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Graphical abstract Highlights • The NLO property of a new octupolar compound was studied through HRS measurement. • The influence of weak absorption induced fluorescence on the HRS was considered. • A facile data processing method was proposed and validated to remove the influence. Abstract A new octupolar compound 2,4,6-tris{4-[4-(dibutylamino)phenylethynyl]phenyl}-1,3,5-triazine was synthesized and characterized. The first hyperpolarizability β of it has been investigated by Hyper-Rayleigh scattering (HRS) measurements. A facile data processing method was proposed to eliminate the influence of the relatively weak three-photo-absorption induced fluorescence (3PF) irradiated by laser beam at λ = 1500 nm. The values of β (1500) and β 0 (1500) are close to those obtained at λ = 1600 nm laser beam at which no multi-photon-absorption induced fluorescence is detected, validating this method. This method is useful for the investigation of the first hyperpolarizability β with weak absorption induced fluorescence. [ABSTRACT FROM AUTHOR]

Fluorescent thermometers display great advantages over conventional analytical methods in terms of its high sensitivity, fast response, simple operation, high spatial resolution, non-destructive inspection, as well as potential bioimaging applications. It has emerged as an effective analytical tool particularly for applications in large surface area, microfluids and biological systems. This review focuses on the recent research progress of fluorescence thermometers based on organic materials, including organic small molecules, macromolecules, and nanoassemblies. The importance of the thermometers, design principles, fluorescence response modes, as well as their biological applications are all thoroughly described in this review. Finally, the sensing performances of thermometers are analyzed highlighting the challenges which need to be addressed urgently and future directions in design and application of organic fluorescent thermometers. [ABSTRACT FROM AUTHOR]

Salen demonstrates aggregation-induced emission (AIE) effect in aqueous solution and solid state with green fluorescence (salen = N , N ′-Ethylenebis(salicylimine)). The reaction of salen with Al 3+ results in [Al(salen)(H 2 O) 2 ] + directly. [Al(salen)(H 2 O) 2 ] + exhibits an obvious assembly phenomenon: monomer exists in organic solution with blue fluorescence while self-assembly polymer forms in aqueous solution and crystal state emitting green fluorescence, we rename it as Restriction of Coordinated Water Motions (RCWM) effect. Moreover, the self-assembly of [Al(salen)(H 2 O) 2 ] + has been observed in different part of cells: green fluorescence in hydrophilic region and blue fluorescence in hydrophobicity region in the same time. The photophysical processes are verified by fluorescence spectra, ESI–MS, X-ray diffractometer. ESIPT effect of salen and fluorescence spectra of [Al(salen)(H 2 O) 2 ] + have been certified by theoretical calculation. Therefore, salen and [Al(salen)(H 2 O) 2 ] + can act as an ideal model for the combination of organic AIEgen and metal complex self-assembly both in aqueous solution and crystal state. [ABSTRACT FROM AUTHOR]

Direct detection of picric acid in water samples is very important for social security and environmental protection. Herein, a novel donor-acceptor type fluorophore 3-(benzyloxy)-2-(4-(di-p-tolylamino)phenyl)-4 H -chromen-4-one has been designed, and synthesized. Due to its aggregation-induced emission enhancement characteristic, this fluorophore showed a very strong fluorescence in water. This fluorophore was then employed as highly sensitive chemosensor for picric acid, with a limit of detection of 370 nM in water. Moreover, this sensor showed very high selectivity towards picric acid among interfering nitroaromatics. At last, the sensing mechanism was carefully studied by using DFT computation and NMR spectra. This work provided a practical and reliable detection method for picric acid in water samples. [ABSTRACT FROM AUTHOR]

Three naphthol Schiff base-type fluorescent sensors, 1,3-Bis(2-hydroxy-1-naphthylideneamino)propane (L1) , 1,3-Bis(1-naphthylideneamino)-2-hydroxypropane (L2) and 1,3-Bis(2-hydroxy-1-naphthylideneamino)-2-hydroxypropane (L3) , have been synthesized. Their recognition abilities for Al 3 + are studied by fluorescence spectra. Coordination with Al 3 + inhibited the C N isomerization of Schiff base which intensely increase the fluorescence of L1 – L3 . Possessing a suitable space coordination structure, L3 is a best selective probe for Al 3 + over other metal ions in MeOH–HEPES buffer (3/7, V/V, pH = 6.6, 25 °C, λ em = 435 nm). A turn-on ratio over 140-fold is triggered with the addition of 1.0 equiv. Al 3 + to L3 . The binding constant K a of L3- Al 3 + is found to be 1.01 × 10 6.5 M − 1 in a 1:1 complex mode. The detection limit for Al 3 + is 0.05 μM. Theoretical calculations have also been included in support of the configuration of the L3- Al 3 + complex. Importantly, the probe L3 has been successfully used for fluorescence imaging in colon cancer SW480 cells. [ABSTRACT FROM AUTHOR]

Wash-free imaging methods can simplify the experimental procedures and facilitate the continuous observation of the targets by eliminating washing process. In this work, we present a flavonoid-based light-up bioprobe with intramolecular charge transfer characteristics. The probe could be easily synthesized by the methylation of its flavone derivative, which was initially prepared via the Claisen-Schmidt condensation and Algar-Flynn-Oyamada reaction. The probe possessed a large Stokes shift, positive solvatochromism, high photostability, high tolerance for metal ions, and light-up fluorescence properties towards protein and tissue lysate. Moreover, the signal-to-noise ratio of fluorescence bioimaging in living cells and zebrafish by using this probe could reach 4–15 without washing process, providing a new candidate for efficient wash-free imaging method in vivo . [ABSTRACT FROM AUTHOR]

