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Here, we report the preparation of hydrogen-bonded complex fibers of graphene oxide (GO) and polyethylene oxide (PEO) and their reduction to conductive fiber. The complexation behaviors of PEO and GO at different pH values are investigated. When pH is below 2.0, PEO and GO will form the complex which precipitates out from the solution quickly. When pH is higher than 5.0, GO and PEO mixed solution will be homogenous. At pH 6.0 the GO/PEO solution shows good fluidity and pre-orientation of GO sheets. The solution is extruded into 1.0 M HCl solution where hydrogen bonding between PEO and GO is constructed and hence the fiber forms. After reduction, the fibers show good mechanical and electrical properties, and the mechanical strength is close to 500 MPa while the conductivity is more than 200 S/cm. The reduced fibers can be assembled into flexible supercapacitor, exhibiting potential for wearable electronics.

Lipid peroxidation plays a crucial role in early brain injury (EBI) after subarachnoid hemorrhage (SAH), and cystine/glutamate antiporter system Xc- has been proved to be associated with glutathione (GSH) synthesis, which protects cells against oxidative damage. Antioxidant effect of system Xc- is mediated by Beclin 1 (BECN1). Therefore, this study aimed to determine whether administration of BECN1 small interfering RNA (siRNA) could attenuate EBI after SAH experiment, specifically through suppressing lipid peroxidation and increasing system Xc- activity. Endovascular perforation was performed to induce SAH in a rat model and BECN1 siRNA was administered through intracerebroventricular injection. Neurological score, brain edema, lipid peroxidation (malondialdehyde, MDA), and antioxidation system, containing GSH, glutathione peroxidase (GSH-Px), glutathione reductase (GR), and anti-reactive oxygen species (anti-ROS), were examined. The expression of BECN1 and light chain of system Xc- (xCT) was detected by western blot, immunoprecipitation, and immunofluorescence staining. This study confirmed that SAH induced neurological deficits and brain edema, which was accompanied by the increase of BECN1 expression and lipid peroxidation, and the decrease of xCT expression and antioxidative capacity. However, downregulation of BECN1 by siRNA could decrease the formation of the BECN1-xCT complex and lipid peroxidation, enhance antioxidative capacity, and ameliorate neurological deficits and brain edema in SAH rats. The results suggested that inhibition of BECN1 suppresses accumulation of lipid peroxidation by increasing system Xc- activity in EBI after SAH, and BECN1 may be a new effective target for EBI treatment after SAH.

Exploring efficient luminophores in the electrochemiluminescence (ECL) system is highly desired to pursue a sensitive ECL sensing platform. Herein, the black phosphorus nanosheets (BP NSs) with excellent ECL properties are investigated and serve as the luminophore with the coreactant of peroxydisulfate (S2O82-) solution. Moreover, owing to the overlapping of emission and absorbance spectra, effective resonance energy transfer (RET) is realized between the BP NSs and the introduced Au nanoparticles. In order to achieve the portable and miniaturized developing trends for the paper-based ECL sensing platform, a paper-based perovskite solar cell (PSC) device is designed to act as the power source to replace the commonly utilized expensive and cumbersome electrochemical workstation. Benefiting from that, a PSC driven paper-based constant potential ECL-RET sensing platform is constructed, thereby realizing sensitive microRNAs (miRNAs) detection. What's more, to attain the preferable analytical performance, the duplex-specific nuclease (DSN) is also introduced to assist the target recycling signal amplification strategy. Based on this, highly sensitive detection of miRNA-107 with a range from 0.1 pM to 15 nM is achieved by this designed sensing platform. Most importantly, this work not only pioneers a precedent for developing a high-sensitivity PSC triggered ECL sensing platform but also explores the application prospect of BP nanomaterial in the field of bioanalysis.

Poly(acrylic acid) (PAA) was partially grafted with dopamine (PAA-dopa), and then layer-by-layer assembled with poly(vinylpyrrolidone) (PVPON) to prepare hydrogen-bonded (PVPON/PAA-dopa)n film. Polydopamine (PDA) was deposited on (PVPON/PAA-dopa)n film in the presence of oxidant, and hence the whole (PVPON/PAA-dopa)nPDA film was cross-linked. (PVPON/PAA-dopa)nPDA could be utilized as a platform to produce the free-standing Janus film because of the easy detaching process and various chemical reactivity of PDA layer. Ag nanoparticles were formed on (PVPON/PAA-dopa)nPDA film by electroless metallization. 1H,1H,2H,2H-Perfluorodecanethiol (PFDT) was used to further modify the film through Michael addition. After detaching from the substrate, (PVPON/PAA-dopa)20PDA/Ag/PFDT exhibits reversible swelling–shrinking behavior as the pH value changes. This free-standing film shows Janus character, one side is hydrophobic, whereas the other side is hydrophilic. In addition, the hydrophobic surface exhibits a surface-en...

