A Chemiluminescence Sensor for the Detection of α-Fetoprotein and Carcinoembryonic Antigen Based on Dual-Aptamer Functionalized Magnetic Silicon Composite.

In this work, a dual-aptamer functionalized magnetic silicon composite was prepared and used to construct a chemiluminescence (CL) sensor for the detection of α-fetoprotein (AFP) and carcinoembryonic antigen (CEA). First, SiO2@Fe3O4 was prepared, and polydiallyl dimethylammonium chloride (PDDA) and AuNPs were sequentially loaded on SiO2@Fe3O4. Subsequently, the complementary strand of CEA aptamer (cDNA2) and the aptamer of AFP (Apt1) were attached to AuNPs/PDDA-SiO2@Fe3O4. Then, the aptamer of CEA (Apt2) and G quadruplex peroxide-mimicking enzyme (G-DNAzyme) were sequentially connected to cDNA2, leading to the final composite. Then, the composite was used to construct a CL sensor. When AFP is present, it will combine with Apt1 on the composite to hinder the catalytic ability of AuNPs to luminol-H2O2, achieving AFP detection. When CEA is present, it will recognize and bind with Apt2, so G-DNAzyme is released to solution and catalyzes the reaction of luminol-H2O2 to achieve CEA determination. After the application of the prepared composite, AFP and CEA were detected in the magnetic medium and supernatant, respectively, after simple magnetic separation. Therefore, the detection of multiple liver cancer markers is realized through the CL technology without additional instruments or technology, which broadens the application range of CL technology. The sensor for detecting AFP and CEA shows wide linear ranges of 1.0 × 10-4 to 1.0 ng·mL-1 and 0.0001-0.5 ng·mL-1 and low detection limits of 6.7 × 10-5 ng·mL-1 and 3.2 × 10-5 ng·mL-1, respectively. Finally, the sensor was successfully used to detect CEA and AFP in serum samples and provides great potential for detection of multiple liver cancer markers in early clinical diagnosis.

A chemiluminescence aptasensor for sensitive detection of alpha-fetoprotein based on hemin@ZIF-67.

In this work, hemin@ZIF-67 composites were prepared and were used to construct a chemiluminescence (CL) aptasensor for alpha-fetoprotein (AFP) detection. Hemin is a catalytic porphyrin with two carboxylate groups that can covalently bond to metal ions. A hemin/ZIF-67 composite was prepared via covalent bonding between the carboxyl groups of hemin and the cobalt ion of ZIF-67, and these materials were characterized by scanning electron microscopy (SEM), infrared spectroscopy (IR), and X-ray diffraction (XRD). Hemin@ZIF-67 was used as the peroxidase material, and the aptamer of alpha-fetoprotein was modified on its surface by electrostatic adsorption. Then a simple CL aptasensor was constructed based on the CL system of luminol-H2O2-NaOH. Under the optimal conditions, the CL intensity value was linearly proportional to the concentration of AFP in the range of 4 × 10-10 to 200 × 10-10 mg/mL. The detection limit was 1.3 × 10-10 mg/mL. Thus the aptasensor enables highly sensitive and selective detection of AFP.

Populus euphratica Apyrases Increase Drought Tolerance by Modulating Stomatal Aperture in Arabidopsis.

Stomatal regulation is crucial to reduce water consumption under drought conditions. Extracellular ATP (eATP) serves as a signaling agent in stomatal regulation; however, it is less known whether the eATP mediation of stomatal aperture is linked to apyrases (APYs), the principal enzymes that control the concentration of eATP. To clarify the role of APYs in stomatal control, PeAPY1 and PeAPY2 were isolated from Populus euphratica and transferred into Arabidopsis. Compared with the wild-type Arabidopsis and loss-of-function mutants (Atapy1 and Atapy2), PeAPY1- and PeAPY2-transgenic plants decreased stomatal aperture under mannitol treatment (200 mM, 2 h) and reduced water loss during air exposure (90 min). The role of apyrase in stomatal regulation resulted from its control in eATP-regulated stomatal movements and increased stomatal sensitivity to ABA. The bi-phasic dose-responses to applied nucleotides, i.e., the low ATP (0.3-1.0 mM)-promoted opening and high ATP (>2.0 mM)-promoted closure, were both restricted by P. euphratica apyrases. It is noteworthy that eATP at a low concentration (0.3 mM) counteracted ABA action in the regulation of stomatal aperture, while overexpression of PeAPY1 or PeAPY2 effectively diminished eATP promotion in opening, and consequently enhanced ABA action in closure. We postulate a speculative model of apyrase signaling in eATP- and ABA-regulated stomatal movements under drought.