Many rhodamine B probes for metal ions and anions showing “orange” fluorescent have attracted a tremendous amount of attention. Herein a rhodamine B-based fluorescent probe 1 showing “green” fluorescence emission in the presence of Hg 2+ was first reported. Self-assembled aggregation was proved to be the crucial factor for the green emitting fluorescence by means of resonance light scattering spectra, fluorescence spectra, ESI mass spectral analysis and SEM image. The probe 1 was developed as a excellent Hg(II)-selective green fluorescence agent in ethanol/HEPES buffer media (v/v = 3:7, pH 7.3) with a detection limit of 0.09 μM. Meanwhile, the green fluorescence of 1 -Hg 2+ can be quenched severely by Cys but not for GSH, S 2− , SO 4 2− , SO 3 2− , CN − , CO 3 2− and HCY. The sequential switching effect for Hg 2+ and then Cys has been achieved in aqueous media and bioimaging with satisfactory results. [ABSTRACT FROM AUTHOR]

Two structurally similar columnar ZnII-MOFs {[Zn8L4(TZ)4·0.5H2O]·4[Me2NH2]·6DMF·4H2O}n (Zn-MOF1) and {[Zn4L2(MT)2·H2O]·2[Me2NH2]·4DMF·4H2O}n (Zn-MOF2) were synthesized with irregular ligands, 2,2′-(pyridine-2,6-diyl) diterephthalic acid (H4L), 1,2,4-triazolium (TZ) and 1H-1,2,4-triazole-3-thiol (MT). Structural studies showed that both ZnII-MOFs had a similar 3D framework constructed with multiple SBUs and displayed an unusual (3,4,6)-connection topology. Furthermore, both ZnII-MOFs have high performance in gas adsorption and separation. The separation ratios of C2H2/CH4 and CO2/CH4 of Zn-MOF1 were 15.1 and 6.8, respectively, and those of Zn-MOF2 were 14.6 and 6.5, respectively. Moreover, Eu@Zn-MOF1 and Eu@Zn-MOF2 were successfully obtained by adding Eu3+ ions to the synthesis system. After a series of fluorescence tests, these two MOFs were found to have good fluorescence performance, and showed high selectivity and sensitivity to Fe3+ ions in aqueous solution with a low detection limit. [ABSTRACT FROM AUTHOR]

Multifunctional magnetite@silica-fluorescein isothioxylate- g-poly(dimethyl amino ethyl methacrylate) (FeO@SiO-FITC- g-PDMAEMA) tri-layer microspheres with magnetism, fluorescence, and pH-responsive PDMAEMA shell were designed and prepared. The functional PDMAEMA brush was grafted from FeO@SiO-FITC nanoparticles by the surface-induced atom transfer radical polymerization (SI-ATRP) onto the alkylbromide-modified FeO@SiO-FITC fluorescent templates, which were synthesized by the co-precipitation of Fe(II) and Fe(III) under basic condition together with the subsequently modified Stöber sol-gel technique. These nanoparticles were characterized by transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), fluorescence spectrum, dynamic light scattering (DLS), and zeta potentials. [ABSTRACT FROM AUTHOR]

Highlights: [•] First aptasensor based on SAMs’ interfacial energy transfer was reported. [•] High quenching efficiency of GO and SAMs’ concentration lead to higher sensitivity. [•] SAMs is easily designed and reduces the labor for the labeling of aptamer to QDS. [•] This universal and simple platform has the potential for sensitive biosensing. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new series of dicyanoisophorone fluorophores with different donor groups have been synthesized and their photophysical properties have been studied. • The fluorescent probe with p -dimethylamine and o -hydroxyl group exhibited the best sensing ability to human serum albumin. • The sensing mechanism was studied by Job's plot, replacement experiment, and molecular docking. • The fluorescent probe is capable of determination of albumin in real serum and urine samples. It is urgently needed to develop NIR-fluorescent probe for detection of human serum albumin (HSA) since the interference of short-wavelength-fluorescence from endogenous species in real serum and urine. However, most previous reports were located in the short-wavelength region (<600 nm). In this work, a series of dicyanoisophorone (DCO)-based fluorophores 1 – 4 with different donor groups have been designed and investigated. A systematic study of their photophysical properties has been carried out. Among these probes, 4 exhibited NIR emission with the highest fluorescence brightness and the most sensitive signal response to HSA. Further studies demonstrated that 4 could strongly bind into the DS1 pocket of HSA with a 1:1 ratio. Importantly, the method based on 4 has been proven to be capable of sensing HSA in real serum and urine samples. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel flavonoid probe is reported for fluorescence discrimination of HSA from BSA. • The sensing mechanism was studied by Job's plot, site-displacement experiment, and molecular docking. • The specific response to HSA was attributed to the albumin-induced restricted intramolecular rotation of flavonoid probe. Discrimination of human serum albumin (HSA) from bovine serum albumin (BSA) based on the fluorescence probe technique is still challenging due to similar chemical structures. In this work, a novel flavonoid-based fluorescent probe AF is reported for successful discrimination of HSA from BSA. The sensing performances of probe, including sensing dynamic, sensitivity and selectivity, have been carefully studied. Moreover, sensing mechanism was elucidated by Job's plot, displacement experiment, and molecular docking, suggesting that the specific response to HSA originated from the albumin-induced restricted intramolecular rotation (RIR) of probe. This work may provide a simple way for designing of novel probes for HSA with high selectivity. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, two types of salicylate Cr(III) complexes [Cr(SA)2(en)]TBA·H2O (I) and [Cr(SA)(en)2]Br·H2O (II) have been synthesized (TBA=Tetrabutylammonium, SA=salicylate, en=ethylenediamine) and determined by X-ray crystallography. Then competition reaction with ethylenediamine-N,N,N′,N′-tetraacetic acid (EDTA) or apoovotransferrin (apoOTf) was monitored by UV–Visible and fluorescence spectra at 37°C. It indicated that decomposition rate of k (I) is smaller than k (II). In the reaction with apoOTf, the releasing salicylate ligands will further be combined to OTf along with the serious fluorescence quenching of salicylate. [Copyright &y& Elsevier]

