Preparation of cellulose/multi-walled carbon nanotube composite membranes with enhanced conductive property regulated by ionic liquids

Cellulose/multi-walled carbon nanotubes (MWCNTs)- composite membranes applied in electrochemical and biomedical fields were prepared using 1-ethyl-3-methylimidazolium diethyl phosphate (EmimDEP) as solvent in this study. With the increasing of MWCNTs amount, the membrane conductivity increased, and the conductivity reached 9.1 S/cm as the mass ratio of MWCNTs to cellulose being 2:1. The additions of sodium dodecyl sulfate (SDS), 1-hexadecyl-3-methylimidazolium bromide (C₁₆mimBr) and 1-butyl-3-methylimidazolium tetrafluoroborate (BmimBF₄) efficiently improved the conductivity, mechanical property, and thermal stability by promoting the dispersion of MWCNTs. When the mass ratio of C₁₆mimBr to MWCNTs changed from 0 to 0.3:1, the conductivity increased from 0.08 S/cm to 0.14 S/cm, and the tensile strength increased from 13.3 MPa to 17.0 MPa. These results indicate that the binary ionic liquids (ILs) system can regulate the properties of the composite membranes, and is a feasible approach for preparing cellulose/MWCNTs composite membranes with enhanced properties.     

Release of doxycycline through cellulose acetate symmetric and asymmetric membranes produced from recycled agroindustrial residue: Sugarcane bagasse

Cellulose acetate is one of the components employed in drug controlled-release systems in the form of membranes. The aim of this study was to examine the controlled-release of doxycycline employing cellulose acetate symmetric and asymmetric membranes as matrices. The cellulose triacetate was produced from sugarcane bagasse through a homogeneous acetylation reaction, using acetic acid as the solvent, acetic anhydride as the acetylating agent and sulfuric acid as the catalyst. The viscosity average molecular weight of the cellulose acetate produced was 39,000 g mol⁻¹. The symmetric membranes were produced using a system solvent of dichloromethane/ethanol (9:1, v/v) and the asymmetric membranes were produced from the same solvent system and 10% of water. For the formulation of both, 5% of doxycycline was used. The membranes were characterized by thermal analysis (DSC and TGA) and scanning electron microscopy SEM. The release of doxycycline through cellulose triacetate matrices was examined using spectrophotometric analysis in the ultraviolet-visible region, at 275 nm. The results revealed that asymmetric membranes release 80% of the drug in 100 min, while symmetric membranes release 14% of the drug during the same time interval.     

Electrospun curcumin loaded poly(lactic acid) nanofiber mat on the flexible crosslinked PVA/PEG membrane film: Characterization and <Emphasis Type="Italic">in vitro</Emphasis> release kinetic study

Herein, a biodegradable and biocompatible composite comprising of support membrane based on crosslinked PVA/PEG film and curcumin loaded electrospun poly(lactic acid) (PLA) nanofiber mat is introduced. The membrane film was prepared from PVA/PEG blend followed by crosslinking with an optimum amount of citric acid, 15 wt.%. After then, PLA solutions with different curcumin content, 0-11 wt.%, were electrospinned on the prepared membrane substrate. The prepared film showed high water absorption, water vapor transmission rate and superior mechanical properties with improved elastic modulus, tensile strength and with an elongation of around 320 % with respect to the non-crosslinked one. Also, the scanning electron microscopy was revealed uniformly dispersed pores throughout the membrane film with a nearly narrow in size distribution centered at 36 μm. As well, a nanostructure porous morphology was found for the electrospun fibrous curcumin loaded PLA from the scanning electron microscopy micrographs and the average fiber diameter was decreased with curcumin content. In vitro drug release from the prepared flexible composite into the vertical diffusion cell was recorded by the measuring curcuminoids content using high performance liquid chromatography and drug release kinetic evaluations were revealed that the release pattern of all prepared samples, containing different content of curcumin, well fitted to the Higuchi’s model signifying diffusion-controlled release mechanism. As well, the determined release rate at the second release stages, i.e. steady state flux (J), was varied from 0.31 to 43.53 μg·cm^-2·h^-1 with increasing drug content from 1 to 11 wt.%. Regarding this results, this flexible composite by providing the moist environment along with miraculous healing properties of curcumin, can be potential candidate for transdermal drug delivery.     

