Selective Ratiometric Fluorescence Research Articles

A simplified ratiometric fluorescent sensing strategy for enhanced detection of alkaline phosphatase employing Prussian blue nanozymes and commercially available chromogen

The traditional nanozymes-based ratiometric fluorescence sensing platforms usually necessitate the supplementary addition of fluorescent probes, therefore greatly restricting its convenient and broad application. In this study, a highly sensitive and selective ratiometric fluorescence platform for alkaline phosphatase (ALP) detection was established, only employing Prussian blue (PB) nanozymes and a commercially available chromogen of o-phenylenediamine (OPD). PB nanozymes with remarkable peroxidase-like (POD-like) activity can effectively catalyze OPD chromogen to yield 2,3-diaminophenazine (OPDox) with an intense yellow fluorescence at 573 nm emission peak. Target ALP can facilitate ascorbic acid 2-phosphate (AAP) dephosphorylation to generate phosphate and ascorbic acid (AA). Significantly, both these two resultant hydrolysis products could effectively decrease the OPDox generation via a dual-path based inhibition on the PB nanozymes POD-like activity. On the other hand, the generated dehydroascorbic acid (DHAA) from AA oxidation would exclusively react with OPD chromogen to yield 3-(dihydroxyethyl)furo[3,4-b]quinoxaline-1-one (DFQ) with a strong blue fluorescent signal at 434 nm, which further providing a significant enhancement on the sensing selectivity of ALP detection. As a result, an increased yellow fluorescence of OPDox and decreased blue fluorescence of DFQ could be clearly observed with different ALP addition. A robust linear relationship between the fluorescence ratio of F434/F573 and ALP activity ranging from 0.25 U/L to 6 U/L was obtained, with a low detection limit of 0.112 U/L. This proposed method demonstrates high sensitivity, excellent selectivity, cost-effectiveness, and operational simplicity, yet enabling an effective detection of ALP levels in human serum.

Highly sensitive and selective ratiometric fluorescence and colorimetric detection of Cr(VI) via in situ encapsulation of green/red carbon quantum dots in zeolite

To overcome the limitations arising from non-uniform particle size and solid-state aggregation of carbon quantum dots (CQDs), a novel dual-emissive ratiometric fluorescence probe, GCQDs@SBA-15/RCQDs@SBA-15 (G-RCQDs@SBA-15), has been successfully constructed by simplifying the synthesis process through in situ synthesis of CQDs in SBA-15 to further enhance their optical properties for highly sensitive detection of Cr(VI). The probe G-RCDs@SBA-15, based on green-emission carbon quantum dots (GCQDs) encapsulated in mesoporous molecular sieves SBA-15, provides the response signal, while red-emission carbon quantum dots (RCQDs) encapsulated in SBA-15 serve as an internal reference. The probe exhibits a satisfactory limit of detection (LOD) of 0.336 μM, which is 52 % lower than GCQDs/RCQDs. Importantly, the probe shows superior selectivity in detecting Cr(VI) compared to other metal ions. The fluorescence signal ratio of the probe decreases with increasing Cr(VI) concentration, resulting in a distinct change of fluorescence color from green to red. Based on UV–vis and fluorescence lifetime analysis, Inner filter effect (IFE) is considered the primary potential mechanism for the fluorescence color transition of G-RCDs@SBA-15 following the addition of Cr(VI). G-RCQDs@SBA-15 not only inherits the excellent optical properties of GCQDs and RCQDs but also shows high fluorescence and chemical stability. Considering the sensitive photoconversion properties of G-RCQDs@SBA-15, a smartphone-based laboratory device in combination with RGB analysis software has been used for Cr(VI) detection by directly capturing and analyzing fluorescence images. In addition, the sensing system is validated in the actual lake water samples, exhibiting recoveries from 83.3 % to 96.3 %, indicating its excellent practicality for Cr(VI) detection in real samples.

