Synthesis and characterization of periodic mesoporous organosilicas as anion exchange resins for perrhenate adsorption

A new methodology to immobilize ionic liquids through the use of a bridged silsesquioxane N-(3-triethoxysilylpropyl), N(3)-(3-trimethoxysilylpropyl-4,5-dihydroimidazolium iodide that incorporates an ionic functionality for the assembly of novel periodic mesoporous organosilica (PMO) materials has been developed. The resulting PMO materials were investigated for use as novel anion exchange resins for the separation of perrhenate anions in aqueous solution. As compared with cetyltrimethylammonium chloride, 1-hexadecane-3-methylimidazolium bromide has been demonstrated to be a more efficient surfactant template for the generation of mesopores and surface areas for such PMO materials.     

Enzymes in the cavity of hollow silica nanoparticles

Due to limitations of the existing preparative methods of hollow nanoparticles by either heating at high temperature (>600 degrees C) or by using strong acid, alkali, or an organic solvent, it was not possible up till now to encapsulate any sensitive organic molecule like enzyme or others inside the cavity of hollow nanoparticles. We have demonstrated a much softer method of preparing hollow silica nanoparticles with horseradish peroxidase (HRP) inside the cavity by synthesizing HRP-doped core-shell silica-coated silver chloride nanoparticles and finally leaching out silver chloride with dilute ammonia at low temperatures. TEM pictures showed the hollow cavity inside the nanoparticles. The enzyme entrapped in these particles was active. The turnover number of HRP entrapped into these hollow particles and dispersed in aqueous buffer (pH 7.2) (k(cat) = 2.56 x 10(6) s(-1)) was found to be less than that of free enzyme in aqueous buffer (k(cat) = 6.133 x 10(7) s(-1)) but higher than that of HRP entrapped in solid-core silica nanoparticles and dispersed in aqueous buffer (k(cat) = 1.05 x 10(5) s(-1)). The result showed that hollow nanoparticles could be prepared using soft chemical methods and sensitive chemicals like active enzyme could be entrapped in the cavities and it retains its activity.     

One-pot sequences of reactions with sol-gel entrapped opposing reagents: an enzyme and metal-complex catalysts

We extend our sol-gel methodology of one-pot sequences of reactions with opposing reagents to an enzyme/metal-complex pair. Sol-gel entrapped lipase and sol-gel entrapped RhCl[P(C(6)H(5))(3)](3) or Rh(2)Co(2)(CO)(12) were used for one-pot esterification and C-C double bond hydrogenation reactions, leading to saturated esters in good yields. When only the enzyme is entrapped, the homogeneous catalysts quench its activity and poison it. Thus, when 10-undecenoic acid and 1-pentanol were subjected in one pot to the entrapped lipase and to homogeneously dissolved RhCl[P(C(6)H(5))(3)](3) under hydrogen pressure, only 7% of the saturated 1-pentyl undecanoate was obtained. The yield jumped 6.5-fold when both the enzyme and the catalyst were immobilized separately in silica sol-gel matrixes. Similar one-pot esterifications and hydrogenations by sol-gel entrapped lipase and heterogenized rhodium complexes were carried out successfully with the saturated nonoic, undecanoic, and lauric acids together with several saturated and unsaturated alcohols. The use of (S)-(-)-2-methylbutanol afforded an optically pure ester. The heterogenized lipase is capable of inducing asymmetry during esterification with a prochiral alcohol. Both the entrapped lipase and the immobilized rhodium catalysts can be recovered simply by filtration and recycled in further runs without loss of catalytic activity.     

