Biofunctionalizing nanofibers with carbohydrate blood group antigens

A rapid and simple method of biofunctionalising nylon, cellulose acetate, and polyvinyl butyral electrospun nanofibers with blood group glycans was achieved by preparing function‐spacer‐lipid constructs and simply contacting them to fibers with a piezo inkjet printer. A series of water dispersible amphipathic glycan‐spacer constructs were synthesized representing a range ABO and related blood group antigens. After immediate contact of the amphipathic glycan‐spacer constructs with nanofiber surfaces they self‐assembled and were detectable by enzyme immunoassays with high sensitivity and specificity.     

醋酸纤维素膜为基础的葡萄糖生物传感器的研制

用共价法将酶固定在醋酸纤维素膜上,方法简便易行,制造的酶膜稳定,比活力高。同时采用该方法制备了葡萄糖氧化酶酶膜,与氧电极组装成测定葡萄糖的生物传感器,线性范围为50~800mg／dl,仪器工作的最适pH为6．0,最适温度为40℃。将该膜与过氧化氢电极组装得到的传感器具有以下特性：线性范围为10~200mg／dl,最适pH为6．0,测定结果与酶试制盒有良好相关性。     

Core‐shell nanofibers: Integrating the bioactivity of gelatin and the mechanical property of polyvinyl alcohol

Coaxial electrospinning is used to fabricate nanofibers with gelatin in the shell and polyvinyl alcohol (PVA) in the core in order to derive mechanical strength from PVA and bioactivity from gelatin. At a 1:1 PVA/gelatin mass ratio, the core‐shell nanofiber scaffolds display a Young's modulus of 168.6 ± 36.5 MPa and a tensile strength of 5.42 ± 1.95 MPa, which are significantly higher than those of the scaffolds composed solely of gelatin or PVA. The Young's modulus and tensile strength of the core‐shell nanofibers are further improved by reducing the PVA/gelatin mass ratio from 1:1 to 1:3. The mechanical analysis of the core‐shell nanofibers suggests that the presence of the gelatin shell may improve the molecular alignment of the PVA core, transforming the semi‐crystalline, plastic PVA into a more crystallized, elastic PVA, and enhancing the mechanical properties of the core. Lastly, the PVA/gelatin core‐shell nanofibers possess cellular viability, proliferation, and adhesion similar to these of the gelatin nanofibers, and show significantly higher proliferation and adhesion than the PVA nanofibers. Taken together, the coaxial electrospinning of nanofibers with a core‐shell structure permits integration of the bioactivity of gelatin and the mechanical strength of PVA in single fibers. © 2013 Wiley Periodicals, Inc. Biopolymers 101: 336–346, 2014.     

Synthesis of PVA-CAP-based biomaterial in situ dispersed with Cu nanoparticles and carbon micro-nanofibers for antibiotic drug delivery applications

A novel pH-sensitive and water-soluble polyvinyl alcohol (PVA)-cellulose acetate phthalate (CAP) composite-based biomaterial was prepared, in which the multi-scale web of copper (Cu)-grown carbon micro-nanofibers (Cu-ACF/CNFs) was in situ dispersed during a synthesis stage. PVA-CAP and Cu-nanoparticles (NPs) were used as an encapsulating agent and nano-antibiotics, respectively. The web of Cu-ACF/CNF was prepared by growing CNFs on the activated carbon microfiber (ACF) substrate by chemical vapor deposition using Cu NPs as the catalyst. The novel step of the synthesis included esterification of polyvinyl acetate (PVAc) to produce a PVA gel to which the ball-milled Cu-ACF/CNF was blended at the incipience of the gel formation to produce the PVA-CAP-Cu-ACF/CNF metal-carbon-polymeric composite film. The in vitro dissolution tests revealed that the encapsulating polymeric composite was dispersible in water and its rate of dissolution was high at pH > 6.5. The antibacterial tests performed on the material demonstrated its effectiveness against both gram negative Escherichia coli and gram positive Staphylococcus aureus bacterial strains. The Hixson-Crowell kinetic model described the dissolution profiles of the material. The method of preparation is novel, simple, and environmentally friendly. The prepared biomaterial may be used in several biomedical applications, including wound healing and the controlled release of drugs in the antibiotic delivery system.     

