Search

Sulfur dioxide (SO 2) is a significant gas signaling molecule in organisms, and viscosity is a crucial parameter of the cellular microenvironment. They are both involved in regulating many physiological processes in the human body. However, abnormalities in SO 2 and viscosity levels are associated with various diseases, such as cardiovascular disease, lung cancer, respiratory diseases, neurological disorders, diabetes and Alzheimer's disease. Hence, it is essential to explore novel and efficient fluorescent probes for simultaneously monitoring SO 2 and viscosity in organisms. We selected quinolinium salt with good stability, high fluorescence intensity, good solubility and low cytotoxicity as the fluorophore and developed a highly sensitive ratiometric probe QQD to identify SO 2 and viscosity changes based on Förster resonance energy transfer/twisted intramolecular charge transfer (FRET/TICT) mechanism. Excitingly, compared with other probes for SO 2 detection, QQD not only identified HSO 3 −/SO 3 2− with a large Stokes shift (218 nm), low detection limit (1.87 μM), good selectivity, high energy transfer efficiency (92 %) and wide recognition range (1.87–200 μM), but also identified viscosity with a 26-fold fluorescence enhancement and good linearity. Crucially, QQD was applied to detect HSO 3 −/SO 3 2− and viscosity in actual water and food samples. In addition, QQD had low toxicity and good photostability for imaging HSO 3 −/SO 3 2− and viscosity in cells. These results confirmed the feasibility and reliability of QQD for HSO 3 −/SO 3 2− and viscosity imaging and environmental detection. We reported a unique ratiometric probe QQD for detecting HSO 3 −/SO 3 2− and viscosity based on the quinolinium skeleton. In addition to detecting HSO 3 −/SO 3 2− and viscosity change in actual water and food samples, QQD could also monitor the variations of HSO 3 −/SO 3 2− and viscosity in cells, which provided an experimental basis for further exploration of the role of SO 2 derivatives and viscosity in biological systems. [Display omitted] • A dual-function fluorescent probe was designed for detecting SO 2 and viscosity. • QQD had large Stokes shift of 218 nm and wide detection rang of 1.87–200 μM. • QQD showed high sensitivity and selectivity. • QQD achieved the dual colorimetric and ratiometric fluorescent strategy. • QQD achieved the application of foods, water samples and living cells. [ABSTRACT FROM AUTHOR]

Detecting and neutralizing Pd2+ ions are a significant challenge due to their cytotoxicity, even at low concentrations. To address this issue, various chemosensors have been designed for advanced detection systems, offering simplicity and the potential to differentiate signals from different analytes. Nonetheless, these chemosensors often suffer from limited emission response and complex synthesis procedures. As a result, the tracking and quantification of residual palladium in biological systems and environments remain challenging tasks, with only a few chemosensing probes available for commercial use. In this paper, a straightforward approach for the selective detection of Pd2+ ions is proposed, which involves the design, synthesis, and utilization of a propargylated naphthalene-derived probe (E)-N'-((2-(prop-2-yn-1-yloxy)naphthalen-1-yl)methylene)benzohydrazide (NHP). The NHP probe exhibits sensitive dual-channel colorimetry and fluorescence Pd2+ detection over other tested metal ions. The detection process is performed through a catalytic depropargylation reaction, followed by an excited state intramolecular proton transfer (ESIPT) process, the detection limit is as low as 11.58 × 10−7 M under mild conditions. Interestingly, the resultant chemodosimeter adduct (E)-N'-((2-hydroxynaphthalen-1-yl)methylene)benzohydrazide (NHH) was employed for the consecutive detection of CN− ions, exhibiting an impressive detection limit of 31.79 × 10−8 M. Validation of both detection processes was achieved through 1H nuclear magnetic resonance and density functional theory calculations. For real-time applications of the NHP and NHH probes, smartphone-assisted detection, and intracellular detection of Pd2+ and CN− ions within HeLa cells were studied. This research presents a novel naphthalene derivative for visually detecting environmentally toxic Pd2+ and CN− ions. The synthesized probe selectively binds to Pd2+, forming a chemodosimeter. It successfully detects CN− ions through colorimetry and fluorimetry, offering a low detection limit and quick response. Notably, it's the first naphthalene-based small molecule to serve as a dual probe for toxic analytes - palladium and cyanide. Moreover, it effectively detects Pd2+ and CN− intracellularly in cancer cells. [Display omitted] • Probe NHP selectively detects Pd2+ and forms chemodosimeter adduct NHH , showing a specific turn-on response to CN- ions. • The "off-on-off" ESIPT process led to the dual-channel detection of Pd2+ and CN− in an ethanol-H 2 O solution. • Consecutive detection, first of Pd2+ and then of CN-, showed naked-eye visibility, rapid response, and a low detection limit. • The study explored both on-site smartphone-based detection and intracellular detection of Pd2+ and CN- within HeLa cells. [ABSTRACT FROM AUTHOR]

Al exists naturally in the environment and is an important component in acidic soils, which harm almost all plants. Furthermore, Al is widely used in food additives, cosmetics, and medicines, resulting in living organisms ingesting traces of Al orally or dermally every day. Accordingly, Al accumulates in the body, which can cause negative bioeffects and diseases, and this concern is gaining increasing attention. Therefore, to detect and track Al in the environment and in living organisms, the development of novel Al-selective probes that are water-soluble and exhibit fluorescence at long wavelengths is necessary. In this study, an Al3+-selective fluorescent probe PSP based on a novel pyrone molecule was synthesized and characterized to detect and track Al in biological systems. PSP exhibited fluorescence enhancement at 580 nm in the presence of Al3+ in aqueous media. Binding analysis using Job's plot and structural analysis using 1H NMR showed that PSP formed a 1:1 complex with Al3+ at the two carbonyl groups of the dimethyl malonate of the pyrone ring. Upon testing in biological systems, PSP showed good cell membrane permeability, detected intracellular Al3+ in human breast cancer cells (MDA-MB-231), and successfully imaged accumulated Al3+ in Microcystis aeruginosa and the larvae of Rheocricotopus species. The novel Al3+-selective fluorescent probe PSP is highly effective and is expected to aid in elucidating the role of Al3+ in the environment and living organisms. [Display omitted] • Water-soluble fluorescent Al3+ probe PSP developed based on phenylsulfonyl-2-pyrone • PSP exhibited fluorescence enhancement toward Al3+ at 580 nm in aqueous media • PSP successfully detected accumulated Al3+ in breast cells and small aquatic organisms [ABSTRACT FROM AUTHOR]

Heavy metal pollution has become one of the world's most important environmental pollution, especially Hg2+ is enriched, it is easy to enter the human body through the food chain, bind to the sulfhydryl group in the protein, cause mercury poisoning. Traditional methods for detecting Hg2+ have obvious drawbacks, such as poor selectivity and long detection time. Fluorescence detection has attracted attention because of its good sensitivity and specificity detection ability. In previously reported probes for detecting Hg2+, Cu2+ often interferes. Therefore, it is of great practical significance to synthesize a fluorescent probe that can distinguish between Hg2+ and Cu2+. We have successfully synthesized the probe DFS, a fluorescent probe that can differentially detect Hg2+ and Cu2+, and the probe DFS has good selectivity and anti-interference ability for Hg2+ and Cu2+. The fluorescence intensity at 530 nm increased rapidly when Hg2+ was detected; during the Cu2+ detection, the fluorescence intensity at 636 nm gradually decreased, fluorescence quenching occurred, and the detection limits of Hg2+ and Cu2+ were 7.29 × 10−9 M and 2.13 × 10−9 M, respectively. Through biological experiments, it was found that probe DFS can complete the fluorescence imaging of Hg2+ and Cu2+ in Staphylococcus aureus and HUVEC cells, which has certain research value in the field of environmental monitoring and microbiology, and the probe DFS has low cytotoxicity, so it also has broad application prospects in the field of biological imaging. In addition, the probe DFS also has good applicability for Hg2+ and Cu2+ detection in actual samples. This is a fluorescent probe that can distinguish between Hg2+ and Cu2+, the fluorescence emission peak appears at 530 nm when Hg2+ is detected; when detecting Cu2+, fluorescence quenching occurs at 636 nm, the fluorescence emission peak distance between Hg2+ and Cu2+ differs by 106 nm. This reduces mutual interference between Hg2+ and Cu2+ during detection, it provides a new idea for the detection of Hg2+ and Cu2+. [Display omitted] • The probe with low limits of detection. • The probe enables differential detection of Hg2+ and Cu2+. • The probe exhibits good biopenetrability and biocompatibility. • The probe can qualitatively detect Hg2+ and Cu2+ in actual samples. [ABSTRACT FROM AUTHOR]

Cell surface glycans (CSGs) are essential for cell recognition, adhesion, and invasion, and they also serve as disease biomarkers. Traditional CSG recognition using lectins has limitations such as limited specificity, low stability, high cytotoxicity, and multivalent binding. Aptamers, known for their specific binding capacity to target molecules, are increasingly being employed in the biosensing of CSGs. Aptamers offer the advantage of high flexibility, small size, straightforward modification, and monovalent recognition, enabling their integration into the profiling of CSGs on living cells. In this review, we summarize representative examples of aptamer-based CSG biosensing and identify two strategies for harnessing aptamers in CSG detection: direct recognition based on aptamer-CSG binding and indirect recognition through protein localization. These strategies enable the generation of diverse signals including fluorescence, electrochemical, photoacoustic, and electrochemiluminescence signals for CSG detection. The advantages, challenges, and future perspectives of using aptamers for CSG biosensing are also discussed. [Display omitted] • The aptamer-based cell surface glycan biosensing with a potential future to facilitate clinical diagnostics. • The representative examples of aptamer-based cell surface glycan biosensing are summarized. • The design strategies for identifying cell surface glycan by aptamers are introduced. • The challenges and prospects of aptamer-based cell surface glycan biosensing are described. [ABSTRACT FROM AUTHOR]

