Rhodamine-based Fluorescent Probe Research Articles

A rhodamine-based fluorescent probe used to determine nitroxyl (HNO) in lysosomes

The reactive nitrogen species (RNS) in lysosomes play a major role during the regulation of lysosomal microenvironment. Nitroxyl (HNO) belongs to active nitrogen species (RNS) and is becoming a potential diagnostic and therapeutic biomarker. However, the complex synthesis routes of HNO in biosystem always hinder the exact determination of HNO in living cells. Here, a rhodamine-based fluorescent probe used to determine nitroxyl (HNO) in lysosomes was constructed and synthesized. 2-(Diphenylphosphino)benzoate was utilized as the sensing unit for HNO and morpholine was chose as the targeting group for lysosome. Before the addition of HNO, the probe displayed a spirolactone structure and almost no fluorescence was found. After the addition of HNO, the probe existed as a conjugated xanthene form and an intense green fluorescence was observed. The fluorescent probe possessed fast response (3 min) and high selectivity for HNO. Furthermore, fluorescence intensity of the probe linearly related with the HNO concentration in the range of 6.0 × 10−8 to 6.0 × 10−5 mol L−1. The detection limit was found to be 1.87 × 10−8 mol L−1 for HNO. Moreover, the probe could selectively targeted lysosome with excellent biocompatibility and had been effectually utilized to recognize exogenous HNO in A549 cells.

Two new rhodamine-based fluorescent probes with thiophen/selenophene acrylate group for selective detection of Cys in living cells

Cysteine (Cys), one of the biological thiols, has long been an important sensing target. In this work, two new rhodamine-based fluorescent probes with thiophen/selenophene acrylate group (Rh–S and Rh–Se) have been obtained and fully characterized. Their sensing behaviors have been researched by UV–Vis absorption and fluorescence spectra, which display high sensitivity and good selectivity for the detection of Cys with low detection limit (0.268/0.270 μM) and fast response time (30/40 min), and exhibit a “turn on” response toward Cys. The possible sensing mechanism has been proposed and confirmed by HRMS and 1H NMR. Biological studies reveal that probe Rh–S has low cytotoxicity and good biocompatibility, thereby could be further used to determine Cys in living cells.

Development of a rhodamine-based fluorescent probe for ATP detection for potential applications in meat freshness assessment

Adenosine triphosphate (ATP) plays a vital role in physiological processes and is an essential indicator of microbial content in food. Herein, a new sensitive, rapid and water-soluble probe for ATP detection was developed. Rhodamine B and pentaethylenehexamine were employed to design and synthesise the probe rhodamine-pentaethylenehexamine (RP) for selective ATP detection. The synthesised probe RP was characterized using Fourier transform infrared, NMR and dynamic light scattering size distributions. Upon the addition of ATP, the probe exhibited a distinct change in fluorescence intensity, with fluorescence emission at 580 nm. A linear relationship was observed between fluorescence intensity and ATP concentrations at 0–50 μmol/L, with a limit of detection of 10.97 × 10−9 mol/L. The results of the zeta potential and molecular dynamics simulation demonstrated that the detection mechanism of the probe RP is associated with the electrostatic adsorption interaction between the multi-positively charged sites of RP and the negatively charged triphosphate structure of ATP. Our study provides new insights into improving charge site identification in small molecule detection. Furthermore, the successful detection of ATP on meat surfaces indicates that RP has the potential to assess meat freshness.

Rhodamine-based fluorescent probe for dynamic STED imaging of mitochondria.

Stimulated emission depletion (STED) microscopy holds tremendous potential and practical implications in the field of biomedicine. However, the weak anti-bleaching performance remains a major challenge limiting the application of STED fluorescent probes. Meanwhile, the main excitation wavelengths of most reported STED fluorescent probes were below 500 nm or above 600 nm, and few of them were between 500-600 nm. Herein, we developed a new tetraphenyl ethylene-functionalized rhodamine dye (TPERh) for mitochondrial dynamic cristae imaging that was rhodamine-based with an excitation wavelength of 560 nm. The TPERh probe exhibits excellent anti-bleaching properties and low saturating stimulated radiation power in mitochondrial STED super-resolution imaging. Given these outstanding properties, the TPERh probe was used to measure mitochondrial deformation, which has positive implications for the study of mitochondria-related diseases.

