Search

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]

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]

Abstract High-efficient orange fluorescence nitrogen-doped carbon dots (N-CDs) were facilely prepared from P-phenylenediamine as a precursor via hydrothermal method. The as-prepared N-CDs with an average diameter of 3.65 nm displayed excitation-independent emission at 590 nm. The N-CDs demonstrated a remarkable fluorescence enhancement behavior with the increase of pH. A sigmoidal curve was well fitted using BiDoseResp equation with pK a1 3.57 and pK a2 6.01, which can be ascribed to the unique surface properties of N-CDs. Two-segment linear ranges of 2.6–4.6 and 5.0–6.8 broaden the response range to pH of the orange-emission N-CDs to some extent. The confocal fluorescent microscopic images of SMMC7721 cells were performed successfully, which demonstrating that N-CDs possess exceptional cell membrane permeability and can implement as biosensing platform to monitor pH fluctuations in living cells. Graphical abstract Image 1 Highlights • The long-wavelength fluorescent N-CDs were prepared by one-step hydrothermal method and using water as the reaction solvent. • The N-CDs displayed excitation-independent emission at 590 nm, which can better applied in biosensor and bioimaging. • The N-CDs shown a remarkable fluorescence enhancement behavior with the increase of pH corresponding to double pK a. • The N-CDs possessed favorable biocompatibility, high photostability, ultra-low toxicity and cellular labeling capability. [ABSTRACT FROM AUTHOR]

At present, few genetically encoded fluorescent probes are currently available for the analysis of toxic heavy metal ions, and most have poor performance that cannot meet the requirements of sensitive and dynamic detection in living cells. In this study, we designed a single fluorescent protein-based probe sfGFP-MerBD, which can specifically response to Hg2+ with high binding affinity and wide dynamic range. More importantly, the developing probe can timely and reversibly monitor changes of Hg2+ concentration in living mammalian cells. The excellent performance of this probe is largely due to the recognition element of the probe, MerBD, which adopts an unusual planar trigonometric coordination configuration with Hg2+, and the coordination can cause enough conformational change to influence the fluorescence of skeleton protein sfGFP coupled with it. The small peptide MerBD was delicately designed based on the three-dimensional structure of metalloprotein MerR. This novel design strategy solves the challenging problems that there are few natural functional proteins in the process of constructing fluorescent probes for toxic metal ions and some functional proteins cannot be directly used as recognition elements. Based on the new strategy, more genetically encoded fluorescent probes of toxic heavy metal ions can be efficiently constructed and applied in the future. [Display omitted] • Genetically encoded probes are ideal tools in living cellular imaging. • Few genetically encoded probes related for toxic heavy metal are currently available. • Novel strategy is adopted in constructing the probe sfGFP-MerBD for sensing Hg2+. • The probe maintains the unusual planar trigonometric coordination with Hg2+. • The probe responses to Hg2+ with high binding affinity and wide dynamic range. [ABSTRACT FROM AUTHOR]

Fluorescent nitrogen and sulfur co-doped carbon dots (NSCDs) were synthesized by a one-step pyrolysis strategy using casein as carbon, nitrogen and sulfur sources, and characterized by UV-vis spectrum, fluorescent spectrum, X-ray photoelectron spectroscopy (XPS) and FT-IR, etc. The synthesized NSCDs displayed a blue emission under ultraviolet illumination with a quantum yield of 31.8%, and a good aqueous solubility, photostability and biocompatibility. It was found that the fluorescence intensity of NSCDs could be selectively quenched by Hg2+, so NSCDs was used as an effective probe for the detection of Hg2+. The linear range and the limit of detection (LOD) of the fluorescent sensor based on NSCDs for the detection of Hg2+ were 0.01-0.25 μM and 6.5 nM, respectively. Spiked water samples were detected by the sensor with the recovery of 95.4-106.3% and relative standard deviation (RSD) of 3.6-8.6%. It was also observed that the quenched NSCDs-Hg2+ system could be restored by the addition of biothiols such as l-cysteine (Lcy), homocysteine (Hcy) and glutathione (GSH), thus NSCDs-Hg2+ system was employed as a fluorescent sensor for the detection of biothiols. The linear range and LOD of the NSCDs-Hg2+ system were 1-10 μM and 23.6 nM for Lcy, 0.2-2.5 μM and 12.3 nM for Hcy, and 0.1-2.0 μM and 16.8 nM for GSH, respectively. The NSCDs-Hg2+ system was applied for the detection of biothiols in serum samples with satisfied results. In addition, the study in vitro imaging HeLa cells revealed that the synthesized NSCDs could be used as effective fluorescent probes in cellular imaging without noticeable cytotoxicity. [ABSTRACT FROM AUTHOR]