Abstract: Two naphthalimide-based turn-on chemosensors were designed and synthesized. These sensors exhibited high sensitivity and selectivity for Cu2+ over other cations. In addition, two different emission channels emerged in a diaminomaleonitrile derivative when the sensor was exposed to different concentration of copper cation in acetonitrile solution. The recognition process in the first channel involves the blocking of the photo-induced electron transfer when imine and amine groups coordinated to the first copper ion, whereas electron-withdrawing ability of the imine group might be enhanced via nitrile group binding with the second copper ion. This gave a cautionary change in fluorescence emission in both intensity and color in response to the concentration change of Cu2+. [Copyright &y& Elsevier]

Abstract: Fluorescent dye Acridine Orange (AO) was indirectly assembled onto the surface of colloidal gold nanoparticles modified quartz and gold wafer, with cysteine as mediation. Strong fluorescence emission was observed from AO self-assembled multilayers. Formation of the self-assembled multilayers was confirmed and primarily characterized by electrochemical and fluorescence methods. The effect of assembling substrate on fluorescence intensity of the film was discussed. The self-assembled multilayers offer a high sensitive interfacial fluorescence sensing of deoxyribonucleic acid with the detection limit of 7.145×10−9 gL−1 (3S.D./K), which was five orders of magnitude lower than that of the bulk solution-phase. The self-assembled multilayers film has higher stability and good regeneration capacity. [Copyright &y& Elsevier]

Abstract: Methods for real time, highly selective and sensitive polynucleotide detection are of vast scientific and economic importance. Fluorescence resonance energy transfer (FRET)-based assays which take advantage of the collective response of water-soluble conjugated polymers (CPs) and the self-assembly characteristic of aqueous polyelectrolytes have been widely used for the detection of DNA, RNA, protein and small molecules. The detection sensitivity of CP-based biosensor is dependent on the signal amplification of dye emission upon excitation of CP relative to that upon direct excitation of the dye. Using cationic polyfluorene derivatives and chromophore (fluorescein or Texas Red) labeled single-stranded DNA molecules (ssDNA-C*) as donor/acceptor pairs, we show that in addition to the spectral overlap, orientation and distance between the donor and the acceptor, the energy levels and fluorescence quenching of the donor/acceptor within the polymer/DNA-C* complexes are also important factors that affect the signal output of dye emission. [Copyright &y& Elsevier]

Abstract: Fluorescent reagent sodium 1-naphthylamine diacetate was assembled onto quartz wafer surface via its electrostatic interaction with cysteine that was directly assembled on gold nanoparticles adsorbed at quartz surface. Formation of the self-assembled bilayers was confirmed and primarily characterized by absorption and fluorescence spectra. Strong fluorescence was observed from the quartz surface and was found highly efficiently quenched by Cu2+ that allowed for a highly sensitive detection of Cu2+. [Copyright &y& Elsevier]

Cationic water-soluble poly(fluorene-co-phenylene)s with electron withdrawing or donating substituents on the conjugated backbone were designed and synthesized. Fluorescence resonance energy transfer (FRET) experiments between these conjugated polymers and dye-labeled single-stranded DNA (ssDNA-C*) reveal the importance of matching donor and acceptor orbital energy levels to improve the sensitization of C* emission. Quenching of polymer fluorescence with ssDNA-C* and differences in C* emission suggest involvement of photoinduced charge transfer (PCT) as an energy wasting mechanism. The HOMO and LUMO energy levels of the conjugated polymers and C* serve as a preliminary basis to understand the competition between FRET and PCT. Dilution of C* in polymer/ssDNA-C* complexes by addition of ssDNA yields insight into C*...C* self-quenching. Under optimized conditions, where there is no probe self-quenching and minimum PCT, efficient signal amplification is demonstrated despite poor spectral overlap between polymer and C*. [ABSTRACT FROM AUTHOR]

Fluorescent reagent sodium 1-naphthylamine diacetate (NADA) was assembled onto gold electrodes via its electrostatic interaction with cysteine (Cys) that was directly assembled on the gold electrode surface. Formation of the self-assembled bilayers was confirmed and primarily characterized by cyclic voltammetry and X-ray photoelectron spectra (XPS). The Cys modification of the gold electrode prevented direct adsorption of NADA onto the gold electrode and hence eliminated fluorescence quenching by gold. Strong fluorescence was observed from the NADA self-assembled bilayers at gold surface and was highly efficiently quenched by Cu2+ that allowed for an extremely highly sensitive detection of Cu2+ with a detection limit of 0.2 ppt and quantitative detection range of 0.5–9 ppt. The fluorescence from NADA/Cys/Au can be easily regenerated and therefore the present report showed a reusable method for immobilizing reagent in fabricating fluorescent chemosensors. [Copyright &y& Elsevier]

Au/Ag alloy@SiO2 core–shell nanoparticles (Au/Ag@SiO2 CSNs) can be applied in fields of catalysis and biosensor, because of the advantages, such as high stability, good biocompatibility, and tunable plasmonic properties. However, a few studies have been made to synthesize Au/Ag@SiO2 CSNs. There is no systematic research about the dependence of metal-enhanced fluorescence (MEF) and surface-enhanced Raman scattering (SERS) enhancement on the composition of Au/Ag@SiO2 CSNs. Here, we successfully prepared Au/Ag@SiO2 CSNs with various Au to Ag molar ratios using a facile one-pot approach. We systematically investigated the influence of the composition of Au/Ag@SiO2 CSNs on their MEF and SERS properties using crystal violet (CV) as fluorescence and Raman molecule. The MEF and SERS enhancement improves as the Ag proportion in Au/Ag@SiO2 CSNs increases. The current research provides a facile method to fabricate Au/Ag@SiO2 CSNs and promotes their potential applications in MEF-SERS dual-mode detection and imaging. [ABSTRACT FROM AUTHOR]

