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Heavy metal contamination has become a global environmental problem and currently drawn much attention from researchers in worldwide. High exposure to heavy metals can lead to problems like kidney, liver and brain damage, skin and lung cancer, etc. Rapid and sensitive detection of heavy metals is of immense importance in environmental monitoring. Over the past few decades, enormous efforts have been made to design various sensors to identify and monitor these harmful metal ions. In Comparison with other methods, fluorescence‐based chemosensors have received extensive attention because of the advantages of high sensitivity, low cost, real‐time monitoring, simple operation, etc. The pyrene derivatives are significant polycyclic aromatic hydrocarbons (PAHs) with strong fluorescence. They are widely used as fluorescent probes in many applications due to their easy modification, high fluorescence quantum yield, and strong fluorescence emission in live cells, outstanding cell permeability, and very low cytotoxicity. The SDG 6: Clean water and sanitation alarm a strong strategy, and careful identification of the risk connected to environmental pollutants needs urgent attention in this situation. Therefore, we highlight different types of pyrene‐based fluorophores and the fluorescence mechanisms for the sensitive and selective detection methodology of Arsenic, Mercury, Cadmium, Lead, and Chromium heavy metals. [ABSTRACT FROM AUTHOR]

• The review explores the world of functional chromophores synthesized via MCRs. • MCR-synthesized functional chromophores are reshaping imaging research. • Bioimaging probes synthesized by MCRs with tunable properties. This review aims to provide a comprehensive overview of recent advancements and applications of fluorescence imaging probes synthesized via MCRs (multicomponent reactions). These probes, also known as functional chromophores, belong to a currently investigated class of fluorophores that are presently being successfully applied in bioimaging experiments, especially in various living cell lineages. We describe some of the MCRs that have been employed in the synthesis of these probes and explore their applications in biological imaging, with an emphasis on cellular imaging. The review also discusses the challenges and future perspectives in the field, particularly considering the potential impact of MCR-based fluorescence imaging probes on advancing this field of research in the coming years. Considering that this area of research is relatively new and nearly a decade has passed since the first publication, this review also provides a historical perspective on this class of fluorophores, highlighting the pioneering works published between 2011 and 2016. [ABSTRACT FROM AUTHOR]

A series of dithienothiophene S,S-dioxide (DTTDO) dyes was designed, synthesized, and investigated for their suitability in fluorescent cell imaging. Synthetized (D-π-A-π-D)-type DTTDO derivatives have molecule lengths close to the thickness of the phospholipid membrane, and they contain on both ends two positively charged or neutral polar groups to increase their solubility in water and to ensure simultaneous interaction with polar groups of the inner and outer part of the cellular membrane. DTTDO derivatives exhibit absorbance and emission maxima in the 517–538 nm and 622–694 nm range, respectively, and a large Stokes shift up to 174 nm. Fluorescence microscopy experiments revealed that these compounds selectively intercalate into cell membranes. Moreover, a cytotoxicity assay conducted on a model human live cells indicates low toxicity of these compounds at the concentrations required for effective staining. With suitable optical properties, low cytotoxicity, and high selectivity against cellular structures, DTTDO derivatives are proven to be attractive dyes for fluorescence-based bioimaging. [ABSTRACT FROM AUTHOR]

AIE-active compounds have lately attracted considerable attention owing to their versatile applications, especially in OLED and bioimaging. Herein, a series of coumarin-3-formylhydrazone derivatives (CFH-1, 2, 3 and 4) were developed for investigating their AIE and solid-state luminescence behaviors. All the obtained compounds emit varying degrees of solid-state fluorescence. CFH-1 and 2 show the typical AIE characteristics, while CFH-3 and 4 exhibit stronger solution fluorescence than their aggregation-induced emission. The single crystal X-ray diffraction analysis of CFH-1 and CFH-3 showed that both of them adopt planar conformation and the CH···O hydrogen bonding plays a crucial role in their crystal packing. Meanwhile, there is a notable difference between them. Successive π-π stacking interaction was observed in the crystal packing of CFH-1, while the crystals of CFH-3 contain dimeric π-π stacking interaction. Their distinct crystal packing interactions result in their different fluorescence properties. Moreover, both CFH-1 and CFH-2 displayed excellent bioimaging performances in living cells. [ABSTRACT FROM AUTHOR]

A novel fluorescence probe for the detection of Al3+ was developed based on methionine protected gold nanoclusters (Met-AuNCs). A fluorescent Schiff base (an aldimine) is formed between the aldehyde group of salicylaldehyde (SA) and the amino groups of Met on the AuNCs, and developed for selective detection of Al3+ in aqueous solution. Al3+ can strongly bind with the Schiff base ligands, accompanied by the blue-shift and an obvious fluorescence emission enhancement at 455 nm. The limits of detection (LODs) of the probe are 2 pmol L−1 for Al3+. Moreover, the probe can successfully be used in fluorescence imaging of Al3+ in living cells (SHSY5Y cells), suggesting that the simple fluorescent probe has great potential use in biological imaging. [ABSTRACT FROM AUTHOR]

[Display omitted] • A "dual-locked" probe for detection of noradrenaline and HClO was synthesized. • The probe shows excellent selectivity for noradrenaline and HClO in cells. • The probe was successfully applied to accurately detect depressed cells. Due to the serious harm of depression to human health and quality of life, an accurate diagnosis of depression is warranted. For the complex etiology of depression, a single biomarker diagnostic method often leads to misdiagnosis. As noradrenaline and HClO are closely related to depression, a "dual-locked" fluorescence probe R-NE-HClO for diagnosing of depression through the simultaneous detection of noradrenaline and HClO was designed and synthesized. Fluorescence of R-NE-HClO can only be restored in the presence of both noradrenaline and HClO. The probe demonstrates excellent selectivity for noradrenaline and HClO and low cytotoxicity in cell imaging experiments. It is to be observed that we successfully applied the probe to accurately detect depressed cells which provides a possible tool for diagnosing depression. [ABSTRACT FROM AUTHOR]

[Display omitted] • Multifunctional CDs were prepared hydrothermally from eco-friendly Coccinia Grandis. • EC-Dots exhibited uniform globular shape with an average size of 4 nm (QY of 17 %). • EC-Dots emit bright fluorescence that is dependent on the excitation wavelength. • The current research provided a new platform in the field of bioimaging. • Also, the EC-Dots are a versatile component in various types of fluorescent ink. This study adopted an eco-friendly approach for the one-step hydrothermal conversion of sustainable Coccinia grandis into well-dispersed, uniform-sized carbon dots. The resulting eco-friendly carbon dots (EC-Dots) were harnessed for bioimaging and fluorescent ink applications. EC-Dots exhibited an average size of 4 nm. Further, cytotoxicity assessments on live nematodes revealed cell viability > 95 %. In-vivo studies showed excellent uptake and their ability to emit light in multiple colors, including blue, green, and red, achieved by adjusting the excitation wavelength. Additionally, the EC-Dots exhibited robust fluorescence in aqueous solutions and exceptional resistance to photobleaching, rendering them highly effective for generating fluorescent ink for drawing and writing. Thus, this research showcases an environmentally sustainable, cost-effective, and straightforward hydrothermal method for creating biocompatible EC-Dots with diverse hydrophilic properties. These synthesized EC-Dots stand as a promising platform for applications in fluorescent ink and in vivo bioimaging, offering a high level of safety with minimal cytotoxicity. [ABSTRACT FROM AUTHOR]