Porcine blood cell separation by porous cellulose acetate membranes

Leukocytes were separated from whole porcine blood using laboratory prepared polymeric asymmetric porous membranes from cellulose acetate (CA) and by applying standard blood cell separation methods: centrifugation in a Ficoll solution gradient and in sucrose solution concentration gradient. Leukocytes, obtained by different separation methods were characterised by their quantity, type, viability and growth ability. Membranes prepared by a wet phase inversion process from different cellulose acetate/acetone/water and magnesium chlorate VII systems, were characterised according to: permeability to deionised water, surface morphology and by the determination of the flux of the permeate during the whole porcine blood separation. Cellulose acetate membranes prepared from 300 μm thick cast solution (14.8 wt% of cellulose acetate, 19.9 wt% of water, 2.3 wt% of Magnesium perchlorate, and 63.0 wt% of acetone), have separation characteristics comparable with the standard separation methods; in the dead-end mode filtration, 21.3% of leukocytes from porcine whole blood are separated. The leukocyte number in peripheral blood before separation was 450,000 ml^-1; the number passed through after was 95,000±6620. The main interest of the study was to introduce the CA membrane filters for the continus technological separation of the leukocyte/lymphocytes from animal (= porcine, bovine, horse..) blood. This revised version was published online in June 2006 with corrections to the Cover Date.     

Improved selectivity of microbial biosensor using membrane coating. Application to the analysis of ethanol during fermentation

A ferricyanide mediated microbial biosensor for ethanol detection was prepared by surface modification of a glassy carbon electrode. The selectivity of the whole Gluconobacter oxydans cell biosensor for ethanol determination was greatly enhanced by the size exclusion effect of a cellulose acetate (CA) membrane. The use of a CA membrane increased the ethanol to glucose sensitivity ratio by a factor of 58.2 and even the ethanol to glycerol sensitivity ratio by a factor of 7.5 compared with the use of a dialysis membrane. The biosensor provides rapid and sensitive detection of ethanol with a limit of detection of 0.85 microM (S/N=3). The selectivity of the biosensor toward alcohols was better compared to previously published enzyme biosensors based on alcohol oxidase or alcohol dehydrogenases. The biosensor was successfully used in an off-line monitoring of ethanol during batch fermentation by immobilized Saccharomyces cerevisiae cells with an initial glucose concentration of 200 g l(-1).     

Structure and mechanical properties of wet-spun fibers made from natural cellulose nanofibers

Cellulose nanofibers were prepared by TEMPO-mediated oxidation of wood pulp and tunicate cellulose. The cellulose nanofiber suspension in water was spun into an acetone coagulation bath. The spinning rate was varied from 0.1 to 100 m/min to align the nanofibers to the spun fibers. The fibers spun from the wood nanofibers had a hollow structure at spinning rates of >10 m/min, whereas the fibers spun from tunicate nanofibers were porous. Wide-angle X-ray diffraction analysis revealed that the wood and tunicate nanofibers were aligned to the fiber direction of the spun fibers at higher spinning rates. The wood spun fibers at 100 m/min had a Young's modulus of 23.6 GPa, tensile strength of 321 MPa, and elongation at break of 2.2%. The Young's modulus of the wood spun fibers increased with an increase in the spinning rate because of the nanofiber orientation effect.     

New results concerning the behavior of cellulose acetate in solutions and films by means of CD measurements

Cellulose acetate (DS = 2.45) was extensively investigated by Circular Dichroism (CD) in acetonitrile and dioxane. We found great differences between the CD spectra of a 1 wt % acetonitrile solution and the corresponding dioxane solution of cellulose acetate (CA) indicating that the macromolecules exist in those solutions in different molecular arrangements (e.g., persistence length, solvatation shell). The resulting morphologies could be transformed reversibly into each other, as we found by measuring the CA in mixtures of both solvents. Solid CA films show discernible CD spectra depending on the solvent they were evaporated from. In this way, we prepared solid films of the same polysaccharide owning different chiral properties. Furthermore, changes in the spectra occurred with increasing CA concentration. Basing upon our findings, some general statements concerning the polymer behavior of CA are possible. © 1999 John Wiley & Sons, Inc. Biopoly 50: 163–166, 1999     