The polymer complex fibers of poly(vinyl alcohol) (PVA) and poly(acrylic acid) (PAA) were produced by inhibiting the complexation to obtain spinnable fluid and initiating the complexation in coagulation bath to make fiber formation. With sulfonic acid as coagulation solution, PVA/PAA fiber can be cross-linked at mild temperature while with hydrochloric acid as coagulation solution is not. The mechanical properties of PVA/PAA fibers strongly depend on environment humidity. As the humidity increases, the fibers show a transition from a glassy state to a rubbery state. Furthermore, dynamic mechanical analysis (DMA) with humidity scans detects not only glass-rubber transition of the cross-linked PVA/PAA fiber but also the secondary relaxation, which reflects molecular motions at the difference scales in the fiber.

CHA zeolite membranes were hydrothermally synthesized by secondary growth method. Original and ball-milled seeds were compared for induction of CHA zeolite membranes. The synthetic parameters were investigated extensively in terms of seed size, precursor composition and crystallization temperature. Impurity MER phase was readily generated in membrane layers when using original CHA seeds (average particle size ∼ 3.80 μm) in an individual K + -containing synthetic medium. Comparatively, pure phase CHA zeolite membranes could be obtained by induction of ball-milled seeds in a broad SiO 2 /Al 2 O 3 ratio and at a low K + concentration. The as-synthesized membranes showed better separation performance than those induced with original seeds. Typically, the CHA zeolite membrane synthesized at 433 K for 20 h in a synthesis gel of 11 SiO 2 :1 Al 2 O 3 :1 K 2 O:1 Na 2 O:550 H 2 O showed a water permeation flux of 2.5 kg m −2 h −1 and separation factor of 2980 for pervaporation dehydration of 90 wt.% ethanol solution at 348 K. The CHA zeolite membrane synthesized with ball-milled seeds was stable for dehydration of acidic ethanol solution (pH ∼3) at 348 K while the membrane induced with original seeds showed a declined separation behavior.

A new type of the surface acoustic wave (SAW) sensor system was delivered. Urease from several kinds of plant seeds was extracted with different extracting solvents. The urease activity, Michaelis constant and other kinetic parameters were estimated for the first time by means of the new device–-SAW sensor system. Some factors such as pH, temperature, activators and inhibitors are also discussed. The method can be applied to the determination of urea content in human urine and the experimental results consist with those reported.

Poly(vinylidene fluoride) (PVDF), polymethyl methacrylate (PMMA) and cellulose acetate (CA) in the presence of N-methyl pyrrolidone were blended in various combinations by using dimethylformamide (DMF) and glacial acetic acid (CH3COOH) as solvent and used to prepare flat-sheet membranes by the phase-inversion process. A square-crossing table with four factors and three levels for the PVDF-PMMA-CA system was designed to study the influences of the casting solution composition and gelation conditions on membrane pore size; preparation conditions for the system were optimized. The results showed that the effect of the casting solution composition was stronger than that of the solid content and the content of the coagulation medium on characteristics of the prepared membrane. The suitable composition for the PVDF-PMMA-CA system was found to be a solid content of 18%, an additive content of 4%, DMF/CH3COOH = 4:1 and a Na2CO3 solution with aa concentration of 2% as the coagulation medium. In addition, it was found that carbon dioxide gas produced by the reaction of glacial acetic acid in the cast solution with sodium carbonate in a coagulation bath can be used to control the even distribution of the membrane pore size during the process of coagulation.

2-Diformylmethylene-1,3-diselenole was prepared and condensed with dithiolium phoshonium bromides and dithiolium phosphonates in the presence of base to give dendralene-type vinylogs of TTF bearing a 1,3-diselenole moiety. The electrochemistry of these dendrimers was studied. SEEPR measurements were also carried out. Calculations were carried out on the radical cations and correlated with the EPR values.

Urease was extracted from several kinds of plant seeds and the kinetic frequency response, the urease activity, Michaelis constants and other kinetic parameters were measured by means of a new device, i.e. a surface acoustic wave (SAW) enzyme sensor system, which was composed of a 61 MHz SAW resonator and a pair of parallel platinum electrodes. Influences such as extracting conditions, pH and temperature and the specificity were also investigated. The method has been successfully applied in the clinical assay of urea in human urine and blood. The results are in agreement with the reported values and also support the clinical diagnosis.

