Ratio Fluorescent Probe Research Articles

A dual emission ratiometric fluorescent probe constructed based on MOF-embedded dye for sequential detection of Al3+ and PPA

The ratiometric fluorescence probe has a self-calibration system that greatly reduces interference from the external environment, it has high sensitivity and accuracy in qualitative and quantitative experiments. In this work, a novel ratio fluorescence probe (RhB@1) was constructed by enclosing Rhodamine B (RhB) in the channel of [Cd2(H2L)2(1,4-bib)2]•DMA (H2L=2-hydroxyterephthalic acid, 1,4-bib=1, 4-bis (imidazol-1-ylmethyl) benzene). The probe can display dual emission characteristics under a single excitation. Al3+ ion was detected by RhB@1. The results showed that the fluorescence of 1 in RhB@1 was increased, the fluorescence of RhB is unchanged, and limit of detection (LOD) of Al3+ is as low as 20.9nM. Interestingly, when PPA (phenylpyruvic acid) is added to the mixture of RhB@1 and Al3+, PPA competes with RhB@1 for Al3+ result in achieving continuous ratio sensing of Al3+ and PPA, and LOD of PPA is 3.21nM. More importantly, the response of RhB@1 to Al3+ in tap water and PPA in artificial urine was quantitatively determined by label recovery method. The results showed that the recovery rate were 97.706%-99.060% (Al3+) and 94.732%-98.100% (PPA). In addition, we prepared a portable test paper modified with carboxymethyl cellulose. This test paper has obvious color change when detecting Al3+ under ultraviolet light, which is easy to detect Al3+ by naked eye.

A novel high signal-to-noise ratio fluorescent probe for real-time mitochondrial viscosity detection and imaging in vitro and in vivo.

Mitochondrial viscosity serves as a critical indicator for assessing mitochondrial functionality and offers valuable insights into cellular homeostasis. Continuous, real-time monitoring of mitochondrial viscosity is indispensable for understanding and diagnosing diseases associated with these dynamic changes. In this study, we introduce a novel mitochondrial viscosity-responsive probe named "JL-JC" which is designed by using a molecular strategy, with a classic "D-π-A" molecular structure. Leveraging the distinctive twisted intramolecular charge transfer (TICT) properties of the probe, JL-JC exhibits exceptional sensitivity and a high signal-to-noise ratio, enabling precise detection of viscosity variations within its microenvironment while remaining unaffected by other factors. Upon rapid cellular uptake, JL-JC can efficiently evaluate the mitochondrial viscosity changes under diverse physiological and pathological conditions. Notably, this probe also enables viscosity imaging in zebrafish, offering insights into mitochondrial states in vivo. Our findings present JL-JC as a promising tool and potential diagnostic platform for mitochondria-related diseases.

Construction of carbon quantum dots/riboflavin fluorescent probe and its application in the detection of ciprofloxacin.

The research outlined a novel approach for creating a sensitive and efficient ratio fluorescent probe for ciprofloxacin (CIP) detection. The method used the biomass materials passionfruit shell and diethylenetriamine as carbon and nitrogen sources, respectively, to prepare blue fluorescent carbon quantum dots (b-CQDs) with an average size of 3.29 nm and a quantum yield of 19.6% by a hydrothermal method. The newly designed b-CQDs/riboflavin ratio fluorescent probe demonstrates a distinct advantage for CIP monitoring, exhibiting a marked increase in fluorescence intensity at 445 nm upon interaction with CIP, while maintaining a stable intensity at 510 nm. In the water system, the I445 nm/I510 nm ratio of the fluorescent probe showed a significant linear relationship with CIP at the concentrations of 0-250 μmol·L-1, and the probe boasts a low detection limit of 0.86 μmol·L-1. The outstanding selectivity, broad detection range, low detection limits, and high quantum yield of the b-CQDs highlight their significant potential in the development of advanced sensing probes for efficient detection of ciprofloxacin, offering promising insights for future sensor technology advancements.

