Search

Proteins are an essential component of living organisms, and the study of their structure and function is of great importance in biological and medical research. In recent years, the remarkable phenomenon of aggregation-induced emission (AIE) has been extensively utilized in protein detection. Significant progress has been made in the development of aggregation-induced emission luminogens (AIEgens), which have proven invaluable in protein imaging. This review highlights AIEgen-conjugated probes for imaging proteins in tumor cells through various mechanisms, including physical interactions, ligand binding, and enzymatic cleavage. These probes exploit the AIE effect to enhance the signal-to-noise ratio, providing important tools for protein research. Additionally, these probes can be used to study structural changes in intracellular protein phase separation processes, such as unfolded, misfolded, fibrous, and amorphous aggregates. The above research achievements presented lay the foundation for the widespread application of AIEgen-conjugated probes in the biomedical field and are expected to stimulate further development in related research., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Background: Cascade activated probes have received extensive attention due to their sequence-dependent detection of multiple markers in pathologic pathways. HSO 3 - and Cu 2+ are biomarkers of intracellular mitochondrial activity, and their simultaneous detection is of great significance. Until now, probes that detect them simultaneously were all based on displacement mechanism with "ON-OFF-ON" switches in an emission channel. In other words, using HSO 3 - and Cu 2+ as two inputs in logic sensing, the inputs of (0,0), (0,1), or (1,1) gave the same "1" output. Therefore, they suffered from the false positive signals in clinical application., Results: The de novo design of fluorescent probes with a more advanced sensing mechanism was explored. The four dyes, CM-Cu, CMA-Cu, R1, and R2, have similar structures, but their sensing behaviors are quite different. For dual detection of HSO 3 - and Cu 2+ , CM-Cu showed emission "ON-OFF-ON" switches based on IMP logic gate; while CMA-Cu, having one more aldehyde, was cascade activated based on AND gate for the first time. Noteworthily, unlike most dual-locked probes, which usually involve a complex synthesis process, here, cascade activation by HSO 3 - and Cu 2+ is achieved by adjusting the electron distribution of a ready-made structure. Coupled with its low toxicity, high specificity, strong solid emission, and anti-diffusion ability, the sensing property of CMA-Cu have been validated in digital encryption and cell imaging., Significance: We exhibited how to adjust the dual recognition from displacement to cascade activation by fine-tuning the molecular structure. This study may provide a new idea for the simple design of dual-locked probe, which is helpful for the sequential detection of multiple biomarkers with physiological correlation and could improve the accuracy of disease diagnosis., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2025 Elsevier B.V. All rights reserved.)

Realizing protein analysis in organelles of living cells is of great significance for developing diagnostic and therapeutic methods of diseases. Fluorescent-labeled antibodies with well imaging performance and high affinity are classical biochemical tools for protein analysis, while due to the inability to effectively enter into cells, not to mention organelles and the uncontrollable reaction sites that might cause antibodies inactivation when chemically modification, they are hard to apply to living cells. Inspired by the structure of fluorescent-labeled antibodies, we designed as a universal detection platform that was based on the peptide-conjugated probes (PCPs) and consisted of three parts: a) a rotor type fluorescent molecular scaffold for conjugation and signal output; b) the cell penetration protein recognition unit; c) the subcellular organelle targeting unit. In living cells, PCPs could firstly localize at organelles and then proceed protein specific recognition, thus jointly leading to the restriction of twisted intramolecular charge transfer and activation of fluorescence signal. As a proof-of-concept, six different proteins in three typical intracellular organelles could be detected by our platform through simply replacing the recognition sequence of proteins and matching organelle targeting units. The position and intensity of fluorescence signals demonstrated specificity of PCPs and universality of the platform., (© 2024 Wiley‐VCH GmbH.)

A mitochondria-targeted ratiometric fluorescent probe (Mito-Zn) was first designed and synthesized with dual emissions both located in the near-infrared region, for Zn 2+ detection with high sensitivity and selectivity. By using the developed Mito-Zn, a high level of Zn 2+ in the depressed mouse brain was discovered for the first time.

