One-Pot Synthesis of Nanoflower-Like Zn2SnS4 as Nanozymes for Highly Sensitive Electrochemical Detection of H2O2 Released by Living Cells.

The sensitive and reliable nanozyme-based sensor enables the detection of low concentrations of H2O2 in biological microenvironments, it has potential applications as an in-situ monitoring platform for cellular H2O2 release. The uniformly dispersed bimetallic sulfide (Zn2SnS4) nanoflowers were synthesized via a one-pot hydrothermal method and the two kinds of metal ions can serve as morphology and structure directing agents for each other in the synthetic process. The nanoparticles were utilized as nanozyme materials to fabricate a novel electrochemical sensor, and it exhibits a distinct electrochemical response towards H2O2 with excellent stability and detection capability (with a minimum detection limit of 1.79 nM (S/N=3)), the excellent characteristics facilitate the precise detection of low concentrations of H2O2 in biological microenvironments. Use the macrophages differentiated from leukemia THP-1 cells as a representative sensing model, the sensor was successfully utilized for real-time monitoring of the release of H2O2 induced by living cells, which has significant potential applications in clinical diagnosis and cancer treatment.

Multiple NTS neuron populations cumulatively suppress food intake.

Several discrete groups of feeding-regulated neurons in the nucleus of the solitary tract (nucleus tractus solitarius; NTS) suppress food intake, including avoidance-promoting neurons that express Cck (NTSCck cells) and distinct Lepr- and Calcr-expressing neurons (NTSLepr and NTSCalcr cells, respectively) that suppress food intake without promoting avoidance. To test potential synergies among these cell groups, we manipulated multiple NTS cell populations simultaneously. We found that activating multiple sets of NTS neurons (e.g. NTSLepr plus NTSCalcr [NTSLC], or NTSLC plus NTSCck [NTSLCK]) suppressed feeding more robustly than activating single populations. While activating groups of cells that include NTSCck neurons promoted conditioned taste avoidance (CTA), NTSLC activation produced no CTA despite abrogating feeding. Thus, the ability to promote CTA formation represents a dominant effect but activating multiple non-aversive populations augments the suppression of food intake without provoking avoidance. Furthermore, silencing multiple NTS neuron groups augmented food intake and body weight to a greater extent than silencing single populations, consistent with the notion that each of these NTS neuron populations plays crucial and cumulative roles in the control of energy balance. We found that silencing NTSLCK neurons failed to blunt the weight-loss response to vertical sleeve gastrectomy (VSG) and that feeding activated many non-NTSLCK neurons, however, suggesting that as-yet undefined NTS cell types must make additional contributions to the restraint of feeding.

Measurement of the [Formula: see text]Ta([Formula: see text]) cross sections up to stellar s-process temperatures at the CSNS Back-n.

The neutron capture cross section of [Formula: see text]Ta is relevant to s-process of nuclear astrophysics, extraterrestrial samples analysis in planetary geology and new generation nuclear energy system design. The [Formula: see text]Ta([Formula: see text]) cross section had been measured between 1 eV and 800 keV at the back-streaming white neutron facility (Back-n) of China spallation neutron source(CSNS) using the time-of-flight (TOF) technique and [Formula: see text] liquid scintillator detectors. The experimental results are compared with the data of several evaluated libraries and previous experiments in the resolved and unresolved resonance region. Resonance parameters are extracted using the R-Matrix code SAMMY in the 1-700 eV region. The astrophysical Maxwell average cross section(MACS) from kT = 5 to 100 keV is calculated over a sufficiently wide range of neutron energies. For the characteristic thermal energy of an astrophysical site, at kT = 30keV the MACS value of [Formula: see text]Ta is 834 ± 75 mb, which shows an obvious discrepancy with the Karlsruhe Astrophysical Database of Nucleosynthesis in Stars (KADoNiS) recommended value 766 ± 15 mb. The new measurements strongly constrain the MACS of [Formula: see text]Ta([Formula: see text]) reaction in the stellar s-process temperatures.