Rare-earth-free up and down-conversion dual-emission carbon dots for Cu2+ sensing

In this work, up- and down-conversion dual-emission CDs without rare-earth (UD D-CDs) were synthesized using RhB and 1,4-Diaminoanthraquinone as precursors. The synthesized UD D-CDs exhibited dual emissions at 496 and 580 nm under 260 and 865 nm excitation, respectively. The fluorescence emission mechanism, including contributions from carbon nuclei, surface states, molecular states, and internal defect states, was discussed through the separation and purification of UD D-CDs. Based on the interaction between UD D-CDs and copper ions (Cu2+), a dual-mode ratio fluorescence probe was developed to detect and quantify Cu2+. The up-conversion ratio fluorescent probe shows a linear range of 0.0500–15.0 μM, with a detection limit as low as 2.76 nM. This method has been successfully applied to detecting Cu2+ in human serum and has potential applications in biochemical analysis and biological imaging. The successful preparation of up-conversion fluorescent carbon dots without rare earth elements and the ability to perform low-damage detection in high-background biological samples provide a new approach to constructing non-rare earth up-conversion probes.

A new insight into the luminescence mechanism of a FRET-ICT-based ratiometric and colorimetric pH probe

Recently, a ratio fluorescent probe molecule BP was designed and synthesized to detect pH in living cells. However, few have conducted in-depth theoretical exploration of the detailed transfer process. In this paper, the luminescence mechanisms of BP and BPH were studied with the results of geometric optimization structures and molecular orbitals at the CAM-B3LYP/TZVP computational level. It was found that a fluorescence resonance energy transfer (FRET) process occurs in the excited state of BP molecules, and the final fluorescence emission is attributed to the intramolecular charge transfer (ICT) of the acceptor styryl pyridine ring. Meanwhile, the fluorescence emission of BPH molecules is due to the ICT process caused by the local excitation process of the acceptor group protonated styryl pyridine ring itself. Therefore, this luminescence is a FRET “ON-OFF” combined ICT process, not like the FRET “OFF-ON” mechanism which the experiment suspected. Our work illustrates a specific FRET combined ICT process of probes BP and BPH from a theoretical perspective which could provide theoretical guidance for the future design of similar fluorescent probes.

Porphyrin nanoparticles-based portable smartphone platform for visual monitoring heavy metal Cr (Ⅲ) in the environment

Chromium ions exist in various valence states in the environment, and their pollution poses serious harm to social ecology and human health. The existing detection is mostly focused on Cr6+, while the detection related to Cr3+ is often overlooked. Cr3+ has a certain impact on soil, water, and the growth of animals and plants and even disrupts ecological balance. Accordingly, it is necessary to explore sensitive, convenient, and fast detection devices for Cr3+ in the environment. Here, we have designed a ratio fluorescence probe with porphyrin nanoparticles formed by block copolymers as the sensing core for ultra sensitive detection of Cr3+. The porphyrin nanoparticles can effectively bind with Cr3+ to form metal complexes, leading to ligand metal charge transfer (LMCT), which will result in a significant color change of the probe from red to blue. Furthermore, we have developed two portable fluorescence sensors for Cr3+ in soil and water, respectively. These portable sensing platforms based on designed nanoprobes and smartphones can convert the color information of fluorescent photos into digital information for real-time analysis. Thus, the method reported in this article can provide a possibility for rapid on-site and visual inspection of Cr3+ in soil and water from different regions.

Dual-emission ratio fluorescent probe based on carbon dots and copper-silver bimetallic nanoclusters for visual and fluorescent detection of ciprofloxacin

Ciprofloxacin (CIP) plays an important role in many physiological processes. Previously reported methods for CIP detection have many drawbacks and so it is crucial to develop highly sensitive methods to detect CIP. In this study, a dual-emission ratiometric fluorescent probe (SF-CQDs/CuAg NCs) of a nanocomposite of carbon quantum dots (SF-CQDs) and copper-silver bimetallic nanoclusters (CuAg NCs) was developed for sensitive and selective detection of CIP. The fluorescent signal of CuAg NCs was quenched while the fluorescence intensity of SF-CQDs was enhanced in the presence of CIP. The working principle of the fluorescent probe SF-CQDs/CuAg NCs is mainly based on the complexation of CIP with CuAg NCs to free SF-CQDs. The quenching of CuAg NCs by CIP arises from the chelation between the metal and the 1-oxo substituent and the adjacent carboxyl group of CIP. The fluorescence recovery of SF-CQDs is attributing to the release of SF-CQDs from SF-CQDs/CuAg NCs and the hydrogen bonding interaction between SF-CQDs and CIP. The ratiometric fluorescence measurement of SF-CQDs/CuAg NCs has been employed to analyze CIP with good sensitivity and selectivity. The working range of CIP is 5.0–200.0 μM and the detection limit is 3.3 μM. More importantly, the fluorescence of SF-CQDs/CuAg NCs can be detected intuitively via a smartphone which can be applied to determine CIP.

