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Herein, a fluorescent probe BFO-HPS was developed for imaging the H2Sn dynamics of the macrophage inflammatory regulation in bone homeostasis. The probe indicated advantages including large response scale, rapid response, steady optical performance in various pH conditions, high selectivity, and good selectivity. BFO-HPS showed a dose-dependent fluorescence response at 570 nm for the H2Sn concentration with the linear range from 0.1 to 100 µM, limit of detection of 0.11 µM, and limit of quantitation of 0.10 µM. Based on the low cyto-toxicity, BFO-HPS provided the intracellular monitoring of the exogenous H2Sn level in uninduced RAW264.7 cells. In the receptor activator of nuclear factor-κB ligand (RANKL)-induced and RANKL-induced inhibited groups, BFO-HPS achieved the monitoring of the H2Sn dynamics to indicate the macrophage-involved bone homeostasis. This work was informative for further investigations on macrophage inflammatory regulation in bone homeostasis. [ABSTRACT FROM AUTHOR]

The effective capture and accurate identification of heterogeneous circulating tumor cells (CTCs) aid in guiding clinical diagnosis and personalized treatment of tumors. Herein, a core‐satellite‐sized magnetic separable nanodevice (denoted as MS‐RI) is developed for the capture and subtype identification of heterogeneous CTCs by identifying the protein targets of CTCs in vitro and imaging intracellular nucleic acid targets of CTCs in situ. Upon the separation of CTCs by MS‐RI using aptamers as capture elements, the programmatically dissociated satellite particles aim to internalize into the cells for simultaneous profiling of microRNA‐21 and microRNA‐141. By virtue of the validated magnetic separation of the core structure, the high affinity of the aptamer, and the high sensitivity of the recognition imaging (RI) module, MS‐RI allows the isolation and subtyping of CTCs in clinical samples from breast cancer patients. This strategy of combining extracellular recognition and intracellular imaging pioneers a new paradigm for the capture and precision subtyping of heterogeneous CTCs. [ABSTRACT FROM AUTHOR]

Tetracycline (TC) is a commonly used antibiotic in human therapy and animal husbandry. Public concerns about TC residues inflated due to their negative impact on the environment, food, and human health concerns. To ensure human health and safety, there is a need for fluorogenic chemosensors that can easily detect TC antibiotics with high selectivity and sensitivity in the aqueous medium. This mini‐review discusses the progress and achievements in several fluorometric antibiotic tetracycline detection methods. Fluorogenic chemosensors for tetracycline antibiotics with easy‐to‐use, high selectivity, and sensitivity have been essentially required to regulate food safety and secure human health and safety. Moreover, we gave more attention to the practical applicability of chemosensors for tetracycline antibiotics in food and water quality assessment. This article starts with a section that constitutes an overview of the problems of antibiotics and the typical features of traditional techniques of antibiotic detection. It then goes on to describe up‐to‐date optical methods for the selective detection and efficient removal of TC. These methods involve a variety of platforms, like tetraphenylethylene polymers, metal complexes, self‐assembled CuNCs, and hydrogel. The article also discusses the practical applicability of chemosensors for tetracycline antibiotics in food and water quality. [ABSTRACT FROM AUTHOR]

This study explores the impact of incorporating oxyethylene (OE) chains into rhodamine‐based dye molecules for the enhancement of photophysical properties in the context of chemical sensing. The introduction of OE chains provides several advantages, including improved water solubility, photostability and resistance to self‐assembled nanoaggregates formation. Despite these, the compound with oxyethylene chains showed poor response (~2‐fold) towards Hg2+ ions than that of dimeric probe (~20 fold) with no such substituents. Notably, dimeric compound shows a remarkable three‐fold larger response to Hg2+ ion compared to monomeric compound. This intriguing outcome is attributed to the extended conjugation within the dimeric structure, which can induce conformational change of the overall molecule. Moreover, the study investigates the effects of end substituents, such as electron‐donating (−OMe, improved response) and electron‐withdrawing (−NO2, poor response) groups, on the interaction with Hg2+ ions. The excellent sensitivity of the probe molecules is also evident in significantly low detection limits for Hg2+ ion (5–8 ppb) in real‐life water samples. The high recovery values (>95 %) with sufficient low standard deviation (<5%) indicates that quantitative analysis of Hg2+ is achievable using the current protocol. Beyond that, we have employed the probe 1 for intracellular (HEK293T cells) fluorescence imaging of Hg2+. [ABSTRACT FROM AUTHOR]

A DNA triangular prism nanomachine (TPN)–based logic device for intracellular AND-gated imaging of adenosine triphosphate (ATP) has been constructed. By using i-motif sequences and ATP-binding aptamers as logic control units, the TPN logic device is qualified to respond to the acidic environment and ATP in cancer cell lysosomes. Once internalized into the lysosome, the specific acidic microenvironment in lysosome causes the i-motif sequence to fold into a tetramer, resulting in compression of DNA tri-prism. Subsequently, the split ATP aptamer located at the tip of the collapsed triangular prism binds stably to ATP, which results in the fluorescent dyes (Cy3 and Cy5) modified at the ends of the split aptamer being in close proximity to each other, allowing Förster Resonance Energy Transfer (FRET) to occur. The FRET signals are excited at a wavelength of 543 nm and can be collected within the emission range of 646–730 nm. This enables the precise imaging of ATP within a cell. We also dynamically operate AND logic gates in living cells by modulating intracellular pH and ATP levels with the help of external drugs. Owing to the AND logic unit on TPN it can simultaneously recognize two targets and give corresponding intelligent logic judgment via imaging signal output. The accuracy of molecular diagnosis of cancer can be improved thus eliminating the false positive signal of single target-based detection. Hence, this space-controlled TPN-based logical sensing platform greatly avoids sensitivity to extracellular targets during the cell entry process, providing a useful tool for high-precision imaging of the cancer cell's endogenous target ATP. [ABSTRACT FROM AUTHOR]

Peroxynitrite (ONOO−) is a crucial reactive oxygen species that plays a vital role in cellular signal transduction and homeostatic regulation. Determining and visualizing peroxynitrite accurately in biological systems is important for understanding its roles in physiological and pathological activity. Among the various detection methods, fluorescent probe-based spectroscopic detection offers real-time and minimally invasive detection, high sensitivity and selectivity, and easy structural and property modification. This review categorizes fluorescent probes by their fluorophore structures, highlighting their chemical structures, recognition mechanisms, and response behaviors in detail. We hope that this review could help trigger novel ideas for potential medical diagnostic applications of peroxynitrite-related molecular diseases. [ABSTRACT FROM AUTHOR]