A ratiometric, turn-on fluorosensor for specific detection of Zn2+ ions

A potentially active fluorescent chemosensor (E)-2-(((2-(1H-benzo[d]imidazol-2-yl)phenyl)imino)methyl)-5-(diethylamino)phenol (BMDP) is developed by the condensation of 2-(2-aminophenyl)-1H-benzimidazole and 4-(diethylamino)salicylaldehyde. It shows an exceptional ratiometric fluorescence behavior when exposed to Zn2+ ions and the photoluminescence color is changed from blue to cyan under the exposure of a 365 nm UV light which is also strongly evident from the color chromaticity diagram. The exceptional ratiometric fluorescence behavior in the presence of Zn2+ ions is found to be due to the chelation-enhanced fluorescence (CHEF). The 1:1 stoichiometry of BMDP and Zn2+ ions in Zn2+ ions chelated BMDP complex is confirmed through Job’s plot analysis. Remarkably, Cd2+ does not interfere with the selective ratiometric fluorescence behavior induced by Zn2+ ions. The lowest detection limit and quantification limit are estimated to be 28 nM and 92 nM respectively. The cyan fluorescence of the Zn2+ ions chelated BMDP complex is interestingly reversed to the original BMDP in the presence of ethylenediamine tetraacetic acid (EDTA). At the molecular level, this can be thought of as a complimentary “INHIBIT” logic gate. Furthermore, it is possible to utilize the probe for on-site identification in test strips with improved Zn2+ ions selectivity. We have also used a smartphone-based method to demonstrate the usefulness of BMDP for the immediate quantification and detection of Zn2+ ions. In light of this, probe BMDP is a trustworthy fluorescence probe for on-site monitoring that can accurately identify Zn2+ ions even when some other metals and anions compete.

On-Site Quantitative Visualization of Singlet Oxygen in Crops via an Organic Small Molecule-Based Ratiometric Fluorescent Probe and a Mobile Fluorescence Analysis Device.

Singlet oxygen (1O2) plays imperative roles in a variety of biotic or abiotic stresses in crops. The change of its concentration within a crop is closely related to the crop growth and development. Accordingly, there is an urgent need to develop an efficient analytical method for on-site quantitative detection of 1O2 in crops. Here, we judiciously constructed a novel ratiometric fluorescent probe, SX-2, for the detection of 1O2 in crops. Upon treating with 1O2, probe SX-2 displayed highly selective ratiometric fluorescence response, which is favorable for the quantitative detection of 1O2. Concurrently, the fluorescence solution color of probe SX-2 was varied, obviously from blue to yellow, indicating that the probe is beneficial for on-site detection by the naked eye. Sensing reaction mechanism studies showed that the 2,3-diphenyl imidazole group in SX-2 could function as a new selective recognition group for 1O2. Probe SX-2 was utilized for the detection of photoirradiation-induced 1O2 and endogenous 1O2 in living cells. The changes in the 1O2 level in zebrafish were also tracked by fluorescence imaging. In addition, the production of 1O2 in crop leaves under a light source of different wavelengths was studied. The results demonstrated more 1O2 were produced under a light source of 365 nm. Furthermore, to achieve on-site quantitative detection, a mobile fluorescence analysis device has been made. Probe SX-2 and mobile fluorescence analysis device were capable of on-site quantitative detecting of 1O2 in crops. The method developed herein will be convenient for the on-site quantitative measurement of 1O2 in distinct crops.

Chemical surface modification of carbon dots with Germanium: A highly sensitive and selective ratiometric fluorescence probe for Mg2+ detection using DFT and TD-DFT

In this study, we chemically modified carbon dots (Cdots) using germanium, enhancing their sensitivity and selectivity as a ratiometric fluorescence probe for precise detection of Mg2+ ions. Excitation of the modified Cdots resulted in a distinct emission peak at 527 nm, enabling accurate measurement of Mg2+ concentrations across a linear range. The surface modification with germanium led to the creation of novel emitting centers on the Cdots' surface. Theoretical calculations using density functional theory (DFT) revealed the effective suppression of these emitting centers through a photo-induced electron transfer (PET) process, utilizing the nitrogen lone pair electrons on the Cdots' surface. Furthermore, adjacent Cdots' surface pyrazino[2,3-f][1,10]-phenanthroline (PPT) nitrogen atoms formed chemical bonds with Mg2+ ions, resulting in the formation of aggregated Cdots. Consequently, the intricate complexation terminated the PET process, resulting in a novel emission peak at longer wavelengths. This study presents a highly sensitive and selective ratiometric fluorescent detection system with exceptional low concentration detection limit for precise Mg2+ ion detection.

