A Rhodamine-based fluorescent sensor for chromium ions and its application in bioimaging

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 novel rhodamine-based turn-on probe for fluorescent detection of Au3+ and colorimetric detection of Cu2+

In this work, we design and synthesize the novel probe RC through introduction the 1-aza-4,13-dithia-15-crown-5 ring into the structure of rhodamine 6G hydrazide, where the N atom of crown ring is responsible for quenching of rhodamine fluorescence. The compound obtained behaves as multifunctional cation sensor providing selective fluorescent response to Au³⁺ and selective colorimetric response to Cu²⁺ ions in aqueous acetonitrile (1/1, v/v) at pH 7.0. The use of 10^?5?M RC solution allowed reliable determination of target cations in the presence of a wide range of environmentally relevant ions with detection limits of 2?×?10^?6?M and 5?×?10^?7?M for gold and copper, respectively.     

A selective turn-on fluorescent sensor for Fe and application to bioimaging

A novel compound FD1 was demonstrated as a turn-on fluorescent sensor for imaging of iron(III) ion in biological samples. Based on the spirolactam (nonfluorescence) to ring-open amide (fluorescence) equilibrium, FD1 exhibited high selectivity and sensitivity for Fe³⁺ over other metal ions. Moreover, fluorescent microscopy experiments further established that FD1 could be used for sensing Fe³⁺ within living cells.     

A naked-eye rhodamine-based fluorescent probe for Fe(III) and its application in living cells

A naked-eye turn-on fluorescent Fe³⁺ probe (RQ6) was developed by linking a new conjugated quinoline fluorescent group to the rhodamine platform. The probe can detect Fe³⁺ with high selectivity over other metal ions. Bioimaging studies indicated that RQ6 was cell permeable and suitable for detecting Fe³⁺ in the living cells by confocal microscopy.     

一种检测肼的纳米粒子探针及其生物成像应用

肼是一种广泛使用的化工原料,但它也是一种有毒化学品,对人类健康和环境安全有着严重威胁.因此,开发一种方便、快速检测肼的方法具有重要的意义.本文制备了一种芘甲醛纳米粒子探针,其能和肼快速反应,从而使探针的荧光信号发生变化,实现对肼的荧光检测.该探针检测肼具有高选择性和灵敏度,并成功地应用于HeLa细胞和斑马鱼中肼的成像.     

Highly sensitive and selective reversible sensor for the detection of Cr

A new fluorescent sensor capable of sensing Cr³⁺ has been synthesized. Complexing with Cr³⁺ triggers the formation of a highly fluorescent ring-open form which is pink in color. The sensor shows extremely high fluorescence enhancement upon complexation with Cr³⁺ and it can be used as a ‘naked eye’ sensor. Binding of Cr³⁺ was found to be reversible as the pink color disappears with excess EDTA.     

A new rhodamine B-based lysosomal pH fluorescent indicator

We designed and synthesized a new pH fluorescent probe, RCE, based on structural changes of rhodamine dye at different pH values. The probe exhibits high selectivity, high sensitivity and quick response to acidic pH, as well as low cytotoxicity, excellent photostability, reversibility and cell membrane permeability. Fluorescence intensity at 584 nm was increased more than 150-fold within pH range 7.51–3.53. This probe has pK_a value 4.71, which is valuable for studying acidic organelles. Because of its long absorption and emission wavelengths, RCE can avoid associated cell damage. The probe can selectively stain lysosomes and monitor lysosomal pH changes in living cells.     

Development of a novel fluorescent sensor to detect a specific range of pH

A novel fluorescent sensor for monitoring the change of pH was developed, based on a structure containing two hydroxyl groups that are sequentially deprotonated as the pH is increased: the first deprotonation increases the fluorescence intensity and the second decreases it. Compared with most reported pH sensors that can detect only whether or not the pH is below or above a specific value, our sensor could detect a specific range of pH (centered on pH 8–9) that should be useful for the study of biological microenvironment.     

Synthesis and application of rhodamine-based fluorescent probe dyes with spacer linker arm

When rhodamine-based fluorescent probe dyes are used to track target molecules they always perturb the behavior of target molecules because of steric hindrance effect. In order to minimize potential steric problems, a kind of rhodamine-based fluorescent probe dye with spacer linker arm was designed and synthesized and its application in immunofluorescence histochemistry was investigated.     

