Studies on preparing and adsorption property of grafting terpolymer microbeads of PEI-GMA/AM/MBA for bilirubin

Crosslinking copolymer microbeads with a diameter range of 100-150 microm were synthesized by suspension copolymerization of glycidyl methacrylate (GMA), acrylamide (AM) and N,N'-methylene bisacrylamide (MBA). Subsequently, polyethyleneimine (PEI) was grafted on the surfaces of the terpolymer microbeads GMA/AM/MBA via the ring-opening reaction of the epoxy groups, and the grafting microbeads PEI-GMA/AM/MBA were prepared. In this paper, the adsorption property of the grafting microbeads for bilirubin was mainly investigated, and the effects of various factors, such as pH value, ionic strength and grafting degree of PEI on the surface of grafting microbeads and the adsorption capacity of the grafting microbeads for bilirubin were examined. The batch adsorption experiment results show that by right of the action of grafted polyamine macromolecules PEI, the grafting microbeads PEI-GMA/AM/MBA have quite strong adsorption ability for bilirubin; the isotherm adsorption conforms to Freundlich equation. The pH value of the medium affects the adsorption capacity greatly, As in the nearly neutral solutions with pH 6, the grafting microbeads have the strongest adsorption ability for bilirubin, whereas in acidic and basic solutions their adsorption ability is weak. The ionic strength hardly affects the adsorption ability of the grafting microbeads. The grafting degree of PEI on the surfaces of the grafting microbeads also has a great effect on the adsorption capacity, and higher the grafting degree of PEI on the surface of the microbead PEI-GMA/AM/MBA, the stronger is the adsorption ability of the microbeads.     

Preparation of surface molecularly imprinted polymeric microspheres and their recognition property for basic protein lysozyme

The surface imprinting of basic protein lysozyme (Lys) was carried out by designing a new route. The copolymerization of N-vinylpyrrolidone (NVP) and 2-hydroxyethyl methacrylate (HEMA) was first conducted in an inverse suspension polymerization system, and the crosslinked copolymeric microspheres HEMA/NVP were prepared. Subsequently, the esterification reaction of methacryloyl (MAO) chloride with the hydroxyl groups on the surfaces of HEMA/NVP microspheres was performed, and the modified microspheres MAO–HEMA/NVP, on which a mass of polymerisable double bonds were introduced, were obtained. In the presence of lysozyme, by initiating of K₂S₂O₈–NaHSO₃, the monomer methacrylic acid (MAA) in the solution was crosslink-polymerized on the surfaces of MAO–HEMA/NVP microspheres, resulting in the surface imprinting of lysozyme. After removing the template molecules, the lysozyme molecule-surface-imprinted material MIP-HEMA/NVP was obtained. Because there were strong interactions between lysozyme and monomer MAA, electrostatic interaction and hydrogen bonding, the lysozyme molecule-surface imprinting was successfully realized. The MIP-HEMA/NVP microspheres have very high binding affinity for lysozyme, and the binding capacity gets up to 216 mg/g. It is more important that MIP-HEMA/NVP microspheres have specific recognition selectivity for lysozyme, and the selectivity coefficient for lysozyme with respect to bovine hemoglobin (BHb), which was used as a contrast protein in the experiments, actually reaches 31.07. In the respect of protein imprinting, the imprinting material with such high performance is unwonted.     

Reversible lysozyme immobilization onto N,N′-bis-(3-(4-morpholino)-propyl)-3,4,9,10-perylenetetracarboxylic acid dimide (MPPDI) attached polymeric nanospheres

Novel hydrophobic nanospheres with an average size of 200 nm utilizing N,N′-bis-(3-(4-morpholino)-propyl)-3,4,9,10-perylenetetracarboxylic acid dimide (MPPDI) as a monomer were prepared by surfactant free emulsion polymerization of 2-hydroxyethyl methacrylate (HEMA) and MPPDI conducted in an aqueous dispersion medium. The nanospheres were used for the adsorption of lysozyme. The system parameters, such as effect of the adsorption conditions (i.e. enzyme concentration, medium pH, and temperature) and the reusability of the support were studied. Specific surface area of the nonporous nanospheres was found 664 m²/g. Poly(HEMA–MPPDI) nanospheres were characterized by Fourier transform infrared spectroscopy (FT-IR), elemental analysis and scanning electron microscopy (SEM). Then, poly(HEMA–MPPDI) nanospheres were used in the adsorption of lysozyme in batch system. Using an optimized adsorption protocol, 400 mg lysozyme/g nanosphere loading capacity was obtained. The adsorption phenomena appeared to follow a typical Langmuir isotherm. Lysozyme could be repeatedly adsorbed and desorbed with poly(HEMA–MPPDI) nanospheres without noticeable loss in the adsorption capacity.     