An Image-Based Quantized Compressive Sensing Scheme Using Zadoff-Chu Measurement Matrix.

In this paper, a complex-valued Zadoff-Chu measurement matrix is proposed and used in an image-based quantized compressive sensing (CS) scheme. The results of theoretical analysis and simulations show that the reconstruction performance generated by the proposed Zadoff-Chu measurement matrix is better than that obtained by commonly used real-valued measurement matrices. We also applied block compressive sensing (BCS) to reduce the computational complexity of CS and analyzed the effect of block size on the reconstruction performance of the method. The results of simulations revealed that an appropriate choice of block size can not only reduce the computational complexity but also improve the accuracy of reconstruction. Moreover, we studied the effect of quantization on the reconstruction performance of image-based BCS through simulations, and the results showed that analog-to-digital converters with medium resolutions are sufficient to implement quantization and achieve comparable reconstruction performance to that obtained at high resolutions, based on which an image-based BCS framework with low power consumption can thus be developed.

Application of Nursing Outcome-Oriented Integrated Zero-Defect Nursing Combined with Respiratory Function Training in Long-Term Bedridden Patients Undergoing Stroke.

Objective: To explore the application effect of nursing outcome-oriented integrated zero-defect nursing combined with respiratory function training in long-term bedridden patients with stroke. Methods: A total of 120 long-term bedridden patients with stroke were randomly divided into three groups: groups A, B, and C. Group A was given nursing outcome-oriented integrated zero-defect nursing combined with respiratory function training, group B was given nursing outcome-oriented integrated zero-defect nursing, and group C was given routine nursing. Rosenbek aspiration degree classification criteria were used to evaluate the incidence of aspiration; blood oxygen saturation, arterial oxygen partial pressure, and respiratory pressure were compared before and after the intervention. The swallowing function was evaluated by a water swallowing test (WST). The quality of life was assessed using the Generic Quality of Life Inventory-74 (GQOLI-74). Results: After treatment, the Rosenbek aspiration degree of groups A and B were better than those of group C (P < 0.05); the improvement degree of respiratory function indexes in group A was better than those in B and C, and the blood oxygen saturation and arterial blood oxygen partial pressure in group B were better than those in C (P < 0.05). The incidence of complications in groups A and B was lower than that in C, and complications in group A were lower than that in B (P < 0.05). After treatment, the scores of psychological function, social function, and material life status of the three groups were increased, and each score of groups A and B was higher than that of C, and each score of group A was higher than that of B (P < 0.05). Conclusion: Nursing outcome-oriented integrated zero-defect nursing combined with respiratory function training can effectively improve aspiration, respiratory function, swallowing function, complication rate, and quality of life in long-term bedridden patients with stroke.

Facile Fabrication of Graphene Oxide Nanoribbon-Based Nanocomposite Papers with Different Oxidation Degrees and Morphologies for Tunable Fire-Warning Response.

Smart fire-warning sensors based on graphene oxide (GO) nanomaterials, via monitoring their temperature-responsive resistance transition, have attracted considerable interest for several years. However, an important question remains as to whether or not different oxidation degrees of the GO network can produce different impacts on fire-warning responses. In this study, we synthesized three types of GO nanoribbons (GONRs) with different oxidation degrees and morphologies, and thus prepared flame retardant polyethylene glycol (PEG)/GONR/montmorillonite (MMT) nanocomposite papers via a facile, solvent free, and low-temperature evaporation-induced assembly approach. The results showed that the presence of the GONRs in the PEG/MMT promoted the formation of an interconnected nacre-like layered structure, and that appropriate oxidation of the GONRs provided better reinforcing efficiency and lower creep deformation. Furthermore, the different oxidation degrees of the GONRs produced a tunable flame-detection response, and an ideal fire-warning signal in pre-combustion (e.g., 3, 18, and 33 s at 300 °C for the three PEG/GONR/MMT nanocomposite papers), superior to the previous GONR-based fire-warning materials. Clearly, this work provides a novel strategy for the design and development of smart fire-warning sensors.