Herein, oxygen-doped g-C3N4 quantum dots (OCNQDs) were fabricated through sintering and ultrasonic-assisted liquid-phase exfoliation methods. The obtained OCNQDs with uniform size show high crystalline quality, and the average diameter is 6.7 ± 0.5 nm. Furthermore, the OCNQDs display excellent fluorescence properties, good water solubility, and excellent photo stability. The OCNQDs as fluorescence probe show high sensitivity and selectivity to Fe3+ ions. Furthermore, the fluorescent OCNQDs are applied for live cell imaging and Fe3+ ions detecting in living cells with low cytotoxicity, good biocompatibility, and high permeability. Overall, the fluorescent OCNQDs fabricated in this work can be promising candidates for a range of chemical sensors and bioimaging applications. [ABSTRACT FROM AUTHOR]

Squaraines (SQs) are unusual cyanine dyes with a unique resonance-stabilized zwitterionic structure. These dyes have attracted significant attention in the fields of organic electronics and organic photonics, due to their facile synthesis, intense and narrow visible and near-infrared absorption/emission, high photostability, low biotoxicity, etc. In this review, we summarize the recent progress of SQ-based fluorescent materials and their biomedical applications. After a brief introduction to SQs, general synthetic routes and design principles of SQ-based fluorescent materials, as well as their aggregation-induced luminescence behaviors, are discussed. Subsequently, their biomedical applications for cell imaging and as fluorescent sensors and therapeutic agents are introduced. Finally, a summary and perspective are given for promoting the development of SQs-based fluorescent materials. [ABSTRACT FROM AUTHOR]

[Display omitted] Carbon dots have garnered significant attention owing to their versatile and highly tunable optical properties; however, the origins and the underlying mechanism remains a subject of debate especially for dual fluorescent systems. Here, we have prepared carbon dots from glutathione and formamide precursors via a one-pot solvothermal synthesis. Steady state and dynamic techniques indicate that these dual fluorescent dots possess distinct emissive carbon-core and a molecular states, which are responsible for the blue and red optical signatures, respectively. To further glean information into the fluorescence mechanism, electrochemical analysis was used to measure the bandgaps of the two fluorescent states, while femtosecond transient absorption spectroscopy evidenced the two-state model based on the observed heterogeneity and bimodal spectral distribution. Our findings provide novel and fundamental insights on the optical properties of dual fluorescent dots, which can translate to more effective and targeted application development particularly in bioimaging, multiplexed sensing and photocatalysis. [ABSTRACT FROM AUTHOR]

By connecting 1,8-naphthalimide and indole sulfonate, a ratio fluorescent probe capable of differential detection of hydrogen sulfite and hypochlorite was synthesized for the first time. It was able to achieve the qualitative detection of HSO3− and ClO− with high sensitivity and selectivity, respectively. It provides a multi-purpose probe and is based on different emission channels without mutual interference. The probe has the advantages of larger Stokes shift (ClO−: 115 nm, HSO3−: 88 nm), longer λem (ClO−: 515 nm, HSO3−: 548 nm) and better water solubility (DMF/PBS = 1:99, v/v). In addition, the probe is a ratio fluorescence probe, which can detect fluorescence intensity with two different emission waves. It provides internal self-calibration, reduces interference from the background and increases detection accuracy. In vitro cytotoxicity and imaging experiments show that the probe can effectively perform the detection of exogenous HSO3− and ClO− in cells. It can also achieve the detection of HSO3− and ClO− in the plasma environment. Because the probe can detect endogenous ClO−, it also has a good prospect for biological application in identifying tumor cells. [ABSTRACT FROM AUTHOR]

A novel boron dipyrromethene (BODIPY)‐based fluorescent probe BDP−Pd was designed and synthesized. Upon coordination with Pd2+, the emission of the probe at 508 nm significantly increased, showing an 'OFF‐ON' fluorescence response. The complexation of BDP−Pd with Pd2+ in both acetonitrile and aqueous solution were then studied by absorption and fluorescence spectra. The binding stoichiometry between the probe and Pd2+ was found to be 1 : 2, and the binding constant was determined to be 8.5×1010 M−2 and 8.2×1010 M−2 in acetonitrile and aqueous solution, respectively. The probe exhibited a detection limit as low as 0.72 ppb toward Pd2+ with no obvious interference from up to 21 species of common metal ions, suggesting BDP−Pd as a sensitive and selective fluorescent probe for Pd2+ detection. The fast fluorescence 'OFF‐ON' phenomenon of the probe upon coordination with Pd2+ ions could be easily observed by a hand‐hold UV lamp under naked eye in solution as well as on homemade test trips. Density functional theory (DFT) calculations were carried out to give the optimized structure of complex BDP−Pd : 2Pd2+ and rationalize the detection mechanism through a prohibited intramolecular photoinduced electron transfer (PET) process. The bio‐imaging application of the probe was investigated and it showed excellent cell permeability for fluorescent imaging of Pd2+ ions in A549 human non‐small cell lung cancer cells. [ABSTRACT FROM AUTHOR]

Two red‐emitting dicyanomethylene‐4H‐pyran (DM) based fluorescent probes were designed and used for peroxynitrite (ONOO−) detection. Nevertheless, the aggregation‐caused quenching effect diminished the fluorescence and restricted their further applications. To overcome this problem, tetraphenylethylene (TPE) based glycoclusters were used to self‐assemble with these DM probes to obtain supramolecular water‐soluble glyco‐dots. This self‐assembly strategy enhanced the fluorescence intensity, leading to an enhanced selectivity and activity of the resulting glyco‐dot comparing to DM probes alone in PBS buffer. The glyco‐dots also exhibited better results during fluorescence sensing of intracellular ONOO− than the probes alone, thereby offering scope for the development of other similar supramolecular glyco‐systems for chemical biological studies. [ABSTRACT FROM AUTHOR]

The synthesis of a novel, and highly selective Fe3+ ion sensor based on anthrone‐spirolactam and its quinoline hybrid ligand is reported. The designed ligand displayed selective detection of Fe3+ ions with enhanced fluorescence emission. The complexation of Fe3+ ion led to a red shift of 32 nm from 420 nm to 452 nm, and a several fold increase in intensity with fluorescent green emission. The complexation (detection) of Fe3+ ions with ligand resulted in chelation enhanced fluorescence and intramolecular charge transfer through the inhibition of C=N isomerization. This hybrid sensor shows high sensitivity and selectivity, spontaneous response, and works on a wide pH range a minimum detection limit of 6.83 × 10−8 M. Importantly, the sensor works through the fluorescence turn‐on mechanism that overcomes the paramagnetic effect of Fe3+ ions. The binding mechanism between the ligand and the Fe3+ ions was established from the Job's plot method, optical studies, Fourier transfor infrared spectroscopy, NMR titration, fluorescence life‐time studies, and density functional theory optimization. The sensor displayed excellent results in the quantification of Fe3+ ions from real water samples. Furthermore, due to its biocompatibility nature, fluorescent spotting of Fe3+ ions in live cells revealed its bioimaging applications. [ABSTRACT FROM AUTHOR]

