A novel water-soluble mitochondria-targeted ratiometric fluorescent probe (Cl-2) is presented. Cl-2 can respond selectively to SO2 derivatives within 1 min. Notably, Cl-2 can be used to monitor successfully the concentration change of endogenously generated SO2 derivatives in living cells.

A series of “submarines”, which composed of gold nanoparticles and modified with rhodamine and fluorescein derivatives, were presented. With dual sensitive units for both acidic and basic environment, these “gold nano-submarines” not only allow efficient intracellular pH mapping but also provide more accurate quantitative detection of pH alteration under different stimuli with distinct pH quantification range. Moreover, they even have the ability to pass through the blood brain barrier (BBB).Keywords: blood brain barrier; fluorescein; gold nanoparticles; in vivo; pH map; rhodamine

Endogenous sulfur dioxide (SO2) is an important gaseous signal molecule, which was also regarded as one of the reactive sulfur spaces (RSS) and closely related to cardiovascular diseases and many neurological disorders. However, the design and synthesis of fluorescent probes with near-infrared-emission which can detect mitochondrial SO2 and its derivatives in living cells still remain unresolved. Herein, a biotin and coumarin-benzoindole conjugate BCS-1 was presented as a ratiometric and colorimetric fluorescent probe for tracing SO2 derivatives with excellent selectivity and rapid responsibility. Notably, it is the first mitochondria-targeted near-infrared-emission probe that could selectively detect SO2 in tumor cells. BCS-1 could selectively enter into mitochondria of tumor cells, and the detection limit for SO2 derivatives was determined as 72 nM.Keywords: mitochondria; near-infrared-emission; ratiometric fluorescent probe; sulfur dioxide; tumor-specific probe

A ratiometric fluorescent probe (RMClO-2) for ClO− based on the conjugate of coumarin–rhodamine was presented, which could sense ClO− with fast response (within 5 s), high sensitivity and excellent selectivity. More importantly, RMClO-2 is the first mitochondria-targeted ratiometric fluorescent probe to image exogenous and endogenous ClO−.

A ratiometric fluorescent probe for SO2 derivatives based on the conjugate of carbazole and indolium was presented, which could selectively respond to HSO3− over other thiol compounds. More importantly, CZ-Id is a novel mitochondria-targeted ratiometric fluorescent probe to image exogenous SO2 derivatives.

An in situ generated BINOL–DPA–Zn(II) complex is presented as a chemo-sensing ensemble for the recognition of phosphate-based molecules. The ensemble showed high sensitivity and selectivity for pyrophosphates (PPi), and it could be successfully applied in imaging PPi in living cells. Notably, the R1–Zn(ii) ensemble exhibited a very low detection limit (95 nM) for PPi and could realize the real time detection of PPi by the naked eye through precipitate experiments. The ensemble also showed good selectivity towards ATP, and the selectivity coefficient for PPi and ATP was calculated to be 4.1/2.8.

The terpyridine anthracene ligand L1 was synthesized and characterized. L1 is a ratiometric fluorescent probe for Cd2+ with a recognition mechanism based on intramolecular charge transfer (ICT). An L1-Cd(II) complex was isolated, and its structure was established using single-crystal XRD. The L1-Cd(II) complex was able to serve as a novel reversible chemosensing ensemble to allow ratiometric response to pyrophosphate (PPi) in aqueous media. Moreover, the fluorescence imaging in living cells from these two emission channels suggested that L1 was a ratiometric probe for Cd2+, and the in situ generated L1-Cd(II) complex was also a ratiometric ensemble for PPi detection in living cells.

We presented a novel approach for pyrophosphate (PPi) sensing. Two tetraphenylethene (TPE)-functionalised pyridine salts (TPM and TPH) were designed and synthesized. Both of them exhibited weak emission in the solution state that originates from intramolecular charge transfer (ICT) from TPE to the pyridine; the addition of PPi into the TPM aqueous solution would enhance the fluorescence intensity, which eliminates the emission quenching effect of the iodide ion by the formation of PPi-sensor nanoparticles. The detection limit of TPM was determined to be as low as 133 nM. Meanwhile, a thin solid film of TPM that could detect PPi rapidly was conveniently prepared.