Fluorescent Paper Based on CQDs/Rhodamine B: A Ratio and Sensitive Detection Platform for On-Site Fe3+ Sensing.

Fluorescent sensors with single reading are generally subject to unpredictable disturbs from environmental and artificial factors. In order to overcome this barrier of detection reliability, a paper-based optical sensor with proportional fluorescence was established and further combined with a smartphone for visual, on-site and quantitative detection of Fe3+, which affects the color, smell and taste of water, and endangers the health of plants and animals. The ratio fluorescent probe was fabricated by rhodamine B and carbon quantum dots derived from xylan. The red fluorescence of rhodamine B was inert to Fe3+, which was referred to as background. And blue emitting carbon quantum dots functioned as signal report units, which would be quenched by Fe3+ and make the fluorescence of the ratio probe change from purple to red. The quantitative detection of Fe3+ was conducted by investigating the RGB value of fluorescent images with a smartphone. With the increase of Fe3+ concentration, the R/B (red/blue) value of the fluorescent paper gradually increased. The linear detection range was 10-180 μM, and the limit of detection was 198.2 nM. The application of ratio fluorescent paper with a smartphone provides a facile method for the rapid detection of ions.

Portable smartphone-assisted ratiometric fluorescent probe for carbimazole visualization detection

The ratio-based probe improves detection precision and accuracy by minimizing the effects of various experimental conditions. Herein, we constructed a ratio fluorescent probe (Si NPs/TGA-functionalized CdTe) using silicon nanoparticles (Si NPs) as the background signal and mercaptoacetic acid-functionalized cadmium telluride quantum dots (TGA-functionalized CdTe) as the responding unit. The interaction between Carbimazole (CBZ) and sulfhydryl groups on the surface of TGA-functionalized CdTe led to a decrease in the fluorescence intensity of the probe, and the color of the solution turned red and pink turned blue. Meanwhile, a test paper-based detection method integrated with the smartphone sensing platform was established to analyze the red, green, and blue (RGB) values in the images of Si NPs/TGA-functionalized CdTe solution before and after the addition of CBZ based on the change of hue, and an analytical model was constructed based on the R/B value and CBZ concentration, realizing rapid visual detection and analysis of CBZ. In addition, the constructed smartphone sensing platform was applied to the detection of CBZ in human urine, and the limit of detection the fluorescence analysis method and the smartphone sensing platform were 40 nM and 63 nM, with the recoveries of 96.5 %-102.7 % and 90.6 %-107.2 %, and the relative standard deviations of 2.7 %-4.1 % and 3.5 %-6.8 %, respectively. This work provides a significant improvement in the proportional sensing of CBZ in human urine and broadens the use of portable quantitative sensing devices in chemical sensing applications.

Detection of Cadmium(II) in Aquatic Products Using a Rolling-Circle Amplification-Coupled Ratio Fluorescent Probe Based on an Aptamer-Peptide Conjugate.

The existing aptamers for cadmium (Cd2+), the common toxic heavy metal contaminant in food, cannot meet the requirements for detecting Cd2+ in rapid detection methods. In previous work, we found that coupling aptamer-peptide conjugates (APCs) with peptides and aptamers can provide a less disruptive method with a significantly improved affinity. Moreover, we found that the spatial conformation of aptamers and peptides is crucial for obtaining proper affinity in APC. Therefore, we describe a simple design strategy to obtain a series of APCs with different affinities by designing peptide orientations (N-terminal, C-terminal). The best affinity was found for APC(C1-N) with a binding constant (Ka) of 2.23 × 106 M-1, indicating that the APC(C1-N) affinity was significantly increased by 829.17% over aptamer. Finally, a rolling-circle amplification (RCA)-coupled ratio fluorescence-based biosensor for Cd2+ detection was established with a detection limit of 0.0036 nM, which has great potential for practical aquatic product detection.

Cyanine based ratio fluorescent probe and its application in hypochlorite detection

Hypochlorite (ClO−), a weakly acidic reactive oxygen species, plays a crucial role in antibacterial and anti-inflammatory defense mechanisms. However, elevated levels of ClO− or disruptions in endogenous sites can lead to tissue damage and various diseases including cardiovascular disease, neuronal degeneration, and arthritis. To address this, the development of a specific fluorescent probe with a built-in self-calibration ratio mode for the analysis and biological imaging of ClO− is essential. In this study, a cyanine-based fluorescent probe (Cy-H) was designed for ratiometric fluorescent detection of ClO−, utilizing its aggregation behavior as a novel approach in this field. Upon exposure to ClO−, the phenolic hydroxyl group in probe Cy-H was oxidized into benzoquinone, leading to the formation of cyanine products that displayed a strong tendency to aggregate. As a result, the maximum emission peak of the probe shifted from 700 nm to 485 nm. Notably, a linear relationship was observed between the peak intensity ratio (I485/I700) and the concentration of hypochlorite, with a limit of detection (LOD) of 0.49 μM. Furthermore, this probe was successfully employed for imaging analysis of hypochlorite in living cells and zebrafish.

