Fuquan Dang

Biomass-derived highly porous functional carbon fabricated by using a free-standing template for efficient removal of methylene blue

Banana peel (BP), a biomass waste, was converted into a valuable highly porous functional carbon material (HPFCM) by a general chelate-assisted co-assembly process. The HPFCMs were fabricated by using Al(III)-based metal-organic framework-like as a free-standing template and commercial Pluronic F127 as a microstructure-directing agent. Several critical variables for fabrication including doses of Al(III) and F127, carbonization temperature had been optimized and the adsorption behavior of HPFCMs was examined by using methylene blue as dye model compound. The optimal adsorbent was validated as HPFCMs-5-1-800, and its equilibrium data were well fitted to the Langmuir isotherm model with a monolayer adsorption capacity of 385.12 mg g(-1) at ambient temperature. The surface physical properties of HPFCMs-5-1-800 were also exemplarily characterized. The findings revealed that the free-standing template is a potential route for preparation of HPFCM from waste BP.

Fluorescent DNA-Protected Silver Nanoclusters for Ligand–HIV RNA Interaction Assay

Studying ligand-biomacromolecule interactions provides opportunities for creating new compounds that can efficiently regulate specific biological processes. Ribonucleic acid (RNA) molecules have become attractive drug targets since the discovery of their roles in modulating gene expression, while only a limited number of studies have investigated interactions between ligands and functional RNA molecules, especially those based on nanotechnology. DNA-protected silver nanoclusters (AgNCs) were used to investigate ligand-RNA interactions for the first time in this study. The anthracycline anticancer drug mitoxantrone (MTX) was found to quench the fluorescence of AgNCs. After adding human immunodeficiency virus trans-activation responsive region (TAR) RNA or Rev-response element (RRE) RNA to AgNCs-MTX mixtures, the fluorescence of the AgNCs recovered due to interactions between MTX with RNAs. The binding constants and number of binding sites of MTX to TAR and RRE RNA were determined through theoretical calculations. MTX-RNA interactions were further confirmed in fluorescence polarization and mass spectrometry experiments. The mechanism of MTX-based fluorescence quenching of the AgNCs was also explored. This study provides a new strategy for ligand-RNA binding interaction assay.

Size-selective QD@MOF core-shell nanocomposites for the highly sensitive monitoring of oxidase activities

In this work, we proposed a novel and facile method to monitor oxidase activities based on size-selective fluorescent quantum dot (QD)@metal-organic framework (MOF) core-shell nanocomposites (CSNCPs). The CSNCPs were synthesized from ZIF-8 and CdTe QDs in aqueous solution in 40min at room temperature with stirring. The prepared CdTe@ZIF-8 CSNCPs , which have excellent water dispersibility and stability, displays distinct fluorescence responses to hole scavengers of different molecular sizes (e.g., H2O2, substrate, and oxidase) due to the aperture limitation of the ZIF-8 shell. H2O2 can efficiently quench the fluorescence of CdTe@ZIF-8 CSNCPs over a linearity range of 1-100nM with a detection limit of 0.29nM, whereas large molecules such as substrate and oxidase have very little effect on its fluorescence. Therefore, the highly sensitive detection of oxidase activities was achieved by monitoring the fluorescence quenching of CdTe@ZIF-8 CSNCPs by H2O2 produced in the presence of substrate and oxidase, which is proportional to the oxidase activities. The linearity ranges of the uricase and glucose oxidase activity are 0.1-50U/L and 1-100U/L, respectively, and their detection limits are 0.024U/L and 0.26U/L, respectively. Therefore, the current QD@MOF CSNCPs based sensing system is a promising, widely applicable means of monitoring oxidase activities in biochemical research.

