Rapid quantitative evaluation of total polar materials (TPM) in frying oil based on an "off-on" fluorescence viscosity response probe.

The content of total polar material (TPM) is considered as a comprehensive indicator to evaluate the quality of edible oils which should be discarded and no longer be used when TPM content exceeding 27 %. Nevertheless, there is currently a lack of a convenient and efficient TPM detection method, which is a meaningful challenge. With the increase of TPM content, the viscosity of frying oil grows, and the two maintain a satisfactory positive correlation. Consequently, an "off-on" fluorescence probe TCF-PR method based on viscosity-response has been developed. There exists a good linear relationship between the fluorescence intensity of the probe and the TPM content of soybean oil ((R2 = 0.9936) and salad oil (R2 = 0.9878), accompanying with the advantage of fast response (3 s), which means the rapid detection of TPM can be realized to determine the quality of frying oil in the field of food safety.

Ketocyanine-Based Fluorescent Probe Revealing the Polarity Heterogeneity of Lipid Droplets and Enabling Accurate Diagnosis of Hepatocellular Carcinoma.

Hepatocellular carcinoma (HCC) has gradually become a pronoun for terrifying death owing to its high mortality rate. With the progression of HCC, lipid droplets (LDs) in HCC cells exhibit specific variations such as increased LDs number and decreased polarity, which can serve as the diagnostic target. However, developing an effective method to achieve HCC diagnosis and reveal LDs polarity heterogeneity is still a crucial challenge. Herein, the first high-performance LDs-targeting probe (1) is reported based on ketocyanine strategy with ultrasensitive polarity-responding ability and near-infrared emission. Probe 1 shows excellent sensitivity to polarity parameter Δf (0.027-0.290) with 808-fold fluorescence enhancement and the emission wavelength red-shifts 91 nm. In HCC cells, probe 1 shows a 2.5- to 5.9-fold fluorescence enhancement compared with normal and other cancer cells which exceeds clinical threshold of 2.0, indicating probe 1 can distinguish HCC cells. The LDs polarity heterogeneity is revealed and it displays a sequence, HCC cells < other cancer cells < normal cells, which may provide useful insight to engineer LDs-targeting probes for HCC cell discrimination. Finally, probe 1 realizes accurate HCC diagnosis on the cellular, organ, and in vivo levels, providing a satisfying tool for clinical HCC diagnosis and surgical navigation.

A Silicon-Rhodamine-Based Heavy-Atom-Free Photosensitizer for Mitochondria-targeted Photodynamic Therapy.

Silicon-xanthene derivatives (SiXs) have gained popularity in the field of bioimaging due to their advantageous far-red to near-infrared (NIR) absorption and emission wavelengths, notable brightness (ε × Φ), inherent mitochondrial targeting properties and high photo-stability, making them an excellent candidate for photodynamic therapy (PDT). Nevertheless, the utilization of SiXs as photosensitizers (PSs) for PDT in cancer treatment remains largely unexplored, primarily due to their limited capacity to generate cytotoxic reactive oxygen species (ROS). However, the potential of SiXs in PDT warrants further investigation. In this study, utilizing the spin-orbit charge transfer-induced intersystem crossing (SOCT-ISC) mechanism, we reported one novel heavy-atom-free, mitochondria-targeted, silicon-rhodamine-based photosensitizer (SiR-PXZ), which demonstrated excellent biocompatibility, minimal dark toxicity, favorable water-solubility and stability, and considerable singlet oxygen quantum yield under 660 nm light irradiation (ΦΔ = 0.16 in air-saturated PBS). Moreover, SiR-PXZ could be rapidly taken up by the mitochondria and efficiently induced apoptosis of cancer cells with an IC50 value of 1.2 µM. The in vivo studies showed that SiR-PXZ exhibited excellent anti-tumor effects, making it potentially valuable for clinical application. This study offers a source of ideas for the construction of SiXs-based photosensitizers for photodynamic cancer treatment in the future.

Light-responsive benzobisthiazole as oxidase mimic for rapid determination of glutathione in food and vegetable.