Nitro groups with a strong electron-withdrawing effect can powerfully influence the fluorescence of fluorophores. In this work, through adjusting the nitro group at the HBT fluorophore to construct a phenylhydrazone structure, two probes (HBTN and HBTH) were synthesized to detect OCl−. Consequently, HBTN with the nitro group quenched the fluorescence of HBT and HBTH without the nitro group causing a redshift of the fluorescence, which resulted in enhanced and ratiometric fluorescence signal changes during the detection process. Among them, HBTN shows good ability to selectively detect OCl− in the concentration range of 0–14 μM with the detection limit of 2.06 nM. Based on HBTN, a portable test strip for detecting OCl− was made for the convenient quantification of the OCl− concentration with a spectrophotometer, and exogenous and endogenous OCl− was successfully imaged in cells. [ABSTRACT FROM AUTHOR]

Fluorescent determinations of analytes have proven to be a powerful method due to their simplicity, low cost, detection limit, rapid photoluminescence response, and applicability to bioimaging. Fluorescence imaging as a powerful tool for monitoring biomolecules within the living systems. Schiff base has been extensively used as strongly absorbing and colorful chromophores in the design of chemosensors. In recent years, Schiff base based fluorescent probes have been developed for the detection of various toxic analytes and imaging of various analytes in biological systems. This review gives an overview of the important fluorescent sensors which are based on Schiff base, their approaches for molecular recognition, and their potential application in bioimaging studies. [ABSTRACT FROM AUTHOR]

The hydrothermal treatment of green carbon dots (CDs) is an appropriate fluorescent probe synthesis method. CDs are exploited as biological staining agents, especially for cellular detection and imaging. The nitrogen‐doped green carbon dots (N‐CDs) formation can improve the fluorescence intensity property in a one‐step process. Here, we report two N‐CDs from lemon and tomato extraction in the presence of hydroxylamine. Lemon and tomato N‐CDs showed the blue fluorescence under ultraviolet radiation of about 360 nm. The characterization of CDs and N‐CDs showed the presence of N‐H and C–N bonds which enhanced the fluorescence efficiency. The mean size of lemon and tomato N‐CDs were about 2 and 3 nm with an increased quantum yield (QY) of 5% and 3.38%, respectively. The CDs and N‐CDs cytotoxicity assay exhibited high cell viability approximately 85% and 73%, respectively. N‐CDs show superior fluorescent intensity in different solvents and significant stability under long‐time UV irradiation, different PH and high ionic strength. Our results indicated that the use of N‐CDs in cell imaging can lead to fluorescence intensity enhancement as well as proper biocompatibility. Therefore, the safe and high fluorescence intensity of green N‐CDs can be utilized for fluorescent probes in biolabeling and bioimaging applications. [ABSTRACT FROM AUTHOR]

• Simple hydrothermal route was adopted for the synthesis of fluorescent NR-CDs. • The average size of the NR-CDs was about 9 nm. • The NR-CDs show very less cytotoxicity on C. albicans. • The synthesized NR-CDs were utilized for the bio-imaging of C. albicans. Nitrogen doped carbon dots (N-CDs) are well documented as an outstanding fluorogenic material for protein tags, live cell imaging and protein-receptor based fluorescence sensors owing to its good optical features with less cytotoxicity and better water solubility. In this regard, the present work describes the synthesis of nitrogen rich blue fluorescent carbon dots (NR-CDs) through hydrothermal treatment of citric acid monohydrate (CA) and 2-aminopyridine (2-AP). The optical properties of NR-CDs are further analyzed by common analytical methods viz., Fourier transform infrared (FT-IR), UV–visible (UV–vis) and Fluorescence spectroscopies. The surface chemical composition and morphology of NR-CDs are acquired by X-ray photo electron spectroscopy (XPS) and high resolution transmission electron microscopy (HR-TEM), respectively. The NR-CDs produce blue fluorescent at 421 nm at the excitation wavelength of 310 nm, the calculated quantum yield is about 18% with respect to standard quinine sulfate. The synthesized NR-CDs contains 15.03 wt % of N revealed by XPS results. Further, the NR-CDs are used as a fluorescence staining agent for cell imaging of Candida albicans (C. albicans) and the cytotoxicity are also measured. All the outcomes proposed that the NR-CDs act as good staining agent for C. albicans with less cytotoxicity. [ABSTRACT FROM AUTHOR]

• Development of a novel red-emitting fluorescent probe (HSA) for the detection of Cys. • The probe can high sensitivity detect Cys with a low LOD. • Successfully verified the experimental results by the theoretical calculation study. • The probe can be used for exogenous Cys monitoring and endogenous Cys cell imaging experiments. Herein, we synthesized a red-emitting fluorescence turn-on probe (HSA) for specific detection of cysteine (Cys) over other biothiols (glutathione (GSH) and homocysteine (Hcy)). The acrylate group was chosen as the recognition site for specific discrimination of Cys. Absorption and emission spectra display a high selectivity towards Cys over GSH/Hcy, organic small-molecule interfering substances and anions, with a high sensitivity towards Cys (0.12 μM) in 1% ethanol-containing PBS buffer solution (25 mM, pH = 7.4). Density functional theory (DFT) and time-dependent DFT (TDDFT) calculations were conducted to clarify the luminescence mechanism of the probe. Furthermore, the probe was successfully applied to the determination of free Cys in human serum and the fluorescence imaging of endogenous Cys in living cells. [ABSTRACT FROM AUTHOR]

Abstract Three new rhodamine based probes 1 , 2 , 3 were synthesized and acted as fluorescence probes for Hg2+ detection in Tris - HCl/C 2 H 5 OH (v : v = 3: 7, 10 mM, pH = 7.2). Hg2+ induced a colorless solution of probes 1 , 2 , 3 to turn to naked-eye visible pink with a 44 - fold fluorescence enhancement at 576 nm. Probes 1 , 2 , 3 are highly selective to Hg2+ over other tested cations with the detection limits are 18 nM, 16 nM, 56 nM, respectively. What's more, the binding constants between probes 1 , 2 , 3 and Hg2+ are 5.0 × 106 M−1, 1.8 × 106 M−1, 1.5 × 106 M−1, respectively. The different detection limits and binding constants of probes 1 , 2 , 3 and Hg2+ may depend on the coordination of probes 1 , 2 , 3. The recognition mechanism of probes 1 , 2 , 3 towards Hg2+ is determinated by ESI - MS, DFT and indicates that a ring-opening of the spirolactam unit and formed complexes between probes 1 , 2 , 3 , resulting in chromogenic and fluorogenic changes. The probes 1 , 2 , 3 could be applied in both environmental and Hg2+ polluted samples due to the instantly and reversible "off-on" Hg2+ response, well cell permeability, cell imaging ability. Graphical abstract Rhodamine based "turn-on" chemodosimeter exhibited instant/reversible and excellent specificity towards Hg2+ in aqueous media and living cells. fx1 [ABSTRACT FROM AUTHOR]