Tyrosine kinase inhibitors (TKIs) are commonly used in tumor targeting therapy. However, the rapid analysis of TKIs remains a significant challenge, especially in complex biological fluid environments. In this work, we have constructed a supramolecular fluorescence sensor array based on a cucurbituril-dye host-guest complex. The binding affinity between the three complexes and each TKI is different, resulting in different cross-response signals of the complexes to the fluorescence of each TKI. Combined with linear discriminant analysis(LDA), five kinds of TKIs can be well identified. The supramolecular fluorescence sensor array could accurately identify and distinguish the five TKIs in water and could classify mixtures containing different concentrations of TKIs in serum. The concentration and Factor 1 exhibited a good linear relationship and the detection limit (LOD) was as low as 10−7 mol L−1. The method has good reproducibility and stability. In addition, the differentiation of four clinical concentrations of first-generation TKIs further validated the potential application of arrays in drug monitoring. Finally, our proposed array enabled drug imaging in living cells. Our array platform provided the foundation for the rapid and easy monitoring of 4-anilinoquinazoline TKIs. [Display omitted] • A supramolecular fluorescence array sensor was constructed based on the dye-cucurbit [8]uril host-guest complexes. • The sensor array can identify five 4-anilinequinoline TKIs. • Five 4-anilinequinolines TKIs in serum were detected by sensor array. [ABSTRACT FROM AUTHOR]

Human telomerase is a ribonucleoprotein complex that includes proteins and human telomerase RNA (hTR). Emerging evidence suggested that the expression level of hTR was high related with the development of tumor, so it is important to accurately detect the content of hTR. Optical control of DNAzyme activity shows a promising strategy for precise biosensing, biomedical imaging and modulation of biological processes. Although DNAzyme-based sensors can be controlled spatiotemporally by light, its application in the detection of hTR in living cells is still rare. Therefore, designing DNAzyme activity spatiotemporal controllable sensors for hTR detection is highly needed. We developed a UV light-activated DNAzyme-based nanoprobe for spatially accurate imaging of intracellular hTR. The proposed nanoprobe was named MDPH, which composed of an 8–17 DNAzyme (D) inactivated by a protector strand (P), a substrate strand (H), and MnO 2 nanosheets. The MnO 2 nanosheets can enhance the cellular uptake of DNA strands, so that MDPH probe can enter cells autonomously through endocytosis. Under the high concentration of GSH in cancer cells, MnO 2 nanosheets can self-generate cofactors to maintain the catalytic activity of DNAzyme. When exposing UV light and in presence of target hTR , DNAzyme could cleave substrate H, resulting in the recovery of fluorescence of the system. The cells imaging results show that MDPH probe could be spatiotemporally controlled to image endogenous hTR in cancer cells. With this design, telomerase RNA-specific fluorescent imaging was achieved by MDPH probe in both cancer and normal cells. Our probe made a promising new platform for spatiotemporal controllable intracellular hTR monitoring. This current method can be applied to monitor a variety of other biomarkers in living cells and perform medical diagnosis, so it may has broad applications in the field of medicine. We developed a UV light-activated DNAzyme-based nanoprobe for fluorescent imaging of hTR in living cells. This nanoprobe achieved spatiotemporally controlled intracellular hTR detection with high sensitivity and specificity. [Display omitted] • A novel DNAzyme-based nanoprobe was developed for sensing hTR with high sensitivity. • A spatiotemporal controllable hTR detection was achieved in living cells. • The nanocarrier of MnO 2 could self-generate cofactors to maintain the activity of DNAzyme. • This work can be applied to monitor a variety of biomarkers. [ABSTRACT FROM AUTHOR]

As a basic parameter of the intracellular microenvironment, viscosity is closely related to the development of cancer. Thus, it is necessary to utilize a sensitive tool to visualize the viscosity in tumor cells and mice, which is helpful for the diagnosis of cancer. Herein, a novel dual-modal probe (IX-V) that has a near-infrared fluorescence (NIRF) and photoacoustic (PA) response to viscosity is synthesized. In low viscosity media, the probe has no fluorescence. With the increase of viscosity, the fluorescence is produced in the near-infrared region due to the inhibition of the TICT process. At the same time, the probe shows different photoacoustic (PA) signals in different viscosity media. Most notably, the viscosity in tumor cells has been imaged successfully by the application of IX-V, and the probe can effectively distinguish cancer cells from normal cells co-cultured in one dish by the difference of fluorescence intensity. In addition, the probe has been used for dual-modal imaging (NIRF and PA) of viscosity in tumor mice, which provides a tool for exploring the relationship between viscosity and diseases. That is to say, IX-V can achieve complementary imaging effects and has great application prospects in the tumor diagnosis. [Display omitted] • A probe (IX-V) has a NIR fluorescence and photoacoustic response to viscosity. • IX-V shows high sensitivity and selectivity for viscosity over other analytes. • This probe can be used in visualizing viscosity change in various living cells. • IX-V can distinguish cancer cells from normal cells co-cultured in one dish. • IX-V is applied for monitoring the viscosity level in mice by dual-modal imaging. [ABSTRACT FROM AUTHOR]

A sensitive method for the detection of β-glucuronidase was established using functionalized carbon dots (β-CD-SiCDs) as fluorescent probes. The β-CD-SiCDs were found to be obtained through in situ autopolymerization by mixing the solutions of methyldopa, mono-6-ethylenediamine-β-cyclodextrin and N -(β-aminoethyl)-γ-aminopropyltrimethoxysilane at room temperature. The method has the characteristics of low energy consumption, simple and rapid. β-CD-SiCDs exhibited green fluorescence at 515 nm emission with a quantum yield of 7.9 %. 4-nitrophenyl-β-D-glucuronide was introduced as a substrate for β-glucuronidase to generate p -nitrophenol. Subsequently, p -nitrophenol self-assembled with β-CD-SiCDs through host-guest recognition to form a stable inclusion complex, resulting in the fluorescence quenching of β-CD-SiCDs. The linear range of β-CD-SiCDs for detecting β-glucuronidase activity was 0.5–60 U L−1 with a detection limit of 0.14 U L−1. For on-site detection, gel reagents were prepared by a simple method and the images were visualized and quantified by taking advantage of smartphones, avoiding the use of large instrumentation. The constructed fluorescence sensing platform has the benefits of easy operation and time saving, and has been successfully used for the detection of β-glucuronidase activity in serum and cell imaging. [Display omitted] • Amination induced in situ self-polymerization formation of β-CD-SiCDs without external energy. • β-CD-SiCDs can selectively recognize p -nitrophenol through host-guest recognition. • Smartphone-integrated hydrogel sensing platform was used to detect β-glucuronidase on site. • The approach is suitable for detecting β-glucuronidase in serum and bioimaging in cells. [ABSTRACT FROM AUTHOR]

Cellular heterogeneity poses a major challenge for tumor theranostics, requiring high-resolution intercellular bioanalysis strategies. Over the past decades, the advantages of electrochemical analysis, such as high sensitivity, good spatio-temporal resolution, and ease of use, have made it the preferred method to uncover cellular differences. To inspire more creative research, herein, we highlight seminal works in electrochemical techniques for biomolecule analysis and bioimaging. Specifically, micro/nano-electrode-based electrochemical techniques enable real-time quantitative analysis of electroactive substances relevant to life processes in the micro-nanostructure of cells and tissues. Nanopore-based technique plays a vital role in biosensing by utilizing nanoscale pores to achieve high-precision detection and analysis of biomolecules with exceptional sensitivity and single-molecule resolution. Electrochemiluminescence (ECL) technology is utilized for real-time monitoring of the behavior and features of individual cancer cells, enabling observation of their dynamic processes due to its capability of providing high-resolution and highly sensitive bioimaging of cells. Particularly, scanning electrochemical microscopy (SECM) and scanning ion conductance microscopy (SICM) which are widely used in real-time observation of cell surface biological processes and three-dimensional imaging of micro-nano structures, such as metabolic activity, ion channel activity, and cell morphology are introduced in this review. Furthermore, the expansion of the scope of cellular electrochemistry research by innovative functionalized electrodes and electrochemical imaging models and strategies to address future challenges and potential applications is also discussed in this review. [Display omitted] • Recent progress of electrochemical science biological research. • Overview of molecular detection techniques ranging from extracellular to intracellular levels. • Overview of electrochemical imaging techniques for monitoring of structural characteristics. [ABSTRACT FROM AUTHOR]

A multifunctional nucleoside-based AIEgens sensor (TPEPy-dU) was constructed for visual screening of Hg2+, determine to the reversible response of Fe3+ and biothiols, and applied for cell imaging, and drug-free bacterial killing. The TPEPy-dU displayed 10-folds fluorescence enhancement at 540 nm of emission in response to trace Hg2+ ions with 10 nM of LOD, which can be immediately quenched by adding Fe3+ or GSH/Cys-containing sulfhydryl groups. Moreover, their bacterial staining efficiency closely correlates with their antibacterial efficacy as they demonstrated comparatively higher antibacterial activity against Gram-positive bacteria than Gram-negative bacteria. The drug-free antibacterial results involved the stating prominent surface damages at the sites of interactions between bacterial cells and TPEPy-dU that were further verified by CLSM and SEM images. It can be applied as a potential fluorescent agent to explore the related antibacterial mechanisms for treating and monitoring bacterial infections in vivo due to their nontoxic nature. Compared with conventional sensors and antibacterial therapies, these findings elevated the synthetic strategies of fluorescent probes and represented an advanced antibacterial agent wearing quaternary ammonium cationic with low resistance in clinical diagnosis. [Display omitted] • Multifunctional AIEgens sensor bearing quaternary ammonium cationic based on the artificial nucleoside. • A 10-fold fluorescence enhancement in response to trace Hg2+ ions. • Reversible recognition of metal ions and biothiols. • Cell imaging and antibacterial. [ABSTRACT FROM AUTHOR]

Thyroid cancer has been increasingly prevalent in recent years. The main diagnostic methods for thyroid are B-ultrasound scan, serum detection and puncture detection. However, these methods are invasive and complex. It is a pressing need to develop non-invasive or minimally invasive methods for thyroid cancer diagnosis. Fluorescence method as a non-invasive detection method has attracted much attention. Butyrylcholinesterase (BChE) is a common enzyme in the human body, and many diseases affect its reduction. We found that BChE is also a marker for thyroid cancer. Therefore, it is of certain clinical value to explore the expression of BChE in thyroid cancer cells through a customized fluorescent probe to provide valuable experimental data and clues for studying the expression of thyroid cancer marker to reflect thyroid status. In this study, we customized a fluorescent probe named Kang-BChE, which is easy to synthesize with a high yield. The experimental results show that the probe Kang-BChE can detect BChE in the linear range of 0–900 U L−1 (R2 = 0.9963), and the detection limit is as low as 3.93 U L−1 (λ ex/em = 550/689 nm). In addition, Kang-BChE probes have low cytotoxicity, good specificity, and can completely eliminate interference from acetylcholinesterase (AChE). Kang-BChE showed excellent stability in the detection of complex biological samples in serum recovery experiments (95.64–103.12 %). This study was the first time using Kang-BChE to study the low expression of BChE in thyroid cancer cells (Tpc-1 cells). In addition, we observed that H 2 O 2 concentration in Tpc-1 cells was positively correlated with BChE activity. Kang-BChE is expected to be an important tool for monitoring the change of BChE content in complex biological environments due to its excellent performance. Kang-BChE can also be used to explore the influence of molecules in more organisms on the change of BChE content due to its excellent anti-interference ability. We expect that Kang-BChE can play a significant role in the clinical diagnosis and treatment of thyroid cancer. [Display omitted] • Kang-BChE was first to observe the change of BChE content in Tpc-1 cells. • Kang-BChE can completely eliminate the interference of AChE. • Kang-BChE has good stability in complex biological samples. • Kang-BChE observed positive correlation between H 2 O 2 and BChE in Tpc-1 cells. [ABSTRACT FROM AUTHOR]

