[Construction of controllable polyethylene glycol bioactive coating with hemocompatibility from the surface of modified glass substrate].

A diblock copolymer, poly(ethylene glycol) methacrylate-block-glycidyl methacrylate (PEGMA-GMA), was prepared on glass substrate by surface-initiated atom transfer radical polymerization (SI-ATRP), and endothelial specific peptide Arg-Glu-Asp-Val (REDV) was immobilized at the end of the PEGMA-GMA polymer brush by ring opening reaction through the rich epoxy groups in the GMA. The structure and hydrophilicity of the polymer brushes were characterized by static water contact angle, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The results showed that the REDV modified copolymer brushes were successfully constructed on the glass substrates. The REDV peptide immobilized onto surface was quantitatively characterized by ultraviolet-visible spectroscopy (UV-VIS). The blood compatibility of the coating was characterized by recalcification time and platelet adhesion assay. The results showed that the polymer coating had good blood compatibility. The multifunctional active polymer coating with PEGMA and peptide produced an excellent prospect in surface construction with endothelial cells selectivity.

Robust fabrication of sulfonated graphene oxide/poly (ether sulfone) catalytic membrane reactor for efficient cellulose hydrolysis and product separation.

The efficient conversion of cellulose to high value-added products is important for the utilization of cellulose biomass. Achieving efficient cellulose hydrolysis and timely products separation is the essential target. Herein, a modified sulfonated graphene oxide/polydopamine deposited polyethersulfone (mGO(SO3H)-PDA/PES) membrane reactor, combining in the same unit a conversion effect and a separation effect, was prepared by suction filtration and subsequent polymerization and adhesion. The structure of PES membrane and deposition of PDA was regulated to sure that small molecules can pass through the membrane, while cellulose could not. As a result, the mGO(SO3H)-PDA/PES membrane realized the efficient cellulose hydrolysis and timely products separation under cross-flow circulation mode at 0.1 MPa, avoiding the further degradation of reducing sugar products. The yields of total reducing sugar (TRS) and glucose in separated hydrolysate reached 93.2 % and 85.5 %, respectively. This strategy provides potential guidance for efficient conversion of cellulose.

[FTIR spectrum and detoxication of extracellular polymeric substances secreted by microorganism].

In order to explore the effect of extracelluar polymeric substances (EPS) on resistance and removal of heavy metals, the production of EPS, secreted by cadmium-resistant strain (SCSE425-7) and cadmium-removal strain (SCSE709-6) was investigated combined with Fourier transform infrared spectroscopy (FTIR). The results showed that the high resistance to cadmium of strain SCSE425-7 was related to the high production of soluble EPS, whereas SCSE709-6 secreted more insoluble EPS resulting in better cadmium removal performance. It was indicated that soluble extracellular carbohydrates may help the bacteria to enhance resistance to Cd2+, and insoluble EPS could contribute to Cd2+ removal effectively. The FTIR spectra showed that the peaks of amide and carboxyl were main functional groups for Cd2+ adsorption.

Towards a fast and generalized microplastic quantification method in soil using terahertz spectroscopy.

Extensive investigation of microplastic abundance in soil environment calls for rapid, accurate, efficient and harmonized quantification methods. Development of rapid quantification method requires made-to-measure soil samples with additions of standard polymers. Existing rapid quantification methods ignore the gap between standard polymers in laboratory and household microplastics in soil environment. Here, terahertz (0.6-1.67 thz) and NIR (950-1660 nm) spectroscopy were compared to explore a fast, accurate and potentially generalizable microplastic quantification method in soil. Soil sample was spiked with two standard polymers (polyvinyl chloride (PVC) and polystyrene (PS)) and their additive-containing household microplastics. Two standard sample sets and two household sample sets were prepared in concentrations ranging from 0.5 to 10%. Nine commonly used preprocessing methods and three machine learning algorithms were coupled to develop methods. Models were constructed by training sets from standard sample sets. When models transferred to household samples, prediction error (RMSE) of proposed terahertz method (Wdenosie_PLSR) only increased by 0.4% for PVC and 0.19% for PS, yet that of the NIR method increased by 1.49% and 1.16% respectively. The proposed terahertz method presented a detection limit around 1.12% and the NIR method showed a detection limit around 3.24%. Overall, our results suggest that compared with NIR method, the proposed terahertz method is not only more accurate but also demonstrate stronger generalizability to bridge the gaps between standard PVC/PS polymers and household PVC/PS microplastics. We also propose MMD heatmap for diagnosing spectral preprocessing methods to further improve method efficiency.