Synthesis of rhodamine-helicin fluorescent probe for colorimetric detection of Cu2+ and fluorescent recognition of Fe3+

Fluorescent probes play a crucial role in analytical chemistry and biological imaging, offering selective detection of metal ions. Herein, we present the synthesis and characterization of a novel rhodamine-based fluorescent probe, RbHC (Rhodamine B Helicin), which was obtained through the condensation of rhodamine B hydrazide and helicin in ethanol. The probe demonstrates remarkable selectivity and anti-interference capabilities towards Cu2+ and Fe3+ ions in 80% acetonitrile solution. Spectral titration analysis revealed a linear relationship between the intensity and the concentration of Cu2+/Fe3+. The formation of complex between Cu2+/Fe3+ and RbHC was confirmed to be 1:1, and it was further confirmed by ESI mass spectroscopy and DFT calculations. The coordination with Cu2+/Fe3+ caused the opening of RbHC's spirolactam ring, resulting in distinct color change and red fluorescence emissions. Moreover, RbHC exhibits high stability and water solubility under both acidic and neutral conditions, enabling its application in the imaging of plant tissues. Besides, the absorption intensity of RbHC–Cu2+ increased significantly when exposed to sunshine and 365 nm UV radiation, indicating that it might be used as a potential indicator for measuring outdoor UV intensity.

Rhodamine-based Fluorescent Probe With Quick Response and High Selectivity for Imaging Labile Ferrous Iron in Living Cells and Zebrafish.

The transition between its various oxidation states of Iron plays a crucial part in various chemical transformation of cells. Misregulation of iron can give rise to the iron-catalyzed reactive oxygen species disorder which have been linked to a variety of diseases, so it is crucial to monitor the labile iron pool in vivo for clinical diagnosis. According to iron autoxidation and hydrogen abstraction reaction, we reported a novel "off-on" fluorescent probe to response to ferrous (Fe2+) both in solutions and biological systems. The probe responds to Fe2+ with good selectivity toward competing metal ions. What's more, the probe presents significant fluorescent enhancement to Fe2+ in less than 1min, making real-time sensing in biological system possible. The applications of the probe in bioimaging revealed the changes in labile iron pool by iron autoxidation or diverse stimuli.

A rhodamine-based fluorescent probe for specific recognition of mitochondrial cysteine

Cysteine (Cys) is of great significance in biological systems and in the process of mitochondrial function. Highly selective and specificity recognizable probes for mitochondrial Cys are still in demand. In this work, a new fluorescent probe for detecting mitochondrial Cys was developed based on a rhodamine derivative. In this probe, acrylate unit was selected as group of Cys recognition and quaternized pyridinium moiety was utilized as mitochondrial targeting group. The probe showed colorless in daylight and extremely weak fluorescence in 365 nm due to its spirolactone structure when Cys did not exist. In the presence of Cys, the probe exhibited orange in daylight and produced intensely green fluorescence in 365 nm owing to the formation of the conjugated xanthene structure. The probe exhibited specific recognition for Cys. There was an excellent linear relationship between fluorescence intensity at 540 nm of the probe and the Cys concentration from 4.0 × 10-8 to 1.0 × 10-5 mol⋅L-1. And the detection limit was estimated to be 1.57 × 10-8 mol/L. Moreover, the probe was almost non-cytotoxic, possessed targeting-mitochondria ability and could sense Cys at the cellular level. The good bioimaging ability makes the probe a potential tool for studying mitochondrial Cys in biological samples.

Rhodamine-Based Cyclic Hydroxamate as Fluorescent pH Probe for Imaging of Lysosomes.

Monitoring the microenvironment within specific cellular regions is crucial for a comprehensive understanding of life events. Fluorescent probes working in different ranges of pH regions have been developed for the local imaging of different pH environments. Especially, rhodamine-based fluorescent pH probes have been of great interest due to their ON/OFF fluorescence depending on the spirolactam ring's opening/closure. By introducing the N-alkyl-hydroxamic acid instead of the alkyl amines in the spirolactam of rhodamine, we were able to tune the pH range where the ring opening and closing of the spirolactam occurs. This six-membered cyclic hydroxamate spirolactam ring of rhodamine B proved to be highly fluorescent in acidic pH environments. In addition, we could monitor pH changes of lysosomes in live cells and zebrafish.

