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The typical aza-BODIPYs in the dye family are known for bright fluorescence, excellent stability, and tunable absorption wavelengths. Hence, these dyes are attracting the increasing attention. Aza-BODIPYs having the maxima absorption in the near-infrared (NIR) region (650–900 nm) are very favorable for bioimaging in vivo due to the less photo-damage, deeper tissue penetration, and less interference from background auto-fluorescence by biomolecules in the living systems. Many strategies have been employed to modify the structures of the aza-BODIPY core to provide the NIR absorbing dyes. Among these, the most effective method is the fusion of the aromatic rings in aza-BODIPY system. This review allsidedly summarizes the recent development of ring-fused aza-BODIPY dyes (λabs> 700 nm) focusing on the design, synthesis, and potential applications in the NIR region since 2002.

Fluorescence bioimaging through the second near-infrared window (NIR-II, 1000-1700 nm) has attracted much attention due to its deep penetration and high contrast. However, exploring new fluorescent materials, especially small molecular fluorophores with long wavelength and high brightness, is still quite challenging. By expanding π-conjugation and enhancing the intramolecular charge transfer effect, herein we report a series of new xanthene-based NIR-II dyes, named VIXs. Among these dyes, VIX-4 exhibits the best performance with fluorescence emission at 1210 nm and high brightness and has been used for dynamically imaging the blood flow of mice at 200 fps. By virtue of high spatiotemporal resolution of the dynamic imaging, we can distinguish directly the artery and vein through the blood flow direction and measure the blood flow volume by the videos. This study provides not only an effective tool for high spatial and temporal resolution bioimaging but also a new and promising conjugated skeleton for NIR-II dyes.

A series of probes KJ-x (x = 1−3) with carbon chains of different lengths based on the matrix of rhodamine B were engineered to detect Ag+ in aqueous solution in this work. Among them, KJ-1 is selected as the best option after in vitro investigation in view of its most sensitive and rapid response to Ag+, whose possible sensing mechanism is studied by experimental investigation and theoretical calculation. To identify the practical application of the probe, the detection of Ag+ in nonantibiotic fungicide Silver&Health and differentiation between normal hepatocytes and hepatoma cells using confocal imaging was conducted.

In this paper, a co-doped cubic phase submicron particles Ba2LaF7:Yb3+/Ln3+ (Ln = Er3+,Ho3+) up-conversion material were successfully synthesized by hydrothermal method. By adjusting PH, time, temperature, and the amount of sodium citrate during the preparation process, it was possible to analyze and obtain the phase structure, morphology, and up-conversion luminescence characteristics of the particles. Furthermore, the influence of doping concentration on the up-conversion luminescence characteristics was studied using X-ray diffractometer (XRD), scanning electron microscopy (SEM), fluorescence spectroscopy, and other characterization methods. The test results show that, under the conditions of pH = 9 and NaBF4 as the fluorine source, Ba2LaF7:Yb3+/Ln3+ (Ln = Er3+,Ho3+) spherical particles have an average size of 240 nm. Under the excitation of a 980 nm laser-diode (LD) laser, it was found that the material spectrum is mainly composed of strong green and weak red light. When Yb3+ and Er3+ doping concentrations are 18% and 2.5%, Yb3+ and Ho3+ doping concentrations are 18% and 3.5%, respectively, the up-conversion transmittance is the highest. Finally, the possible causes of the fluorescence decay curve of Ba2LaF7:Yb3+/Ln3+ (Ln = Er3+,Ho3+) up-conversion materials were investigated.

For achieving smart materials with color-tunable emissions, the development of single-component systems exhibiting high durability and stability is desired but remains challenging, in comparison to multicomponent systems. Here, a single-component luminescent molecule (3-SPhF) with colorful emissions is successfully reported through different expressions of triplet excitons in radiative transitions. The time-resolved spectra confirm the existence of delayed fluorescence (τ = 282.5 μs), monomeric phosphorescence (τ = 497.7 ms) and aggregated-state phosphorescence (τ = 230.0 ms) in the crystal powder of 3-SPhF, which affords time-dependent afterglow and excitation-dependent emissions in a steady state. Furthermore, the relationships between ultra-long luminescence and stacking of the dibenzofuran group in single crystals are explored, providing evidence for the regularity of multiple emission centers in single-component compounds with dibenzofuran substituents., Color tunable luminescent materials with multiple emission centers showing delayed fluorescence, single molecular phosphorescence and aggregated molecular phosphorescence are achieved, along with time-dependent and excitation-dependent properties.