A novel “turn-on” fluorescent probe 3 for monitoring hypochlorous acid was investigated, which showed high selectivity and sensitivity to hypochlorous acid over other ROS and was loaded into cell media to image HClO.

A colorimetric and fluorescent probe C-Py-1 for ONOO− was prepared and it could exhibit high sensitivity and excellent selectivity toward ONOO− among reactive oxygen species (ROS) and reactive nitrogen species (RNS) with a rapid response time in 100% water solution. Meanwhile, C-Py-1 was successfully applied in the imaging of endogenous ONOO− in RAW264.7 cells.

A coumarin TCF-based water-soluble near-infrared fluorescent probe was presented, which could be used for the rapid, colorimetric and ratiometric detection of SO2 derivatives with a detection limit of 0.27 nM. Moreover, this probe could successfully image the analyte in living cells.

Two mitochondria-targeted real-time probes were presented, which could selectively respond to hypochlorite over other ROS. Meanwhile, the “off–on” probes could be successfully applied in the in vivo imaging of hypochlorite in living mice.

Two rhodamine-based polymers (P-1 and P-2) were prepared via free radical polymerization, which could serve as lysosome targeting probes with prominent pH sensitivity. The polymers exhibited suitable water solubility and the content of rhodamine in them was determined through 1H NMR and ultraviolet-visible absorption spectroscopy. Both P-1 and P-2 have excellent selectivity, membrane permeability and low cytotoxicity. Confocal microscopy was used to investigate the intracellular distribution of lysosomes and visualize pH-responsive changes in the liver of zebrafish. Moreover, fluorescence imaging of nude mice of P-1 and P-2 displayed a chance for the visualization of cancerous tissue in vivo by sensing the tumor acidic microenvironments.

Three new ferrocene–peptide compounds were designed and prepared. We investigated their gelling abilities and found that two of them were capable of gelling various organic solvents, especially alcohols. Gels also formed in mixed alcohol–water solvents, which decreased the critical gelation concentration (CGC) of the gels. Compound 1, comprised of a dipeptide (Phe-Phe) and ferrocene, acted as a novel low-molecular-weight gelator in the formation of metallogel 1 in isopropanol–water (v/v = 1:1). This gelation was found to be reversible under redox stimuli; changing of the redox state of ferrocene induced a reversible gel–sol phase transition. Additionally, gel 1 responded to β-CD as a result of host–guest interactions between this compound and ferrocene. With the addition of β-CD, the gel network gradually broke down, as demonstrated by SEM.

A selenium-contained fluorescent ‘turn-on’ probe D-HMSe was developed for monitoring hydrogen peroxide. The probe D-HMSe is highly selective to hydrogen peroxide over other reactive oxygen species (ROS). An aggregation-induced enhancement (AIE) phenomenon was involved in the sensing process.

Two rhodamine-based pH probes (RhP and RhPA) were synthesized via the click reaction. The probes exhibited high pH sensitivity and selectivity with significant fluorescence intensity enhancement. Cell imaging experiments demonstrated RhPA was a good lysosome targeting probe in living cells with low cytotoxicity and excellent photostability.

Three cholesterol-based low molecular weight gelators were synthesized, and their gelation abilities were investigated. These compounds formed gels in various organic solvents. Specifically, gel 1 formed by gelator 1 bearing proline as hydrophilic groups and cholesterol as a lipophilic group collapsed selectively in the presence of Asp and Glu.

An ensemble-based fluorescent sensor HS-1 + Cu2+ for detection of histidine is reported. Complex HS-1 + Cu2+ sensitively senses histidine at pH 7.4 in aqueous media. The quantitative determination of histidine in urine and fetal calf serum is also conducted.

The first triazole-containing fluorescent probe with excellent water-solubility for Pd2+ was presented. The results indicated that an amide–triazole–amide binding sequence was responsible for the unique affinity of PS-1 toward Pd2+. Among the tested metal ions, only Pd2+ could selectively quench the fluorescence of PS-1 under physiological conditions, while other common interference ions like Pt2+ and Ru3+ caused little changes. The successful fluorescence imaging of Pd2+ in HeLa cells implied the potential applications of PS-1 in biological Pd2+-analysis.

