Control release of lactate dehydrogenase encapsulated in poly (vinyl alcohol) nanofibers via electrospinning

Sustained release of lactate dehydrogenase (LDH, EC 1.1.1.27) from electrospun poly (vinyl alcohol) (PVA) nanofibers was successfully achieved using the coaxial electrospinning technique. The presence of the encapsulated enzyme in the nanofibers was confirmed by infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Scanning electron microscopy (SEM) was used to evaluate the morphology and diameter of the nanofibers. The conversion of lactate to pyruvate by LDH coupling with the reduction of the cofactor nicotinamide adenine dinucleotide (NAD⁺) to dihydronicotinamide adenine dinucleotide (NADH) produces an increment in the ultraviolet absorption (UV) at 340 nm. This change in the UV absorbance was used to follow the release kinetic of LDH from the PVA nanofibers and also as a measure to evaluate the residual enzymatic catalytic function. Most of the encapsulated LDH enzyme was released in a sustained manner from the PVA nanofibers within a period of 1 month.     

Improved cellular response on multiwalled carbon nanotube-incorporated electrospun polyvinyl alcohol/chitosan nanofibrous scaffolds

We report the fabrication of multiwalled carbon nanotube (MWCNT)-incorporated electrospun polyvinyl alcohol (PVA)/chitosan (CS) nanofibers with improved cellular response for potential tissue engineering applications. In this study, smooth and uniform PVA/CS and PVA/CS/MWCNTs nanofibers with water stability were formed by electrospinning, followed by crosslinking with glutaraldehyde vapor. The morphology, structure, and mechanical properties of the formed electrospun fibrous mats were characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, and mechanical testing, respectively. We showed that the incorporation of MWCNTs did not appreciably affect the morphology of the PVA/CS nanofibers; importantly the protein adsorption ability of the nanofibers was significantly improved. In vitro cell culture of mouse fibroblasts (L929) seeded onto the electrospun scaffolds showed that the incorporation of MWCNTs into the PVA/CS nanofibers significantly promoted cell proliferation. Results from this study hence suggest that MWCNT-incorporated PVA/CS nanofibrous scaffolds with small diameters (around 160 nm) and high porosity can mimic the natural extracellular matrix well, and potentially provide many possibilities for applications in the fields of tissue engineering and regenerative medicine.     

Electrospinning Process of Thermo-sensitive Poly(N-isopropylacrylamide) /poly (2-acrylamido-2-methylpropanesulfonic acid) Nanofibers

Poly (N-isopropylacrylamide)/poly (2-acrylamido-2-methylpropanesulfonic acid) (PNIPAAm/PAMPS) nanofibers was prepared using the electrospinning technique. The electrospinning process parameters such as solution concentration, voltage, receiver distance and flow rate were determined by the orthogonal experiments. The appropriate electrospinning parameters were 7.0% of solution concentration, 10.0 kV of voltage, 20 cm of distance and 3.1 μL·min^?1 of flow rate, respectively. The major factor affecting the nanofibers diameter was the solution concentration and the diameter increased with the solution concentration. The Fourier-transform infrared spectroscopy (FTIR) was conducted to characterize the structure of the components for electrospinning. Scanning electron microscopy (SEM) was taken to observe the morphology, and the contact angle (CA) measuring was carried out to determine the wettability of the nanofibers with temperatures. The results of SEM observation showed that the surfaces of nanofibers were smooth with uniform fibrous diameters and without the formation of beads. The CA detections showed that the electrospun PNIPAAm/PAMPS nanofibers exhibited thermo-sensitivity of hydrophilicity at 20°C and hydrophobicity at 40°C.     