Broadband Circular Polarizer Based on Chirped Double-Helix Chiral Fiber Grating.

We propose an all-fiber broadband circular polarizer based on leaky mode coupling and a phase-matched turning point (PMTP) in a chirped, double-helix, chiral, long-period, fiber grating (CLPG). The CLPG was coated with a material in which the refractive index was higher than that of the fiber cladding, enabling the coupling of the core mode to leaky modes to achieve a desired extinction ratio. The complex coupled-mode theory was employed to investigate the coupling mechanism and conditions under which the desired coupling efficiency could be achieved. Moreover, the PMTP in phase-matched curves, which resolved the conflict between the operating bandwidth and the grating pitch range of the CLPG and made a large bandwidth with a small grating pitch possible, was used in the design to achieve a compact structure. Finally, two broadband circular polarizers with an extinction ratio above 25 dB were simulated; one had a bandwidth of over 120 nm and a length of 3.5 cm, and the other had a bandwidth of over 300 nm and a length of 8 cm.

Solvent-Free Hydrogenation of 5-Hydroxymethylfurfural and Furfural to Furanyl Alcohols and their Self-Condensation Polymers.

2,5-Bis(hydroxymethyl)furan (BHMF) as well as furfuryl alcohol (FFA) are considered as highly valuable biomass-derived alcohols resembling aromatic monomers in polymer synthesis. Herein, a series of cobaltic nitrogen-doped carbon (Co-NC) catalysts calcinated at different temperatures were synthesized and tested for the solvent-free hydrogenation of 5-hydroxymethylfurfural (HMF) to prepare BHMF. It was found that the Co-NC catalyst calcinated at 600 °C (Co-NC-600) exhibited a superior catalytic activity in the hydrogenation reaction mainly due to the doping of graphitic N, which probably facilitated the polarization of H2 to afford H+ and H- . Consequently, Co-NC-600 offered a high BHMF/FFA yield greater than 90 % with a nearly complete conversion of HMF/furfural (FF) at the optimal conditions (80 °C, 4 h, and 5 MPa H2 ). After the hydrogenation reaction, Co-NC catalyst was facilely recycled by magnetic separation, and the obtained BHMF/FFA was then successfully transformed into hypercrosslinked polymers with an excellent CO2 /H2 storage capacity comparable to aromatic hydroxymethyl polymers. Therefore, this is a novel and facile two-step pathway for the conversion of biomass-derived HMF/FF towards functional polymers from both industrial and environmental perspectives.

The clinicopathological and prognostic significance of mTOR and p-mTOR expression in patients with non-small cell lung cancer: A meta-analysis.

BACKGROUND: The mammalian target of rapamycin (mTOR) has a crucial role in carcinogenesis, angiogenesis, cellular proliferation, and metastasis; however, its significance in non-small cell lung cancer (NSCLC) remains contentious. Consequently, this study aims to assess the clinicopathological and prognostic importance of mTOR/p-mTOR expression in NSCLC. METHODS: Literature retrieval was undertaken by searching English databases PubMed, EMBASE, Web of Science, and Cochrane Library as well as Chinese databases CNKI, Wan Fang, and VIP for full-text publications that satisfied our eligibility criteria up to November 2021. STATA 12.0 was used to conduct statistical analysis (STATA Corporation, College Station, TX). RESULTS: This meta-analysis includes a total of 4683 patients from 28 primary publications. mTOR/p-mTOR expression was associated with sex (OR = 0.608, 95% CI: 0.442-0.836), lymph node metastasis (OR = 2.084, 95% CI: 1.437-3.182), and CEA (OR = 1.584, 95% CI: 1.135-2.209), but not with age, histological type, depth of tumor invasion, distant metastasis, TNM stage, differentiation degree, tumor size, or smoking. In addition, the expression of mTOR/p-mTOR is related to shorter overall survival in NSCLC patients (HR = 1.415, 95% CI: 1.051-1.905). CONCLUSION: Positive mTOR/p-mTOR expression was substantially correlated with unfavorable conditions on the sex, lymph node metastases, and CEA levels. mTOR/p-mTOR may indicate a bad prognosis for NSCLC. The current findings must be confirmed and changed by other high-quality research employing a multivariate analysis on bigger sample size.