Preparation of the Multicomponent High Temperature Proton Exchange Membranes with Layer by Layer Self-assembly Technique

Layer by layer (LBL) self-assembly technique has been proved to be a feasible method that enables to accomplish the preparation of functional membranes with multilayered structure. In this research, the polymer of sulfonated polyetheretherketone (SPEEK) and thioglycolic acid capping of cadmium telluride (CdTe) nanocrystals as polyanion, the polymer of polyurethane (PU) as polycation have been used to prepare membrane electrolytes. These multilayered membranes showed good thermal stability and exhibited low liquid methanol permeability, which provided a possibility for the prepared membranes as proton exchange membranes (PEMs) to apply in direct methanol fuel cells (DMFCs). We have also demonstrated that the multicomponent (SPEEK/PU/CdTe/PU)₁₀₀ membranes favored to combine more phosphoric acid (PA) molecules and possessed a higher proton conductivity comparing to the bicomponent (SPEEK/PU)₂₁₀ membranes. So PA doped (SPEEK/PU/CdTe/PU)₁₀₀ membrane presented a maximum proton conductivity up to 8.6×10^-2 S/cm at 160 °C under anhydrous conditions. However, PA doped (SPEEK/PU)₂₁₀ membranes underwent a drop on proton conductivity while the temperature exceeded 120 °C.     

Development and characterization of bamboo gauze fabric coated with polymer and drug for wound healing

The bamboo yarn of Ne 40^s was used for the preparation of the Gauze fabric. The physical properties such as areal density and stiffness of fabrics were measured. The fabric was then scoured and bleached as per the standard procedure using distilled water. Chitosan-sodium alginate, Calcium-sodium alginate polymer and their mixture were coated separately on the gauze structure to improve the antibacterial and wound healing property of the bandage. Scanning electron microscope (SEM) analysis was carried out to observe the uniform distribution of polymers in the samples. The antibiotic drugs were selected based on the antibiotic sensitivity test. The drugs such as Tetracycline hydrochloride (250 mg), Chloramphenicol (250 mg) and Rifampicin (250 mg) were immobilized on the polymer coated fabrics to increase the rate of wound healing and antibacterial activity. The drug loaded samples were subjected to drug release study for about four days in a static condition. The results show that good amount of drug was released during all the four days. Further, the antibacterial activity of the drug loaded and polymer coated samples were evaluated against S. aureus and Proteus bacteria. The results show excellent antibacterial activity.     

Preparation and Characterization of A Semi-interpenetrating Network Alkaline Anion Exchange Membrane

A series of semi-interpenetrating network (semi-IPN) anion exchange membranes (QCS/St-G_8-2-8, Quaternized chitosan/styrene-[maleic alkylene group diethyl bis (octyl dimethyl chloro/bromide), abbreviated as G_8-2-8] were prepared via in-situ polymerization by Styrene (St) and G_8-2-8 in QCS casting solution. During the process of in-situ polymerization, linear block polymers (St-G_8-2-8) of Styrene and G_8-2-8 was constructed, then was mixed with QCS casting solution, followed crosslinking the QCS by glutaraldehyde (GA). With the increasing content of linear block polymer, water uptake and swelling ratio of the composite membrane decreased; This kind of linear structure makes an order arrangement of quaternary ammonium groups which improves the OH? migration efficiency. At 70 °C, the M-30 composite membrane performs a high OH? conductivity of 8.20×10^-2 S·cm^-1, the methanol permeability is 3.23×10^-6 cm^-2·s^-1 which is still lower than Nafion 115 of 2.42×10^-6 cm^-2·s^-1, but M-30 shows a higher selectivity of 25.3 than Nafion 115 of 11.6. Furthermore, the membranes exhibited excellent thermal stability (≥150 °C), the tensile strength of the composite membrane is in the range of 14-25 MPa and elongation at break is in the range of 16-37 % at room temperature, as well as superior chemical stability in 1.0 M KOH solution for 250 h.     