Abstract Hydrogen sulfide (H 2 S) can undergo dual nucleophilic reaction, which is a wise and effective way to distinguish biothiols and H 2 S. A novel H 2 S fluorescence probe, 4-{2-[4-(2-disulfide pyridyl-benzoyloxy)-phenyl]-vinyl}-1-methyl-pyridinium[ e ]iodide (DSPBP), with two nucleophilic reaction sites has been developed. The spectra results showed that DSPBP could detect H 2 S in ratiometric and colorimetric signals and has excellent selectivity and sensitivity. The fluorescence ratiometric signals (F 520 /F 450) displayed a prominent increase from 0.74 to 7.08, the fluorescence color turned to yellow form blue simultaneously. The linear range was 2–14 μM and its detection limit was 25.7 nM. Moreover, the biocompatibility of DSPBP was fine and its toxicity was very low. It has been successfully used for imaging H 2 S in cells. Graphical Abstract Unlabelled Image Highlights • A ratiometric fluorescence probe (DSPBP) for H 2 S with bis-nucleophilic center was developed. • DSPBP showed rapid response time, high selectivity and sensitivity for H 2 S over biothiol. • DSPBP would used to detect H 2 S in living cells. [ABSTRACT FROM AUTHOR]

Abstract We reported a novel and readily synthesized fluorescent "turn-on" probe L (Dansyl-Glu-Pro-Gly-Cys) based on dansyl group combine tetrapeptide. The probe L exhibited highly sensitive fluorescent recognition to Cd2+ ions in HEPES buffer solutions (10.0 mM, pH 7.4). The 2:1 binding stoichiometry of L with Cd2+ were determined based on fluorescence titration and the Job's plot investigation. The competitive experiments were found to be highly selective for the Cd2+ ions even in the existence of excess competing metal ions including Zn2+, Pb2+, Hg2+ and Cu2+ ions. The binding constant of the complex L -Cd was calculated to be 5.18 × 1010 M−2, and showed great affinity compared to other probes. In addition, the detection limit of the probe L for Cd2+ ions was calculated to be 45 nM, which presented a pronounced sensitivity toward Cd2+ ions. Most importantly, the probe L had wide range of pH and good biocompatibility, and were successfully applied to selectively detected Cd2+ ions within pH range of 7–12 and bioimaging studies in live cells. Graphical Abstract Unlabelled Image Highlights • A novel fluorescent peptide-based probe (L) was synthesized. • L exhibited exclusively selective fluorescent "turn-on" response toward Cd2+ ions. • L displayed high sensitivity for Cd(II) with a low detection limit of 45 nM. • L could serve as a potential probe to detect Cd2+ ions in living cells. [ABSTRACT FROM AUTHOR]

Long wavelength (i.e., orange- to red-light) fluorescence emission and functionality are critically longing for the development and applications of carbon dots (CDs) toward biosensor and bioimaging analysis. Herein, the N-doped carbon dots (N-CDs) with bright orange fluorescence emission at 592 nm were facilely synthesized via p-phenylenediamine as a carbon precursor by microwave method. The as-prepared N-CDs exhibit favorable biocompatibility, excellent water solubility, highly optical stabilities and display sensitive pH response behavior. When the pH is decreased from 9.45 to 2.45, its emission fluorescence intensity will be significantly enhanced. The pKa value of N-CDs is 5.80 and it shows linear response to the physiological pH range of 4.45–7.00. Moreover, the N-CDs also possess high selectivity of hydrogen ions over common metal ions and some bioactive molecules, excellent photostability and reversibility. Based on this, a fluorescence sensing platform is established for the detection of pH in the environment. The N-CDs were successfully used as the fluorescent probe for cellular imaging and applied to monitor pH fluctuations in live cells based on its biocompatibility and cell membrane permeability. It is also anticipated that the N-CDs are potential bio-nano-materials for real-time tracking of the intracellular pH especially under physiological conditions in the disease diagnosis, biosensing and biomedical fields. [ABSTRACT FROM AUTHOR]

Benefiting from the excellent photostability and biocompatibility, fluorescent nanoclusters have recently emerged as a highly attractive bio-sensing and imaging material, especially in early diagnosis of cancer. However, their clinic applications were limited by the unsatisfactory specificity and the complex synthesis. In this study, novel methionine coated gold nanoclusters (Met-AuNCs) have been prepared via an easily-achievable one-pot synthetic method. The prepared Met-AuNCs showed high imaging-specificity: after incubating with Met-AuNCs for 1 h, cancer cells (including A549, Hela, MCF-7, HepG2) were fluorescent, while the normal cells (WI-38 and CHO) showed no fluorescence. According to a series of controlled experiments, the reason for the high imaging-selectivity was proposed to originate from the specific recognition of L-type amino acid transporter overexpressed in cancer cells. [ABSTRACT FROM AUTHOR]

A hydrothermal synthetic approach is developed for the preparation of graphitic carbon nitride quantum dots (g-C 3 N 4 QDs) from human urine. The reported synthetic method is green, simple, low-cost, less time-consuming, and can be used for the large-scale production of the g-C 3 N 4 QDs. The as-prepared g-C 3 N 4 QDs possess a high quantum yield of 15.7% by using quinine sulfate as a reference, and display excitation-wavelength dependent fluorescent emission. In addition, the g-C 3 N 4 QDs exhibit high photostability, low cytotoxicity. and are successfully used as fluorescent probes for cell multicolor imaging. It is believed that the valuable nanomaterials, g-C 3 N 4 QDs, which are transformed from the human bodily wastes, are promising in diverse chemical applications. [ABSTRACT FROM AUTHOR]

Taking advantage of the special Hg 2+ -promoted deprotection reaction of dithioacetals and the well-known coumarin chromophore, novel reactive fluorescent probes ( C3 and C4 ) towards mercury ions were designed and synthesized. Upon the addition of mercury ions, probe C3 displayed remarkable fluorescence quenching, which was beneficial to the production of a high signal output during sensing process. Differently, compound C4 displayed dramatic red-shift in both fluorescence (60 nm) and absorption (60 nm) spectra, with the detection limit of 90 nM. By virtue of this unique chemical reaction, compound C4 had selective response towards Hg 2+ over other metal ions and only the addition of Hg 2+ could lead to apparent emission and absorption spectra changes. Moreover, C4 was successfully applied to microscopic imaging for the detection of Hg 2+ in HeLa cells with ratiometric fluorescent methods. [ABSTRACT FROM AUTHOR]