β -Glucosidase (β -Gluco) is an enzyme that is crucial to numerous diseases, including cancer, and in sector of industries, it is used in the manufacturing of food. Measuring its enzymatic activity is critical for biomedical studies and other activities. Herein, we have developed a novel and precise fluorescent sensing method for measuring β -Gluco activity based on the production of yellow-green fluorescent quercetin-silicon nanoparticles (Q-SiNPs) produced from quercetin (QN) as a reducing agent and 3-[2-(2-aminoethyl amino) ethylamino] propyl-trimethoxy silane (AEEA) as a silane molecule. β -Gluco hydrolyzed quercetin-3-O- β - d -glucopyranoside (QO- β -DG) to produce QN, which was then used to produce Q-SiNPs. Reaction parameters, including temperature, time, buffer, pH, and probe concentration, were carefully tuned in this study. Subsequently, the fluorescence intensity was performed, showing good linearity (R2 = 0.989), a broad linear dynamic range between 0.5 and 12 U L−1, and a limit of detection (LOD) as low as 0.428 U L−1, which was proven by fluorescence measurements. Most importantly, various parameters were detected and characterized with or without β -Gluco. The designed probe was successively used to assess β -Gluco activity in human serum and moldy bread. However, the mathematical findings revealed recoveries for human serum ranging from 99.3 to 101.66% and for moldy bread from 100.11 to 102.5%. Additionally, Q-SiNPs were well suited to being incubated in vitro with L929 and SiHa living cells, and after using an Olympus microscope, imaging showed good fluorescence cell images, and their viability evinced minimal cytotoxicity of 77% for L929 and 88% for SiHa. The developed fluorescence biosensor showed promise for general use in diagnostic tests. Therefore, due to this outstanding sensing modality, we anticipate that this research can provide a novel schematic project for creating simple nanostructures with a suitable plan and a green synthetic option for enzyme activity and cell imaging. [Display omitted] • Q-SiNPs were generated through the combination of quercetin and 3-[2-(2-aminoethyl amino) ethylamino] propyl-trimethoxy silane. • β-Glucosidase hydrolyze quercetin-3-O-β- d -glucopyranoside to generate quercetin. • Castanospermine had been used as β-Glucosidase inhibitor with a significant effect. • β-Glucosidase activity analytically produced from human blood and samples of moldy bread with successful recoveries. • Q-SiNPs were suited for imaging L929 and SiHa cells due to their minimal cytotoxicity. [ABSTRACT FROM AUTHOR]

Monoaromatic molecules are a category of molecules containing a single aromatic ring which generally emit light in the ultraviolet (UV) region. Despite their facile preparation, the UV emission greatly limits their application as organic probes. In this study, we developed a general method to red shift the emission of monoaromatic molecules. Significant fluorescence red-shift (∼100 nm per intramolecular hydrogen bonding) can be achieved by introducing intramolecular hydrogen bonding units to benzene, a typical monoaromatic molecule. Upon increasing the number of hydrogen bonding units on the benzene ring, UV, blue, and green emissions are screened, which are switchable by simply breaking/restoration the intramolecular hydrogen bonding. As a demonstration, with the breaking of one intramolecular H-bonding, the green emission (λ em max = 533 nm) of 2,5-dihydroxyterephthalic acid (DHTA) changed to cyan (λ em max = 463 nm) upon the formation of its phosphorylated form (denoted as PDHTA), which, in the presence of alkaline phosphatase (ALP), hydrolyzed and recovered the green emission. By taking advantage of the switchable emission colors, ratiometric in vitro and endogenous ALP sensing was achieved. This general approach offers a great promise to develop organic probes with tunable emissions for fluorescence analysis and imaging by different intramolecular hydrogen bonding. Image 1 • Intramolecular hydrogen bonding-induced large red emission-shift of monoaromatics was presented. • Ratiometric fluorescence variation of monoaromatics by altering intramolecular hydrogen bonding was realized. • A sensitive and selective ratiometric fluorescence probe for evaluating alkaline phosphatase activity was proposed. • The visualization of endogenous alkaline phosphatase was achieved. [ABSTRACT FROM AUTHOR]

Taking advantage of the superior biocompatibility, good stability in a wide pH and temperature range, as well as its strong affinity with DNA of hydroxyapatite (HAp), tetrahedral DNA nanostructures (TDNs) conjugated with AS1411 aptamer (anti -nucleolin overexpressed on tumor cell membranes) were employed as affinity ligands to construct a novel mono-dispersed HAp based probe with Gd3+ doping (Apt-TDNs-GdHAp) for MR imaging. The adsorption of TDNs on the nano-HAp surface facilely accomplished the construction of the Apt-TDNs-GdHAp probes. Meanwhile, the use of hydrophilic TDNs not only favored the phase-transfer from the oil phase to the aqueous phase, but also enhanced the mono-dispersion of this probe due to the well-ordered distribution of TDNs on the surface of nano-HAp. Moreover, Apt-TDNs-GdHAp probe with a better mono-dispersion and crystalinity achieved twice higher longitudinal relaxivity (r 1 value) than that of GdHAp synthesized by microwave-assisted method (Microwave-GdHAp), exhibiting much more excellent T 1 -weighted imaging performance. With the introduction of TDNs, the stability and the tumor-targeting accessibility were also greatly improved, showing its great potential for further bio-applications. A novel mono-dispersed Gd3+-doped HAp based MRI probe modified by TDNs with AS1411 conjugation was facilely fabricated for tumor-cell imaging, exhibiting much more excellent T 1 -weighted imaging performance than that of Microwave-GdHAp. Image 1 • A nano-hydroxyapatite based MRI probe was facilely fabricated. • The good mono-dispersion is favorable for its MRI contrast performance. • The probe showed excellent mono-dispersion, stability and tumor-targeting performance. [ABSTRACT FROM AUTHOR]

A deep-red emission and lipid droplets-targeted fluorescence probe (named ZFPy) for effective bioimaging of bisulfite was developed from flavone moiety and benzoindole derivative based on intramolecular charge transfer (ICT) and Förster resonance energy transfer (FRET) platform. ZFPy displayed promising fluorescence parameters including bright deep red fluorescence (615 nm), large Stokes shift (205 nm), extended emission window gap (140 nm), high absolute fluorescence quantum yield (4.1%) and stable emission signal output. In addition, ZFPy realized ratiometric fluorescence monitoring for SO 2 derivatives with low detection limit (30 nM), preferable linearity, high sensitivity and selectivity. Interestingly, dual fluorophores (i.e. the donor moiety and 1,1,2,3-tetra-substituent-1H-benzo[e]indol-3-ium iodide moiety) released the same emission band about 475 nm to enhance the emission signal when ZFPy reacted with SO 2 derivatives, to the best of our knowledge, this is the first synergetic FRET/ICT platform for fluorescence probe, which might effectively offer ZFPy a high sensitivity and low detection limit in the detection of SO 2 derivatives. More importantly, ZFPy could image exogenous and endogenous SO 2 derivatives in living HeLa, HepG2 and L-O2 cells with good biocompatibility and photostability. ZFPy also preferred to load on lipid droplets with high Pearson's coefficient (0.95). Image 1 • A ratiometric fluorescent probe (ZFPy) for rapidly monitoring SO 2 derivatives was developed. • FRET-based ZFPy displayed larger gap (140 nm) between two emission spectra. • This is a first synergetic FRET/ICT platform for fluorescence probe. • ZFPy was applied to image exogenous and endogenous SO 2 derivatives in living Hela, HepG2 and L-O2 cells. • ZFPy showed lipid droplets-targeted ability (Pearson's coefficient 0.95). [ABSTRACT FROM AUTHOR]

Nucleases play crucial roles in maintaining genomic integrity. Visualization of intracellular distribution and translocation of nucleases are of great importance for understanding the in-vivo physiological functions of these enzymes and their roles in DNA repair and other cellular signaling pathways. Here we review the recently developed approaches for fluorescence imaging of nucleases in various eukaryotic cells. We mainly focused on the immunofluorescence techniques, the genetically encoded fluorescent probes and the chemically synthesized fluorescent DNA-substrate probes that enabled in-situ visualization of the subcellular localization of nucleases and their interactions with other protein/DNA molecules within cells. The targeted nucleases included important endonucleases, 3′ exonucleases and 5′ exonucleases that were involved in the DNA damage repair pathways and the intracellular DNA degradation. The advantages and limitations of the available tools were summarized and discussed. Image 1 • The principle of different fluorescent probes for tracking intracellular nucleases. • The advantages and limitations of available methodology for cellular DNA delivery. • Visualization of intracellular distribution and translocation of various nucleases. • Monitoring of the interactions between nucleases and other proteins within cells. [ABSTRACT FROM AUTHOR]

A water-soluble probe with p-hydroxybenzyl quaternary ammonium linker, FR-2a, for selective imaging in senescent cells is reported. Probe FR-2a integrated water-soluble fluorophore (HT-4a) and β-galactosidase (β-gal) trigger into one entity by a p-hydroxybenzyl quaternary ammonium linker. HT-4a is a styryl-based push–pull benzothiazole fluorophore with attractive properties, including excellent water-solubility, intense fluorescence emission and a large Stokes shift (161 nm), characterized by an intramolecular charge transfer (ICT) excited state. The formation of quaternary ammonium deactivated the ICT state, resulting in fluorescence quenching of FR-2a. In the presence of β-gal, the glycosidic bond was hydrolyzed and fluorophore HT-4a was released through self-immolative process, resulting in effective fluorescence recovery. FR-2a shows high affinity to β-gal (K m = 1.33 μM), exhibiting good sensitivity, selectivity and stability for imaging in senescent cells. Image 1 • Fluorescent probe FR-2a with self-immolative p-hydroxybenzyl quaternary ammonium linker was developed. • FR-2a selectively and rapidly responses to β-gal in PBS buffer. • FR-2a has excellent water solubility, avoiding ACQ of fluorescence in PBS. • FR-2a was capable of selective imaging in senescent cells. [ABSTRACT FROM AUTHOR]