A chemiluminescence assay for determination of lysozyme based on the use of magnetic alginate-aptamer composition and hemin@HKUST-1.

Lysozyme aptamer-functionalized magnetic alginate hydrogel was prepared for separation and enrichment of lysozyme. Luminol-labeled aptamer was used as a signal tag, and the signal tag was adsorbed on magnetic carboxylated carbon nanotubes based on the π-interaction. When lysozyme was added, the aptamer specifically binds to the lysozyme, causing the signal tag to detach from the magnetic carboxylated carbon nanotubes. When the aptamer/lysozyme complex bound to the complementary single strand of aptamer on the hemin@HKUST-1, lysozyme was released. The released lysozyme can be recombined with the signal tag adsorbed on the magnetic carboxylated carbon nanotube, allowing more signal tag to be dispersed into the solution. Determination of lysozyme was achieved by releasing the luminol-labeled aptamer to generate a chemiluminescence signal at a wavelength of 425 nm. It was proved by experiments that the synthesized hemin@HKUST-1 had a strong catalytic effect on the luminol-NaOH-H2O2 system. The chemiluminescence signal was increased nearly 100 times. The complementary pairing allowed the luminol to be immobilized on the surface of hemin@HKUST-1. The generation and consumption of short-lived reactive oxygen species were concentrated on the surface of the MOFs, which improves the chemiluminescence efficiency. The introduction of hemin@HKUST-1 and DNA solved the defects of chemiluminescence analysis. The chemiluminescence assay was able to detect lysozyme with linear range of 1.05 × 10-6 U∙mg-1 (6.00 × 10-13 mol∙L-1)-1.25 × 10-2 U∙mg-1 (7.14 × 10-9 mol∙L-1); the detection limit was 3.50 × 10-7 U∙mg-1 (2.00 × 10-13 mol∙L-1) (R2 = 0.99). The recovery of lysozyme in spiked saliva samples was 97.4-102.8%. Graphical abstract Schematic presentation of chemiluminescence assay. Lysozyme (Lys) was captured by aptamer-modified magnetic sodium alginate (M-Alg-Apt); Glycine (pH = 2) as eluent for Lys. Luminol-modified Apt (Apt-luminol) as signal tag; magnetic carbon nanotubes (MCNTs) as adsorption matrix; cDNA was complementary to Apt; hemin@HKUST-1 as catalyst.

Electrochemical assays for determination of H2O2 and prostate-specific antigen based on a nanocomposite consisting of CeO2 nanoparticle-decorated MnO2 nanospheres.