Equilibrium distribution of permeants in polyelectrolyte microcapsules filled with negatively charged polyelectrolyte: the influence of ionic strength and solvent polarity

The effects of ionic strength and solvent polarity on the equilibrium distribution of fluorescein (FL) and FITC-dextran between the interior of polyelectrolyte multilayer microcapsules filled with negatively charged strong polyelectrolyte and the bulk solution were systematically investigated. A negatively charged strong polyelectrolyte, poly(styrene sulfonate) (PSS), used for CaCO3 core fabrication, was entrapped inside the capsules. Due to the semipermeability of the capsule wall, a Donnan equilibrium between the inner solution within the capsules and the bulk solution was created. The equilibrium distribution of the negatively charged permeants was investigated by means of confocal laser scanning microscopy as a function of ionic strength and solvent polarity. The equilibrium distribution of the negatively charged permeants could be tuned by increasing the bulk ionic strength to decrease the Donnan potential. Decreasing the solvent polarity also could enhance the permeation of FL, which induces a sudden increase of permeation when the ethanol volume fraction was higher than 0.7. This is mainly attributed to the precipitation of PSS. A theoretical model combining the Donnan equilibrium and Manning counterion condensation was employed to discuss the results.     

Antimicrobial efficacy and light stability of N-halamine siloxanes bound to cotton

N-halamine silane syntheses and coatings of cotton fabrics as siloxanes were addressed for a series of silanes. The coated fabrics were chlorinated by exposure to dilute sodium hypochlorite with a range of chlorine loadings from 0.20% to 0.26%. Two types of N–Cl moieties were involved in the N-halamine siloxanes, amine and amide. The siloxane-coated cotton swatches were very effective in inactivating Escherichia coli O157:H7 and Staphylococcus aureus, each in 10 min contact time. The N–Cl bond and compound stabilities under UV irradiation and ambient light exposure were also investigated. Both UV and laboratory light stability tests show that most of the chlorine on cotton coated with 3-(3-triethoxysilylpropyl)-7,7,9,9-tetramethyl-1,3,8-triazaspiro[4.5]decane-2,4-dione could be regenerated after irradiation, while most of the lost chlorine from 5,5-dimethyl-3-(3′-triethoxysilylpropyl)hydantoin and 4-[3-triethoxysilylpropoxyl]-2,2,6,6-tetramethylpiperidine could not be recovered upon rechlorination.     

Perfecting imperfect "monolayers": removal of siloxane multilayers by CO2 snow treatment

Self-assembled monolayers (SAMs) of N-(3-triethoxysilylpropyl)-4-hydroxybutyramide were prepared on silicon oxide on silicon (Si/SiO(2)). Initial silane adsorption and high-temperature annealing led to a stable base monolayer with many large over-lying islands of disordered multilayers as a result of the non-self-limited growth process. The disordered multilayers were hydrolyzed and subsequently removed by CO(2) snow treatment. The resulting films were one monolayer thick as measured by ellipsometry. Atomic force microscopy, attenuated total reflection Fourier transform infrared spectroscopy, and contact angle analysis showed that the films were composed of monolayers with full and uniform surface coverage rather than nonuniform coverage by islands or patches of multilayers. Monolayers of octadecyltrichlorosilane were also prepared by multilayer removal via CO(2) treatment, showing the general applicability of the technique toward siloxane SAMs. We believe that CO(2) is an excellent solvent for weakly bound and hydrolyzed molecules that compose multilayers, and this ability to prepare near-perfect monolayer films from imperfect ones allows for less stringent formation conditions.     

高分子聚合物-多壁碳纳米管复合物固定漆酶及其在玻碳电极上的直接电子迁移

采用不同结构的高分子聚合物与纯化的多壁碳纳米管(MWCNTs)共混的方法,制备得到聚合物非共价功能化多壁碳管复合物,测定了这些载体对漆酶(lac)的担载量、固定漆酶的比活力及稳定性.以固定漆酶的复合物修饰玻碳(GC)电极后,采用循环伏安法研究这些电极在无氧磷酸盐缓冲液(PBS)中的直接电化学行为及催化氧还原活力,粗略地测定了固定漆酶与电极间电子转移的速率常数.实验结果表明,当聚合物中含亲漆酶基团或能与漆酶活性中心发生相互作用的官能团时利于直接电子转移,而且复合物固定漆酶保持了游离漆酶的天然构象.这些电极中,lac/NIPAM-co-BPCP-M WCNTs/GC(NIPAM-co-BPCP:N-烯丙基-1-苯甲酰基-3-苯基-4,5-2H-4-甲酰胺基吡唑-co-N-异丙基丙烯酰胺)在无氧PBS中发生直接电子转移的式电位(605mV)更接近漆酶活性中心的式电位(580mV),具有较快的异相电子转移速率(0.726s-1),较高的漆酶担载量(103.5mg/g)和固定漆酶比活力(1.68U/mg),较高的催化氧还原能力(氧还原起始电位820mV,在650mV时的催化峰电流为85.5μA)以及良好的重复使用性和长期使用性.     