Soluble forms of aggregated tau misfolded protein, generally termed oligomers, are considered to be the most toxic species of the different assembly states that are the pathological components of neurodegenerative disorders. Therefore, a critical biomedical need exists for imaging probes that can identify and quantify them. We have designed and synthesized a novel fluorescent probe, pTP-TFE for which binding and selectivity profiles towards aggregated tau and Aβ proteins were assessed. Our results have shown pTP-TFE to be selective for early forms of soluble tau aggregates, with high affinity of dissociation constants (Kd) = 66 nM, and tenfold selectivity over mature tau fibrils. Furthermore, we found that pTP-TFE is selective for tau over Aβ aggregates and had good cell permeability. This selectivity of pTP-TFE towards early forms of aggregated tau protein ex vivo was also supported with studies on human brain tissue containing tau and Aβ pathology. To the best of our knowledge, this is the first fluorescent molecule to be reported to have this form of selectivity profile, which suggests that pTP-TFE is a unique probe candidate for imaging-based detection of early stages of Alzheimer's disease and other tauopathies., pTP-TFE imaging probe can distinguish soluble tau aggregated proteins from other aggregated proteins enabling earlier detection of neurodegenerative diseases.

In this work, novel β-cyclodextrin-enhanced Eu3+ luminescence aggregates (CELAs) with bright red fluorescence of Eu3+ are prepared. These CELAs exhibit the quick response and highly selective sensitivity at the concentration of 50 µM Fe3+. A series of ligands (such as TTA, phen, β-cyclodextrin) sensitizes the luminescence of Eu3+ (the “antenna effect”), and metal ions–ligands interactions can differentially alter the antenna effect of ligands toward Eu3+. Addition of EDTA to chelate Fe3+ restores the fluorescence, indicating that the fluorescence quenching in the presence of Fe3+ is reversible. This research provides that CELAs integrate these merits of superior lanthanide fluorescence and the amphiphilia property of β-cyclodextrin (β-CD). It is a unique system with enhancement Eu3+ luminescence in ethanol–water system and will be applied for aqueous solution detection sensor with high selectivity and reversibility for Fe3+. On the other hand, the on-off fluorescence property of the CELAs is convenient for environmental detection system.

Versatile species have been increasingly recognized as important components and possible fluorescence origins in carbon dots synthesized via a bottom-up route. Herein, we use 2,7-naphthalenediol an...

White-light-emitting materials have attracted significant attention due to their broad applications in displays and lighting. Herein, a quadruple-stranded helicate with white-light emission was constructed by co-assembly of bis-β-diketone featuring cyan fluorescence and red light emitting Eu3+ ions in a 2 : 1 stoichiometric ratio. The cyan emission from bis-β-diketone originated from the pendent tetraphenylethylene (TPE), a typical AIE molecule featuring strong emission in the aggregation state. The formation of the helicate was verified by 1H NMR, 1H DOSY and high-resolution MS analyses. Upon excitation at 390 nm, the helicate realized the tunable emission with the colors changing from white light to green in the solid state. After hybridization with a polymer, a white-light hybrid material was prepared with the CIE coordinate locating at (0.322, 0.332). The absolute luminescence quantum yields were measured to be 16.9%.

In this paper, a high sensitivity and accuracy biosensor for CEA detection based on atom transfer radical polymerization (ATRP) with β-cyclodextrin (β-CD) and 2-bromoisobutyryl bromide (BIBB) as a macroinitiator is reported for the first time. Carcinoembryonic antigen (CEA), as a tumor-associated antigen, can be of great significance in the diagnosis of illness. Herein, thiolated CEA-aptamer 1 (Apt 1) at the 5′-terminal is first immobilized on amino magnetic beads (MBs) via a cross-linking agent to specifically recognize the antigen of CEA. After the sandwich-type structure formed, β-CD, with a bridging effect, is linked to the carboxylation CEA-aptamer 2* (Apt 2*) and BIBB via esterification reaction and substitution reaction, respectively. Remarkably, the combination of β-CD and the initiators BIBB can provide a large number of active sites for monomers and significantly amplify the fluorescent signal. Under optimum experimental conditions, the proposed biosensor for detecting CEA has a strong linear relationship in the wide detection range of 1.0 × 10−15–1.0 × 10−7 g mL−1 (R2 = 0.9989), and it is capable of detecting as low as 6.76 ag mL−1 CEA. Furthermore, the fluorescence biosensor exhibits splendid analytical performance in practical sample analysis. More importantly, the excellent sensitivity with outstanding anti-interference properties of this proposed biosensor makes it of great potential in the field of bioanalytical applications.