MiR-451a is a biomolecule tightly related to resistance development during treatment with selective estrogen-receptor modulators for breast cancer. Accurately and sensitively monitoring its level in cells is of great significance for the drug selection and the evaluation of this cancer. However, the commonly obtainable ssDNA probe cannot efficiently enter the cell to sensitively emit reliable signals by avoiding nuclease digestion. Herein, a sensing system is reported to monitor miR-451a in living cells with high specificity and sensitivity. The system consisted of reduced graphene oxide (rGO), duplex-specific nuclease (DSN), and a fluorescence-labeled ssDNA nanoprobe. The fluorescence probe on the rGO surface provided an ultra-low background and resistance to endonuclease digestion. Duplex-specific nuclease sequentially triggered the hybridization cycle and the cleavage of ssDNA nanoprobe. The signal amplification provided a detection limit of 1 fM miR-451a using the optimal conditions with a linear range from 1 fM to 100 nM. Finally, the developed method was used to determine miR-451a in breast cancer tissue. This strategy provides a promising tool for clinical diagnosis and evaluation of miR-451a related cancer. [ABSTRACT FROM AUTHOR]

The precise identification of wood plays a vital role in protecting rare timber species. Among the various wood identification techniques, the fluorescence characteristics of Pterocarpus santalinus L.f. species have rarely been investigated. In this study, the types, number of fluorescent compounds, maximum excitation and emission wavelengths, and effects of solvent and pH were characterized by fluorescence photographs, fluorescence emission spectra and fluorescence contour spectra, respectively. The results indicate that the fluorescence of P. santalinus species is relatively strong, and the fluorescent substances extracted in different solvents exhibit different color photographs under irradiation. The spectrum is also affected by the polarity of the solvent and the pH of the solution. In addition, the method for extracting the fluorescent compounds in P. santalinus samples was optimized. Based on the reported results, a good correlation between the fluorescence characteristics and the wood species was obtained as a potentially new identification method for precious rosewoods at the species level. [ABSTRACT FROM AUTHOR]

A colorimetric and ratiometric fluorescent chemosensor for F−has been prepared, which is based on combination of desilylation reaction and excited-state proton transfer from the desilylation product to F−. The sensor exhibits rapid response, excellent selectivity and sensitivity to F−. [ABSTRACT FROM AUTHOR]

Intermolecular proton transfer from a flavonol-based probe to the arginine (Arg222) in drug site 1 of human serum albumin triggers an unusual red-shifted ratiometric fluorescence response, which can be applied in the point-to-care diagnosis of hypoalbuminemia. [ABSTRACT FROM AUTHOR]

Aggregation-induced emission (AIE) has received great attention. In this paper, Cu 2+ induced self-assembly and H 2 S induced disassembly of two aggregation–induced emission enhancement (AIEE) compounds were reported in this paper. Two salicylaldehyde azine Schiff base were synthesized and characterized. It is found that 1 and 2 are AIEE active molecular both in aqueous solution and crystal state with strong yellow fluorescence. Theirs fluorescence can be selectively quenched in the presence of Cu 2+ ions with the formation of self-assembly system [ 1-Cu 2+ ] n . The interaction mechanism has been researched by multiple means. Depending on this reaction, energy changes (ΔG) from 1 to [ 1-Cu 2+ ] n was also estimated by Scatchard formula. Moreover, the quenching fluorescence was further restored by H 2 S both in tube and live cells along with the releasing of AIEE molecular 1 . That is, a reversible process between AIEE, self-assembly and disaggregation can be found in the model compound. [ABSTRACT FROM AUTHOR]

Terminal deoxynucleotidyl transferase (TdT) is a crucial biomarker for diseases such as lymphoblastic leukemia. Herein, a pho tocatalytic co lorimetry and f luorescence dual-signal biosensor (PhoCoF-sensor) for simple, low-cost and sensitive detection of TdT was developed, which integrated with the TdT-triggered polymerization reaction and the fluorescence-photocatalytic dual performance of double-strand DNA/SYBR Green-I (dsDNA/SG-I) complex. The target TdT catalyzed the elongation of single-stranded DNA in the dTTP substrate pool, and then hybridized with complementary DNA to form dsDNA/SG-I complex that exhibited obvious fluorescent and excellent photocatalytic activity. Reactive oxygen species were generated from photosensitization of the dsDNA/SG-I complex acted as the visual colorimetric readout. The PhoCoF-sensor was successfully used to detect TdT activity with a series of color and fluorescence changes in the concentration range from 0.5 U/mL to 20.0 U/mL. The PhoCoF-sensor further improves the assay simplicity and accuracy and reduces the time and cost, which overcomes the limitations of traditional detection TdT methods and single-signal sensors. Additionally, this PhoCoF-sensor can readily be integrated with centrifugal microfluidic device for one-step test and achieve quantitative determination without sophisticated instruments. Moreover, the PhoCoF-sensor has good sensitivity and good practical reliability and is suitable for instant determination in early disease diagnosis and drug discovery. • Photocatalytic colorimetry and fluorescence dual-signal biosensor was developed. • TdT-triggered polymerization reaction without DNA/RNA template. • The dsDNA/SG-I complex has excellent fluorescence-photocatalytic dual performance. • PhoCoF-sensor well integrated with centrifugal microfluidic chip for TdT detection. [ABSTRACT FROM AUTHOR]

Highlights: [•] A sensitive and low-cost fluorescence detection system for UDG assay was constructed. [•] A fluorescence strategy for sensing UDG activity and kinetics study was proposed. [•] A low detection limit (0.005UmL−1) was obtained without any amplification. [•] The strategy can be reliably applied for quantitative assay of UDG in complicated biological samples. [ABSTRACT FROM AUTHOR]