Magnolol entrapped ultra-fine fibrous mats electrospun from poly(ethylene glycol)-<Emphasis Type="Italic">b</Emphasis>-poly(L-lactide) and <Emphasis Type="Italic">in vitro</Emphasis> release

Ultra-fine fibrous mats with magnolol entrapped have been prepared by electrospinning biodegradable copolymer poly(ethylene glycol) blocked poly(L-lactide). Drug entrapment was perfect which was confirmed by scanning electron microscopy and differential scanning calorimetry. According to in vitro drug release investigation by high performance liquid chromatography, it was found that fibers with 10%, 20% and 30% drug entrapped respect to polymer (mass ratio) presented dramatically different drug release behavior and degradation behavior under the effect of proteinase K. The reason may be that fibers with 10% drug entrapped was more easily affected by enzyme while, to some degree, magnolol in fibers with 20% and 30% entrapped prevented polymer from being degraded by enzyme.     

Fabrication of poly(ethylene glycol)‐based hydrogels entrapping enzyme‐immobilized silica nanoparticles

In this study, we immobilized enzymes by combining covalent surface immobilization and hydrogel entrapment. A model enzyme, glucose oxidase (GOX), was first covalently immobilized on the surface of silica nanoparticles (SNPs) via 3‐aminopropyltriethoxysilane (APTES), and the resultant SNP‐immobilized enzyme was physically entrapped within photopolymerized hydrogels prepared from two different molecular weights (MWs) (575 and 8000 Da) of poly(ethylene glycol)(PEG). The hydrogel entrapment resulted in a decrease in reaction rate and an increase in apparent K_m of SNP‐immobilized GOX, but these negative effects could be minimized by using hydrogel with a higher MW PEG, which provides higher water content and larger mesh size. The catalytic rate of the PEG 8000 hydrogel was about ten times faster than that of the PEG 575 hydrogel because of enhanced mass transfer. Long‐term stability test demonstrated that SNP‐immobilized GOX entrapped within hydrogel maintained more than 60% of its initial activity after a week, whereas non‐entrapped SNP‐immobilized GOX and entrapped GOX without SNP immobilization maintained less than 20% of their initial activity. Incorporation of SNPs into hydrogel enhanced the mechanical strength of the hydrogel six‐fold relative to bare hydrogels. Finally, a hydrogel microarray entrapping SNP‐immobilized GOX was fabricated using photolithography and successfully used for quantitative glucose detection. Copyright © 2009 John Wiley & Sons, Ltd.     

On the oxidation of N-methyl and N-benzylpyrimidin-2- and -4-ones by rabbit liver aldehyde oxidase

The presence of a methyl or benzyl group at N-1 or N-3 of 2- and 4-pyrimidone does not affect the site of oxidation by rabbit liver aldehyde oxidase. From all substrates studies only one product viz. the corresponding N-1 or N-3 substituted uracil has been obtained. The maximum rates of oxidation by free enzyme show an optimum in the pH range 6.5–7.8, which is little influenced by the site and the size of the N-substituent. Application of immobilized enzyme in small scale synthesis gives 1- or 3-R-uracils (R = methyl, benzyl) in 43–78% yield.     