Neutrophil elastase (NE), a representative protease which is closely related to many diseases, acts an indispensable role in inflammatory diseases and clinical medicine. In this work, one activity-based non-peptide ratiometric fluorescent probe DCDF was designed with pentafluoropropionic anhydride as identification group. To our knowledge, this is the first probe capable of detecting NE in ratio. After the addition of the NE, the emission spectrum of DCDF has obvious bathochromic-shift phenomenon, and there is large Stokes shifts of ∼60 nm. Compared to only a few reported NE probes, DCDF is sensitive and selective and has very low detection limit (0–14 μg/mL, DL = 30.8 ng/mL). A possible response mechanism was proposed and verified by HPLC and HRMS spectra. What's more, DCDF is capable of endogenous recognition imaging in biological cells without interference from other enzymes under the ratio signal. A549 and HeLa cells were used for endogenous cell imaging experiments of NE and the feasibility of DCDF for the specific detection of NE in cells was proved. This experimental result makes probe DCDF a very promising tool for the clinical diagnosis and treatment of NE related diseases. Two ratiometric probe DCDF was synthesized to detect NE with a ratio signal. Probe DCDF can respond to NE in a very short time, ideal detection limit (30.8 ng/mL) and good selectivity. Probe DCDF can use to detect endogenously produced NE in A549 and HeLa with a ratio signal. Image 1 • DCDF synthesized based on ICT mechanism and the first small molecule probes capable of detecting NE in ratio. • DCDF has obvious bathochromic-shift phenomenon, and has a large Stokes shift of ∼ 60 nm. • DCDF shows highly selectivity and sensitivity, the LOD, low cytotoxicity and good biocompatibility. • The mechanism of DCDF reacted with NE was proposed and verified by HPLC and HRMS spectra. • The DCDF was successfully used for cell imaging in A549 and HeLa cells. [ABSTRACT FROM AUTHOR]

A smart fluorescent probe DPAS-Cys has been rationally designed based on a typical AIEgen DPAS and an acrylate moiety. The probe DPAS-Cys not only can be used for the detection of cysteine (Cys) selectively with large Stokes shift (200 nm) and relatively low detection limit (2.4 μM), but also shows lipid droplets (LDs) targeting property. The response mechanism for Cys was carefully verified. Importantly, due to the aggregation-induced emission characteristic, the introduction of considerable percentage of traditional organic solvent is avoidable, which makes it suitable for bioimaging in physiological systems. In addition, the confocal fluorescence imaging demonstrates that DPAS-Cys is able to detect Cys in LDs of different cell lines with universality. Our study opens a new avenue to understand the importance of LDs in biosystem, for which the gap between the essential biothiol Cys and the energy storage organelle LDs was bridged for the first time. Image 1 • A smart fluorescent probe DPAS-Cys is developed for selective detection of cysteine. • DPAS-Cys shows aggregation-induced emission characteristic and large Stokes shift. • DPAS-Cys exhibits lipid droplets targeting property with universality. [ABSTRACT FROM AUTHOR]

Cysteine/cystine redox couple plays a vital role in maintaining the cellular redox state of living bio-systems. However, the dynamic changes of the intracellular cysteine/cystine pool mediated by cysteine/glutamate transporter (System X C −) in various cellular processes have remained incompletely understood. Here we established a series of strategies around fluorescent probe CP2 for effectively monitoring the intracellular cysteine level in living cells and in vivo zebrafish model, therefore for tracking dynamic changes of system X C −-mediated cysteine/cystine pool under ferroptosis. Living cell imaging and in vivo visualization both revealed that intracellular cysteine levels could be significantly reduced upon blocking system X C − activity and inducing ferroptotic cell death. This kind of blocking was potent against cisplatin-resistant A549R cancer cells, which might bring new potential for treating drug-resistant carcinoma through regulating system X C − and processes of ferroptosis. With further improvements in monitoring tools, understanding of system X C −-mediated cystine/cysteine pool and ferroptosis could certainly offer crucial information in more physiological or pathological processes. In this work, we established a series of strategies around fluorescent probe CP2 for effectively monitoring the intracellular cysteine level in living cells and zebrafish model, therefore for tracking dynamic changes of system X C −-mediated cysteine/cystine pool under ferroptosis. Living cell imaging and in vivo visualization both revealed that intracellular cysteine level could be significantly reduced upon treatment with system X C − inhibition and ferroptosis induction. This kind of blocking was potent against cisplatin-resistant A549R cancer cells, which might bring new potential for treating drug-resistant carcinoma through regulating system X C − and processes of ferroptosis. With monitoring tools further improved, further understanding of system X C −-mediated cystine/cysteine pool and ferroptosis could certainly offer crucial information in more physiological or pathological processes. Image 1 • New strategy for monitoring endogenous cysteine in cancer and dynamic changes of Cys/cystine pool in external stimulation. • Effectively monitoring intracellular cysteine in living cells and zebrafish thus tracking Cys/cystine changing. • The first report for imaging Cys/cystine pool dynamics during ferroptosis. • Revealing physiological or pathological role of the system XC--mediated Cys/cystine pool in ferroptosis> Providing possibility to circumvent drug resistance of cisplatin and identify inhibitors for ferroptosis-mediated therapy. [ABSTRACT FROM AUTHOR]

Hydrogen sulfide (H 2 S) is an important endogenous gasotransmitter and has been implicated with a variety of biological processes. The development of an efficient method for monitor H 2 S fluctuations in biological systems is of great significance to understand its roles in physiological and pathological conditions. In this work, two red-emitting fluorescent probes SNARF-SSPy and SNARF-SeSPy for H 2 S detection with turn-on fluorescence signals were reported. Interestingly, SNARF-SeSPy exhibited excellent anti-interference via dual selenium-sulfur exchange reaction even in the presence of high concentrations of thiols, whereas SNARF-SSPy did not sense H 2 S in the same condition. Additionally, in the present of H 2 S, SNARF-SeSPy showed a rapid response and excellent sensitivity with a detection limit of 34 nM. Most importantly, SNARF-SeSPy featured low cytotoxicity and could be employed to detect and image exogenous/endogenous H 2 S in living cells and zebrafish. Image 1 • Two red-emitting fluorescent probes SNARF-SSPy and SNARF-SeSPy have been designed for efficient detection of H 2 S. • By comparing the two probes, only SNARF-SeSPy exhibited excellent anti-interference even in the presence of high concentration of thiols. • Results of imaging H 2 S in living cells and zebrafish demonstrated that SNARF-SeSPy could be employed to track exogenous and endogenous H 2 S in vitro and in vivo. [ABSTRACT FROM AUTHOR]

In this work, a novel bright yellow fluorescent carbon dots (CDs) was synthesized from N-methyl-1,2-phenylenediamine hydrochloride in ethanol solvent through the solvothermal method. The obtained carbon dots had no fluorescence in water, but could specifically light up in the cell which makes the staining process without washing. Interestingly, the imaging process can be performed by simply shaking the culture with the cells for only 1 min, indicating ultrafast and easy to operate fluorescence imaging. Moreover, the carbon dots with abundant amino functional groups had good lysosome targeting properties (the Pearson's correlation coefficient is 0.92) and could achieve the ultrafast lysosome imaging in cell and zebrafish and monitoring cell apoptosis status. This is the first lysosome targeting carbon dots that allows the combination of a short incubation at the second-level with wash-free process providing great potential for continuous observation lysosome in vivo. The obtained carbon dots can not only accumulate in lysosome rapidly by the clathrin-mediated endocytosis and were used for wash-free in lysosome and zebrafish imaging, but also monitor the dynamic change of lysosomal apoptosis. Image 1 • The method has intrinsic lysosome targeting without further modification. • The carbon dots can accumulate in lysosomes within 1 min by the clathrin-mediated endocytosis. • The obtained carbon dots were used for wash-free lysosome imaging in living and fixed cells. • The carbon dots can monitor the dynamic change of lysosomal apoptosis. • The obtained carbon dots were also used for ultrafast and wash-free imaging in zebrafish. [ABSTRACT FROM AUTHOR]

Fluorescent organic dots (O-dots) recently have emerged as a new class of promising contrast reagents for two-photon fluorescence (TPF) imaging. However, most of these developed two-photon absorption (TPA) O-dots have no tumor-targeting group, which hampers their wide application for targeted tumor imaging. Herein, we fabricated Sgc8c aptamer-mediated TPA O-dots as a proof-of-concept of the sensing platform for targeted imaging in live cells or deep tissues. The O-dots composed of trans -4-[p-(N, N-diethylamino)styryl]-4'-(dimethyl amino) stilbene (DEAS) emerged as TPA organic emissive cores and encapsulation by using poly (methyl methacrylate-co-methacrylic acid) (PMMA-co-MAA) as polymeric encapsulating matrix to form DEAS/PMMA-co-MAA O-dots via a co-precipitation strategy. The obtained O-dots enabled an extremely high TPA absorption cross-section, bright two-photon fluorescence (excitation at 720 nm; emission at 412 nm and 434 nm), excellent cell-permeability and high penetration depth. Sgc8c aptamer, as a protein tyrosine kinase-7 (PTK7) receptor-targetable ligand, was further anchored on the surface of O-dots to obtain DEAS/PMMA-co-MAA@Sgc8c nanoprobes by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC)-mediated coupling reaction. Guided by Sgc8c aptamer, DEAS/PMMA-co-MAA@Sgc8c nanoprobes could be rapidly internalized into target acute lymphoblastic leukemia cells (CEM) cells with high specificity and great efficiency. It was also performed that two-photon images of TPA nanoprobes exhibited high two-photon brightness not only in target CEM cells, but also in mouse liver tissue slices even a depth of up to 210 μm. In our perception, it is highly promising that this nanoprobe provides a valuable tool for in vivo targeted imaging. Image 1 • A versatile and scalable strategy to aptamer-modified two-photon DEAS/PMMA-co-MAA O-dots for targeted imaging was proposed. • The DEAS/PMMA-co-MAA O-dots enabled higher two-photon brightness (45-fold enhancement). • Sgc8c acts as a tumor-specific ligand is introduced to TP nanoprobes, applying for precision targeting and imaging in cells. • This novel targeted nanoprobes was capable of two-photon imaging up to 210 μm in liver tissue slices. [ABSTRACT FROM AUTHOR]