Carbendazim‐loaded electrospun poly(vinyl alcohol) fiber mats and release characteristics of carbendazim therefrom

Ultra‐fine poly(vinyl alcohol) (PVA) electrospun fiber mats containing carbendazim were successfully fabricated by electrospinning from the neat PVA solution containing carbendazim in various amounts based on the weight of PVA. The morphological appearance of both the neat and the carbendazim‐loaded electrospun PVA fibers were smooth and the incorporation of carbendazim in the neat PVA solution did not affect the morphology of the resulting fibers. The average diameters of the neat and the carbendazim‐loaded electrospun PVA fibers ranged between 155 and 160 nm. The chemical integrity of the as‐loaded carbendazim in the carbendazim‐loaded electrospun PVA fiber mats was intact as verified by the ¹H‐nuclear magnetic resonance spectroscopy. Thermal properties of the carbendazim‐loaded electrospun PVA fiber mats were analyzed by differential scanning calorimetry and thermogravimetric analysis. The release characteristics of the carbendazim‐loaded electrospun PVA mats were investigated by the total immersion method in distilled water at 30°C. The carbendazim‐loaded electrospun PVA mats exhibited greater amount of carbendazim released than the carbendazim‐loaded as‐cast films. Copyright © 2010 John Wiley & Sons, Ltd.     

改性海藻酸钠聚集行为对电纺纳米纤维形貌的影响

以过硫酸钾(KPS)为引发剂, 采用双丙酮丙烯酰胺(DAA)对海藻酸钠(SA)进行改性, 制备了海藻酸钠-聚双丙酮丙烯酰胺两亲性共聚物(SA-PDAA). 将SA-PDAA与聚乙烯醇(PVA)复配, 并进行静电纺丝, 制得SA-PDAA/PVA电纺纳米纤维. 通过红外光谱、 差示扫描量热和荧光光谱表征了SA-PDAA的结构和性能, 通过黏度仪、 表面张力仪和电导率仪测试了SA-PDAA纺丝液的物理性能, 用扫描电子显微镜表征了SA-PDAA/PVA电纺纳米纤维的形貌, 考察了SA-PDAA/PVA电纺纳米纤维的释药性能. 结果表明, DAA接枝到SA分子链上, SA-PDAA的临界聚集浓度为0.072 g/L, SA-PDAA具有良好的两亲性, SA-PDAA/PVA电纺纳米纤维具有均一的形貌. 改性后的SA可以有效地减缓药物释放速度, 提高SA-PDAA/PVA电纺纳米纤维的缓释性能.     

Influence of solvents properties on morphology of electrospun polyurethane nanofiber mats

Segmented polyurethane (SPU) nanofiber mats were prepared by electrospinning technique using the combination of four different solvents viz. tetrahydrofuran, N,N′‐dimethyl formamide, N,N′‐dimethyl acetamide, and dimethyl sulfoxide. Morphology of the electrospun nanofibers was examined by field emission scanning electron microscope. Experimental results revealed that the morphologies of polyurethane nanofiber mats have been changed significantly with the solvent selection for the electrospinning. It was observed that the diameters and morphology of the SPU nanofibers were influenced greatly by the use of combination of solvents. The uniform polyurethane nanofibers without beads or curls could be prepared by electrospinning through the selection of combination of good conductive and good volatile solvent viz. 7.5 wt/v% of SPU in N,N′‐dimethyl formamide/tetrahydrofuran (30 : 70 v/v) solutions at 20 kV applied voltages and volume flow rate of 1 ml/min. On the basis of the results obtained from this investigation, it has been established that solvent selection is one of the driving factors for controlling the morphology of the polyurethane electrospun nanofiber mats. The well‐controlled morphology of electrospun polyurethane nanofiber mats could be useful for many potential industrial applications such as in biomedical, smart textiles, nanofiltration, and sensors. Copyright © 2013 John Wiley & Sons, Ltd.     