A nanocomposite consisting of CeO2 nanoparticle-decorated MnO2 nanospheres (CeO2@MnO2) was synthesized for the first time via a hydrothermal method. CeO2@MnO2 was exploited to construct an electrochemical assays for detecting H2O2 and prostate-specific antigen (PSA) with square wave voltammetry (SWV). The electrochemical results proved that CeO2@MnO2 owned a better electrocatalytic effect towards H2O2 reduction than pure MnO2 NS and CeO2 NP due to the synergistic effect between MnO2 NS and CeO2 NP. Under optimized conditions, CeO2@MnO2-based assay can be applied to detect H2O2 in the range 1 to 3.0 × 103 µmol L-1. The label-free electrochemical immunoassay based on CeO2@MnO2 displayed linearly with concentrations of PSA from 0.005 to 50.0 ng mL-1. The electrochemical assays also possessed acceptable sensitivity, selectivity, and stability. The study showed that CeO2@MnO2 hold great potential as a biosensing platform and the clinical determination of tumor markers in human serum. Graphical abstract A nanocomposite consisting of CeO2 nanoparticles decorated MnO2 nanospheres (CeO2 @MnO2) was firstly synthesized via a hydrothermal method. CeO2@MnO2 was firstly exploited to construct electrochemical assays for detecting H2O2 and prostate-specific antigen (PSA) with square wave voltammetry (SWV), respectively. The electrochemical results proved that CeO2@MnO2 owned better electrocatalysis towards H2O2 reduction than pure MnO2 NS and CeO2 NP due to the synergistic effect between MnO2 NS and CeO2 NP. Under optimized conditions, CeO2@MnO2 based assay relative to the H2O2 system can be applied to detect H2O2 with range from 1 to 3.0 × 103 µmol L-1. The label-free electrochemical immunoassay based on CeO2@MnO2 relative to the H2O2 system displayed linearly with concentrations of PSA from 0.005 to 50.0 ng mL-1. The electrochemical assays also possessed acceptable sensitivity, selectivity and stability. The study showed that CeO2@MnO2 hold great potential for biosensing platform and the clinic determination of tumor markers in human serum.

Kandelia candel Thioredoxin f Confers Osmotic Stress Tolerance in Transgenic Tobacco.

Water deficit caused by osmotic stress and drought limits crop yield and tree growth worldwide. Screening and identifying candidate genes from stress-resistant species are a genetic engineering strategy to increase drought resistance. In this study, an increased concentration of mannitol resulted in elevated expression of thioredoxin f (KcTrxf) in the nonsecretor mangrove species Kandelia candel. By means of amino acid sequence and phylogenetic analysis, the mangrove Trx was classified as an f-type thioredoxin. Subcellular localization showed that KcTrxf localizes to chloroplasts. Enzymatic activity characterization revealed that KcTrxf recombinant protein possesses the disulfide reductase function. KcTrxf overexpression contributes to osmotic and drought tolerance in tobacco in terms of fresh weight, root length, malondialdehyde (MDA) content, and hydrogen peroxide (H2O2) production. KcTrxf was shown to reduce the stomatal aperture by enhancing K+ efflux in guard cells, which increased the water-retaining capacity in leaves under drought conditions. Notably, the abscisic acid (ABA) sensitivity was increased in KcTrxf-transgenic tobacco, which benefits plants exposed to drought by reducing water loss by promoting stomatal closure. KcTrxf-transgenic plants limited drought-induced H2O2 in leaves, which could reduce lipid peroxidation and retain the membrane integrity. Additionally, glutathione (GSH) contributing to reactive oxygen species (ROS) scavenging and transgenic plants are more efficient at regenerating GSH from oxidized glutathione (GSSG) under conditions of drought stress. Notably, KcTrxf-transgenic plants had increased glucose and fructose contents under drought stress conditions, presumably resulting from KcTrxf-promoted starch degradation under water stress. We conclude that KcTrxf contributes to drought tolerance by increasing the water status, by enhancing osmotic adjustment, and by maintaining ROS homeostasis in transgene plants.

A nanocomposite prepared from bifunctionalized ionic liquid, chitosan, graphene oxide and magnetic nanoparticles for aptamer-based assay of tetracycline by chemiluminescence.