Adsorption of gamma-globulin, a model protein for antibody, on colloidal particles

The effect of surface properties on the adsorption of bovine gamma-globulin, a model protein for antibody, was studied. Polystyrene latex (PS), hydrophilic copolymer lattices of styrene/2-hydroxyethyl methacrylate [P(S/HEMA)], styrene/ methacrylic acid [P(S/MAA)] and methyl methacrylate/ 2-hydroxyethyl methacrylate [P(MMA/HEMA)], and colloidal silica were used. The adsorption isotherms of gamma-globulin on these colloidal particles were measured as a function of pH and ionic strength. The hydrophilic particles showed low affinities for gamma-globulin at alkaline pH, while PS showed high affinities for gamma-globulin over the whole range of pH and ionic strength. The gamma-globulin adsorption on hydrophilic particles was highly reversible with respect to the pH and ionic strength compared with that on PS. These differences indicate that the dominant driving forces of adsorption are related to the hydrophilicity of particles. The adsorption isotherms of all colloidal particles showed the plateau values, and the order of maximum values of plateau adsorption was P(S/MAA) > PS or P(S/HEMA), silica > P(MMA/HEMA). Thus, they were also affected by the charged groups and the hydrophilicity of the surfaces. On the other hand, the plateau values of all colloidal particles were more or less symmetrical with a maximum at around the isoelectric point of gamma-globulin at an ionic strength of 0.01. This behavior is attributed to the important role of the lateral interaction between the adsorbed molecules at low ionic strength.     

IPNs based on chitosan with NVP and NVP/HEMA synthesised through photoinitiator-free photopolymerisation technique for biomedical applications

Biocompatible interpenetration polymeric network (IPN) hydrogels based on chitosan with N-vinylpyrrolidinone (NVP) as well as its copolymer with 2-hydroxymethyl methacrylate (HEMA) were synthesised using the photopolymerisation technique without the inclusion of any photoinitiator or crosslinking agent. These hydrogels were characterised using the Fourier-transform infrared spectroscopy (FTIR) technique. Equilibrium swelling of these hydrogels was performed in Milli-Q water and drug release studies were carried out using theophylline as the model drug. These tests showed that the IPN comprised of chitosan and NVP with a very small amount of N-hydroxymethyl maleimide (HMMI) included exhibited higher swelling abilities and fast drug release rates than the IPN which contained chitosan, NVP and HEMA. Kinetic studies of water diffusion into these hydrogels and drug release revealed that with the exception of the IPN with HEMA incorporated, the other hydrogels did not adhere to the Fickian diffusion model. These hydrogels were tested for their biocompatibility with human epidermal keratinocyte cells (HaCaT). A positive cell growth as evidenced by the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) cell proliferation assay indicated that these hydrogels are non-toxic to human keratinocytes and can be potentially used as biomaterials for biomedical applications.     

Development of the magnetic beads for dye ligand affinity chromatography and application to magnetically stabilized fluidized bed system

Magnetic poly(2-hydroxyethylmethacrylate) [mPHEMA] beads were prepared by suspension polymerization of HEMA in the presence of Fe₃O₄ nano-powder. Cibacron Blue F3GA was covalently immobilized to the mPHEMA beads via nucleophilic substitution reaction between chloride of its triazine ring and hydroxyl groups of HEMA under alkaline conditions. The mPHEMA/Cibacron Blue F3GA beads (100–140 μm in diameter) carrying 68.3 μmol Cibacron Blue F3GA per gram polymer were used for β-casein adsorption studies. Adsorption studies were performed under different conditions in a batch system (i.e., pH, β-casein initial concentration, temperature, and ionic strength) and then in a magnetically stabilized fluidized bed (MSFB) system. The swelling ratio of the mPHEMA was 62.1%. The maximum adsorption capacity for batch system was 20.2% lower as compared to the value obtained in MSFB. The mPHEMA/Cibacron Blue F3GA beads could be repeatedly applied for β-casein adsorption without significant losses in the adsorption capacity.     

