•A 1, 8-naphtylimide-based probe for UDP sensing is studied.•The sensor displays remarkable optical response towards UDP.•The sensor is applied in UDP fluorescence in vivo imaging in Hela cells and C. elegans.A 1, 8-naphtylimide-based probe 1 was developed for fluorescence sensing of uridine diphosphate (UDP). Probe 1 selectively recognized UDP in solvant system (DMSO-H2O) over other structurally similar nucleotides. Among all the tested targets, only the addition of UDP resulted in fluorescence enhancement of about 13-fold. Probe 1, the first receptor moiety without metal center, could recognize UDP only by multi H-bonds formed between the organic ligand and the base group in nucleotide. Moreover, probe 1 exhibited excellent cell permeability. The fluorescence imaging of UDP by probe 1 in Hela cells and Caenorhabditis elegans (C. elegans) demonstrated its potential as a fluorescent sensor for in vivo imaging of UDP.Download high-res image (322KB)Download full-size image

A rhodamine-based sensor (1) has been developed for the detection of chromium ions. Cr3+-induced opening of the rhodamine spirocycle in sensor (1) led to the distinct colorimetric and fluorescence responses. Among all the tested ions, only Cr3+ generated a significant fluorescence enhancement of up to 13-fold, which indicated the high selectivity of 1. Sensor (1) was successfully applied in the in vivo fluorescence imaging of Cr3+ in C. elegans. The results provided solid evidences for the future estimation of Cr3+ in environmental applications and tobacco samples.A rhodamine-based sensor has been developed for the detection of chromium ions, with a significant fluorescence enhancement of up to 13-fold. This sensor was a low toxic compound, and was successfully applied in the in vivo imaging of Cr3+ in C. elegans.Download high-res image (155KB)Download full-size image

•A near-infrared chemosensor for phosphate ions sensing is studied.•The sensor displays remarkable colorimetric response towards phosphate ions.•The sensor is applied in phosphate ions imaging in CHO cells in vitro and in vivo.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.

A rhodamine-based sensor has been developed for the detection of mercuric ions. The colorimetric and fluorescence responses, allowing naked-eye detections, are based on Hg2+-induced opening of the rhodamine spirocycle. Among all the testes ions, only Hg2+ generated a significant fluorescence enhancement of up to 300-fold, with a bright yellow–green emission. This sensor was a low toxic compound, and was successfully applied in the in vivo imaging of Hg2+ in Spill 2 cells and C. elegans. This approach provides a sensitive and accurate method for the estimation of Hg2+ in environmental, tobacco and biological applications.A rhodamine-based sensor has been developed for the detection of mercuric ions, with a significant fluorescence enhancement of up to 300-fold. This sensor was a low toxic compound, and was successfully applied in the in vivo imaging of Hg2+ in Spill 2 cells and C. elegans.

•A coumarin-based terpyridine–Zn2+ complex (1) was designed and synthesized.•Pyrophosphate resulted in a color change of 1 from brown to light yellow.•Pyrophosphate led to a 27-fold fluorescence enhancement of 1.•Probe 1 can combine with PPi to trace their enrichment and distribution in in vivo imaging.A coumarin-based terpyridine–zinc complex (1) was developed for sensing pyrophosphate. In aqueous media (CH3CN–HEPES), complex 1 had been proven to be an effective and selective colorimetric and fluorescent sensor for recognition of pyrophosphate over other structurally similar nucleotides and anions. Among all the tested targets, only addition of pyrophosphate resulted in a color change from brown to light yellow with a fluorescence enhancement of about 27-fold. The terpyridine–Zn2+ complex (1) formed a 2:1 binding mode with pyrophosphate by multi-hydrogen bonds. This complex was successfully applied to fluorescence imaging for pyrophosphate in Hi-5 cells and Caenorhabditis elegans, demonstrating its utility as a fluorescent sensor for detecting pyrophosphate in in vivo imaging.A coumarin-based terpyridine–zinc complex (1) was developed for sensing pyrophosphate. In aqueous media (CH3CN–HEPES), complex 1 had been proven to be an effective and selective colorimetric and fluorescent sensor for recognition of pyrophosphate over other structurally similar nucleotides and anions. Among all the tested targets, only addition of pyrophosphate resulted in a color change from brown to light yellow with a fluorescence enhancement of about 27-fold. The terpyridine–Zn2+ complex (1) formed a 2:1 binding mode with pyrophosphate by multi-hydrogen bonds. This complex was successfully applied to fluorescence imaging for pyrophosphate in Hi-5 cells and C. elegans, demonstrating its utility as a fluorescent sensor for detecting pyrophosphate in in vivo imaging.