A diformylphenol Schiff base of triazole‐amine, 4‐methyl‐2, 6‐bis‐[(1H‐[1,2,4] triazol‐3‐ylimino)‐methyl]‐phenol (PTR) has been synthesised and characterised by spectroscopic data (ESI‐MS, UV‐vis, FT‐IR, NMR spectra). The probe, PTR, emits at 610 nm upon excitation at 380 nm and the emission is strongly intensified on interacting with Zn2+ ion in DMSO‐water (99:1, v/v; HEPES buffer, pH, 7.2) solution even in the presence of 15 other cations (Cu2+, Mn2+, Co2+, Ni2+, Pd2+, Cd2+, Pb2+, Hg2+, Fe3+, Cr3+, Al3+, Na+, K+, Ba2+, Ca2+) and the emission band has been shifted to 530 nm. The limit of detection of Zn2+, 0.30 μM is much lower than WHO recommended value (76 μM). The binding constant (Kd) is 4.2585 × 104 M−1. Selective and sensitive chemosensing behaviour of PTR to Zn2+ has been explained by switching off ESIPT quenching of the keto‐enol tautomerisation of the probe along with the chelation enhancement of fluorescence (CHEF) by binding with Zn2+. The Job's plot and NMR titration have been extended to measure the 1:1 M composition [PTR + Zn2+]. The energy calculation by the DFT computation of keto and enol isomers supports easy tautomerisation and helps ESIPT quenching by proton transfer. Intracellular Zn2+ ions in living cells of HEK293 (PBS: phosphate buffer saline; pH, 7.2) have also been identified by the probe, PTR, using fluorescence microscopic imaging technique. [ABSTRACT FROM AUTHOR]

Simultaneous and non-destructive quantitative detection of intracellular metal ions holds great promise for improving the accuracy of diagnosis and biological research. Herein, novel multicolor DNAzymes-embedded framework nucleic acids (FNAzymes) were presented, which can easily enter cells and achieve simultaneous and quantitative detection of intracellular physiologically related Cu2+ and Zn2+. Two types of DNAzymes, specific to Cu2+ and Zn2+, were encoded in the framework nucleic acids (FNAs) via self-assembly. With the formation of a well-ordered FNAzyme nanostructure, the fluorophore and the quencher were close to each other; therefore, the fluorescence was quenched. In the presence of Cu2+ and Zn2+, the integrated FNAzymes would be specifically cleaved, resulting in the release of fluorophores in cells. Consequently, the fluorescence in living cells could be observed by a confocal microscope and semi-quantitatively analyzed by flow cytometry with low-nanomolar sensitivity for both metal ions. The FNAzymes have high uniformity and structural accuracy, which are beneficial for intracellular detection with excellent reproducibility. This proposed method offers new opportunities for non-destructive, semi-quantitative, multi-target detection in living cells. [ABSTRACT FROM AUTHOR]

The availability of various calcium ion (Ca 2+ ) fluorescent probes has contributed to revealing physiological events related to intracellular Ca 2+ . However, conventional probes face challenges for quantitatively and selectively visualizing high Ca 2+ concentrations in cells induced by any stimuli, including biomolecules or electrical signal that disrupt Ca 2+ homeostasis. In this report, we designed and synthesized a low-affinity ratiometric Ca 2+ probe, KLCA-Fura , utilizing o -aminophenol- N,N -diacetate- O -methylene-methylphosphinate (APDAP) as a ligand, for which we recently demonstrated the suitability as a new low-affinity ligand for Ca 2+ . KLCA-Fura showed a blue shift in excitation wavelength with increasing Ca 2+ concentration based on the intramolecular charge transfer (ICT). Its affinity for Ca 2+ is lower than commercially available conventional Ca 2+ probes. Furthermore, the selectivity for Ca 2+ and the fluorescence intensity were considered sufficient to accurately detect Ca 2+ . The corresponding acetoxymethyl ester, KLCA-FuraAM , was synthesized for intracellular imaging and applied to Ca 2+ quantification in neurons. KLCA-FuraAM enabled quantitative ratiometric monitoring of the two-step Ca 2+ concentration increase induced by glutamate stimulation. While this two-step response was not clearly observed with a commercially available low-affinity ratiometric Ca 2+ probe, Fura-FF, KLCA-FuraAM has demonstrated the potential to quantitatively visualize the behavior of high Ca 2+ concentrations. The ratiometric low-affinity Ca 2+ probe, KLCA-Fura , is expected to be a powerful tool for discovering new functions of Ca 2+ in neurons.

Herein, a cytoplasm-applicative aggregation-induced fluorescent probe Pyr-HS was developed for detecting H 2 S in living cells and C. elegans. The trials were carried out to utilize the aggregation-induced strategy to realize the wide linear range as well as cytoplasm-applicative imaging capability. In-solution tests suggested that Pyr-HS responded to H 2 S with notable fluorescence enhancement and naked-eye observed color change. The detecting product Pyr-OH exhibited the obvious aggregation to form crystal clusters. By coupling the correlation curves, the linear range of the detecting system was extended to 0–1500 μM, with the LOD value of 0.4481 μM. The Pyr-HS has high sensitivity and selectivity. With low cyto-toxicity, Pyr-HS achieved the imaging of both the exogenous and endogenous H 2 S in living cells and Caenorhabditis elegans. The aggregation of the detecting product locked the fluorescence signals in the cytoplasm, which was a potential cytoplasm-applicative imaging pattern. This work was informatic with the aggregation-induced strategy in introducing the wide linear range and cytoplasm-applicative imaging. • A cytoplasm-applicative aggregation-induced fluorescent probe, Pyr-HS , was developed for monitoring H 2 S. • Pyr-OH exhibited the obvious aggregation to form crystal clusters. • The aggregation of the detecting product locked the fluorescence signals in the cytoplasm. • Reliable linear range, high sensitivity, high selectivity towards H 2 S. • Applied into the biological imaging of H 2 S in living cells and Caenorhabditis elegans. [ABSTRACT FROM AUTHOR]

Microscopy image observation is commonly performed on 2D screens, which limits human capacities to grasp volumetric, complex, and discrete biological dynamics. With the massive production of multidimensional images (3D + time, multi-channels) and derived images (e.g., restored images, segmentation maps, and object tracks), scientists need appropriate visualization and navigation methods to better apprehend the amount of information in their content. New modes of visualization have emerged, including virtual reality (VR)/augmented reality (AR) approaches which should allow more accurate analysis and exploration of large time series of volumetric images, such as those produced by the latest 3D + time fluorescence microscopy. They include integrated algorithms that allow researchers to interactively explore complex spatiotemporal objects at the scale of single cells or multicellular systems, almost in a real time manner. In practice, however, immersion of the user within 3D + time microscopy data represents both a paradigm shift in human-image interaction and an acculturation challenge, for the concerned community. To promote a broader adoption of these approaches by biologists, further dialogue is needed between the bioimaging community and the VR&AR developers.