Naphthalimide-modified near-infrared cyanine dye with a large stokes shift and its application in bioimaging

A naphthalimide-modifi ed near-infrared cyanine dye (emission at 785 nm) with a large Stokes shift (up to 165 nm) has been synthesized and had favorable lysosome-targeting property.     

A new rhodamine-based dual chemosensor for Al and Cu

A new rhodamine B derivative bearing a hydrazone group has been designed and prepared. The synthesized colorimetric and fluorescent molecular chemosensor can be used as a dual probe, selectively detecting Al³⁺ and Cu²⁺ in acetonitrile solution by monitoring changes in the absorption and fluorescence spectral patterns. The results show that Al³⁺ ions can induce a greater fluorescence enhancement, while the addition of Cu²⁺ ions induces a strong UV–vis absorption enhancement with weak fluorescence. The limits of detection of Cu²⁺ and Al³⁺ were estimated to be 2.9 × 10⁻⁷ M and 8.3 × 10⁻⁹ M, respectively.     

A pyridoxal-based chemosensor for visual detection of copper ion and its application in bioimaging

A pyridoxal-based chemosensor was synthesized by reacting hydrazine hydrate and pyridoxal hydrochloride in ethanol and characterized by NMR and ESI-MS.The optical properties of the compound were investigated in a methanol:HEPES solution.The compound displayed selectivity for Cu2+,as evidenced by a colorless to yellow color change,which was characterized using UV–vis spectroscopy.The fluorescence of the compound can be quenched only by Cu2+,accompanying by a color change from blue to colorless.Furthermore,it can be used in bioimaging.     

Development of a colorimetric microfluidic pH sensor for autonomous seawater measurements

High quality carbonate chemistry measurements are required in order to fully understand the dynamics of the oceanic carbonate system. Seawater pH data with good spatial and temporal coverage are particularly critical to apprehend ocean acidification phenomena and their consequences. There is a growing need for autonomous in situ instruments that measure pH on remote platforms. Our aim is to develop an accurate and precise autonomous in situ pH sensor for long term deployment on remote platforms. The widely used spectrophotometric pH technique is capable of the required high-quality measurements. We report a key step towards the miniaturization of a colorimetric pH sensor with the successful implementation of a simple microfluidic design with low reagent consumption. The system is particularly adapted to shipboard deployment: high quality data was obtained over a period of more than a month during a shipboard deployment in northwest European shelf waters, and less than 30 mL of indicator was consumed. The system featured a short term precision of 0.001 pH (n = 20) and an accuracy within the range of a certified Tris buffer (0.004 pH). The quality of the pH system measurements have been checked using various approaches: measurements of certified Tris buffer, measurement of certified seawater for DIC and TA, comparison of measured pH against calculated pH from pCO₂, DIC and TA during the cruise in northwest European shelf waters. All showed that our measurements were of high quality. The measurements were made close to in situ temperature (+0.2 ?C) in a sampling chamber which had a continuous flow of the ship’s underway seawater supply. The optical set up was robust and relatively small due to the use of an USB mini-spectrometer, a custom made polymeric flow cell and an LED light source. The use of a three wavelength LED with detection that integrated power across the whole of each LED output spectrum indicated that low wavelength resolution detectors can be used instead of the current USB mini spectrophotometer. Artefacts due to the polychromatic light source and inhomogeneity in the absorption cell are shown to have a negligible impact on the data quality. The next step in the miniaturization of the sensor will be the incorporation of a photodiode as detector to replace the spectrophotometer.     

Synthesis and bioimaging application of red-emissive carbon dots

Fluorescent red-emissive carbon dots (RCDs) were synthesized using the solvothermal method with citric acid as a carbon source, N,N-dimethylformamide as a nitrogen source, and formamide as a solvent. The as-synthesized RCDs show red fluorescence in an aqueous solution and have an excellent stability towards photobleaching as well as extremely low cytotoxicity and are successfully used for cell and zebrafish imaging. The results indicate that RCDs have potential applications in both in vitro and in vivo bioimaging.     

A new Vilsmeier-type reaction for one-pot synthesis of pH sensitive fluorescent cyanine dyes

A new Vilsmeier-type reaction is suggested for the synthesis of novel indocarbocyanine pH sensors, which are fluorescent when protonated but nonfluorescent upon proton abstraction. These sensors show significant ratiometric UV-visible as well as fluorescence spectral changes upon subtle variation of pHs with pK_a values near neutral.     

