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In this paper, a novel fluorescent detection method for glucose and lactic acid was developed based on fluorescent iron nanoclusters (Fe NCs). The Fe NCs prepared using hemin as the main raw material exhibited excellent water solubility, bright red fluorescence, and super sensitive response to hydrogen peroxide (H2O2). This paper demonstrates that Fe NCs exhibit excellent peroxide-like activity, catalyzing H2O2 to produce hydroxyl radicals (•OH) that can quench the red fluorescence of Fe NCs. In this paper, a new type of glucose sensor was established by combining Fe NCs with glucose oxidase (GluOx). With the increase in glucose content, the fluorescence of Fe NCs decreases correspondingly, and the glucose content can be detected in the scope of 0–200 μmol·L−1 (μM). Similarly, the lactic acid sensor can also be established by combining Fe NCs with lactate oxidase (LacOx). With the increase in lactic acid concentration, the fluorescence of Fe NCs decreases correspondingly, and the lactic acid content can be detected in the range of 0–100 μM. Furthermore, Fe NCs were used in the preparation of gel test strip, which can be used to detect H2O2, glucose and lactic acid successfully by the changes of fluorescent intensity. [ABSTRACT FROM AUTHOR]

Bilirubin is a key biomarker in the diagnosis of jaundice. Herein, we proposed a simple and convenient quantitative method for the fluorescent detection of bilirubin. We developed a copper nanoclusters coated by zinc-based metal-organic frameworks (Cu NCs@MOF). The prepared Cu NCs@MOF exhibited bright blue fluorescence excited with ultra-violet light and well stability at various environments. More importantly, Cu NCs@MOF was used for bilirubin detection based on the emerging red fluorescence emission peak induced by bilirubin. Furthermore, Cu NCs@MOF were made into test strip for the visual detection of bilirubin by the fluorescence color variation. [ABSTRACT FROM AUTHOR]

In this work, we developed a simple route to synthesize green fluorescence carbon nanoparticles (FCPs) at room temperature with dopamine and p-phenylenediamine as raw materials. The FCPs exhibited a salient fluorescence emission peak at 525 nm and well stability in the intricate surroundings. Only Cu2+ ions could significantly inhibited the fluorescence of FCPs and could be successfully detected in the concentration scope of 0–200 µmol·L−1 based on the fluorescence quenching of FCPs. The Cu2+ ion-quenched fluorescence of FCPs system can be further recovered by the addition of dipicolinic acid (DPA) and could be utilized for DPA detection within the dynamic scope of 10–150 µmol·L−1. [ABSTRACT FROM AUTHOR]

In this paper, bovine serum albumin served as the initial materials for preparing a kind of cyan-emitting fluorescent protein nanoparticles (BSA NPs). The BSA NPs were further adopted as a template to synthesize protein nanoparticles-stabilized silver nanoclusters (BSA NPs@Ag NCs) that offered two well-separated fluorescence emission peaks respectively at 470 nm and 670 nm. Dopamine could specifically induce the fluorescence enhancement at 470 nm and the fluorescence quenching at 670 nm of BSA NPs@Ag NCs. Moreover, cupric ions could cause the fluorescence quenching at 670 nm of BSA NPs@Ag NCs just with a negligible impact on the fluorescence intensity at 470 nm. The BSA NPs@Ag NCs can serve as a ratiometric probe for detection of dopamine and cupric ions. [ABSTRACT FROM AUTHOR]

In this paper, we prepared fluorescence-tunable water-soluble CdS quantum dots (QDs) with hexametaphosphate as stabilizers by a simple route. The prepared CdS QDs were utilized to detect calcium ion (Ca 2+ ) based on an obvious fluorescence enhancement of CdS QDs induced by Ca 2+ . The results demonstrated there was an excellent linear relationship between the fluorescence intensity of hexametaphosphate-capped CdS QDs and Ca 2+ concentration in the range from 10 μmol/L to 400 μ mol/L and the detection limit for Ca 2+ was 4 μmol/L. Furthermore, fluoride ions (F − ) can react with Ca 2+ to generate the insoluble calcium fluoride that would inhibit the Ca 2+ -induced fluorescence enhancement of CdS QDs. Therefore, the designed Ca 2+ -induced fluorescence enhancement system was also able to effectively detect fluoride. [ABSTRACT FROM AUTHOR]