Development of thiol-specific fluorescent probes with selectivity in different thiol compounds is more practical and significant than those without that capacity. In this work, a new quinoline-derived fluorophore, hydroxyl-substituted quinoline-benzo[ d ]oxazole 6 with high fluorescence quantum yield is synthesized and esterified with acrylic acid to afford two fluorescent probes, BQA-1 and BQA-2 for selectively discriminating Cys from Hcys/GSH based on conjugate addition-cyclization mechanism. BQA-1 exhibits a large ratiometric fluorescence response toward Cys in aqueous pH 7.4 solution with big emission peak-shifting from 383 nm to 518 nm, over 130 nm. The detection limit is determined to be as low as 0.59 μM. In contrast to BQA-1 , BQA-2 whose acrylic ester moiety is further modified with pyridine group, displays a turn-on fluorescence response to Cys with detection limit of 0.98 μM. Both BQA-1 and BQA-2 have relatively weak response to another two biothiols, Hcys and GSH and nearly no response to other nucleophiles. Furthermore, the potential application for the detection of biothiols in living cells has been demonstrated by cell imaging experiment. [ABSTRACT FROM AUTHOR]

Red/near-infrared (NIR) fluorescent molecules with aggregation-induced emission (AIE) characteristics are of great interest in bioimaging and therapeutic applications. However, their complicated synthetic approaches remain the major barrier to implementing these applications. Herein, a one-pot synthetic strategy to prepare a series of red/NIR-emissive AIE luminogens (AIEgens) by fine-tuning their molecular structures and substituents is reported. The obtained AIEgens possess simple structures, good solubilities, large Stokes shifts, and bright emissions, which enable their applications toward in vitro and in vivo imaging without any pre-encapsulation or -modification steps. Excellent targeting specificities to lipid droplets (LDs), remarkable photostabilities, high brightness, and low working concentrations in cell imaging application make them remarkably impressive and superior to commercially available LD-specific dyes. Interestingly, these AIEgens can efficiently generate reactive oxygen species upon visible light irradiation, endowing their effective application for photodynamic ablation of cancer cells. This study, thus, not only demonstrates a facile synthesis of red/NIR AIEgens for dual applications in simultaneous imaging and therapy, but also offers an ideal architecture for the construction of AIEgens with long emission wavelengths. [ABSTRACT FROM AUTHOR]

A supramolecular ligand for the specific detection of Cd 2+ ions, [pyridine-2,6-diylbis (methyleneimino-2,1-phenylene)]bis(phenyl methanone) ( L ) was synthesized, and characterized by various spectral techniques and single crystal X-ray crystallography. The L exhibits “turn-on” fluorescence and excellent selectivity towards Cd 2+ ions in acetonitrile/HEPES buffer medium (1:5 v/v). The lowest quantum yield and shorter emission lifetime of L (Φ = 0.0293, τ = 9.98 ns) was corroborated by the operation of PET process. This PET is quenched during the complex formation between L and Cd 2+ leads to high quantum yield and longer emission lifetime (Φ = 0.1770, τ = 13.46 ns). The L forms 1:1 complex with Cd 2+ is confirmed by Job’s plot and ESI-Mass techniques. The binding of L with Cd 2+ was studied by UV–vis and NMR. The reversible of L.Cd 2+ with EDTA establishes the reuse of L. The lower detection limit of L was found to be 10.21 nM. The impact of fluorescence with respect to pH, time, temperature and solvent concentrations was investigated to find its practical applications. The sensor was applied for the determination of Cd 2+ ions in water samples. DFT studies explain the binding mechanism between the L and Cd 2+ . The cell imaging studies established that L has been used to detect the intracellular Cd 2+ ions in HeLa cells. [ABSTRACT FROM AUTHOR]

Diethylenetriamine-β-cyclodextrin (3N-β-CD)-modified carbon quantum dots were synthesized for the first time via a one-step hydrothermal method using citric acid as the carbon source and diethylenetriamine-β-cyclodextrin as the nitrogen source. The synthesized carbon quantum dots were used as fluorescent probes for the selective detection of Hg2+ and Fe3+ in an aqueous solution and live cell imaging application on Hela cancer cell line. [Display omitted] • 3 N -CQDs were synthesized readily using citric acid as the carbon source by hydrothermal method. • The 3 N -CQDs showed a favorable fluorescence performance towards Hg2+ and Fe3+ detection. • Cytotoxicity assay indicated that the 3 N -CQDs had extremely low cytotoxicity. • The 3 N -CQDs showed good biocompatibility and bioimaging property in the cell imaging. Diethylenetriamine-β-cyclodextrin-modified carbon quantum dots (3 N -CQDs) were synthesized via a one-step hydrothermal method using citric acid as the carbon source and diethylenetriamine-β-cyclodextrin (3 N-β-CD) as the nitrogen source. The successful preparation of 3 N -CQDs were revealed by infrared absorption spectroscopy, ultraviolet (UV)-visible absorption spectroscopy, fluorescence spectroscopy, XRD, XPS, TEM, and TG. Further spectroscopic studies showed that the synthesized carbon quantum dots offered good anti-interference capability. The relative fluorescence quantum yield was 67.2 %. The limits of detection for Hg2+ and Fe3+ were 0.25 µM and 0.57 μM, respectively. Cytotoxicity and imaging studies showed that the prepared carbon quantum dots had low cytotoxicity, good biocompatibility, and good cellular imaging capability for HeLa cells. They offered fluorescent sensing of Hg2+ and Fe3+ in live cells. Therefore, 3 N -CQDs were ideal fluorescent probes for the detection of Hg2+ and Fe3+ in water. [ABSTRACT FROM AUTHOR]

In this paper, a novel fluorescent probe HBT-H based on benzothiazole has been designed and synthesized. The probe has excellent selectivity and can be used for specific detection of Cu2+. Under 360 nm UV excitation, the probe HBT-H itself has a fluorescence emission peak at 487 nm, emitting cyan blue fluorescence, fluorescence quenching after added Cu2+. The detection limit of Cu2+ recognition by HBT-H probe was calculated as 3.08 × 10−7 M. According to Job's plot and high resolution mass spectrometry, the complexation ratio of HBT-H to Cu2+ was 2:1. The sensor mechanism was confirmed as excited intramolecular proton transfer (ESIPT). Surprisingly, the probe HBT-H system responded well to pH, showing green fluorescence under acidic conditions and cyan blue fluorescence under alkaline conditions. In addition, the probe HBT-H has excellent membrane permeability and low cytotoxicity, which could not only detect Cu2+ in actual water samples, but also recognize Cu2+ in human breast cancer cells (MCF-7). [Display omitted] • The probe could selectively detect Cu2+ from solutions or water samples. • The detection limit of Cu2+ with this probe was as low as 3.08 × 10−7 M. • The probe could be used to judge the acid-base properties colorimetrically. • The probe was successfully applied to the imaging of human breast cancer cells. [ABSTRACT FROM AUTHOR]