Identifying nitroreductase (NTR) with fluorescent techniques has become a research hotspot, due to its good sensitivity and selectivity toward the early-stage cancer diagnosis and monitoring. Herein, a host-guest reporter ( NAQA ⊂ Zn-MPPB ) is successfully achieved by encapsulating the NTR probe NAQA into a new NADH-functioned metal-organic cage Zn-MPPB , which makes the reporter for ultrafast detection of NTR within dozens of seconds in solution. The host-guest strategy fuses the Zn-MPPB and NAQA to form a pseudomolecule material, which changes the reaction process of NTR and NAQA from a double substrates mechanism to a single substrate one, and accelerates the reduction efficiency of NAQA . This advantage make the new host-guest reporter exhibit a linear relationship between emission changes and NTR concentration, and it shows better sensitively toward NTR than that of NAQA . Additionally, the positively charged water-soluble metal-organic cage can encapsulate NAQA in the cavity, promote it to dissolve in an aqueous environment, and facilitate their accumulation into tumor cells. As expected, such host-guest reporter displays a fast and high efficiently imaging capability toward NTR in tumor cells and tumor-bearing mice, and flow cytometry assay is conducted to corroborate the capability as well, implying the considerably potential of host-guest strategy for early tumor diagnosis and treatment.

Adenosine triphosphate (ATP) is an important kind of metabolized biological molecule that is formed in organisms, especially in mitochondria, is used universally as energy, and is one of the most significant multifunctional biological molecules. Metal-organic frameworks (MOFs) have been widely used in many applications such as gas storage and separation, drug delivery, heterogeneous catalysis, chemical sensors, etc. Remarkably, lanthanide MOFs (Ln-MOFs), which display large pores, multiple dimensions, and unique lanthanide luminescence properties, are widely used as chemical sensors. A novel three-dimensional probe, Eu 2 (sbdc) 3 (H 2 O) 3 (Eu-sbdc), was successfully self-assembled with Eu(NO 3 ) 3 ·6H 2 O and 5,5-dioxo-5 H -dibenzo[ b , d ]thiophene-3,7-dicarboxylic acid (H 2 sbdc). The Ln-MOF Eu-sbdc can quickly and effectively optically detect ATP via a luminescent quenching mechanism. The K sv value of Eu-sbdc is 1.02 × 10 4 M -1 , and the lower detection limit of Eu-sbdc for ATP is 20 μM, which is more sensitive to ATP. Its mechanism of monitoring ATP might be a dynamic or static quenching process. Eu-sbdc could effectively and quickly recognize ATP with high sensitivity.

Impairment of the protein quality control network leads to the accumulation of unfolded and aggregated proteins. Direct detection of unfolded protein accumulation in the cells may provide the possibility for early diagnosis of neurodegenerative diseases. Here a new platform based on a peptide-conjugated thiol-reactive aggregation-induced emission fluorogen (AIEgen), named MI-BTD-P (or D1), for labeling and tracking unfolded proteins in cells is reported. In vitro experiments with model proteins show that the non-fluorescent D1 only becomes highly fluorescent when reacted with the thiol group of free cysteine (Cys) residues on unfolded proteins but not glutathione or folded proteins with buried or surface exposed Cys. When the labeled unfolded proteins form aggregates, D1 fluorescence intensity is further increased, and fluorescence lifetime is prolonged. D1 is then used to measure unfolded protein loads in cells by flow cytometry and track the aggregate formation of the D1 labeled unfolded proteins using confocal microscopy. In combination with fluorescence lifetime imaging technique, the proteome at different folding statuses can be better differentiated, demonstrating the versatility of this new platform. The rational design of D1 demonstrates the outlook of incorporation of diverse functional groups to achieve maximal sensitivity and selectivity in biological samples., (© 2021 Wiley-VCH GmbH.)

Accurate and sensitive fluorescence imaging of intracellular miRNA is essential for understanding the mechanism underlying some physiological and pathological events, as well as the prevention and diagnosis of diseases. Herein, a highly sensitive ratiometric fluorescent nanoprobe for intracellular miRNA imaging was fabricated by integrating a Ru-SiO 2 @polydopamine (Ru-SiO 2 @PDA) nanoplatform with a near-infrared light (NIR)-assisted DNA strand displacement signal amplification strategy. The Ru-SiO 2 @PDA spheres have excellent biosafety, high photothermal effect, and unique photophysical properties that can both emit a stable red fluorescence and well quench the fluorophores getting closer to them. So, when the fuel DNA and carboxyfluorescein (FAM)-labeled signal DNA are co-assembled on their outer surfaces, the FAM's green fluorescence is quenched, and a low ratiometric signal is obtained. However, in the presence of miRNA, the target displaces the signal DNA from the capture DNA, releasing the signal DNA far away from the Ru-SiO 2 @PDA. Then, the green fluorescence recovers and leads to an enhanced I green / I red value. Under NIR light irradiation, the Ru-SiO 2 @PDA increases the local temperature around the probe and triggers the release of fuel DNA, which thus recycles the target miRNA and effectively amplifies the ratiometric signal. Using A549 cells as a model, the nanoprobe realizes the highly sensitive ratiometric fluorescence imaging of miRNA let-7a, as well as its in vivo up- and down-regulation expressions. It provides a facile tool for highly sensitive and accurate intracellular miRNA detection through one-step incubation and may pave a new avenue for single-cell analysis.

