Mohamed H. El-Newehy

Wound-dressing materials with antibacterial activity from electrospun polyurethane-dextran nanofiber mats containing ciprofloxacin HCl.

Dextran is a versatile biomacromolecule for preparing electrospun nanofibrous membranes by blending with either water-soluble bioactive agents or hydrophobic biodegradable polymers for biomedical applications. In this study, an antibacterial electrospun scaffold was prepared by electrospinning of a solution composed of dextran, polyurethane (PU) and ciprofloxacin HCl (CipHCl) drug. The obtained nanofiber mats have good morphology. The mats were characterized by various analytical techniques. The interaction parameters between fibroblasts and the PU-dextran and PU-dextran-drug scaffolds such as viability, proliferation, and attachment were investigated. The results indicated that the cells interacted favorably with the scaffolds especially the drug-containing one. Moreover, the composite mat showed good bactericidal activity against both of Gram-positive and Gram-negative bacteria. Overall, our results conclude that the introduced scaffold might be an ideal biomaterial for wound dressing applications.

Controlled release of bone morphogenetic protein 2 and dexamethasone loaded in core-shell PLLACL-collagen fibers for use in bone tissue engineering.

Electrospun nanofibers mimic the native extracellular matrix of bone and have generated considerable interest in bone tissue regeneration. The aim of this study was to fabricate novel poly(l-lactide-co-caprolactone) (PLLACL), PLLACL/collagen nanofibers blended with bone morphogenetic protein 2 (BMP2) and dexamethasone (DEX) for controlled release during bone tissue engineering (BTE). The morphology, surface hydrophilicity, and mechanical properties of the PLLACL/collagen nanofibrous mats were analyzed by scanning electron microscopy and water contact angle and mechanical stability determination. The performance of the scaffolds was investigated in terms of the viability and morphology of human mesenchymal stromal cells (hMSC) on the nanofibrous mats. BMP2 and DEX were successfully incorporated into PLLACL/collagen nanofibers by means of blending or coaxial electrospinning and the PLLACL/collagen blended fibers proved useful for hMSC culture. Release of the two growth factors from PLLACL/collagen nanofibrous mats in vitro was investigated by UV spectrophotometry. The release profiles for core-shell nanofibers showed more controlled release of the growth factors compared with the blended electrospun fibers. The experimental results show that controlled release of BMP2 and DEX can induce hMSC to differentiate into osteogenic cells for bone tissue engineering. The results imply that PLLACL/collagen nanofibers encapsulating two drugs and/or proteins have great potential in bone tissue engineering.

Biologically active polymers: synthesis and antimicrobial activity of modified glycidyl methacrylate polymers having a quaternary ammonium and phosphonium groups

Polymers with antibacterial activity have been synthesized by chemical modification of poly(glycidyl methacrylate). The glycidyl methacrylate was polymerized by the free radical polymerization technique. The poly(glycidyl methacrylate) was hydrolyzed and was chloroacetylated using chloroacetyl chloride. The chloroacetylated product was modified to yield polymers with either quaternary ammonium or phosphonium salts. The antimicrobial activity of the modified glycidyl methacrylate polymers has been examined against a variety of test microorganisms by the cut plug and the viable cell counting methods using shake flask of ten times diluted nutrient broth medium. All three polymers obtained were inhibitory to the growth of Gram negative bacteria (Escherichia coli, Pseudomones aeruginosa, Shigella sp. and Salmonella typhae) and Gram positive bacteria (Bacillus subtilis and B. cereus) as well as the fungus (Trichophytun rubrum). It was found that the growth inhibitory effect varied according to the structure of the polymer and the composition of the active group and increased with increasing the concentration of the polymer. The tested polymers showed more antimicrobial activity against Gram negative bacteria and the fungus, whereas were less active against Gram positive bacteria.