A ratiometric fluorescent probe revealing the abnormality of acetylated tau by visualizing polarity in Alzheimer's disease.

Abnormal neuronal polarity leads to early deficits in Alzheimer's disease (AD) by affecting the function of axons. Precise and rapid evaluation of polarity changes is very important for the early prevention and diagnosis of AD. However, due to the limitations of existing detection methods, the mechanism related to how neuronal polarity changes in AD is unclear. Herein, we reported a ratiometric fluorescent probe characterized by neutral molecule to disclose the polarity changes in nerve cells and the brain of APP/PS1 mice. Cy7-K showed a sensitive and selective ratiometric fluorescence response to polarity. Remarkably, unlike conventional intramolecular charge transfer fluorescent probes, the fluorescence quantum yield of Cy7-K in highly polar solvents is higher than that in low polar solvents due to the transition of neutral quinones to aromatic zwitterions. Using the ratiometric fluorescence imaging, we found that beta-amyloid protein (Aβ) inhibits the expression of histone deacetylase 6, thereby increasing the amount of acetylated Tau protein (AC-Tau) and ultimately enhancing cell polarity. There was a high correlation between polarity and AC-Tau. Furthermore, Cy7-K penetrated the blood-brain barrier to image the polarity of different brain regions and confirmed that APP/PS1 mice had higher polarity than Wild-type mice. The probe Cy7-K will be a promising tool for assessing the progression of AD development by monitoring polarity.

A thiophene-linked terpyridine based phenanthridine chemoreceptor for Cd2+ and Cr3+ selective ratiometric fluorescence detection in environmental water and rice samples

BackgroundThe studied materials, Cadmium (Cd2+) and Chromium (Cr3+) are highly toxic, and it focuses on investigating various environmental sources, such as industrial processes and waste water. When quantities of Cr3+ and Cd2+ exceed the allowable limit, biological toxicity and hazardous environmental pollution are unavoidable. In order to address this problem, we introduce 5-(5-(4-([2,2':6′,2″-terpyridin]-4′-yl) phenyl) thiophen-2-yl)-7,8,13,14-tetrahydrodibenzo [a,i] phenanthridine (TPTP), a dual-emission response chemosensor that employs a colorimetric and fluorescence turn-on approach for the rapid, sensitive, and discriminate detection of Cr3+ and Cd2+ ions. ResultsWe created a newly designed luminous TPTP sensor based on intramolecular charge transfer (ICT). TPTP sensor probe specifically determined Cr3+ and Cd2+ ions with an immediate colour shift from cyan to green and orange in CH3CN: H2O (6:4) solvent solution. The permissible level set by the Environmental Protection Agency (EPA) of the United States for the presence of Cr3+ and Cd2+ ions in drinking water was higher than the detection level of 3.5 and 9.7 nM, by this sensor respectively. NMR titrations, HRMS, and theoretical calculation methods were employed to examine the accurate sensing processes of TPTP and complexes. SignificanceThis is an effective method of detecting Cr3+ and Cd2+ ions in an environmental system using a ratiometric methodology. In addition, TPTP was used to determine the concentration of Cr3+ and Cd2+ ions in natural water and food samples. Fluorescent bio-imaging studies revealed that the present sensor TPTP could identify Cr3+ and Cd2+ ions inside living HeLa cells. A paper kit analysis has been done on TPTP, which has a time-to-result of less than 1 s and offers a cost-effective assay. As a result, the platform offers portability.