The urea sensor was prepared by combining a surface acoustic wave (SAW) device, in which a SAW resonator operating at 61 MHz and a pair of parallel electrodes were used in series, with urease extracted from green soya bean. The Michaelis constant and maximum reaction rate of the urease were estimated as 2.14 mM and 27.18 kHz min-1, respectively, at pH 7.0 and 25.0 degrees C. Influences of pH, temperature and effectors on the response properties of the SAW urea sensor were investigated. Recovery of the sensor ranged from 95 to 105% and the detection limit of urea was 1.0 micrograms ml-1 (1.7 x 10(-5) M). The proposed sensor has been successfully applied to the rapid determination of urea in human urine samples. The results are consistent with the reported values and also support the clinical diagnosis.

Two methods are described for the determination of l -glutamic acid using a series-electrode piezoelectric quartz crystal sensor. The effect of formaldehyde solution on the frequency shift is discussed. For the calibration curve method, in formaldehyde medium, the detection limit is 3.8 · 10 −5 M, the recovery is 100.4%, the relative standard deviation is 3.32% ( n = 5) and the frequency shift is linear up to 8 · 10 −4 M; in aqueous medium, the above values are 2.0 · 10 −5 M, 99.1%, 3.01% ( n = 6) and 1.1 · 10 −3 M, respectively. The frequencimetric titration method is also described and the lowest titratable concentration of l- glutamic acid is 7.0 · 10 −5 M. The detecting results for tablet samples show good agreement with the values determined by the pharmaceutical method.

A surface acoustic wave (SAW) urease sensor system was developed in which a SAW resonator oscillating at 61 MHz and a pair of parallel electrodes were utilized by coupling with urease extracted from pumpkin seeds. The Michaelis constant and the maximum reaction rate of urease were estimated as 2.08 × 10 −3 mol/1 and 8.85 kHz/min, respectively, at pH 7.5 and 25.0 ° C. The analytical characteristics of the urease sensor system, including influences of pH, temperature on frequency response, calibration curves, reproducibility, selectivity over enzymatic interferences were determined. The recovery of the sensor system ranged from 96 to 105% and the experimental detection limit of urea was 0.50 μg/ml (i.e., 8.3 × 10−6 M, S N = 3 ). The SAW urease sensor system possesses the characteristics of good reproducibility and specificity. It has been successfully applied to the analysis of urea in human blood samples. The assay results are consistent with the results tested by conventional colorimetry and also support clinical diagnosis.

A conductivity cell employing a 61 MHz surface acoustic wave resonator-based measurement circuit was applied to the detection of the urea/urease reaction. The kinetic enzymatic parameters of the urease were estimated from the frequency shifts. The effects of pH, temperature and inhibitor on the response of the enzyme conductivity measurement system were investigated. The system was applied to rapid determination of urea in small urine samples. The lowest detection limit of urea was 30 ng/ml.

2-Diformylmethylene-1,3-diselenole was prepared and condensed with dithiolium phoshonium bromides and dithiolium phosphonates in the presence of base to give dendralene-type vinylogs of TTF bearing a 1,3-diselenole moiety. The electrochemistry of these dendrimers was studied. SEEPR measurements were also carried out. Calculations were carried out on the radical cations and correlated with the EPR values.

An extended set of equations which describe coupled arginase-urease reactions is presented. The mathematical treatment leads to the development of new equations which relate the lag-time required for the concentration of urea to reach a defined fraction of its steady-state concentration to the kinetic parameters of the enzymes, when the steady-state concentration of urea is small compared to its Michaelis constant value, the coupled arginase-urease reaction was monitored with a surface acoustic wave (SAW) enzyme sensor system, to couple the biochemical selectivity of enzymes with the sensitivity of SAW sensors. The proposed theoretical expressions were verified experimentally. The kinetic parameters of urease and arginase (extracted directly from bovine liver) were examined under theoretical guidance. Dependence of the lag-time of the coupled enzyme reaction on the concentrations of urease and arginase is also described.

A new type of surface acoustic wave sensor system for assaying the activity of pancreatic lipase has been proposed. The assay of this enzyme is based on the change in conductance of the solution caused by the release of a fatty acid, using triolein as a substrate. A linear relationship between frequency response and enzyme concentration is obtained. Kinetic parameters of pancreatic lipase, i.e., the Michaelis constant for triolein and the corresponding maximum initial rate, are estimated to be 5.46 mM and 7551.6 Hz/min, respectively. The effects of temperature and pH value are also investigated.