A facile and eco-friendly approach to prepare nitrogen(N)- and sulfur(S)-doped carbon dots (CDs) by one step microwave-assisted pyrolysis of the precursors with dl -malic acid as carbon source, ethanolamine and ethane-sulfonic acid as N and S dopants, respectively, was reported. Through the extensive investigation on morphology, chemical structures and optical properties of the carbon dots, it was found that the obtained CDs exhibited good luminescence stability, high resistance to photo bleaching and favorite solubility. Compared with undoped CDs, adding the N or S dopant could give rise to a slightly smaller particle size and a long fluorescence lifetime of CDs. Moreover, the optimal N-CDs was successfully employed as good multicolor cell imaging probes due to its fine dispersion in water, excitation-dependent emission, excellent biocompatibility and low toxicity. Besides, such N-CDs showed a wide detection range and excellent accuracy as fluorescent probe for Fe 3+ ions. This probe enabled the selective detection of Fe 3+ ions with a linear range of 6.0–200 μM and a limit of detection of 0.80 μM. [ABSTRACT FROM AUTHOR]

In this work, we reported the first use of a novel fluorescent probe for phoxim detection based on yellowish-green emissive carbon quantum dots (CQDs). By facile one-pot hydrothermal treatment of citric acid and p-phenylenediamine, the CQDs with yellowish-green luminescence were synthesized. The sensing mechanism is based on the quenching effect of phoxim on the fluorescence emission of CQDs by inner filter effect (IFE). The CQDs showed a good sensitivity and selectivity to phoxim detection and dual good linear relationships were provided in the concentration ranges of 1–10 μM and 10–98 μM, associated with the limit of detection of 0.09 μM. The proposed assay has been allowed to detect phoxim in real samples with satisfying recoveries ranging from 93 to 105.9%. Furthermore, due to the low cytotoxicity and excellent biocompatibility, the as-prepared CQDs was successfully used for cell imaging, demonstrating the considerable potential applications of such CQDs in biological field. [Display omitted] • A novel sensing platform based on yellowish-green emitting CQDs was developed. • The proposed method exhibited high selectivity and sensitivity towards phoxim. • The new analytical method was feasible for phoxim determination in real samples. • The as-prepared CQDs was successfully used for cell imaging. [ABSTRACT FROM AUTHOR]

Hg(II) is well-known for quenching fluorescence in a distance dependent manner. Nevertheless, when we exposed the fluorophore of a green fluorescent protein (GFP) toward Hg(II), through H148C mutation, the GFP fluorescence could be “lighted up” by Hg(II) down to sub-nM level. The detection linear range is 0.5–3.0 nM for protein solutions at 8.0 nM. The GFPH148C protein displayed a promising selectivity toward Hg(II) and also the cellular imaging capacity. Spectra measurements suggested that the ground-state redistribution of protein contributed to the fluorescence enhancement, which was found not limited to Hg(II), and thus presented an opening for building a pool of GFP-based chemosensors toward other heavy metal ions. [ABSTRACT FROM AUTHOR]

