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DNA‐based probes have gained significant attention as versatile tools for biochemical analysis, benefiting from their programmability and biocompatibility. However, most existing DNA‐based probes rely on fluorescence as the signal output, which can be problematic due to issues like autofluorescence and scattering when applied in complex biological materials such as living cells or tissues. Herein, we report the development of bioluminescent nucleic acid (bioLUNA) sensors that offer laser excitation‐independent and ratiometric imaging of the target in vivo. The system is based on computational modelling and mutagenesis investigations of a genetic fusion between circular permutated Nano‐luciferase (NLuc) and HaloTag, enabling the conjugation of the protein with a DNAzyme. In the presence of Zn2+, the DNAzyme sensor releases the fluorophore‐labelled strand, leading to a reduction in bioluminescent resonance energy transfer (BRET) between the luciferase and fluorophore. Consequently, this process induces ratiometric changes in the bioluminescent signal. We demonstrated that this bioLUNA sensor enabled imaging of both exogenous Zn2+in vivo and endogenous Zn2+ efflux in normal epithelial prostate and prostate tumors. This work expands the DNAzyme sensors to using bioluminescence and thus has enriched the toolbox of nucleic acid sensors for a broad range of biomedical applications. [ABSTRACT FROM AUTHOR]

Ferroptosis exhibits potential to damage drug‐resistant cancer cells. However, it is still restricted with the "off‐target" toxicity from the undesirable leakage of metal ions from ferroptosis agents, and the lack of reliable imaging for monitoring the ferroptosis process in living systems. Herein, we develop a novel ternary alloy PtWMn nanocube as a Mn reservoir, and further design a microenvironment‐triggered nanoplatform that can accurately release Mn ions within the tumor to increase reactive oxygen species (ROS) generation, produce O2 and consume excess glutathione for synergistically enhancing nonferrous ferroptosis. Moreover, this nanoplatform exerts a responsive signal in high‐field magnetic resonance imaging (MRI), which enables the real‐time report of Mn release and the monitoring of ferroptosis initiation through the signal changes of T1‐/T2‐MRI. Thus, our nanoplatform provides a novel strategy to store, deliver and precisely release Mn ions for MRI‐guided high‐specificity ferroptosis therapy. [ABSTRACT FROM AUTHOR]

Genetically encoded fluorescent proteins (FPs) have been used for metal ion detection. However, their applications are restricted to a limited number of metal ions owing to the lack of available metal‐binding proteins or peptides that can be fused to FPs and the difficulty in transforming the binding of metal ions into a change of fluorescent signal. We report herein the use of Mg2+‐specific 10–23 or Zn2+‐specific 8–17 RNA‐cleaving DNAzymes to regulate the expression of FPs as a new class of ratiometric fluorescent sensors for metal ions. Specifically, we demonstrate the use of DNAzymes to suppress the expression of Clover2, a variant of the green FP (GFP), by cleaving the mRNA of Clover2, while the expression of Ruby2, a mutant of the red FP (RFP), is not affected. The Mg2+ or Zn2+ in HeLa cells can be detected using both confocal imaging and flow cytometry. Since a wide variety of metal‐specific DNAzymes can be obtained, this method can likely be applied to imaging many other metal ions, expanding the range of the current genetically encoded fluorescent protein‐based sensors. [ABSTRACT FROM AUTHOR]

Abstract: Gold nanoparticles-based colorimetric assay possesses several unique advantages, and has been applied for a wide range of targets, varying from nucleic acids to different metal ions. However, due to the lack of proper coordinating ligand, gold nanoparticles-based colorimetric sensing system for Au3+ has not been developed so far. It is well-known that Au3+ could induce the oxidation transition of thiol compounds to disulfide compounds. In this article, for the first time we converted such thiol masking reaction into colorimetric sensing system for label-free detection of Au3+ via a target-controlled aggregation of nanoparticles strategy. In the new proposed sensing system, fluorosurfactant-capped gold nanoparticles were chosen as signal reporter units, while an Au3+-triggered oxidation of cysteine (Cys), which inhibited the aggregation of gold nanoparticles, acted as the recognition unit. By varying the amount of Cys, a tunable response range accompanied with different windows of color change could be obtained for Au3+, illustrating the universality of the sensing system for Au3+ samples with different sensitivity requirements. Under optimized condition, the proposed sensing system exhibits a high sensitivity towards Au3+ with a detection limit of 50nM, which is lower than previously reported spectroscopic methods. It has also been applied for detection of Au3+ in practical water samples with satisfactory result. [Copyright &y& Elsevier]

