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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]

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]

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]