Amorphous amEu-NH2BDC and amTb-NH2BDC as ratio fluorescence probes for smartphone-integrated naked eye detection of bacillus anthracis biomarker

The abnormal concentration of anthrax spore biomarker 2,6-pyridinedicarboxylic acid (2,6-DPA) will seriously affect public health. Therefore, a sensitive and rapid assay for 2,6-DPA monitoring is of vital importance. In this work, novel nano-sized amorphous Eu-NH2BDC (amEu-NH2BDC) and amorphous Tb-NH2BDC (amTb-NH2BDC) metal organic frameworks are prepared by adjusting the ratio of metal and ligand, respectively. Both of them exhibit highly sensitive and selective ratiometric fluorescence detection for 2,6-DPA with wider linear range and lower detection limit in aqueous solutions and human serum. Attributed to the coordination effect of 2,6-DPA in triggering the characteristic fluorescence emissions of Eu3+or Tb3+ by replacing coordinated solvent molecules, as evidenced by ultraviolet–visible spectroscopy, the fluorescence lifetimes analysis, thermal gravimetric analysis, Fourier-transform infrared spectroscopy, density functional theory (DFT) simulations and X-ray photoelectron spectroscopy. In addition, the amEu-NH2BDC or amTb-NH2BDC loaded paper-based microsensors are constructed for real-time and sensitive detection of 2,6-DPA and coupled with a smartphone-assisted visual portable device.

Preparation of dual-ligands Eu-MOF nanorods with dual fluorescence emissions for highly sensitive and selective ratiometric/visual fluorescence sensing phosphate

In this work, a new MOF Eu-BTC-BDC-NH2 (BTC = benzene-1,3,5-tricarboxylate, BDC-NH2 = 2-aminoterephthalic acid) was synthesized by a facile and energy-efficient process, and can be utilized as a highly sensitive and selective ratiometric fluorescence probe for phosphate (Pi). The produced Eu-MOF had two emission peaks at 425 nm and 617 nm, which came from the BDC-NH2 ligand and energy transfer effect between the two ligands and Eu3+, respectively. When contact with Pi, due to the ultra-high affinity between Eu3+ and the oxygen atoms in Pi, part of the ligands were replaced and P-O-Eu bonds formed. Accordingly, the energy transfer effect was weakened, and the fluorescence intensity at 617 nm reduced, however, the peak at 425 nm increased. Based on this, a Pi ratiometric fluorescence platform with excellent performance was established with a low detection limit (LOD) of 0.07 μM and superior selectivity for 19 common ions and 6 phosphate-containing molecules. In addition, the sensor achieved satisfactory results in the detection of environmental water samples. Finally, a portable detection kit based on hydrogel-MOFs was successfully constructed by combining with a smartphone, which can realize on-site monitoring of Pi.

A selectivity-enhanced ratiometric fluorescence imprinted sensor based on synergistic effect of covalent and non-covalent recognition units for ultrasensitive detection of ribavirin

Development of methods with high selectivity and sensitivity for detection of trace ribavirin (RBV) is of great importance for environmental protection and food safety. Herein, we proposed a simple yet valid strategy to construct the highly selective ratiometric fluorescence sensing platform (BA-LMOFs@MIP) for analysis of RBV based on boric acid-functionalized lanthanide metal-organic framework (BA-LMOFs) coupled with molecularly imprinted polymer (MIP). In this strategy, BA-LMOFs featured with dual-emission and pH-responsive behavior were first synthesized as supporter. Benefiting from boric acid group of BA-LMOFs, RBV was easily immobilized onto its surface, taking advantage of template immobilization-based surface imprinting means to fabricate BA-LMOFs@MIP with dual recognition sites for the first time. The synergistic effect of covalent boronate affinity-based recognition unit and non-covalent imprinting sites enabled BA-LMOFs@MIP to exhibit superior selectivity and binding efficiency to RBV. BA-LMOFs as signal tag endowed BA-LMOFs@MIP with desirable sensitivity, photostability and hydrophilicity. More importantly, BA-LMOFs@MIP-based sensor displayed a wide linear range for RBV from 25 to 1200 ng mL−1 with a detection limit down to 7.62 ng mL−1. The sensor was finally applied to RBV determination in real samples, and the obtained results revealed that BA-LMOFs@MIP would be a promising candidate for monitoring of RBV in complex systems.