Production of high-energy neutrons by interaction of a deuteron beam with matter.

Experimental double differential cross section data for neutrons in the high-energy region are still scarce because of the difficulty of producing high-energy neutrons. The present work studies the possibility of producing high-energy neutrons by interaction of a deuteron beam with matter. The Geant4 toolkit is used to simulate the interaction between a deuteron beam and matter. An analytical method is also developed to calculate the neutron yields produced in the interaction of the deuteron beam with matter. The input cross section data are not only taken from the TEDNL-2017 library but are also calculated by the isospin-dependent quantum molecular dynamics model. It is shown that it is possible to produce high-energy neutrons by interaction of a deuteron beam with matter. If one wishes to produce high-energy neutrons, a low-Z target and a small emission angle may be considered. A thin target is a good choice if one wishes to produce neutrons with a smaller energy peak width.

The Immune Regulatory Effect of Boron on Ostrich Chick Splenic Lymphocytes.

Boron is a trace element which plays important roles in immune response. The relationship between boron and splenic lymphocyte proliferation, apoptosis, secretion of cytokines, and genes potentially related to immune response in ostrich chicks were investigated in the present study. Different concentrations of boron (0, 0.01, 0.1, 0.5, 1, 5, 10, 25, 50, and 100 mmol/L) were applied to splenic lymphocytes of African ostrich, respectively. The effect of boron on lymphocyte proliferation was checked by the CCK-8 method. Flow cytometry was used to detect the effect of boron on apoptosis. The secretion levels of IL-6 and IFN-α were determined by ELISA. Splenic lymphocyte gene expression profiles of ostrich chicks treated with boron (0, 0.1, 100 mmol/L) were studied using RNA-seq technology. The results showed that cell proliferation increased with 0.01-10 mmol/L boron, when it was 25-100 mmol/L, the cell proliferation gradually decreased as the boron concentration increased. Apoptosis ratio in ostrich splenic lymphocytes was closely related to boron concentrations. 0.01- and 0.1-mmol/L boron inhibited apoptosis in splenic lymphocytes, whereas 1, 10, 50, and 100-mmol/L boron promoted apoptosis. As the concentration of boron increased, the secretion of IL-6 gradually decreased; IFN-α was initially increased and then decreased with boron concentrations increased, reaching the maximum level with 1 mmol/L boron. In terms of the RNA-Seq data, there was no differentially expressed gene between the 0- and 0.1-mmol/L boron-treated samples; 21 differentially expressed genes were found between the 0- and 100-mmol/L boron-treated samples; 43 differentially expressed genes were found between the 0.1- and 100-mmol/L boron-treated samples. Functional analysis of the differentially expressed genes by Gene Ontology verified multiple functions associated with immune response. Pathway analysis showed that systemic lupus erythematosus, alcoholism, viral carcinogenesis, and necroptosis pathway were the major enriched pathways, and BIRC2-3, FTH1, and IL-1ß genes showed differential expression in necroptosis pathway. These results demonstrated that low concentrations (0.01-0.1 mmol/L) of boron may promote the proliferation and the secretion of cytokines, inhibit cell apoptosis of ostrich splenic lymphocytes by enhancing the function of the cell membrane and the activity of intracellular catalytic enzymes, whereas high-concentration (25-100 mmol/L) boron had opposite effects on cells. The necroptosis pathway might play a pivotal role in regulating the immune response of boron-treated splenic lymphocytes in ostrich chicks.

Boron Supplementation Promotes Osteogenesis of Tibia by Regulating the Bone Morphogenetic Protein-2 Expression in African Ostrich Chicks.