A nanocomposite was prepared from a bifunctionalized ionic liquid, chitosan on magnetic nanoparticle-modified graphene oxide (IL/Chit@MGO). It was used in a chemiluminescencc (CL) assay for tetracycline. The materials were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray powder diffraction, nitrogen adsorption-desorption isotherm, vibrating sample magnetometry and zeta potentials. Subsequently, a tetracycline-binding aptamer (TC-Apt) acting as a recognition element, and G-quadruplex DNAzyme (G-DNAzyme) acting as a signal amplification component were modified on IL/Chit@MGO. So, the bifunctional G-DNAzyme/TC-Apt/IL/Chit@MGO was prepared. The IL/Chit@MGO is found to possess excellent loading capability for TC-Apt. This is attributed to the large specific surface and abundant charge on the surface of IL/Chit@MGO. The composite was used to construct a CL assay for tetracycline. Tetracycline binds to TC-Apt and causes the release of the G-DNAzyme. The latter catalyzes the CL of luminol-H2O2 CL system at pH 7.4. Under optimized conditions, the blue CL at the emission wavelength of 425 nm increases linearly in the 0.16 pM to 2.0 nM concentration range, and the detection limit is 21 fM (at 3σ). The assay is selective, reproducible and stable. The assay was applied to tetracycline detection in practical samples. The apparent recoveries are 98.0% to 101.3% for the milk sample and 97.0% to 102.2% for the water sample. Graphical abstractG-quadruplex DNAzyme (G-DNAzyme) and tetracycline aptamer (TC-Apt) bifunctionalized ionic liquid/chitosan@magnetic graphene oxide (IL/Chit@MGO) was prepared. The nanocomposite was used to construct a chemiluminescence (CL) assay for tetracycline.

Populus euphratica APYRASE2 Enhances Cold Tolerance by Modulating Vesicular Trafficking and Extracellular ATP in Arabidopsis Plants.

Apyrase and extracellular ATP play crucial roles in mediating plant growth and defense responses. In the cold-tolerant poplar, Populus euphratica, low temperatures up-regulate APYRASE2 (PeAPY2) expression in callus cells. We investigated the biochemical characteristics of PeAPY2 and its role in cold tolerance. We found that PeAPY2 predominantly localized to the plasma membrane, but punctate signals also appeared in the endoplasmic reticulum and Golgi apparatus. PeAPY2 exhibited broad substrate specificity, but it most efficiently hydrolyzed purine nucleotides, particularly ATP. PeAPY2 preferred Mg(2+) as a cofactor, and it was insensitive to various, specific ATPase inhibitors. When PeAPY2 was ectopically expressed in Arabidopsis (Arabidopsis thaliana), cold tolerance was enhanced, based on root growth measurements and survival rates. Moreover, under cold stress, PeAPY2-transgenic plants maintained plasma membrane integrity and showed reduced cold-elicited electrolyte leakage compared with wild-type plants. These responses probably resulted from efficient plasma membrane repair via vesicular trafficking. Indeed, transgenic plants showed accelerated endocytosis and exocytosis during cold stress and recovery. We found that low doses of extracellular ATP accelerated vesicular trafficking, but high extracellular ATP inhibited trafficking and reduced cell viability. Cold stress caused significant increases in root medium extracellular ATP. However, under these conditions, PeAPY2-transgenic lines showed greater control of extracellular ATP levels than wild-type plants. We conclude that Arabidopsis plants that overexpressed PeAPY2 could increase membrane repair by accelerating vesicular trafficking and hydrolyzing extracellular ATP to avoid excessive, cold-elicited ATP accumulation in the root medium and, thus, reduced ATP-induced inhibition of vesicular trafficking.

Ultra-sensitive film sensor based on Al2O3-Au nanoparticles supported on PDDA-functionalized graphene for the determination of acetaminophen.

An electrochemical sensor of acetaminophen based on poly(diallyldimethylammonium chloride) (PDDA)-functionalized reduced graphene-loaded Al2O3-Au nanoparticles coated onto glassy carbon electrode (Al2O3-Au/PDDA/reduced graphene oxide (rGO)/glass carbon electrode (GCE)) were prepared by layer self-assembly technique. The as-prepared electrode-modified materials were characterized by scanning electron microscopy, X-ray powder diffraction, and Fourier transform infrared spectroscopy. The electrocatalytic performances of Al2O3-Au/PDDA/rGO-modified glassy carbon electrode toward the acetaminophen were investigated by cyclic voltammetry and differential pulse voltammetry. The modified electrodes of graphene oxide (GO)/GCE, PDDA/rGO/GCE, and Al2O3-Au/PDDA/rGO/GCE were constructed for comparison and learning the catalytic mechanism. The research showed Al2O3-Au/PDDA/rGO/GCE having good electrochemical performance, attributing to the synergetic effect that comes from the special nanocomposite structure and physicochemical properties of Al2O3-Au nanoparticles and graphene. A low detection limit of 6 nM (S/N = 3) and a wide linear detection range from 0.02 to 200 µM (R (2) = 0.9970) was obtained. The preparation of sensor was successfully applied for the detection of acetaminophen in commercial pharmaceutical pills. Graphical abstract Schematic diagram of synthesis of Al2O3-Au/PDDA/rGO/GCE.