In this study, we reported a simple and sensitive fluorescence nanosensor for rapid detection of amifostine and alkaline phosphatase (ALP). The novel nanosensor was based on the fluorescence “turn on-off” of CdS quantum dots (QDs). Firstly, Cd 2+ cation could react with S 2− anion to generate fluorescent CdS QDs in the presence of amifostine. The fluorescence (FL) intensity of amifostine-capped CdS QDs (Amifostine-CdS QDs) was increased with the increasing amounts of amifostine, and could be used for amifostine detection. However, amifostine could be converted to 2-(3-aminopropylamino) ethanethiol (WR1065) in the presence of ALP based on the dephosphorylation of ALP. Under the optimum conditions, the affinity of WR1065 to CdS QDs was weaker than that of amifostine. Therefore the new generation of WR1065-CdS QDs would reduce the FL intensity with the increase of ALP concentration, and the fluorescence of CdS QDs was turn off. The metabolic process of amifostine in the presence of alkaline phosphatase could be also studied via the change of FL intensity of CdS QDs. The present method was cost-effective, convenient, and does not require any complicated synthetic procedures. [ABSTRACT FROM AUTHOR]

In this paper, a simple and sensitive sensing strategy for the determination of Pb 2+ ions was designed, in which anticancer drug AGRO100, a guanine (G)-quadruplex DNA aptamer, was selected as the probe to detect Pb 2+ ions and graphene oxide (GO) was adopted as the fluorescence quencher. A dye-labeled AGRO100 aptamer in a flexible single stranded state could be adsorbed on the surface of GO, and the fluorescence was quenched via Förster resonance energy transfer (FRET) from fluorescence dyes to GO. AGRO100 can interact with Pb 2+ ions to form an intermolecular G-quadruplex/Pb 2+ complex, which has a weaker binding affinity with GO. By this way, the dyes were kept away from the GO sheet and the fluorescence was restored. Thus the AGRO100 aptamer could be used as a fluorescence probe for the determination of Pb 2+ ions. Under the optimized conditions, there was a good linear relationship between the fluorescence intensity of the dyes and the concentration of Pb 2+ ions in the range from 0.75 to 6.0 nmol/L with a detection limit of 0.40 nmol/L. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we have developed a simple and rapid method for the detection of Pb2+ based on the DNA sequence capped CdS quantum dots (QDs). We utilized the designed guanine (G)-rich DNA sequence (PS2.M) as a coating reagent to synthesize the DNA-capped CdS QDs. The designed G-rich DNA sequence PS2.M can bind with hemin to form G-quadruplex/hemin complex with K+, accompanied by the fluorescence quenching of CdS QDs via the photoinduced electron transfer. Pb2+ can induce conformational changes in the G-quadruplex/hemin complex to release the hemin molecules, so the quenched fluorescence of CdS QDs could be recovered. Therefore, the new fluorescent analysis system could be applied for the detection of Pb2+ based on the label-free DNA sequence capped CdS QDs. [Copyright &y& Elsevier]

[Display omitted] • The dual emission polymer carbon nanoparticles PDA-OPD were synthesized. • The PDA-OPD exhibited dual emission peaks at 460 nm and 540 nm upon single excitation wavelength. • The PDA-OPD can be used for detection of pH value in the range from 3.0 to 7.4. • The PDA-OPD can be used for detection of bilibrubin in the alkaline environment. Herein, we prepared a novel fluorescent polymer carbon nanoparticles by polymerizing dopamine (DA) and o-phenylenediamine (OPD) through oxidation of hydrogen peroxide. In a neutral environment, the synthesized fluorescent polymer carbon nanoparticles (PDA-OPD) exhibited two emission peaks at 460 nm and 540 nm with 400 nm excitation wavelength. In an acidic environment, the fluorescence emission peaks of PDA-OPD at 540 nm showed an obvious fluorescence quenching, and there existed a good linear relationship between the fluorescence ratio F 540 /F 460 and environment pH value. In an alkaline environment, the fluorescence emission peak at 460 nm showed obvious fluorescence quenching after the addition of bilirubin, while a novel fluorescence emission peak at 560 nm emerged gradually. The PDA-OPD could be also used to detect bilirubin in the range of 0–400 μmol·L−1. [ABSTRACT FROM AUTHOR]

In this paper, we developed dopamine functionalized–CdTe quantum dots as fluorescence probes for the determination of l-histidine. Firstly, CdTe was covalently linked to dopamine to form a kind of fluorescence sensor with pyrocatechol structure on the surface. The photoluminescence intensity of CdTe–dopamine (QDs–DA) could be quenched by Ni2+ due to the strong coordination interaction between the pyrocatechol structure of QDs–DA and Ni2+. In the presence of l-histidine, Ni2+ preferred to bind with l-histidine due to high affinity of Ni2+ to l-histidine and the photoluminescence intensity of QDs–DA was recovered. The recovered photoluminescence intensity of QDs–DA was proportional to the concentration of l-histidine in the ranges of 1.0×10−6–1.0×10−4 molL−1 and the detection limit was 5.0×10−7 molL−1 respectively. The established method showed a good selectivity for l-histidine among other common amino acids, and it was applied for determination of l-histidine in human serum sample with satisfactory results. [ABSTRACT FROM AUTHOR]