The present study aimed to explore the effects of supplemental boron on osteogenesis of tibia and to investigate the possible relationship between additional boron and the expression of bone morphogenetic protein-2 (BMP-2) in tibia of ostrich chicks. Therefore, forty-eight African ostrich chicks (15 days old) were supplemented with 0 mg/L, 40 mg/L, 80 mg/L, 160 mg/L, 320 mg/L, and 640 mg/L of boron in drinking water for 75 days. The paraffin sections of tibia used to measure histomorphometric parameters by hematoxylin and eosin (HE) staining, Masson's staining, and immunohistochemistry (IHC). Enzyme-linked immunosorbent assay was performed to assess the level of BMP-2, osteocalcin (BGP), glucocorticoids (GCs), osteoprotegerin (OPG), and receptor activator of nuclear factor kappa-B ligand (RANKL) in serum. TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling) technique was performed to detect the cell apoptosis. The results indicated that low dose of supplemental boron (40 mg/L-160 mg/L) in drinking water promotes bone development by increasing the mature ossein. The expression of BMP2 on 45 days was higher than 90 days. Serum level of BMP-2, BGP, and GCs changed significantly in groups with low dosage of boron, and OPG/RANKL ratio was upregulated from 0 to 160 mg/L. Cell apoptosis was least in 40 mg/L and 160 mg/L groups. Taken together, low dose of boron supplemented in drinking water could promote osteogenesis and growth and development of tibia by regulating the expression and secretion of BMP-2 and providing a dynamically balanced environment for tibia growth, development, and reconstruction by regulating the concentrations of BGP, GCs, and OPG/RANKL ratio in serum.

Specific Coordination between Zr-MOF and Phosphate-Terminated DNA Coupled with Strand Displacement for the Construction of Reusable and Ultrasensitive Aptasensor.

Electrochemical aptasensors involved in chemical labeling are often single-use and sensitivity-limited because the probes are commonly single-point labeled and irreversible. In this work, the specific coordination between Zr4+ and phosphate group (-PO43-) was employed to construct a new aptasensor that is highly sensitive and reusable, using Ochratoxin A (OTA) as the test model. The OTA binding aptamer (OBA) was hybridized with the thiolated supporting sequence (TSS) immobilized on the surface of a gold electrode. The UiO-66 with a formula of [Zr6O4(OH)4(BDC)6], one of the class of Zr metal-organic frameworks (MOFs), was then particularly grafted on the terminal of OBA through the specific coordination between Zr4+ and 5'-PO43-, i.e., the Zr-O-P coordination bond. Similarly, as much as the 5'-PO43- and 3'-methylene blue dual-labeled sequences (DLS) were further assembled on UiO-66 due to the large surface area of MOF and rich active sites of Zr4+. Owing to the specific coordination for signal amplification, the developed aptasensor shows greatly enhanced sensitivity. A wide detection range from 0.1 fM to 2.0 µM and an ultralow detection limit of 0.079 fM (S/N = 3) for OTA were obtained. Additionally, the TSS can rehybridize with a new OBA to regenerate the aptasensor but without complicated pretreatments, enabling a aptasensor that is readily reusable for OTA detection. The aptasensor was successfully applied for OTA detection in the red wine samples, demonstrating a promising prospect for food safety monitoring.

MiR-26 regulates ddx3x expression in medaka (Oryzias latipes) gonads.

MicroRNAs (miRNAs) participate in the reproductive process by regulating the expression of target genes, however, there are few studies on the regulation of mRNA target by miRNAs in medaka (Oryzias latipes). Our previous data showed that miR-202-5p has a sex-biased expression and miR-26 is abundantly expressed in both ovary and testis of medaka. In this study, DEAD-box helicase 3, X-linked (ddx3x) was proposed to be a putative target of miR-26 and miR-202-5p through bioinformatic analysis. Here, medaka ddx3x (Olddx3x) was cloned and sequence alignment analysis indicated that Olddx3x is highly conserved and has more than 90% identity with some other teleosts. Reverse transcription polymerase chain reaction (RT-PCR) showed that Olddx3x was highly expressed in testis and ovary. Meanwhile, chromogenic in situ hybridization manifested that Olddx3x was abundantly expressed in the early oocytes in the ovary and in various stages of spermatogenesis, especially the obvious signal in the testis of spermatocytes and sperm. Dual-luciferase reporter assay and the injection of miR-26 agomir and antagomir demonstrated that the expression of Olddx3x was regulated by miR-26 but not miR-202-5p. The overall results revealed that miR-26 may perform a vital role in medaka reproduction development by regulating the expression of ddx3x.