Accurate determination of glutathione (GSH) in food and vegetable is significant to instruct the appropriate supplementation of GSH in the human body. Light-responsive enzyme mimics have been widely used in detecting GSH due to controllable temporal and spatial accuracy. However, exploring a potential organic mimic enzyme with excellent catalytic efficiency keeps challenging. Herein, a benzobisthiazole organic oxidase mimic was successfully prepared by a simple and low-cost method. Based on its high light-responsive oxidase-like activity, it was used for high reliable colorimetric determination of GSH in food and vegetable for only 1 min with a large linear range of 0.02-30 µM and a low detection limit of 5.3 nM. This study provides a novel strategy to obtain powerful light-responsive oxidase mimics and holds great potential for rapid and accurate detection of GSH in food and vegetables.

Carbon dots as light-responsive oxidase-like nanozyme for colorimetric detection of total antioxidant capacity in fruits.

Evaluation of total antioxidant capacity (TAC) in fruits is essential for dietary guidance and health monitoring. Here, we have exploited light-response carbon dots (CDs) as oxidase-like nanozyme to determine the TAC of fruits. The CDs possess excellent oxidase-like activity with light stimulation due to the accelerated intramolecular charge transfer caused by abundant electron donating/drawing groups in precursors. The scavenger experiment reveals that the catalytic intermediate could be hydroxyl radical, which can oxidize the colorimetric substrate. With the introduction of antioxidants, the oxidization of colorimetric substrate will be alleviated due to the scavenging of this intermediate by antioxidants. Based on this, we have successfully detected three antioxidants and obtained TAC of fruits with desirable results. This work affords a rapid, cost-effective and convenient analysis tool for TAC, as well as building a strong bridge between CDs and the development of photo-responsive oxidase-like nanozymes.

High-fidelity carbon dots polarity probes: revealing the heterogeneity of lipids in oncology.

Polarity is an integral microenvironment parameter in biological systems closely associated with a multitude of cellular processes. Abnormal polarity variations accompany the initiation and development of pathophysiological processes. Thus, monitoring the abnormal polarity is of scientific and practical importance. Current state-of-the-art monitoring techniques are primarily based on fluorescence imaging which relies on a single emission intensity and may cause inaccurate detection due to heterogeneous accumulation of the probes. Herein, we report carbon dots (CDs) with ultra-sensitive responses to polarity. The CDs exhibit two linear relationships: one between fluorescence intensity and polarity and the other between polarity and the maximum emission wavelength. The emission spectrum is an intrinsic property of the probes, independent of the excitation intensity or probe concentration. These features enable two-color imaging/quantitation of polarity changes in lipid droplets (LDs) and in the cytoplasm via in situ emission spectroscopy. The probes reveal the polarity heterogeneity in LDs which can be applied to make a distinction between cancer and normal cells, and reveal the polarity homogeneity in cytoplasm.

Quantitative Structure-Activity Relationship Enables the Rational Design of Lipid Droplet-Targeting Carbon Dots for Visualizing Bisphenol A-Induced Nonalcoholic Fatty Liver Disease-like Changes.

Lipid droplets (LDs) play indispensable roles in numerous physiological processes; hence, the visualization of the dynamic behavior of LDs in living cells is of great importance in physiological and pathological research. In this article, the quantitative structure-activity relationship (QSAR) theory was employed as an effective design strategy for the development of organelle-targeting carbon dots (CDs). The lipid-water partition coefficient (Log P) of the QSAR was adopted as a key parameter to predict the cellular uptake and subcellular localization of CDs in live cells. By carefully adjusting the molecular structure and lipophilicity of the precursors, p-phenylenediamine-derivatized nucleolus-targeting hydrophilic CDs were converted to lipophilic CDs [4-piperidinoaniline (PA) CDs] with inherent LD-targeting performance. The PA CDs were able to indicate the dynamic behavior of LDs and visualize the changes of bisphenol A-induced nonalcoholic fatty liver disease-like changes in a cellular model. The QSAR strategy of CDs demonstrated here is expected to be increasingly exploited as a powerful design tool for developing various organelle-targeting CDs.

Low Polarity-Triggered Basic Hydrolysis of Coumarin as an AND Logic Gate for Broad-Spectrum Cancer Diagnosis.

