Ratiometric Fluorescence Changes Research Articles

Design, synthesis and structural optimization of two click modified butterfly molecules: Aggregation induced ratiometric fluorescence change and ICT associated hydrogen bonding effect in solvatochromic analysis

Two click modified butterfly molecules are designed and synthesized having presence and absence of the aggregative moiety to differ between aggregation induced ratiometric emission changes via excimer formation and ICT associated hydrogen bonding effect. These two distinct phenomena can be successfully employed in solvatochromic analysis. This is also supported by the theoretical study through the structural variation of the two butterfly molecules.

A 1,8 naphthalimide anchor rhodamine B based FRET probe for ratiometric detection of Cr3+ion in living cells

A 2-(1,3-dioxo-1H-benzo[de]isoquinolin-2(3H)-yl)acetaldehydeanchored rhodamine B based probe, RDNAP detects Cr3+ ion by fluorescence resonance energy transfer (FRET) process in aqueous buffered acetonitrile media (7:3, v/v). Conversely, conjugation of 2-(1,3-dioxo-6-(piperidin-1-yl)-1H-benzo[de]isoquinolin-2(3H)-yl)acetaldehyde with rhodamine B provides another probe, RDNAP-PY that undergoes Cr3+assisted ratiometric fluorescence and colorimetric change in the same media. RDNAP-PY provides higher FRET efficiency and detects as low as 1.81×10−6 M Cr3+with an association constant, 15.9 × 104 M−1. Other common ions do not interfere. RDNAP-PY efficiently images intracellular Cr3+ in live Hep3B, MCF-7, HeLa, SiHa and HEK 293T cells under fluorescence microscope in a ratiometric and time dependent manner. 1H NMR titration and DFT studies strongly support experimental findings.

Ratiometric fluorescence detection of Cu(II) with a keto-dipicolylamine ligand: A mechanistic implication

Cu(II) affects our environment and living systems to various aspects, demanding its detection and quantification methods. Fluorescent detection has its own advantages, and many fluorescent sensing systems are known. As Cu(II) quenches fluorescence, a key challenge in developing fluorescent sensors is to induce fluorescence signal enhancement rather than quenching. A further challenge is to develop probes that provide ratiometric fluorescence changes at two different wavelengths. We have developed such a ratiometric sensing system for Cu(II), which is an acedan-derived dipicolylamine ligand. The probe responded to Cu(II) with a large emission wavelength shift (104 nm) from green to blue in aqueous buffer at pH 7.4; the response was specific to Cu(II) among various other metal ions. The probe was also highly sensitive (LOD = 89 nM), and thus used to detect trace amounts of Cu(II) ions in nearby river and sea water samples. Also, the probe enabled us to image intracellular Cu(II) ions through ratiometric two-photon microscopic imaging. We performed fluorescence titrations toward Cu(II) and Cu(I) at pH 7.4 and 9.0, respectively, and computational calculations on plausible metal complex intermediates, which provided insights on the sensing mechanism to propose that it involves Cu(II)-promoted enolization and subsequent reduction of Cu(II) to Cu(I). The mechanistic implication would guide us to develop other types of probes and also to re-consider the sensing mechanism involved in the known probes that involve the intramolecular charge-transfer upon metal binding.

A benzocoumarin based two-photon fluorescent probe for ratiometric detection of bisulfite

Bisulfite, an equilibrium species with sulfite, is generated from endogenous sulfur dioxide in cell from biothiols. At its elevated level, bisulfite can cause several physiological disorder and diseases. To study such “bisulfite biology” in cell and in tissue, a two-photon fluorescent probe with ratiometric imaging capability is in great demand. To this end, we investigated an aryl aldehyde-type probe derived from a dipolar benzocoumarin dye. The probe sensed bisulfite through formation of the corresponding aldehyde–bisulfite adduct in aqueous buffer at pH 7.4, with excellent selectivity over other biologically relevant species and with well-resolved ratiometric fluorescence changes from 625 nm to 552 nm. The high sensitivity (LOD = 0.08 μM) and reactivity (within 30 s) of the probe towards bisulfite enabled us to quantify an endogenous bisulfite level present in human serum. The promising in vitro ratiometric behavior, however, was deteriorated in the cellular environment, owing to large red-edge and blue-shift effects, observed for both the probe and its bisulfite adduct in cell, which occurred into the unfavorable direction. Thus the cellular imaging with the probe was confined to observe the bisulfite level changes, using one-photon as well as two-photon microscopy.

