and high selectivity. The detection limit of the probe BTD for Al3+ is as low as 3.25 nM, which is below the WHO recommendation concentration (7.41 μM) for drinking water. Furthermore, this probe was successfully applied to the sensing of Al3+ in living cells and zebrafish.

A Schiff-based AIE fluorescent probe for Zn2+ detection and its application as “fluorescence paper-based indicator”

A Schiff-based aggregation induced emission (AIE) fluorescent probe with excited intramolecular proton transfer (ESIPT) mechanism was synthesized by grafting 2-hydrazinobenzothiazole onto 2,6-diformyl-4-methylphenol. The probe recognizes Zn2+ selectively and sensitively, accompanied by a significant fluorescence emission increasement change from light yellow-green to strong green. Additionally, a stabilization time of at least 30 min was kept in the recognition process. Besides, a linear relationship was observed between the concentration of Zn2+ and the fluorescence intensity at 525 nm (0.05–10 µM). And thus, the probe can detect Zn2+ quantitatively in aqueous solution with a low detection limit of 1.9 × 10-8 M. Based on the AIE property and the selective recognition of Zn2+, SCH was strategically loaded on the filter paper to develop a novel paper-based indicator for on-site and high-efficiency detection of Zn2+. The results showed that the paper-based indicator could be conveniently applied to the visual inspection of Zn2+ as expected and SCH in the paper-based indicators fortunately exhibited a better stability. Furthermore, our comprehensive application evaluations have confirmed that SCH was capable of detecting Zn2+ in real water samples and imaging Zn2+ in living cells roundly.

A novel turn-on type AIE fluorescent probe for highly selective detection of cysteine/homocysteine and its application in living cells

Biothiols, associated with multiple physiological and pathological processes, have structural similarities. Monitoring Biothiols selectively in organisms is of great significance. Burdened by the aggregation-caused quenching (ACQ) effect, the applications of conventional biothiols fluorescent probes are extremely limited. Herein, we developed a “turn-on” type aggregation-induced emission (AIE) fluorescent probe BQM-NBD, which was composed of a BQM-OH fluorophore molecule with AIE effect and the recognition group 7-nitro-1,2,3-benzoxadiazole (NBD). Non-fluorescent BQM-NBD produces strong fluorescence after the addition of cysteine (Cys) or homocysteine (Hcy). BQM-NBD exhibited excellent linearity for selective detection of Cys (0–100 Μm) and Hcy (0–50 μM) with detection limits of 6.0 × 10−8 M and 8.4 × 10−8 M, respectively. Simultaneously, after treatment with glutathione (GSH), it appeared no fluorescence. The results demonstrated BQM-NBD exhibited good selectivity to Cys/Hcy. Furthermore, BQM-NBD was successfully performed in the imaging of Cys in living cells with low cytotoxicity, which provides a feasible strategy for the selective detection of Cys in the living system.

BF2 group chelated AIE fluorescent probe for polarity mapping of lipid droplets in cells and in vivo

Lipid droplets (LDs), are multi-functional organelles with the storage of neutral lipids and proteins, participating in various of physiological processes. However, abnormal of LDs in morphology and numbers always lead to multiple diseases, including cancer, viral infection, obesity, inflammation. To better understand the physiological function of LDs in living cells, we designed two new fluorescent probes LDs-CA and LDs-BCA based on the triphenylamine and coumarin fluorophores to monitor LDs polarity and numbers variation in this work. The one-step strategy for the regulation of BF2 group realized a gratifying in emission wavelengths from orange fluorescence of LDs-CA to the red fluorescence of LDs-BCA, surprisingly. The two novel probes showed strong positive solvatochromism effect in different solvents and exhibited the aggregation-induced emission (AIE) effect. Based on the above excellent optical properties, LDs-CA and LDs-BCA were applied for imaging of the LDs with high overlap coefficient when co-stained with commercial dyes, respectively. The probes of LDs-CA and LDs-BCA provided an intuitive method to visualize the dynamic changes of LDs in morphology, size, and numbers under nutritionalstimulation, affording a powerful tool for fluorescence visualization of LDs related biological processes. Notably, the near-infrared emissive probe LDs-BCA successfully imaged the gastric fat in living obese mouse, which may provide a new idea for medical diagnostics.

