A novel pencil graphite electrode modified with an iron-based conductive metal-organic framework exhibited good ability in simultaneous sensing bisphenol A and bisphenol S.

Bisphenol A (BPA) and its substitute bisphenol S (BPS) are desirable materials widely used in manufacturing plastic products but can pose carcinogenic risks to humans. A new conductive iron-based metal-organic framework (Fe-HHTP)-modified pencil graphite electrode (PGE) for electrochemically sensing BPA and BPS was prepared and fully characterized by SEM, TEM, FT-IR, XRD, and XPS. Results showed that the optimal conditions for preparing Fe-HHTP/PGE were a pH of 6.5, a Fe-HHTP concentration of 2 mg·mL-1, a deposition potential of 0 V, and a deposition time of 100 s. The Fe-HHTP/PGE prepared under such conditions harbored a significant electrocatalytic activity with a detection limit of 0.8 nM for BPA and 1.7 nM for BPS (S/N = 3). Correspondingly, the electrochemical response current was linearly correlated to BPA and BPS, ranging from 0.01 to 100 µM. Fe-HHTP/PGE also obtained satisfactory recoveries by 93.8-102.1% and 96.0-101.3% for detecting BPA and BPS in plastic food packaging samples. Our work has provided a novel electrochemical tool to simultaneously detect BPA and BPS in food packaging samples and environmental matrixes.

Adjustable luminescence copper nanoclusters nanoswitch based on competitive coordination of samarium ions for cascade detection of adenosine triphosphate and acid phosphatase activity.

Benefit from the strong coordination property, lanthanide metal ions have been used as competitive reagents to modulate the fluorescence changes of the system. However, lanthanide metal ions as inducers for aggregation-induced emission enhancement in nanosystems is rare. Herein, we report a "turn on-off-on" fluorescent switch for cascade detection of acid phosphatase (ACP) and adenosine triphosphate (ATP) based on the competitive coordination of samarium ions (Sm3+). Novel copper nanoclusters (CuNCs) with long wavelength emission (614 nm) stabilized by glutathione (GSH) and glycylglycine (Gly-Gly) have been confirmed to have AIE property. With the continuous aggregation of GSH/Gly-Gly CuNCs under the induction of Sm3+, the fluorescence of the system increased to achieve the "turn-on" process. The coordinated behaviour between Sm3+ and GSH/Gly-Gly CuNCs is discussed. Due to the strong metal coordination ability of ATP, the Sm3+ coordinated with the GSH/Gly-Gly CuNCs is competed out, resulting in the fluorescence "turn-off" process of the system. As the substrate of enzymatic hydrolysis of ACP, with the continuous hydrolysis of ATP by ACP, Sm3+ coordinates with GSH/Gly-Gly CuNCs again, which leads to the AIE effect and realize the fluorescence "turn-on" process of the system. This strategy results in ATP linear range of 0.508 ~ 120.0 µM with a detection limit of 0.508 µM (S/N = 3) and ACP linear range of 0.011 ~ 30.0 U·L-1 with a detection limit of 0.011 U·L-1 (S/N = 3). Application to biologic samples was successful.

Fabrication of novel electrochemical sensor based on bimetallic Ce-Ni-MOF for sensitive detection of bisphenol A.

In this paper, a novel bimetallic Ce-Ni metal-organic frameworks (Ce-Ni-MOF) are synthesized by hydrothermal reaction, using 1,3,5-benzenetricarboxylic acid as a ligand. In particular, the bimetallic Ce-Ni-MOF with the largest specific surface area and catalytic sites was synthesized when the molar ratio of Ce3+ to Ni2+ was 3:7. Bimetallic Ce-Ni-MOF is added to the traditional conductive material of multiwall carbon nanotubes (MWCNTs) to play their synergistic effect, improve the conductivity, specific surface area, and catalytic site of the MWCNTs. A novel bisphenol A (BPA) sensor was successfully prepared by a self-assembled multilayer strategy of Ce-Ni-MOF/MWCNTs modified glassy carbon electrodes (GCE). Field emission scanning electron microscopy, powder X-ray diffraction, and transmission electron microscope were carried out to characterize the Ce-Ni-MOF/MWCNTs. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used as a sensitive analytical method for the determination of BPA, and a wider linear dynamic range of BPA determination in 0.1 µmol·L-1 to 100 µmol·L-1 with a detection limit of 7.8 nmol·L-1 (S/N = 3). The proposed method was applied to measure the content of BPA in different brands of drinking water with satisfying recovery from 97.4 to 102.4%. Graphical abstract.