Ratiometric Indicator Based on Vibration-Induced Emission for in Situ and Real-Time Monitoring of Gelation Processes

Monitoring specific processes such as gelation in a ratiometric and visual manner is of scientific value and has practical implications but remains challenging. Herein, an innovative fluorescent low-molecular-weight gelator (DPAC-CHOL) capable of revealing and self-revealing the gelation processes in situ and in real time via the ratiometric fluorescence change from orange-red to blue has been developed. By virtue of its vibration-induced emission attribute, the gelation point, critical gelation concentration, and the internal stiffness of the gel networks of DPAC-CHOL and other gelation systems could be facilely evaluated in a ratiometric and naked-eye-observable fashion. Noteworthily, the DPAC-CHOL-doped gelation system Ph-CHOL can quantitatively identify the environmental temperature in a daily-concerned range (i.e., 20-55 °C). This work not only provides a versatile advanced material but also opens up a new avenue for the investigation of gelation systems.

An efficient fluorescent probe for rapid sensing of different concentration ranges of cysteine with two-stage ratiometric signals

A diketopyrrolopyrrole-based fluorescent probe (DPP-AC) for rapid sensing of different concentration ranges of cysteine (Cys) has been designed and synthesized, where acrylate group and α,β-unsaturated ketone moiety on DPP-AC are employed as the high and low sensitivity sites, respectively. On the basis of proposed strategy, probe DPP-AC showed ratiometric fluorescent change from 605 nm to 578 nm in presence of low concentration of Cys because of the conjugate addition-cyclization-elimination sequence reaction of acrylate group of DPP-AC with Cys. The addition of excess Cys caused second stage of ratiometric fluorescent change from 578 nm to 560 nm, which due to the Michael addition reaction between α,β-unsaturated ketone of DPP-AC and Cys. Moreover, different concentration ranges of cysteine detection can be completed in 6 min at room temperature. The limit of detection (LOD) was found to be 0.18 μM and 2.9 μM in less and excess Cys ranges, respectively. Furthermore, probe DPP-AC possessed highly selective property to differentiate Cys over glutathione and homocysteine. DPP-AC was also successfully used in cell imaging.

Readily prepared iminocoumarin for rapid, colorimetric and ratiometric fluorescent detection of phosgene

In this paper, a new colorimetric and ratiometric fluorescent probe for the rapid detection of phosgene is reported. This probe is based on a readily prepared and highly fluorescent iminocoumarin, which reacts rapidly with phosgene to form a cyclic carbamate product to produce, distinctive colorimetric and ratiometric fluorescent signal changes. The detection of phosgene with this probe is fast (complete within 2 min), highly selective and sensitive with a detection limit of 27 nM in solution. Moreover, this probe can be used to prepare easy-to-use paper test strips for convenient visual and fluorescent detection of phosgene gas even at a concentration of 0.1 mg/L. Overall, this work provides a very promising dual colorimetric and ratiometric fluorescent probe for rapid and sensitive detection of phosgene both in solution and in the gas phase.

Two colorimetric and ratiometric fluorescence probes for hydrogen sulfide based on AIE strategy of α–cyanostilbenes

Aggregation-induced emission (AIE) active fluorescent probes have attracted great potential in biological sensors. In this paper two cyanostilbene based fluorescence chemoprobe Cya–NO2 (1) and Cya–N3 (2) were developed and evaluated for the selective and sensitive detection of hydrogen sulfide (H2S). Both of these probes behave aggression-induced emission (AIE) activity which fluoresces in the red region with a large Stokes shift. They exhibit rapid response to H2S with enormous colorimetric and ratiometric fluorescent changes. They are readily employed for assessing intracellular H2S levels.

Thermo-Responsive Fluorescent Polymers with Diverse LCSTs for Ratiometric Temperature Sensing through FRET.