Chitosan microspheres as immobilized dye affinity support for catalase adsorption

Chitosan microsphere (CS) was prepared by phase-inversion method as the support matrices. Cibacron Blue F3GA (CB) was covalently attached to the chitosan microspheres, and thus the novel dye-affinity adsorbent was obtained. These Cibacron Blue F3GA-attached chitosan microspheres (CB-CS) were used in the catalase (CAT) adsorption studies. The maximum CAT adsorption capacity of Cibacron Blue F3GA-attached chitosan microspheres was 28.4 mg/g at pH 7.0. Langmuir adsorption model was found to be applicable in interpreting CAT adsorption. Significant amount of the adsorbed CAT (up to 90.6%) was eluted in the elution medium containing 0.5 M NaSCN at pH 8.0. It appears that CB-CS can be applied for adsorption of CAT without causing any denaturation.     

Designing chitosan based magnetic beads with conocarpus waste-derived biochar for efficient sulfathiazole removal from contaminated water

The development of a simple method to synthesize highly efficient and stable magnetic microsphere beads for sulfathiazole (STZ) removal from contaminated aqueous media was demonstrated in this study. Conocarpus (Conocarpus erectus L.) tree waste (CW) derived biochar (BC) was modified to fabricate chitosan-BC (CBC) and magnetic CBC (CBC-Fe) microsphere beads. Proximate, chemical, and structural properties of the produced adsorbents were investigated. Kinetics, equilibrium, and pH adsorption batch trials were conducted to evaluate the effectiveness of the synthesized adsorbents for STZ removal. All adsorbents exhibited the highest STZ adsorption at pH 5.0. STZ adsorption kinetics data was best emulated using pseudo-second order and Elovich models. The equilibrium adsorption data was best emulated using Langmuir, Freundlich, Redlich–Peterson, and Temkin models. CBC-Fe demonstrated the highest Elovich, pseudo-second order, and power function rate constants, as well as the highest apparent diffusion rate constant. Additionally, Langmuir isotherm predicted maximum adsorption capacity was the highest for CBC-Fe (98.67 mg g⁻¹), followed by CBC (56.54 mg g⁻¹) and BC (48.63 mg g⁻¹). CBC-Fe and CBC removed 74.5%–108.8% and 16.2%–25.6% more STZ, respectively, than that of pristine BC. π-π electron-donor–acceptor interactions and Lewis acid-base reactions were the main mechanisms for STZ removal; however, intraparticle diffusion and H-bonding further contributed in the adsorption process. The higher efficiency of CBC-Fe for STZ adsorption could be due to its magnetic properties as well as stronger and conducting microsphere beads, which degraded the STZ molecules through generation of HO^• radicals.     

A new metal chelate affinity adsorbent for cytochrome C

We have prepared a novel metal-chelate adsorbent utilizing N-methacryloyl-L-histidine methyl ester (MAH) as a metal-chelating ligand. MAH was synthesized by using methacryloyl chloride and l-histidine methyl ester dihydrochloride. Spherical beads with an average diameter of 75-125 microm were produced by suspension polymerization of 2-hydroxyethyl methacrylate (HEMA) and MAH carried out in an aqueous dispersion medium. Then, Cu(2+) ions were chelated directly on the chelating beads. Cu(2+)-chelated beads were used in the adsorption of cytochrome c (cyt c) from aqueous solutions. The maximum cyt c adsorption capacity of the Cu(2+)-chelated beads (658.2 micromol/g Cu(2+) loading) was found to be 31.7 mg/g at pH 10 in phosphate buffer. The nonspecific cyt c adsorption on the naked PHEMA beads was 0.2 mg/g. Cyt c adsorption increased with increasing Cu(2+) loading. Cyt c adsorption capacity was demonstrated for the buffer types with the effects in the order phosphate > HEPES > MOPS > MES > Tris-HCl. Cyt c molecules could be adsorbed and desorbed five times with these adsorbents without noticeable loss in their cyt c adsorption capacity.     

New intrinsically radiopaque hydrophilic microspheres for embolization: synthesis and characterization

Polymeric particles currently used for embolization procedures have the disadvantage that they are radiolucent, that is, invisible on X-ray images, and consequently the interventional radiologist has to resort to angiography to (indirectly) monitor the fate of the particles. Here, we introduce intrinsically radiopaque hydrophilic microspheres. Since these microspheres can directly be visualized on X-ray images, using these microspheres for embolization purposes will allow superprecise location of the embolic material, both during and after the procedure. The microspheres, which are prepared by suspension polymerization, are based on the radiopaque monomer 2-[4-iodobenzoyl]-oxo-ethylmethacrylate and hydroxyethylmethacrylate (HEMA) and/or 1-vinyl-2-pyrrolidinone (NVP) as hydrophilic component. It has been shown that for clinically relevant X-ray visibility the spheres should contain at least 20 wt % iodine. At this iodine content, copolymerization with HEMA results in spheres that hardly imbibe water (EQ = 1.08). When HEMA is replaced by NVP, the volume swelling ratio can be significantly increased (to 1.33).     