Fluorescent probe 1, the first inorganic phosphate (Pi) targeted colorimetric and fluorescent probe to detect endogenous Pi in hemichannel-closed cells, has been developed. Probe 1 undergoes a unique Pi induced hydrolytic reaction in DMSO–HEPES (V/V = 9:1) buffered (0.02 M, pH 7.4) solutions that produces a colorimetric change associated with a 62 nm red-shift in the UV–vis absorption maximum and up to a 780-fold enhancement in the fluorescence intensity. The mechanistic proposal that these spectroscopic changes are associated with reaction Pi with 1 to form coumarin gains support from the results of theoretical calculations and mass spectrometry studies. Observations made in fluorescence imaging studies with HeLa cells and C. elegans show that 1 can be employed to monitor Pi production in vivo caused by apyrase-catalyzed ATP hydrolysis. Moreover, probe 1 was utilized to show that apoptosis of hemichannel-closed Sf9 cells is caused by Inx3 promoted dephosphorylation of Akt (RAC serine/threonine-protein kinase), leading to an elevation of the concentration of Pi. Overall, the study has produced the first fluorescent sensor 1 for endogenous inorganic phosphate. Moreover, the utility of 1 for measuring Pi release in vitro has been demonstrated and utilized to elucidate the mechanism of Inx3 action in hemichannel-closed Sf9 cells.

Two 1,8-naphthyridine-based N,O-chelated boron complexes (1 and 2) were designed as novel phosphate ion (Pi) probes, which are based on a methoxy oxalyl group reaction site. These two probes showed high selectivity for Pi detection without interference from ATP, PPi, or other anions. Dramatic color changes from colorless to light yellow were observed by addition of Pi to solutions of 1 and 2 in DMSO/HEPES buffer (0.02 M, pH 7.4) (V/V = 8:2). This qualitative color shift was accompanied by red-shifts in the UV–vis absorbance spectrum of approximately 43 nm for 1 and 46 nm for 2. Fluorescence quenching was observed in solutions of 1 (Φ = 0.31) and 2 (Φ = 0.23) upon addition of Pi. Probes 1 and 2 are the first two 1,8-naphthyridine-based boron complexes developed which serve as colorimetric probes capable of highly selective detection of Pi over other phosphate-based chemical species including P2O74−, ATP, ADP, AMP, GTP, GDP, GMP, TTP, TDP, TMP, UTP, UDP, and UMP. The in vivo imaging results demonstrate that 1 and 2 are able to permeate into the HeLa cells and Caenorhabditis elegans to detect Pi via a strong fluorescence intensity change.Two 1,8-naphthyridine-based N,O-chelated boron complexes (1 and 2) were designed as novel phosphate ion (Pi) probes, which are based on a methoxy oxalyl group reaction site. These two probes showed high selectivity for Pi detection without interference from ATP, PPi, or other anions. Dramatic color changes from colorless to light yellow were observed by the addition of Pi to solutions of 1 and 2 in DMSO/HEPES buffer (0.02 M, pH 7.4) (V/V = 8:2). This qualitative color shift was accompanied by red-shifts in the UV–vis absorbance spectrum of approximately 43 nm for 1 and 46 nm for 2. Fluorescence quenching was observed in solutions of 1 (Φ = 0.31) and 2 (Φ = 0.23) upon addition of Pi. Probes 1 and 2 are the first two 1,8-naphthyridine-based boron complexes developed which serve as colorimetric probes capable of highly selective detection of Pi over other phosphate-based chemical species including P2O74−, ATP, ADP, AMP, GTP, GDP, GMP, TTP, TDP, TMP, UTP, UDP, and UMP. The in vivo imaging results demonstrate that 1 and 2 are able to permeate into the HeLa cells and Caenorhabditis elegans to detect Pi via a strong fluorescence intensity change.

A lysosome-targeted fluorescent chemodosimeter, 1, was developed for monitoring endogenous and exogenous H2S by in vivo imaging of HeLa cells, D. melanogaster and C. elegans. In the tests of mutated C. elegans (SRP-6 nulls), chemodosimeter 1 could trace the accumulation of lysosome and lysosomal injury with a high resolution.

•We synthesized a highly selective and sensitive colorimetric signal-responding anion-sensor 1.•The solution of 1 changed from yellow color to red for F−, to orange for AcO− and to brown for OH−.•The color changes of F− are attributed to the deprotonation of the hydroxyl moiety in the binding group.•The commonly competing ions induced none or relatively negligible optical perturbations in the UV–Vis spectral analyses.A highly selective and sensitive colorimetric signal-responding anion-sensor 1, based on 1,8-naphthalimide, was prepared and spectroscopically characterized. Strong visible colorimetric changes in 1 were observed only in the presence of fluoride (yellow-to-red color change), acetate (yellow-to-orange color change) and hydroxyl (yellow-to-brown color change) anions in DMSO. In the UV–Vis spectroscopy titration of F−, two different processes were observed as the concentration of F− increased. In the lower concentration of F−, hydrogen-bond interactions were formed in the first process. The second process of the spectral changes, in the higher concentration of F−, was attributed to the deprotonation of the hydroxyl moiety in the binding group, which was associated with the enhancement in the push-pull effect of the internal charge-transfer transition. The commonly competing Cl−, Br−, I−, ClO4−, PF6−, HSO4− and H2PO4− ions induced none or relatively negligible optical perturbations in the UV–Vis spectral analyses. The present naked-eye detection system provides a simple and rapid method for the detection of fluoride, acetate and hydroxyl anions without interferences from other halide anions or common anions, including ClO4−, PF6−, HSO4− and H2PO4−.