We have developed a simple and efficient fluorescence detection system for lysozyme utilizing I–III–VI type Cu–In–S ternary quantum dots (CuInS2 QDs) as the probe. Water-soluble near-infrared CuInS2 QDs capped with 3-mercaptopropionic acid were directly synthesized by using a hydrothermal method. Poly(dimethyl diallyl ammonium chloride), as a cationic polyelectrolyte, could bind to 3-mercaptopropionic acid-capped CuInS2 QDs via electrostatic interactions that would lead to fluorescence quenching of CuInS2 QDs. And the addition of a lysozyme aptamer could effectively turn on the quenched fluorescence due to the stronger interaction between the cationic polyelectrolyte and negatively charged aptamer. The addition of lysozyme would result in fluorescence quenching of CuInS2 QDs again due to the specific binding between lysozyme and the lysozyme aptamer. Therefore, this label-free fluorescence system could be applied to selectively detect lysozyme. [ABSTRACT FROM AUTHOR]

Highlights: [•] Cd2+ reacts with S2− to generate fluorescent CdS QDs with ATP. [•] ATP can be hydrolyzed by the enzymatic dephosphorylation of ALP. [•] Fluorescent CdS QDs could not be generated in the presence of ALP. [•] The analysis system was successfully applied to assay ATP and ALP. [ABSTRACT FROM AUTHOR]

Highlights: [•] The water-soluble CuInS2 QDs was functionalized with dopamine molecules. [•] The fluorescence of the dopamine functionalized CuInS2 QDs was sensitive to pH value changes. [•] Urea would release OH− to change the pH value with urase as the catalyst. [•] The dopamine functionalized CuInS2 QDs could be utilized as a fluorescence probe for urea. [ABSTRACT FROM AUTHOR]

Abstract: A novel sensing strategy for specific recognition of hemoglobin has been designed. In the presence of trypsin, hemoglobin was cleaved to release heme which could effectively bind to a FITC-labeled guanine (G)-rich oligonucleotide sequence to form the G-quadruplex/hemin complex. This binding process would lead to fluorescence quenching of FITC via photoinduced electron transfer. Therefore, a fluorescence assay for the determination of hemoglobin could be established. Under the optimized conditions, there was a linear relationship between the fluorescence intensity of probe DNA and the hemoglobin concentration in the range of 5–200nmol/L, with the limit of detection (LOD) as low as 2nmol/L. [Copyright &y& Elsevier]

Abstract: In this paper, a sensitive and simple method for the determination of melamine (MA) was developed based on the fluorescence changes of the water-soluble CuInS2 quantum dots (QDs). The water-soluble CuInS2 QDs capped by mercaptopropionic acid (MPA) was directly synthesized by hydrothermal method based on our previous report. The fluorescence emission of CuInS2 QDs was quenched by the oxidation of the surface of the QDs with H2O2, and the quenched fluorescence of CuInS2 QDs could be recovered upon the addition of small amounts of MA, which might be due to the surface passivation of the CuInS2 QDs by MA. The other amino acids such as glycine and lysine had no effect on the quenched fluorescence of CuInS2 QDs. Under optimum conditions, there was a good linear relationship between the fluorescence intensity of CuInS2 QDs and the concentration range of MA from 1.0×10−8 to 1.0×10−5 mol/L with a detection limit as low as 5nM. The proposed method was successfully applied to detect trace MA in raw milk with satisfactory results. Compared with previous reports, the proposed method manifested several advantages such as high sensitivity, short analysis time, low cost and ease of operation. [Copyright &y& Elsevier]

