Hoechst-naphthalimide dyad with dual emissions as specific and ratiometric sensor for nucleus DNA damage

A ratiometric fluorescent sensor（Hoe-NI） was developed by connecting a nucleus targeted Hoechst unit to a naphthalimide dye via ＂click chemistry＂. The sensor achieves high specific nucleus labeling with wash-free staining method in various kinds of living cells. The fluorescence ratio of the two emission bands（450 nm for Hoechst and 505 nm for naphthalimide） is changed sensitively to the variation of DNA concentrations, which provides the quantitative information in the processes of DNA damage induced by hydroxyl radicals and antitumor drug. Therefore, Hoe-NI is a recommendable sensor for the monitoring of nuclear DNA damage that reveals the health status of cells.

Ratiometric Fluorescence Detection of 6-Mercaptopurine Based on the Nanohybrid of Fluorescence Carbon Dots and Gold Nanoclusters

The development of a simple and accurate quantitative method for the determination of 6-mercaptopurine (6-MP) is of great importance because of its serious side effects. Ratiometric fluorescence (RF) sensors are not subject to interference from environmental factors, and exhibit enhanced precision and accuracy. Therefore, a novel RF sensor for the selective detection of 6-MP was developed. The present work reports a sensitive and selective RF sensor for the detection of 6-mercaptopurine, by hybridizing carbon nanodots (CDots) and gold nanoclusters (AuNCs) capped with bovine serum albumin (BSA). The CDots serve as the reference signal and the AuNCs as the reporter. On addition of the 6-MP, AuNCs formed aggregates, because the existing cross-links within the AuNCs and BSA structure were broken in favour of the Au-S bonds, which can enhance the fluorescence of AuNCs, while the fluorescence of CDots is stable against 6-MP, leading to distinct ratiometric fluorescence changes when exposed to 6-MP. 6-MP could be detected in the range of 0 - 30.22 μM with a detection limit of 54 nM. The developed sensor was applied for the determination of 6-MP in human serum samples and satisfactory results were obtained.

A Fluorescein Derivative Chemosensor Combined with Triplet-Triplet Annihilation Upconversion System for Ratiometric Sensing of Cysteine

A derivative of fluorescein,fluorescein O,O-diacrylate(FODA),was utilized in a triplet-triplet annihilation upconversion(TTA-UC)system to develop a composite ratiometric chemosensor capable of detecting cysteine(Cys).FODA acted as both the probe for Cys and the energy acceptor for upconversion(UC)emission,thereby making UC a responsive signal to Cys.In addition,the phosphorescence signal of the sensitizer in the TTA-UC system remained constant and did not respond to Cys,making it an ideal internal reference signal for constructing a ratiometric sensor.Through this simple strategy,traditional fluorescent probes can be combined with TTA-UC system to establish a ratiometric sensing platform,which can be applied in more scenarios due to the longer wavelength excitation.

Monitoring intracellular pH fluctuation with an excited-state intramolecular proton transfer-based ratiometric fluorescent sensor

Intracellular pH is a key parameter related to various biological and pathological processes.In this study,a ratiometric pH fluorescent sensor ABTT was developed harnessing the amino-type excited-state intramolecular proton transfer(ESIPT) process.Relying on whether the ESIPT proceeds normally or not,ABTT exhibited the yellow fluorescence in acidic media,or cyan fluorescence in basic condition.According to the variation,ABTT behaved as a promising sensor which possessed fast and reversible response to pH change without interference from the biological substances,and exported a steady ratiometric signal(I_(478)/I_(546)).Moreover,due to the ESIPT effect,large Stokes shift and high quantum yield were also exhibited in ABTT.Furthermore,ABTT was applied for monitoring the pH changes in living cells and visualizing the pH fluctuations under oxidative stress successfully.These results elucidated great potential of ABTT in understanding pH-dependent physiological and pathological processes.

MODULATION OF FRET THROUGH THE SPECTRAL-OVERLAP STRATEGY

Fluorescence resonance energy transfer(FRET)is an important photophysical mechanism whichfinds many applications in biophotonics,particularly in biological sensing and imaging.It is well known,there are two major factors that determine the efficiency of FRET.One is the distance between the donor and the acceptor,and the other is the overlap of the donor's emission and the acceptor's absorption spectra.However,while the distance-modulation of FRET is very popular,the spectral-overlap-modulation draws much less attention.In this talk,I would like to illustrate the importance of the strategy of spectral-overlapmodulation.The presentation will include our works on the construction of highly efficient FRET systems featuring the short and rigid linker between the donor and acceptor moieties,and several typical examples of spectral-overlap-modulation strategy applied in the development of ratiometric sensors.