Lysozyme purification with dye-affinity beads under magnetic field

Magnetic poly(2-hydroxyethyl methacrylate) mPHEMA beads carrying Cibacron Blue F3GA were prepared by suspension polymerization of HEMA in the presence of Fe3O4 nano-powder. Average size of spherical beads was 80-120 microm. The beads had a specific surface area of 56.0m(2)/g. The characteristic functional groups of dye-attached mPHEMA beads were analyzed by Fourier transform infrared spectrometer (FTIR) and Raman spectrometer. mPHEMA with a swelling ratio of 68% and carrying 28.5 micromol CibacronBlueF3GA/g were used for the purification of lysozyme. Adsorption studies were performed under different conditions in a magnetically stabilized fluidized bed (i.e., pH, protein concentration, flow-rate, temperature, and ionic strength). Lysozyme adsorption capacity of mPHEMA and mPHEMA/Cibacron Blue F3GA beads were 0.8 mg/g and 342 mg/g, respectively. It was observed that after 20 adsorption-desorption cycle, mPHEMA beads can be used without significant loss in lysozyme adsorption capacity. Purification of lysozyme from egg white was also investigated. Purification of lysozyme was monitored by determining the lysozyme activity using Micrococcus lysodeikticus as substrate. The purity of the desorbed lysozyme was about 87.4% with recovery about 79.6%. The specific activity of the desorbed lysozyme was high as 41.586 U/mg.     

Methacryloylamidohistidine in affinity ligands for immobilized metal-ion affinity chromatography of ferritin

A new metal-chelate adsorbent utilizing 2-methacryloylamidohistidine (MAH) was prepared as a metalchelating ligand. MAH was synthesized using methacryloly chloride and histidine. Monosize nanospheres with an average diameter of 450 nm were produced by emulsion polymerization of 2-hydroxyetylmethacrylate (HEMA) and MAH. Then, Fe³⁺ ions were chelated directly onto the monosize nanospheres. Mon-poly(HEMA-MAH) nanospheres were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, and elemental analysis. Fe³⁺ chelated monosize nanospheres were used in ferritin adsorption from an aqueous solution. The maximum ferritin adsorption capacity of Fe³⁺-chelated mon-poly(HEMAMAH) nanospheres was 202 mg/g at pH 4.0 in acetate buffer. The non-specific ferritin adsorption on the monpoly( HEMA-MAH) nanospheres was 20 mg/g. The adsorption behavior of ferritin could be modeled using both Langmuir and Freundlich isotherms. The adsorption capacity decreased with increasing ionic strength of the binding buffer. High desorption ratios (> 95% of the adsorbed ferritin) were achieved with 1.0 M NaCl at pH 7.0. Ferritin could be repeatedly adsorbed and desorbed with the Fe³⁺-chelated mon-poly(HEMA-MAH) nanospheres without significant loss of adsorption capacity.     

Synthesis of CarAlg/MMt nanocomposite hydrogels and adsorption of cationic crystal violet

CarAlg/MMt nanocomposite hydrogels composed of kappa-carrageenan (Car) and sodium alginate (Alg) biopolymers were synthesized by incorporation of sodium montmorillonite (Na-MMt) nanoclay. Acrylamide (AAm), methylenebisacrylamide (MBA), and ammonium persulfate (APS) were used as monomer, crosslinker, and initiator, respectively. The structure and morphology of nanocomposites were characterized by XRD, SEM, and TEM techniques. The XRD results showed exfoliated MMt nanoclay and exfoliation of MMt was confirmed by TEM graph. The resulting nanocomposites were evaluated to remove cationic crystal violet (CV) dye from water. According to data, the adsorption capacity of nanocomposites was enhanced as the clay content was increased. The experimental data were analyzed according to both Langmuir and Freundlich models and experimental maximum adsorption capacity was obtained 88.8 mg g⁻¹. By studying the effect of pH on the dye adsorption capacity of nanocomposites, it was revealed that the adsorption capacity of nanocomposites was enhanced at acidic pHs as the Na-MMt nanoclay and kappa-carrageenan components were increased.     