A porphyrin-based optical sensor membrane prepared by electrostatic self-assembled technique for online detection of cadmium(II).

An optical sensor membrane was prepared by electrostatic self-assembled technique for online detection of cadmium ion (II) (Cd(II)). The optical indicator 5,10,15,20-tetrakis(4-N-methylpyridyl) porphyrin p-toluenesulfonate (TMPyP) was adsorbed on a hydrolyzed polyacrylonitrile (PAN) membrane by electrostatic attraction and further immobilized through layer-by-layer deposition of poly(allylamine hydrochloride) (PAH) and poly(sodium 4-styrenesulfonate) (PSS) on the membrane surface. The electrostatic self-assembly of polyelectrolytes on the membrane is influenced by pH and salt concentration of polyelectrolytes. The optical sensor membrane shows distinct color and spectral response to Cd(II) under static and flow-through conditions based on the coordination of TMPyP with Cd(II). A faster detection of Cd(II) is achieved at higher feed concentration of Cd(II) or appropriate lower immobilization capacity of TMPyP on the membrane. The flow-through detection is also influenced by the flow rate; higher flow rate led to faster response to Cd(II) during filtration. Compared with the static process, the flow-through conditions are more conducive to faster analysis of ppb level concentration of Cd(II) (10-3 mg L-1) due to a promoted mass transfer and filtration enrichment. Hence, the development of the optical sensor membrane in this study demonstrated the prospect to make membranes multifunctional with advantages for online chromatic warning in addition to adsorption/rejection of heavy metal ions in the solutions that are treated.

Bioinspired EVAL membrane modified with cilia-like structures showing simultaneously enhanced permeability and antifouling properties.

A simple and effective strategy to simultaneously enhance the permeability and antifouling properties of ethylene vinyl alcohol (EVAL) membrane was developed based on the bioinspired natural cleaner, cilia. Taking clue from the self-cleaning effect of cilia, supramolecular polyrotaxanes (PRs) with sliding and rotating cyclic molecules along linear chains were synthesized using azide-alkyne click chemistry. Cilia-like PRs were incorporated into EVAL matrix in the fabrication of modified EVAL membranes. Cilia-like structures protruding from the membrane surface have been observed by SEM, TEM and AFM. By imitating natural ciliary movements, these structures provided a proactive self-cleaning system to remove the foulants. The introduction of cilia-like PRs enhanced the surface roughness and hydrophilicity, and significantly enhanced permeability by 55.3% compared to raw EVAL membrane. Moreover, the membrane modified with cilia-like PRs showed an excellent antifouling property with a lower water flux decline (12.6%) and higher water flux recovery (94%) in dynamic fouling tests. Furthermore, this modified membrane develops the scope of bioinspired membranes, inspiring more attractive potential applications in self-cleaning materials, dynamic membranes and supramolecular machines.

Enhanced hydrolysis of cellulose by catalytic polyethersulfone membranes with straight-through catalytic channels.

The aim of this study was to prepare sulfonated graphene oxide/polyether sulfone (GO-SO3H/PES) mixed matrix membranes (GPMMMs) with high porosity and straight-through catalytic channels by segregation and used for dynamic and continuous hydrolysis of cellulose. The high porosity and segregation increased the exposure of catalysts synergistically and the formative GO-SO3H enriched, straight-through catalytic channels had higher catalytic performance, enhancing the diffusion of hydrolytic products. Dynamic hydrolysis of cellulose is more efficient than static hydrolysis due to the enhanced contact between cellulose and catalysts achieved by the extra driving forces, and the further degradation of produced saccharides was suppressed due to the high freedom of products. The TRS reached 98.18% after 1 h at 150 °C with a catalyst/cellulose mass ratio of 1:5. More importantly, the immobilization of GO-SO3H by PES improved its stability and reusability at high reaction temperature. This strategy provides guidance to the design of high-performance catalytic membranes.

[Spectral analyses during the isolation course of Spirulina platensis phycobilisomes using low-speed centrifugation].