Simultaneous and non-destructive quantitative detection of intracellular metal ions holds great promise for improving the accuracy of diagnosis and biological research. Herein, novel multicolor DNAzymes-embedded framework nucleic acids (FNAzymes) were presented, which can easily enter cells and achieve simultaneous and quantitative detection of intracellular physiologically related Cu2+ and Zn2+. Two types of DNAzymes, specific to Cu2+ and Zn2+, were encoded in the framework nucleic acids (FNAs) via self-assembly. With the formation of a well-ordered FNAzyme nanostructure, the fluorophore and the quencher were close to each other; therefore, the fluorescence was quenched. In the presence of Cu2+ and Zn2+, the integrated FNAzymes would be specifically cleaved, resulting in the release of fluorophores in cells. Consequently, the fluorescence in living cells could be observed by a confocal microscope and semi-quantitatively analyzed by flow cytometry with low-nanomolar sensitivity for both metal ions. The FNAzymes have high uniformity and structural accuracy, which are beneficial for intracellular detection with excellent reproducibility. This proposed method offers new opportunities for non-destructive, semi-quantitative, multi-target detection in living cells.

The gold nanostars (GNSs) with sharp branches have shown tunable strong localized surface plasmon resonance (LSPR) peak in the NIR region by varying the size and the shape of the branches which cause to use them for applications such as surface-enhanced Raman spectroscopy (SERS), intracellular imaging and sensing. In this paper, plasmonic nanoprobes based on the GNSs with different morphology have been designed and embedded in the human skin tissue as a surrounding media. The strong Raman scattering has been calculated for GNSs. Furthermore, the high refractive index sensitivity ( RIS ), the effective figure of merit (FOM) enhancement with minimum cellular damage in intracellular imaging, are observed. The RIS and FOM are found to be dependent on the shape and the size of the GNS and the dielectric constant of the surrounding medium. Our results briefly demonstrate the existence of electromagnetic hotspot in the sharp branches of the GNS with the high LSPR peak in the tissue diagnostic window. Moreover, we obtained the high RIS of 856 nm RIU , and a large FOM around 2.1 R I U - 1 with the wide resonance spectra in comparison with previously presented nanoparticles. We present guideline for designing the specific nanostar based LSPR nanoprobe with high sensitivity. [ABSTRACT FROM AUTHOR]

A benzo[ d ]imidazole-derived fluorescent probe, DCBIF , was developed for the carbon dioxide (CO 2) detection and imaging in living lung cells. On the basis of investigating previous reports and modifying the test method, the in-solution experiments showed that DCBIF exhibited the fluorescence response at 420 nm to CO 2 under the excitation of 350 nm. The response was steady and rapid in physiological conditions. The linear range of the detecting system covered the practical necessity, and the limit of detection was 0.002 mL/min. There were few reports for detecting CO 2 depicted the intracellular imaging while the cells were not pulmonary. Herein, in all the tested groups including oxygen-rich, hypoxia, and hypoxia recovered, DCBIF realized the imaging of the CO 2 level in living A549 lung cells. This work was meaningful for developing fluorescent implements and imaging scenarios. [Display omitted] • A benzo[ d ]imidazole-derived fluorescent probe developed for the carbon dioxide detection. • Steady and rapid response in physiological conditions, with high sensitivity and selectivity. • Imaging the carbon dioxide level in living lung cells. • Achieving the imaging of the status including oxygen-rich, hypoxia, and hypoxia recovered. In this work, a benzo[ d ]imidazole-derived fluorescent probe, DCBIF , was developed for the carbon dioxide (CO 2) detection and imaging in living lung cells. On the basis of investigating previous reports and modifying the test method, the in-solution experiments showed that DCBIF exhibited the fluorescence response at 420 nm to CO 2 under the excitation of 350 nm. The response was steady and rapid in physiological conditions. The linear range of the detecting system covered the practical necessity, and the limit of detection was 0.002 mL/min. There were few reports for detecting CO 2 depicted the intracellular imaging while the cells were not pulmonary. Herein, in all the tested groups including oxygen-rich, hypoxia, and hypoxia recovered, DCBIF realized the imaging of the CO 2 level in living A549 lung cells. This work was meaningful for developing fluorescent implements and imaging scenarios. [ABSTRACT FROM AUTHOR]

The integration of strong near-infrared (NIR) emission, rapid lysosome escape, fast cellular excretion, and efficient total body clearance is highly desired for nanoparticles (NPs) to achieve synergistic functions in both molecular imaging and delivery. Herein, using a well-designed cyclopeptide (CP) that can spontaneously assemble into controllable nanofibers as template, a facile strategy is reported for in situ self-assembly of NIR-emitting gold NPs (AuNPs) into ordered and well-controlled one-dimensional (1D) nanostructures (AuNPs@CP) with greatly enhanced NIR emission (∼ 6 fold). Comparing with the unassembled AuNPs, the AuNPs@CP are observed to enter living cells through endocytosis, escape from lysosome rapidly, and excrete the cell fast, which shows high gene transfection efficiencies in construction of cell line with ∼ 7.5-fold overexpression of p53 protein. Furthermore, the AuNPs@CP exhibit high in vivo diffusibility and total body clearance efficiency with minimized healthy organ retention, which are also demonstrated to be good nanovectors for plasmid complementary deoxyribonucleic acid 3.1 (pcDNA3.1)(+)-internal ribosome entry site (IRES)-green fluorescent protein (GFP)-p53 plasmid with efficient p53 gene over-expression in tumor site. This facile in situ strategy in fabricating highly luminescent 1D nanostructures provides a promising approach toward future translatable multifunctional nanostructures for delivering, tracking, and therapy. [ABSTRACT FROM AUTHOR]

Novel polyepinephrine-modified NaYF4:Yb,Tm upconversion luminescent nanoparticles (UCNP@PEP) were prepared via the self-polymerization of epinephrine on the surfaces of the UCNPs for selective sensing of Fe3+ inside a cell and for intracellular imaging. The proposed UCNP@PEP probe is a strong blue light emitter (λmax = 474 nm) upon exposure to an excitation wavelength of 980 nm. The probe was used for detecting Fe3+ owing to the complexation reaction between UCNP@PEP and Fe3+, resulting in reduced upconversion luminescence (UCL) intensity. The proposed probe has a detection limit of 0.2 μM and a good linear range of 1–10 μM for sensing Fe3+ ions. Moreover, the UCNP@PEP probe displays high cell viability (90%) and is feasible for intracellular imaging. The ability of the probe to sense Fe3+ in a human serum sample was tested and shows promising output for diagnostic purposes. The prepared UCNP@PEP probe was characterized by using UV-visible (UV-Vis) absorption spectrometry, fluorescence (FL) spectrometry, field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FT-IR). [ABSTRACT FROM AUTHOR]

It is of great value to detect biological molecules in live cells. However, probes for imaging low‐abundance targets in live cells are limited by the one‐to‐one signal‐triggered model. Here, we introduce the concept of the amplified FRET nanoflare, which employs high‐abundance endogenous mRNA as fuel strands to amplify the detection of low abundance intracellular miRNA. As far as we know, this is the first report of an endogenous mRNA‐powered nanomachine for intracellular molecular detection. We experimentally prove the mechanism of the nanomachine and demonstrate its specificity and sensitivity. The proposed amplified FRET nanoflare can act as an excellent intracellular molecular detection strategy that is promising for biological and medical applications. [ABSTRACT FROM AUTHOR]