Analytical capabilities of Nanoscopic Secondary Ion Mass Spectrometry (nano-SIMS) and Synchrotron Radiation based X-ray Fluorescence (SR nano-XRF) techniques were compared for nanochemical imaging of polymorphonuclear human neutrophils (PMNs). PMNs were high pressure frozen (HPF), cryo-substituted, embedded in Spurr's resin and cut in thin sections (500 nm and 2 μm for both techniques resp.) Nano-SIMS enabled nanoscale mapping of isotopes of C, N, O, P and S, while SR based nano-XRF enabled trace level imaging of metals like Ca, Mn, Fe, Ni, Cu and Zn at a resolution of approx. 50 nm. The obtained elemental distributions were compared with those of whole, cryofrozen PMNs measured at the newly developed ID16A nano-imaging beamline at the European Synchrotron Radiation Facility (ESRF) in Grenoble, France. Similarities were observed for elements more tightly bound to the cell structure such as phosphorus and sulphur, while differences for mobile ions such as chlorine and potassium were more pronounced. Due to the observed elemental redistribution of mobile ions such as potassium and chlorine, elemental analysis of high pressure frozen (HPF), cryo-substituted and imbedded cells should be interpreted critically. Although decreasing analytical sensitivity occurs due to the presence of ice, analysis of cryofrozen cells - close to their native state - remains the golden standard. In general, we found nanoscale secondary ion mass spectrometry (nano-SIMS) and synchrotron radiation based nanoscopic X-ray fluorescence (SR nano-XRF) to be two supplementary alternatives for nanochemical imaging of single cells at the nanoscale. Image 1 • First Nano-SIMS imaging of thin sections of human polymorphonuclear neutrophils (PMNs) embedded in Spurr's resin. • Nano-SIMS and SR nano-XRF techniques are compared for nanochemical imaging of PMNs embedded in Spurr's resin. • Trace level metal imaging at 50 nm spatial resolution of cryofrozen PMNs using SR nano-XRF. • Comparison of SR nano-XRF imaging on 1) thin sections of PMNs embedded in Spurr's resin and 2) whole, cryofrozen PMNs. [ABSTRACT FROM AUTHOR]

An effective ratiometric fluorescent probe based on silicon particles/gold nanoclusters (SiNPs/AuNCs) nanohybrid has been fabricated and applied to be a "on-off-on" switch sensing platform for detection of Hg2+ and cysteine. In this elaborated sensing platform, the SiNPs just acted as internal reference signal, providing a build-in correction for background interferences and environmental effects, to which the AuNCs as a signal report unit for Hg2+ response was covalently grafted by amidation reaction. The fluorescence intensity of SiNPs/AuNCs could be effectively quenched upon adding Hg2+, accompanied with an easily distinguishable fluorescent color change. The ratiometric fluorescence signal (F 649 /F 511) of the established nanoprobe was linearly proportional to the concentration of Hg2+ ranging from 0.02 to 24 μM with a low detection limit of 5.6 nM, which is below the guideline value of Hg2+ in drinking water set by the World Health Organization. Interestingly, upon addition of cysteine, the Hg2+-quenched fluorescence intensity was recovered gradually. Furthermore, the approach developed has also been utilized for Hg2+ detection in real complex biological samples with satisfactory results. More importantly, benefiting from the good water-solubility and excellent biocompatibility, this nanoprobe can monitor the intracellular Hg2+ and cysteine in living cells, indicating its potential applications in advanced biosensing and bioimaging. Herein, we reported an effective dual-emission ratiometric probe for "on-off-on" detection of Hg2+ and cysteine. Image 1 • An efficient dual-emission fluorescent probe for simultaneously and visual detecting Hg2+ and L-Cys was constructed. • The probe could simultaneously detection of Hg2+ in human serum and urine samples. • Due to the ratiometric fluorescence model, the background interference was extincted. • The developed probe was successfully used for the fluorescence bioimaging of Hg2+ and L-Cys in live cells. [ABSTRACT FROM AUTHOR]

Dopamine β-hydroxylase (DBH) is involved in various neuronal transmission processes in the brain. Due to the severe diseases caused by abnormity levels of such important enzyme in human serum, sensitive and rapid detection of DBH at early stages is crucial, particularly for clinical analysis. Herein, we developed optical sensors for DBH that include the following: (i) a ratiometric fluorescence sensor that hybridizes the bovine serum albumin (BSA)-gold nanoclusters (BSA-AuNCs) and nitrogen doped carbon dots (N-CDs). The sensor proved to be highly selective and sensitive, achieving a linear range of 0.02–0.16 μg mL−1 and a limit of detection of 4.0 ng mL−1. In the presence of DBH, the fluorescence intensity of BSA-AuNCs (λ em = 615 nm) was remarkably quenched by DBH serving as a reporter signal, whereas the N-CDs fluorescence intensity at 440 nm was almost kept unchanged serving as a reference signal. The developed ratiometric sensor is capable of demonstrating a color change from pink to violet and blue with a gradual increase in DBH concentration, which is discernible by the naked-eye. A test strip is prepared for semi-quantitative assay and convenient use. Intriguingly, by taking advantage of the inter-AuNCs aggregation in the presence of DBH, (ii) a resonance light scattering (RLS) sensor was also developed based on the nanohybrid probe (detection limit 95 ng mL−1). Fluorescence imaging in PC12 cell lines demonstrated that the BSA-AuNCs could be utilized in visualization assay towards intracellular DBH. Additionally, the sensors were tested in a real matrix by spiking serum samples with satisfactory recoveries. Image 1 • Ratiometric fluorescence method for Dopamine β-hydroxylase was developed for the first time. • Dopamine β-hydroxylase assay was performed for the first time based on a nontoxic and simple method. • A resonance light scattering detection of Dopamine β-hydroxylase was developed. • A portable and visual test strip was developed for Dopamine β-hydroxylase as a point of care testing. • Cellular imaging of the BSA-AuNCs was achieved successfully on brain cells. [ABSTRACT FROM AUTHOR]

We report on the synthesis of manganese oxide doped CDs (MnO x -CDs) by a hydrothermal strategy using manganese (III) acetylacetonate (Mn(III) (C 5 H 7 O 2) 3) as the only raw materials. The MnO x -CDs exhibit water solubility, favorable biocompatibility, low cytotoxicity, and show blue fluorescence with excitation/emission maxima at 326/442 nm with a quantum yield of 11.3%, allowing efficient cellular imaging. The MnO x -CDs have a reversible temperature-sensitive fluorescent property in vitro within 10–60 °C, which can also be used as a sensitive thermometer in living cells. By a scratch assay, the MnO x -CDs can restrain the migration of HepG2 cancer cells, which make the MnO x -CDs be attractive candidates for liver cancer adjuvant treatment. Besides, the fluorescence of the MnO x -CDs is quenched in the presence of Fe3+ due to the formation of a nonfluorescent MnO x -CDs-Fe3+ complex between oxygen-containing groups on the surface of MnO x -CDs and Fe3+, and the quenched fluorescence of MnO x -CDs can be turn-on by dissociation of MnO x -CDs-Fe3+ complexes by biothiols including L -cysteine, homocysteine and glutathione. Therefore, the Fe3+ and biothiols can be sequentially detected with high reliability and accuracy via exploiting the on-off-on nanosensor at room temperature, respectively. Further application to detection biothiols in human serum indicated that the probe was practicality and feasibility in medical field. Image 1 • First synthesis of manganese oxide doped CDs (MnO x -CDs) using manganese (III) acetylacetonate as the single precursor. • The MnO x -CDs have reversible temperature-sensitive fluorescent behaviors in vitro and can be used as a thermometer in vivo. • The MnO x -CDs can restrain the migration of HepG2 cancer cells, which facilitate liver cancer adjuvant treatment. • Fe3+ and biothiols can be sequentially detected with high reliability and accuracy based on the MnO x -CDs. [ABSTRACT FROM AUTHOR]

With this research we presented a ratiometric and mitochondria-target fluorescent probe (Mito-HT) for detection of H 2 O 2 both in vitro and in live cells. Mito-HT was constructed by direct conjugation of aryl boronate to fluorophore with three synthetic steps. The borate group is cleaved from Mito-HT in the presence of H 2 O 2 , resulting in the exposure of the hydroxyl group of the electron donating group. Then the ICT mechanism was turned on, and the fluorescence emission of Mito-HT at 493 nm was red-shifted to 562 nm, thereby achieving radiometric detection of H 2 O 2. Mito-HT exhibited a highly selectivity towards H 2 O 2 , and this interaction can be completed within 40 min. Mito-HT could be used for quantitative detection of H 2 O 2 (0–200 μM) through ratiometric fluorescence signal readout. And limit of detection (LOD) is approximately 0.33 μM. The relatively high stability and medium fluorescence quantum yield of Mito-HT (0.39) and Mito-HT-OH (0.43) enable clear mitochondria localization and dual-channel fluorescence imaging of H 2 O 2 in live cells with confocal microscopy. Image 1 • A new ratiometric and mitochondria-target fluorescent probe (Mito-HT) was constructed. • Mito-HT exhibited a selective response towards H 2 O 2 through ratiometric fluorescence signal readout. • Mito-HT could be used for quantitative detection of H 2 O 2 (0–200 μM). • Mito-HT localized in mitochondria and allows a dual-channel imaging of H 2 O 2 in live cells. [ABSTRACT FROM AUTHOR]