In situ cross-linked superwetting nanofibrous membranes for ultrafast oil–water separation

Creating a practical and energy-efficient method with high efficacy to separate oil–water mixtures, especially those stabilized by surfactants, has proven to be extremely challenging. To overcome this challenge, a novel and scalable strategy was developed for the synthesis of superhydrophilic and prewetted oleophobic nanofibrous membranes by the facile combination of in situ cross-linked polyethylene glycol diacrylate nanofibers supported on polyacrylonitrile/polyethylene glycol nanofibrous (x-PEGDA@PG NF) membranes. The as-prepared x-PEGDA@PG NF membranes have shown superhydrophilicity with ultralow time of wetting and promising oleophobicity to achieve effective separation for both immiscible oil–water mixtures and oil-in-water microemulsions solely driven by gravity. These new membranes having a good mechanical strength of 14 MPa and mean pore sizes between 1.5 and 2.6 μm have shown a very high flux rate of 10 975 L m−2 h−1 with extremely high separation efficiency (the residual oil content in filtrate is 26 ppm). More importantly, the membranes exhibit high separation capacity, which can separate 10 L of an oil–water mixture continuously without a decline in flux, and excellent antifouling properties for long term use, thus making them important candidates for treating wastewater produced in industry and daily life. Such membranes are also ideal for high viscosity oil purification such as purification of crude oil.

Preparation of polyamide-6/chitosan composite nanofibers by a single solvent system via electrospinning for biomedical applications.

This work was focused on preparation and characterizations of chitosan blended polyamide-6 nanofibers by a new single solvent system via electrospinning process for human osteoblastic (HOB) cell culture applications. The morphological, structural and thermal properties of the polyamide-6/chitosan nanofibers were analyzed by using field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), Fourier transform-infrared (FT-IR) spectroscopy, Raman spectroscopy, differential scanning calorimetry (DSC) and thermogravimetry (TGA). SEM images revealed that the nanofibers were well-oriented and had good incorporation of chitosan. FT-IR results indicated that the amino groups of chitosan existed in the blended nanofibers. TGA analysis revealed that the onset degradation temperature was decreased with increasing chitosan content in the blended nanofibers. The morphological features of the cells attached on nanofibers were confirmed by SEM. The adhesion, viability and proliferation properties of osteoblast cells on the polyamide-6/chitosan blended nanofibers were analyzed by in vitro cell compatibility test.

Sandwich-structured PVdF/PMIA/PVdF nanofibrous separators with robust mechanical strength and thermal stability for lithium ion batteries

Novel, sandwich-structured PVdF/PMIA/PVdF nanofibrous battery separators with robust mechanical strength and thermal stability are fabricated via a sequential electrospinning technique. The nanofibers of the PVdF and the PMIA layers are bonded and interconnected on the interface boundary without any polymer binder or post-treatment. Benefiting from the high porosity of the as-prepared membranes and the introduction of PMIA, the PVdF/PMIA/PVdF composite membranes exhibit high ionic conductivity (2.3 times higher than that of the Celgard membrane), robust tensile strength (13.96 MPa), and excellent thermal stability, sustaining insulation after closing the pores in the PVdF layer. Hot oven testing reveals that the composite membranes exhibit no dimension shrinkage after being exposed to 180 °C for 1 h. Furthermore, the as-prepared-membrane-based Li/LiCoO2 cell shows a higher capacity retention of 93.10% after 100 cycles and better rate performance compared with the cell using the Celgard membrane, providing new insight into the design and development of high-performance rechargeable lithium ion batteries.

Hierarchically structured polysulfone/titania fibrous membranes with enhanced air filtration performance.

Hierarchically structured, superhydrophobic filter medium exhibiting robust filtration performance to airborne particulate were prepared by a facile deposition of electrospun polysulfone/titania nanoparticles (PSU/TiO2 NPs) on a conventional nonwoven substrate. The air permeability, tensile strength and abrasion resistance of pristine PSU fibrous membranes could be finely controlled by regulating the solvent composition and number ratios of jets. By employing the TiO2 NPs incorporation, the pristine PSU fibers were endowed with promising superhydrophobicity with a water contact angle of up to 152°. The quantitative hierarchical roughness analysis using N2 adsorption method has confirmed the major contribution of TiO2 NPs on enhancing the porous structure and surface fractal features with irregular rough structure. Filtration performance studies have revealed that the filtration efficiency and pressure drop of resultant hybrid membranes could be manipulated by tuning the surface composition as well as the hierarchical structures. Furthermore, the as-prepared PSU/TiO2-5 membrane exhibited improved filtration efficiency (99.997%) and pressure drop (45.3 Pa) compared with pristine PSU membrane, which would make them a promising media for fine particle filtration, and a new insight was also provided into the design and development of high performance filter medium based on hierarchical structured fibers.