Quinoline-appended rhodamine B thiohydrazide based fluorescent probe was designed and applied in fluorescent detections of mercury ions in both aqueous solution and living cells. The signal change of the probe is based on a specific metal ion induced reversible ring-opening mechanism of a rhodamine B thiohydrazide. The probe exhibits a dynamic response concentration range for Hg2+ from 1.0 × 10-8 to 1.0 × 10-5 M with a detection limit of 8.5 × 10-9 M. The fluorescent probe is pH independent in medium condition and exhibits high selectivity over other common metal ions. [ABSTRACT FROM AUTHOR]

Abstract: In the present paper, we describe the fabrication and analytical characteristics of fluorescence-based zinc ion-sensing glass slides. To construct the sensor, a benzoxazole derivative 4-benzoxazol-2′-yl-3-hydroxyphenyl allyl ether (1) with a terminal double bond was synthesized and copolymerized with 2-hydroxyethyl methacrylate (HEMA) on the activated surface of glass slides by UV irradiation. In the absence of Zn2+ at pH 7.24, the resulting optical sensor emitted fluorescence at 450nm via excited-state intramolecular proton transfer (ESIPT). Upon binding with Zn2+, the ESIPT process was inhibited resulting in a 46nm blue-shift of fluorescence emission. Thus, the proposed sensor can behave as a ratiometric fluorescent sensor for the selective detection of Zn2+. In addition, the sensor shows nice selectivity, good reproducibility and fast response time. Cd2+ did not interfere with Zn2+ sensing. The sensing membrane demonstrates a good stability with a lifetime of at least 3 months. The linear response range covers a concentration range of Zn2+ from 8.0×10−5 to 4.0×10−3 mol/L and the detection limit is 4.0×10−5 mol/L. The determination of Zn2+ in both tap and river water samples shows satisfactory results. [Copyright &y& Elsevier]

Abstract: N-Methyl-α,β,γ,δ-tetraphenylporphine (NMTPPH) has been used to detect trace amount of zinc ions in ethanol–water solution by fluorescence spectroscopy. The fluorescent probe undergoes a fluorescent emission intensity enhancement upon binding to zinc ions in EtOH/H2O (1:1, v/v) solution. The fluorescence enhancement of NMTPPH is attributed to the 1:1 complex formation between NMTPPH and Zn(II) which has been utilized as the basis for the selective detection of Zn(II). The linear response range covers a concentration range of Zn(II) from 5.0×10−7 to 1.0×10−5 mol/L and the detection limit is 1.5×10−7 mol/L. The fluorescent probe exhibits high selectivity over other common metal ions except for Cu(II). [Copyright &y& Elsevier]

Abstract: In this paper, 2-(2′-hydroxy-phenyl)-4(3H)-quinazolinone (HPQ), a typical compound that exhibits excited state intramolecular proton transfer (ESIPT) reaction and possesses good photophysical properties, is synthesized and used as fluoroionophore for Fe3+ sensitive optochemical sensor. The decrease of fluorescence intensity of HPQ membrane upon the addition of Fe3+ was attributed to the blocking of ESIPT reactions of HPQ and quenching its fluorescence. The effect of the composition of the sensing membrane was studied, and experimental conditions were optimized. The sensor shows a linear response toward Fe3+ in the concentration range of 7.1×10−7 M to 1.4×10−4 M with a limit of detection of 8.0×10−8 M, and a working pH range from 2.5 to 4.5. It shows excellent selectivity for Fe3+ over a large number of cations such as alkali, alkaline earth and transitional metal ions. The proposed sensor is applied to the determination of the content of iron ions in pharmaceutical preparations samples with satisfactory results. [Copyright &y& Elsevier]

A highly selective electrochemical biosensor for the ultrasensitive detection of Hg2+in aqueous solution has been developed based on the strong and specific binding of Hg2+by two DNA thymine bases (T–Hg2+–T) and the use of AuNP-functionalized reporter DNA to achieve signal amplification. [ABSTRACT FROM AUTHOR]