The phycobilisomes were isolated from Spirulina platensis using low-speed centrifugation. The crude phycobilisomes solution extracted by Triton X-100 was centrifugated (13000 rpm) four times. The centrifugated phycobilisomes solution was spectrally analyzed using absorption spectrum each time. The absorption spectrum showed that the ultraviolet absorption maximum of the phycobilisomes solution was still at 263 nm, and also exhibited the characteristic chlorophyllous absorption in the rang of 400-450 nm after the fourth centrifugation. This indicated that there existed small quantities of Triton X-100 and chlorophyll in the centrifugated phycobilisomes solution. But the ultraviolet absorption maximum was red-shifted to 277 nm and the chlorophyllous absorption was not observed in the absorption spectrum of the phycobilisomes solution obtained by high concentration salt precipitation, which meant that the method of high concentration salt precipitation could effectively remove Triton X-100 and chlorophyll from the phycobilisomes solution. The precipitated phycobilisomes of Spirulina platensis were further purified by using Sepharose CL-6B column chromatography. The fluorescence emission maximum of the purified phycobilisomes at room temperature was at 680 nm, which indicated that the purified phycobilisomes were intact.

Electrochemical studies oxidation of ciprofloxacin at nano-SnO2/PVS modified electrode and its interaction with calf thymus DNA.

In pH 6.0 phosphate buffer solutions (PBS), a glassy carbon electrode (GCE) modifying by nano-tin oxide/polyvinyl sulfonic potassium (nano-SnO2/PVS) exhibited an enhanced effectiveness for the oxidation of ciprofloxacin (CFX), which compared with a bare GCE or a nano-SnO2 modified electrode. In addition we also investigated the electrooxidation mechanism of the fluoroquinolone antibiotics (utilizing ciprofloxacin, ofloxacin, sparfloxacin and lomefloxacin) at the modified electrode. Furthermore, gel electrophoresis coupled with electrochemistry and spectra techniques were used to study the interaction of CFX and calf thymus DNA (ctDNA). These acquired data showed that the binding mode of CFX and DNA was mainly an intercalation mechanism.

Biological and optical properties of fluorescent nanoparticles developed for intravascular imaging.

Intravascular tracers in the blood circulation can provide a description of the flow field over time and space. To address the limitations of existing intravascular tracers, we have developed fluorescent nanoparticles capable of providing detailed information regarding the intravascular flow field. The nanoparticles were designed to maximize plasma half-life as well as minimize interactions with other blood components. The bioavailability of the particles in the blood circulation required nanoscale size and low surface charge density. Intravital imaging of nanoparticles in the microcirculation demonstrated that the fluorescence intensity of the nanoparticles was a major determinant of both temporal and spatial resolution of the flow field. We conclude that nanoparticles prepared with these physical and optical properties can provide an accurate description of the localized intravascular flow field.

Poly (3-(3-pyridyl) acrylic acid) modified glassy carbon electrode for simultaneous determination of dopamine, ascorbic acid and uric acid.

Trans-3-(3-pyridyl) acrylic acid (PAA) was deposited on glassy carbon electrode (GCE) by electropolymerization in pH 7.0 phosphate buffer solution (PBS). The poly (3-(3-pyridyl) acrylic acid) (PPAA) film modified glassy carbon electrode shows an excellent electrochemical response for dopamine (DA), ascorbic acid (AA) and uric acid (UA). The cyclic voltammetry oxidation peaks for DA and AA, DA and UA, AA and UA are separated by 150 mV, 130 mV and 280 mV, respectively. This permits the simultaneous determination of AA, DA and UA. The interference of AA with the determination of DA could be eliminated because of the electrostatic interaction between DA cations and the negatively charged PPAA film at pH 7.0. The anodic peak currents of DA, AA and UA increase linearly with concentration in the range of 1-40 micromol L(-1), 10-400 micromol L(-1) and 1.6-80 micromol L(-1), respectively, with a correlation coefficient (r) always higher than 0.998. The detection limit is 0.06 micromol L(-1), 0.8 micromol L(-1) and 1.1 micromol L(-1) for DA, AA and UA, respectively.

Novel affinity membranes with macrocyclic spacer arms synthesized via click chemistry for lysozyme binding.