Surface modified ZnO nanomaterial is widely used in the field of bioimaging worldwide due to its optical properties, electronic characteristics and biocompatibility. Fluorescent enhanced, Polyquaternium-7(PQ7) capped, ZnO hexagonal nano disks (ZnO-PQ7) were synthesised by simple wet chemical method. The structural and optical properties of ZnO-PQ7 hexagonal nano disks were characterized using XRD, UV-Visible, Fluorescence, HRTEM, EDAX and FTIR studies. The size of synthesised ZnO-PQ7 were around 30-45 nm as confirmed by HRTEM studies. Fluorescence emission intensity increased with increase in PQ7 concentration. ZnO-PQ7 was further conjugated with folic acid (FA) to target human breast cancer cell line (MCF-7) via EDC/NHS coupling chemistry. Conjugation of folic acid with ZnO-PQ7 was confirmed by FTIR studies. The cell viability study using Methyl thiazolyltetrazolium(MTT) assay has demonstrated that the ZnO-PQ7 conjugated FA composites (ZnO-PQ7-FA) exhibit low toxicity towards MCF-7 up to a concentration of 125 μg/mL. Confocal laser scanning microscopic images confirmed the uptake of ZnO-PQ7-FA nanoparticles by MCF-7 cells. This study reveals ZnO-PQ7-FA nano disks as a potential imaging agent for detection of cancer cells. The synthesis route reported in this article is simple and easy to follow for the synthesis of ZnO-PQ7-FA in bulk quantities with high purity. [ABSTRACT FROM AUTHOR]

A turn-on fluorescent probe ( FN) for detection of hydrazine has been developed. Probe FN exhibited high selectivity and excellent sensitivity towards hydrazine with a detection limit as low as 4.6 × 10 M. Probe FN selectively reacts with hydrazine (NH) in a physiological environment, leading to an off-on fluorescence response along with the color change from colorless to yellow, allowing colorimetric detection of hydrazine by the naked eye. Furthermore, probe FN was successfully applied for visualizing hydrazine in living cells. [ABSTRACT FROM AUTHOR]

Three naphthol Schiff base-type fluorescent sensors, 1,3-Bis(2-hydroxy-1-naphthylideneamino)propane (L1) , 1,3-Bis(1-naphthylideneamino)-2-hydroxypropane (L2) and 1,3-Bis(2-hydroxy-1-naphthylideneamino)-2-hydroxypropane (L3) , have been synthesized. Their recognition abilities for Al 3 + are studied by fluorescence spectra. Coordination with Al 3 + inhibited the C N isomerization of Schiff base which intensely increase the fluorescence of L1 – L3 . Possessing a suitable space coordination structure, L3 is a best selective probe for Al 3 + over other metal ions in MeOH–HEPES buffer (3/7, V/V, pH = 6.6, 25 °C, λ em = 435 nm). A turn-on ratio over 140-fold is triggered with the addition of 1.0 equiv. Al 3 + to L3 . The binding constant K a of L3- Al 3 + is found to be 1.01 × 10 6.5 M − 1 in a 1:1 complex mode. The detection limit for Al 3 + is 0.05 μM. Theoretical calculations have also been included in support of the configuration of the L3- Al 3 + complex. Importantly, the probe L3 has been successfully used for fluorescence imaging in colon cancer SW480 cells. [ABSTRACT FROM AUTHOR]

This paper reports a near-infrared chemosensor for phosphate ions (Pi) based on Pi-controlled fluorescence off-on switching mechanism. The Pi sensor displayed colorimetric responses towards Pi with a distinct color change from green to yellow in aqueous media. Apyrase, a hydrolytic enzyme, was used to accelerate the endogenous Pi production for evaluating in vivo fluorescent sensing ability of the new cyanine based probe ( 1 ). In addition, the present study demonstrated potential of the newly developed chemosensor in bioimaging by performing experiments in Chinese hamster ovary (CHO) cells both in vitro and in vivo. [ABSTRACT FROM AUTHOR]

A novel p -dimethylaminobenzamide-based Schiff base derivative DTBL was synthesized via a simple reaction and utilized as a “turn-on” fluorescent indicator for copper ion (Cu 2+ ). It showed extraordinary high selectivity toward Cu 2+ in MeCN–H 2 O (v/v = 3:2, pH = 5) HOAc-NaOAc buffer solution, and the fluorescence intensity change were noticeable for the Cu 2+ detection even in the presence of different kinds of foreign ions and compounds at very high concentrations. The 2:1 stoichiometry of DTBL-Cu 2+ complex was calculated from Job’s plot based on fluorescence titrations. The good linear relationship easily exhibited a dynamic response range for Cu 2+ from 0 to 3.4 μM and the detection limit (0.32 nM) of DTBL for Cu 2+ was far lower than the maximum allowable level of the WHO limit (30 μM) for drinking water. Moreover, the adaptability of DTBL for biological applications was also demonstrated by fluorescence imaging of intracellular Cu 2+ in living cells. The results indicate that DTBL should be available for the research on the biological and environmental applications associated with Cu 2+ . [ABSTRACT FROM AUTHOR]

Herein, a facile way to synthesize Cu nanoclusters (CuNCs) has been proposed while insulin played the role as a stabilizer. Specifically, this type of CuNCs existed in tunable diameters of 4-5 nm, and exhibited bright reddish-orange fluorescence with a quantum yield of 7.4 %. Interestingly, the fluorescence intensity of CuNCs could be obviously enhanced and more stable by introducing Eu. Moreover, this proposed Eu@CuNCs with low toxicity and near-infrared fluorescence may provide potential to broaden avenues for various applications in bioimaging and beyond. [ABSTRACT FROM AUTHOR]

[Display omitted] • A simple ratiometric fluorescence method for detection of alkaline phosphatase. • The ratiometric fluorescence method was constructed based on in situ reactions. • It was applied to detection of serum alkaline phosphatase and inhibitor screening. • Cellular imaging of alkaline phosphatase was performed in MCF-7 cells. Alkaline phosphatase (ALP) is an important biomarker, it is of great significance to develop a sensitive and efficient analytical method for ALP. In this study, an in situ reaction based ratiometric fluorescence assay for ALP was proposed. l -ascorbic acid-2-phosphate (AA2P) was used as a substrate for ALP, and Cu2+/ o -phenylenediamine (OPD) were involved in this system. Cu2+ can oxidize OPD to 2,3-diaminophenazine (OPDox) with an emission centered at 566 nm. The presence of ALP can catalyze the hydrolysis of AA2P to ascorbic acid (AA), which will inhibit the production of OPDox and reduce the corresponding fluorescence intensity, and AA will react with OPD to generate 3-(dihydroxyethyl)furan[3,4- b ]quinoxalin-1-one (DFQ) with an emission peak at 447 nm. The fluorescence ratio of F447/F566 has a linear relationship with ALP activity. The proposed method is highly sensitive, finely selective, cost efficiency and easy to operate, it exhibits good linearity in the range of 0.5–22 and 22–40 mU·mL−1, with a detection limit as low as 0.06 mU·mL−1. The excellent applicability of this strategy in human serum samples and MCF-7 cells imaging suggests that this method has promising prospects for biomedical research. [ABSTRACT FROM AUTHOR]