Ratiometric fluorescence for sensitive detection of phosphate species based on mixed lanthanide metal organic framework.

Phosphate (PO43-) plays a major role in aquatic ecosystems and biosystems. Developing a highly sensitive and selective ratiometric fluorescence probe for detection of PO43- is of great significance to the ecological environment and human health. In this work, a novel dual lanthanide metal organic framework was synthesized via hydrothermal reaction based on Tb3+ and Ce3+ as the center metal ions and terephthalic acid as the organic ligand (designated as Tb-Ce-MOFs). The fluorescence of Tb-Ce-MOFs shows emission at 375nm. In the presence of PO43-, with increased concentration of PO43-, the fluorescence intensity of Tb-Ce-MOFs at 500nm and 550nm increased, while the intensity at 375nm was reduced. Hence, ratiometric fluorescence detecting of PO43- can be achieved by measuring the ratio of fluorescence at 550nm (FL550) to 375nm (FL375) in the fluorescent spectra of the Tb-Ce-MOFs. In this sensing approach, the Tb-Ce-MOFs probe exhibits highly sensitive and selective for detection of PO43-. The limit of detection is calculated to be 28nM and the detection range is 0.1 to 10μM. In addition, the Tb-Ce-MOFs were used in the detection of PO43- in real samples. We design and synthesize a mixed lanthanide metal organic framework fluorescence probe (Tb-Ce-MOFs) for ratiometric fluorescence for the detection of PO43- based on Tb3+ and Ce3+ as the center metal ions and terephthalic acid as the organic ligand.

One-pot synthesis of CeO2-carbon dots with enhanced peroxidase-like activity and carbon dots for ratiometric fluorescence detection of H2O2 and cholesterol

Carbon dots-doped CeO2 (CeO2-CDs) with enhanced peroxidase-like activity and fluorescent carbon dots (CDs) were prepared by one-pot hydrothermal method in this work. The morphology, surface groups and enzymatic properties of CeO2-CDs and optical properties of CDs were studied in detail. The enzyme activity of CeO2-CDs was higher than CeO2 due to the smaller particle size. O-phenylenediamine (OPD) as peroxidase substrate can be catalyzed to fluorescent o-phenylenediamine (oxOPD) by CeO2-CDs, and the UV–vis absorption of oxOPD overlapped partly with the fluorescence emission of CDs. Hence, the fluorescence intensity of CDs would be decreased by oxOPD due to the inner filter effect. Based on this, a sensitive and selective ratiometric fluorescence method for H2O2 and cholesterol was developed. The detection ranges for H2O2 and cholesterol are 1.67 µM-2.01 mM and 1.66 µM-1.65 mM with the detection limits are 0.35 µM and 0.49 µM (3Ϭ), respectively. Moreover, this method has been successfully used to detect cholesterol in human serum.

Thiophene-phenylquinazoline probe for selective ratiometric fluorescence and visual detection of Fe(iii) and turn-off fluorescence for I− and its applications

A 2,5-bis(4-phenylquinazolin-2-yl)thiophene (BQT) probe is designed, synthesized and explored for selective ratiometric fluorescence and visual detection of Fe3+ and as a turn-off fluorescence probe for I- anion. BQT is colorless and has blue emission in CH3CN solution. BQT selectively complexes with Fe3+, turns its solution from colorless to greenish yellow and enables the ratiometric sensing of Fe3+ with limit of detection (LOD) and limit of quantitation (LOQ) of 2 × 10-8 M and 6.1 × 10-8 M, respectively. Binding constant of BQT with Fe3+ is found to be 4.1 × 10-4 M-1. BQT is also able to sense I- anion present in aqueous solution by selectively turning colorless to yellow and fluorescence quenching with a LOD of 1.7 × 10-7M and LOQ of 5.2 × 10-7 M. BQT sensing ability is not influenced by the presence of other metal ions and anions in the vicinity. The BQT-Fe3+ complex is thoroughly characterized using MALDI-TOF, NMR and Job's plot. A reversibility experiment with EDTA suggests BQT is a reversible fluorescent chemosensor for Fe3+ ions. The spectroscopic data of BQT and its complexes are employed to construct a field test kit for qualitative analysis and INHIBIT logic gate.