Hydrogen sulfide (H 2 S) is a typical gas signal molecule that plays a vital role in various pathological courses. Despite having the accumulated knowledge on the physiological functions of H 2 S in many diseases, the process in the measurement of its level in mitochondria during oxidative stress is still far away from the expectation. In this regard, it is great significant to design a fluorescent probe for accurately monitoring the dynamics of H 2 S during oxidative stress. In this work, we firstly synthesized an oxidative stress activated fluorescence probe QM-RSH for tracking H 2 S level in mitochondria. It exhibited high selectivity and sensitivity for detecting H 2 S with lower limit of detection (LOD = 44.6 nM) in the presence of H 2 O 2. QM-RSH can be successfully applied to accurately monitor the fluctuation of H 2 S level during oxidative stress without interference from other physiological processes in living cells and zebrafish. Therefore, this multifunctional probe QM-RSH has great potential as an image tool in biological research. It also provides a novel strategy for designing fluorescent probe to investigate biomolecular information and signaling pathways under specific physiological conditions. [Display omitted] •A novel multifunction fluorescent probe QM-RSH was designed and synthesized. • QM-RSH can sequentially detect H 2 O 2 and H 2 S in two signal channels. • QM-RSH exhibited brighter NIR fluorescence and lower detection limit for H 2 O 2 (80.3 nM) and H 2 S (44.6 nM). • QM-RSH can be applied to accurately monitor H 2 S fluctuation during oxidative stress, avoiding interference from other physiological processes. • QM-RSH is used to investigate the main factors of H 2 S up-regulation during oxidative stress. [ABSTRACT FROM AUTHOR]

The detection of metal ions is of particular importance for monitoring environmental pollution and life metabolic activities. However, it is still a challenge to achieve Fe3+ detection with specific sensitivity and rapid response, especially in the presence of chelating agents for Fe3+ ions. Herein, a novel fluorescence probe for Fe3+, i.e., amide derivative of [1,2,4]triazolo[1,5-a] pyrimidine (TP, Id), was synthesized, featuring specific Fe3+ selectivity, rapid quenching (5 s), low limit of detection (0.82 μM), good permeability and low cytotoxicity. More importantly, Id can be used to identify and detect Fe3+ in the presence of existing strong chelating agents (e.g., EDTA) for Fe3+ ions. The results show that the as-synthesized fluorescence probe is particularly suitable as a bioimaging reagent to monitor intracellular Fe3+ in living HeLa cells. Furthermore, we proposed the binding mode for Id with Fe3+ ions and the light-emitting mechanism through high-resolution mass spectra and density function theory calculations, respectively. An Id -based test paper can be used to rapidly identify Fe3+. These results are expected to improve the development of new sensitive and specific fluorescent sensors for Fe3+. [Display omitted] • A novel amide derivative of [1,2,4]triazolo[1,5-a]pyrimidine fluorescence probe Id for Fe3+ ions was first reported with specific, rapid response to Fe3+ ions and low cytotoxicity. • The probe Id could detect Fe3+ ions in the presence of strong chelating agents (e.g., EDTA) of Fe3+ ions and the Id -based test paper could identify Fe3+ ions rapidly. [ABSTRACT FROM AUTHOR]

A turn-on fluorescent nanoprobe (named AAP-1), based on an aggregation-induced emission luminogen (AIEgen), is disclosed for the detection of adenosine triphosphate (ATP), which is an essential element in the biological system. Organic fluorophore (named TPE-TA) consists of tetraphenylethylene (TPE, sensing and signaling moiety) and mono-triamine (TA, sensing moiety), and it forms an aggregated form in aqueous media as a nanoprobe AAP-1. The nanoprobe AAP-1 has multiple electrostatic interactions as well as hydrophobic interactions with ATP, and it displays superior selectivity toward ATP, reliable sensitivity, with a detection limit around 0.275 ppb, and fast responsive (signal within 10 s). Such a fluorescent probe to monitor ATP has been actively pursued throughout fundamental and translational research areas. In vitro assay and a successful cellular ATP imaging application was demonstrated in cancer cells and embryonic stem cells. We expect that our work warrants further ATP-related studies throughout a variety of fields. Image 1 • AIEgen-based nanoprobe for the ATP sensing and imaging was disclosed. • The nanoprobe showed high selectivity, sensitivity, and fast response time. • The fluorescence imaging of ATP in human cancer cells and embryonic stem cells were successfully demonstrated. [ABSTRACT FROM AUTHOR]