To overcome a series of challenges in tumor therapy, modular-agent probes (MAPs) comprised of various functional modules have been proposed. Researchers have tried to optimize the MAPs by exploiting the new modules or increasing the numbers of module, while neglecting the configuration of various modules. Here, we focus on the different spatial arrangements of existing modules. By utilizing a tetraphenylethylene (TPE) derivative with stereochemical structure and dual modifiable end-group sites as small molecule scaffold, two MAPs with same modular agents (module T for enhancing the internalization of MAPs by tumor cells and module M for causing mitochondrial dysfunction) but different spatial arrangements (on the one side, TM-AIE, and two sides, T-AIE-M, of the molecule scaffold) are designed. T-AIE-M with larger RGD binding angle performed higher specificity, while TM-AIE characterizing longer α-helix structure displayed superior toxicity., (© 2021 Wiley-VCH GmbH.)

Hydrogen peroxide (H 2 O 2 ) plays an important role in the human body and monitoring its level is meaningful due to the relationship between its level and diseases. A fluorescent sensor ( CMB ) based on coumarin was designed and its ability for detecting hydrogen peroxide by fluorescence signals was also studied. The CMB showed an approximate 25-fold fluorescence enhancement after adding H 2 O 2 due to the interaction between the CMB and H 2 O 2 and had the potential for detecting physiological H 2 O 2 . It also showed good biocompatibility and permeability, allowing it to penetrate cell membranes and zebrafish tissues, thus it can perform fluorescence imaging of H 2 O 2 in living cells and zebrafish. This probe is a promising tool for monitoring the level of H 2 O 2 in related physiological and pathological research.

Simple, accurate and real-time analytical methods are required for the detection of metal ions in a complex environment. In the present work, a fluorescent probe CPB based on coumarin was designed for recognizing Cu 2+ ions. The fluorescence of CPB gradually quenched with increasing concentration of Cu 2+ ions, due to the interactions between CPB and Cu 2+ ions. With the addition of Cu 2+ ions, the emission changes of CPB exhibited a good liner relationship toward the Cu 2+ ions content in solution. Additionally, CPB could highly selective recognize Cu 2+ ions among other metal ions in solution. Bearing the selectivity and fluorescence property toward Cu 2+ ions, CPB was successfully applied to monitoring Cu 2+ ions in Hela cells and zebrafish.

Fluorescence ratiometric biosensors are valuable tools for the accurate and sensitive prediction and diagnosis of diseases. However, seldom have fluorescence ratiometric biosensors for protein and DNA been reported because of the shortage of suitable nanoscale scaffolds. Herein, a tripyridinyl Ru II complex-encapsulated SiO 2 @polydopamine (Ru-SiO 2 @PDA) nanocomposite was designed as a universal platform for fluorescence ratiometric detection of DNA and protein in serum samples. The Ru-SiO 2 @PDA nanocomposites have a narrow size distribution, exhibit good biosafety, and are convenient for the postmodification of biorecognition elements. Under irradiation, they can emit a stable and strong luminescence at 650 nm and simultaneously quench the fluorescence emitted from the fluorophores getting close to them. Once the capture probes such as single-stranded DNA and aptamer are assembled, the fluorophores labeled on them are then brought close to their PDA shell and quenched. However, the biorecognition behaviors change the probe's configuration and take the fluorophore far away from the PDA shell. Correspondingly, the fluorescence recovers and its ratio to the constant fluorescence reference is linear to the targets' concentration. Using a D-catalyst and thrombin as model analytes, the Ru-SiO 2 @PDA-based nanoplatform shows high sensitivity and good accuracy in the serum sample analysis. Regarding these attractive properties, the Ru-SiO 2 @PDA nanoplatform provides a new avenue for the accurate and sensitive fluorescence assay of a wide range of targets in complex systems.

Reactive oxygen and nitrogen species (RONS) are an important class of oxidative stress mediators which are tightly associated with several diseases. Therefore, it is important to develop an accurate and reliable method for the in situ monitoring of biologically relevant RONS. Fluorescent bioprobes exhibit remarkable sensing properties such as easy operation, rapid response and good sensitivity, and thus have emerged as powerful tools in diverse biomedical applications. Benefiting from remarkable photophysical advantages like large Stokes' shifts, high signal-to-noise ratios and excellent photostability, aggregation-induced emission (AIE) luminogens (AIEgens) show unique superiority for RONS sensing and are widely applied in diverse biomedical applications. In this review, we first introduce the concept of RONS and the sensing principles of RONS by AIE bioprobes. Then we summarize the current state of AIEgens for RONS sensing with some representative examples. Finally, we present a perspective on the future development of RONS sensing based on AIEgens. We hope our review can inspire more endeavors in this fascinating area, further promoting the use of AIEgens in diagnostic analysis and therapy.