The great challenge still exists in the synthesis of red-emissive carbon nanodots (C-dots) and the development of molecular logic devices with better operation stability for biological applications. In this study, gadolinium (III)-doped C-dots are synthesized by a new solvothermal approach using citric acid, urea and GdCl 3 as precursors. The as-prepared Gd3+-doped C-dots exhibit bright red fluorescence (FL) centered at 620 nm in an excitation wavelength-independent manner, and a high T 1 relaxivity (∼16.0 mM−1 s−1). More excitingly, the Gd3+-doped C-dots exhibit a pH-dependent response in not only FL behaviour but also magnetic resonance (MR) signal. When triggered by H+, OH−, or Cu2+, the Gd3+-doped C-dots can behave as a switch for FL emission and MR signal, leading to dual-readout and multi-addressable logic systems. Therefore, by employing the Gd3+-doped C-dots as logic gate with varying the chemical inputs, FL/MR dual-readout logic operations including IMP and NOR have been successfully demonstrated not only in all-aqueous media but also within the living HeLa cells. Together with the good biocompatibility and cell-permeability, the Gd3+-doped C-dots hold great potentials for real-time monitoring pH changes both in solution and biological cells, and even future evaluating cellular states via in-cell biocomputation. Image 1 [ABSTRACT FROM AUTHOR]

Dual-emissive carbon dots (CDs) were fabricated for dual-channel ratiometric fluorometric determination of pH and mercury ion (Hg2+) and intracellular imaging. Dual-emissive CDs were synthesized by one-pot solvothermal treatment of cabbage. The CDs exhibited two distinctive fluorescence emissions at 500 and 678 nm under single excitation at 410 nm. The green emission (500 nm) had reversible linear response to pH (7.0–12.0) due to deprotonation and protonation of surface functional groups and their non-covalent interactions. On the other hand, the red emission (678 nm) had efficient and selective fluorescence response to Hg2+ by formation of non-emission complex between CDs and Hg2+. The limit of detection (LOD) and limit of quantification (LOQ) for Hg2+ were 6.25 and 20.63 nM, respectively. The CDs have been successfully applied for label-free ratiometric fluorometric determination of pH and Hg2+ in fish and human serum samples with good recoveries (92.0–108.3%). In addition, the CDs had excellent photostability, low cytotoxicity, and good biocompatibility for intracellular imaging. All in all, the system was multi-functional in determination, high in sensitivity, and excellent in selectivity, which demonstrated wide and promising applicability for biosensing and bioimaging in the future. [ABSTRACT FROM AUTHOR]

[Display omitted] • We review the advance in intracellular telomerase imaging for cancer diagnosis and therapy. • We summarize their principles, features, performances, and applications. • We highlight the challenges and future directions in the field d. Telomerase is a distinctive reverse transcriptase that can elongate telomere end to preserve the telomere length and maintain chromosome integrity. Telomerase activity is silenced in most normal cells but highly reactivated in almost all types of tumor cells, making it an important hallmark of cancers and a potential target for cancer therapeutics. However, the majority of reported methods are only suitable for telomerase detection in cell extracts, which severely hinders their wider applications in fundamental research and clinical diagnosis. Recently, a series of imaging methods are developed for intracellular telomerase imaging in living cells and even living bodies, providing a non-invasive and real-time approach for better understanding the telomerase-associated carcinogenesis and accurately evaluating the efficiency of telomerase inhibitor drugs. In this review, we introduce the biological functions of telomerase and summarize the recent advances in development of various methods for in vivo telomerase imaging (e.g., fluorescence imaging, dark-field imaging, Raman imaging, and magnetic resonance imaging), and discuss their principles, features, performances, and applications in cancer cell discrimination, telomerase inhibitor screening, and cancer therapy. Moreover, we highlight the challenges and future directions in the field. [ABSTRACT FROM AUTHOR]

Ag+ pollution is of great harm to the human body and environmental biology. Therefore, there is an urgent need to develop inexpensive and accurate detection methods. Herein, lignin-derived structural memory carbon nanodots (CSM-dots) with outstanding fluorescence properties were fabricated via a green method. The mild preparation process allowed the CSM-dots to remain plentiful phenol, hydroxyl, and methoxy groups, which have a specific interaction with Ag+ through the reduction of silver ions. Further, the sulfur atoms doped on CSM-dots provided more active sites on their surface and the strong interaction with Ag nanoparticles. The CSM-dots can specifically bind Ag+, accompanied by a remarkable fluorescence quenching response. This “turn-off” fluorescence behavior was used for Ag+ determination in a linear range of 5–290 μM with the detection limit as low as 500 nM. Furthermore, findings showed that this sensing nano-platform was successfully used for Ag+ determination in real samples and intracellular imaging, showing great potential in biological and environmental monitoring applications.

In this work, a highly sensitive and selective fluorescent probe L based on naphthalimide derivative is developed for detection of Cu2+ ion in water samples and living cells. The probe displays excellent performance with great selectivity for Cu2+ ion detection in CH3CN/phosphate buffered saline (PBS, 10 mM, 9:1, v/v). The fluorescence of probe L is almost completely quenched upon the addition of Cu2+. The 2:1 stoichiometry of L–Cu2+ complex is confirmed by a Job's plot and ESI‐MS analysis. More evidence about the interaction mechanism of L with Cu2+ is 1H NMR titration data and density functional theoretical (DFT) studies. More importantly, the probe L with good cell permeability has been successfully applied to intracellular imaging of Cu2+ in A549 cells. [ABSTRACT FROM AUTHOR]

With rapid development of nuclear industry, the overexploitation of uranium has brought a series of radioactive pollution problems to water, soil, atmosphere and ecosystem. Uranium and its compounds are highly carcinogenic and biologically toxic, posing a deadly threat to human health. Therefore, how to design a highly selective and sensitive sensor to detect uranyl ions in the environment and organisms has become an urgent task. This review summarizes relevant literature on the detection of uranyl ions by different sensors over the years. The detection methods can be roughly divided into three categories: optical sensors, electrochemical sensors and other sensors; further classification has also been carried out according to their detection mechanism. The detection limits and performances of different sensors are discussed to intuitively understand different capability for these methods in detecting uranyl ions. We also discuss the trend and future direction of uranium to provide a valuable reference for further developing better uranyl sensors. Schematic diagram of sensors for detecting uranyl ions by different sensing modes. Image 1 • All of the reported uranium sensors over the years are summarized according to the sensing mode and detection mechanism. • The factors of selectivity, sensitivity, pH and other performance in uranium sensors are reviewed. • Advantages and limitations of uranium sensors in different sensing mode are concluded. • Summarization and future expectation of the uranium sensor are discussed. [ABSTRACT FROM AUTHOR]