Abstract: The design and synthesis of a porphyrin-appended terpyridine, 5-(4-([2,2′:6′,2″]-terpyridin-4-yl-carboxyamidyl)phenyl)-10,15,20-triphenylporphyrin (H2TPPTPy) and its application as potential fluoroionophore for recognition of metal ions are reported. For preparation of the fluoroionophore, a novel simple strategy with improved total yield has been applied for the synthesis of 2,2′:6′,2″-terpyridine-4′-carboxylic acid as a ligand. H2TPPTPy shows chelation-enhanced fluorescence effect with cadmium ion via the interruption of photoinduced electron transfer (PET) process, which has been utilized as the basis of the fabrication of the Cd(II)-sensitive fluorescent chemosensor. The analytical performance characteristics of the proposed Cd(II)-sensitive chemosensor were investigated. It shows a linear response toward Cd(II) in the concentration range of 3.2×10−6 to 3.2×10−4 M with a limit of detection of 1.2×10−6 M. The chemosensor shows good selectivity for Cd(II) over a large number of cations, such as alkali, alkali earth and transitional metal ions except Cu(II) and Zn(II). The sensor has been used for determination of Cd(II) in water samples with satisfactory recoveries. [Copyright &y& Elsevier]

DNAzyme-based catalytic beacons have been widely studied for both in vivo and in vitro molecular detection. However, only a few label-free catalytic beacons with excellent analytical performance have been reported so far. In this work, by combining a catalytic DNAzyme for amplified sensing through enzymatic turnover with cleavage-induced G-quadruplex formation, a label-free DNAzyme biosensor was developed for amplified “turn-on” fluorescence detection of Pb 2+ with a detection limit of 3 nM. The method is very competitive compared to many other labeled or label-free methods with or without signal amplification. Due to the inherent specificity of the GR-5 DNAzyme, the method also exhibits excellent selectivity. This biosensor successfully detected Pb 2+ in river water samples with high sensitivity and selectivity. Such a method might provide a universal DNAzyme-based sensing platform for sensitive detection of various targets both in environmental and biomedical fields. [ABSTRACT FROM AUTHOR]

Abstract: Development of fluorescent probes for Hg2+ has become a hot topic in modern chemical research due to its high toxicity. In this paper, we for the first time report the synthesis and application of a thioether spirocyclic rhodamine B derivative (TR) as an efficient fluorescent probe for Hg2+. TR was synthesized using a simple procedure under mild condition. By employing a thioether spirocycle instead of classic spirolactam as recognition unit, our proposed probe TR is acidity-insensitive, and exhibits a pH-independent and ultrasensitive response to Hg2+. The probe works well within a wide pH range from 3.5 to 11.5, and exhibits a 350-fold fluorescence enhancement upon 0.5equiv of Hg2+ triggered, with a detection limit of 2.5nM estimated for Hg2+. In virtue of the strong thiophilic characteristic of Hg2+, the response of the probe to Hg2+ is instantaneous and highly selective, which make it favorable for cellular Hg2+ imaging applications. It has been preliminarily used for highly sensitive monitoring of Hg2+ level in living cells with satisfying resolution, demonstrating its value of the practical applications in biological systems. [Copyright &y& Elsevier]

Abstract: A aggregation-induced emission-based fluorescent probe 1 for Zn2+ was designed and simply synthesized by condensation of salicylaldehyde with aqueous hydrazine. The experimental conditions were first optimized. It was found that N, N-Dimethylformamide (DMF) was the best solvent for the Zn2+-triggered aggregation of compound 1 compared with other solvents. The emission intensity was gradually increased, accompanied by the simultaneous red shift of the maximum emission peak with increasing Zn2+ concentrations. A red shift about 45 nm was achieved when Zn2+ concentration is 100 μM. Compared with other Zn2+ fluorescent sensors based on aggregation-induced emission (AIE), compound 1 can detect a lower concentration of Zn2+ with a detection limit of 0.1 μM. Compound 1 also exhibited good selectivity toward Zn2+. The aggregation was verified by the dynamic light scattering (DLS) results, with a Zn2+ concentration-dependent size observed. It was also directly confirmed by TEM analyses. [Copyright &y& Elsevier]