Electrospinning collagen/chitosan/poly(L-lactic acid-co-ϵ-caprolactone) to form a vascular graft: Mechanical and biological characterization†

For blood vessel tissue engineering, an ideal vascular graft should possess excellent biocompatibility and mechanical properties. For this study, a elastic material of poly (L-lactic acid-co-ε-caprolactone) (P(LLA-CL)), collagen and chitosan blended scaffold at different ratios were fabricated by electrospinning. Upon fabrication, the scaffolds were evaluated to determine the tensile strength, burst pressure, and dynamic compliance. In addition, the contact angle and endothelial cell proliferation on the scaffolds were evaluated to demonstrate the structures potential to serve as a vascular prosthetic capable of in situ regeneration. The collagen/chitosan/P(LLA-CL) scaffold with the ratio of 20:5:75 reached the highest tensile strength with the value of 16.9 MPa, and it was elastic with strain at break values of ~112%, elastic modulus of 10.3 MPa. The burst pressure strength of the scaffold was greater than 3365 mmHg and compliance value was 0.7%/100 mmHg. Endothelial cells proliferation was significantly increased on the blended scaffolds versus the P(LLA-CL). Meanwhile, the endothelial cells were more adherent based on the increase in the degree of cell spreading on the surface of collagen/chitosan/P(LLA-CL) scaffolds. Such blended scaffold especially with the ratio of 20:5:75 thus has the potential for vascular graft applications.

Effects of plasma treatment to nanofibers on initial cell adhesion and cell morphology

Poly-L-lactic acid (PLLA) nanofibers were fabricated by electrospinning and treated with O2 plasma. The surface properties of PLLA nanofibers before and after plasma treatment were characterized by water contact angle measurement and X-ray photoelectron spectroscopy (XPS). It was found that the hydrophilicity of PLLA nanofibers was improved and the amount of oxygen-containing groups increased after plasma treatment. Initial cell adhesion was evaluated by cell capture efficiency based on the cell count method. The results showed that initial porcine mesenchymal stem cells (pMSCs) adhesion to plasma-treated nanofibers was significantly enhanced. Moreover, the morphology of pMSCs on PLLA nanofibers (PLLA NFS) and plasma-treated PLLA nanofibers (P-PLLA NFS) were observed by scanning electron microscope (SEM) after 10 min, 20 min, 30 min and 60 min cell adhesion. It was found that plasma treatment to electrospun nanofibers had a great effect on pMSCs morphology at earlier time points. Therefore, plasma treatment is an efficient surface modification strategy to improve cell adhesion in earlier culture time intervals. It may be a promising method in the design of novel tissue-engineered scaffolds.

Ultra-light 3D nanofibre-nets binary structured nylon 6–polyacrylonitrile membranes for efficient filtration of fine particulate matter

Particulate matter (PM) with an aerodynamic diameter of 2.5 micrometers or less (PM2.5), as one of the most hazardous air pollutants, has raised serious concerns for public health. Although individual or environmental protection could be achieved using conventional fibrous media, high performance filters usually rely on energy-intensive and bulky air-filtering media. In this work, an ultra-lightweight nylon 6–polyacrylonitrile nanofibre-nets binary (N6–PAN NNB) structured membrane, consisting of an ambigenous nanofibre framework through which run two-dimensional nano-nets, for sieving-enhanced capture of fine particles was demonstrated. The high coverage N6 nano-nets and low packing density of PAN nanofibres are certified as an efficient property promoter when the fibre spinning jet ratio of N6/PAN reaches 2/2, thereby improving the porosity, filtration efficiency, flow resistance, and stability. Upon exposure to 300 nm NaCl aerosol particles, the N6–PAN2/2 NNB membrane with a low basis weight of 2.94 g m−2 exhibited high filtration efficiency (99.99%) and desirable quality factor (0.1163 Pa−1) even though under a high flow rate (90 L min−1), significantly better results than those of glass fibre and melt-blown polypropylene fibre-based media. Ultimately, three-dimensional computer simulation based on the images of N6-15 and N6–PAN2/2 membranes after particle loading and filtration data via GeoDict were processed statistically through principal component analysis and then used to graphically express the particle deposition pattern change from surface filtration to deep bed filtration. We hope that the methodology and results presented here will encourage different approaches to diminish the negative impact of PM2.5 air pollution, in particular the frequency of haze occurrence in rapidly developing countries.