The ability to accurately diagnose cancer is the cornerstone of early cancer treatment. The mitochondria in cancer cells maintain a higher pH and lower polarity relative to that in normal cells. A probe that reports signals only when both conditions are met may provide a reliable method for cancer detection with reduced false positives. Here, we construct an AND logic gate fluorescent probe using mitochondrial microenvironments as inputs. Utilizing the hydrolysis of a coumarin scaffold, the probe generates fluorescence signals ("ON") only when high pH (>7.0) and low polarity conditions exist simultaneously. Additionally, the higher mitochondrial membrane potential in cancer cells provides an additional level of selectivity because probe has increased affinity for cancer cell mitochondria. These capabilities endow the probe with a high contrast fluorescence diagnosis ability of cancer at cellular and tissue levels (as high as 51.9 fold), which is far exceeding the clinic threshold of 2.0 fold.

Runx1/miR-26a/Jagged1 signaling axis controls osteoclastogenesis and alleviates orthodontically induced inflammatory root resorption.

BACKGROUND: MicroRNAs (miRNAs) are involved in the regulation of osteoclast biology and several pathogenic progression. This study aimed to identify the role of miR-26a in osteoclastogenesis and orthodontically induced inflammatory root resorption(OIIRR). METHODS: Rat orthodontic tooth movement (OTM) model was established by ligating a closed coil spring between maxillary first molar and incisor, and 50 g orthodontic force was applied to move upper first molar to middle for 7 days. Human periodontal ligament (hPDL) cells were isolated from periodontium of healthy donors, and then subjected to compression force (CF) for 24 h to mimic an in vitro OTM model. The levels of associated factors in vivo and in vitro were measured subsequently. RESULT: The distance of tooth movement was increased and root resorption pits were occurred in rat OTM model. The expression of miR-26a was decreased in vivo and vitro experiments. CF treatment enhanced the secretion of inflammatory factors receptor activator of nuclear factor-kappa B ligand (RANKL) and IL-6, osteoclast marker levels, and the number of tartrate-resistant acid phosphatase (TRAP)-positive osteoclasts, while miR-26a overexpression reversed these results. Furthermore, miR-26a overexpression inhibited the osteoclastogenesis and rescued the root resorption in OTM rats through inhibition of Jagged1. Additionally, Runx1 could bind to miR-26a promoter and promote its expression, thereby suppressing the osteoclastogenesis. CONCLUSION: We concluded that Runx1/miR-26a/Jagged1 signaling axis restrained osteoclastogenesis and alleviated OIIRR.

The recent development of fluorescent probes for the detection of NADH and NADPH in living cells and in vivo.

Reduced nicotinamide adenine dinucleotide (NADH) and its phosphate ester (NADPH) participate in numerous metabolic processes in living cells as electron carriers. The levels of NADH and NADPH in a cell are closely related to its metabolic and pathological state. It is important to monitor the levels of NADH and NADPH in living cells and in vivo in real-time. This review mainly focuses on fluorescent probes developed for monitoring NADH and NADPH in living cells and in vivo, and classifies them according to the recognition units. These fluorescence probes can rapidly respond to changes in NADH and NADPH levels without interference from other biomolecules, both in cell culture and in vivo. These probes have been employed to monitor NADH and NADPH levels in living cells, tumor spheroids, and in vivo; moreover, some of them can be used to discriminate normal cells from cancer cells, and detect cancer cell death due to reductive stress induced by natural antioxidants. This review is expected to inspire the generation of novel fluorescent probes for the detection of NADH and NADPH, and stimulate more attention in the development of fluorescent probes based on carbon dots and nanoparticles, as well as metal complex-based, time-gated luminescent probes for monitoring NADH and NADPH in both living cells and in vivo.

Engineering a lipid droplet targeting fluorescent probe with a large Stokes shift through ester substituent rotation for in vivo tumor imaging.

Great progress has been made with lipid droplet targeting fluorescent probes in a wide range of biomedical fields. However, the Stokes shifts of most fluorescent probes are relatively small, leading to strong biological background fluorescence, poor signal-to-noise ratios, self-quenching in the commonly used microscopes and the need for in vivo imaging systems. In this manuscript, the ester substituent rotation of fluorophores was supposed to result in a large Stokes shift via steric hindrance effects and resonance effects. A lipid droplet targeting fluorescent probe 1 was achieved by simply appending a 4-substituted ester group onto the classic coumarin fluorophore. Probe 1 exhibited large Stokes shifts (122 to 184 nm) in both high polarity and weak polarity solvents with good lipophilicity and polarity responsive ability (3500 fold fluorescence enhancement). Probe 1 was suitable for washing-free imaging of lipid droplets in living cells with excellent specificity and rapidity (<2 min). Probe 1 was applied for distinguishing cancer cells from normal cells by taking advantage of the abnormalities of lipid droplets of cancer cells. Due to its huge Stokes shift, probe 1 can be used for in vivo tumor imaging by the excitation of a blue laser, which is important for biomedical research.