A near-infrared AIE fluorescent probe for myelin imaging: From sciatic nerve to the optically cleared brain tissue in 3D

Myelin, the structure that surrounds and insulates neuronal axons, is an important component of the central nervous system. The visualization of the myelinated fibers in brain tissues can largely facilitate the diagnosis of myelin-related diseases and understand how the brain functions. However, the most widely used fluorescent probes for myelin visualization, such as Vybrant DiD and FluoroMyelin, have strong background staining, low-staining contrast, and low brightness. These drawbacks may originate from their self-quenching properties and greatly limit their applications in three-dimensional (3D) imaging and myelin tracing. Chemical probes for the fluorescence imaging of myelin in 3D, especially in optically cleared tissue, are highly desirable but rarely reported. We herein developed a near-infrared aggregation-induced emission (AIE)-active probe, PM-ML, for high-performance myelin imaging. PM-ML is plasma membrane targeting with good photostability. It could specifically label myelinated fibers in teased sciatic nerves and mouse brain tissues with a high-signal-to-background ratio. PM-ML could be used for 3D visualization of myelin sheaths, myelinated fibers, and fascicles with high-penetration depth. The staining is compatible with different brain tissue-clearing methods, such as ClearT and ClearT2 The utility of PM-ML staining in demyelinating disease studies was demonstrated using the mouse model of multiple sclerosis. Together, this work provides an important tool for high-quality myelin visualization across scales, which may greatly contribute to the study of myelin-related diseases.

TEPP-46-Based AIE Fluorescent Probe for Detection and Bioimaging of PKM2 in Living Cells.

Pyruvate kinase (PK) M2 (PKM2), a glycolytic enzyme, is a hallmark of different types of tumors and plays a significant role in the Warburg effect. However, there is no fluorescent probe for PKM2 that has been reported yet. In this study, TEPC466, a novel TEPP-46-based aggregation-induced emission (AIE) probe for the detection of PKM2, was designed, synthesized, and fully characterized by 1H NMR, 13C NMR, and high-resolution mass spectrometry. When the fluorescent agent, coumarine, was conjugated to TEPP-46, the bioprobe TEPC466 showed a high degree of selectivity and sensitivity for the detection of PKM2 protein via the AIE effect. TEPC466 was then successfully applied in imaging the PKM2 protein in colorectal cancer cells with low toxicity. Moreover, structure-based modeling and the PK activity assay confirmed that TEPC466 has a better binding with PKM2 than TEPP-46, which suggests that TEPC466 could also be a good agonist of PKM2. Taken together, the bioprobe shows potential in selective detection of PKM2 and provides a useful tool for cancer diagnosis and therapy.

A stable hydrazine click fluorescent probe based on photo switch

One novel aggregation induced emission (AIE) fluorescent probe for hydrazine (N2H4) (T) was synthesized. This is an optically controlled process. The probe is very stable before light, which is different from many probes with ester bonds that are easily hydrolyzed during storage. Only under ultraviolet (UV) light irradiation, T responded to N2H4 rapidly in aqueous solution along with the fluorescence change from yellow to blue. The detection limit is as low as 0.25 μM, and it works well at a wide pH range (3–10) in aqueous solutions. Bio-imaging of N2H4 in living cell demonstrated a favorable biocompatibility. Moreover, the optically controlled mechanism was exploited. The result indicated that the Schiff base structure of T would be twisted under UV light irradiation, which loosened the original aggregation state. Consequently, T became more accessible to N2H4. That is, aggregation state of T is inactive, only in the presence of UV light the reactivity could be activated. Interestingly, the torsion of this compound can be restored by visible light irradiation or heating. This is the first report about optically controlled AIE fluorescent probe.