Ultrasensitive impedimetric mercury(II) sensor based on thymine-Hg(II)-thymine interaction and subsequent disintegration of multiple sandwich-structured DNA chains.

An impedimetric method is described for ultrasensitive analysis of mercury(II). It is based on thymine-Hg(II)-thymine interaction which causes the disintegration of multiple-sandwich structured DNA chains. DNA strands were selected that are partially complementary to the T-rich Hg(II)-specific oligonucleotides (MSO). They were immobilized on a gold electrode via Au-S interaction. Next, the MSO and the bridging strands (BS) that can connect adjacent MSOs were alternately attached through layer-by-layer hybridization. Thus, a multiple-sandwich structured interface in created that carries numerous MSOs. This leads to a change-transfer resistance (Rct) values of the electrode-electrolyte interface at faradic electrochemical impedance spectroscopy measurements in the presence of the hexacyanoferrate(II)/(III) redox probe at 0.2 V (vs. Ag/AgCl). If Hg(II) is added to the solution, the MSOs selectively interact with Hg(II) to produce T-Hg(II)-T structures. Hence, the multiple-sandwich hybridization chains become disintegrated, and this causes a decrease in resistivity. The effect can be used to quantify Hg(II) over an analytical range that extends over four orders of magnitude (1 fM to 10 pM), and it has a 0.16 fM limit of detection under optimal conditions. Graphical abstract An electrochemical sensor for femtomolar level detection of Hg2+ is realized on the basis of thymine-Hg2+-thymine interaction which causes disintegration of multiple sandwich DNA hybridization strands.

Local and Global Feature Learning for Blind Quality Evaluation of Screen Content and Natural Scene Images.

The blind quality evaluation of screen content images (SCIs) and natural scene images (NSIs) has become an important, yet very challenging issue. In this paper, we present an effective blind quality evaluation technique for SCIs and NSIs based on a dictionary of learned local and global quality features. First, a local dictionary is constructed using local normalized image patches and conventional -means clustering. With this local dictionary, the learned local quality features can be obtained using a locality-constrained linear coding with max pooling. To extract the learned global quality features, the histogram representations of binary patterns are concatenated to form a global dictionary. The collaborative representation algorithm is used to efficiently code the learned global quality features of the distorted images using this dictionary. Finally, kernel-based support vector regression is used to integrate these features into an overall quality score. Extensive experiments involving the proposed evaluation technique demonstrate that in comparison with most relevant metrics, the proposed blind metric yields significantly higher consistency in line with subjective fidelity ratings.

Identification and expression analysis of microRNAs in medaka gonads.

Gonad development is a highly regulated, coordinated biological process and increasing evidences have indicated that microRNA (miRNA) may be involved in this dynamic program. Medaka (Oryzias latipes) is a good model for reproductive research as it has distinct sex determining genes, however, research in gonadal miRNAs is lacked. In this study, two small RNA libraries from the ovaries and testes were constructed and sequenced. A total of 285 conserved and 388 novel miRNAs were obtained, among which 142 mature miRNAs were significantly (> two-fold change) up or down regulated in the testis compared to the ovary. Quantitative Reverse Transcription-Polymerase Chain Reaction (qRT-PCR) analysis showed that miR-430c, miR-26a and miR-202-5p were expressed in a gonad-specific or sex-biased pattern. Fluorescence in situ hybridization (FISH) indicated that miR-202-5p was present throughout spermatogenesis and was only detected at the early stages of oogenesis, this sex biased expression pattern suggested that miR-202-5p might be a crucial candidate in male differentiation and development. Our study provides the repertoire, a comprehensive annotation of miRNAs from gonads and a reference for functional studies of miRNAs in medaka.