Temperature is a significant parameter to regulate biological reactions and functions inside cells. Sensing the intracellular temperature with a competent method is necessary to understand life science. In this work, an energy-transfer polymeric thermometer was designed for temperature sensing. The thermometer was prepared from two thermo-responsive polymers with different lower critical solution temperatures (LCSTs) of 31.1 °C and 48.6 °C, coupling with blue and red fluorescent molecules, respectively, developed for ratiometric temperature sensing based on the Förster resonance energy transfer (FRET) mechanism. The polymers were synthesized from two monomers, N-isopropylacrylamide (NIPA) and N-isopropylmethacrylamide (NIPmA), which provided different temperature responses. The fluorescent intensity of each polymer (peaked at 436 and 628 nm, respectively) decreased upon the heating of the polymer aqueous solution. While these two polymer aqueous solutions were mixed, the fluorescent intensity decrease at 436 nm and substantial fluorescence enhancement at 628 nm was observed with the increasing temperature due to FRET effect. The cell imaging of HeLa cells by these thermo-responsive polymers was explored. The difference of LCSTs resulting in ratiometric fluorescence change would have a potential impact on the various biomedical applications.

Chiral Recognition of Anions by Fluorescence Tetraamide-Based Receptors Bearing Hydroxy Groups from l-Serine and l-Threonine Residues

Abstract Chiral recognition abilities of tetraamide-based receptors 1 and 2 bearing l-serine and l-threonine as recognition sites, respectively, and terminal pyrenyl groups as signaling units for enantiomers of biologically important N-acetyl amino acid tetrabutylammonium salts were studied in acetonitrile. The receptors showed ratiometric fluorescence changes upon the addition of chiral guest anions. The binding constants for amino acid derivatives were in the 104–105 mol−1 dm3 range. The chiral discrimination abilities (K11,D/K11,L) of 1 and 2 were significantly large, for instance K11,D/K11,L for Ac-Leu-O− were found to be 3.9 and 4.6, respectively. The complex structures were evaluated by 1H NMR titrations and DFT calculations implying that the effective hydrogen bond formations by six N-H and O-H groups and a CH-π interaction of the acetyl group of d-enantiomer with a terminal pyrenyl group of the receptor.

Cyclization of chalcone enables ratiometric fluorescence determination of hydrazine with a high selectivity

Precise determination of hydrazine has gained a great importance for the environmental ecology and health risk assessment owing to the significant biotoxicity of hydrazine. However, most existing fluorescent hydrazine probes, whose selectivity relies on the nucleophilicity of one −NH2 group on hydrazine, cannot effectively discriminate hydrazine from other amine species, especially for hydroxylamine. In this work, we develop a simple fluorescent probe (TAPHP) for hydrazine detection based on a chemoselective hydrazine-induced chalcone cyclization. The probe responds specifically and quantitatively to hydrazine with a discernible ratiometric fluorescence change. Notably, the newly developed probe TAPHP can be successfully applied for hydrazine imaging in living cells and zebrafish embryos. This finding offers a straightforward strategy to achieve the high selectivity towards hydrazine, and may enlightening further development of hydrazine probes.

A novel phthalimide-rhodol-based ESIPT-FRET system for rapid colorimetric and ratiometric fluorescent detection of palladium

In this paper, a new colorimetric and ratiometric fluorescent probe was developed for rapid detection of palladium in aqueous solution under mild conditions. This probe is based on a novel phthalimide-rhodol dyad, which has a unique ESIPT-FRET mechanism to give the desired ratiometric fluorescent signal changes. Optical sensing studies showed that this probe not only has high selectivity and sensitivity for palladium with a low detection limit of 31 nM, but also exhibits rapid and distinct colorimetric and ratiometric fluorescent signal changes with a large pseudo Stokes shift. In addition, the probe was successfully used for fluorescent imaging of palladium in living cells. Overall, this work provided a new ESIPT-FRET platform for development of ratiometric probes and a new attractive colorimetric and ratiometric fluorescent probe for detection of palladium.