How to improve the equity of health financial sources? - Simulation and analysis of total health expenditure of one Chinese province on system dynamics.

INTRODUCTION: We simulate and analyze Total Health Expenditure (THE) in financial sources and other economic indicators (such as THE per capita, GDP, etc.) in a province of China from 2002 to 2012 on System Dynamics. METHODS: Based on actual data and certain mathematical methods, we use system dynamic software to construct a logic model for THE and changing proportions, and thus simulate the actual conditions of development and changes in THE. RESULTS: According to the simulation results, the government possess the largest investment in the average annual growth rate of THE, which was 25.16% in 2012. Social investment comprises the majority of the possession ratio, which was up to 41.20%. CONCLUSIONS: The personal investment growth rate decreased by almost 21%, but the total amount of personal investment increased by 28075 million yuan, which is far higher than the increase in government investment. Individuals are still the main carriers of health care expenses. The equity of health financial sources is still poor. The System Dynamics method used in this paper identifies a dynamic measurement process, provides a scientific basis for simulation and analysis of the changes in THE and its key constraining factors, as well as put forward suggestions for the improvement of equity of health financial sources.

A novel flower-shaped Ag@ZIF-67 chemiluminescence sensor for sensitive detection of CEA.

In this work, a chemiluminescence (CL) aptasensor for sensitive carcinoembryonic antigen (CEA) detection was constructed based on the CL system of luminol-H2O2-NaOH. Magnetic carbon nanotubes (MCNTs), as the base material, was modified with CEA-aptamer and DNA1, and was combined with the novel flower-shaped Ag@ZIF-67 of modified with DNA2 through the principle of base complementary pairing. CEA combined with aptamer when it existed in the solution. At the same time, MCNTs was adsorbed at the bottom of the container under the influence of external magnetic field, and Ag@ZIF-67 enhanced the CL signal. The CL aptasensor demonstrated high selectivity and sensitivity for CEA in human serum sample with (1-4): a detection limit of 4.53 × 10-3 ng/mL in case the detection range was 0.05-500 ng/mL. Furthermore, the proposed method had been shown great potential in cancer diagnosis.

Chemiluminescence sensing of adenosine using DNA cross-linked hydrogel-capped magnetic mesoporous silica nanoparticles.

At present, a host of high-sensitivity and selective tumor marker detection methods play a central role in various research fields and assay platforms. Here, a method for DNA cross-linked hydrogel-capped magnetic core-shell structure mesoporous silica nanoparticles (Fe3O4@nSiO2@mSiO2) based on target stimulus was proposed. Specifically, Fe3O4@nSiO2@mSiO2 nanoparticles with nucleic acid promoter units were prepared. The promoter induces the predesigned modified polyacrylamide DNA strand to carry out hybridization chain reaction on the surface of Fe3O4@nSiO2@mSiO2 nanoparticles, forming a hydrogel coating on the surface of Fe3O4@nSiO2@mSiO2 nanoparticles. Under the stimulation of adenosine, Fe3O4@nSiO2@mSiO2 released the signal molecule luminol. Simultaneously, the MIL-101（Fe）material, a signal amplification molecule, was released from the DNA hydrogel. Compared with the traditional gated mesoporous silica system, the DNA hydrogel-coated Fe3O4@nSiO2@mSiO2 is not easy to leak and has a higher loading capacity. In addition, the optical background of DNA hydrogels is low, combined with MOFs materials, even about 1.4 × 10-10 M adenosine can be detected in this biosensor. Based on the combination of DNA hydrogels, MOFs conjugates and gating systems, the construction of biosensors will be more eye-catching, which will expand new ideas for biosensor platform manufacturing.