A dianthracene–cyclen conjugate was synthesized via ‘click’ chemistry, which could serve as an equal-equivalent responding chemosensor for Pb2+ in aqueous solution. Moreover, it could be successfully applied in the detection of Pb2+ in living cells and fetal calf serum.

A novel BINOL-based ratiometric fluorescent sensor (R2) is presented, which can selectively respond to Zn2+ over Cd2+ and other metal ions with fluorescence enhancement in aqueous solution. The R2 was successfully applied in the imaging of Zn2+ in living cells. Additionally, the in situ generated R2-Zn(II) ensemble could further serve as a probe to distinguish histidine from other amino acids via a displacement mode.

A coumarin-based reactive probe 1 is reported for the highly selective detection of Cu+. The benzylic ether (C–O) bond of probe 1 can be cleaved selectively by the reaction with Cu+ under a physiological reducing environment, resulting in a fluorescent change. The maximum emission peak exhibited a red shift from 410 nm to 472 nm, and a remarkable enhancement of emission intensity ratios (I472/I410) from 0.26 to 13.82 was observed.A coumarin-based reactive probe 1 is presented for the highly selective ratiometric detection of Cu+ in aqueous solutions under physiological reducing conditions.

A water-soluble imidazolium-based BINOL receptor R-1 was exploited, which could selectively sense DNA over other biologically relevant anions including nucleotides under physiological conditions. Upon addition of DNA, R-1 displayed notably blue-shifted and ratiometric fluorescence enhancement.

•A multifunctional and highly selective fluorescent probe 1 was presented.•Ensemble 1-Co(II) can selectively detect Zn2+, and 1-Cu(II) can recognize S2−.•1-Cu(II) could permeate the cell membrane and could image S2− in living biological samples.A coumarin-based multifunctional fluorescent sensor containing a di-2-picolylamine (DPA) moiety (1) was presented. Interestingly, this probe could similarly act as ON-OFF type fluorescent sensor for Co2+ and Cu2+, then in situ generated 1-Co(II) and 1-Cu(II) ensembles could further serve as OFF-ON type fluorescent sensors to achieve the discrimination of Zn2+ from Cd2+ and selective recognition of sulfide anion in aqueous solution via displacement approach, respectively. Specially, 1-Cu(II) could permeate the cell membrane and could be used in fluorescence imaging of S2− in living biological samples. These ON-OFF-ON type fluorescent sensors exhibited high selectivity and sensitivity towards the targets.A coumarin-based multifunctional ON-OFF-ON type fluorescent sensor was presented, which could discriminate Zn2+ from Cd2+ and selectively recognize sulfide anion in aqueous solution.

A reaction-based colorimetric and ratiometric fluorescent probe based on an ICT-strategy for selective detection of H2S that exploited the H2S-mediated reduction of nitrocompound to amines was explored. And it displayed high selectivity for H2S over other relevant reactive sulfur, oxygen, nitrogen species and other anions with more than 120 nm blue shift and the change of emission intensity ratio inducted by H2S was over 4750.

A multifunctional fluorescent sensor based on a cyclen-appended BINOL derivative (R-1) was synthesized and characterized. It can display on–off-type fluorescence change with high selectivity toward Cu(II) among 19 metal ions in 100% aqueous solution. Furthermore, the in situ generated R-1–Cu(II) ensemble could recover the quenched fluorescence upon the addition of sulfide anion resulting in a off–on-type sensing with a detection limit of micromolar range in the same medium. No interference was observed from other biothiols and anions, including GSH, l-Cys, DTT, and sulfates, making it a highly sensitive and selective sulfide probe.