Telomerase, as a potential biomarker for early cancer diagnostics and therapies, has attracted considerable interests concerning its detection and monitoring. Herein, we develop a novel method for sensitive detection of telomerase activity by designing a gold nanoparticles/graphene oxide (AuNPs/GO) probe. The AuNPs were functionalized with a telomerase substrate (TS) primer and a 6-carboxy-fluorescein (FAM)-modified complementary DNA (P1). In the absence of telomerase, P1 exists in the random-coiled conformation, and the fluorescence resonance energy transfer (FRET) from FAM to AuNPs and GO results in efficient fluorescence quenching. In the presence of telomerase, the multiple hybridization between TS extension products and P1 leads to the conformation transition of P1 from single-stranded DNA to double-stranded rigid structure, and thus the FRET process can be prevented with the efficient fluorescence recovery. The metal enhanced fluorescence (MEF) effect between FAM and AuNPs can further effectively enhance the fluorescence of FAM, and thus the sensitivity and specificity of telomerase detection can be remarkably improved. It is worth mentioning that the proposed strategy does not need to design complex hairpin structure and allows the measurement of telomerase activity in three crude cell extracts equivalent to 7 HeLa cells, 8 A549 cells and 8 L929 cells in 1 h. In addition, the present sensing platform can be applied to inhibitor screening, in situ telomerase imaging, and intracellular drug delivery. Image 1 • The metal enhanced fluorescence effect can be regulated to generate significant fluorescence enhancement. • Weak background fluorescence can be realized via efficient fluorescence resonance energy transfer. • Telomerase activity down to 7 HeLa cells can be sensitively detected. • The method facilitates cellular imaging, inhibitor screening and drug delivery. [ABSTRACT FROM AUTHOR]

A multiple turn-on fluorophore (FHCS), combining fluorescein, hydrazone, cyanuric chloride and salicylaldehyde chromone into a molecule, was identified and developed based on density functional theoretical calculation. It was expected that FHCS could express exclusive fluorescent signals and improved Stokes shifts when chelating Al3+ or Zn2+. After it was synthesized and characterized in detail, it was noted that FHCS could turn-on fluorescently discriminate trace Al3+ and Zn2+ under the optimized conditions, i.e., from no-fluorescence to strong blue fluorescence for Al3+ and to green fluorescence for Zn2+ with low detection limits of 5.37 × 10−8 M and 7.90 × 10−8 M respectively. Owing to its low toxicity, FHCS was successfully applied for quantitative determination of Al3+ and Zn2+ in natural aqueous samples and toxicity evaluation of Al3+ and Zn2+ in living cells and bio-tissues with excellent linear relationships. The action mechanisms for FHCS with Al3+ and Zn2+ were confirmed to form stable 5-member-co-6-member condensed rings between Al3+/Zn2+ and N/O atoms in FHCS by both theoretic and experimental methods, which resulted in turn-on fluorescence with different dipolar moments and improved Stokes shifts. A multiple turn-on fluorophore, combining fluorescein, hydrazone, cyanuric chloride and salicylaldehyde chromone into a molecule (FHCS), was identified and developed for turn-on fluorescently discriminate trace Al3+ and Zn2+ in natural aqueous, living cells and bio-tissue samples with quite low detection limits of 5.37 × 10−8 M and 7.90 × 10−8 M respectively. The action mechanisms for FHCS with Al3+ and Zn2+ were confirmed by both theoretic and experimental methods to form stable 5-member-co-6-member condensed rings between Al3+/Zn2+ and N/O atoms, which resulted in turn-on fluorescence with different dipolar moments and improved Stokes shift. Image 1 • A multiple turn-on fluorophore combining fluorescein, hydrazone, cyanuric chloride and salicylaldehyde chromone was developed. • It could turn-on fluorescently monitor Al3+ and Zn2+ in aqueous. • It was applied for cell imaging of Al3+ and Zn2+ in bio-samples. • The reaction mechanism was to form stable 5-member-co-6-member condensed rings with improved Stokes shift. [ABSTRACT FROM AUTHOR]

To explore how hypochlorous acid (HClO) affects human health, a highly sensitive, selective, and trace detection method for hypochlorite (ClO−) is crucial for determining its non-negligible function in both environment and living systems. Herein, a dicyanoisophorone-phenylboronic acid-based novel ratiometric near-infrared fluorescent probe (Probe 1) was designed for the rapid and specific detection of ClO− based on the intramolecular charge transfer (ICT) mechanism. Excess addition of HClO to the Probe 1 solution, 186-times ratio (I 652 / I 582) augment were gained. And this probe provided a colorimetric and ratiometric fluorescence response to ClO− with a high selectivity, a rapid response (within 30 s), and had an extremely low detection limit (15.7 nM). In addition, owing to the good sensing properties and low cytotoxicity of Probe 1 , it can be used to expediently visualize exogenous ClO− in HepG2 cells and endogenous ClO− in RAW264.7 macrophage cells. Furthermore, the probe was successfully used for the bioimaging of zebrafish with an acute inflammation. Thus, Probe 1 is a promising vehicle to identify the level of HClO in animals with associated diseases. A new ratiometric and colorimetric NIR fluorescent probe (Probe 1) for the specific detection of ClO− has been designed and synthesized on the basis of dicyanoisophorone-phenylboronic acid. And it was endowed with the following outstanding advantages: one-step synthesis, a long-wavelength emission, naked-eye assay, ratio fluorescent dual-channel detection, and feasibility in living cells and zebrafish. Image 1 • A new ratiometric dicyanoisophorone fluorescent Probe 1 was synthesized. • Probe 1 displays high selectivity and sensitivity to ClO− over other relevant ROS and common ions. • Probe 1 responses quickly to ClO− through distinct color change and ratiometric fluorescence variation. • Probe 1 has low cytotoxicity and is applicable for ClO− detection in living cells. • Probe 1 is successfully used for the detection of endogenous and exogenous ClO− in zebrafish. [ABSTRACT FROM AUTHOR]

Nanoscale metal-organic frameworks (NMOFs) have been widely employed in biological diagnosis and treatment system. In this work, glutathione stabilized gold nanoclusters (GSH-AuNCs) were successfully encapsulated in NMOFs and the as-obtained nanocomposites (named as AuNCs@NMOFs) showed nearly 10 times enhancement in fluorescence intensity and longer fluorescence lifetime relative to GSH-AuNCs. In addition, the fluorescence intensity of AuNCs@NMOFs was quenched by highly reactive oxygen species (hROS) due to their strong oxidation ability. Based on the fact, the nanocomposites were used for the detection of hROS with a linear range from 80 nM to 1.0 μM toward hypochlorite (as the representative of hROS). The limit of detection (LOD) was about 30 nM, which was about 30 times lower than that of GSH-AuNCs (LOD = 0.96 μM). With the features of good biocompatibility, excellent luminescence and efficient cellular uptake, AuNCs@NMOFs were successfully applied in fluorescence imaging of hROS in living cells. Au nanoclusters@NMOF nanocomposites were prepared and further applied for hROS detection with high sensitivity in living cells. Image 1 • Au nanoclusters@NMOF composites were prepared as nanoprobe for hROS through a facile in-situ growth method. • The nanoprobe was developed to detect hROS with a fast response time and nearly 30 times sensitive than AuNCs. • The nanoprobe had been successfully applied in the imaging of exogenous and endogenous hROS in living cells. [ABSTRACT FROM AUTHOR]

A fluorescent probe for the determination of nitrite (NO 2 −) was fabricated by using green fluorescent nitrogen doped carbon dots (NCDs). The NCDs were synthesized via a one-pot hydrothermal carbonization of citric acid in the presence of p -phenylenediamine as the nitrogen source. The N content of the NCDs was high to 17.09% and consisted of a variety of functional groups on the NCDs surface, including sp2-hybridized C N, porphyrin C–N–C and amino N in N-(C) 3 or H–N-(C) 2 et al. N atoms were also doped within the framework of the NCDs. The almost monodisperse NCDs (average particle diameter = 3.67 nm) exhibited green photoluminescence (PL) with excitation/emission maxima of 360/505 nm. The PL of the NCDs was dependent on both excitation wavelength and solution pH. The NCDs showed a strong PL quenching response to NO 2 − under acidic conditions (pH = 2.5). The PL intensity of the NCDs was inversely proportional to the concentration of NO 2 − between 0.02 and 40 μM (R2 = 0.992), with a detection limit of 21.2 nM. The practical use of the nanoprobe for NO 2 − determination in food samples was also demonstrated, successfully. NCD-nitroso compounds formed because of reaction between the abundant amide groups on the surface of NCDs with the NO 2 −, which caused an inner filter effect and static PL quenching. Importantly, the NCDs had low cellular toxicity and were successfully used as a multicolor cellular imaging agent for Hepg2 cells. One-pot hydrothermal synthesis of nitrogen doped carbon dots that emit green fluorescence and their applications for nitrite detection based on inner filter effect and static quenching and multicolor cellular imaging. Image 1 • Nitrogen doped carbon dots (NCDs) were prepared by hydrothermal treatment of citric acid and p -phenylenediamine. • The NCDs showed selective and sensitive nitrite determination property. • The NCDs were successfully used to detect the content of nitrite in food samples. • The NCDs possessed high efficiency for multicolor cellular imaging. [ABSTRACT FROM AUTHOR]

NAD(P)H: Quinone Oxidoreductase 1 (hNQO1) is a cytosolic flavin two-electron reductase involved in many physiological and pathological processes that is overexpressed in many cancers and recognized as a potential cancer biomarker. However, it is still challenging for highly sensitive and selective monitoring hNQO1 in living cells. Here, we developed a highly selective and ultrasensitive hemicyanine-based near-infrared (NIR) fluorescence probe (probe HCYSN) for the sensing of hNQO1 activity and discrimination of human cancer cells. The fluorescent sensing system with NIR emission is low phototoxic to normal cells but is highly selective and ultrasensitive to hNQO1 in a linear range from 0.03 μg/mL to 0.6 μg/mL with detection limit (LOD) of 4.9 ng/mL (0.49 mU/mL), which is better than most of other hNQO1 probes reported. In particular, the NIR fluorescent probe was successfully applied to distinguish various cancer cells through the different distribution of endogenous hNQO1. All the present results demonstrated that the probe HCYSN exhibited great potential for human hNQO1 assay and in vivo imaging for the early cancers diagnosis and pathological studies. Image 1 • A new hemicyanine-based near infrared fluorescence probe HCYSN was designed. • The probe exhibited low phototoxicity to normal cells due to its NIR emission. • The probe showed high selectivity and sensitivity for detecting hNQO1 with a LOD superior to that of other probes. • The sulfonic acid group of the probe greatly promoted the interaction between probe and enzyme. • The probe was successfully applied for the visual discrimination of human cancer cells. [ABSTRACT FROM AUTHOR]