Engineering a novel rhodamine-based fluorescent probe using host-guest interactions for reversible, selective, and sensitive detection of herbicide paraquat

Although paraquat (PQ) is one of the most extensively used herbicides worldwide, it is hazardous to the environment and the public due to its extreme toxicity towards non-target organisms especially animals and humans. Therefore, developing a detection system for selectively and sensitively detecting PQ remains a great challenge. This report demonstrates the design of a novel highly fluorescent rhodamine-based probe fabricated by rationally inserting adamantane-modified rhodamine into a host cucurbit[7]uril (CB[7]) with a host-guest interaction induced spirocyclic ring-opening process. This host-guest binary complex (1&CB[7]) had a stronger fluorescence intensity than rhodamine B, which was exploited for PQ detection. Notably, complex 1&CB[7] displayed high sensitivity toward PQ, with an excellent nanomolar limit of detection of 10 nM. It was determined that this unique detection mechanism involved a process of self-assembly, disassembly, and reassembly, thereby providing a reversible fluorescence response to PQ. With such merits, we successfully quantified and mapped PQ in actual water samples, live cells, and various agricultural products. We anticipated that the constructed complex 1&CB[7] could acts as a potential alternative for PQ tracking in various applications, highlighting a new paradigm for engineering host-guest probes with spirocyclic ring-opening process for analyte detection.

Preparation of a Highly Selective “Off-On” Rhodamine-Based Fluorescent Probe for the Specific Determination of Carboxylesterase 2 and Cell Imaging

Given the important role of carboxylesterase 2 (CES2) in the metabolism of various esters, it is of significance to develop a tool to determine endogenous CES2 activity in a rapid and highly selective manner. In this work, an "off-on" rhodamine-based fluorescent probe is reported as an effective tool for CES2 activity. Based on the substrate recognition preference of CES2 (large alcohol and small acyl groups), the probe with dimethyl carbamate as the recognition group performs well in terms of selectivity and sensitivity to CES2. The fluorescence switching control of the probe for CES2 was achieved by using the spirolactone structure of rhodamine. The probe shows the fast generation of a fluorescence signal at 634 nm upon hydrolysis of CES2 with excitation at 578 nm. The results showed a linear relationship between the fluorescence intensity at 634 nm and the CES2 activity from 0 to 4 μg/mL. The probe reacts rapidly with CES2, and the reaction is stable within 40 minutes. The probe is highly selective for CES2, with a detection limit as low as 0.303 μg/mL. In addition, the probe has currently been successfully utilized to evaluate CES2 activity in living cells. Hence, this probe is anticipated to be significant in identifying endogenous CES2 activity in intricate biological settings.

A novel rhodamine-based fluorescent probe for high selectively determining cysteine in lysosomes

An essential sulfhydryl amino acid in the human body is cysteine (Cys). Its abnormal level is related to coronary heart disease, hypertension, growth retardation, sleepiness, liver injury and AIDS. At present, although many cysteine fluorescent probes have been synthesized, there are relatively few fluorescent probes for sensing cysteine in lysosomes. Therefore, based on a rhodamine derivative, we constructed a fluorescent probe with high selectivity for detecting cysteine in lysosome. The probe chose acrylate as the recognition group and morpholine as the positioning group. The probe was in spirolactone state and displayed very weak fluorescence when cysteine was absent. After adding cysteine, the conjugated xanthene structure was formed through the conversion of the closed spirolactone structure and strong green fluorescence appeared. Compared with glutathione (GSH) and homocysteine (Hcy), the probe had better selectivity to Cys. When the Cys concentration was altered from 1.0 × 10−7 to 6.0 × 10−6 mol·L−1, there was a good linear relationship between fluorescence intensity of the probe and Cys concentration. The detection limit had been evaluated to be 7.5 × 10−9 mol·L−1 for Cys. The probe can work under a wide pH range, including pH under physiological conditions. The probe also has a good effect in non-cytotoxic confocal imaging of endogenous and exogenous cysteine in A549 cells. These findings showed that the fluorescent probe synthesized in this study could be a useful tool for the detection of endogenic and exogenic cysteine.