Highly sensitive aptamer based on electrochemiluminescence biosensor for label-free detection of bisphenol A.

Bisphenol A (BPA), a typical endocrine disruptor, is widely used as a key monomer in the packaging industry. Residual monomer can transfer from the package material to the food and thereby pose a risk to the health of the consumer, so determination of BPA migration is highly important for food safety control. In this study, a simple but sensitive electrochemiluminescence (ECL) biosensor, which combines the characteristics of high selectivity of an aptamer and high sensitivity of ECL, has been developed to detect BPA from package materials. The aptamer was immobilized on a gold electrode surface through Au-S interaction. The aptamer was then hybridized with complementary DNA (CDNA) to form double-stranded DNA (dsDNA). Ru(phen)32+ can intercalate into the grooves of dsDNA and acts as an ECL indicator; high ECL intensity can therefore be detected from the electrode surface. In the presence of BPA, which can competitively bind with the aptamer owing to their high affinity, Ru(phen)32+ is released from the electrode surface and the ECL of the system is decreased. The decreasing ECL signal has a linear relationship with BPA in the range of 0.1-100 pM with a detection limit of 0.076 pM. The developed biosensor has been applied to detect migration of BPA from different categories of canned drink with satisfactory results.

Electrochemical Sensor Based on Glassy-Carbon Electrode Modified with Dual-Ligand EC-MOFs Supported on rGO for BPA.

The electronic conductive metal-organic frameworks (EC-MOFs) based on a single ligand are not suitable for the accurate detection of bisphenol A (BPA) due to the limitations of their electron-transfer-based sensing mechanism. To overcome this drawback, we developed EC-MOFs with novel dual-ligands, 2,3,6,7,10,11-hexahydroxy-sanya-phenyl (HHTP) and tetrahydroxy 1,4-quinone (THQ), and metal ions. A new class of 2D π-conjugation-based EC-MOFs (M-(HHTP)(THQ)) was synthesized by a self-assemble technique. Its best member (Cu-(HHTP)(THQ)) was selected and combined with reduced graphene (rGO) to form a Cu-(HHTP)(THQ)@rGO composite, which was thoroughly characterized by X-ray diffraction, field scanning electron microscopy, and energy-dispersive X-ray spectroscopy. Cu-(HHTP)(THQ)@rGO was drop-cast onto a glassy carbon electrode (GCE) to obtain a sensor for BPA detection. Cyclic voltammetry and electrochemical impedance tests were used to evaluate the electrode performance. The oxidation current of BPA on the Cu-(HHTP)(THQ)@rGO/GCE was substantially higher than on unmodified GCE, which could be explained by a synergy between Cu-(HHTP)(THQ) (which provided sensing and adsorption) and rGO (which provided fast electron conductivity and high surface area). Cu-(HHTP)(THQ)@rGO/GCE exhibited a linear detection range for 0.05-100 µmol·L-1 of BPA with 3.6 nmol·L-1 (S/N = 3) detection limit. We believe that our novel electrode and BPA sensing method extends the application perspectives of EC-MOFs in the electrocatalysis and sensing fields.

Cathodic electrochemiluminescent behavior of luminol at nafion-nano-TiO2 modified glassy carbon electrode.

The electrochemiluminescence (ECL) behavior of luminol on a nafion-nano-TiO(2) modified glassy carbon electrode (nafion-nano-TiO(2)--GCE) was studied. Two ECL peaks (ECL-1 and ECL-2) were found during cathodic potential scanning. ECL-1 at ca -0.4 V (vs Ag--AgCl reference electrode) came from the reaction between luminol and active oxygen anion produced at the GCE surface directly, while ECL-2 at ca -0.9 V (vs Ag--AgCl reference electrode) came from the reaction between luminol and the active oxygen anion catalyzed by TiO(2.) The possible mechanism for the generation of both ECL peaks has been proposed. The reproducibility of the ECL intensities on nafion-nano-TiO(2)--GCE at ECL-1 and ECL-2 was good, with relative standard deviations (n = 10) of 4.3 and 1.3%, respectively. The ECL-2 generated at the nafion-nano-TiO(2)--GCE surface was further developed to detect the dissolved oxygen, and a detection limit of 0.02 mg/L was achieved. The proposed method was applied to detect dissolved oxygen in water with satisfactory result.