Synthesis and properties of three novel rhodamine-based fluorescent sensors for Hg2+

Three novel rhodamine-based Hg~(2+) fluorescent sensors were designed and synthesized. The sensors could work in semi-aqueous solutions with nearly neutral p H and showed high selectivity and sensitivity to Hg~(2+) with remarkable fluorescence enhancement. For these three sensors, the linear working range broadened(0–80, 0–100 and 0–140 μmol/L, respectively) and the sensitivity increased(7.7, 15.5 and 17.6 folds of the fluorescence enhancement and 512, 66.2 and 37.6 ppb of the detection limit) with the rising of the thiourea-unit numbers. Furthermore the sensors exhibited excellent interference immunity to multiple environmentally and biologically relevant metal ions. Pond and tap water assay showed good practicability of the sensors. The number of the bound Hg~(2+) equaling to that of the thiourea units and the irreversible recognition process implied a new interaction way between Hg~(2+) and the sensor.     

Design and preparation of a novel fluorescent naphthalimide derivative supramolecular self-assembly system and its bioimaging application

ABSTRACT

A novel fluorescent naphthalimide derivative gelator (N-18) was designed and characterised which could form a stable gel in 1,4-dioxane/H₂O (2/1, v/v), methyl sulfoxide (DMSO), ethanol/H₂O (4/1, v/v), acetone/H₂O (2/1, v/v) and methanol. The self-assembly process of molecule N-18 in the five solvents was carefully investigated by the field emission scanning electron microscope, UV-vis absorption spectra, fluorescence emission spectra, fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD) and water contact angle experiments. Different structures from microbelts to helical nanofibers were formed in the self-assembly process. Hydrogen bonding and π–π stacking interaction were the mainly driving forces for the formation of gel. At the same time, the hydrophobic surface with the contact angles of 133°–142° was observed on the xerogel films N-18 from the above five solvents. Interestingly, molecule N-18 could be applied in bioimaging in a living cell.     

1,8-Naphthalimide-based colorimetric and fluorescent sensor for recognition of GMP,TMP, and UMP and its application in in vivo imaging

In this study, a series of 1,8-naphthalimide-based analogs were developed for fluorescence imaging of nucleotides in Caenorhabditis elegans. In DMSO, compound 1 proved to be an effective and selective colorimetric and fluorescent sensor for recognition of GMP, TMP, and UMP over other structurally similar nucleotides. Among all the tested nucleotides, only the addition of GMP, TMP, and UMP resulted in a fluorescence color change from blue to brown with a fluorescence enhancement of more than 600-fold, with the colorless solution turning brown. NMR spectroscopic titration, theoretical calculations, and spectral tests performed using various solvent compositions confirmed that compound 1 formed multiple hydrogen bonds with the related base groups in the nucleotide. Compound 1 demonstrated its utility as a fluorescent chemosensor for detecting GMP, TMP, and UMP in in vivo imaging of GMP, TMP, and UMP in C. elegans.     

Smart thermometer style sensor with volume readout and visualization for pH detection

A novel visual volume-type hydrogel sensor like thermometer for pH response was developed. The multifunctional stimuli-responsive fluorescent hydrogel was fabricated by employing 5, 6-dicarboxylic fluorescein crosslinked partially ammoniated polyacrylamide (PAM). The polymer hydrogel was characterized with fluorescent inverted microscope (FIM) and scanning electron microscope (SEM), as well as N₂ adsorption–desorption analysis. The polymer hydrogel emitted fluorescence and exhibited volume phase transition (VPT) in response to pH in aqueous solution. The intelligent response hydrogel was put into an elaborately altered shower-like pipette with uniform holes in which the water can pass through without the swelling hydrogel. A visual thermometer style hydrogel sensor combination of chemical reaction, separation and detection was designed. It was accurately measure the volume of hydrogel instead of the pH value when response to different pH solution by reading the graduation with naked eye. Therefore, the challenge for direct measurement of hydrogel volume was overcome. Meanwhile, a scale bar was also designed to indicate pH according to the volume. We can directly read the pH from the bar, similar to a thermometer in daily life. The volume-type sensor paves the way for VPT hydrogel sensors with convenience, visualization, low-cost, portable, smartness and ease of operation.     

A fluorometric and mitochondrion-targetable probe for rapid,naked-eye test of hypochlorite in real samples

A colorimetric, fluorometric and mitochondrion-targetable probe (Rh-ClO) based on rhodamine B fluorophore and thiophene-2-carbohydrazide has been unveiled and successfully utilized for ClO^- detection in water samples and HeLa cells.