A novel Eu-MOF ratiometric fluorescent probe for visual detection of Hg2+, Cd2+ and formaldehyde

The accumulation of heavy metal ions in nature will not only lead to the further deterioration of the environment, but also directly do harm to human health. And as a gas pollutant, excessive inhalation of formaldehyde is also harmful to human health. Herein, a novel Eu-MOF was synthesized by solvothermal method using Eu3+, 2-pyridine-4-yl-3H-benzimidazole-5-carboxylic acid (HL) and 1,10-phenanthroline (phen), which can be used as a ratio fluorescent probe to detect Hg2+, Cd2+ and formaldehyde, and the limits of detection(LOD) can reach 34, 9.91 and 194 nM respectively. Among them, the LOD of Eu-MOF for Cd2+ has reached the lowest level at present. Noticeable, Eu-MOF can detect formaldehyde in both liquid and gas phases, and the response time is extremely short. In addition, Eu-MOF has been applied to trace detection of Hg2+ and Cd2+ in tap water, lake water and sea water with satisfactory recoveries (ranging from 98.10 % to 103.0 %). A program has been developed for quickly calculating the concentration of the substances to be detected by capturing the fluorescent color of the solvents under the ultraviolet light.

A Ratio Fluorescence Method Based on Dual Emissive Copper Nanoclusters for the Detection of Vanillin.

In this study, a novel double-emission fluorescence probe at 340 and 400nm was synthesized by one-pot method using phenylalanine (Phe) and ascorbic acid (AA) as stabilizing and reducing agents. It was found that the fluorescence intensity of the probe at 400nm could be controlled by controlling the temperature within a certain range, and the ratio of double-emission fluorescence probe could be further regulated. Under the optimal conditions, the fluorescence intensity at 340nm decreased significantly, while it only showed a slight decrease at 400nm, which constituted the ratio fluorescence probe. The synthesized fluorescence probe showed good linearity in the range of 0.2-32 μM, and its detection limit was 63.4 nM. Moreover, the method was successfully employed to determine VA in vanilla drink and perfumes, and corresponding results were consistent with those of HPLC.

Exploration of novel dual-emission NL-CDs/Cu–Cy–I ratio fluorescent probe for the sensitive detection of amoxicillin

A dual-emission ratio fluorescence probe (NL-CDs/Cu–Cy–I) was fabricated via an electrostatic self-assembly method.

Portable paper-based probe for on-site ratiometric fluorescence determination of total flavonol glycosides in plant extract using smartphone imaging.

A smartphone-assisted, paper-based ratio fluorescence probe is presented for the rapid, low-cost and on-site quantification of total flavonol glycosides in Ginkgo biloba extracts (GBE). The Al3+/Eu-MOF/paper-based probe utilizes lanthanide metal-organic framework (Ln-MOF) nanoparticles immobilized on Whatman filter paper along with Al3+ for detecting flavonols, which are the hydrolyzed products of flavonol glycosides. The color change of the paper-based fluorescence image from red to orange depends on the concentration of the target analyte in the sample solution. The smartphone equipped with a red, green, blue (RGB) color detector measured the fluorescence signal intensity on the paper substrate after adding flavonol. The analytical variables affecting the performance of the probe, including the addition sequence of the aluminum nitrate solution, its concentration, that of the Ln-MOF solution, the drying time of the paper probe, the reaction time and the sensitivity parameters of the mobile phone camera (ISO), were optimized. Under optimal conditions, the Al3+/Eu-MOF/paper-based probe has good linear response in the concentration range 7 ~ 80µg mL- 1 and a lower detection limit of 2.07µg mL- 1. The results obtained with the paper-based ratio fluorescence probe and smartphone combination were validated by comparing them with high-performance liquid chromatography (HPLC) measurements. This study provides a potential strategy for fabricating Al3+/Eu-MOF/paper-based probe used for total flavonol glycosides determination.