Apoptosis plays an essential role in a multicellular organism's lifecycle. Developing technologies for selectively monitoring apoptotic processes can be useful not only in the evaluation of disease progression, but also in the assessment of their therapeutic intervention. However, quantitative imaging of cell apoptosis is still a challenge. In this work, we reported a cell-permeable peptide probe with a ratiometric fluorescence response specifically toward caspase-3, a key enzyme for the execution of apoptosis. This probe Ac-Tat-DEVD-CV consisted of a caspase-3 recognition sequence Asp-Glu-Val-Asp (DEVD), a cell-penetrating peptide Tat (RKKRRORRR), and a long wavelength fluorophore, cresyl violet (CV). Upon selective hydrolyzation by caspase-3, the probe released CV and displayed a ratiometric change in fluorescence. Facilitated by the cell-penetrating peptide, this probe can easily internalize into cells. The ratiometric response property bestowed the probe with advantages in the real-time quantification of caspase-3 activity, thus estimating the apoptotic stages in living cells. This method could offer opportunities to evaluate apoptosis-related disease progression and therapeutic monitoring.

Peroxynitrite (ONOO–), a powerful biological oxidant, is produced in the mitochondria and reacts with many biomolecular targets under various pathological conditions, leading to a range of disease ...

Developing anti-counterfeiting technique with rich information encrypted by cheap, eco-friendly and stable photoluminescent materials is useful yet challenging. Herein, we present the application of graphene quantum dots (GQDs) for full-color and stimuli-responsive information encryption. GQDs with red, green and blue (RGB) fluorescence or ion-responsiveness are prepared based on scalable bottom-up molecular fusion in one-step hydrothermal or solvothermal reaction. Printable fluorescent ink is easily prepared by dispersing GQDs homogeneously in glycerol-containing ethanol. Utilizing the color, pattern, characteristic fluorescence emission spectrum, or stimuli-responsive emission of GQDs, information encryption under daylight and information decryption under UV light are realized. Moreover, N and S co-doped GQDs (N, S-GQDs), which have Cu2+-quenchable and cysteine (Cys)-recoverable blue fluorescence, are mixed with lanthanide complex (Eu3+DP) to realize order-sensitive stimulus-responsive information encryption.

Gd2O3:Tb3+ nanocrystal co-doped with Zn2+ and Li+ was prepared by the combination of polyol and solid-phase methods. The synthesized nanoparticles were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), photoluminescence (PL) spectra and magnetic resonance imaging (MRI). The results revealed that both Gd2O3:Tb3+/Zn2+ and Gd2O3:Tb3+/Li+ had cubic unit structures with a spherical shape, and the fluorescence intensity of the nanoparticles reached a maximum at a doping concentration of 0.050 mmol% for Zn2+ and 2 mol% for Li+, respectively. In addition, the T1/T2 (longitudinal/transverse relaxation time)-weighted MRI signals got enhanced due to the increased longitudinal relaxivity (r1) and transverse relaxivity (r2) after the doping by metal ions. Therefore, the materials reported here can be used for fluorescence and MR bimodal imaging, as tracers and for fluorescence detections.

We investigate the two-photon fluorescence (TPF) of conjugated polymer (CP) microspheres with diameters up to tens of micrometers. Two polymers, emitting in either the violet or red, were first synthesized and characterized in terms of their one-photon fluorescence and three-dimensional internal microstructure. Under femtosecond infrared excitation, both types of microspheres showed a strong TPF, which was investigated by the excitation intensity dependence, emission spectroscopy, time-resolved luminescence, and photobleaching dynamics. While the violet-fluorescent microspheres performed similarly compared to dye-doped polystyrene counterparts emitting at a similar wavelength, the red-fluorescent microspheres showed a two-orders-of-magnitude stronger TPF. This excellent performance is attributed to enhanced hyperpolarizability associated with intermolecular interactions in the polymer solid, indicating a route toward designed CP microspheres that could outperform currently-available microparticles for sensing or imaging applications involving two-photon fluorescence.

New cyan long persistent luminescence (LPL) phosphors Sr5SiO4Cl6:Eu2+, Cr3+/Sc3+ (SSC: Eu2+, Cr3+/Sc3+) have been prepared. The LPL behaviors of the SSC are greatly enhanced through incorporating Cr3+ and Sc3+ ions as trap centers. The fluorescence and phosphorescence spectra of SSC:Eu2+, Cr3+/Sc3+ both show an asymmetric wide emission band at 446 nm, which is attributed to the 4f65 d1→4f7 transitions of Eu2+ions in two different Sr2+ sites. The LPL of the SSC:0.03Eu2+, 0.03Cr3+ can remain 11760 s above the identifiable intensity level (0.32 mcd m−2) after 10 min of excitation (for SSC:0.05Eu2+, 0.05Sc3+, 4080s). In addition, the temperature-dependent afterglow decay curves also show good afterglow initial brightness at 443 K for SSC:0.03Eu2+, 0.03Cr3+ (for SSC:0.05Eu2+, 0.05Sc3+, 343 K). This research provides new blue LPL phosphors with potential applications in high temperature environment.