A Water-Stable 3D Eu(Ⅲ)-Organic Framework as a Bi-Functional Ratiometric Luminescent Sensor for Fast, Sensitive and Selective Detection of ODZ and Hg^(2+) in Aqueous Media

The fast,sensitive and selective detection of some antibiotics and heavy metal cations in water is highly desirable for environmental protection and human health,but it is still currently challenging.In this work,a new luminescent Eu(Ⅲ)-based metalorganic framework(MOF),{[(CH_(3))_(2)NH_(2)][Eu(L)2(H_(2)O)_(2)]·xDMF}n(1)[H_(2)L=4,4’-((naphthalene-1,4-dicarbonyl)bis(azanediyl))dibenzoic acid],was solvothermally synthesized.Complex 1 exhibits good water stability and luminescent property and could serve as a bifunctional ratiometric luminescent sensor for fast,sensitive and selective detection of ornidazole(ODZ)and Hg^(2+)in aqueous solution.The corresponding luminescent mechanism has also been discussed.This work indicates that 1 as a promising luminescent material exhibits luminescent quenching behavior for ODZ and luminescent enhancement behavior for Hg^(2+)in H_(2)O,which will promote the practical application of Ln-MOF-based ratiometric luminescent sensors in monitoring antibiotics and metal ions pollutants in the environmental water matrices.

A novel colorimetric and ratiometric NIR fluorescent sensor for glutathione based on dicyanomethylene-4H-pyran in living cells

Glutathione(GSH)plays a critical role in maintaining oxidation-reduction homeostasis in biological systems.Considering the detection of GSH by fluorescence sensors is limited by either the short wavelength emission or the poor photostability,a highly stable colorimetric and ratiometric NIR fluorescent sensor(DCM-S)for GSH detection has been constructed on the basis of dicyanomethylene-4H-pyran(DCM)chromophore.The specific disulfide bond is incorporated via a carbamate linker as the GSH responsive group,which simultaneously blue-shifts and quenches the fluorescence.Upon addition of GSH,DCM-S exhibits outstanding colorimetric(from yellow to red)and ratiometric fluorescent response with the 6-fold enhancement of NIR fluorescence at 665 nm in quantum yield.More importantly,the GSH-treated DCM-S(DCM-NH_2 actually)possesses 20-fold longer fluorescence half-life period as well as much better photostability than the FDA-approved ICG.Finally,the ratiometric detection of GSH is also successfully operated in the living cell imaging,exhibiting NIR fluorescence and large Stokes shift(215 nm)with nearly no background fluorescence interference.As a consequence,DCM-S can be utilized as colorimetric and ratiometric NIR fluorescent sensor for GSH,with a great potential in the development of GSH-induced drug delivery system.

A New Ratio-Metric pH Probe,“ThiAKS Green”for Live-Cell pH Measurements

Deviation of the H+concentration from optimum values within the organelles is closely associated with irregular cellular functions that cause the onset of various diseases.Therefore,determining subcellular pH values in live cells and tissues is valuable for diagnostic purposes.In this study,we report a novel ratiometric fluorescence probe 1H-pyrazole-3-carboxylic acid,4-(benzo[d]thiazol-2-yl)-3-(2,4-dihydroxy-3-methylphenyl)-1H-pyrazole-5-carboxylicacid4-(2-benz othiazolyl)-5-(2,4-dihydroxy-3-methylphenyl),to which we will refer as ThiAKS Green(Thiazole AKyol shifting green),that is pH sensitive.The results presented here show that the probe can penetrate the celi membrane in iess than 30minutes and does not show any detectable toxicity.The measured color shifts up on pH change are linear and most significant around physiological pH(pKa=7.45),thus making this probe suitable for live-cell imaging and intracellular pH measurements.During the long-incubation periods following the application of the probe and the fluorescent microscopy measurements,it shows stable properties and is easy to detect in live cells.In conclusion,the results suggest that ThiAKS Green can be used to obtain precise information on the H+distribution at various compartments of the live cells.