A 1,8-naphthalimide derivative (1) was intentionally designed and synthesized as a new turn-on fluorescent probe for the detection of zinc ion with high selectivity over other metal ions at pH 7.4 in aqueous media (CH3CN/HEPES, V/V = 6:4). The reaction mechanism is attributed to the replacement of the protons of the O–H groups by zinc ion at the binding site and production of fluorescence which is blocked in the photo-induced electron transfer (PET) process. Remarkable enhancement of up to 13-fold in fluorescence intensity with a 38 nm red-shift was achieved in the detection of zinc ion. Compound 1 was successfully applied to the fluorescence imaging of zinc ion, with a fluorescence emission color produced in the cell nucleus different from that produced in the cytoplasm, in A549, BEAS-2B, CHO, Hela, and HepG2 cells. Furthermore, cytokinesis-block micronucleus (CBMN) assay was carried out in CHO cells using 1 and zinc ion as the imaging agents, showing that the 1-Zn2+ agent is a nucleic acid selective stain, which could be applied in MN assays in different kinds of cell lines.A 1,8-naphthalimide derivative (1) was intentionally designed and synthesized as a new turn-on fluorescent probe for the detection of zinc ion in aqueous media (CH3CN/HEPES, V/V = 6:4). Remarkable enhancement of up to 13-fold in fluorescence intensity with a 38 nm red-shift was achieved in the detection of zinc ion. Compound 1 was successfully applied to the fluorescence imaging of zinc ion, with a fluorescence emission color produced in the cell nucleus different from that produced in the cytoplasm, in A549, BEAS-2B, CHO, Hela, and HepG2 cells. Furthermore, cytokinesis-block micronucleus (CBMN) assay was carried out in CHO cells using 1 and zinc ion as the imaging agents, showing that the 1-Zn2+ agent is a nucleic acid selective stain, which could be applied in MN assays in different kinds of cell lines.

A 1,8-naphthalimide–Cu(II) ensemble was rationally designed and synthesized as a new turn-on fluorescent probe utilizing the ‘chemosensing ensemble’ method for detections of thiols (Cys, Hcy and GSH) with high selectivity over other α-amino acids at pH 7.4 in organic aqueous media (EtOH/HEPES, v/v = 9:1). The recognition mechanism was attributed to the remove Cu(II) from the 1,8-naphthalimide–Cu(II) ensemble by thiols and the release of flurescence of ligand 1. Remarkable fluorescence enhancements were therefore observed in the sensing process of thiols by the 1,8-naphthalimide–Cu(II) ensemble. Furthermore, the 1,8-naphthalimide–Cu(II) ensemble was successfully applied to the fluorescence imaging of thiols in CHO cells with high sensitivity and selectivity.A naphthalimide–Cu(II) ensemble was rationally designed and synthesized as a new turn-on fluorescent probe utilizing the ‘chemosensing ensemble’ method for detections of thiols (Cys, Hcy and GSH) with high selectivity over other α-amino acids. The recognition mechanism was attributed to the remove of Cu(II) from the naphthalimide–Cu(II) ensemble by thiols and the release of florescence of ligand 1. Remarkable fluorescence enhancements were therefore observed in the sensing process of thiols by the naphthalimide–Cu(II) ensemble in the vitro assays and in the fluorescence imaging in CHO cells with high sensitivity and selectivity.

A 1,8-naphthyridine modified rhodamine B derivative (1) has been designed and synthesized. Compound 1 is the first 1,8-naphthyridine-modified rhodamine B sensor that can detect Cu2+ selectively with a dramatic color change from colorless to pink. The complex of 1 and Cu2+ was utilized as a chemosensing ensemble for cysteine (Cys), homocysteine (Hcy), and glutathione (GSH) detection, which showed highly sensitive and selective colorimetric response to Cys, Hcy, and GSH among the tested naturally occurring α-amino acids in EtOH-HEPES (0.02 M, pH 7.4) (3:7, v/v) buffer solution.A 1,8-naphthyridine modified rhodamine B derivative (1) has been designed and synthesized. Compound 1 is the first 1,8-naphthyridine-modified rhodamine B sensor that can detect Cu2+ selectively with a dramatic color change from colorless to pink. The complex of 1 and Cu2+ was utilized as a chemosensing ensemble for cysteine (Cys), homocysteine (Hcy), and glutathione (GSH) detection, which showed highly sensitive and selective colorimetric response to Cys, Hcy, and GSH among the tested naturally occurring α-amino acids in EtOH-HEPES (0.02 M, pH 7.4) (3:7, v/v) buffer solution.

A lysosome-targeted fluorescent chemodosimeter, 1, was developed for monitoring endogenous and exogenous H2S by in vivo imaging of HeLa cells, D. melanogaster and C. elegans. In the tests of mutated C. elegans (SRP-6 nulls), chemodosimeter 1 could trace the accumulation of lysosome and lysosomal injury with a high resolution.