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DNA-templated fluorescent nanoclusters (NCs) have attracted increasing research interest on account of their prominent features, such as DNA sequence-dependent fluorescence, easy functionalization, wide availability, water solubility, and excellent biocompatibility. Coupling DNA templates with complementary DNA, aptamers, G-quadruplex, and so on has generated a large number of sensors. Additionally, the preparation and applications of DNA-templated fluorescent NCs in these sensing have been widely studied. This review firstly focuses on the properties of DNA-templated fluorescent NCs, and the synthesis of DNA-templated fluorescent NCs with different metals is then discussed. In the third part, we mainly introduce the applications of DNA-templated fluorescent NCs for sensing metal ions. At last, we further discuss the future perspectives of DNA-templated fluorescent NCs in the synthesis and sensing metal ions in the environmental and biological fields.

Single-molecule imaging technologies, especially those based on fluorescence, have been developed to probe both the equilibrium and dynamic properties of biomolecules at the single-molecular and quantitative levels. In this review, we provide an overview of the state-of-the-art advancements in single-molecule fluorescence imaging techniques. We systematically explore the advanced implementations of in vitro single-molecule imaging techniques using total internal reflection fluorescence (TIRF) microscopy, which is widely accessible. This includes discussions on sample preparation, passivation techniques, data collection and analysis, and biological applications. Furthermore, we delve into the compatibility of microfluidic technology for single-molecule fluorescence imaging, highlighting its potential benefits and challenges. Finally, we summarize the current challenges and prospects of fluorescence-based single-molecule imaging techniques, paving the way for further advancements in this rapidly evolving field. [ABSTRACT FROM AUTHOR]

Nucleocapsid protein (N protein) is an appropriate target for early determination of viral antigen-based severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We have found that β-cyclodextrin polymer (β-CDP) has shown a significant fluorescence enhancement effect for fluorophore pyrene via host–guest interaction. Herein, we developed a sensitive and selective N protein-sensing method that combined the host–guest interaction fluorescence enhancement strategy with high recognition of aptamer. The DNA aptamer of N protein modified with pyrene at its 3′ terminal was designed as the sensing probe. The added exonuclease I (Exo I) could digest the probe, and the obtained free pyrene as a guest could easily enter into the hydrophobic cavity of host β-CDP, thus inducing outstanding luminescent enhancement. While in the presence of N protein, the probe could combine with it to form a complex owing to the high affinity between the aptamer and the target, which prevented the digestion of Exo I. The steric hindrance of the complex prevented pyrene from entering the cavity of β-CDP, resulting in a tiny fluorescence change. N protein has been selectively analyzed with a low detection limit (11.27 nM) through the detection of the fluorescence intensity. Moreover, the sensing of spiked N protein from human serum and throat swabs samples of three volunteers has been achieved. These results indicated that our proposed method has broad application prospects for early diagnosis of coronavirus disease 2019. [ABSTRACT FROM AUTHOR]

Two-photon carbon-based nanoprobes hold great potential for biomedical applications as a result of their advantages of low fluorescence background, deep tissue imaging penetration and enhanced spatial resolution. However, the development of an activatable two-photon fluorescence carbon-based nanoprobe that simultaneously has the ability to target desired organs or cells is highly desired but remained a largely unsolved challenge. Herein, we developed boronate affinity BCNP@MnO2 nanocomposites, constructed by one step in situ growth of MnO2 nanosheets on the surface of aminophenylboronic acid-functionalized CNPs (BCNPs) via a redox reaction, which can feature efficient fluorescence energy transfer quenching to the BCNPs, allowing for tumor-specific affinity recognition and two-photon fluorescence activation imaging. By utilizing the inherent two-photon optical properties and sialic acid (SA) specific targeting ability of the BCNPs, good biocompatibility of the nanocomposites as well as highly sensitive and selective responses of MnO2 nanosheets towards GSH, the developed nanocomposites have demonstrated specific two-photon fluorescence activation imaging in target cancer cells and nude mouse tissues. Therefore, our proposed novel strategy could be used for monitoring GSH-triggered two-photon fluorescence activation events in SA-overexpressed cancer cells and has promising applications in both biological exploration and clinical diagnosis. [ABSTRACT FROM AUTHOR]

A novel tumor-selective catalytic nanosystem that enables efficient chemodynamic therapy (CDT) and activatable fluorescence imaging in H2O2-rich tumor microenvironments has been developed. [ABSTRACT FROM AUTHOR]