Novel Chemiluminescence Sensor for Thrombin Detection Based on Dual-Aptamer Biorecognition and Mesoporous Silica Encapsulated with Iron Porphyrin.

Thrombin is a marker of blood-related diseases, and its detection is of great significance in the fields of medical and biological research. Herein, a novel chemiluminescence (CL) sensor for thrombin detection was prepared based on dual-aptamer biorecognition and mesoporous silica encapsulated with iron porphyrin. Mesoporous silica encapsulated with hematin by aptamer1 (Apt1/hematin/M-SiO2) and magnetic microspheres modified with aptamer2 (Apt2/NH2-MS) were successfully prepared, and the two materials were used to construct a CL sensor to detect thrombin. Primarily, Apt2/NH2-MS is used for pretreatment separation of thrombin samples by the biorecognition effect between the aptamer (Apt2) and target (thrombin). Then, thrombin/Apt2/NH2-MS is again recognized with Apt1 on the surface of Apt1/hematin/M-SiO2 and Apt1/thrombin/Apt2/NH2-MS is formed, so dual-aptamer biorecognition is realized. Meanwhile, the generated Apt1/thrombin/Apt2/NH2-MS makes Apt1 shed off the surface of M-SiO2 and release hematin. The released hematin can catalyze the luminol-H2O2 CL reaction. Therefore, a sandwich-type CL sensor was constructed based on dual-aptamer biorecognition and hematin catalysis for the detection of thrombin. The sensor has a linear range of 7.5 × 10-15 to 2.5 × 10-10 mol·L-1 and a detection limit of 2.2 × 10-15 mol·L-1 and also exhibits excellent selectivity, reproducibility, and stability. The sensor was successfully used for the detection of thrombin in serum samples, which makes it possible to apply the sensor in the detection of thrombin in actual samples.

A "signal-on" chemiluminescence biosensor for thrombin detection based on DNA functionalized magnetic sodium alginate hydrogel and metalloporphyrinic metal-organic framework nanosheets.

A "signal-on" chemiluminescence biosensor was established for detecting thrombin. The thrombin aptamer1-functionalized magnetic sodium alginate (Malg-Apt1) hydrogel was synthesized by physical interaction between sodium alginate and Ca2+, and it was used in the biosensor for separating and enriching thrombin. Ethylenediamine tetraacetic acid (EDTA) was used to chelate with Ca2+ to dissolve the hydrogel and release thrombin. A metalloporphyrinic metal-organic framework nanosheet, named as Cu-TCPP(Co) MOFs, was prepared as signal amplification strategy. Cu-TCPP(Co) MOFs/Au-ssDNA (ssDNA: single-strand DNA) was synthesized for controllable further amplification of chemiluminescent signal. The thrombin aptamer2-functionalized magnetic carbon nanotubes (MCNTs-Apt2) were used as a matrix, and Cu-TCPP(Co) MOFs/Au-ssDNA was adsorbed on the MCNTs by the complementary pairing of the partial bases between ssDNA and Apt2. Compared with ssDNA, Apt2 has a stronger interaction with thrombin. Therefore, thrombin can trigger the release of Cu-TCPP(Co) MOFs/Au-ssDNA to achieve signal amplification. Under the optimal conditions, the biosensor could detect thrombin as low as 2.178 × 10-13 mol/L with the range from 8.934 × 10-13 to 5.956 × 10-10 mol/L and exhibited excellent selectively. Moreover, the "signal-on" chemiluminescence biosensor showed potential application for the detection of thrombin in body fluids.

Rapid fabrication of electrode for the detection of alpha fetoprotein based on MnO2 functionalized mesoporous carbon hollow sphere.