二氧化硅/聚乙烯醇杂化电纺纤维膜的制备与结构形态

用溶胶-凝胶(Sol-Gel)法制备了不同二氧化硅含量的PVA/SiO2杂化纺丝液,将其电纺成纤维膜.XRD结果表明,杂化电纺纤维膜的结晶度较纯PVA电纺纤维膜小;FTIR证实了PVA的羟基与正硅酸乙酯水解后的羟基发生了缩合反应,杂化电纺纤维膜是以网络结构形式相结合的;FESEM表明,PVA/SiO2质量比为4∶1时,纤维光滑,分散比较均匀.随着二氧化硅含量的增加,纤维直径变细,纺锤形珠节结构增多.加入金属盐NaCl和MgCl2后,纤维直径变细,圆形珠节增多.从理论上分析了纤维膜结构形态的形成机理.     

Electrospun poly(aniline‐co‐ethyl 3‐aminobenzoate)/poly(lactic acid) nanofibers and their potential in biomedical applications

Poly(aniline‐co‐ethyl 3‐aminobenzoate) (3EABPANI) copolymer was blended with poly(lactic acid) (PLA) and co‐electrospun into nanofibers to investigate its potential in biomedical applications. The relationship between electrospinning parameters and fiber diameter has been investigated. The mechanical and electrical properties of electrospun 3EABPANI‐PLA nanofibers were also evaluated. To assess cell morphology and biocompatibility, nanofibrous mats of pure PLA and 3EABPANI‐PLA were deposited on glass substrates and the proliferation of COS‐1 fibroblast cells on the nanofibrous polymer surfaces determined. The nanofibrous 3EABPANI‐PLA blends were easily fabricated by electrospinning and gave enhanced mammalian cell growth, antioxidant and antimicrobial capabilities, and electrical conductivity. These results suggest that 3EABPANI‐PLA nanofibrous blends might provide a novel bioactive conductive material for biomedical applications. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011.     

Preparation,characterization, and properties of nanofibers based on poly(vinylidene fluoride) and polyhedral oligomeric silsesquioxane

Nanostructered nanofibers based on poly(vinylidene fluoride) (PVDF) and polyhedral oligomeric silsesquioxane (POSS) have been prepared by electrospinning process. The starting solutions were prepared by dissolving both the system components in the mixture N,N‐dimethylacetamide/acetone. The characteristics of the fiber prepared, studied by scanning electron microscopy, atomic force microscopy, and wide angle X‐ray diffraction, have been compared with those of PVDF fibers. Morphological characterization has demonstrated the possibility to obtain defect‐free PVDF/POSS nanofibers by properly choosing the electrospinning conditions, such as voltage, polymer concentration, humidity, etc. Conversely, in the case of fibers based on the neat polymer, it was not possible to attain the complete elimination of beads in the electrospun nanofibers. The different behavior of the two types of solutions has been ascribed to silsesquioxane molecules, which, without influencing the solution viscosity or conductivity, favor the formation of uniform structures by decreasing the system surface tension. Concerning POSS distribution in the fibers, the morphological characterization of the electrospun films has shown a submicrometric dispersion of the silsesquioxane. It is relevant to underline that cast films, prepared by the same solutions, have been found to be characterized by POSS aggregation, thus demonstrating a scarce affinity between the two‐system components. Indeed, the peculiar solvent evaporation of the electrospun solution, which is much faster than that occurring during the cast process, prevents POSS aggregation, thus leading to the formation of nanofibers characterized by a silsesquioxane dispersion similar to that present in solution. Finally, the presence of POSS improves the electrospun film mechanical properties. Copyright © 2011 John Wiley & Sons, Ltd.     

Effect of pullulan/poly(vinyl alcohol) blend system on the montmorillonite structure with property characterization of electrospun pullulan/poly(vinyl alcohol)/montmorillonite nanofibers

Nanofibers of the composite of pullulan (PULL), poly(vinyl alcohol) (PVA), and montmorillonite clay (MMT) were prepared using electrospinning method in aqueous solutions. Pullulan is an interesting natural polymer for many of its merits and good properties. Because of biocompatibility and non-toxicity of PVA, it could be used in numerous fields. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR), X-ray diffraction (XRD), and thermal gravimetric analysis (TGA) were done to characterize the PULL/PVA/MMT nanofibers morphology and properties. XRD patterns and FTIR data demonstrated that there were good interactions between PULL and PVA caused by possibly hydrogen bonds. Moreover, XRD data and TEM images indicated that intercalated and exfoliated MMT nanoplatelets can be obtained within the PULL/PVA/MMT nanofibers depending on the PULL/PVA blend ratios. Furthermore, the thermal stability and mechanical property (tensile strength) of PULL/PVA/MMT nanofibers could be enhanced more by exfoliated MMT nanoplatelets than intercalated structures of that nanoplatelets.     