Lipid droplets (LDs) are closely connected to many physiological processes and abnormal LDs are related to many diseases. Herein, a family of two-photon fluorescence compounds based on the aurone skeleton were developed as efficient LDs imaging probes. They exhibit the obvious solvatochromism effect from blue to orange emission (∼140 nm shift) in various solvents. The robust probes possess low toxicity to living cells, high photobleaching resistance, and superior photostability and can light up LDs with high specificity. Furthermore, the probe DMMB (aurone skeleton with dimethylamino) was carefully applied in real-time monitoring of the morphological changes of LDs and the interactions between LDs and mitochondria under specific physiological conditions (e.g., starvation). We have observed for the first time the dynamic change between mitochondria and LDs when mitochondrial damage is caused by a large excess of H2O2 in a short period of time.

Because of the involvement of the gas–solid diffusion, device fabrication, and the relatively complex photophysical process, the lanthanide complexes are rarely exploited as fluorescence sensors fo...

In this paper, we reported a system for the ultrasensitive fluorescence detection of cytokeratin fragment antigen 21–1 DNA (CYFRA21-1 DNA) for the early diagnosis of lung cancer. The approach used electron transfer atom transfer radical polymerization (ARGET-ATRP) with ethylenediaminetetraacetic acid (EDTA) as the metal ligand. Firstly, thiolated peptide nucleic acid (PNA) was linked to aminated magnetic beads solutions (MBs) by a cross-linking agent and then hybridized with CYFRA21-1 DNA (tDNA). Subsequently, Zr4+ was introduced into the MBs by conjugating with the phosphate group of tDNA, and the initiator of ARGET-ATRP was introduced into via phosphate-Zr4+-carboxylate chemistry. Next, Cu(II)Br/EDTA was reduced to Cu(I)/EDTA by ascorbic acid (AA) to trigger ARGET-ATRP and then a large amount of fluorescein-o-acrylate (FA) molecules were grafted from the surface of the MBs, which amplified significantly the fluorescent signal. Under optimal conditions, a strong linear relationship of tDNA over the range from 0.1 fM to 1 nM (R2 = 0.9988). The limit of detection was as low as 23.8 aM (~143 molecules). The fluorescence detection based on the ARGET-ATRP strategy yielded excellent sensitivity, selectivity, outstanding anti-interference properties, and cost-effectiveness. These results indicated that this strategy has considerable potential for biological detection and early clinical diagnosis. Keywords: EDTA, Fluorescence detection, CYFRA21-1, ARGET-ATRP, Lung cancer

Two novel ZnII complexes based on a tripodal carboxamide-containing ligand, [Formula: see text] and [Formula: see text] (where LL-2 = N′, N″, N′″-tris(pyrid-2-ylmethyl)-1,3,5-benzenetricarboxamide) are synthesized and structurally characterized. The first complex is a zero-dimensional structure which was further connected into a three-dimensional structure via hydrogen bond interactions, while the second complex features a one-dimensional tube-like structure, where the structural diversities were mainly caused by the different anions. The solid-state luminescent properties of the complexes were investigated and powder X-ray diffraction and thermal gravimetric analysis were performed.

Sulfur dioxide (SO2) is commonly used in food processing and preservation processes due to its antioxidant and antibiotic properties. However, it has been documented that excessive intake of SO2 could cause serious health problems. Therefore, it is very necessary to develop a novel SO2 probe with excellent performance. Herein, a novel fluorescent probe (Ph-CN) based on the ICT-ESIPT mechanism for monitoring SO2 with the C[double bond, length as m-dash]N double bond was developed. Furthermore, Ph-CN exhibits various splendid features, such as near-infrared (NIR) and ratiometric detection, real-time detection (

The excessive production of sulfur dioxide (SO2) and formaldehyde (FA) by organisms is closely associated with several diseases, including neurological disorders, respiratory disease, and genotoxicity. RNA plays a central role in the expression of genes. However, it is difficult for fluorescent probes to explore the intersecting correlation of SO2 and FA near the nucleolus regions due to the protective obstacle of the cell nucleus membrane. Herein, a unique fluorescent probe (DP) for reversible detection of the interaction of SO2 and FA in the nucleolus regions was constructed. In light of the outstanding attributes of DP, including a large fluorescence ratio variation, ultrafast detection of SO2, and excellent reversibility, it was successfully employed to track the variation of endogenous SO2 and FA in the cytoplasm and nucleolus regions of live cells. In addition, the DP probe could be applied to the imaging of endogenous SO2 and then recovered by FA in live mice.