The concentration of alpha-fetoprotein (AFP) rises greatly in patients with liver cancer and it is a challenge to construct a sensitive AFP detection method with wide range. Therefore, an easy and label-free sensing electrochemical platform for AFP detection with wide concentration range had been designed in this work. Firstly, MnO2 functionalized mesoporous carbon hollow sphere (MCHS@MnO2) with optimal performance was synthesized by regulating experimental conditions and characterized by scanning electron microscope (SEM), high resolution transmission electron microscopy (HRTEM), x-ray diffraction (XRD), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV), etc. Then, it was immobilized on glassy carbon electrode (MCHS@MnO2/GCE) to build an immunosensor for the detection of AFP. The MCHS@MnO2/GCE can catalyze decomposition of H2O2 to generate electrochemical signal, and the signal will decrease after capturing AFP. Due to good electrocatalytic activity of MCHS@MnO2 to H2O2, the immunosensor achieved indirect detection of AFP with wide sensing range from 0.10 ng mL-1 to 420 ng mL-1 and a detection limit of 0.03 ng mL-1. Furthermore, the method had been proven to be satisfactory selectivity and reproducibility, and it was successfully applied to determine the content of AFP in human serum samples with satisfactory results. This method is expected to be used for early diagnosis and prognosis examination of liver cancer patients.

A chemiluminescence biosensor for lysozyme detection based on aptamers and hemin/G-quadruplex DNAzyme modified sandwich-rod carbon fiber composite.

In our work, aptamers and hemin/G-quadruplex DNAzyme modified sandwich-rod graphene quantum dots @ graphene oxide @ carbon fiber composite (DNAzyme/L-Apt/GQDs@GO@CF) was successfully prepared for sensitive and selective chemiluminescence (CL) detection of lysozyme (LZM). Initially, GQDs@GO@CF was successfully prepared and characterized. Lysozyme aptamers (L-Apt) as a recognition element and hemin/G-quadruplex DNAzyme (DNAzyme) as a catalyst of luminal - H2O2 were modified on the surface of GQDs@GO@CF, sequentially. The immobilization properties of GQDs@GO@CF to L-Apt and the adsorption properties of L-Apt/GQDs@GO@CF to DNAzyme were also researched, respectively. Then, the modified sandwich-rod carbon fiber composite was applied to the construction of CL biosensor for LZM detection. When LZM existed, DNAzyme would be released from the surface of L-Apt/GQDs@GO@CF and catalyzed the reaction of luminal - H2O2. Under optimized conditions, the CL biosensor for LZM detection showed wide linear range of 2.64 × 10-10 to 6.6 × 10-8 g/L and low detection limit of 1.25 × 10-11 g/L (3δ). Finally, the CL biosensor was successfully used for LZM detection in human urine samples and illustrated the potential application in pratical samples.

A highly selective and sensitive detection of insulin with chemiluminescence biosensor based on aptamer and oligonucleotide-AuNPs functionalized nanosilica @ graphene oxide aerogel.

A novel, highly selective and sensitive chemiluminescence (CL) biosensor for insulin (INS) detection was proposed based on aptamer and oligonucleotide-gold nanoparticles functionalized nanosilica @ graphene oxide aerogel. Initially, nanosilica functionalized graphene oxide aerogel (SiO2@GOAG) was successfully prepared and the composite showed rich pore distribution, large specific surface area and good biocompatibility. Insulin aptamer (IGA3) was used as a biorecognition element and oligonucleotide functionalized gold nanoparticles (ssDNA-AuNPs) was used as CL signal amplification materials, which were functionalized on the surface of SiO2@GOAG. The multi-functionalized composite - ssDNA-AuNPs/IGA3/SiO2@ GOAG was obtained and used to construct the CL biosensor for insulin detection. When insulin is present in a sample, the insulin will bind to the IGA3, which will result in the release of ssDNA-AuNPs. The released ssDNA-AuNPs would catalyze the luminescence of luminol and H2O2. The linear range of the CL biosensor for insulin detection was 7.5 × 10-12 to 5.0 × 10-9 moL/L and the detection limit was 1.6 × 10-12 moL/L (S/N = 3). The selectivity and stability of the CL biosensor were also studied and the results showed that the biosensor exhibited high selectivity and good stability due to the introduction of ssDNA-AuNPs/IGA3/SiO2@GOAG. The CL biosensor was finally used for recombinant human insulin detection in recombinant human insulin injection and the results were satisfactory.