A fluorescent probe Eu(tdl) 2 abp for efficient and specific recognition of hydrogen sulfide (H 2 S) was successfully synthesized and characterized by NMR and MS. Eu(tdl) 2 abp showed "on-off" fluorescence signals for H 2 S and its color changes could be identified with naked eyes. Eu(tdl) 2 abp had short response time (2 min) to H 2 S, high selectivity and good anti-interference, large stokes shift (207 nm). In various samples, when H 2 S existed, the azide group was reduced to amine group, resulting in closed-circuit fluorescence signal, and the fluorescence intensity reached the degree of quenching without being affected by other interference. At the same time, there was a good linear relationship between relative fluorescence intensity and H 2 S concentration. By calculation, the high sensitivity (LOD) is 0.64 μM. Eu(tdl) 2 abp was successfully used for the sensitive detection of H 2 S in natural water and living cells. [Display omitted] • A probe Eu(tdl) 2 abp was successfully prepared, synthesized, and applied for H 2 S detection. • Eu(tdl) 2 abp can perform high efficiency and specificity colorimetric and fluorescent double signal recognition for H 2 S. • The Eu(tdl) 2 abp has been successfully used for imaging H 2 S in living cells and natural water. Using 4-([2,2′: 6′, 2′- terpyridin] -4′-yl) -N, N-dimethylaniline (tdl) as auxiliary ligand and 6-azido-2,2′-bipyridine (abp) as recognition ligand, a europium complex fluorescent probe Eu(4-([2,2′: 6′, 2′-terpyridin] -4′ -yl) -N, N-dimethylaniline) 2 –6-azido-2,2′-bipyridine Eu(tdl) 2 abp for efficient and specific recognition of hydrogen sulfide (H 2 S) was successfully synthesized and characterized by NMR and MS. Eu(tdl) 2 abp represented "on-off" fluorescence signals for H 2 S and its color changes could be identified with naked eyes. Eu(tdl) 2 abp had short response time (2 min) to H 2 S, high selectivity and good anti-interference, large stokes shift (207 nm). In various samples, when H 2 S existed, the azide group was reduced to amine group, resulting in closed fluorescence signal, and the fluorescence intensity reached the degree of quenching without being affected by other interference. At the same time, there was a good linear relationship between relative fluorescence intensity and H 2 S concentration with the detection limit (LOD) of 0.64 μM. The sensing mechanism of Eu(tdl) 2 abp to detect H 2 S was characterized by 1H NMR and HR-MS. Eu(tdl) 2 abp was used with success for the sensitive detection of H 2 S in natural water and living cells. [ABSTRACT FROM AUTHOR]

[Display omitted] • An indene-chalcone-based fluorescence probe with lysosome-targeting has been developed. • The crystal structure of the probe was reported. • The probe could monitor carboxylesterase (CEs) with a short response time (20 min), low detection limit (1.3 × 10−4 U/mL) and large stokes shift (155 nm). • The probe has been successfully applied to the imaging of endogenous CEs in the lysosomes of living cells and zebrafish. An indene-chalcone-based fluorescence probe 1 was synthesized and characterized. Under physiological conditions (containing 5% DMSO), probe 1 showed satisfactory stability with a low background signal and recognized carboxylesterases (CEs) based on the catalytic hydrolysis of ester groups, releasing a significant green fluorescence. Probe 1 presents several features including a short response time (within 20 min), low detection limit (1.3 × 10−4 U/mL) and large stokes shift (over 155 nm). Notably, commercial lysosomal dye co-staining experiments illustrated the lysosomal localization function of 1 , with the probe also being used for cell and zebrafish imaging of endogenous CEs. [ABSTRACT FROM AUTHOR]

A new highly selective and sensitive chemosensor 1 for both Al 3+ and F − was designed and synthesized. 1 could detect both Al 3+ and F − with turn-on fluorescence behavior in a nearly perfect aqueous solution. The binding stoichiometry of receptor 1 with Al 3+ and F − was proposed to be 1:1, respectively, based on Job plot, 1 H NMR titration and ESI-mass spectrometry analysis. The detection limits (1.12 μM for Al 3+ and 7.01 μM for F − ) of 1 for Al 3+ and F − were lower than the World Health Organization guidelines (7.41 μM for Al 3+ and 79 μM for F − ) for drinking water. Chemosensor 1 was also successfully applied to living cells for simultaneous detection and quantification of both Al 3+ and F − . Moreover, the sensing mechanisms of 1 toward Al 3+ and F − were explained by theoretical calculations. [ABSTRACT FROM AUTHOR]

A rhodamine derivative ZP1 , appended with two 1,2,3-triazole moieties via a diaminopropyl linker, is a chromogenic and fluorogenic sensor for Zn 2+ . In the presence of Zn 2+ , a colorless solution of ZP1 becomes pink with a maximum absorption of 555 nm and a large fluorescence enhancement (140-fold) at 579 nm (Φ = 0.12). ZP1 is highly selective with Zn 2+ , among other metal ions including Cd 2+ , with a binding constant ( K a ) of 7.4 × 10 3 M −1 and a detection limit of 1 μM (65 ppb). Similar rhodamine derivatives with a shorter linker or with a single triazolyl group cannot function as a Zn 2+ chemosensor. ZP1 is membrane-permeable and could react with intracellular Zn 2+ in cultured HeLa cells. [ABSTRACT FROM AUTHOR]

A new turn-on fluorescent quinolone tetrazole based chemosensor (QT-1) is designed and synthesized which shows high sensitivity and selectivity for Zn 2+ ions in aqueous acetonitrile solution. QT-1 probe easily distinguishes Zn 2+ ions from Cd 2+ ions. Job's plot analysis suggested that the binding of QT-1 and Zn 2+ ions is probably a 1:1 stoichiometry. Thus QT-1 can be employed for fluorescent imaging of Zn 2+ ions in living cells. [ABSTRACT FROM AUTHOR]