• A novel fluorescence strategy based on MPA-AgInZnS QDs for sensitive and effective detection of protamine and trypsin. • This assay we investigated was simple, cost-effective, convenient and does not need any complicated pretreatment. • We successfully applied the AgInZnS QDs to intracellular imaging and lysosomes localization. In this study, a fluorescence strategy based on MPA-AgInZnS quantum dots (AIZS QDs) for the sensitive, effective detection of protamine and trypsin was developed. Protamine as a cationic peptide exhibited electrostatic interactions with AIZS QDs, leading to the aggregation of QDs and subsequent enhancement of the fluorescence intensity. The added trypsin catalyzed the hydrolysis of protamine and led to less formation of AIZS QDs/protamine complex, thereby decreasing the fluorescence intensity. Thus, a method for direct determination of protamine and indirect measurement of trypsin using protamine as a tool was developed. The protamine and trypsin concentrations were determined by the detection of the change in fluorescence intensity. Under the optimized conditions, the fluorescence intensity exhibited a good linear response to the protamine concentration, with a limit of detection (LOD) of 0.13 μg mL−1, and trypsin exhibited a linear relationship, with an LOD of 0.04 μg mL−1. The probe exhibited good biocompatibility and low cytotoxicity according to the MTT assay. Moreover, the application of this probe for intracellular imaging and lysosome localization demonstrates potential development in the biomedical and clinical fields. [ABSTRACT FROM AUTHOR]

• Our study provided an easily tunable way for extracellular or intracellular multi-probe designing. • Both extracellular and intracellular dual nanostructured probes exhibited fast, highly sensitive and reproducible responses. • Quantum yields of oxygen and pH probes in the nanoprobes were achieved to be ˜0.15 under nitrogen and ˜0.78 at pH 8, respectively • Quantum yields of the nanoprobes were achieved to be ∼0.15 (oxygen probe) under nitrogen and ∼0.78 (pH probe) at pH 8. Cellular pH and oxygen are the two important parameters to evaluate cell metabolism and functions of subcellular structures. Herein, we developed graft copolymers-based dual pH and oxygen luminescent nanoprobes with excellent sensitivity and quantum yields for both extracellular sensing and intracellular imaging. The oxygen probe platinum(II)-5,10,15,20-tetrakis-(2,3,4,5,6-pentafluorophenyl)-porphyrin (PtTFPP) was encapsulated into the hydrophobic core formed by poly(ε-caprolactone) (PCL), while pH sensitive fluorescein moieties were polymerized in hydrophilic chains of poly(oligo(ethylene glycol) methacrylate) (POEGMA). The quantum yield of oxygen and pH probe in the nanoprobes was separately achieved to be ˜0.15 under nitrogen and ˜0.78 at pH 8. Through tuning the polymer structures, the nanoprobes without the [2-(methacryloyloxy)ethyl] trimethylammonium chloride (MATMA) components (M1) was demonstrated to be extracellular probes; while the other nanoprobes with the MATMA moieties (M2) was demonstrated to be intracellular probe. Both nanostructured probes (＜150 nm) exhibited fast, highly sensitive and reproducible responses to pH and dissolved oxygen (DO). Clear cell density dependent extracellular acidification and oxygen consumption were observed by using M1 during the growth of macrophages and E.coli. Whereas, M2 showed the ability for analysis of pH and DO in the macrophage cells through bioimaging. Clear emission intensity changes under confocal were observed between hypoxia and normoxia conditions as well as between pH 4.5 and 7.5, suggesting that these nanoprobes are capable of cell metabolism monitoring and intracellular pH and DO analysis. This study provided a feasible way to design extracellular or intracellular multi-parameters sensing systems, simultaneously with excellent optical and sensing properties for biological applications. [ABSTRACT FROM AUTHOR]

Developing accurate, sensitive, and rapid methods for microRNA analysis in living cells is crucial for cancer diagnosis. Recent advances in enzyme-free amplification and spatial-confinement techniques have enhanced both the sensitivity and speed of miRNA detection. However, they also introduce a challenging contradiction: while localized amplification increases the sensitivity of miRNA detection, the consequent elevated risk of probe crosstalk can lead to false-positive signals and compromised accuracy. To strike a balance between the sensitivity, speed, and accuracy, we herein propose a localized branched catalytic hairpin assembly (LBCHA) strategy. This method employs three independent nanoprobes, each equipped with a specific branched catalytic hairpin assembly (bCHA) hairpin. The presence of the target initiates localized bCHA among the LRN probes, generating amplified fluorescent signals. Importantly, by anchoring each bCHA hairpin on separate nanospheres, we enhance detection sensitivity and speed while preserving accuracy by minimizing non-specific interactions. The LBCHA system demonstrated exceptional miRNA sensing performance in vitro, reaching a detection limit of 3.66 pM. Further applications in live cells and clinically derived tissues confirmed its potential for accurate cancer discrimination. This innovative LBCHA strategy holds great potential for clinical applications and real-time cancer diagnostics. • A Localized Branched Catalytic Hairpin Assembly (LBCHA) system based on three independent DNA nanospheres was developed. • The LBCHA system provides a solution to balance sensitivity, speed, and accuracy in miRNA detection. • The LBCHA system showed promising in vitro miRNA sensing performance, with a detection limit as low as 3.66 pM. • The LBCHA system holds potential for cancer detection in living cells and clinical tissues. [ABSTRACT FROM AUTHOR]

DNA repair enzymes play a vital role in the maintenance of genomic integrity, and the development of multiple diseases. Investigation of DNA repair enzymes is of great importance for understanding their functions in physiological processes and discovering new biomarkers. Fluorescent nucleic acid probes are regarded as a powerful technique for sensitive and accurate investigation of DNA repair enzymes, and the design strategies employed for these probes significantly influence the selectivity and sensitivity of analytical methods. In this article, we reviewed various design strategies of fluorescent nucleic acid probes for determination and visualization of DNA repair enzymes both in vitro and in cells, including probe structure, isothermal signal amplification methods and computer simulation-aided design techniques. In addition, the delivery methods of probes into cells are summarized. Furthermore, the potential challenges and future perspectives in this field are discussed. • Different probe structures for DNA repair enzyme monitoring are introduced. • Non-polymerase signal amplification strategies for DNA repair enzyme detection are summarized. • The use of computer simulation methods in the design of fluorescent nucleic acid probes for DNA repair enzyme is reviewed. • Different DNA probe carriers for intracellular imaging of DNA repair enzymes are outlined. [ABSTRACT FROM AUTHOR]