[Display omitted] • A novel route for the synthesis of fluorescent iron nanoclusters in aqueous solution was synthesized. • The fluorescence emission peak of iron nanoclusters were adjustable from red to blue fluorescence. • The fluorescence of iron nanoclusters can be used for monitoring the changes of pH value. • The fluorescence of iron nanoclusters can be inhibited significantly by hydroxyl radical. In this work, we developed a novel route for the synthesis of fluorescent iron nanoclusters (Hb-Fe NCs) in aqueous solution with natural protein and amino acid as the original materials. Moreover, the fluorescence emission of Hb-Fe NCs were adjustable from red to blue fluorescence by regulating the dosage of sodium hydroxide in the synthesis process. We have examined the fluorescence response of Hb-Fe NCs in various temperature, metal ions or biomolecules environment, and exhibited excellent stability in the complex environment. Furthermore, the fluorescence of Hb-Fe NCs gradually enhanced as the pH value of environment increased from 5.0 to 9.0. More importantly, the fluorescence of Hb-Fe NCs can be inhibited significantly by hydroxyl radical (OH·). [ABSTRACT FROM AUTHOR]

A fluorescent suspension array combining digital encoding and molecular imprinting technologies was applied for multiplexed detection of phenols in aqueous medium. In this assay, nanomaterials such as silver (Ag), cuprous oxide (Cu 2 O), magnesium oxide (MgO), and zinc oxide (ZnO) were assembled on microbeads as digital encoding signal sources, then, (Digital encoding signal sources were produced by assembling silver (Ag), cuprous oxide Cu2O), magnesium oxide (MgO), and zinc oxide (ZnO) on microbeads. Molecular imprinted nanoparticles based on CdSe/ZnS quantum dots with various emission wavelengths (525, 565 and 585 nm) were grafted on the encoded beads through electrostatic adsorption and were used as the sensing units. The decoding spectra of the suspension array were stimulated and collected by a home-built laser induced breakdown spectroscopy system. The resulted spectra were transformed into digital sequences for encoding. As demonstrated in the gradient detections to various phenol solutions in concentration range of 0.98–62.5 μg/mL, the functionality of the suspension array was proven in the control experiments between the parent sensor beads and the molecular imprinting silica nanoparticles assembled sensor beads. Furthermore, the selectivity of suspension array was verified by the mixed adsorption experiments conducted in multicomponent analytes. [ABSTRACT FROM AUTHOR]

To achieve the dual-channel (analog and digital) encoding, microbeads assembled with quantum dots (QDs) and element coding nanoparticles (ECNPs) have been prepared. Dual-spectra, including fluorescence generated from quantum dots (QDs) and laser induced breakdown spectrum obtained from the plasma of ECNPs, including AgO, MgO and ZnO nanoparticles, has been adopted to provide more encoding amounts and more accurate dual recognition for encoded microbeads in multiplexed utilization. The experimental results demonstrate that the single microbead can be decoded in two optical channels. Multiplexed analysis and contrast adsorption experiment of anti-IgG verified the availability and specificity of dual-channel-coded microbeads in bioanalysis. In gradient detection of anti-IgG, we obtained the linear concentration response to target biomolecules from 3.125 × 10 −10  M to 1 × 10 −8  M, and the limit of detection was calculated to be 2.91 × 10 −11  M. [ABSTRACT FROM AUTHOR]

A list of the most dangerous bacteria that are multiple-drug resistance has been published by WHO, among which are various Gram-positive bacteria related with serious healthcare and community-associated infection. An effort is called for developing new strategies to combat the resistance, and nanomaterial-based approaches provide an ideal potential to mitigate the antimicrobial resistance as an alternative to antibiotics. Nanoscale zero-valent iron particles exhibited a good antimicrobial activity by triggering Fenton reaction, however, no zero-valent iron nanoclusters are developed as antimicrobial medical materials. In this work, a novel ultra-small zero-valent iron nanoclusters (usZVIN) was synthesized by one-step reduction in aqueous solutions, which exhibited bright red fluorescence at 616 nm. Interestingly, the usZVIN displayed an excellent selectively antibacterial activity against Gram-positive bacteria, and little effects on Gram-negative bacteria. The killing efficiency of usZVIN against S. aureus can reach 100 % with a concentration of 40 μg mL−1 after 1 h incubation, whereas there is no killing effect of usZVIN against E.coli even with a concentration of 900 μg mL−1 for 4 h. The antimicrobial mechanism of usZVIN was demonstrated to be the intracellular reactive oxygen species (ROS) production triggered by usZVIN due to its excellent peroxidase-like activity. Collectively, our findings suggested that usZVIN is a good medical-material candidate for fighting against Gram-positive bacterial infections, especially when we need leave beneficial Gram-negative bacteria intact. [Display omitted] • An ultra-small iron nanocluster with red fluorescence was prepared in aqueous phase. • The usZVIN were synthesized with endogenous hemin and histidine as raw materials. • The usZVIN exhibited a significant peroxidase-like activity. • The usZVIN displayed excellent antibacterial activity against Gram-positive bacteria. [ABSTRACT FROM AUTHOR]