Pyrene-phenylglycinol tangled ratiometric sensor (R)-1 was developed for the detection of Al3+ ion over other metal ions. Ratiometric behaviour of (R)-1 for Al3+ ion explained through monomer emission and excimer quenching leads to avoiding the π-π interactions of bis-pyrene rings. Pull-push to push-pull binding mechanism is successfully explained by DFT and sensing of Al3+-ions demonstrated in living cells. The LOD of (R)-1 for Al3+ downs to nanomolar concentrations which is lower than the allowed concentration of drinking water set by the (World Health Organization) WHO. Image 1 • Probe (R)-1 selectively detects Al3+-ion via ratiometric approach and detection limit upto nanomolar range. • Pull-push to push-pull binding mechanism is supported by fluorimetry and DFT studies. • Probe (R)-1 act as a reversible ratiometric sensor for Al3+ ion in the presence of EDTA. • Sensing behaviours (R)-1 to Al3+ ion successfully applied into living cell imaging studies. [ABSTRACT FROM AUTHOR]

Genetically encoded fluorescent biosensors are particularly promising sensors to examine biochemical processes in a complex cellular context. RNA mimics of GFP are RNA-fluorophore complexes that emit green fluorescence comparable in brightness to fluorescent proteins. The fluorophore is non-fluorescent until it binds with specific RNA. We designed and developed a dual activated fluorescent probe based on RNA mimics of GFP for the detection of an intracellular nitroreductase. Our probe only fluoresces in the presence of both the specific RNA and nitroreductase. Since we used RNA to tag cells, our probe only fluoresces when nitroreductase exists in such cells. Our detection system should benefit the study of cell biomarkers in heterogeneous cell populations. More importantly, the strategy of quenching the RNA/DFHBI complex by alkylation of the hydroxyl group in DFHBI opens new possibilities for developing various genetically encoded fluorescent biosensors based on RNA/DFHBI complexes. Image 1 • First example of a dual activated fluorescent probe based on RNA mimics of GFP for the detection of nitroreductase. • Cell imaging nitroreductase only in RNA aptamer expressing cells. • The universal strategy of quenching fluorescence of the RNA/DFHBI complex by alkylation of the hydroxyl group in the DFHBI. [ABSTRACT FROM AUTHOR]

Conjugated polymers for bioimaging and sensing chemical/biological reagents have received much attention owing to their outstanding photophysical properties. However, most conventional synthetic strategies result in aggregates of conjugated polymers with limited solubility in most common organic and aqueous solvents. Therefore, advancement in molecular design and synthetic pathways is required to tune the optical and solubility properties of the resulting conjugated polymers. Herein, a simple, general, and effective approach for the synthesis of water-soluble polypyrrole (PPy) is reported based on the chemical polymerization in the presence of a homologue series of dicarboxylic acids with different chain lengths as multifunctional dopant molecules, possessing two carboxylic acid groups which serve as both dopants and stabilizing agents. The role of dopant chain length on the emission properties of resulting water-soluble polymers has been investigated. Among the synthesized water-soluble polymers, succinic acid-stabilized polymer (PPy-Suc) showed the highest emission wavelength (λ em = 453 nm), high quantum yield (12.87), very good photostability and low cytotoxicity, suggesting its applicability in bioimaging and sensing applications. As a proof of concept, the PPy-Suc polymer was successfully utilized in cellular imaging. Moreover, a novel fluorescence iodide sensor with two linear ranges of 0.012–0.200 and 0.200–8.825 μM and a low detection limit of 9 nM was developed based on the prepared PPy-Suc polymer. The superior properties of the synthesized water-soluble polymers confirm the potential applicability of developed method as a general, facile and effective synthesis approach in preparation of water-soluble conjugated polymers with several potential applications. Image 1 • PPy structure was modified with introducing homologue series of dicarboxylic acids. • Dicarboxylic acids act as both dopants and stabilizers and prepared water-soluble conjugated polymers. • The synthesized polymer (PPy-Suc) was used for development of a sensitive and selective iodide ion fluorescence sensor. • The PPy-Suc polymer was successfully utilized in cellular imaging. [ABSTRACT FROM AUTHOR]

Since inorganic phosphate ion (PO 4 3−) plays very important roles in environment or living organisms, developing a selective and sensitive detection method for PO 4 3− is highly desired. Owing to the superior optical properties, graphene quantum dots (GQDs) have been developed as a promising emitting material in fluorescence analysis. Herein, we reported the first example of negatively charged molybdate-mediated nitrogen doped graphene quantum dots (Mo 7 O 24 6--mediated N-GQDs) as a fluorescence "off-on" probe for PO 4 3− via "anion ion-mediated" strategy. The N-GQDs was firstly modified with Mo 7 O 24 6− through a complex bonding system containing ionic and hydrogen bonds. The formation of N-GQDs/Mo 7 O 24 6− complex leaded to photoluminescence (PL) quenching of N-GQDs. In the presence of PO 4 3−, strong affinity between PO 4 3− and Mo 7 O 24 6− produced ammonium phosphomolybdate, which destroyed the pre-formed N-GQDs/Mo 7 O 24 6− structure and detached Mo 7 O 24 6− from N-GQDs surface. Thus, the PL of N-GQDS was in turn switched on. Under optimal conditions, this probe exhibited a good linear relationship between PL response and PO 4 3− concentration in the range from 7.0 to 30.0 μM with a limit of detection of 50 nM. Also this probe with high selectivity and sensitivity has been successfully used to sense PO 4 3− in natural water, biological fluid, and living cells. A negatively charged molybdate mediated nitrogen-doped graphene quantum dots (Mo 7 O 24 6--mediated N-GQDs) as a fluorescent off-on probe for PO 4 3− has been developed and successfully utilized in real samples and live cells imaging. Image 1 • A fluorescence "turn on" N-doped graphene quantum dots nanocomposite for inorganic phosphate ion. • The nanocomposite working in "anion ion-mediated" principle. • The probe exhibiting the excellent PO 4 3− detection performance in biological fluids and living cells. • Presenting the possible detection mechanism. [ABSTRACT FROM AUTHOR]

This study examined the efficiency of pH-dependent, fluorescent carbon dots for the sensing of hazardous anions in aqueous media and cell imaging. The nitrite anion, an important water-soluble element for environmental and biological systems, requires continuous monitoring because a high concentration can affect the systems severely. The as-synthesized carbon dots efficiently detected the nitrite anion in aqueous solution through a fluorescent 'Turn Off' phenomenon. The quenching mechanism was investigated through proper microscopic and spectroscopic studies. The limit of detection and linear detection range were 7.9 nM and 2.3μM-7.7 mM, respectively. The sensitivity was tested with different water samples. In a parallel experiment, the as-synthesized carbon dots were used as a cell-imaging probe for HeLa cells, highlighting their potential in different biological studies. Image 1 • Fluorescent nitrogen-doped carbon nanodots were synthesized using a facile green chemical pathway. • The as-synthesized carbon dots showed selective and sensitive nitrite ion detection. • The as-synthesized carbon dots exhibited high efficiency for cell imaging. [ABSTRACT FROM AUTHOR]

Characterization of carbonaceous nanomaterials (CNMs) exposure is a key step and of great importance towards a better understanding of their toxicity and underlying mechanisms. However, it has been bottlenecked for lack of valid methods capable of quantifying cell-associated CNMs. Here, we developed a new economical and convenient method based on sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) that could accumulate graphene oxide (GO) at the interface between the loading well and the gel. The sharp black band formed there can be digitalized and the intensity quantified, which was proportional to the amount of GO loaded onto the gel. The method has a detection limit of 84.1 ng. We showed that the amount of GO in three different cell models, mouse macrophage cells (Raw264.7), human epithelial cells (A549) and mouse mesenchymal stem cells (MSC), could be accurately quantified by this assay, with the uptake rates decreasing in the order of MSC > Raw264.7 > A549. The results were consistent with the fluorescent imaging on cells exposed to fluorescence-labeled GO and TEM examination on ultrathin cell sections. The surprisingly highest uptake rate of MSC might be due to their abundant intracellular vesicles, which deserves further investigation. The novel method provides a complementary quantitative tool to the use of radioactive markers and fluorescent labeling of carbon nanomaterials and may facilitate the toxicological studies on carbon nanomaterials. Image 1 • Gel-electrophoresis based method was developed for accurate quantification of GO in cell samples. • The method has a LOD of 84.1 ng and is applicable in various types of cells. • MSC has the highest uptake rate of GO among three tested cells. • The method can be further extended to other carbon nanomaterials. [ABSTRACT FROM AUTHOR]

Hypochlorous acid (HOCl)/hypochlorite (OCl−), important reactive oxygen species, play essential roles in many physiological and pathological progresses. Accordingly, we developed a novel dicyanomethylene-4 H -pyran (DCM)-based probe DCM-OCl for colorimetric and near-infrared fluorescent turn-on detection of OCl−. The probe exhibited excellent selectivity and sensitivity for OCl− over other bio-related analytes with a detection limit of 80 nM. The excellent selectivity of DCM-OCl for OCl− was ascribed to specific oxidative cleavage of the dimethylthiocarbamate (DMTC) recognition unit by OCl−. Moreover, DCM-OCl exhibited an ultrafast turn-on response (<3 s) to OCl−, potentially allowing real-time detection of OCl−. Furthermore, DCM-OCl was successfully used to image endogenous/exogenous OCl− in living cells. Image 1 • A new near-infrared fluorescent turn-on and colorimetric probe for OCl-was developed. • Rapid (<3 s) and selective detection of OCl-was realized with good sensitivity. • The response mechanism was based on oxidative cleavage of the probe by OCl-. • Successful monitoring of endogenous/exogenous OCl-in living cells was achieved. [ABSTRACT FROM AUTHOR]

A novel imidazo[1,2-a]pyridine-rhodamine ratiometric fluorescent probe IP-Hg for Hg2+ based on a fluorescence resonance energy transfer mechanism has been developed. The probe has been proved to show high sensitivity and high selectivity toward Hg2+. Furthermore, it could be used for imaging Hg2+ in cells and in polluted water. Image 1 • A ratiometric fluorescent probe for sensing Hg2+ based on new imidazo[1,2-a]pyridine fluorophore has been synthesized. • The probe exhibits highly sensitivity and selectivity toward Hg2+ (LOD: 9.1 nM). • The ratiometric fluorescent probe displays a remarkable emission shift (220 nm). • The probe show low cytotoxicity and can image in cells. [ABSTRACT FROM AUTHOR]