Identifying the location and expression levels of enzymes under hypoxic conditions in cancer cells is vital in early-stage cancer diagnosis and monitoring. By encapsulating a fluorescent substrate, L-NO 2 , within the NADH mimic-containing metal-organic capsule Zn-MPB, we developed a cofactor-substrate-based supramolecular luminescent probe for ultrafast detection of hypoxia-related enzymes in solution in vitro and in vivo. The host-guest structure fuses the coenzyme and substrate into one supramolecular probe to avoid control by NADH, switching the catalytic process of nitroreductase from a double-substrate mechanism to a single-substrate one. This probe promotes enzyme efficiency by altering the substrate catalytic process and enhances the electron transfer efficiency through an intra-molecular pathway with increased activity. The enzyme content and fluorescence intensity showed a linear relationship and equilibrium was obtained in seconds, showing potential for early tumor diagnosis, biomimetic catalysis, and prodrug activation., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Fluorescent imaging of receptor tyrosine kinases in living biosystems is an important means for the early diagnosis of cancer, herein an ionic fluorescent sensor (SNB) composed of targeting unit (sunitinib) and nile blue fluorophore linked via long flexible chain has been designed and evaluated. The SNB sensor exhibits distinct fluorescence responses to receptor tyrosine kinases derived from unfolding strategy and targeting ability, which were evaluated through 2D NMR analyses, optical studies, kinase activity assays. The SNB sensor has excellent membrane fluorescent imaging by electrostatic adsorption and can selectively insert into receptor tyrosine kinases domain pocket on the membrane of cancer cell lines. The SNB sensor has been successfully applied in flow cytometry for cell sorting and fluorescence imaging with tumor mouse model in vivo. The SNB senor may help transition the technology into a widely suitable tool for flow cytometry, imaging with confocal microscopes, whole animal imaging and possibly facilitating early diagnoses and treatment of cancer., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Gasotransmitter hydrogen sulfide (H 2 S), produced enzymatically in body, has important functions in biological signaling and metabolic processes. An abnormal level of H 2 S expression is associated with different diseases, therefore, development of novel bioanalytical methods for rapid and effective detection of H 2 S in biological conditions is of great importance. In this work, we report the development of a new responsive nanosensor for ratiometric luminescence detection of H 2 S in aqueous solution and live cells. The nanosensor (Ru@FITC-MSN) was prepared by immobilizing a luminescent ruthenium(II) (Ru(II)) complex into a fluorescein isothiocyanate (FITC) conjugated water-dispersible mesoporous silica nanoparticle (MSN), showing dual emission bands at 520 nm (FITC) and 600 nm (Ru complex). The red luminescence of the formed Ru@FITC-MSN was quenched in the presence of Cu 2+ . The in-situ generated Ru-Cu@FITC-MSN responded to H 2 S rapidly and selectively, showing a linear ratiometric luminescence change in FITC and Ru(II) channels with the H 2 S concentration (0.5-4 μM). Limit of detection (LoD) and limit of quantification (LoQ) were determined to be 0.36 and 1.21 μM. Followed by investigation of cellular uptake processes, the utility of the nanosensor for ratiometric imaging of H 2 S in live cells and its capability to monitor H 2 S levels in inflammatory breast cancer cells were then demonstrated. This study provides a powerful approach for detection of highly reactive and unstable H 2 S biomolecules in live systems., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2019 Elsevier B.V. All rights reserved.)

It is a challenge to develop multifunctional theranostic agents in one molecule, which simultaneously possesses tumor imaging ability with a high signal-to-noise ratio and excellent therapeutic activity. In this work, we synthesized and screened a series of BODIPY (BDP) with various absorption and fluorescence. The interplay of the molecular structure, pH-sensitive absorption and emission, and photodynamic and photothermal activities was well studied in detail. Photoinduced electron transfer, intramolecular charge transfer, and heavy atom effect were leveraged to engineer BDP with tumor imaging and therapeutic functions. The BDP nanoparticle formulations possessed multifunctional biological features, including selective treatment of cancer cells, near-infrared fluorescence, photoacoustic and computed tomography imaging, and photodynamic and photothermal therapy, as validated by cellular and animal experiments. These results not only give a new horizon to multifunctional BDP for biological applications but also show a new way to design the organic dye for tumor imaging and phototherapy.