Abstract: This paper details the fabrication of indole (ID) self-assembled multilayers (SAMs) and fluorescence interfacial sensing for organophosphorus (OP) pesticides. Quartz/APES/AuNP/l-Cys/ID film was constructed on l-cysteine modified Quartz/APES/AuNP surface via electrostatic attraction between ID and l-cysteine. Cyclic voltammetry indicates that ID is immobilized successfully on the gold surface. Fluorescence of the Quartz/APES/AuNP/l-Cys/ID film shows sensitive response toward OPs. The fluorescent sensing conditions of the SAMs are optimized that allow linear fluorescence response for methylparathion and monocrotophos over 5.97×10−7 to 3.51×10−6 gL−1 and 3.98×10−6 to 3.47×10−5 gL−1, with detection limit of 6.1×10−8 gL−1 and 3.28×10−6 gL−1, respectively. Compared to bulk phase detection, interfacial fluorescence sensing based on the SAMs technology shows higher sensitivity by at least 2 order of magnitude. [Copyright &y& Elsevier]

Ferroptosis regulates cell death through reactive oxygen species (ROS)‐associated lipid peroxide accumulation, which is expected to affect the structure and polarity of lipid droplets (LDs), but with no clear evidence. Herein, we report the first example of an LD/nucleus dual‐targeted ratiometric fluorescent probe, CQPP, for monitoring polarity changes in the cellular microenvironment. Due to the donor–acceptor structure of CQPP, it offers ratiometric fluorescence emission and fluorescence lifetime signals that reflect polarity variations. Using nucleus imaging as a reference, CQPP was applied to report the increase in LD polarity and the homogenization of polarity between LDs and cytoplasm in the ferroptosis model. This LD/nucleus dual‐targeted fluorescent probe shows the great potential of using fluorescence imaging to study ferroptosis and ferroptosis‐related diseases. [ABSTRACT FROM AUTHOR]

Ferroptosis regulates cell death through reactive oxygen species (ROS)‐associated lipid peroxide accumulation, which is expected to affect the structure and polarity of lipid droplets (LDs), but with no clear evidence. Herein, we report the first example of an LD/nucleus dual‐targeted ratiometric fluorescent probe, CQPP, for monitoring polarity changes in the cellular microenvironment. Due to the donor–acceptor structure of CQPP, it offers ratiometric fluorescence emission and fluorescence lifetime signals that reflect polarity variations. Using nucleus imaging as a reference, CQPP was applied to report the increase in LD polarity and the homogenization of polarity between LDs and cytoplasm in the ferroptosis model. This LD/nucleus dual‐targeted fluorescent probe shows the great potential of using fluorescence imaging to study ferroptosis and ferroptosis‐related diseases. [ABSTRACT FROM AUTHOR]

Tetracyclines (TCs) are a group of broad-spectrum antibiotics against multiplying microorganisms yet with several adverse effects on humans. Since all types of TCs have the similar chemical skeleton and mechanism of action, quantification of total amount of TCs in the environment was of particular importance. To date, dozens of fluorescent probes have been reported for TCs detection, but only very few of them enabled detection of total TCs. In this study, we report a novel supramolecular sensor constructed by human serum albumin as the recognition moiety and a flavonol fluorophore as the indicator. Under the 370 nm UV excitation, this sensor exhibits the rapid response (5 s), acceptable sensitivity (limit of detection ∼ 0.58 μM), long dynamic detection range (0–20 μM), prominent specificity, and excellent anti-interference properties for analysis of total TCs. The mechanism was carefully validated using 1H NMR, fluorescence titration experiments, molecular docking, and mass spectrometry. We expect this work can inspire more sensor design for TCs quantification. [Display omitted] • A novel fluorescent sensor enables detection of total amount of tetracyclines. • This method can detect tetracycline with rapid response and high selectivity. • The limit of detection for tetracyclines can reach 0.58 μM. • Accurate detection of total tetracycline in real samples is achieved. [ABSTRACT FROM AUTHOR]

Abnormal expression of alkaline phosphatase (ALP) in serum has received considerable attention in health monitoring and disease diagnosis. However, conventional optical analysis based on a single signal must compromise background interference and limited sensitivity in trace analysis. As an alternative candidate, the ratiometric approach depends on the self-calibration of two independent signals in a single test to minimize interferences from the background for accurate identification. Here, a carbon dot/cobalt-metal organic framework nanocoral (CD/Co-MOF NC) mediated fluorescence-scattering ratiometric sensor has been developed for simple, stable, and highly sensitive detection of ALP. ALP-responsive phosphate production was used to coordinate cobalt ion and collapse the CD/Co-MOF NC, resulting in the recovery of fluorescence signal from dissociative CDs and the decrease of second-order scattering (SOS) signal from the cracked CD/Co-MOF NC. The ligand-substituted reaction and the optical ratiometric signal transduction provide a rapid and reliable chemical sensing mechanism. The ratiometric sensor effectively converted ALP into a ratio signal of fluorescence-scattering dual emission throughout a wide linear concentration range of six orders of magnitude with a detection limit of 0.6 mU/L. In addition, self-calibration of fluorescence-scattering ratiometric method can reduce background interference and improve sensitivity in serum, approaching recoveries of ALP from 98.4% to 101.8%. Due to the above advantages, the CD/Co-MOF NC mediated fluorescence-scattering ratiometric sensor readily provides rapid and stable quantitative detection of ALP as a promising in vitro analytical method for clinical diagnostics. [Display omitted] • A CD/Co-MOF NC mediated fluorescence-scattering ratiometric sensor has been developed for highly sensitive detection of ALP. • Dual emission signal readout achieves self-calibration of the method to minimize interferences. • Real sample analysis was completed in a simple and rapid detection process. • The sustainable carbon dots from green source can be easily assembled for CD/Co-MOF NC. [ABSTRACT FROM AUTHOR]