The spectral dual-mode response towards analyte has been attracted much attention, benefiting from the higher detection accuracy of such strategy in comparison to single signal readout. However, the currently reported dual-mode sensors for acid phosphatase (ACP) activity are still limited, and most of them more or less exist some deficiencies, such as complicated construction procedure, high-cost, poor biocompatibility, aggregation-caused quenching and limited emission capacity. Herein, we employed Fe3+ functionalized CuInS 2 /ZnS quantum dots (CIS/ZnS QDs) as nanosensor to develop a novel fluorometric and colorimetric dual-mode assay for ACP activity, combing with ACP-triggered hydrolysis of ascorbic acid 2-phosphate (AAP) into ascorbic acid (AA). The Fe3+ binding to CIS/ZnS QDs can be reduced into Fe2+ during the determination, resulting in the dramatically weakened photoinduced electron transfer (PET) effect and the disappearance of competition absorption. Thus, a highly sensitive ACP assay in the range of 0.22–12.5 U L−1 through fluorescence "turn-on" mode has been achieved with a detection of limit (LOD) of 0.064 U L−1. Meanwhile, the ACP activity can also be quantified by spectrophotometry based on the chromogenic reaction of the formed Fe2+ with 1,10-phenanthroline (Phen). Moreover, the designed nanosensor with good biocompatibility was successfully applied to image and monitor the ACP levels in living cells. We believe that the proposed method has remarkable advantages and potential application for ACP assay in terms of the high accuracy, simplicity, low cost, as well as its adequate sensitivity. [Display omitted] • Fe3+ functionalized on CIS/ZnS QD is employed to construct the sensing platform. • The mechanism of much greater efficiency for Fe3+ quencher than Fe2+ is elucidated. • A novel fluorometric and colorimetric dual-mode method is established for ACP assay. • The sensing platform shows high analytical performance for AA and ACP assay. • CIS/ZnS@Fe nanosensor can image the activity change of intracellular ACP. [ABSTRACT FROM AUTHOR]

A sensitive method for the detection of β-glucuronidase was established using functionalized carbon dots (β-CD-SiCDs) as fluorescent probes. The β-CD-SiCDs were found to be obtained through in situ autopolymerization by mixing the solutions of methyldopa, mono-6-ethylenediamine-β-cyclodextrin and N -(β-aminoethyl)-γ-aminopropyltrimethoxysilane at room temperature. The method has the characteristics of low energy consumption, simple and rapid. β-CD-SiCDs exhibited green fluorescence at 515 nm emission with a quantum yield of 7.9 %. 4-nitrophenyl-β-D-glucuronide was introduced as a substrate for β-glucuronidase to generate p -nitrophenol. Subsequently, p -nitrophenol self-assembled with β-CD-SiCDs through host-guest recognition to form a stable inclusion complex, resulting in the fluorescence quenching of β-CD-SiCDs. The linear range of β-CD-SiCDs for detecting β-glucuronidase activity was 0.5–60 U L−1 with a detection limit of 0.14 U L−1. For on-site detection, gel reagents were prepared by a simple method and the images were visualized and quantified by taking advantage of smartphones, avoiding the use of large instrumentation. The constructed fluorescence sensing platform has the benefits of easy operation and time saving, and has been successfully used for the detection of β-glucuronidase activity in serum and cell imaging. [Display omitted] • Amination induced in situ self-polymerization formation of β-CD-SiCDs without external energy. • β-CD-SiCDs can selectively recognize p -nitrophenol through host-guest recognition. • Smartphone-integrated hydrogel sensing platform was used to detect β-glucuronidase on site. • The approach is suitable for detecting β-glucuronidase in serum and bioimaging in cells. [ABSTRACT FROM AUTHOR]

Abstract In this work, we report a novel sensor for colorimetric and fluorometric H 2 O 2 sensing which is based on silver nanoparticles decorated and tetraphenylethene probe doped silica nanoparticles (Ag@TPE-SiO 2 NPs). A positively charged tetraphenylethene (TPE) probe is doped into silica nanoparticles, and the nanoparticles exhibit strong fluorescence emission due to aggregation-induced emission (AIE) of the TPE probe. Ag nanoparticles (AgNPs) are prepared in situ on the surface of the silica nanoparticles. AgNPs serve as a nanoquencher which can quench the AIE emission of the TPE-SiO 2 NPs efficiently. However, AgNPs can be oxidized to Ag+ by H 2 O 2 , which leads to fluorescence recovery and color fading of the Ag@TPE-SiO 2 NPs. The dual-readout strategy allows sensitive analysis of H 2 O 2. The detection limit of the fluorometric and colorimetric assay is 0.28 and 2.1 μM, respectively. And the nanosensor also shows good selectivity. In addition, analysis of H 2 O 2 in human serum and intracellular imaging of H 2 O 2 are both demonstrated. With the good analytical properties of merit, the proposed nanoprobe has a promising potential for H 2 O 2 related bioanalysis and biomedical applications. Graphical abstract fx1 Highlights • A sensor based on AgNPs decorated and TPE probe doped silica NPs was fabricated. • This dual-mode colorimetric and fluorometric sensor was employed for H 2 O 2 sensing. • The determination of H 2 O 2 in human serum was demonstrated. • The nanosensor was successfully employed for intracellular imaging of H 2 O 2. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • One-step green synthesis of high quantum yield (QY = 27.00%) carbon dots (N-CDs) from bauhinia flower. • The N-CDs proved to be an effective “turn-off” fluorescent sensor for Fe3+ recognition with the detection limit of 0.01 μM. • A “turn-on” fluorescent ATP sensor was developed based on the N-CDs-Fe3+ system with the detection limit of 0.005 μM. • The fluorescent sensors could be used in semiquantitative imaging intracellular Fe3+ and ATP successfully. • The “off-on” fluorescent sensors also could determine Fe3+ and ATP in biological samples with satisfying results. Abstract In this work, for the first time, natural bauhinia flower was adopted as a carbon source to prepare nitrogen-doped carbon dots (N-CDs) through facile and green microwave method without further passivation or modification. The fluorescent quantum yield (QY = 27.00%) of the as-synthesized N-CDs was higher than most of CDs prepared from other natural sources. The N-CDs was proved to be an effective “turn-off” fluorescent sensor for detection of Fe3+ exhibiting excellent sensitivity with the detection limit of 0.01 μM. The fluorescence of N-CDs-Fe3+ system would be recovered when ATP was added mainly due to high affinity of the adenosine triphosphate (ATP) for Fe3+ through Fe-O-P bonds. Therefore, a sensitive and reliable “turn-on” fluorescent ATP sensor was developed, the limit detection was calculated to be 0.005 μM. In addition, the fluorescent sensors could act as a good candidate to determine Fe3+ and ATP in biological samples with satisfying results. What’s more, the application of the fluorescent sensors for imaging Fe3+ and ATP in living cells, which suggested that the systems had great potential applications in biosensing and bioimaging. [ABSTRACT FROM AUTHOR]

Human telomerase is a ribonucleoprotein complex consisting of telomerase RNA and telomerase reverse transcriptase that catalyzes the addition of (TTAGGG) n repeat sequences to the 3′-end of the telomere. As almost all malignant cells overexpress telomerase, and it is seen as a diagnostic and prognostic cancer biomarker. Consequently, accurate and reliable quantification of telomerase activity is essential in medical diagnostics. A series of novel probes of telomerase activity, including quantum dot-based biosensors, gold nanoparticles, and mesoporous silica nanoparticles, and novel fluorescent labels such as aggregation induced emission (AIE) luminogens and conjugated polymer, have recently been developed and tested. This review describes the available fluorescence assays of extracellular and in situ telomerase activity. Current challenges and future research directions are discussed. [ABSTRACT FROM AUTHOR]