One Stone, Three Birds: pH Triggered Transformation of Aminopyronine and Iminopyronine Based Lysosome Targeting Viscosity Probe for Cancer Visualization.

The lysosomes of cancer cells have lower pH and higher viscosity than those of normal cells. These features can be used as sensitive and selective markers for cancer diagnosis. In this work, a pH and viscosity dual responsive lysosome targeting fluorescent probe 1 was designed based on the transformation of amino- and imino- forms of pyronine and the twisted intramolecular charge shuttle (TICS) sensing mechanism. Live cancer cells and tumors were effectively distinguished from normal cells and organs through fluorescence imaging of probe 1, which indicated that probe 1 could serve as an effective tool for visualization of tumors at organ level with high selectivity.

Carbon-Dipyrromethenes: Bright Cationic Fluorescent Dyes and Potential Application in Revealing Cellular Trafficking of Mitochondrial Glutathione Conjugates.

Boron-dipyrromethenes (Bodipys), since first reported in 1968, have emerged as a fascinating class of dyes in the past few decades due to their excellent photophysical properties including bright fluorescence, narrow emission bandwidth, resistance to photobleaching, and environment insensitivity. However, typical Bodipys are highly lipophilic, which often results in nonfluorescent aggregates in aqueous solution and also severely limits their bioavailability to cells and tissues. In this work, based on a simple one-atom B → C replacement in the Bodipy scaffold, we present a new class of carbon-dipyrromethenes (Cardipys for short) fluorescent dyes with tunable emission wavelengths covering the visible and near-infrared regions. These Cardipys not only retain the excellent photophysical properties of conventional Bodipys but also show improved water solubility and photostability due to their cationic character. Moreover, the cationic character also makes them extremely easy to penetrate the cell membrane and specifically accumulate into mitochondria without resorting to any mitochondria-targeted groups. Interestingly, several Cardipys bearing active styryl groups could serve as fluorescent indicators to map cellular trafficking of the glutathione conjugates produced within mitochondria under the catalysis of glutathione S-transferase (GST), thus showing potential in either exploring the detoxification mechanism of the mitochondrial GST/GSH system or evaluating the drug resistance of cancer cells that is closely related with GST activity.

Fluorescent Carbon Dots for in Situ Monitoring of Lysosomal ATP Levels.

Monitoring the ATP levels in lysosomes in situ is crucial for understanding their involvement in various biological processes but remains difficult due to the interference of ATP in other organelles or the cytoplasm. Here, we report a lysosome-specific fluorescent carbon dot (CD), which can be used to detect ATP in acidic lysosomes with "off-on" changes of yellow fluorescence. These CDs were successfully applied in real-time monitoring of the fluctuating concentration of lysosomal ATP induced by drug stimulation (e.g., chloroquine, etoposide, and oligomycin). Because of the excellent specificity, these CDs are promising agents for drug screening and medical diagnostics through lysosomal ATP monitoring.

RNA-responsive fluorescent carbon dots for fast and wash-free nucleolus imaging.

RNA as a carrier of genetic information plays a critical role in various physiological processes. RNA-rich nucleolus is usually employed as an important biomarker for many malignant diseases. Herein, RNA-responsive fluorescent carbon dots (CDs) were synthesized by a simple microwave method. Due to the presence of cationic benzothiazolium groups in the CDs, a "turn-on" fluorescence signal was achieved between CDs and RNA. The CDs exhibit excellent RNA selectivity and a good linear relationship with a detection limit of 0.62 µg/mL. The small particle size, polarity sensitivity and RNA response behavior of CDs realized fast and wash-free nucleolus imaging effectively. Overall, these CDs provide a powerful potential tool for monitoring cell nucleus activity and elucidating RNA dynamics.