Hydrogen Peroxide Sensor Based on Horseradish Peroxidase Combined with CaCO3 Microspheres and Gold Nanoparticles

Direct electrochemistry and electrocatalysis of horseradish peroxidase(HRP) were achieved by entrapping the enzyme between CaCO3 microspheres and gold nanoparticles through forming sandwich configuration (CaCO3-HRP-AuNPs). Polyanion, poly(styrene sulfonate)(PSS), was hybrid with CaCO3 microspheres to increase the surface negative charges for binding with HRP through electrostatic interaction. After the bioconjugate CaCO3 PSS-HRP was entrapped in chitosan based sol-gel(CS-GPTMS) film, HRP was encapsulated by in situ formation of an outer layer of AuNPs through electrochemical reduction of HAuCl4. The composite film containing AuNPs, CaCO3-PSS-HRP bioconjugates and CS-GPTMS can provide favorable microenvironment for HRP to perform direct electron transfer at glassy carbon electrode(GCE). HRP retained its bioelectrocatalytic activity and lead to sensitive and fast amperometric response for the determination of H2O2. H2O2 could be detected in a very wide linear range from 5.0×10–6 mol/L to 7.1×10–2 mol/L. The sandwich configuration of CaCO3-biomolecules-AuNPs could serve as a versatile platform for enzyme immobilization and biosensing.     

Localized Deposition of Chitosan as Matrix for Enzyme Immobilization

A local electrodeposition method was developed for chitosan by exploiting a pH gradient between a macroscopic electrode (the support) and a much smaller counter electrode. The deposition was confined either by using the direct mode of scanning electrochemical microscopy (SECM) or by performing the deposition in channels of a microfluidic network. The roughness was characterized by noncontact scanning force microscopy. The availability of amino groups at the surface of the microstructures was visualized after labeling by confocal laser scanning microscopy. The enzyme glucose oxidase could be entrapped during the electrochemical deposition and showed activity as seen by SECM images.     

Fluorescence-based adenylyl cyclase assay adaptable to high throughput screening

The second messenger cAMP has been implicated in numerous cellular processes such as glycogen metabolism, muscle contraction, learning and memory, and differentiation and development. Genetic evidence suggests that the enzyme that produces cAMP, adenylyl cyclase (AC), may be involved in pathogenesis in many of these cellular processes. In addition, these data suggest that membrane-bound ACs may be valuable targets for therapeutics to treat pathogenesis of these processes. The development of a robust real-time adenylyl cyclase assay that can be scalable to high-throughput screening could help in the development of novel therapeutics. Here we report a novel fluorescence-based cyclase assay using Bodipy FL GTPgammaS (BGTPgammaS). The fluorescence of the Bodipy moiety of BGTPgammaS was dramatically enhanced by incubation with the minimal catalytic core of wild-type-AC (wt-AC) and a mutant with decreased purine selectivity (mut-AC), in an AC activation-dependent manner. No increase in fluorescence was observed using Bodipy FL ATPgammaS (BATPgammaS) as substrate for either wt-AC or mut-AC. Using BGTPgammaS, forskolin, Gsalpha.GTPgammaS and the divalent cation Mn(2+) potently enhanced the rate of fluorescence increase in a concentration-dependent manner. The fluorescence enhancement of the Bodipy moiety was inhibited by known inhibitors of AC such as 2'deoxy,3'AMP and 2',5'-dideoxy-3'ATP. Furthermore, the fluorescence assay is adaptable to 96-well and 384-well multiplate format and is thus applicable to high throughput screening methodologies.     

Surfactant‐Stabilized Small Hydrogel Particles in Oil: Hosts for Remarkable Activation of Enzymes in Organic Solvents