[Display omitted] • Switchable two-color graphene quantum dot was designed and synthesized by via one-step pyrolysis. • Synergy of histidine, serine, pentaethylenehexamine and boron realizes unique optical behavior. • Two-color fluorescence emissions can be sensitively switched by varying excitation wavelength. • The optical probe was successfully applied in pH detection and bioimaging with high sensitivity. • The study provides approach for design and synthesis of various functional graphene quantum dots. Graphene quantum dots have been widely applied in biosensing, fluorescence imaging, biomedicine, energy storage and conversion and catalysis, but design and synthesis of polychromatic graphene quantum dot with high luminous efficiency still faces great challenges. The study reports synthesis of histidine, serine and pentaethylenehexamine-functionalized and boron-doped graphene quantum dot (HSPB-GQD) via one-step pyrolysis. The resulting HSPB-GQD consists of graphene sheets of 2–5 nm with carboxyl, hydroxyl, amino, imino and imidazole. Synergy of histidine, serine, pentaethylenehexamine and boron atoms improves the luminescence behavior. This realizes unique switchable two-color luminescence. UV excitation of 370 nm produces one strong blue fluorescence with the maximum emission wavelength of 455 nm and quantum yield of 72.34%. Vis. excitation of 480 nm produces one strong yellow fluorescence with the maximum emission wavelength of 560 nm and quantum yield of 72.59%. The multiple proton dissociation system constructed by nitrogen-containing and oxygen-containing groups makes yellow fluorescence sensitive to environmental pH value. The intensity linearly increases with increasing pH in the range of 4.5–10.0. Organic molecules and inorganic ions do not interfere pH detection. HSPB-GQD as a promising fluorescence probe with negligible effect on cell viability was successfully applied to pH detection in biological and environmental water samples and cell imaging. [ABSTRACT FROM AUTHOR]

A series of new rationale designed 2,1,3-benzothiadiazole (BTD) fluorescent derivatives has been synthesized and applied for cellular selective staining of cancer cells in cell-imaging experiments. Four new synthesized BTD derivatives showed only poor or reasonable cellular selection, but with excellent fluorescence intensity and almost no background signal emitting at the blue or green channels. The knowledge gained by analysing their molecular architecture, however, allowed the planning and synthesis of a fluorescent BTD, which was then successfully tested and showed superior mitochondrial selection with outstanding results in bioimaging experiments in living cells. The new marker (named Splendor) was then compared with the commercially available MitoTracker Red (also through co-staining experiments) and showed far better mitochondrial selection, fluorescence intensity and chemical stability. Mitochondrial imaging and tracking (dynamic changes) was possible using Splendor during the whole cellular division cycle. DFT calculations were performed to offer insights into the origin of the chemical- and photostability of BTD derivatives. In addition, molecular docking calculations hint at a potential molecular target for the BTD derivatives in the mitochondrial protein adenine nucleotide translocase, which may explain the mitochondrial selectivity of Splendor versus the other four BTD derivatives. [ABSTRACT FROM AUTHOR]

The design, synthesis, properties, and cell imaging applications of a series of 2-pyridyl disulfide based fluorescent probes (WSP1, WSP2, WSP3, WSP4 and WSP5) for hydrogen sulfide detection are reported. The strategy is based on the dual-nucleophilicity of hydrogen sulfide. A hydrogen sulfide mediated tandem nucleophilic substitution-cyclization reaction is used to release the fluorophores and turn on the fluorescence. The probes showed high sensitivity and selectivity for hydrogen sulfide over other reactive sulfur species, including cysteine and glutathione. [ABSTRACT FROM AUTHOR]

[Display omitted] • Single-pot large-scale synthesis of C-dots from peptic digest of animal-tissue. • Emission of strong blue fluorescence at 350 nm comparable to synthetic organic dyes. • Prospective fluorescent probe for specific metal ions detection. • Excellent chelating agent for metal-ion toxicity for fast complexation & exocytosis. • Potential application in bioimaging due to quick uptake with minimal cytotoxicity. In recent years, there has been an increased interest in the use of fluorescent carbon dots (C-dots) as an alternative to toxic synthetic organic dyes in live cell imaging, medical diagnostics and other diverse biomedical applications. In the present work, highly fluorescent C-dots have been prepared from commercially available peptic digest of animal tissue, without using any additional chemical reagent for surface functionalization. The synthesized C-dots are monodispersed nanomaterials with hydroxyl, carboxyl and amino surface functionalities and remain stable in high ionic strength media and over a wide range of pH. They exhibit a strong blue fluorescence upon excitation at 350 nm with a high quantum yield of 61%. The potential use of these C-dots as fluorescent nanoprobe for specific metal ions (Cu2+ and Hg2+) detection through chelation, radical scavenging and cellular imaging has been investigated. These highly fluorescent labels show rapid cellular internalization without hampering cellular integrity. Cell proliferation assay demonstrates that these C-dots have minimal cell toxicity even at a high concentration of 3 mg/mL. They show significant quenching on incubation with cells pretreated with Cu2+ and Hg2+ ions. They also show rapid exocytosis from cells showcasing their high potential for chelation therapy. Thus, this study offers a scalable synthesis approach for highly fluorescent and bio-compatible C-dots from a cost-effective precursor, which can be used for specific metal ions detection and their removal from cells through chelation via exocytosis. They can also be used as an alternate to synthetic organic dyes for fluorescence-based cell-imaging. [ABSTRACT FROM AUTHOR]

Abstract: A new Schiff base 1-[(1H-1,2,4-triazole-3-ylimino)-methyl]-naphthalene-2-ol (H2L) exhibiting high selectivity for Al3+ ion over other metal ions, such as Li+, Na+, K+, Ca2+, Mg2+, Cu2+, Co2+, Mn2+, Ni2+, Zn2+, Cd2+, Pb2+, Fe3+, and Cr3+ was prepared, and it is sensitive for Al3+ with the detection limit reaching 0.69μM in DMF. Upon addition of Al3+, the significant enhancement (32-fold) of fluorescence intensity for H2L at 466nm is ascribed to the formation of a 1:1 complex between Al3+ and H2L, which is denoted as the chelation-enhanced fluorescence (CHEF) effect. The confocal fluorescence microscopy experiments demonstrate that H2L could be used as a fluorescent probe for Al3+ in living cells. [Copyright &y& Elsevier]

Highlights: [•] A “turn-on” fluorescent chemosensor for the detection of Zn(II) was facilely synthesized. [•] Detection of Zn(II) can be performed in water at neutral pH with high sensitivity. [•] The chemosensor exhibits remarkably selective to Zn(II) over other metal ions. [•] The chemosensor could be efficiently delivered to live cells for bioimaging of Zn(II). [Copyright &y& Elsevier]

[Display omitted] • A rational design of probe Chol-6RN strives to minimize the interference between recognition moiety and functional moiety. • The probe Chol-6RN is better than the control probe Chol-RN in the linearity and the detection limit. • The cell imaging experiments show that Chol-6RN has good biocompatibility and membrane permeability. To improve the sensitivity and detection limit of probe, we made good use of the advantage of 6-carboxyrhodamine to design a new cholesterol-conjugated fluorescent probe Chol-6RN for Cu2+ detection. The probe Chol-6RN exhibits a sensitive response towards Cu2+ by fluorescence spectrum in aqueous solution. The linearity of Chol-6RN is from 5 μM to 40 μM of Cu2+ with an excellent linear correlation (R2 = 0.99110) and the detection limit for Cu2+ is 1.12 μM, they are better than the control probe Chol-RN. The MTT assay indicates that Chol-6RN is negligible cytotoxicity to HeLa cells after 24 h at a concentration less than 30 μM. The cell imaging displays that Chol-6RN is capable of detecting Cu2+ in live cells and the sensibility of Chol-6RN is better than Chol-RN. [ABSTRACT FROM AUTHOR]