Since the accumulation of mercury (II) ions in the environment and ecosystem causes serious problems to environment and disease, the recognition of Hg 2+ ions and its bio-imaging is of high importance. In sight of the advantages of fluorescence probes, a new probe ( PMH ) was facilely synthesized by incorporating phenylimidazole fluorophore and 3-methyl-2- benzothiazolinone hydrazone hydrochloride monohydrate. The PMH probe exhibited a ratiometric response for Hg 2+ ions with fluorescence intensity increasing at 520 nm and decreasing at 445 nm simultaneously. The PMH probe interacted with Hg 2+ ions in seconds with high optical stability and showed good selectivity over other metal ions. In addition, the probe has excellent biocompatibility and imaging performance in cells and zebrafish.

A high brightness red fluorescent probe (S-BODIPY) has been developed for the sensitive and specific imaging of HClO/ClO - in vitro and in vivo. This probe exhibits some distinctive features such as excellent resistance to photobleaching, a high fluorescence brightness, high selectivity, as well as a good biocompatibility. Upon oxidation of the thio-ether group into sulfoxide, the probe showed a noticeable ratiometric fluorescence response toward ClO - with fast response (within 30 s) and a low detection limit (59 nM). The probe demonstrated the successful imaging of exogenous and endogenous HClO/ClO - in living HeLa cells, zebrafish, and mice with high signal-to-noise ratios. S-BODIPY allows for the real-time monitoring the level of ClO - in living cells by ratiometric fluorescence imaging, opening up exciting prospects to develop red and even near-infrared BODIPYs with high brightness and good photostability for in vivo imaging.

The development of effective bioanalytical methods for rapid, sensitive and specific detection of HOCl in vitro and in vivo plays a key role for better understanding the roles of this molecule in normal and diseased conditions, but remains challenging due to the highly reactive nature of HOCl and the complicated biological conditions. In this work, a new fluorescence probe, PQI, was developed for monitoring of the HOCl level in biological samples. PQI was easily synthesized by a one-step condensation reaction. Upon addition of HOCl, significant changes in the absorption spectra and the color of the solution were noticed, facilitating the "naked eye" detection of HOCl in PBS buffer. The fluorescence of PQI was found to be significantly increased within a few seconds, leading to "OFF-ON" fluorescence response towards HOCl. The sensing mechanism, oxidation of thioether by HOCl, was confirmed by HRMS titration analysis. PQI features a large Stokes shift, high sensitivity and selectivity, and rapid fluorescence response towards HOCl. Quantitative detection of HOCl in single live cells was demonstrated through fluorescence imaging and flow cytometry analysis. PQI was then successfully used in visualisation of HOCl in live zebrafish and nude mice., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Quantitative detection and visualization of hypochlorous acid (HOCl) in biological samples has emerged as a hot topic in biochemical research because of the important role of this biomolecule in live organisms. In this contribution, a novel 1,8-naphthalimide-based fluorescence probe, DNPH-NA, was designed and synthesized for HOCl detection in aqueous solutions and in biological systems. In the presence of HOCl, significant changes in absorption and fluorescence spectra were observed, which allow for the quantitative detection of HOCl in PBS buffer. The detection limit for HOCl was determined to be 50 nM. In the presence of HOCl, the fluorescence response of DNPH-NA was found to be completed within 2 seconds. The desirable features of DNPH-NA for the detection of HOCl in aqueous solutions, such as its high sensitivity and selectivity, reliability at physiological pH, rapid fluorescence response, and biocompatibility enabled its application in the detection of HOCl in biological samples. Imaging of exogenous HOCl in live HeLa cells and endogenous HOCl generation in live J774A.1 macrophage cells and zebrafish was then successfully performed using DNPH-NA as a fluorescence probe.

Monitoring sulfur dioxide (SO 2 ) derivatives in environment is of great significance due to their harmful effects to the environment and human health. In this study, a fluorescent probe (CZBT) for SO 2 derivatives was prepared from 9-ethyl-9H-carbazole-3,6-dicarboxaldehyde and 2-methyl-benzothiazolium, which displayed a noticeable color change from yellow to colorless along with a remarkable fluorescence change from yellow to blue in response to HSO 3 - . The probe could quantitatively determine the concentration of HSO 3 - with excellent selectivity, high sensitivity and low limit of detection. 1 H NMR and HR-MS spectra demonstrated that a selective 1, 4-nucleophilic addition occurred on the bridge double bond in CZBT. The probe was successfully used to determine the SO 2 derivatives in several real water samples with good recovery. Furthermore, the probe was employed for monitoring the level of intracellular HSO 3 - in HeLa (human cervical cancer) cells by fluorescence imaging. These results indicated that CZBT has a good capability for monitoring SO 2 derivatives in environment and living cells., (Copyright © 2017 Elsevier B.V. All rights reserved.)