Antimicrobial cellulose acetate nanofibers containing silver nanoparticles

It was found for the first time that polymer nanofibers containing Ag nanoparticles on their surface could be produced by UV irradiation of polymer nanofibers electrospun with small amounts of silver nitrate (AgNO₃). When the cellulose acetate (CA) nanofibers electrospun from CA solutions with 0.5 wt% of AgNO₃ were irradiated with UV light at 245 nm, Ag nanoparticles were predominantly generated on the surface of the CA nanofibers. The number and size of the Ag nanoparticles were continuously increased up to 240 min. The Ag⁺ ions and Ag clusters diffused and aggregated on the surface of the CA nanofibers during the UV irradiation. The Ag nanoparticles with an average size of 21 nm exhibited strong antimicrobial activity.     

Optical, bactericidal and water repellent properties of electrospun nano-composite membranes of cellulose acetate and ZnO

In this report, ZnO nanoparticles embedded cellulose acetate (CA) fibrous membrane with multifunctional properties have been prepared through electrospinning method. The morphology of the electrospun composite membrane was analyzed by Scanning Electron Microscope (SEM). It was found that the polymer concentration in the solution has a significant effect on the morphology of the fibers. The optical property of the sample was tested using Photo Luminescence (PL) spectra. There is no significant change in the emission features of cellulose acetate with the addition of ZnO. The anti-bacterial property of the sample was studied using disc diffusion method. The wettability of the pure and composite fibrous membrane was also studied by measuring the contact angle of water on the membrane. It was observed that the embedded ZnO in the CA was responsible for the hydrophobic nature of the surface.     

On-line microbial biosensing and fingerprinting of water pollutants

The potential for biosensors to contribute to on-line toxicity testing for monitoring of water quality is currently constrained both by the relevance of the biosensors available and the technology for biosensor delivery. This paper reports the use of novel slow release biosensor delivery for on-line monitoring instrumentation, with environmentally relevant bacteria for both simple toxicity testing and more complex toxicity fingerprinting of industrial effluents. The on-line toxicity test, using bioluminescence-based biosensors, proved to be as sensitive and reliable as the corresponding batch test, with comparable contaminant EC(50) values from both methods. Toxicity fingerprinting through the investigation of the kinetics (dose-response) and the dynamics (response with time) of the biosensor test response proved to be diagnostic of both effluent type and composition. Furthermore, the slow release of biosensors immobilised in a polyvinyl alcohol (PVA) matrix greatly improved biosensor delivery, did not affect the sensitivity of toxicity testing, and demonstrated great potential for inclusion in on-line monitoring instrumentation.     

Electrospun polylactic acid and polyvinyl alcohol fibers as efficient and stable nanomaterials for immobilization of lipases

Electrospinning was applied to create easy-to-handle and high-surface-area membranes from continuous nanofibers of polyvinyl alcohol (PVA) or polylactic acid (PLA). Lipase PS from Burkholderia cepacia and Lipase B from Candida antarctica (CaLB) could be immobilized effectively by adsorption onto the fibrous material as well as by entrapment within the electrospun nanofibers. The biocatalytic performance of the resulting membrane biocatalysts was evaluated in the kinetic resolution of racemic 1-phenylethanol (rac-1) and 1-phenylethyl acetate (rac-2). Fine dispersion of the enzymes in the polymer matrix and large surface area of the nanofibers resulted in an enormous increase in the activity of the membrane biocatalyst compared to the non-immobilized crude powder forms of the lipases. PLA as fiber-forming polymer for lipase immobilization performed better than PVA in all aspects. Recycling studies with the various forms of electrospun membrane biocatalysts in ten cycles of the acylation and hydrolysis reactions indicated excellent stability of this forms of immobilized lipases. PLA-entrapped lipases could preserve lipase activity and enantiomer selectivity much better than the PVA-entrapped forms. The electrospun membrane forms of CaLB showed high mechanical stability in the repeated acylations and hydrolyses than commercial forms of CaLB immobilized on polyacrylamide beads (Novozyme 435 and IMMCALB-T2-150).     