Spectroscopic quantification of 5-hydroxymethylcytosine in genomic DNA using boric acid-functionalized nano-microsphere fluorescent probes ☆

5-hydroxymethylcytosine (5hmC) is the sixth base of DNA. It is involved in active DNA demethylation and can be a marker of diseases such as cancer. In this study, we developed a simple and sensitive 2-(4-boronophenyl)quinoline-4-carboxylic acid modified poly (glycidyl methacrylate (PBAQA-PGMA) fluorescent probe to detect the 5hmC content of genomic DNA based on T4 β-glucosyltransferase-catalyzed glucosylation of 5hmC. The fluorescence-enhanced intensity recorded from the DNA sample was proportional to its 5-hydroxymethylcytosine content and could be quantified by fluorescence spectrophotometry. The developed probe showed good detection sensitivity and selectivity and a good linear relationship between the fluorescence intensity and the concentration of 5 hmC within a 0-100nM range. Compared with other fluorescence detection methods, this method not only could determine trace amounts of 5 hmC from genomic DNA but also could eliminate the interference of fluorescent dyes and the need for purification. It also could avoid multiple labeling. Because the PBAQA-PGMA probe could enrich the content of glycosyl-5-hydroxymethyl-2-deoxycytidine from a complex ground substance, it will broaden the linear detection range and improve sensitivity. The limit of detection was calculated to be 0.167nM after enrichment. Furthermore, the method was successfully used to detect 5-hydroxymethylcytosine from mouse tissues.

A novel peptide/Fe 3 O 4 @SiO 2 -Au nanocomposite-based fluorescence biosensor for the highly selective and sensitive detection of prostate-specific antigen

Highly selective and sensitive detection methods are very important for the early diagnosis of prostate-specific antigen (PSA). Here, we present a novel peptide/Fe3O4@SiO2-Au nanocomposite-based fluorescence biosensor for highly selective and sensitive detection of PSA. The biosensor was made by self-organizing 5-FAM labeled peptides onto the surface of magnetic Fe3O4@SiO2-Au nanocomposites (MNCPs), resulting in efficient quenching of the FAM fluorescence. The PSA specifically recognized and cleaved the 5-FAM-labeled peptides, leading to the fluorescence recovery. This is the first report of the MNCPs by in situ growth of Au nanoparticles (AuNPs) on the SiO2 encapsulated single Fe3O4 nanocubes. The MNCPs feature robust salt stability, and allow for effective fluorescence quenching and easy magnetic separation, which greatly decrease the background fluorescence. The peptide/MNCPs-based fluorescence biosensor measure a wide range of concentrations of PSA, from 1.0 × 10-12 to 1.0 × 10-9g/mL, with a limit of detection (LOD) of 3.0 × 10-13g/mL in both standard solutions and serum samples, demonstrating the great potential of this biosensor platform for use in clinical and biological assays.

Lysozyme-mediated fabrication of well-defined core–shell nanoparticle@metal–organic framework nanocomposites

We report a versatile strategy based on self-assembled lysozymes (LYZs) to prepare core–shell nanocomposites with nanoparticles (NPs) in metal–organic frameworks (MOFs). We first demonstrated that LYZs can readily self-organize into a robust coating layer with abundant functional groups on the surfaces of various NPs, making it possible to mediate the heterogeneous nucleation and growth of MOFs for the structural integration of a broad range of NPs and functional MOFs. Two kinds of core–shell NP@MOF nanocomposites with monocrystalline-shell and polycrystalline-shell structures are obtained depending on the size of the NPs. The readily tunable structures added additional possibilities to tailor the functionalities of the nanocomposites by sandwiching nanostructures between the core and shell. When coupled with soft lithography, the LYZ-based method allows for fabricating the arrays of carbon dot (CD)@Tb-MOFs on a microscope glass slide with micro-sized resolution within minutes, which unlocked a possible opportunity for precisely engineering NP@MOF arrays on solid substrates. The proposed method shows competitive advantages including ease of interfacial functionalization, simple and mild conditions, and structural tunability for constructing NP@MOF nanocomposites, which have great potential applications in many fields such as catalysis, sensors, biomedicine, and tissue engineering.