A novel coumarin derivatives based fluorescent chemosensor CBH was designed and synthesized by Schiff base reaction, which was connected by 7-(N,N-diethylamino) coumarin-3-aldehyde and 3-methyl-2-benzothiazolinone hydrazone through C=N. X-ray single crystal structure analysis indicated that two aromatic groups of the CBH were almost in the same plane. It displayed enhancement of the fluorescent intensity and absorbance when the sensor CBH interacted with Hg 2+ ions. The chemosensor CBH exhibited a good sensitive and selective recognition towards Hg 2+ ions in the presence of other important relevant metal ions., (Copyright © 2016. Published by Elsevier B.V.)

One of the key roadblocks in UCNP development is its extremely limited choices of excitation wavelengths. We report a generic design to program UCNPs to possess highly tunable dye characteristic excitation bands. Using such distinctive properties, we were able to develop a new excitation wavelength selective security imaging. This work unleashed the greater freedom of the excitation wavelengths of the upconversion nanoparticles and we believe it is a game-changer in the field and this method will enable numerous applications that are currently limited by existing UCNPs.

Fluorescent nanoparticles (NPs) for Al(3+) sensing with high selectivity were developed from a type of carbazole-based conjugated polymer with a two-dimensional donor-π bridge-acceptor (D-π-A) structure. These NPs are characterized by their small particle diameter (∼18 nm), far-red fluorescence emission (centered ∼710 nm), and Al(3+)-induced fluorescence enhancement with high selectivity owing to an Al(3+)-triggered inhibition on the intramolecular charge transfer (ICT) processes between the conjugated backbone and the pendant acceptors. This type of nanoparticle is easily suspended in aqueous solutions, indicating their practical applicability in physiological media, and their ability for intracellular Al(3+) sensing was confirmed. As compared to other types of conjugated polymer based probes showing metal ion mediated fluorescence quenching, these as-prepared NPs possess analyte-enhanced fluorescence emission, which is analytically favored in terms of sensitivity and selectivity. Fluorescence emission with wavelengths in the biological window of maximum optical transparency (∼700 to 1000 nm) is expected to impart a salient advantage for biological detection applications to these as-prepared probes. The superior features of merit of this new type of fluorescent probe, together with the validation of practicability for intracellular Al(3+) ion sensing, are indicative of their potential for application in fluorescence-based imaging and sensing, such as investigations on Al(3+)-related physiological and pathological processes.

A series of fluorescent materials were synthesized by modification of chitosan (CS) with 4-fluoresceincarboxaldehyde (Fluo) and N-methyl-carbazole-3-aldehyde (Cb). Both L-CS-Fluo and L-CS-Cb feature excellent water-solubility and exhibit highly selective fluorescence response to Fe(3+) in environment and biological fields. The high-molecular weight chitosan-based materials: H-CS-Fluo and H-CS-Cb take on doubled absorptivity compared to free chitosan due to the introduction of fluorescence probes. These modified-probe chitosan materials could be regenerated by treating with EDTA. Meanwhile, monomer probes AG-Fluo and AG-Cb linked by D-glucosamine were also synthesized to explore the binding efficiency., (Copyright © 2012 Elsevier B.V. All rights reserved.)

A unique gadolinium complex, Nap-DO3A-Gd, comprising a naphthylamine luminescent moiety, a di-2-picolylamine (DPA) binding chelator, and a 1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid (DO3A) moiety has been designed and synthesized as a dual-functional probe for selective magnetic resonance imaging and fluorescent sensing of copper(II) in living cells. Nap-DO3A-Gd exhibited a turn-on manner of relaxivity changes and a fluorescent quenching toward Cu(2+). Through the introduction of naphthalamide into the Gd(3+) contrast agent platform to restrict the coordination ability of the DPA chelator and with Gd(3+) coordinating to the DPA moiety to turn away the interferences of other metal cations from Cu(2+) detection, the probe featured selective relaxivity changes toward Cu(2+) over other metal ions and brought unique Cu(2+)-specific luminescent responses. The probe was water-soluble with the luminescent detection limit established at 6 ppb and was successfully used for luminescence imaging detection of copper(II) in living cells. The results demonstrated the efficiency and advantage of our approach in the development of a dual-modality image.