Intrinsic dual-emissive carbon dots for efficient ratiometric detection of Cu2+ and aspartic acid

Herein, novel intrinsic dual-emitting carbon dots (CDs) are prepared through a one-step hydrothermal treatment of glucose and 3-nitroaniline in sulfuric acid solution and utilized for ratiometric determination of Cu2+ and aspartic acid (Asp). The CDs exhibited an interesting pH-switchable emission behavior displaying an intrinsic dual-emitting peak with emission maxima at 400 and 610 nm at pH 4.0–5.0. The presence of Cu2+ intensively quenched the first emission peak at 400 nm, but it had a negligible effect on the second emission peak. The ratiometric signal displayed a high selectively for Cu2+ over other metal ions and provided a linear response over the concentration range of 0.01–1.00 μM with a detection limit of 7.0 nM. Moreover, at pH 4.0, Asp was able to restore the quenched fluorescence of the CDs-Cu2+ system with a much more successful performance than other amino acids. This on-off-on fluorescence behavior provided a selective ratiometric fluorescence method for the determination of Asp in the concentration range of 0.2–15 μM. The acceptable detection results for Cu2+ in a river water sample (compared to Inductively Coupled Plasma (ICP) method) and for Asp in human serum samples confirmed the potential application of this ratiometric nanoprobe for sensing in real samples.

A highly selective ratiometric fluorescence probe for bioimaging of hypobromous acid in living cells and zebrafish

Hypobromous acid is an important reactive oxygen species (ROS), which is involved in operating various cellular functions. However, the abnormal production of HOBr can induce the generation of a variety of diseases. Although fluorescence probes are huge contributor to our understanding of the biological roles of HOBr, relatively few probes have been used to detect HOBr. Hence, we constructed a ratiometric fluorescent probe Ratio-HOBr with high selectivity to sensitively monitor HOBr. Probe Ratio-HOBr exhibited quick response (< 10 s) for HOBr. Besides, probe Ratio-HOBr has high selectivity and sensitivity for HOBr with a linear concentration range from 0−20 μM and a limit of detection as 92 nM. Further studies found that probe Ratio-HOBr showed good biocompatibility for imaging HOBr in living cells and zebrafish.

Detection of Lipase Activity in Cells by a Fluorescent Probe Based on Formation of Self-Assembled Micelles.

SummaryReliable and sensitive detection of lipase activity is essential for the early diagnosis and monitoring of acute pancreatitis or progression of digestive diseases. However, the available fluorescent probes for detection of lipase activity are only implemented in a hexane-water two-phase system due to the nature of heterogeneous catalysis of lipase, thus limiting their applications in direct imaging of lipase activity in living cells and tissues. Here we designed and synthesized a “turn on” fluorescent probe CPP based on self-assembled micelles for hydrolysis of lipase. The CPP probe exhibits high selectivity and excellent sensitivity for the detection of lipase in such a homogeneous system and is successfully applied for monitoring lipase activity in pancreatic AR42J cells, tissues, and serums. Taken together, the fluorescent CPP probe not only provides a tool for diagnostic potential in pancreatic disease but also demonstrates an application potential for micelle self-assembly-based development of biological probes.

Facile and Highly Selective Ratiometric Fluorescence Probe Based on Benzo[5]helicene for the Detection of Hypochlorous Acid