SO2 and formaldehyde (FA) are important signal molecules in physiological and pathological processes. It is particularly urgent to seek a method that can monitor SO2 and FA in real-time to study their role in organisms. Herein, we designed and synthesized a ratiometric fluorescent probe NaP based on the FRET mechanism for the reversible detection of SO2 and FA. This probe possesses high sensitivity, good selectivity, excellent photostability, low cytotoxicity and an ultra-fast response to SO2 (within 5 s). Notably, the probe can be recovered efficiently by FA. In addition, the biological experiments showed that the novel probe NaP could reversibly image SO2 and FA in cells and mice.

A novel and simple "off-to-on" fluorescent sensing platform for β-amyloid oligomers (Aβo) was developed based on dye (FAM)-labeled single-strand DNA (FAM-ssDNA)-conjugated molybdenum disulfide nanosheets (MoS2 NSs). Due to strong adsorption of ss-DNA to the surface of MoS2 NSs, the fluorescence of FAM was quenched remarkably, leading to a fluorescent "off" state. However, in the presence of Aβo, a hybrid structure between Aβo and FAM-ssDNA resulted in the dissociation of FAM-ssDNA from MoS2 NSs and an obvious fluorescence recovery transformed the fluorescence to an "on" state. The developed fluorescence sensing assay showed a good linear relationship toward Aβo ranging from 0.01 to 20 μM (R2 = 0.994) with a satisfactory detection limit of 3.1 nM. Practical samples of hippocampus and cortex tissues from APP/PS1 double transgenic AD mice were applied to demonstrate feasibility of the assay. Moreover, we found that similar to MoS2 nanoparticles, MoS2 NSs possessed therapeutic effects on Alzheimer's disease (AD) by inhibiting Aβ aggregations and degrading the previously formed Aβ fibrils. Collectively, the high sensitivity, specificity, and good biocompatibility along with an efficient anti-aggregation ability, the presented fluorescent strategy with MoS2 NSs demonstrated their promising potential for future AD-related research.

The use of the pesticide imidacloprid can be hazardous to human health. In this work, the impacts of imidacloprid on the secondary structure of pepsin were investigated through spectroscopic techniques and simulation studies. One binding site for pepsin with strong affinity was evident from changes in the fluorescence emission spectra of pepsin in the presence of imidacloprid. Calculated thermodynamic parameters based on the van't Hoff relationship indicate the predominance of hydrophobic and hydrogen bonding interactions contributing to the imidacloprid-pepsin complex. Structural changes in pepsin were also evident from changes in the UV, FTIR, CD, three-dimensional fluorescence (3D), and synchronous fluorescence spectroscopy (SFS) of pepsin upon titration with imidacloprid. Furthermore, density functional theory (DFT) calculations and molecular docking studies revealed predominant binding of imidacloprid in the hydrophobic pocket of pepsin.

Viscosity is a key factor that determines the diffusion-controlled processes in biological systems. The matrix of mitochondria contains various enzymes and other proteins with high density, and the diffusion of which are severely restricted by the cristae, making it the most crowded place in the cells. Herein, we reported a new near-infrared probe NV-1 with increased Stokes shift for monitoring viscosity changes in mitochondria. A remarkable increase of the fluorescence was observed in glycerol compared with which was observed in methanol at 744 nm. The probe was applied for measuring viscosity changes not only in mitochondria, but also in vivo (in zebra fishes and mice).

Ratiometric fluorescent probes have shown great potential for optical sensing and have been widely used for bioimaging. However, due to extremely stringent molecular design, most conventional organic ratiometric fluorescent probes can only achieve one single ratio. Currently, the detection of a target in living systems in a multiratiometric manner is prominently challenging. Therefore, it is of great significance to develop a method to construct the multiratiometric fluorescent probes for accurate quantitative detection of specific small molecules. To address this challenge, we developed a unique multiratiometric composite fluorescent probe. Herein, a new triple-ratiometric fluorescent composite nanoprobe CP@GQDs-OH based on OH-functionalized GQDs (GQDs-OH) and red emission ratiometric fluorescent molecular probe (CP) was prepared through π-π stacking. The novel nanoprobe showed high selectivity for SO