New sorbent for bilirubin removal from human plasma: Cibacron Blue F3GA-immobilized poly(EGDMA–HEMA) microbeads

Cibacron Blue F3GA-immobilized poly(EGDMA–HEMA) microbeads were investigated as a specific sorbent for bilirubin removal from human plasma. The poly(EGDMA–HEMA) microbeads were prepared by a modified suspension copolymerization technique. Cibacron Blue F3GA was covalently coupled to the poly(EGDMA–HEMA) microbeads via the nucleophilic reaction between the chloride of its triazine ring and the hydroxyl groups of the HEMA molecule, under alkaline conditions. Bilirubin adsorption was investigated from hyperbilirubinemic human plasma on the poly(EGDMA–HEMA) microbeads containing different amounts of immobilized Cibacron Blue F3GA, (between 5.0–16.5 μmol/g). The non-specific bilirubin adsorption on the unmodified poly(EGDMA–HEMA) microbeads were 0.32 mg/g from human plasma. Higher bilirubin adsorption values, up to 14.8 mg/g, were obtained with the Cibacron Blue F3GA-immobilized microbeads. Bilirubin molecules interacted with these sorbents directly. Contribution of albumin adsorption on the bilirubin adsorption was pronounced. Bilirubin adsorption increased with increasing temperature.     

Characteristics of xanthan gum-based biodegradable superporous hydrogel

A novel biopolymer-based superporous hydrogel (SPH) was synthesized through chemical crosslinking by graft copolymerization of 2-hydroxyethyl methacrylate (HEMA) and acrylic acid (AA) on to xanthan gum (XG) via redox initiator system of ammonium persulfate (APS) and N, N, N′, N′-tetramethylethylenediamine (TMED), in the presence of N, N′-methylenebisacrylamide (MBA) crosslinking agent, sodium bicarbonate foaming agent, a triblock copolymer of polyoxyethylene/polyoxypropylene/polyoxyethylene as a foam stabilizer. Characterization of SPH was done by FT-IR, TGA, SEM, HPC and GCMS. The effects of pH and salinity on the swelling aptitude of the SPH were investigated along with its degradability in Streptococcus bovis medium.     

Microfluidic device‐assisted etching of p‐HEMA for cell or protein patterning

The construction of biomaterials with which to limit the growth of cells or to limit the adsorption of proteins is essential for understanding biological phenomena. Here, we describe a novel method to simply and easily create thin layers of poly (2‐hydroxyethyl methacrylate) (p‐HEMA) for protein and cellular patterning via etching with ethanol and microfluidic devices. First, a cell culture surface or glass coverslip is coated with p‐HEMA. Next, a polydimethylsiloxane (PDMS) microfluidic is placed onto the p‐HEMA surface, and ethanol is aspirated through the device. The PDMS device is removed, and the p‐HEMA surface is ready for protein adsorption or cell plating. This method allows for the fabrication of 0.3 µm thin layers of p‐HEMA, which can be etched to 10 µm wide channels. Furthermore, it creates regions of differential protein adhesion, as shown by Coomassie staining and fluorescent labeling, and cell adhesion, as demonstrated by C2C12 myoblast growth. This method is simple, versatile, and allows biologists and bioengineers to manipulate regions for cell culture adhesion and growth. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 34:243–248, 2018     

Dye affinity chromatography for fast and simple purification of fucoidan from marine brown algae

Fucoidan is a sulfated polysaccharide with promising pharmacological applications. Due to its medicinal properties, there is a demand for a separation technique that yields a high purification grade. Here, we present a novel purification tool for recovering fucoidan from the marine brown macroalgae Fucus vesiculosus. The developed method is based on amino‐derivatized Sepabeads^® EC‐EA. The beads were modified with toluidine blue (TB), a thiazine derivative, to exploit the strong donor acceptor interactions between the cationic dye and the anionic polysaccharide. The adsorption kinetics and the binding capacity of the resin were analyzed. A Sips model was used to approximate the adsorption isotherm, resulting in a maximum capacity of 127.7 mg fucoidan per g adsorbent. Investigation of the effect of adsorption step's pH on purity and chemical structure was performed by TB and Fourier transform infra‐red spectroscopy assays. Results showed that adsorption at pH 1 and 6 had negligible effects on fucoidan's chemical structure. However, purity was actually improved by 1.55‐ and 1.69‐fold at pH 1 and 6, respectively, with an average yield of 5 g/100 g dried algae powder. In contrast, only a 1.46‐fold increment was observed in fucoidan purified by the traditional method at pH 2, with a yield of 7.5 g/100 g dried algae powder. Furthermore, fucoidan purified by this method at pH 6 complies with, or even exceeds the quality of the commercially available (≥95% pure) fucoidan (Sigma‐Aldrich^®) with respect to molecular weight and sulfur content. Therefore, dye affinity chromatography provides more advantages than the classically used techniques for fucoidan purification.     