An ESIPT based fluorescence probe for ratiometric monitoring of nitric oxide

Development of simple and selective fluorescence probes for the detection of nitric oxide (NO) is of great important because of the key roles this gasotransmitter plays in various physiological and pathological processes. Although a large number of fluorescence probes for NO have been developed thus far, only a few display ratiometric fluorescence changes. In this study, an excited-state intramolecular proton transfer (ESIPT) fluorophore based, ratiometric fluorescence probe for NO was developed. The probe shows good selectivity and sensitivity for NO over other relevant analytes. Furthermore, the probe was applied to imaging NO in living cells.

Fast and Selective Two-Stage Ratiometric Fluorescent Probes for Imaging of Glutathione in Living Cells.

Two fluorescent, m-nitrophenol-substituted difluoroboron dipyrromethene dyes have been designed by nucleophilic substitution reaction of 3,5-dichloro-4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY). Nonsymmetric and symmetric probes, that is. BODIPY 1 (with one nitrophenol group at the position 3) and BODIPY 2 (with two nitrophenol groups at the positions 3 and 5) were applied to ratiometric fluorescent glutathione detection. The detection is based on the two-step nucleophilic aromatic substitution of the nitrophenol groups of the probes by glutathione in buffer solution containing CTAB. In the first stage, probe 1 showed ratiometric fluorescent color change from green (λem = 530 nm) to yellow (λem = 561 nm) because of monosubstitution with glutathione (I561nm/I530nm). Addition of excess glutathione caused the second stage of ratiometric fluorescent color change from yellow to reddish orange (λem = 596 nm, I596nm/I561nm) due to disubstitution with glutathione. Therefore, different concentration ranges of glutathione (from less to excess) could be rapidly detected by the two-stage ratiometric fluorescent probe 1 in 5 min. While, probe 2 shows single-stage ratiometric fluorescent detection to GSH (from green to reddish orange, I596nm/I535nm). Probes 1 and 2 exhibit excellent properties with sensitive, specific colorimetric response and ratiometric fluorescent response to glutathione over other sulfur nucleophiles. Application to cellular ratiometric fluorescence imaging indicated that the probes were highly responsive to intracellular glutathione.

Two-stage ratiometric fluorescent responsive probe for rapid glutathione detection based on BODIPY thiol-halogen nucleophilic mono- or disubstitution

Abstract 3,5-dichloro-8-phenyl-4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BOD-2Cl) (1) as a classical fluorescent dye was synthesized for the purpose of functionalization of BODIPY dye. Herein, it was applied for the purpose of achieving two-stage ratiometric fluorescent detection of glutathione based on the two-step thiol-halogen substitution reaction with the sulfhydryl group of glutathione at the 3 (mono-substitution) and 3,5-position (disubstitution) of 1 in CTAB micelles. The first stage induced fluorescent color change from green (λem = 530 nm) to yellow (λem = 562 nm) (I562nm/I530nm, mono-substitution), excess addition of glutathione caused the second stage fluorescent color change from yellow to red (λem = 597 nm) (I597nm/I562nm, disubstitution). It exhibits excellent properties with specific colorimetric and ratiometric fluorescent change to glutathione over cysteine and homocysteine. Further application to cellular ratiometric fluorescence imaging indicated that the probe was highly responsive to the glutathione in cells.

Drug-Porous Silicon Dual Luminescent System for Monitoring and Inhibition of Wound Infection.

Wound monitoring and curing is of great importance in biomedical research. This work created a smart bandage that can simultaneously monitor and inhibit wound infection. The main components of the smart bandage are luminescent porous silicon (LuPSi) particles loaded with ciprofloxacin (CIP). This dual luminescent system can undergo accelerated fluorescent color change from red to blue upon the stimulation of reactive oxygen species (ROS) and elevated pH, which are main biomarkers in the infected wound. The mechanism behind the chemical-triggered fluorescent color change was studied in detail. In vitro experiment showed that the ratiometric fluorescent intensity (IRed/IBlue) of CIP-LuPSi particles decreased from 10 to 0.03 at pH 7.5 after 24 h, while the value deceased from 10 to 2.15 at pH 7.0. Strong correlation can be also found between the IRed/IBlue value and ROS concentration ranging from 0.1 to 10 mM. In addition, the oxidation of LuPSi also simultaneously triggered the release of CIP molecules, which exhibited bacterial inhibition activity. Therefore, the ratiometric fluorescent intensity change at red and blue channels can indicate not only the wound infection status but also the release of antibiotics. In vivo test proved that the smart bandage could distinguish infected wounds from acute wounds, just relying on the naked eyes or a cell phone camera. On the basis of the Si nanotechnology established in this work, theranostic wound care will be realized in future.