Hydrogels of amino acid based cationic surfactant having C₁₆ tails were used to immobilize heme proteins and enzyme. These hydrogel‐entrapped proteins/enzyme showed remarkable activation when dispersed in organic solvent. The activation effect (ratio of the activity of the hydrogel‐entrapped enzyme in organic solvent to the activity of the native enzyme in water) of cytochrome c increased up to 350‐fold with varying protein and gelator concentration. Hydrogel‐entrapped hemoglobin and horseradish peroxidase (HRP) also showed markedly improved activity in organic solvent. Alteration in the structure of the gelator and its supramolecular arrangement showed that the protein immobilized within amphiphilic networks with larger interstitial space exhibited higher activation. This striking activation of hydrogel‐entrapped proteins stems from the following effects: 1) the hydrophilic domain of the amphiphilic networks facilitates accessibility of the enzyme to the water‐soluble substrate. 2) the surfactant, as an integral part of the amphiphilic network, assists in the formation of a distinct interface through which reactants and products are easily transferred between hydrophilic and hydrophobic domains. 3) Surfactant gelators help in the dispersion and stabilization of gel matrix into small particles in organic solvent, which enhances the overall surface area and results in improved mass transfer. The activation was dramatically improved up to 675‐fold in the presence of nongelating anionic surfactants that helped in disintegration of the gel into further smaller‐sized particles. Interestingly, hydrogel‐immobilized HRP exhibited about 2000‐fold higher activity in comparison to the activity of the suspended enzyme in toluene. Structural changes of the entrapped enzyme and the morphology of the matrix were investigated to understand the mechanism of this activation.     

新型吖啶-9-磺酰胺衍生物的合成及光谱学性质

在吖啶磺酰胺分子中引入杂环安替比林吸电性基团,合成了N-对甲基苯磺酰基-N-(4-安替比林)-10-甲基吖啶-9-磺酰胺三氟甲基磺酸鎓盐.最终产物与未甲基化的前体分别与模型化合物N-对甲基苯磺酰基-N-苯基-10-甲基吖啶-9-酰胺三氟甲基磺酸鎓盐及其前体的紫外-可见吸收光谱(UV)、荧光光谱(FL)进行比较.结果表明,引入杂环安替比林使吖啶磺酰胺的UV和FL谱发生了变化,尤其是FL谱的最大激发与发射峰的位置比相应的模型化合物大幅蓝移.最终产物及其前体的最大λex分别为268和274 nm; λem分别为321和327 nm.而模型化合物及前体最大λex分别为365和359 nm; λem分别为504和440 nm.H2O2引发的目标产物的化学发光(CL)在1.1 s完成;化学发光量子产率与模型化合物相当,是Luminol的化学发光效率的5.6倍.     

Stereoselective synthesis of novel benzoins catalysed by benzaldehyde lyase in a gel-stabilised two-phase system

Asymmetric benzoin condensation was performed using recombinant benzaldehyde lyase (BAL) from Pseudomonas fluorescens Biovar I. To enable the conversion of hydrophobic substrates, the enzyme was entrapped in polyvinyl alcohol and suspended in hexane. Compared to the reported application of the biocatalyst in an aqueous phase containing 20% DMSO, the productivity of the resulting gel-stabilised two-phase system was 3-fold better. The entrapment process had an efficiency of >90%, no enzyme or cofactor was lost during reaction or storage. The entrapped enzyme was stable in hexane for 1 week at 4 °C and more than 1 month at −20 °C. Without preceding optimisation the novel benzoins (R)-1,2-di(3-furanyl)-2-hydroxyethanone, (R)-2-hydroxy-1,2-di(3-thienyl) ethanone, (R)-1,2-di(4-ethoxyphenyl)-2-hydroxyethanone, (R)-1,2-di(3-ethoxyphenyl)-2-hydroxyethanone, (R)-2-hydroxy-1,2-di(3-tolyl)ethanone, and (R)-1,2-di(benzofuran-2-yl)-2-hydroxyethanone were prepared with yields up to 31.8% and enantiomeric excess >99%.     

Application of Calcium Alginate–Starch Entrapped Bitter Gourd (<Emphasis Type="Italic">Momordica charantia</Emphasis>) Peroxidase for the Removal of Colored Compounds from a Textile Effluent in Batch as well as in Continuous Reactor

Calcium alginate–starch entrapped bitter gourd peroxidase has been employed for the treatment of a textile industrial effluent in batch as well as in continuous reactor. The textile effluent was recalcitrant to decolorization by bitter gourd peroxidase; thus, its decolorization was examined in the presence of a redox mediator, 1.0 mM 1-hydroxybenzotriazole. Immobilized enzyme exhibited same pH and temperature optima for effluent decolorization as attained by soluble enzyme. Immobilized enzyme could effectively remove more than 70% of effluent color in a stirred batch process after 3 h of incubation. Entrapped bitter gourd peroxidase retained 59% effluent decolorization reusability even after its tenth repeated use. The two-reactor system containing calcium alginate–starch entrapped enzyme retained more than 50% textile effluent decolorization efficiency even after 2 months of its operation. The absorption spectra of the treated effluent exhibited a marked difference in the absorption at various wavelengths as compared to untreated effluent. The use of a two-reactor system containing immobilized enzyme and an adsorbent will be significantly successful for treating industrial effluents at large scale, and it will help in getting water free from aromatic pollutants.     