Two new homometallic coordination polymers 1 and 2 have been prepared by the directly one-step hydrothermal reactions of a carboxylate-functionalized salen ligand with Zn(II) and Co(II) ions, respectively. 1 exhibits a 3D open framework built by [Zn 4 (μ 4 -O)(carboxylate) 8 ] units and double Zn-salen ligands, while 2 shows a 1D chain structure constructed by cobalt ions and the ligand derived from the hydrolysis to one C N bond of salen ligand. The preliminary fluorescence measurements of 1 – 2 show the influence of structure on the property. [ABSTRACT FROM AUTHOR]

{[Mn3(bpt)2(bib)2(H2O)2]·(H2O)2}nand {[Cd(Hbpt)(bib)0.5(H2O)2]·(H2O)2}nwere obtained under solvothermal reactions of biphenyl-3,4′,5-tricarboxylic acid (H3bpt) and 1,4-bis(imidazolyl)benzene (bib). In1, the fully deprotonated bpt3−is a “Y-shape” and “X-shape” ligand, linking trinuclear manganese ions to generate a 2-D layer. The layer is further bridged by bpt3−to generate a 3-D wave-like zigzag structure. In2, Hbpt2−is a “V-shape” ligand, bridging metal centers to generate a sheet. The neighboring sheets are packed together in an ABAB mode to afford a 3-D supramolecular framework. Complex2exhibits intense fluorescence at room temperature, which may originate from a ligand-to-metal charge transfer. [ABSTRACT FROM AUTHOR]

In this study, a convenient, sensitive, rapid and simple method was developed on microfluidic chip which was integrated with on-line complexing and laser-induced fluorescence detection. A rhodamine derivative (RD) was developed as a fluorescent chemosensor for Hg(II). It exhibited high selective recognition toward Hg(II) over other examined metal ions in water samples. Under the optimized conditions, the response was linearly proportional to the concentration of Hg(II) in the range of 0–70 μM with a detection limit of 0.031 μM. Satisfactory repeatability and reproducibility were achieved, with a relative standard deviation (RSD) of 6.62%. The established method was successfully applied for the determination of Hg(II) in environmental water samples (surface water, tap water, and waste water). Recoveries obtained for the determination of Hg(II) in spiking samples ranged from 85% to 103%. [ABSTRACT FROM AUTHOR]

Highlights: [•] Regular hexagonal disks (NaLnF4) were synthesized by a simple hydrothermal method. [•] Much stronger UC and DC emissions were observed in NaLuF4-based disks. [•] Stronger fluorescence emissions in NaLuF4-based disks were explained reasonably. [•] NaLuF4-based disks can act as a removable luminescent platform for nano-assembly. [•] NaLuF4-based disks can be applied in improving efficiency of solar cells. [ABSTRACT FROM AUTHOR]

A separation using capillary electrophoresis with laser-induced fluorescence (CE-LIF) was applied to the study of green fluorescent protein tagged calmoldulin (GFP-CaM) that was expressed from Escherichia coli and purified with Ni2+-nitrilotriacetate (Ni-NTA) resin column. It was found that GFP-CaM not only has good fluorescence properties under various conditions similar to GFP, but also retains its calcium-binding ability as the native CaM. GFP-CaM was separated and detected by CE-LIF within 10 min with a limit-of-detection (LOD) of 2×10−10 M for an injection volume of 3 nl, higher than that of common chemical fluorescent-tagged protein method. The results indicated that, as a fluorescence probe, GFP could overcome the drawback of inefficient derivatization of chemical fluorescence probes. The interaction between the GFP-CaM and Ca2+ was studied in detail using affinity capillary electrophoresis with laser-induced fluorescence and the dissociation constant (Kd) between GFP-CaM and Ca2+ was determined to be 1.2×10−5 M, which is in good agreement with the literature values of untagged CaM (10−6 to 10−5 M) obtained by conventional method. As a preliminary application, the interaction between GFP-CaM and OsCBK was also investigated. The method makes it possible to screen the trace amounts of target proteins in crude extracts interacting with CaM under physiological conditions. [Copyright &y& Elsevier]

Abstract: We have observed the fluorescence emission of a monolayer of Rhodamine 6G coated on the surface of 32μm glass microsphere under 632.8nm excitation. The structural resonances of upconversion fluorescence around 550–580nm region were observed, which could be assigned by using the well-known Lorenz–Mie Formalism. [Copyright &y& Elsevier]