A copper(II) complex CuRBT with a ring-closed rhodamine-containing tripodal ligand was synthesized as a highly selective fluorescent imaging agent for nitric oxide (NO). It featured a 700-fold fluorescent enhancement toward NO from a dark-background with the detection limit of NO about 1 nM in aqueous solution and could be applied for monitoring intracellular NO., (This journal is © The Royal Society of Chemistry 2011)

A dye-functionalized silica nanomaterial, SBA-RT was prepared by the immobilization of the Rhodamine-based chemosensor R6G-TETA within the channels of SBA-15. SBA-RT exhibits several different properties compared to the free R6G-TETA, such as higher selectivity, blue-shift of the UV-vis spectra due to special spatial environment in the channels of the mesoporous material. It presents Cr(III)-selective fluorimetric and colorimetric responses in aqueous solution. The fluorescence responses are reversible by treating with EDTA and do not vary over a broad pH range suitable for Cr(III) bioimaging application. Through isolating of the metal ions within the mesopores of the silica, SBA-RT can extract Cr(III) from the solution with only trace amounts remaining. The fluorescence images experiment demonstrated the possibility of further application in monitoring Cr(III) in living cells and organisms., (Copyright © 2011 Elsevier B.V. All rights reserved.)

By incorporating NOO tridentate chelators into rationally designed ligand systems, a well-defined molecular cube Ce-TBDS and a bicoronal trigonal prism Ce-TBBS were achieved via self-assembly and the luminescence recognition of natural saccharides with Ce-TBBS were also investigated., (This journal is © The Royal Society of Chemistry 2011)

New europium(III) complexes Eu(TTA)(2)-DSQ and Eu(TTA)(3)-DR1 were designed and synthesized as new fluorescent pH probes (where HDSQ = 5-(dimethylamino)-N-(4-(2-((8-hydroxyquinolin-2-yl)methylene)hydrazinecarbonyl)phenyl)naphthalene-1-sulfonamide, DR1 = N(1)-(4-(dimethylamino)benzylidene)-N(2)-(rhodamine-6G) lactamethylene-diamine and TTA = thiophentrifluoroacetone). Eu(TTA)(2)-DSQ exhibited high sensitivity in monitoring pH changes in neutral aqueous solution with negligible background fluorescence. Eu(TTA)(3)-DR1 comprised a green light emitting Rhodamine 6G fluorophore and a Eu(III) moiety as the origin of red light. These pH-sensitive emitter components have pK(a) values of 5.0 and 7.2 respectively, and exhibit isolated protonated steps within one molecule. Luminescence titrations demonstrate that Eu(TTA)(3)-DR1 was able to detect pH values at both near neutral pH and acidic pH ranges, and was also able to detect pH in both cultured cells and in vivo.

New aminonaphthalimide imidazolium podands, which worked as luminescence chemosensors for selectively sensing nucleoside polyphosphates through a "turn-on" manner, were prepared for fluorescent imaging of ADP and ATP in living cells.

A new Rhodamine-based chemosensor RBSN designed for the selective detection of Hg(2+) in aqueous media is synthesized and structural characterized. It features brightness blue emission in the presence of Hg(2+) with the fluorescent detection limit for Hg(2+) in aqueous media being ppb levels and exhibits excellent Hg(2+)-specific luminescence enhancement over various competitive cations, including alkali and alkaliearth, the first-row transition metals and heavy metals. By immobilizing RBSN to the mesoporous SBA-15, a highly selective and sensitive chemosensor toward mercury cations in aqueous solution was achieved. RBSN/SBA-15 could quantitatively determinate mercury cations at ppb level in the practical environmental media, suggesting the possibility for real-time quantitative detection of Hg(2+) and the convenience for potential application in toxicological and environmental science., ((c) 2010 Elsevier B.V. All rights reserved.)

In virtue of the sulfurphilic nature of Hg(2+), three new sensors RN1, RN2 and RST1 that combine a thiophene group and one or two rhodamine choromophores, or a thiospirolactam rhodamine chromophore, were designed and prepared for the selective detection of Hg(2+) in aqueous media, respectively. These sensors all displayed good brightness and fluorescence enhancement following Hg(2+) coordination with limits of detection for Hg(2+) at the ppb level. Thus, they have the potential for distinguishing between safe and toxic levels of inorganic mercury in drinking water. RN1 exhibited chromogenic and fluorogenic selectivity over alkali, alkaline earth metals, divalent first-row transition metal ions as well as heavy metals, but the presence of Cu(2+) had a small but significant influence on the absorption detection of Hg(2+). Compared to RN1, the introduction of sufficient sulfur atoms could increase the binding capability of RST1 towards Hg(2+) relative to the sensor RN1, but decrease its Hg specific ability. The existence of some heavy and transition metal ions, such as Pb(2+), Ag(+), Cu(2+) enhance the silent absorption spectra of RST1. Spectral evidence and X-ray structural investigations of the mercury complex revealed a possible 1:2 complexation behaviour between the Hg(2+) ion and the sensor RN1 or RST1. Sensor RN2 which contains two rhodamine carboxhydrazone arms exhibited better selectivity, compared to those of RN1 and RST1. The addition of Cu(2+) only caused a small interference for the absorption detection of Hg(2+) under the same conditions, demonstrating the efficiency of the robust bis-chelating mode with regard to the selectivity for Hg(2+).