Desorption of Copper from Polyvinyl Alcohol‐Immobilized Seaweed Biomass

The desorption characteristics of copper on biomass of a marine macroalga, Sargassum baccularia, immobilized in polyvinyl alcohol (PVA) gel beads, were investigated using HCl eluting solutions. Both the extent and the rate of desorption were affected by the pH of the eluent. Nearly 91% of the copper initially adsorbed was released back into an HCl solution at pH 1.0 after 40 min of contact time when apparent desorption equilibrium was achieved. When the pH was raised to 2.0, about 81% of the bound copper was desorbed within 120 min of contact time. Apparent desorption rate constants were determined using first‐order desorption models. Very high concentrations of copper in the eluate could be obtained by using small amounts of the HCl eluent. However, this was achieved at the expense of the desorption efficiency. The PVA‐immobilized seaweed biomass beads could be regenerated with HCl solution at pH 1.0 or 2.0 in multiple cycles of copper biosorption‐desorption. Following desorption at pH 1.0 in the first cycle, about 55% of the biosorption capacity of the virgin biomass could be reused in subsequent cycles; in the case of desorption at pH 2.0, about 67% of the original uptake capacity was reusable.     

Vitrification enhancement by synthetic ice blocking agents

Small concentrations of the synthetic polymer polyvinyl alcohol (PVA) were found to inhibit formation of ice in water/cryoprotectant solutions. Ice inhibition improved with decreasing molecular weight. A PVA copolymer of molecular weight 2 kDa consisting of 20% vinyl acetate was found to be particularly effective. PVA copolymer concentrations of 0.001, 0.01, 0.1, and 1% w/w decreased the concentration of glycerol required to vitrify in a 10-ml volume by 1, 3, 4, and 5% w/w, respectively. Dimethyl sulfoxide concentrations required for vitrification were also reduced by 1, 2, 2, and 3% w/w, respectively. Crystallization of ice on borosilicate glass in contact with cryoprotectant solutions was inhibited by only 1 ppm of PVA copolymer. Devitrification of ethylene glycol solutions was also strongly inhibited by PVA copolymer. Visual observation and differential scanning calorimeter data suggest that PVA blocks ice primarily by inhibition of heterogeneous nucleation. PVA thus appears to preferentially bind and inactivate heterogeneous nucleators and/or nascent ice crystals in a manner similar to that of natural antifreeze proteins found in cold-hardy fish and insects. Synthetic PVA-derived ice blocking agents can be produced much less expensively than antifreeze proteins, offering new opportunities for improving cryopreservation by vitrification.     

白蚁纤维素粉饵料成型技术研究

为研究白蚁饵料成型工艺,比较了9种胶黏剂对白蚁纤维素饵料成型效果、耐水性能以及对白蚁取食的影响。结果表明:20%、40%剂量糊精;50%、100%剂量三聚氰胺甲醛树脂,10%、20%、40%田菁胶、卡拉胶、壳聚糖、明胶;10%、50%、100%聚乙烯醇、硅酸钠对微晶纤维素的成型效果较好,经上述剂量胶黏剂处理后,纤维素饵块的邵氏硬度(HD)极显著高于对照。耐水性能试验至第30天时,50%聚乙烯醇、100%聚乙烯醇、100%三聚氰胺甲醛树脂处理的纤维素饵块的溃散程度指数分别为1.33、1.00、2.00,其余饵块的溃散程度指数均达3级。生测结果显示,在7 d的室内强迫取食试验中,白蚁对50%聚乙烯醇、100%聚乙烯醇、100%三聚氰胺甲醛树脂处理的块状纤维素饵料的取食率均极显著低于对照,说明饵块中添加的上述胶黏剂对白蚁的取食具有一定的影响。综上,50%聚乙烯醇、100%聚乙烯醇、100%三聚氰胺甲醛树脂适用于白蚁纤维素饵料成型,但若想获得白蚁喜食的饵块仍需对配方做进一步的优化。     

Polyvinyl alcohol--trypsin as a catalyst for amino acid ester synthesis in organic media

The bovine trypsin-catalyzed synthesis of N-alpha-benzoyl-DL-arginine esters from N-benzoyl-DL-arginine were studied in various organic solvents. Trypsin was immobilized to polyvinyl alcohol (PVA) by adsorption from its aqueous solutions. Immobilized enzyme showed higher catalytic activities than free enzyme for amino acid esterification in ethanol. The yield of ester is strongly dependent upon the PVA/trypsin ratio and water content in the reaction medium. The rate and equilibrium constant of the ester formation reaction are also dependent on water content.     