In physiological processes, hypochlorous acid can regulate in vitro signaling molecules as one kind of reactive oxygen species (ROS). Serious diseases, such as cardiovascular disorders, neurodegenerative diseases, Alzheimer’s disease, and cancers are usually concerned with the abnormal levels of hypochlorous acid in human bodies. Herein, we report a new probe DPH-BP for HClO, which consists of a benzo[5]helicene-pyridine fluorophore and benzyl-benzeneboronic acid pinacol ester as HClO reaction sites. The structural motifs combined with chromogenic media and fluorescence become a single-molecule sensor response in aqueous solutions. In the presence of HClO, this probe shows a remarkable blue shift of fluorescence from 536 to 452 nm in an aqueous solution and obvious fluorescence color change from yellow to blue. In the same conditions, almost no response can be recorded with the other common ROS/RNS, such as H2O2, TBHP, •OH, t-BuO•, ONOO–, and O2•–. As we have designed, the oxidation of phenylboronic ester by HClO induces the cleavage of the benzyl in DPH-BP, which has been proven by 1H NMR spectra and density functional theory calculations. To the best of our knowledge, this is the first report of the analysis of HClO using the oxidation of benzyl-benzeneboronic acid pinacol ester.

Selective ratiometric fluorescence detection of hypochlorite by using aggregation-induced emission dots.

The development of simple and effective tools for selective ratiometric detection of hypochlorite (ClO-) is one of the most important goals for elucidating the biofunction of ClO- in associated diseases. However, most developmental probes suffer from the notorious aggregation-caused quenching (ACQ) effect that greatly limits their applications. Herein, we report on novel aggregation-induced emission dots (AIED) for ratiometric detection of ClO- via a co-precipitation strategy. The AIED nanoprobe displayed a ratiometric signal output, which was more promising to minimize the bad environmental factors and simultaneously avoided the ACQ effect. Notably, amphiphilic block copolymer endowed the nanoprobe with stable water dispersibility and easy modification. The as-prepared AIED probe exhibited high sensitivity (~ 89nM), high selectivity, outstanding photostability, and prominent long-term fluorescence stability. Furthermore, the as-prepared AIED was applied for the visualized fluorescence detection of ClO- and further utilized to detect ClO- in real samples. We expect the nanoprobe to be an outstanding tool to understand ClO--associated diseases. Graphical abstract Illustration of the probe for the detection of ClO-.

Peptide-based ratiometric fluorescent probe for highly selective detection of Cd (II) and its application in bioimaging

This work reported a new peptide fluorescent probe L including dansyl group (acceptor) and tryptophan (donor) via imitated the binding sites of natural protein. L exhibited exclusively selective ratiometric fluorescence response towards Cd2+ ions over other metal ions based on fluorescent resonance energy transfer (FRET) effects. As designed, L showed exciting sensitivity to Cd2+ ions in aqueous media, and the detection limits are less than 27.5 nM. In addition, the binding pattern of L and Cd2+ was confirmed by fluorescence titration analysis which was found to be 2:1 and further it was confirmed by Job’s plot. What’ more, L exhibited very low biotoxicity and exciting cell infiltration, and have been successfully used for fluorescence imaging of Cd2+ ions in living HeLa cells.

Ratiometric fluorescence detection of hydroxyl radical using cyanine-based binary nanoGUMBOS

Overproduction of reactive oxygen species (ROS) results in oxidative stress, which is closely associated with pathogenesis of many diseases. Visualized detection of ROS in situ enables deeper insight into the mechanisms that underlie such pathological and physiological processes. Among reactive species, selective detection of hydroxyl radical is the most challenging, due to high aggression and short life time of this specie. In this regard, we have developed a sensitive and selective ratiometric fluorescence nanoprobe for detection of hydroxyl radical. This probe is based on use of GUMBOS (a Group of Uniform Materials Based on Organic Salts) that are derived from 1,1′-diethyl-2,2′-cyanine iodide and 1,1′-diethyl-2,2′-carbocyanine iodide. Each GUMBOS exhibit different reactivity towards reactive species. Without any chemical linkage, these two GUMBOS were combined into a single nanomaterial to produce a ratiometric fluorescent sensing profile through Förster resonance energy transfer. This cyanine-based ratiometric nanoprobe exhibited high selectivity for the hydroxyl radical in comparison to other ROS, including superoxide anion, singlet oxygen, hydrogen peroxide, and peroxynitrite. Furthermore, detection of hydroxyl radical was successfully demonstrated by use of these binary nanoGUMBOS in vitro using hormone-independent human breast adenocarcinoma cells (MDA-MB-231).