Affinity membrane has great potential for applications in bioseparation and purification. Disclosed herein is the design of a novel affinity membrane with macrocyclic spacer arms for lysozyme binding. The clickable azide-cyclodextrin (CD) arms and clickable alkyne ethylene-vinyl alcohol (EVAL) chains are designed and prepared. By the azide-alkyne click reaction, the EVAL-CD-ligands affinity membranes with CD spacer arms in three-dimensional micro channels have been successfully fabricated. The FT-IR, XPS, NMR, SEM and SEM-EDS results give detailed information of structure evolution. The abundant pores in membrane matrix provide efficient working channels, and the introduced CD arms with ligands (affinity sites) provide supramolecular atmosphere. Compared with that of raw EVAL membrane, the adsorption capacity of EVAL-CD-ligands membrane (26.24mg/g) show a triple increase. The study indicates that three effects (inducing effect, arm effect, site effect) from CD arms render the enhanced performance. The click reaction happened in membrane matrix in bulk. The effective lysozyme binding and higher adsorption performance of affinity membranes described herein compared with other reported membranes are markedly related with the proposed strategy involving macrocyclic spacer arms and supramolecular working channels.

Selective response of dopamine in the presence of ascorbic acid on L-cysteine self-assembled gold electrode.

A L-cysteine (L-Cys) self-assembled modified gold electrode was used to detect dopamine (DA) by chronoamperometric method (CE) in the presence of ascorbic acid (AA). The defective limit is 2.0 x 10(-8) mol L(-1) (S/N=3). The proposed method was applied to detect DA in the samples with satisfied result.

Poly (O-aminobenzoic acid) modified glassy carbon electrode for electrochemical detection of dopamine in the presence of ascorbic acid.

O-aminobenzoic acid (o-ABA) film is deposited on glassy carbon electrode (GCE) by electropolymerization in pH 7.0 phosphate buffer solution (PBS). The polymeric film shows an excellent electrocatalytical activity on the oxidation of dopamine (DA). Difference pulse voltammetry (DPV) was performed to determine DA in an excess of ascorbic acid (AA). The oxidation peak potentials of DA and AA recorded are 144 mV and -52 mV, respectively. In pH 7.0 PBS, the anodic peak current of DA increases linearly over two concentration intervals, viz., 1.0x10(-7)-1.0x10(-5) mol L(-1) and 1.0x10(-5) - 2.0x10(-4) mol L(-1), with correlation coefficient, 0.9966 and 0.9960, respectively. The relative standard deviation of 10 successive scans is 2.8 % for 1.0x10(-6) mol L(-1) DA and the recovery is 96 % - 101 %. The interference of AA and DOPAC with the determination of DA could be eliminated because of the very distinct attracting interaction between DA cations and the negatively poly (o-ABA) film in pH 7.0 PBS. The proposed method exhibits good recovery and reproducibility.

Quantitative estimate of the effect of cellulase components during degradation of cotton fibers.

A comprehensive mechanistic kinetic model for enzymatic degradation of cotton fibers has been established based on a complete factorial experiment in combination with multivariate stepwise regression analysis. The analysis of the statistical parameter value in the model suggests that the enzymatic degradation of cotton fiber is a progressive and heterogeneous process that includes, at least, two courses that occur sequentially and then progress in parallel. Cellulose fibers were first depolymerized or solubilized by the synergism between cellobiohydrolase I (CBHI) and endoglucanase I (EGI), and then the oligomers obtained were randomly hydrolyzed into glucose by EGI and beta-glucosidase. The proposed model can be applied to the quantitative estimation of the effects of three cellulase components, CBHI, EGI, and beta-glucosidase separately, or in combination during the entire process of cellulose degradation. The validity of the proposed model has been verified by a filter paper activity assay. Its other applicability was also discussed.

Sulfur removal from fuel using zeolites/polyimide mixed matrix membrane adsorbents.

A novel membrane adsorption process was proposed for the sulfur removal from fuels. The mixed matrix membranes (MMMs) adsorbents composed of polyimide (PI) and various Y zeolites were prepared. By the detailed characterization of FT-IR, morphology, thermal and mechanical properties of MMMs adsorbents, combining the adsorption and desorption behavior research, the process-structure-function relationship was discussed. Field-emission scanning electron microscope (FESEM) images show that the functional particles are incorporated into the three-dimensional network structure. MMMs adsorbents with 40% of zeolites content possess better physical properties, which was confirmed by mechanical strength and thermo stability analysis. Influence factors including post-treatment, content of incorporated zeolites, adsorption time, temperature, initial sulfur concentration as well as sulfur species on the adsorption performance of MMMs adsorbents have been evaluated. At 4 wt.% zeolites content, adsorption capacity for NaY/PI, AgY/PI and CeY/PI MMMs adsorbents come to 2.0, 7.5 and 7.9 mg S/g, respectively. And the regeneration results suggest that the corresponding spent membranes can recover about 98%, 90% and 70% of the desulfurization capacity, respectively. The distinct adsorption and desorption behavior of MMMs adsorbents with various functional zeolites was markedly related with their various binding force and binding mode with sulfur compounds.