Abnormal levels of Cys, Hcy and GSH are associated with various diseases, thus monitoring biothiols is of great significance. In this work, a dual-emission responsive near-infrared fluorescent probe NIR-NBD for detecting Hcy and Cys/GSH was developed based on the conjugation of a dicyanoisophorone based fluorophore (NIR-OH) and 7-nitrobenzofurazan (NBD). To our surprise, the addition of Hcy induced significant fluorescence enhancement at both 549 and 697 nm; while Cys/GSH resulted in major fluorescence emission at 697 nm. The detection limit was determined to be 33.2 nM for Cys, 33.5 nM for Hcy, and 34.4 nM for GSH. Therefore, the probe can be used for discriminative detection of Hcy and Cys/GSH. Moreover, fluorescence imaging of HeLa cells indicated that the probe was cell membrane permeable and could be used for visualizing Hcy and Cys/GSH in living cells. Image 1 • A novel NIR fluorescent probe for discriminative sensing of Hcy and Cys/GSH in dual channel was developed. • The probe can measure Hcy level in serum samples. • The probe could sense intracellular Hcy and Cys/GSH in living HeLa cells. [ABSTRACT FROM AUTHOR]

Abstract A new highly selective and sensitive dual-mode sensor 3TD based on the conjugate of oligothiophene and barbituric acid moiety was developed for colorimetric and turn-on fluorescent detection of CN─. The sensor 3TD exhibited high specificity towards CN─ by interrupting its own ICT producing thereupon a large blue-shift in UV–Vis spectrum and remarkable "turn-on" fluorescence emission. The detection limit was 2.26 × 10─7 M, which is quite lower than the permissible level of CN─ in drinking water according to the WHO. The fluorescent detection of CN─ was well demonstrated by filter paper strips and silica coated TLC plates. Moreover, the sensor was also used to detect CN─ in environmental water and agro-products with satisfactory results. Most importantly, in terms of these advantages of colorimetric and turn-on fluorescent dual-mode, immediate response, excellent selectivity, high sensitivity, low cytotoxicity, and good biocompatibility, the sensor 3TD was successfully applied into CN− imaging in living cells, demonstrating its excellent value in practical application. Graphical abstract Image 1 Highlights • A new colorimetric naked-eye and turn-on fluorescent sensor 3TD was developed. • Sensor 3TD emerged strong response to CN− with rapid, selective, and sensitive characteristics. • Sensor 3TD could detect trace CN− in water, agro-products and test strips. • Sensor 3TD showed low cytotoxicity and was successfully applied to living cell imaging. [ABSTRACT FROM AUTHOR]

Lipid droplets (LDs) are an important organelle as the main energy storage site in cells. LDs viscosity controls the material and energy exchange between it and other organelles. Furthermore, the LDs metabolic abnormalities, cell dysfunction, some diseases may be attributed to the singular LDs viscosity. Currently, the fluorescent probes for sensing the variations of LDs viscosity are still scarce and expose some drawbacks of low fluorescence quantum yield, low sensitivity and LDs polarity interference. Thus, the development of high performance probes is significant to detect LDs viscosity. We hereby provide a lipophilic fluorescent probe (TPE-BET) with high fluorescence quantum yield (Φ f , 0.91 in glycerol) for imaging LDs viscosity in living cells. With the increase of viscosity from 0.54 cp to 934 cp, the fluorescence at λ ex /λ em = 405/520 nm and the fluorescence quantum yield of TPE-BET linearly increased by 64.9 and 128.5 folds, respectively. Meanwhile, the outstanding LDs staining capability of TPE-BET may provide a high spatial resolution for LDs imaging. The cell imaging of TPE-BET not only successfully observed the viscosity variations of LDs in cell stress models, e.g., ferroptosis, inflammation and mitophagy, but also revealed the increased viscosity and extracellular delivery of LDs in heavy metal cell injury models (Hg/As) for the first time, which may supply concrete evidence for understanding the structure and function of LDs. This represents a new fluorescent probe TPE-BET with high fluorescence quantum yield for imaging LDs viscosity, which may decrease the dose of probe and excitation light intensity along with the improvement on signal noise ratio (S/N). The imaging results of TPE-BET clarified that LDs viscosity may be an appraisal index on cell differentiation, state evaluation and drug screening. [Display omitted] • A lipophilic probe (TPE-BET) with high fluorescence quantum yield was developed for imaging lipid droplet (LDs) viscosity. • TPE-BET shows high spatial resolution, which provide information including the distribution, size and morphology of LDs. • The LDs viscosity was detected in various cell models such as ferroptosis, mitophagy and heavy metal cell injury models. • LDs viscosity may be an appraisal index on cell differentiation, state evaluation and drug screening. [ABSTRACT FROM AUTHOR]

Ferroptosis is a novel Fe(II)-mediated oxidative cell death form, and is closely related with endoplasmic reticulum (ER). Exploring the fluctuation of ER polarity during ferroptosis is highly important for the in-depth study of the biological roles of ER in ferroptosis. Herein, we present a ratiometric probe (BNS) for revealing the changes of the ER polarity in the living cells experiencing ferroptosis. BNS employed a D-π-A-π-D type structure as the polarity-sensitive fluorophore, and selected p -toluenesulfonamide as the ER-targeting unit. Theoretical calculations suggested that the response mechanism of BNS to polarity was based on ICT, and two ICT processes appeared when BNS was at excited state. Cell imaging results demonstrated that BNS possessed desirable ER-targeting capability, and erastin-induced ferroptosis could increase the ER polarity of the living cells. Moreover, similarly to vitamin E (VE) and deferoxamine (DFO), dihydrolipoic acid (DHLA) could inhibit the changes of the ER polarity during erastin-induced ferroptosis. We expect that the probe could provide a convenient method to rapidly monitor ferroptosis and design novel drugs for the treatment of ferroptosis-relevant diseases. [Display omitted] • A D-π-A-π-D type structure-based fluorescent probe (BNS) was developed for detecting the changes of ER polarity in the living cells. • Two ICT processes appeared when the probe BNS responded to polarity. • Ratiometric fluorescence imaging demonstrated that ferroptosis could increase ER polarity in living cells. • Fluorescence imaging demonstrated that dihydrolipoic acid (DHLA) could show prominent inhibition effect to ferroptosis. [ABSTRACT FROM AUTHOR]

The widespread use of cyanide (CN−) in industry results in contamination of various effluents such as drain, lake, and tap water, an imminent danger to the environment and human health. We prepared naphthoquinolinedione (cyclized; 1 – 5) and anthracenedione (un-cyclized) probes (6 – 7) for selective detection of CN−. The addition of CN− to the probe solutions (1 – 5) resulted in a color change from pale green to orange under 365 nm illumination. The nucleophilic addition of CN− to C2 of the imidazolium ring of the probes is responsible for selective CN− detection. Among all probes, 1 gave the lowest fluorescence-based LOD of 0.13 pM. In contrast, the un-cyclized probes (6 and 7) were substantially inferior to the cyclized counterparts (1 and 2 , respectively) for detecting a trace amount of CN−. The notably low LOD displayed by probe 1 was maintained in the detection of CN− in real food samples, human fluids, and human brain cells. This is the first report studying imidazolium-bearing naphthoquinolinedione-based probes for CN− sensing in 100% water. Water-soluble probe 1 displayed a selective CN− sensing in water, along with a very low LOD of 0.13 pM and the probe was successfully applied for CN− sensing in human bio-fluids and food items. [Display omitted] • Several probes 1 – 7 were prepared in a single step. • Probe 1 showed a selective color change upon addition of CN−. • Formation of [probe 1 -CN−] adduct is responsible for fluorescence response. • Probe 1 displayed an effective detection of CN− in food samples and human bio-fluids. • A concentration of CN− as low as 1 μM was detected in human brain cells using probe 1. [ABSTRACT FROM AUTHOR]

Abstract MicroRNA (miRNA) plays significant roles in cell proliferation, differentiation and apoptosis, and has been considered to be valuable biomarker for cancer. Accurate and sensitive detection of miRNA is crucially significant for cancer diagnosis and treatment. Here, a MnO 2 nanosheet-mediated ratiometric fluorescence biosensor was designed for miRNA detection and imaging in living cells. It contained MnO 2 nanosheets acting as DNA carrier, and fluorescent donor (FAM)-labeled hairpin H1 (recognition probe) and fluorescent acceptor (TAMRA)-labeled hairpin H2 (amplification probe). When the biosensor entered cell by endocytosis, MnO 2 nanosheets were degraded to Mn2+ via intracellular glutathione (GSH) and the adsorbed hairpins H1 and H2 were released. The intracellular target miRNA-21 hybridized with the recognition unit of H1 to initiate catalyzed hairpin assembly (CHA) and a large amount of H1-H2 duplexes were produced. This brought fluorescent donor FAM and fluorescent acceptor TAMRA into close proximity to produce fluorescence resonance energy transfer (FRET), inducing a ratiometric fluorescent response (donor signal decreased and acceptor signal enhanced) for miRNA-21 detection. Furthermore, this method could be applied to differentiate the expression levels of miRNA-21 in HeLa, HepG-2 and L02 cells. These results indicated that the proposed method possessed great potential in the early diagnosis of miRNA-related diseases. Graphical abstract Image 1 Highlights • A ratiometric fluorescence biosensor was designed for miRNA detection. • The strategy had been applied to differentiate miRNA expression levels in cells. • The CHA displayed signal amplification ability, ensuring the sensitive detection. • The strategy held great potential for the early clinical diagnostics. [ABSTRACT FROM AUTHOR]

Abstract Characterizing cell behavior is important to modern medical diagnoses as the changes of cell behavior are often indicators of huge diseases. In order to gain enough information about cells, developing novel methods of cell sorting and imaging is an important task. With development of micro-fabrication technologies, more advanced miniaturized devices are applied to cell research. Here, a portable and easy-to-use chip with high-density periodic micro-well array is designed and fabricated to capture target cells specifically. Combining with aptamer-silver conjugates and FAM functioned report probes, the sandwich assay was successfully applied for imaging cells. Any well of the chip is carefully designed to provide abundant information on single cells. Since there are 19,200 microwells in a single chip, more information is available. Compared to other cells, such as HEK-293, MCF-7, U 2 OS and Ramos cells, the sandwich assay shows high specificity towards target cell CCRF-CEM. What's more, the applications of the chip can be further expanded to other cells imaging if suitable aptamers were selected. This high-density micro-well array of aptamer-silver conjugates is hopeful to play an important role in medical diagnosis in the future. Graphical abstract Image 1 Highlights • The aptamer-silver conjugates can effectively capture cells and amplify signal. • The well-designed chip eliminates the non-specific adsorption and enhance specificity. • Different cells can be detected simultaneously if different aptamers were applied. • The captured cells can be easily localized and analyzed at the same time. [ABSTRACT FROM AUTHOR]