Peroxynitrite (ONOO − ) is one of the endogenous reactive oxygen species (ROS), which causes damage to a wide array of molecular components in the cells, including DNA and proteins, owing to its high oxidizing as well as nitrating properties. However, the precise pathogenic roles played by this substance in biological systems have not yet been elucidated completely owing to its short lifetime, high reactivity, low concentration and elusive nature in the in vivo applications. Thus, the development of more sensitive and selective techniques for detecting ONOO − , with high biocompatibilities, sensitivities, and site-specificities, is a significant goal. This review summarizes the recent advances that have been made in developing fluorescent sensors for ONOO − and their biological applications in diverse living systems. [ABSTRACT FROM AUTHOR]

The development of fluorescent probes for detection of glutathione (GSH) has attracted extensive attentions due to its close association with cellular functions and diseases. Herein, a fluorescence enhancement sensing system based on acetaldehyde-modified-cystine (AMC) is reported for the detection of thiols, providing detection limits of 36 and 52 μmol L −1 for GSH and cysteine (Cys) respectively. Importantly, the fluorescence response of AMC is highly selective toward thiols with respect to the coexisting species in real biological matrixes. Considering the fact that GSH levels in cancer cells is significantly higher than those of Cys and other reducing species, the fluorescence enhancing response of AMC in cancer cells is dominated by GSH. Therefore, this provides the possibility for selective intracellular GSH imaging in living cancer cells, i.e., HeLa cells in the present study. [ABSTRACT FROM AUTHOR]

Carbon dots (CDs) have gained great attention as multifunctional materials because of their interesting properties and general applicability. However, there are some reports for the preparation of highly luminescent green-emitting CDs (G-CDs), although these reports seem not to be extensible. Herein, new G-CDs (quantum yield: 27.2%) were synthesized from a facile hydrothermal treatment of p -aminosalicylic acid and ethylene glycol dimethacrylate as both carbon and nitrogen source and cross-linking agent, respectively. The chemical composition and optical properties of the as-prepared G-CDs were successfully investigated using transmission electron microscopy, atomic force microscopy, dynamic light scattering, X-ray diffraction, energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy and fluorescence and UV–vis spectroscopies. Interestingly, the fluorescence intensity of G-CDs was selectivity quenched by Fe 3+ in the range of 0.05–10.0 µmol Lˉ 1 , with a detection limit of 13.7 nmol Lˉ 1 . Meanwhile, ascorbic acid found to reduce Fe 3+ to Fe 2+ , thereby causing restoration of the fluorescence of G-CDs. The detection limit for ascorbic acid detection was estimated as 82.0 nmol Lˉ 1 over a linear range from 0.2 to 11.0 µmol Lˉ 1 . Furthermore, the designed sensing platform was successfully utilized to the detection of Fe 3+ and ascorbic acid in water and urine samples and to intracellular imaging without surface modification. [ABSTRACT FROM AUTHOR]

Intracellular uptake, distribution and metabolism of lipids are tightly regulated characteristics in healthy cells. An analytical technique capable of understanding these characteristics with a high level of species specificity in a minimally invasive manner is highly desirable in order to understand better how these become disrupted during disease. In this study, the uptake and distribution of three different alkyne tagged fatty acids in single cells were monitored and compared, highlighting the ability of Raman spectroscopy combined with alkyne tags for better understanding of the fine details with regard to uptake, distribution and metabolism of very chemically specific lipid species. This indicates the promise of using Raman spectroscopy directly with alkyne tagged lipids for cellular studies as opposed to subsequently clicking of a fluorophore onto the alkyne for fluorescence imaging. [ABSTRACT FROM AUTHOR]

In this work, for the first time, biomass-derived carbon dots (AMP-CDs) with strong water solubility, antioxidant activity and good biocompatibility were synthesized by a one-step microwave method using Allium macrostemon Bunge polysaccharides (AMP) as the main carbon source, L-cysteine as the nitrogen and sulfur source, and phosphoric acid as the phosphorus source. The results showed that sphere-like AMP-CDs with an average particle size of about 2.34 ± 0.49 nm were successfully prepared, with good resistance to salt and photobleaching, and maintained high fluorescence intensity under normal pH conditions in human body. AMP-CDs were highly resistant to 2,2-diphenyl-1-pycrylhydrazyl (DPPH), 2,2′-Azinobis- (3-ethylbenzthiazoline-6-sulphonate) (ABTS) and hydroxyl radical (·OH) with significantly higher scavenging ability than AMP, with IC 50 (μg/mL) of 10.240, 7.265, and 574.730, respectively. In addition, AMP-CDs can be selectively used for the sensitive detection of Cr6+ with the limit of detection was 5.25 μM, and satisfactory results were obtained for the Cr6+ recovery experiments of actual environmental samples. In vitro cytotoxicity and hemolytic activity assays showed that AMP-CDs have good biocompatibility and can smoothly enter cells for clear imaging. Therefore, AMP-CDs are likely expected to be applied as a potential antioxidant and metal ion detection probe in the field of drug and food, environmental and biological scenario samples for metal ion detection analysis. [Display omitted] • For the first time, foodborne Allium macrostemon Bunge polysaccharides (AMP) are synthesized into carbon dots by a fast (only 160s), simple, and safe microwave approach. • The antioxidant activity of synthetic carbon dots (AMP-CDs) is significantly higher than that of AMP. • Cr (VI) detection based on static quenching mechanism and internal filtering effect has been applied in food and environmental samples with satisfactory recovery results. • Bio-based carbon dots can be applied for clear intracellular imaging with good biocompatibility. [ABSTRACT FROM AUTHOR]

Through the orthogonal design of two fluorophores and two recognition groups, a series of fluorescent probes were developed from the flavone derivatives for hydrogen sulfide (H 2 S). The probe FlaN-DN stood out from the primarily screening on the selectivity and response intensities. Among the recent reported probes for the H 2 S detection, FlaN-DN indicated the most highlighted advantages including the rapid response (within 200 s) and the high response multiplication (over 100 folds). Moreover, FlaN-DN suggested practical capabilities including a wide linear range (0–400 μM), a relatively high sensitivity (limit of detection 0.13 μM), and high selectivity towards H 2 S. As a low cytotoxic probe, FlaN-DN achieved the imaging in living HeLa cells. FlaN-DN could detect the endogenous generation H 2 S and visualize the dose-dependent responses to the exogenous H 2 S level. [Display omitted] • A series of fluorescent probes for hydrogen sulfide developed from flavone derivatives. • Highlighted advantages including the rapid response within 200 s and the high response multiplication. • Practical capabilities including a wide linear range, a relatively high sensitivity, and high selectivity. • Achieveing the imaging of endogenous generation and exogenous H 2 S in living HeLa cells. In this work, through the orthogonal design of two fluorophores and two recognition groups, a series of fluorescent probes were developed from the flavone derivatives for hydrogen sulfide (H 2 S). The probe FlaN-DN stood out from the primarily screening on the selectivity and response intensities. It could respond to H 2 S with both the chromogenic and fluorescent signals. Among the recent reported probes for the H 2 S detection, FlaN-DN indicated the most highlighted advantages including the rapid response (within 200 s) and the high response multiplication (over 100 folds). FlaN-DN was sensitive to the pH condition, thus could be applied to distinguish the cancer micro-environment. Moreover, FlaN-DN suggested practical capabilities including a wide linear range (0–400 μM), a relatively high sensitivity (limit of detection 0.13 μM), and high selectivity towards H 2 S. As a low cytotoxic probe, FlaN-DN achieved the imaging in living HeLa cells. FlaN-DN could detect the endogenous generation H 2 S and visualize the dose-dependent responses to the exogenous H 2 S level. This work provided a typical case of natural-sourced derivatives as functional implements, which might inspire the future investigations. [ABSTRACT FROM AUTHOR]