A passive air sampler for characterizing the vertical concentration profile of gaseous phase polycyclic aromatic hydrocarbons in near soil surface air.

Air-soil exchange is an important process governing the fate of polycyclic aromatic hydrocarbons (PAHs). A novel passive air sampler was designed and tested for measuring the vertical concentration profile of 4 low molecular weight PAHs in gaseous phase (PAH(LMW4)) in near soil surface air. Air at various heights from 5 to 520 mm above the ground was sampled by polyurethane foam disks held in down-faced cartridges. The samplers were tested at three sites: A: an extremely contaminated site, B: a site near A, and C: a background site on a university campus. Vertical concentration gradients were revealed for PAH(LMW4) within a thin layer close to soil surface at the three sites. PAH concentrations either decreased (Site A) or increased (Sites B and C) with height, suggesting either deposition to or evaporation from soils. The sampler is a useful tool for investigating air-soil exchange of gaseous phase semi-volatile organic chemicals.

A sensitive DNA biosensor fabricated with gold nanoparticles/poly (p-aminobenzoic acid)/carbon nanotubes modified electrode.

In this work, we fabricated a sensitive electrochemical DNA biosensor for the detection of target DNA. Aminobenzoic acid (ABA) was firstly electropolymerized on the surface of the glassy carbon electrode (GCE) modified with multi-walled carbon nanotubes with carboxyl groups (MWCNTs) by cyclic voltammetry (CV). Gold nanoparticles (AuNPs) were subsequently introduced to the surface of PABA-MWNTs composite film by electrochemical deposition mode. Probe DNA was immobilized on the surface of AuNPs through Au-S bond. Scanning electron microscopy (SEM), cyclic voltammetry (CV) and electrochemical impedance spectra (EIS) were used to investigate the film assembly process. Differential pulse voltammetry (DPV) was used to monitor DNA hybridization event by measurement of the intercalated adriamycin. Under the optimal conditions, the increase of reduction peak current of adriamycin was linear with the logarithm of the concentration of the complementary oligonucleotides from 1.0 x 10(-12) to 5.0 x 10(-9)M with a detection limit of 3.5 x 10(-13)M. This DNA biosensor has a good stability and reproducibility.

Determination of dopamine in the presence of ascorbic acid by poly(styrene sulfonic acid) sodium salt/single-wall carbon nanotube film modified glassy carbon electrode.

In this study, poly(styrene sulfonic acid) sodium salt/single-wall carbon nanotube film was cast onto the surface of glassy carbon electrode and the electrochemical behavior of the modified electrode was investigated. The results show that the anodic peak current is proportional to the concentration of dopamine in the range of 1.6 x 10(-8)-6 x 10(-4) M. The detection limit is 8 x 10(-9) M. The interference of ascorbic acid with the determination of dopamine could be eliminated due to the very distinct attracting interaction between dopamine cations and the negative poly(styrene sulfonic acid) sodium salt film in pH 7.0 phosphate-buffered saline solutions. The proposed method exhibits good sensitivity, selectivity, and reproducibility.

Changes in the structural properties and rate of hydrolysis of cotton fibers during extended enzymatic hydrolysis.

An extended enzymatic hydrolysis of cotton fibers by crude cellulase from Trichoderma pseudokoningii S-38 is described with characterization of both the enzyme changes of activities and cellulose structure. The hydrolysis rates declined drastically during the early stage and then slowly and steadily throughout the whole hydrolysis process the same trend could be seen during the following re-hydrolysis process. Morphological and structural changes to the fibers, such as swelling, frequent surface erosion, and variation in the packing and orientation of microfibrils, were investigated by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Observation of X-ray diffraction and IR spectra suggests that the hydrolysis process results in a gradual increase in the relative intensity of the hydrogen bond network, and a gradual decrease in the apparent crystal size of cellulose. The I(alpha) crystal phase was hydrolyzed more easily than was the I(beta) crystal phase. Apart from the inactivation of CBHs activity, changes in the packing and arrangement of microfibrils and the structural heterogeneity of cellulose during hydrolysis could be responsible for the reduction in the rate of reaction, especially in its later stages. The results indicate that the enzymatic hydrolysis of cellulose occurs on the outer layer of the fiber surface and that, following this, the process continues in a sub-layer manner.