Controlled release of doxorubicin from electrospun MWCNTs/PLGA hybrid nanofibers

In this study, multiwalled carbon nanotubes (MWCNTs) were used to encapsulate a model anticancer drug, doxorubicin (Dox). Then, the drug-loaded MWCNTs (Dox/MWCNTs) with an optimized drug encapsulation percentage were mixed with poly(lactide-co-glycolide) (PLGA) polymer solution for subsequent electrospinning to form drug-loaded composite nanofibrous mats. The structure, morphology, and mechanical properties of the formed electrospun Dox/PLGA, MWCNTs/PLGA, and Dox/MWCNTs/PLGA composite nanofibrous mats were characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy, and tensile testing. In vitro viability assay and SEM morphology observation of mouse fibroblast cells cultured onto the MWCNTs/PLGA fibrous scaffolds demonstrate that the developed MWCNTs/PLGA composite nanofibers are cytocompatible. The incorporation of Dox-loaded MWCNTs within the PLGA nanofibers is able to improve the mechanical durability and maintain the three-dimensional structure of the nanofibrous mats. More importantly, our results indicate that this double-container drug delivery system (both PLGA polymer and MWCNTs are drug carriers) is beneficial to avoid the burst release of the drug and able to release the antitumor drug Dox in a sustained manner for 42 days. The developed composite electrospun nanofibrous drug delivery system may be used as therapeutic scaffold materials for post-operative local chemotherapy.     

Electrospun PVA Nanofibrous Membranes Reinforced with Silver Nanoparticles Impregnated Cellulosic Fibers: Morphology and Antibacterial Property

To enhance the mechanical and antibacterial properties of silver nanoparticle impregnated cellulosic fibers, carboxy-cellulose nanocrystals(CCNs) were grafted with chitooligosaccharide(COS), which was used as a stabilizer for silver nanoparticles (AgNPs). Nanofibrous membranes reinforced with silver nanoparticle impregnated cellulosic fibers(CCN-COS-AgNP) were prepared via electrospinning using polyvinyl alcohol(PVA) as a matrix. The effects of CCN-COS-AgNP contents on the morphology, surface composition, mechanical properties, and antibacterial performances of the prepared CCN-COS-AgNP/PVA membranes were examined. The addition of CCN-COS-AgNP certainly improved the mechanical properties and antibacterial performances of the PVA nanofibers. The tensile strength was significantly increased from 4.40 MPa to 8.60 MPa when 8% CCN-COS-AgNP(mass ratio) was introduced. When 10%(mass ratio) CCN-COS-AgNP was added, the nanofibers showed an excellent antibacterial activity for S. aureus(Staphylococcus aureus) and E. coli(Escherichia coli), with the maximum inhibition zones of 2.30 and 1.60 cm, respectively. Moreover, the 2%(mass ratio) CCN-COS-AgNP/PVA fibrous membrane showed 126% cell viability for mg63 human osteoblasts. The electrospun PVA membrane has great potential application in biomedical field.     

Thermal,morphological, and mechanical properties of ethyl vanillin immobilized in polyvinyl alcohol by electrospinning process

In this study, polyvinyl alcohol (PVA) nanofibers with ethyl vanillin as an active compound were prepared using electrospinning technique. The final products of electrospinning process were in the form of nanofibers films. PVA/ethyl vanillin nanofibers, having fibers diameters in the range 100–1700 nm, were successfully electrospun from ethanol/water mixture of PVA and ethyl vanillin. The effects of immobilization process on ethyl vanillin thermal properties were investigated by differential scanning calorimetry (DSC). The results of DSC showed significant influence of immobilization process on thermal properties of ethyl vanillin. It was noticed that melting point of immobilized ethyl vanillin was lower (~55 °C) compared to free flavor (~77 °C). Our results showed that films based on PVA/ethyl vanillin nanofibers are mechanically stable.     