RELEASE OF IBUPROFEN FROM PEG-PLLA ELECTROSPUN FIBERS CONTAINING POLY(ETHYLENE GLYCOL)-b-POLY(α-HYDROXY OCTANOIC ACID) AS AN ADDITIVE

<正>Poly(α-hydroxy octanoic acid) was first used as an additive for the preparation of electrospun ultra-fine fibers of poly(ethylene glycol)-b-poly(L-lactide)(PEG-PLLA).Ibuprofen was loaded in the electrospun ultra-fine fibers.The results from environmental scanning electron microscopy(ESEM),wide angle X-ray diffraction(WAXD) and differential scanning calorimetry(DSC) demonstrated that ibuprofen could be perfectly entrapped in the fibers electrospun from PEG-PLLA usingα-hydroxy octanoic acid or PEG-b-poly(α-hydroxy octanoic acid)(PEG-PHOA) as additives.Compared with electrospun PEG-PLLA fibers which entrapped 20 wt%ibuprofen,the PEG-PLLA electrospun fibers containing PEG-PHOA exhibited integral and robust after 1 week incubated in 37℃,pH 7.4 phosphate buffer solution with 10μg/mL proteinase K.Compared with electrospun fibers without PEG-PHOA,the concentration of proteinase K in release media had less effect on the release rate of ibuprofen.An unique release profile was found from PEG-PLLA fiber after the incorporation of PEG-PHOA. Enzyme degradation experiments demonstrated that PEG-PHOA but notα-hydroxy octanoic acid monomer was the crucial factor for integrity maintenance of the electrospun fibers,which may be due to the enzyme degradation tolerance property of the PEG-PHOA polymer additive.     

Investigation of the origin of the glucose response in a glucose oxidase|polyaniline system

The origin of the signal seen in response to glucose in a polyaniline|glucose oxidase system is explored by immittance spectroscopy, by comparing data from an equivalent circuit model and the parameters obtained from a solution of the faradaic branch of the frequency dispersion for a coupled chemical—electrochemical reaction mechanism. It was shown that an RC subcircuit in the equivalent circuit model was sensitive to peroxide concentration, and the interaction of peroxide with polyaniline at potentials where it either oxidised or reduced the polyaniline was discussed. This information was used to compare the data obtained in a bulk and entrapped glucose oxidaselglucose system, and it was seen that the origin of the response could not be fully attributed to peroxide interaction in the latter case. Under anaerobic conditions with entrapped enzyme, it was proposed that a complex between the gluconolactone product of the enzyme reaction and the polymer leads to a more conducting polymer, with inherent charge compensation, and this results in the observed enhanced current signal.     

Entrapping enzyme in a functionalized nanoporous support

The enzyme organophosphorus hydrolase (OPH) was spontaneously entrapped in carboxylethyl- or aminopropyl-functionalized mesoporous silica with rigid, uniform open-pore geometry (30 nm). This approach yielded larger amounts of protein loading and much higher specific activity of the enzyme when compared to the unfunctionalized mesoporous silica and normal porous silica with the same pore size. When OPH was incubated with the functionalized mesoporous silica, protein molecules were sequestered in or excluded from the porous material, depending on electrostatic interaction with the charged functional groups. OPH entrapped in the organically functionalized nanopores showed an exceptional high immobilization efficiency of more than 200% and enhanced stability far exceeding that of the free enzyme in solution. The combination of high protein loading, high immobilization efficiency and stability is attributed to the large and uniform pore structure, and to the optimum environment introduced by the functional groups.