The toxicity and stability of all-inorganic perovskite quantum dots are major challenge to be addressed in its commercialization process. Here, the toxicity of lead is reduced while improving the optical properties of quantum dots via replacing Pb2+ ions in CsPbBr 3 perovskites quantum dots with low-toxicity and cost-effectiveness Cu2+ cations. The PL emission and absorption peaks of quantum dots appear blue shift due to lattice shrinkage caused by copper ion doping. At the same time, we also observed that with the increase of Cu2+ doping concentration, the fluorescence lifetime of quantum dots decreased from 40.66 ns to 8.23 ns. Next, the slim CsPbBr 3 :Cu@SiO 2 core-shell QDs were synthesized via a simply one-step synthesis method. Compared with the original CsPbBr 3 :Cu QDs, the stability of the quantum dots after coated has been significantly improved. Benefiting from this effective cladding strategy, these CsPbBr 3 :Cu@SiO 2 can be well used for manufacturing high-performance perovskite LEDs. [ABSTRACT FROM AUTHOR]

Light‐up bioorthogonal probes have attracted increasing attention recently due to their capability to directly image diverse biomolecules in living cells without washing steps. The development of bioorthogonal probes with excellent fluorescent properties suitable for in vivo imaging, such as long excitation/emission wavelength, high fluorescence turn‐on ratio, and deep penetration, has been rarely reported. Herein, a series of azide‐based light‐up bioorthogonal probes with tunable colors based on a weak fluorescent 8‐aminoquinoline (AQ) scaffold were designed and synthesized. The azido quinoline derivatives are able to induce large fluorescence enhancement (up to 1352‐fold) after click reaction with alkynes. In addition, the probes could be engineered to exhibit excellent two‐photon properties (δ=542 GM at 780 nm) after further introducing different styryl groups into the AQ scaffold. Subsequent detailed bioimaging experiments demonstrated that these versatile probes can be successfully used for live cell/zebrafish imaging without washing steps. Further in vivo two‐photon imaging experiments demonstrated that these light‐up biorthogonal probe outperformed conventional fluorophores, for example, high signal‐to‐noise ratio and deep tissue penetration. The design strategy reported in this study is a useful approach to realize diverse high‐performance biorthogonal light‐up probes for in vivo studying. [ABSTRACT FROM AUTHOR]

Monitoring of human serum albumin (HSA) in a point‐of‐care fashion is urgently needed in particular for elderly or chronically ill patients. Herein, a dual‐state emissive chalcone probe having the feature of aggregation‐induced emission was designed and synthesized. The concentration of HSA can be evaluated by the ratios of emission from probes in aggregated and monomeric state, which gives a visually discernible red‐to‐green color change. A simple, portable paper‐based analytical device have been fabricated by integration of the recognition probe in the detection pad and employed for HSA test using the whole blood samples. This paper‐based assay shows the analytical capability comparable to the standard testing methods but is in a point‐of‐care fashion, providing a promising tool for at‐home HSA detection and HSA‐related disease diagnosis. [ABSTRACT FROM AUTHOR]

Monitoring of human serum albumin (HSA) in a point‐of‐care fashion is urgently needed in particular for elderly or chronically ill patients. Herein, a dual‐state emissive chalcone probe having the feature of aggregation‐induced emission was designed and synthesized. The concentration of HSA can be evaluated by the ratios of emission from probes in aggregated and monomeric state, which gives a visually discernible red‐to‐green color change. A simple, portable paper‐based analytical device have been fabricated by integration of the recognition probe in the detection pad and employed for HSA test using the whole blood samples. This paper‐based assay shows the analytical capability comparable to the standard testing methods but is in a point‐of‐care fashion, providing a promising tool for at‐home HSA detection and HSA‐related disease diagnosis. [ABSTRACT FROM AUTHOR]

We herein find that graphene oxide (GO) can enhance the fluorescence signal of conjugated polyelectrolytes (CPEs) with charge transfer characteristics under certain conditions, which is due to a relative hydrophobic environment of CPEs upon complexation with GO. [ABSTRACT FROM AUTHOR]

We report a general strategy to design and synthesize a bright far-red and near-infrared fluorescent conjugated polyelectrolyte with a high quantum yield of 25% and a large Stokes shift of ∼200 nm, which is ideal for cell imaging. [ABSTRACT FROM AUTHOR]

[Display omitted] • A dual-site fluorescent probe for detecting low and high concentration of ClO− was reported. • With the increase of ClO−, the probe showed a fluorescence change from red to green to blue. • The probe can be applied for imaging exogenous and endogenous ClO− in living cells. Hypochlorite (ClO−) is an important bioactive molecule of living system which plays essential roles in many physiological and pathological processes. There is no doubt that the biological roles of ClO− depend highly on the concentration of ClO−. Unfortunately, the relationship between the concentration of ClO− and the biological process is unclear. Toward this purpose, in this work we addressed a core challenge for developing a powerful fluorescence tool for monitoring a wide concentration change (0–14 eq.) of ClO− via two distinct detection manners. The probe displayed fluorescence variation (red to green) upon addition of ClO− (0–4 eq.) and the color of test medium changed from red to colorless witnessed by the naked eyes. Surprisingly, in the presence of higher concentration of ClO− (4–14 eq.), the probe displayed another fluorescent signal change from green to blue. After demonstrating the excellent sensing properties of the probe with ClO− in vitro, it was successfully used to imaging different concentration of ClO− in living cells. We expected that the probe could act as an exciting chemistry tool for imaging of ClO− concentration-dependent oxidative stress event in biological system. [ABSTRACT FROM AUTHOR]