A novel ratiometric fluorescent probe for selective detection of Hg2+, Cr3+ and Al3+ and its bioimaging application in living cells

A novel rhodamine-benzothiazole fluorescent probe L was designed and synthesized which can be selective detection of three kinds of metal ions (Hg2+, Cr3+ and Al3+), through the mechanism of fluorescence resonance energy transfer (FRET). This probe L shows good sensitivity towards Hg2+, Cr3+ and Al3+ even at the sub-micromolar levels, which exhibited ratiometric fluorescence change from colorless to pink in aqueous media in a wide pH range of 5–10. Interestingly, the Job’s plot investigation suggested that L bounding to Hg2+ or Al3+ with a simple 1:1 mode and a 2:1 mode to Cr3+ display different binding modes. Furthermore, the potential utility for biological applications was performed by fluorescence microscopic imaging in live cells. The results indicated that fluorescence probe L was a hopeful candidate for applications in the cell-imaging and safety inspection.

The influences of different substituents on spectral properties of rhodamine B based chemosensors for mercury ion and application in EC109 cells

Six rhodamine-based “turn-on” fluorescence chemosensors (L1–L6) with different substituents for mercury (Hg2+) were readily synthesized and investigated; they displayed high selectivity and chelation enhanced ratiometric fluorescence change and colorimetric change with Hg2+ among the metal ions examined. Based on UV and fluorescence spectral data, the effects of different substituents on spectral properties of the probes were presented and discussed. The detection limit of Hg2+ to probe L1 was as low as 50 nmol/L because of its electron-donating group. Theoretical calculation also supported the process of reaction. Confocal laser scanning microscopy experiments showed that probe could be used to detect Hg2+ in living cells.

Ratiometric sensing of Fe3+ through PET-CHEF-FRET processes: Live cell imaging, speciation and DFT studies

4-Hydroxy-5-isopropyl-2-methylisophthalaldehyde anchored rhodamine B derivative, RDDFT experiences Fe3+ assisted inhibition of photoinduced electron transfer (PET), chelation-enhanced fluorescence (CHEF) and fluorescence resonance energy transfer (FRET) process in aqueous buffered acetonitrile media. RDDFT is an excellent colorimetric Fe3+ probe that undergoes ratiometric fluorescence change to recognize and determine traces of Fe3+ in presence of Fe2+ in real sample, thus allowing speciation studies of iron. It detects as low as 2×10−8M Fe3+ with an association constant, 3.7025×106M−1. Common ions do not show any significant interference in the detection of Fe3+ ion. RDDFT efficiently images intracellular Fe3+ in HeLa cells under fluorescence microscope. DFT studies strongly support experimental findings.

Colorimetric and ratiometric fluorescent detection of carbon monoxide in air, aqueous solution, and living cells by a naphthalimide-based probe

Carbon monoxide (CO), a highly toxic gas, is now well known as an important gasotransmitter in living systems. Accordingly, development of fluorescent probes for CO is of great significance. However, fluorescent detection of CO in living systems is challenging due to the lack of effective probes, and particularly, ratiometric fluorescent probes for CO have not yet been reported. In this article, a readily available colorimetric and ratiometric fluorescent probe system for CO was reported. This probe system shows excellent sensing properties for CO including rapid response, high selectivity and sensitivity with a low detection limit (58nM), and capable of giving distinct colorimetric and ratiometric fluorescent signal changes for CO in aqueous solution under mild conditions. In addition, this probe system has low cytotoxicity and can be used to ratiometrically detect CO in living cells. Furthermore, a very convenient paper test strip system can be developed with this probe for visual detection of CO gas. Overall, this work provided a very promising probe for colorimetric and ratiometric fluorescent detection of CO in air, aqueous solution, and living cells.