Carbon quantum dot with co-doped nitrogen and phosphorus for tazettine ratiometric fluorescent sensing

An overdose of tazettine (TZ) has toxic side effects, which makes it extremely important to rapidly and subtly determine the TZ. In this study, double-emitting, nitrogen–phosphorus co-doped carbon quantum dots (N,P-CQDs) were prepared using cis-butenedioic acid, phosphoric acid, and p-phenylenediamine. An effective inner filter effect (IFE) can occur between TZ and N,P-CQDs, resulting in their fluorescence quench. Therefore, a ratio fluorescent probe was constructed for detecting the TZ was constructed. After optimizing the experimental conditions, the quenching efficiency showed a strong linear connection with the TZ concentration in the range of 0.01–30 µmol/L, with the detection limit of 0.002 µmol/L. This method could be satisfactorily applied to detect TZ in mouse plasma samples.

Self-Calibrating Lanthanide Infinite Coordination Polymer Constructs Fluorescent Probes: A Sensitive Approach for Early Diagnosis of Hepatocellular Carcinoma and Environmental Analysis.

The development of a self-calibrating ratio fluorescence probe without the need for additional substrates is a major advancement in biosensing. In this study, at room temperature, a self-calibrating infinite coordination polymer (SSA-Tb-ATP ICPs) has been proposed by self-assembling adenosine triphosphate (ATP) with 5-sulfosalicylic acid (SSA) and Tb3+. Due to the antenna effect, SSA-Tb-ATP ICPs exhibited strong green fluorescence emission of Tb3+ (at 547 nm) and blue fluorescence emission of SSA (at 407 nm). This material offers several advantages over existing detection methods, including simplicity of synthesis and exceptional sensitivity. Our self-calibrating SSA-Tb-ATP ICPs demonstrated excellent performance in detecting alkaline phosphatase (ALP) and phosphate (Pi) in both serum and environmental samples with detection limits of 0.076 U/L and 0.025 μM, respectively. Moreover, we successfully employed the SSA-Tb-ATP ICPs to perform cellular imaging of ALP in both hepatocellular carcinoma cells (HepG2) and normal liver cells (LO2), representing a significant advancement in ALP detection and imaging. The simplicity of the synthesis and high sensitivity make this probe a promising tool for early diagnosis of hepatocellular carcinoma in clinical settings and environment analysis.

Portable smartphone platform based on a ratio fluorescence probe for situ visual monition of cardiac disease markers in vitro

Portable smartphone platform based on a ratio fluorescence probe for situ visual monition of cardiac disease markers in vitro

A highly selective ratio fluorescence probe for detecting cysteine and its bioimaging application

Cysteine is an important thiol amino acid that is abundantly present in cells and has an important function in various life processes of the human body. Therefore, it is of great significance to develop an accurate method for monitoring cysteine concentration in cells. We designed and synthesized a novel FRET-ICT-based ratiometric fluorescence and colorimetric probe (BD-C) for detecting cysteine. As cysteine was gradually added, the fluorescence intensity of probe BD-C in buffer solution decreased at 614 nm and increased at 428 nm. The logarithm of the fluorescence intensity ratio to cysteine exhibited favorable linearity in the concentration range of 0.5–14.0 μM, with a detection limit of 395 nM. The energy transfer efficiency of this FRET system is up to 98.8%. BD-C demonstrated preeminent selectivity for cysteine and could specifically react with cysteine, though other sulfhydryl amino acids, such as GSH and Hcy, were present. Furthermore, BD-C exhibited outstanding targeting ability to the endoplasmic reticulum (ER) and was successfully applied in cellular imaging.

A smartphone-assisted paper-based ratio fluorescent probe for the rapid and on-site detection of tetracycline in food samples

Rapid, sensitive and portable analytical methods for on-site detection of tetracycline (TC) in food samples is of critical importance for food safety and public health. In this study, a dual-emission ratio fluorescent probe (Gd0.9@Eu0.1) was prepared and utilized for the detection of tetracycline (TC) by observing the fluorescence color change from blue to red. The detection process exhibits a wide linear range (0–52.0 μM), good selectivity and low detection limit (14 nM). A paper-based probe and a colorimetric card was constructed for the visual detection of TC. Furthermore, a novel and portable detection platform combining smartphone and test strip was exploited for the quantitative and on-site detection of TC in real pork sample. The developed method was validated through intra- (n = 5) and inter-day (n = 2) measurements, as well as comparison with a traditional HPLC method. These statistical result validate the reliability and accuracy of the developed method. This intelligent detection platform represents a promising approach for the rapid, sensitive and visual detection of TC in food samples.