As a highly conserved damage repair protein, Fpg can specifically recognize and digest 8-oxoG from a damaged DNA backbone. Meanwhile, DNAzyme, a single-stranded DNA with enzymatic activity, can cleave RNA in the presence of cofactors. In this study, we established a highly sensitive method for Fpg assay using a DNAzyme-mediated signal cascade amplification strategy. Based on the Fpg-dependent fluorescence response of the “turn-on” manner, we could reliably determine Fpg activity down to 0.14 U mL−1 with a linear response from 0.10 to 40 U mL−1 under optimal conditions. In addition, this strategy was successfully applied to analyze the kinetic parameter of Fpg with Km of 0.061 μM. Furthermore, the developed sensing system was used to screen the regulators of Fpg from natural compounds and antibiotics. These results indicated that all of the 14 natural compounds and 6 kinds of antibiotics deferentially showed an active effect on Fpg in vitro. In summary, these results show that the method not only provides an alternative for monitoring Fpg activity but also shows great potential for drug screening in the future. [ABSTRACT FROM AUTHOR]

T4 polynucleotide kinase (PNK) is the primary member of the 5′-kinase family that can transfer the γ-phosphate residue of ATP to the 5′-hydroxyl group of oligonucleotides. In this article, using the differential quenching ability of reduced graphene oxide (rGO) towards the fluorophore-labeled DNA probe, we propose a novel method for detecting T4 PNK activity assisted by ligase reaction. Under the optimized conditions, the detection limit of T4 PNK was estimated to be 0.0002 U μL−1 in the linear region of 0.001 U μL−1–0.1 U μL−1. Additionally, the developed method was used to screen regulators of T4 PNK from natural compounds. The compound f isolated from the root of Kadsura coccinea (Lem.) A.C. Smith was found to stimulate T4 PNK activity in a concentration-dependent manner in vitro. Finally, the method was used to monitor the relation of T4 PNK activity with pelvic inflammatory disease (PID). The results demonstrated that the development of this disease could inhibit T4 PNK activity to some extent. In summary, the above data indicate that the method not only provides a universal platform for monitoring T4 PNK activity, but also shows great potential to be used in drug screening and clinic diagnosis. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • An ESIPT-based fluorescent probe was reported for determination of methanol in biodiesel. • Ratiometric fluorescent response with a large chromatic shift was achieved. • The methanol-sensing mechanism has been studied by fluorescence spectra and time-resolved fluorescence decay. Abstract Developing an analytical method for monitoring methanol content in biodiesel in a rapid and precise manner is of great importance for biodiesel production quality control, due to that an excessive amount of methanol in biodiesel will accelerate the engine aging thereby affect driving safety. In this study, we reported a novel flavonoid-based fluorescent probe HOF with the excited-state intramolecular proton transfer (ESIPT) character. This study demonstrated that the alcohols could form strong intermolecular hydrogen bonds with the HOF molecules and consequently block the ESIPT process, triggering a fast and specific fluorescence response. This alcohol-sensing method was proven to be rapid, sensitive, ratiometric, and visually discernible for detection of methanol with multi-channel signal output (fluorescent wavelength, intensity, and lifetime). Moreover, this method was successfully applied for determination of methanol content in commercial biodiesel, which may provide a practical tool for real-time monitoring of biodiesel production process. [ABSTRACT FROM AUTHOR]

A label-free, ultra-sensitive and turn-off fluorescence method for detecting cysteine (Cys) has been developed using enhanced DNA-templated silver nanoclusters (DNA-AgNCs) as the fluorescence probe. The method is based on the specific interaction between Cys and DNA-AgNCs via robust Ag-S bonds and the fluorescence quenching ability of Cys to DNA-AgNCs. Using this method for Cys assay, it was found that the change of fluorescent intensity has a good linear relationship with Cys concentration in the range from 0.1 nM to 100 nM (R 2  = 0.991). The detection limit of Cys was 0.05 nM. Furthermore, the method was successfully used for the detection of Cys in human serums, the result of which was confirmed using clinical colorimetric assay. In summary, our study shows that this simple, sensitive and rapid detection method can be hopefully used for theranostics. [ABSTRACT FROM AUTHOR]

As an essential phosphate group hydrolase, alkaline phosphatase (ALP), whose level in serum is correlated with bone disease, liver dysfunction, and cancer, could be used as a biomarker for clinical diagnosis and biomedical studies. Hence, developing a convenient and sensitive method for ALP assay has importance in disease diagnosis, drug treatment, and prognosis assessment. In this work, using a hairpin DNA strand as the substrate, we developed an ultrasensitive and simple fluorescence method for quantitative ALP assay based on the binding difference of reduced graphene oxide (rGO) with different DNA strands coupled with λ exonuclease (λ exo) cleavage. Under the optimal conditions, the limit of detection (LOD) of ALP is estimated to be 0.01 U/L with the linear region from 0.5 U/L to 70 U/L. Furthermore, the proposed assay was used to detect ALP in complicated cell-free extracts and evaluate the inhibitory effects of two well-known inhibitors of ALP activity. Finally, the method was used to investigate the effect of natural compounds on ALP activity and five compounds with different inhibitory capability were screened. In summary, we propose that the new method for ALP assay can be applied for therapeutic drug monitoring (TDM) and high-throughput compound screening in combination with multiwell plate technology. [ABSTRACT FROM AUTHOR]

Abstract: Bio‐orthogonal tumor labeling is more effective in delivering imaging agents or drugs to a tumor site than active targeting strategy owing to covalent ligation. However, to date, tumor‐specific imaging through bio‐orthogonal labeling largely relies on body clearance to differentiate target from the intrinsic probe signal owing to the lack of light‐up probes for in vivo bio‐orthogonal labeling. Now the first light‐up probe based on a fluorogen with aggregation‐induced emission for in vivo bio‐orthogonal fluorescence turn‐on tumor labeling is presented. The probe has low background fluorescence in aqueous media, showing negligible non‐specific interaction with normal tissues. Once it reacts with azide groups introduced to tumor cells through metabolic engineering, the probe fluorescence is lightened up very quickly, enabling rapid tumor‐specific imaging. The photosensitizing ability was also used to realize effective image‐guided photodynamic tumor therapy. [ABSTRACT FROM AUTHOR]