A highly sensitive glutathione probe based on silicon quantum dots (SiQDs) modified with MnO 2 nanosheets has been developed. A strong reduction of the blue fluorescence of the SiQDs happened due to the surface energy transfer (SET) from SiQDs to the deposited MnO 2 . Fluorescence can be restored in the presence of glutathione on account of the MnO 2 nanosheets are reduced. A fluorometric glutathione detection assay with a low detection limit (153 nM, at an S/N ratio of 3) can be designed via this method. It can be applied to directly determine GSH in living cells. A significant blue fluorescence image is produced in the cytosol of the cell and the fluorescence disappears while the cells treated with scavenger of GSH. [ABSTRACT FROM AUTHOR]

The design of robust tools for hypochlorous acid (HClO) detection at subcellular level is highly desired for the better understanding of its biological function in cellular signaling pathways. Herein, we report the development of a two-photon fluorescent probe (TPFP) for lysosome-targetable HClO detection through the integration of a lysosome-targetable group (aminoethyl)morpholine, two-photon fluorophore 1,8-naphthalimide and HClO capturing phenyl-thiourea together. In the presence of HClO, the thiourea moiety is oxidized to urea and thereby restores the fluorescence of 1,8-naphthalimide(at 538 nm) due to the inhibition of photo-induced electron transfer (PET) effect. As is demonstrated in the spectroscopic characterizations, the probe TPFP exhibits excellent probing performance toward HClO, including short response time (<30 s), outstanding selectivity, high photostability and low detection limit (∼5.7 nM). In addition, it is confirmed that TPFP displays promising cell-membrane permeability and high specificity toward HClO in lysosomes through the one-photon and two-photon intracellular fluorescent microscopic imaging experiments. As a consequence, this lysosome-targetable two-photon fluorescent probe provides a promising platform for HClO detection at subcellular level and would inspire the design of plummy tools for other analytes detection. [ABSTRACT FROM AUTHOR]

Docosanol is an over-the-counter topical agent that has proved to be one of the most effective therapies for treating herpes simplex labialis. However, the mechanism by which docosanol suppresses lesion formation remains poorly understood. To elucidate its mechanism of action, we investigated the uptake of docosanol in living cells using coherent anti-Stokes Raman scattering microscopy. Based on direct visualization of the deuterated docosanol, we observed highly concentrated docosanol inside living cells 24 h after drug treatment. In addition, different spatial patterns of drug accumulation were observed in different cell lines. In keratinocytes, which are the targeted cells of docosanol, the drug molecules appeared to be docking at the periphery of the cell membrane. In contrast, the drug molecules in fibroblasts appeared to accumulate in densely packed punctate regions throughout the cytoplasm. These results suggest that this molecular imaging approach is suitable for the longitudinal tracking of drug molecules in living cells to identify cell-specific trafficking and may also have implications for elucidating the mechanism by which docosanol suppresses lesion formation. [ABSTRACT FROM AUTHOR]

Whether as an important biological element or as a radioactive source/medicine, the monitoring of trace levels of cobalt ions (Co) has become a non-negligible factor for human health and green environment. Current technologies for the detection of Co are cost-expensive and time-consuming, and require cumbersome sample pretreatment process. Herein a novel sensing platform has been developed for Co detection based on the quenching of the enhanced fluorescence signal of polyamine functionalized C-dots. Amine groups at the surface of the C-dots can capture Zn 2+ /Cd 2+ to form coordination compound, which can inhibit the photoinduced electron transfer pathways of C-dots and then induce the fluorescence enhancement of the C-dots by ∼80% margin. Also, Co interacts with these amine groups to form an absorbent complex, which can strongly quench the enhanced fluorescence of C-dots via an inner filter effect. This C-dots-based probe showed a wide linear response to Co with a concentration ranging from 0.012 to 12 μM, and a detection limit of 8.0 nM and RSD of 5.7% (n = 5). Significantly, the C-Dots exhibit excellent properties, such as negligible cytotoxicity, excellent biocompatibility, low-cost and high photostability, etc., which make C-dots favorable for label-free monitoring of Co and then successfully applied to the confocal imaging of intracellular Co. [ABSTRACT FROM AUTHOR]

Intramolecular catalytic hairpin assembly (intraCHA) has recently been developed. However, non-nucleic acid-initiated intraCHA is rarely explored. The only protein-initiated intraCHA depends on the unwarrantable binding affinity between protein and its aptamer, which generally results in limited initiation efficiency. Herein, a "repaired and initiated" intraCHA (RI-intraCHA) nanosystem was designed and its operation was reported for amplified imaging of DNA repair enzyme activity in live cells. 8-oxoguanine (8-OG) DNA glycosylase was selected as the model DNA repair enzyme. The RI-intraCHA nanosystem was constructed by linking a dsDNA (containing 8-OG sites and trigger strand), two hairpins to different vertexes of DNA tetrahedron. The nanosystem could independently enter into live cells in virtue of cell permeability of DNA tetrahedron. Upon repair action of endogenous 8-OG DNA glycosylase, intraCHA reaction in the nanosystem was initiated efficiently, generating amplified fluorescence signal. The nanosystem provided a detection limit of 0.2443 U/mL for 8-OG DNA glycosylase, which was lower than that of the reported imaging approaches. Furthermore, the nanosystem exhibited satisfactory biosafety and biostability, achieving amplified imaging of intracellular 8-OG DNA glycosylase activity. The designed RI-intraCHA nanosystem provided a promising tool for the research of basic biology of intracellular DNA repair enzymes as well as their clinic correlations. Schematic representation of the "repaired and initiated" intramolecular catalytic hairpin assembly (RI-intraCHA) nanosystem for amplified imaging the activity of intracellular 8-oxoguanine (8-OG) DNA glycosylase (a model DNA repair enzyme). [Display omitted] • "Repaired and initiated" intramolecular catalytic hairpin assembly system was showed. • The system depended on the repair action of 8-oxoguanine DNA glycosylase. • High efficient initiation of intramolecular catalytic hairpin assembly was achieved. • The system entered cells independently with satisfactory biosafety and biostability. • Amplified imaging intracellular 8-oxoguanine DNA glycosylase activity was realized. [ABSTRACT FROM AUTHOR]