Highly selective adsorption of hydroquinone by hydroxyethyl cellulose functionalized with magnetic/ionic liquid.

Magnetic hydroxyethyl cellulose/ionic liquid (MHEC/IL) materials were fabricated through a facile and fast process and their application as excellent adsorbents for hydroquinone was also demonstrated. The thermal stability, chemical structure and magnetic property of the MHEC/IL were characterized by the Scanning electron microscope (SEM), Transmission Electron Microscope (TEM), Fourier transform infrared spectrometer (FT-IR) and X-ray diffraction (XRD), respectively. The adsorbents were used for the removal of hydroquinone from simulated wastewater with a fast solid-liquid separation in the presence of external magnetic field. The influence of various analytical parameters on the adsorption of hydroquinone such as pH, contact time and initial ion concentration were studied in detail. The results showed that the maximum adsorption capacity was 335.68mgg-1, observed at pH 5 and temperature 30°C. Equilibrium adsorption was achieved within 30min. The kinetic data, obtained at the optimum pH 5, could be fitted with a pseudo-second order equation. Adsorption process could be well described by Freundlich adsorption isotherms. The obtained results indicated that the impregnation of the room temperature IL significantly enhances the removal efficiency of hydroquinone. The MHEC/IL may be suitable materials in phenols pollution cleanup if they are synthesized in largescale and at low price in near future.

A chemiluminescence aptasensor for thrombin detection based on aptamer-conjugated and hemin/G-quadruplex DNAzyme signal-amplified carbon fiber composite.

In this work, a highly sensitive and selective chemiluminescence (CL) aptasensor was prepared for thrombin (THR) detection based on aptamer-conjugated and hemin/G-quadruplex DNAzyme signal-amplified carbon fiber composite (HG-DNAzyme/T-Apt/SiO2@GO@CF). Initially, SiO2@GO@CF was successfully prepared and characterized by Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FT-IR). Thrombin aptamer (T-Apt) as an identification element and simulated enzyme - hemin/G-quadruplex DNAzyme (HG-DNAzyme) as a signal-amplified material, were applied in the CL aptasensor. Then, the immobilization properties of SiO2@GO@CF and adsorption properties of T-Apt/SiO2@GO@CF were studied. Lastly, HG-DNAzyme/T-Apt/SiO2@GO@CF was applied in construction of the CL aptasensor. When THR existed, HG-DNAzyme was desorbed from the surface of T-Apt/SiO2@GO@CF and catalyzed the CL system of luminol-H2O2. Under optimized CL conditions, THR was measured with the linear concentration range of 1.5 × 10-14 to 2.5 × 10-11 moL/L and the detection limit of 6.3 × 10-15 moL/L (3δ). The proposed CL aptasensor was used to the determination of THR in human serum samples and recoveries ranged from 99.0% to 102.4%. Those satisfactory results illustrated the CL aptasensor could achieve highly sensitive and selective detection of THR and revealed potential application in practical samples.

A turn-on chemiluminescence biosensor for selective and sensitive detection of adenosine based on HKUST-1 and QDs-luminol-aptamer conjugates.

In this work, HKUST-1 and QDs-luminol-aptamer conjugates were prepared. The QDs-luminol-aptamer conjugates can be adsorbed by graphene oxide through π-π conjugation. When the adenosine was added, the QDs-luminol-aptamer conjugates were released from magnetic graphene oxide (MGO), the chemiluminescent switch was turned on. It was reported that HKUST-1 can catalyze the chemiluminescence reaction of luminol-H2O2 system in an alkaline medium, and improve the chemiluminescence resonance energy transfer (CRET) between chemiluminescence and QDs indirectly. Thus, the adenosine can be detected sensitively. Based on this phenomenon, the excellent platform for detection of adenosine was established. Under the optimized conditions, the linear detection range for adenosine was 1.0 × 10-12-2.2 × 10-10 mol/L with a detection limit of 2.1 × 10-13 mol/L. The proposed method was successfully used for adenosine detection in biological samples.