A lipase-catalyzed direct Mannich reaction of arylamines with aromatic aldehydes and ketones including cyclohexanone, butanone and 1-hydroxy-2-propanone was developed under EtOH/H2O system in a “one-pot” strategy. A series of experiments on the promiscuous activity of lipases were performed to optimize the biocatalytic process, and a wide scope of substrates was expanded with good yields.Graphical abstractA lipase-catalyzed direct Mannich reaction of arylamines with aromatic aldehydes and ketones was developed under EtOH/H2O system in a “one-pot” strategy. A series of experiments on the promiscuous activity of lipases were performed to optimize the biocatalytic process, and a wide scope of substrates was expanded..Download full-size imageResearch highlights▶ The Mannich reaction was realized in “one pot” strategy in the presence of water. ▶ Solvents play an impartment role in this lipase promiscuious catalyzed Mannich reaction and protic solvents are better for this reaction. ▶ Water content has a great effect on the enzyme activity. ▶ The reaction was favored by electron-withdrawing substituents of aldehyde.

The terpyridine anthracene ligand L1 was synthesized and characterized. L1 is a ratiometric fluorescent probe for Cd2+ with a recognition mechanism based on intramolecular charge transfer (ICT). An L1-Cd(II) complex was isolated, and its structure was established using single-crystal XRD. The L1-Cd(II) complex was able to serve as a novel reversible chemosensing ensemble to allow ratiometric response to pyrophosphate (PPi) in aqueous media. Moreover, the fluorescence imaging in living cells from these two emission channels suggested that L1 was a ratiometric probe for Cd2+, and the in situ generated L1-Cd(II) complex was also a ratiometric ensemble for PPi detection in living cells.

A selenium-contained fluorescent ‘turn-on’ probe D-HMSe was developed for monitoring hydrogen peroxide. The probe D-HMSe is highly selective to hydrogen peroxide over other reactive oxygen species (ROS). An aggregation-induced enhancement (AIE) phenomenon was involved in the sensing process.

A ratiometric fluorescent probe (RMClO-2) for ClO− based on the conjugate of coumarin–rhodamine was presented, which could sense ClO− with fast response (within 5 s), high sensitivity and excellent selectivity. More importantly, RMClO-2 is the first mitochondria-targeted ratiometric fluorescent probe to image exogenous and endogenous ClO−.

A novel water-soluble mitochondria-targeted ratiometric fluorescent probe (Cl-2) is presented. Cl-2 can respond selectively to SO2 derivatives within 1 min. Notably, Cl-2 can be used to monitor successfully the concentration change of endogenously generated SO2 derivatives in living cells.

A reaction-based colorimetric and ratiometric fluorescent probe based on an ICT-strategy for selective detection of H2S that exploited the H2S-mediated reduction of nitrocompound to amines was explored. And it displayed high selectivity for H2S over other relevant reactive sulfur, oxygen, nitrogen species and other anions with more than 120 nm blue shift and the change of emission intensity ratio inducted by H2S was over 4750.

A water-soluble imidazolium-based BINOL receptor R-1 was exploited, which could selectively sense DNA over other biologically relevant anions including nucleotides under physiological conditions. Upon addition of DNA, R-1 displayed notably blue-shifted and ratiometric fluorescence enhancement.

An ensemble-based fluorescent sensor HS-1 + Cu2+ for detection of histidine is reported. Complex HS-1 + Cu2+ sensitively senses histidine at pH 7.4 in aqueous media. The quantitative determination of histidine in urine and fetal calf serum is also conducted.

Two mitochondria-targeted real-time probes were presented, which could selectively respond to hypochlorite over other ROS. Meanwhile, the “off–on” probes could be successfully applied in the in vivo imaging of hypochlorite in living mice.

A coumarin TCF-based water-soluble near-infrared fluorescent probe was presented, which could be used for the rapid, colorimetric and ratiometric detection of SO2 derivatives with a detection limit of 0.27 nM. Moreover, this probe could successfully image the analyte in living cells.

A colorimetric and fluorescent probe C-Py-1 for ONOO− was prepared and it could exhibit high sensitivity and excellent selectivity toward ONOO− among reactive oxygen species (ROS) and reactive nitrogen species (RNS) with a rapid response time in 100% water solution. Meanwhile, C-Py-1 was successfully applied in the imaging of endogenous ONOO− in RAW264.7 cells.

A ratiometric fluorescent probe for SO2 derivatives based on the conjugate of carbazole and indolium was presented, which could selectively respond to HSO3− over other thiol compounds. More importantly, CZ-Id is a novel mitochondria-targeted ratiometric fluorescent probe to image exogenous SO2 derivatives.