Layer‐by‐Layer Na3V2(PO4)3 Embedded in Reduced Graphene Oxide as Superior Rate and Ultralong‐Life Sodium‐Ion Battery Cathode

Na₃V₂(PO₄)₃ (NVP) is regarded as a promising cathode for advanced sodium‐ion batteries (SIBs) due to its high theoretical capacity and stable sodium (Na) super ion conductor (NASICON) structure. However, strongly impeded by its low electronic conductivity, the general NVP delivers undesirable rate capacity and fails to meet the demands for quick charge. Herein, a novel and facile synthesis of layer‐by‐layer NVP@reduced graphene oxide (rGO) nanocomposite is presented through modifying the surface charge of NVP gel precursor. The well‐designed layered NVP@rGO with confined NVP nanocrystal in between rGO layers offers high electronic and ionic conductivity as well as stable structure. The NVP@rGO nanocomposite with merely ≈3.0 wt% rGO and 0.5 wt% amorphous carbon, yet exhibits extraordinary electrochemical performance: a high capacity (118 mA h g^?1 at 0.5 C attaining the theoretical value), a superior rate capability (73 mA h g^?1 at 100 C and even up to 41 mA h g^?1 at 200 C), ultralong cyclability (70.0% capacity retention after 15 000 cycles at 50 C), and stable cycling performance and excellent rate capability at both low and high operating temperatures. The proposed method and designed layer‐by‐layer active nanocrystal@rGO strategy provide a new avenue to create nanostructures for advanced energy storage applications.     

Nanoflake‐Assembled Hierarchical Na3V2(PO4)3/C Microflowers: Superior Li Storage Performance and Insertion/Extraction Mechanism

Na₃V₂(PO₄)₃ (NVP) has excellent electrochemical stability and fast ion diffusion coefficient due to the 3D Na⁺ ion superionic conductor framework, which make it an attractive cathode material for lithium ion batteries (LIBs). However, the electrochemical performance of NVP needs to be further improved for applications in electric vehicles and hybrid electric vehicles. Here, nanoflake‐assembled hierarchical NVP/C microflowers are synthesized using a facile method. The structure of as‐synthesized materials enhances the electrochemical performance by improving the electron conductivity, increasing electrode–electrolyte contact area, and shortening the diffusion distance. The as‐synthesized material exhibits a high capacity (230 mAh g^?1), excellent cycling stability (83.6% of the initial capacity is retained after 5000 cycles), and remarkable rate performance (91 C) in hybrid LIBs. Meanwhile, the hybrid LIBs with the structure of NVP || 1 m LiPF₆/EC (ethylene carbonate) + DMC (dimethyl carbonate) || NVP and Li₄Ti₅O₁₂ || 1 m LiPF₆/EC + DMC || NVP are assembled and display capacities of 79 and 73 mAh g^?1, respectively. The insertion/extraction mechanism of NVP is systematically investigated, based on in situ X‐ray diffraction. The superior electrochemical performance, the design of hybrid LIBs, and the insertion/extraction mechanism investigation will have profound implications for developing safe and stable, high‐energy, and high‐power LIBs.     

Immobilization of endo-polygalacturonase from Aspergillus niger on various types of macromolecular supports

Endo-polygalacturonase (endo-PG) was immobilized on a wide range of natural and synthetic macromolecular supports and their modified derivatives representing many chemical classes, including esters, amides, phenols, alkyl- and arylamines, and carboxyl derivatives. The immobilization entailed methods of adsorption alone as well as covalent bond formation using glutaraldehyde or carbodiimide or via the diazo-coupling reaction. The most promising system proved to be immobilization on trimalehylchitosan (TMC) via adsorption followed by treatment with glutaraldehyde (GA). The binding capacity of the support is on the order of 13,000 IU/g, half of which is active. Various properties of immobilized endo-PG were evaluated. The optimum pH of the enzyme shifted to the alkaline side. The relative catalytic activity was considerably high even at room temperature and remained so above 70 degrees C. The thermal stability at pH 3-4 was notably improved by immobilization, the half-time doubling. Finally, the apparent K(m) was greater for immobilized endo-PG than for native enzyme, while the V(max) was smaller for the immobilized enzyme.