Ratiometric fluorescence sensor based on cholesterol oxidase-functionalized mesoporous silica nanoparticle@ZIF-8 core-shell nanocomposites for detection of cholesterol

A novel ratiometric fluorescence sensing system based on cholesterol oxidase-functionalized dual-color mesoporous silica nanoparticles (MSNs)@metal-organic framework core-shell nanocomposite is demonstrated for cholesterol detection. MSNs were first loaded with 5-aminofluorescein (AF) inside pores and then wrapped with red-emission CdTe quantum dots (QDs) on the surface to seal in the dye molecules, forming the signal displaying unit (AF-MSN-QDs). Next, AF-MSN-QDs were encapsulated with zeolitic imidazolate framework (ZIF-8) to form a transition layer with distinct size-selectivity, which not only protected the cores from corrosion but also greatly decreased background interference from large molecules. More significantly, the ZIF-8 shells showed high affinity for most enzymes, which made it possible for cholesterol oxidase (ChOx) to self-organize on the surface of ZIF-8-encapsulated AF-MSN-QDs via chemo-physical adsorption, forming novel core-shell nanocomposites (AF-MSN-QD@ZIF-8-ChOx) as a sensing platform for cholesterol detection. The detectable signal was monitored by enzymatic product-quenching fluorescence of the QDs. The fluorescence changes of I520/I618 showed excellent linearity with H2O2 concentrations in the range of 5-100 nM, with a limit of detection (LOD) as low as 0.89 nM. As a proof-of-concept, cholesterol was selectively detected with beneficial LOD as low as 0.923 μg/mL, demonstrating the great potential of this biosensor platform for other biologically important molecules with H2O2-producing oxidases.

Fabrication of a porous β-cyclodextrin-polymer-coated solid-phase microextraction fiber for the simultaneous determination of five contaminants in water using gas chromatography-mass spectrometry

A novel solid-phase microextraction fiber coated with a porous β-cyclodextrin polymer was developed. The porous β-cyclodextrin polymer cross-linked using tetrafluoroterephthalonitrile, possessed well-distributed pores and the largest surface area among current β-cyclodextrin polymers. Scanning electron microscopy revealed that the coating had a continuous wrinkled and folded structure, which guarantees a sufficient loading capacity for contaminants. The properties of the developed fiber were evaluated using headspace solid-phase microextraction of five contaminants as model analytes coupled with gas chromatography-mass spectrometry. Owing to the advantages of a large surface area and three-dimensional cavities, the novel fiber exhibited excellent operational stability and extraction ability. After optimisation of the extraction conditions, including extraction temperature, extraction time, salt effect, and desorption time, validation of the method with water samples achieved good linearity over a wide range (0.01–120 μg L−1) and low detection limits (0.003–1.600 μg L−1). The single-fiber and fiber-to-fiber repeatabilities were 1.7–11.0% and 1.9–11.0%, respectively. The method was applied to the simultaneous analysis of five analytes with satisfactory recoveries (76.6–106.0% for pond water and 89.0–105.9% for rainwater).

A chimeric aptamers-based and MoS2 nanosheet-enhanced label-free fluorescence polarization strategy for ATP detection

Adenosine triphosphate (ATP) as a primary energy source plays a unique role in the regulation of all cellular events. The necessity to detect ATP requires sensitive and accurate quantitative analytical strategies. Herein, we present our study of developing a MoS2 nanosheet-enhanced aptasensor for fluorescence polarization-based ATP detection. A bifunctional DNA strand was designed to consist of chimeric aptamers that recognize and capture ATP and berberine, a fluorescence enhancer. In the absence of ATP, the DNA strand bound to berberine will be hydrolyzed when Exonuclease I (Exo I) is introduced, releasing berberine as a result. In contrast, when ATP is present, ATP aptamer folds into a G-quadruplex structure; thus, the complex can resist degradation by Exo I to maintain berberine for fluorescent detection purpose. In addition, to magnify the fluorescence polarization (FP) signal, MoS2 nanosheets were also adopted in the system. This nanosheets-enhanced FP strategy is simple and facile which does not require traditional dye-labeled DNA strands and complex operation steps. The developed fluorescence polarization aptasensor showed high sensitivity for the quantification of ATP with a detection limit of 34.4 nM, performing well both in buffer solution and in biological samples.