An electrochemical sensor based on a glassy carbon electrode modified with sandwich structured ZIF-67@rGO for bisphenol A measurement.

The low conductivity of metal-organic frameworks seriously impedes their electrocatalytic performance. In this study, we prepared a fabricated sandwich structure composed of a Co-based zeolitic imidazolate framework (ZIF-67) and reduced graphene oxide (rGO) through a facile and simple one-pot hydrothermal reaction. This framework of nanocomposites, which are modified with a glassy carbon electrode, constructed a bisphenol A (BPA) electrochemical sensor for the first time. Operational parameters such as pH, electrolytes, the amount of modifiers, deposition potentials and deposition time were optimised for the sensitive detection of BPA. The performance of electrodes was evaluated by cyclic voltammetry, electrochemical impedance spectroscopy, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction and transmission electron microscopy. With differential pulse voltammetry, the detection concentration of BPA ranged from 0.05 µmol L-1 to 100 µmol L-1. The results revealed that the hierarchical nanocomposites demonstrated better electrocatalytic performance with large electrochemically active surface areas, high sensitivity and a low limit of detection (5.2 nmol L-1), compared with a physical mixture of ZIF-67 and rGO at the same ratio. These impressive features originate from the synergistic effects of ZIF-67 and rGO. This study presents a new strategy using metal-organic framework composite materials for the sensitive detection of BPA.

Doxorubicin-loaded bacterial outer-membrane vesicles exert enhanced anti-tumor efficacy in non-small-cell lung cancer.

More efficient drug delivery system and formulation with less adverse effects are needed for the clinical application of broad-spectrum antineoplastic agent doxorubicin (DOX). Here we obtained outer-membrane vesicles (OMVs), a nano-sized proteoliposomes naturally released by Gram-negative bacteria, from attenuated Klebsiella pneumonia and prepared doxorubicin-loaded O0MVs (DOX-OMV). Confocal microscopy and in vivo distribution study observed that DOX encapsulated in OMVs was efficiently transported into NSCLC A549 cells. DOX-OMV resulted in intensive cytotoxic effects and cell apoptosis in vitro as evident from MTT assay, Western blotting and flow cytometry due to the rapid cellular uptake of DOX. In A549 tumor-bearing BALB/c nude mice, DOX-OMV presented a substantial tumor growth inhibition with favorable tolerability and pharmacokinetic profile, and TUNEL assay and H&E staining displayed extensive apoptotic cells and necrosis in tumor tissues. More importantly, OMVs' appropriate immunogenicity enabled the recruitment of macrophages in tumor microenvironment which might synergize with their cargo DOX in vivo. Our results suggest that OMVs can not only function as biological nanocarriers for chemotherapeutic agents but also elicit suitable immune responses, thus having a great potential for the tumor chemoimmunotherapy.

[Determination of 61 organophosphorous pesticide residues in fruits, vegetables, milk, vegetable oils and animal muscles by dispersive solid-phase extraction and ultra performance liquid chromatography-tandem mass spectrometry].

A dispersive solid-phase extraction coupled with ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed for the determination of 61 organophosphorous pesticide residues in fruits, vegetables, milk, vegetable oils and animal muscles. The fruit, vegetable and milk samples were extracted with acetonitrile and separated with salting out method; vegetable oil samples were dissolved by n-hexane, and extracted with acetonitrile; animal muscle samples were extracted with acetonitrile-water assisted by n-hexane and separated with salting out method. And then the supernatants were purified using dispersive solid-phase extraction (C18 and primary secondary amine powder) prior to the UPLC-MS/MS analysis. The analytes were indentified in positive electrospray ionization (ESI+) and multiple reaction monitoring (MRM) mode. The matrix-matched external standard calibration curves were used for quantitative analysis. Under the optimal conditions, the detection limits (S/N > or = 10) of the method were 0.01 mg/kg. The recoveries were 62.8%-107%, and the relative standard deviations (RSDs) were in the range of 4.2%-19%. The method has the advantages of easy, fast, and more sensitive, and can meet the requirement of the determination of organophosphorous pesticide residues in the foods.