Preparation and performance study of rhodamine B naphthylamide, a fluorescent probe, for the detection of Fe3.

Fe3+ is essential for humans, and its deficiency or excess can be harmful to human health; thus, it is crucial to detect Fe3+. Herein, a novel 1,8-naphthylimide rhodamine-based fluorescent probe (NA-RhBEA) was prepared from rhodamine B, anhydrous ethylenediamine, and 1,8-naphthoic anhydride. This fluorescent probe complexes Fe3+ with N and O on the carboxyl groups of its spironolactam structure and part of the 1,8-naphthalenedicarboxylic anhydride structure, which results in spironolactam ring-opening and fluorescence. NA-RhBEA has high selectivity for Fe3+ in ethanol/buffer solution (4 : 1, v/v), and fluorescence is detected at an excitation wavelength λEX = 500 nm, an absorption peak appears at 585 nm, and a significant color change appears. The effect of the fluorescence intensity of Fe3+ under a series of different concentration conditions was investigated, and it was concluded that the fluorescence intensity increased with increasing Fe3+ concentration in the range of 0-500 μmol, and its detection limit was 0.84 μmol L-1. In addition, we explored the detection ability of NA-RhBEA in solutions with different pH values, mixed metal ions, and different solvents, and the results showed that the fluorescent sensor also has good anti-interference properties and some practical applicability.

Rhodamine-Based Fluorescent Probe for Highly Selective Determination of Hg2.

The determination of mercuric ions (Hg2+) in environmental and biological samples has attracted the attention of researchers lately. In the present work, a novel turn-on Hg2+ fluorescent probe utilizing a rhodamine derivative had been constructed and prepared. The probe could highly sensitively and selectively sense Hg2+. In the presence of excessive Hg2+, the probe displayed about 52-fold fluorescence enhancement in 50% H2O/CH3CH2OH (pH, 7.24). In the meantime, the colorless solution of the probe turned pink upon adding Hg2+. Upon adding mercuric ions, the probe interacted with Hg2+ and formed a 1:1 coordination complex, which had been the basis for recognizing Hg2+. The probe displayed reversible dual colorimetric and fluorescence sensing of Hg2+ because rhodamine’s spirolactam ring opened upon adding Hg2+. The analytical performances of the probe for sensing Hg2+ were also studied. When the Hg2+ concentration was altered in the range of 8.0 × 10–8 to 1.0 × 10–5 mol L–1, the fluorescence intensity showed an excellent linear correlation with Hg2+ concentration. A detection limit of 3.0 × 10–8 mol L–1 had been achieved. Moreover, Hg2+ in the water environment and A549 cells could be successfully sensed by the proposed probe.

Scrutinzing the interaction of bovine serum albumin and human hemoglobin with isatin-triazole functionalized rhodamine through spectroscopic and In-silico approaches

• Spectral methods have been used to investigate the interaction of R1 with HHb and BSA. • Thermodynamic parameters suggested exothermic spontaneous binding processes involving hydrogen bonding and van der Waal interaction. • Molecular docking and molecular dynamics have been utilized to discuss the principle binding sites of proteins for R1 . • R1 proposes preferentially binding to the hydrophobic cavity in site III of proteins. A Rhodamine-based fluorescent probe R1 has been successfully utilized to detect BSA and HHb proteins via non-covalent bonding. The protein binding nature with R1 has been unravelled by the characteristic changes in absorption, emission and circular dichroism spectra that indicated their noticeable interaction. The experimental results have also shown the moderate strength between proteins and R1 from the quenching of proteins through the static quenching mechanism. The hyperchromism in the absorption band of proteins with R1 has given vital information and binding affinity values have been calculated from Stern-Volmer plots. The calculated values of the thermodynamic parameters revealed a spontaneous binding processes occurring primarily via hydrogen bonding and van der Waal interactions. Furthermore, in-silico approaches have been utilized to make a comparison and conclusion with spectroscopic results. The outcome of these studies could be useful to examine the drug-protein binding for further exploitation.