A rhodol-hemicyanine based ratiometric fluorescent probe for real-time monitoring of glutathione dynamics in living cells.

Glutathione (GSH) plays crucial roles in various physiological and pathological processes. The fluctuation of the GSH level is closely associated with a variety of diseases and cellular functions. Hence, it is important to real-time monitor the fluctuation of GSH in living cells. In this work, we presented a rhodol-hybridized hemicyanine fluorophore (RdH) as a selective, rapid-response, ratiometric, and reversible fluorescent probe for intracellular GSH (t1/2 = 89 ms, Kd = 1.42 mM). The imaging assays in living cells revealed that RdH could be used to real-time monitor GSH dynamics in A549 cells under a laser scanning confocal microscope by ratiometric fluorescence changes.

Lysosome-targeted carbon dots for ratiometric imaging of formaldehyde in living cells.

Formaldehyde (FA) is involved in many biological processes and is closely connected with many diseases including Alzheimer's disease and cancer. Therefore, methods for sensitive and selective detection of FA in living cells are highly demanded. As a new class of carbon nanomaterials, carbon dots (CDs) have attracted great attention owing to their robust photostability, good biocompatibility and environmental friendliness. In this manuscript, the first lysosome-targeted CDs for ratiometric fluorescence detection of FA were efficiently prepared from dexamethasone and 1,2,4,5-tetraaminobenzene through the microwave-assisted hydrothermal method. These CDs show highly selective and sensitive sensing ability towards FA with fast response and great changes of ratio values. The CDs exhibit robust photostability and good biocompatibility and were successfully employed in ratiometric fluorescence bioimaging of FA fluctuations in lysosomes of living cells, which demonstrates their great practicability in FA-related bioanalysis and biological studies.

Synthesis of Luminescent Carbon Dots with Ultrahigh Quantum Yield and Inherent Folate Receptor-Positive Cancer Cell Targetability.

Carbon dots (CDs) have a wide range of applications in chemical, physical and biomedical research fields. We are particularly interested in the use of CDs as fluorescence nanomaterials for targeted tumor cell imaging. One of the important aspects of success is to enhance the fluorescence quantum yields (QY) of CDs as well as increase their targetability to tumor cells. However, most of the reported CDs are limited by relative low QY. In the current study, for the first time, one-step synthesis of highly luminescent CDs by using folic acid (FA) as single precursor was obtained in natural water through hydrothermal method. The as-prepared CDs exhibited QY as high as 94.5% in water, which is even higher than most of organic fluorescent dyes. The obtained CDs showed excellent photoluminescent activity, high photostability and favorable biocompatibility. The FA residuals in CDs led to extraordinary targetability to cancer cells and promoted folate receptor-mediated cellular uptake successfully, which holds a great potential in biological and bioimaging studies.

Construction of a selective fluorescent probe for GSH based on a chloro-functionalized coumarin-enone dye platform.

Glutathione (GSH), the most abundant intracellular biothiol, protects cellular components from damage caused by free radicals and reactive oxygen species (ROS), and plays a crucial role in human pathologies. A fluorescent probe that can selectively sense intracellular GSH would be very valuable for understanding of its biological functions and mechanisms of diseases. In this work, a 3,4-dimethoxythiophenol-substituted coumarin-enone was exploited as a reaction-type fluorescent probe for GSH based on a chloro-functionalized coumarin-enone platform. In the probe, the 3,4-dimethoxythiophenol group functions not only as a fluorescence quencher through photoinduced electron transfer (PET) to ensure a low background fluorescence, but also as a reactive site for biothiols. The probe displays a dramatic fluorescence turn-on response toward GSH with the long-wavelength emission (600 nm) and significant Stokes shift (100 nm). The selectivity of the probe toward GSH over cysteine (Cys), homocysteine (Hcy), and other amino acids was demonstrated. Assisted by laser-scanning confocal microscopy, we have demonstrated that the probe could specifically sense GSH over Cys/Hcy in human renal cell carcinoma SiHa cells.

A mitochondria-targetable fluorescent probe for peroxynitrite: fast response and high selectivity.

A mitochondria-targetable fluorescence probe, methyl(4-hydroxyphenyl)amino-substituted pyronin (1), was exploited, which could highly selectively sense peroxynitrite (ONOO(-)) within seconds.