By combination of a sugar group and a rhodamine group into one molecule, a bright and specific fluorescent sensor for Hg(2+) in natural water and living cells was achieved. RG1 features the high quantum efficiency for a Hg(2+)-bound sensor in natural water and sensitivity to environmentally relevant mercury in complex natural samples. The limit of detection of Hg(2+) of 1 ppb level suggests that RG1 is capable of distinguishing between the safe and toxic levels of inorganic mercury in drinking water. RG1 also establishes excellent Hg(2+)-ion specificity over alkali-, alkaline-earth metals and the first-row transition metals as well as Pb(2+) and Ag(+). Investigation on the fluorescence imaging of Hg(2+) in living cells demonstrates that RG1 might be used for monitoring Hg(2+) within biological samples.

Cells are generally labeled during in vivo implantation studies enabling the cells to be traced. The relationship between the labeling efficiency and cellular proliferation after transplantation is critical for the interpretation of data obtained by detection of the signals on tissue sections. Here, we compare cellular labeling methods of rat marrow stromal cells that were labeled with 5-bromo-2-deoxyuridine (BrdU), 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI) and fluorescence in situ hybridization (FISH). Our data show that (i) BrdU uniformly labeled the nuclei, (ii) DiI-labeled cells had many dots or stained clear and uniform when a longer exposure time was used during detection and (iii) FISH labeled the cells with dots along the edges of the nuclei. The labeling efficiency was 94.1+/-8.6%, 97.6+/-3.4% and 90.5+/-3.0%, in BrdU, DiI- and FISH-labeled cells, respectively. After sub-culturing of labeled cells, the percentage of BrdU-positive cells was found to be 71.9+/-18.0% and 18.4+/-6.9%, after the first and second passages, respectively. The percentage of DiI-labeled cells detected depended on the exposure time: a long exposure time (>10 s) resulted in identification of 95.1+/-4.0% and 94.5+/-3.9% DiI-positive cells after the first and second sub-cultures, respectively. The percentage of FISH-positive cells was found to be 87.0+/-3.0% and 89.1+/-9.7%. The BrdU labeling signal quickly decreased over time. Thus, BrdU should only be used to temporarily label dividing cells. In contrast, our data indicate that DiI and FISH labeling may be used to steadily trace cells during in vivo experiments. To our knowledge, this is the first time that the effects of different labeling methods over time have been examined during a cell transplantation study.

A new Cu2+ compound Cu- NB, (where H2 NB is bis(2-hydroxyl-naphthalene-carboxaldehyde) benzil dihydrazone) was synthesized as a highly selective fluorescence chemosensor for the detection of Hg2+ in aqueous media through a displacement "turn-on" signaling strategy. Whereas the coordination of Cu2+ resulted in a considerable quenching of the typical luminescence of the naphthol rings in Cu-NB, the addition of Hg2+ ion led to a dramatic increase in the emission intensity of Cu-NB at about 530 nm (excitation at 430 nm). The competitive fluorescent experiments showed that alkali, alkaline earth metal ions, the group 12 metals Zn2+, Cd2+, the first-row transition-metal ions such as Mn2+, Fe2+, Co2+, and Ni2+, as well as Pb2+ could not inhibit the Hg2+-binding fluorescent enhancement. It is postulated that the existence of Cu2+ in the luminescent probe Cu-NB could turn away the interferences of other metal cations from Hg2+ detection. The optical responses of the free ligand upon addition of Cu2+ ion, and of the Hg-H2NB compound upon the addition of Cu2+ were also investigated for comparisons.

A highly sensitive fluorescent probe 1 for selective detection of Hg ion in mixed N,N-dimethylformamide aqueous media was designed and prepared by incorporating the well-known Rhodamine 6G fluorophore and a carbohydrazone binding unit into one molecule. The fluorescent probe 1 can detect the parts per billion level of HgII in a mixed aqueous environment and displays a highly selective response of fluorescence enhancement toward HgII.

In this paper, the binding characteristics of human serum albumin (HSA) and m-nitrophenylfluorone (m-NPF)-molybdenum (Mo(VI)) complex have been studied by fluorophotometry. The binding constants are measured at different temperature. Based on the theory of Forster energy transfer, the binding distance and the energy transfer efficiency between m-nitrophenylfluorone-Mo(VI) complex and protein are obtained. According to the thermodynamic parameters, the main sort of binding force can be judged. The results indicate that HSA and m-NPF-Mo(VI) complex have strong interactions. The mechanism of quenching belongs to static quenching and the main sort of binding force is electrostatic gravitation.