Construction of a unique fluorescent probe for rapid and highly sensitive detection of glutathione in living cells and zebrafish

A rhodamine-based fluorescent probe (Rho-GSH) was rationally designed and synthesized, using nitrobenzene as recognition group for monitoring and imaging GSH in vitro and in vivo. In the presence of GSH, Rho-GSH undergoes sequential nucleophilic substitution and spiro-ring-opening reaction, resulting the fluorescence increase of probe, which enables quantitative detection of GSH with “off-on” fluorescence. The cascade reaction also enables Rho-GSH to rapidly detect GSH (3 s). In addition, Rho-GSH exhibited outstanding selectivity in detecting GSH vs cysteine (Cys) and homocysteine (Hcy). Based on the outstanding detection performance and superior biocompatibility of Rho-GSH, it was used to visualize GSH in vitro and in vivo, demonstrating its highly selectivity for GSH detection (with respect to Cys and Hcy). Rho-GSH can help visually distinguishing cancer cells from normal cells by fluorescence imaging, demonstrating the overexpression of GSH in cancer cells. Because of the outstanding analytical capabilities of Rho-GSH for GSH detection, Rho-GSH may be useful for cancer diagnosis and clinical evaluation.

A Rhodamine-Based Fluorescent Probe for Visual Monitoring of Ph Changes in the Golgi Apparatus

A Rhodamine-Based Fluorescent Probe for Visual Monitoring of Ph Changes in the Golgi Apparatus

A rhodamine based fluorescent chemodosimeter for the selective and sensitive detection of copper (II) ions in aqueous media and living cells

A rhodamine-based fluorescent probe, integrated with phosphonate group, demonstrated highly selective and sensitive recognition towards copper (II) ions over other metal species. Operating via ring opening reaction, the probe molecule (RhP) offered extensive properties such as “turn-on” fluorescence response, naked-eye detection, low detection limit (15 nM) and fast response time (<15 s). Detection of copper (II) ions in living cells as a biological application is also successfully reported.

A new rhodamine probe with large stokes shift for Hg2+ detection and its application in real sample analysis

Mercury can cause a variety of physical diseases and even death due to its complicated biological toxicity. The detection of mercury ions is therefore of great significance. In this study, we designed a new rhodamine-based fluorescent probe Hg664 which shows a large Stokes-shift for Hg2+ detection. The probe was developed employing Hg2+-enhanced desulfurization-cyclization reaction, and demonstrated high selectivity, excellent sensitivity (LOD 1.87 ppb), and fast responsive profile (within 30 s). Besides, the probe was successfully applied for the detection of Hg2+ ions in different real water samples, and satisfactory results were obtained, indicating that the probe may be a potential method for detecting Hg2+ in the ecosystem.

Studies of the labile lead pool using a rhodamine-based fluorescent probe.

Lead is a heavy metal which has long been known to have toxic effects on the body. However, much remains to be learnt about the labile lead pool and cellular uptake of lead. We report here RPb1 that undergoes a 100-fold increase in fluorescence emission in the presence of Pb2+, and which can be applied to study the labile lead pool within cells. We demonstrate the capacity of RPb1 for investigating labile lead pool in DLD-1 cells and changes in labile lead during differentiation of K562 cells.

One-step synthesis of rhodamine-based Fe3+ fluorescent probes via Mannich reaction and its application in living cell imaging.

Four rhodamine-based fluorescent probes M1-M4 were synthesized in one step using Mannich reaction. The Mannich reaction based approach has the advantages of simplicity, good yield and excellent atomic economy. The structures were determined by 1H NMR, 13C NMR, IR and HRMS. The probe M3 as a representative compound was characterized by single-crystal X-ray analyses. The fluorescence and absorbance spectra research of the probes demonstrated that they could be used as Fe3+-selective fluorescent probes with good sensitivity, excellent linearity, and outstanding anti-interference in acetonitrile/Tris-HCl buffer solution (3:7, V/V; pH=7.4). Moreover, confocal laser scanning microscopy experiments have proven that the probe M3 was successfully used for fluorescence imaging in MCF-7 cells.