Selective binding of Pb2+ with manganese-terephthalic acid MOF/SWCNTs: Theoretical modeling, experimental study and electroanalytical application.

A nanocomposite of flake-shaped manganese-terephthalic acid MOF/single-walled carbon nanotubes (Mn(TPA)-SWCNTs) was synthesized using manganese chloride, terephthalic acid and SWCNTs as raw materials. Theoretical modeling study shows that the Mn(TPA) component has stronger adsorption ability to lead ion (Pb2+) than the other common heavy metal ions, which is in good agreement with the result of electrochemical assay. Then, the Mn(TPA)-SWCNTs were used as a sensing matrix for the voltammetric determination of Pb2+. The results displayed that the sensor shows high analytical performance for Pb2+ due to the synergy of Mn(TPA) with highly selective binding to Pb2+ and SWCNTs with high electronic conductivity. Under the optimal conditions, the Mn(TPA)-SWCNTs-based electrochemical sensor presented a wide linear response over the concentration range from 0.10 to 14.0µM. The limit of detection was achieved to be 38nM. Satisfactory results were also achieved when the Mn(TPA)-SWCNTs-based sensor was utilized for the determination of Pb2+ in the practical samples of industrial wastewater and human serum, suggesting great promising of the sensor for practical application.

Electroactive crown ester-Cu2+ complex with in-situ modification at molecular beacon probe serving as a facile electrochemical DNA biosensor for the detection of CaMV 35s.

A novel electrochemical DNA biosensor has been facilely constructed by in-situ assembly of electroactive 4'-aminobenzo-18-crown-6-copper(II) complex (AbC-Cu2+) on the free terminal of the hairpin-structured molecule beacon. The 3'-SH modified molecule beacon probe was first immobilized on the gold electrode (AuE) surface through self-assembly chemistry of Au-S bond. Then the crow ester of AbC was covalently coupled with 5'-COOH on the molecule beacon, and served as a platform to attach the Cu2+ by coordination with ether bond (-O-) of the crown cycle. Thus, an electroactive molecule beacon-based biosensing interface was constructed. In comparison with conventional methods for preparation of electroactive molecule beacon, the approach presented in this work is much simpler, reagent- and labor-saving. Selectivity study shows that the in-situ fabricated electroactive molecule beacon remains excellent recognition ability of pristine molecule beacon probe to well differentiate various DNA fragments. The target DNA can be quantatively determined over the range from 0.10pM to 0.50nM. The detection limit of 0.060pM was estimated based on signal-to-noise ratio of 3. When the biosensor was applied for the detection cauliflower mosaic virus 35s (CaMV 35s) in soybean extraction samples, satisfactory results are achieved. This work opens a new strategy for facilely fabricating electrochemical sensing interface, which also shows great potential in aptasensor and immurosensor fabrication.

Graphene oxide directed in-situ synthesis of Prussian blue for non-enzymatic sensing of hydrogen peroxide released from macrophages.

A novel electrochemical non-enzymatic hydrogen peroxide (H2O2) sensor has been developed based on Prussian blue (PB) and electrochemically reduced graphene oxide (ERGO). The GO was covalently modified on glassy carbon electrode (GCE), and utilized as a directing platform for in-situ synthesis of electroactive PB. Then the GO was electrochemically treated to reduction form to improve the effective surface area and electroactivity of the sensing interface. The fabrication process was characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and atomic force microscopy (AFM). The results showed that the rich oxygen containing groups play a crucial role for the successful synthesis of PB, and the obtained PB layer on the covalently immobilized GO has good stability. Electrochemical sensing assay showed that the modified electrode had tremendous electrocatalytic property for the reduction of H2O2. The steady-state current response increased linearly with H2O2 concentrations from 5µM to 1mM with a fast response time (less than 3s). The detection limit was estimated to be 0.8µM. When the sensor was applied for determination of H2O2 released from living cells of macrophages, satisfactory results were achieved.