Preparation of Polymer Nanofibers Containing Silver Nanoparticles by Using Poly(N‐vinylpyrrolidone)

Summary: Poly(N‐vinylpyrrolidone) (PVP) was used in two methods to prepare polymer nanofibers containing Ag nanoparticles. The first method involved electrospinning the PVP nanofibers containing Ag nanoparticles directly from the PVP solutions containing the Ag nanoparticles. N,N‐Dimethylformamide was used as a solvent for the PVP as well as a reducing agent for the Ag⁺ ions in the PVP solutions. In the second method, poly(vinyl alcohol) (PVA) aqueous solutions were electrospun with 5 wt.‐% of the PVP containing Ag nanoparticles. The Ag nanoparticles were evenly distributed in the PVA nanofibers. PVP containing Ag nanoparticles could be used to introduce Ag nanoparticles to other polymer nanofibers that are miscible with PVP.

TEM image of a PVA nanofiber electrospun with 5 wt.‐% of the PVP containing Ag nanoparticles.     

Hybrid silica-PVA nanofibers via sol-gel electrospinning

We report on the synthesis of poly(vinyl alcohol) (PVA)-silica hybrid nanofibers via sol-gel electrospinning. Silica is synthesized through acid catalysis of a silica precursor (tetraethyl orthosilicate (TEOS) in ethanol-water), and fibers are obtained by electrospinning a mixture of the silica precursor solution and aqueous PVA. A systematic investigation on how the amount of TEOS, the silica-PVA ratio, the aging time of the silica precursor mixture, and the solution rheology influence the fiber morphology is undertaken and reveals a composition window in which defect-free hybrid nanofibers with diameters as small as 150 nm are obtained. When soaked overnight in water, the hybrid fibers remain intact, essentially maintaining their morphology, even though PVA is soluble in water. We believe that mixing of the silica precursor and PVA in solution initiates the participation of the silica precursor in cross-linking of PVA so that its -OH group becomes unavailable for hydrogen bonding with water. FTIR analysis of the hybrids confirms the disappearance of the -OH peak typically shown by PVA, while formation of a bond between PVA and silica is indicated by the Si-O-C peak in the spectra of all the hybrids. The ability to form cross-linked nanofibers of PVA using thermally stable and relatively inert silica could broaden the scope of use of these materials in various technologies.     

Electrospinning of ultra-thin polymer fibers

The electrospinning technique was used to spin ultra-thin fibers from several polymer/solvent systems. The diameter of the electrospun fibers ranged from 16 nm to 2 μm. The morphology of these fibers was investigated with an atomic force microscope (AFM) and an optical microscope. Polyethylene oxide) (PEO) dissolved in water or chloroform was studied in greater detail. PEO fibers spun from aqueous solution show a “beads on a string” morphology. An AFM study showed that the surface of these fibers is highly ordered. The “beads on a string” morphology can be avoided if PEO is spun from solution in chloroform; the resulting fibers show a lamellar morphology. Polyvinylalcohol (PVA) dissolved in water and cellulose acetate dissolved in acetone were additional polymer/solvent systems which were investigated. Furthermore, the electrospinning process was studied: different experimental lay-outs were tested, electrostatic fields were simulated, and voltage - current characteristics of the electrospinning process were recorded.     