Abstract: Red/near‐infrared dyes are highly demanded for biological applications but most of them are far from satisfactory. In this work, a series of red/near‐infrared fluorophores based on electron‐withdrawing benzo[1,2‐b:4,5‐b′]dithiophene 1,1,5,5‐tetraoxide (BDTO) are synthesized and characterized. They possess both aggregation‐induced emission, and hybridized local and charge‐transfer characteristics. Crystallographic, spectroscopic, electrochemical and computational results reveal that the oxidation of benzo[1,2‐b:4,5‐b′]dithiophene to BDTO can endow the fluorophores with greatly red‐shifted emission, enhanced emission efficiency, reduced energy levels, enlarged two‐photon absorption cross section, and increased reactive oxygen species generation efficiency. The nanoparticles fabricated with a near‐infrared fluorophore TPA‐BDTO show high photostability and biocompatibility with good performance in targeted photodynamic ablation of cancer cells and two‐photon fluorescence imaging of intravital mouse brain vasculature. [ABSTRACT FROM AUTHOR]

Bright and red-emissive organic nanoparticles (NPs) are demonstrated as promising for in vivo fluorescence imaging. However, most red organic dyes show greatly weakened or quenched emission in the aggregated state. In this work, a robust red fluorophore ( t-BPITBT-TPE) with strong aggregate-state photoluminescence and good biocompatibility is presented. The NPs comprised of t-BPITBT-TPE aggregates encapsulated within 1,2-distearoyl- sn-glycero-3-phosphoethanolamine- N-[methoxy(polyethylene glycol) (DSPE-mPEG) micelles exhibit a photoluminescence peak at 660 nm with a high fluorescence quantum yield of 32% in aqueous media. The NPs can be facilely charged by using the same polymeric matrix with different terminal groups, e.g., methoxy (DSPE-mPEG), amine (DSPE-PEG-NH2), or carboxymethyl (DSPE-PEG-COOH) groups. The biocompatibility, toxicity, circulation, and biodistribution of the NPs are assessed using the zebrafish model through whole embryo soaking and intravenous delivery. Furthermore, HeLa and MCF-7 cells tagged with t-BPITBT-TPE in DSPE-PEG-NH2-TAT polymer NPs are xenografted into zebrafish larvae to successfully track the cancer cell proliferation and metastasis, demonstrating that these new NPs are efficient cancer cell trackers. In addition, the NPs also show good in vivo imaging ability toward 4T1 tumors in xenografted BALB/c mice. [ABSTRACT FROM AUTHOR]

Mung bean nuclease is a single stranded specific DNA and RNA endonuclease purified from mung bean sprouts. It yields 5′-phosphate terminated mono- and oligonucleotides. The activity level of this nuclease can act as a marker to monitor the developmental process of mung bean sprouts. In order to facilitate the activity and physiological analysis of this nuclease, we have developed a biosensing assay system based on the mung bean nuclease-induced single-stranded DNA scission and the affinity difference of graphene oxide for single-stranded DNA containing different numbers of bases. This end-point measurement method can detect mung bean nuclease in a range of 2×10 −4 to 4×10 −2 with a detection limit of 1×10 −4 unit/mL. In addition, we demonstrate the utility of the assay for screening chemical antibiotics and metal ions, resulting in the identification of several inhibitors of this enzyme in vitro . Furthermore, we firstly report that inhibiting mung bean nuclease by gentamycin sulfate and kanamycin in vivo can suppress mung bean sprouts growth. In summary, this method provides an alternative tool for the biochemical analysis for mung bean nuclease and indicates the feasibility of high-throughput screening specific inhibitors of this nuclease in vitro and in vivo . [ABSTRACT FROM AUTHOR]

An AIE-active “turn-on” bioprobe is designed for hydrogen peroxide detection based on an imine-functionalized tetraphenylethene derivative. The linear fluorescence response enables quantification of hydrogen peroxide with superior sensitivity and selectivity. Meanwhile, glucose assay is also realized by taking advantage of GOx/glucose enzymatic reaction. [ABSTRACT FROM AUTHOR]

[Display omitted] • A surfactant-assisted fluorescent method is reported for sensitive detection of benfluralin herbicide in water with a LOD of 80 nM. • The role of surfactant on signal amplification has been carefully studied by the polarity-dependent DFT calculation. • The sensing properties including response time, sensitivity, selectivity, and anti-interference ability, have been fully studied. • This surfactant-assisted method enables the fluorescent monitoring of benfluralin in living plants. Developing an effective detection method for benfluralin (BFA) is of great significance, since BFA as most widely used herbicides can be bioaccumulated by aquatic organisms in environment, possessing potential risks to human health. Owing to aggregation-caused quenching effect, most fluorescent detection methods based on donor–acceptor organic fluorophores suffered from very low sensitivity towards BFA in water system, hampering the bioimaging application in plants. In this work, we reported a novel surfactant-assisted fluorescent probe enabling detection of BFA in water with a high sensitivity. The involvement of specific surfactant Triton X100 (TX100) could amplify the response signal of probe more than 100-fold. The detection limit for BFA was determined to be 80 nM, satisfying the environmental protection requirements. Moreover, we demonstrated applications of this strategy for the fluorescent imaging of BFA in plant. The absorbance of BFA into roots of Arabidopsis thaliana and castor seedlings was successfully observed based on this method. [ABSTRACT FROM AUTHOR]