Enhanced stability of immobilized keratinolytic protease on electrospun nanofibers

Abstract

Feathers from poultry industries are considered a major pollutant and its degradation is a challenging problem due to its recalcitrant nature. The high cost of energy and loss of essential amino acids by conventional methods have paved a way for an environmentally benign approach using microbial keratinolytic proteases. The widespread application of keratinolytic proteases is limited due to autolysis and denaturation of the enzyme upon storage. Immobilization overcomes these disadvantages by adsorbing the enzyme onto a solid support. Recently, electrospun nanofibers have been used due to their increased surface area and porous structure. The biocompatible and hydrophilic polyvinyl alcohol (PVA) has been blended with biodegradable chitosan for immobilization in electrospinning. The present study focuses on feather degradation by immobilized keratinolytic proteases on electrospun nanofibers. The keratinolytic protease production was enhanced by using a media containing hydrolyzed feather under optimized conditions. The immobilized keratinolytic protease on electrospun PVA chitosan (PVA-Ch) nanofibers (100–150?nm diameter) degraded the chicken feathers with 88% efficiency at the end of 72?hr.     

Modified coaxial electrospinning for the preparation of high-quality ketoprofen-loaded cellulose acetate nanofibers

This study investigates the use of a modified coaxial electrospinning process in the production of drug-loaded cellulose acetate (CA) nanofibers. With CA employed as a filament-forming matrix and ketoprofen (KET) as an active pharmaceutical ingredient, modified coaxial processes using sheath fluids comprising only mixed solvents were undertaken. With a sheath-to-core flow rate ratio of 0.2:1, the nanofibers prepared from the coaxial process had a smaller average diameter, narrower size distribution, more uniform structures, and smoother surface morphologies than those generated from single fluid electrospinning. In addition, the coaxial fibers provided a better zero-order drug release profile. The use of a sheath solvent means that the core jet is subjected to electrical drawing for a longer period, facilitating homogeneous core jet solidification and retarding the formation of wrinkles on the surface of the nanofibers. This modified coaxial electrospinning protocol allows the systematic fabrication of functional polymer nanofibers with improved quality.     

Electrospun cellulose acetate nanofibers: The present status and gamut of biotechnological applications

Cellulose acetate (CA) has been a material of choice for spectrum of utilities across different domains ranging from high absorbing diapers to membrane filters. Electrospinning has conferred a whole new perspective to polymeric materials including CA in the context of multifarious applications across myriad of niches. In the present review, we try to bring out the recent trend (focused over last five years' progress) of research on electrospun CA fibers of nanoscale regime in the context of developmental strategies of their blends and nanocomposites for advanced applications. In the realm of biotechnology, electrospun CA fibers have found applications in biomolecule immobilization, tissue engineering, bio-sensing, nutraceutical delivery, bioseparation, crop protection, bioremediation and in the development of anti-counterfeiting and pH sensitive material, photocatalytic self-cleaning textile, temperature-adaptable fabric, and antimicrobial mats, amongst others. The present review discusses these diverse applications of electrospun CA nanofibers.     

The dependence of pyrolysis behavior on the crystal state of cellulose

Cellulose was dissolved in the ionic liquid 1-butyl-3-methylimidazolium chloride, and then regenerated from the solution by using different methods. Thermogravimetric analysis (TG)-Differential Scanning Calorimetry (DSC), X-ray diffraction (XRD), and Scanning Electron Microscopy (SEM) were used to characterize the structure of the original and regenerated cellulose. Cellulose II or amorphous cellulose was obtained by pouring cellulose solution into de-ioned water or pouring de-ioned water into cellulose solution, respectively. The pyrolysis behavior of original and regenerated cellulose was tested in a fixed bed reactor. The pyrolysis of cellulose I gave high content of furfural and 1,4;3,6-dianhydro-alpha-d-glucopyranose in the liquid products, and cellulose II and amorphous cellulose gave high content of furfural and 5-(hydroxymethyl)-2-furancarboxyaldehyde, with 5-(hydroxymethyl)-2-furancarboxyaldehyde the highest for cellulose II and furfural the highest for amorphous cellulose. And the treatment of the cellulose samples favored the removal of oxygen in the form of CO₂ in the pyrolysis.