Development and characterization of electrospun cellulose acetate nanofibers modified by cationic surfactant

Polymeric electrospun nanofibers have been gaining notoriety in the same way as their industrial applications, since the manufacturing of this type of material is simple and low-costed. In order to obtain fibrous polymeric material with small diameters and with reduced beads formation, a 2⁴ factorial experiment with triplicate at center point was performed. Cellulose acetate (CA) and cationic cetylpyridinium bromide (CPB) surfactant nanofibers were made using a homemade electrospinning apparatus. The assessed inputs were as follows: CA%, CPB%, flow rate, and applied voltage. From the analysis of the response surface methodology and scanning electron microscope (SEM), the optimal concentrations of CA and CPB for producing nanofibers were 21 w/v-% and 0.5 w/v-%, respectively, using a flow rate of 0.7 mL h⁻¹ and applied voltage of 18 kV. Fibers mats morphology shows average diameter of 0.2 μm and 7 nm pore size, as well as it was found that the single fiber unit presented nanoheterogeneity. Mechanical resistance of 2.70 MPa was obtained in the tensile strength test. The modification of CA by the addition of surfactant attributed better thermal and mechanical resistances to the nanofibers without, however, affecting their biodegradability and water resistance properties. The morphological characteristics of the newly obtained CA/CPB nanofibers combined with mechanical resistance provided subsidies to suggest that the as-obtained material presents potential to be applied as an air filter.     

Atmospheric plasma treatment of pre‐electrospinning polymer solution: A feasible method to improve electrospinnability

The electrospinnability of polyethylene oxide (PEO) was manipulated by atmospheric plasma treatment of pre‐electrospinning solutions. Conductivity, viscosity, and surface tension of PEO solutions increased after plasma treatment, and the plasma effect remained longer when the solution concentrate increased. Both untreated and treated solutions were then electrospun, and the morphology of the resultant nanofibers was observed by SEM. Atmospheric plasma treatment improved the electrospinnability of PEO solutions and led to less beads and finer diameter distribution in the resultant nanofibers. Additionally, plasma treatment of the pre‐electrospinning solutions affected the crystal structure of resultant nanofibers. These results suggest that atmospheric plasma treatment is a feasible approach to improve the electrospinnability of polymer solutions and can used to control the structure of electrospun nanofibers. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

Fabrication of poly(vinyl alcohol)‐graphene quantum dots coated with poly(3,4‐ethylenedioxythiophene) for supercapacitor

Conducting nanofiber composed of poly(vinyl alcohol) (PVA), graphene quantum dots (GQDs) and poly(3,4‐ethylenedioxythiophene) (PEDOT) was prepared for symmetrical supercapacitor through electrospinning and electropolymerization techniques. The formation of PVA nanofibers with the addition of GQDs was excellently prepared with the average diameter of 55.66 ± 27 nm. Field emission scanning electron microscopy images revealed that cauliflower‐like structure of PEDOT was successfully coated on PVA‐GQD electrospun nanofibers. PVA‐GQD/PEDOT nanocomposite exhibited the highest specific capacitance of 291.86 F/g compared with PVA/PEDOT (220.73 F/g) and PEDOT (161.48 F/g). PVA‐GQD/PEDOT also demonstrated a high specific energy and specific power of 16.95 and 984.48 W/kg, respectively, at 2.0 A/g current density. PVA‐GQD/PEDOT exhibited the lowest resistance of charge transfer (R_ct) and equivalent series resistance compared with PEDOT and PVA/PEDOT, indicating that the fast ion diffusion between the electrode and electrolyte interface. PVA‐GQD/PEDOT nanocomposite also showed an excellent stability with retention of 98% after 1000 cycles. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 50–58     

Fragrance encapsulation in polymeric matrices by emulsion electrospinning

We present the successful application of emulsion electrospinning for the encapsulation of a model for highly volatile fragrances, namely (R)-(+)-limonene in a poly(vinyl alcohol) (PVA) fibrous matrix. The influence of the emulsion formulation and of its colloidal properties on the fiber morphology, as well as on the limonene encapsulation efficiency, is described. The release profile of the fragrance from the electrospun nanofibers over a fifteen days range shows that this type of nanofibrous matrices with a high fragrance loading capacity is of great potential for applications in various fields, such as cosmetics or food packaging.