One-step fabrication of high selective hollow fiber nanofiltration membrane module

A novel hollow fiber composite Nanofiltration (NF) membrane was fabricated by an improved preparation procedure. Using hollow fiber ultrafiltration (UF) membrane modules as the supporting modules, hollow fiber composite NF modules were fabricated by the one-step interfacial polymerization method. The effects of preparation conditions (such as concentration of the monomers, reaction time of monomers and ambient relative humidity, etc.) on the performance of the hollow fiber composite membranes were studied. When tested at 0.6 MPa, room temperature, the hollow fiber composite membrane had a rejection sequence of MgSO₄>Na₂SO₄>MgCl₂>NaCl and a permeate flux sequence of NaCl>Na₂SO₄> MgSO₄>MgCl₂. The nagative charge character of the membrane surface was examined by streaming potential methods. The effect of the surface electrolyte properties on the membrane separation performance was investigated. The morphologies of the hollow fiber composite Nanofiltration membranes were studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM).     

Chitosan composites for bone tissue engineering--an overview

Bone contains considerable amounts of minerals and proteins. Hydroxyapatite [Ca₁₀(PO₄)₆(OH)₂] is one of the most stable forms of calcium phosphate and it occurs in bones as major component (60 to 65%), along with other materials including collagen, chondroitin sulfate, keratin sulfate and lipids. In recent years, significant progress has been made in organ transplantation, surgical reconstruction and the use of artificial protheses to treat the loss or failure of an organ or bone tissue. Chitosan has played a major role in bone tissue engineering over the last two decades, being a natural polymer obtained from chitin, which forms a major component of crustacean exoskeleton. In recent years, considerable attention has been given to chitosan composite materials and their applications in the field of bone tissue engineering due to its minimal foreign body reactions, an intrinsic antibacterial nature, biocompatibility, biodegradability, and the ability to be molded into various geometries and forms such as porous structures, suitable for cell ingrowth and osteoconduction. The composite of chitosan including hydroxyapatite is very popular because of the biodegradability and biocompatibility in nature. Recently, grafted chitosan natural polymer with carbon nanotubes has been incorporated to increase the mechanical strength of these composites. Chitosan composites are thus emerging as potential materials for artificial bone and bone regeneration in tissue engineering. Herein, the preparation, mechanical properties, chemical interactions and in vitro activity of chitosan composites for bone tissue engineering will be discussed.     

Preparation and characterization of Ceftazidime loaded electrospun silk fibroin/gelatin mat for wound dressing

Fabrication of Ceftazidime (CTZ) loaded silk fibroin/gelatin (SF/GT) nanofibers (NFs) without the loss of structure and bioactivity of CTZ was demonstrated by electrospinning method. The structure, morphology and mechanical properties of the electrospun SF/GT nanofibrous mats were characterized using FT-IR, SEM and DSC. The drug release profile of different electrospun fibers was analyzed using spectrophotometric method, and also diffusion method was applied to assess the antibacterial effect of NFs. Cell viability was evaluated by MTT assay. The results show that the average diameter of drug loaded NFs at the optimum polymer to drug feeding ratio (10:1) was 276.55±35.8 nm, while increasing the feeding ratio to 1:1 increases the average diameter to 825.02±70.3 nm. FT-IR of drug loaded NFs was revealed that CTZ was successfully encapsulated into NFs while viability study approved cytocompatibility of SF/GT NFs. CTZ was released from NFs during 6 h, and formation of inhibition zone in diffusion test demonstrated the antibacterial effect of drug loaded NFs. Altogether, the CTZ loaded SF/GT NFs can improve the drug effectiveness particularly in the prevention of post-surgical adhesions and infections for wound dressing.     

Development and characterization of alginate-chitosan-hyaluronic acid (ACH) composite fibers for medical applications

Natural materials and plants have a long history of medical applications due to their broad range of favorable biological functions including biocompatibility, anti-bacterial, anti-oxidant and anti-inflammatory properties. Main objective of this study was to develop alginate-chitosan-hyaluronic acid (ACH) composite fibers with controlled drug release, and liquid retention properties for better moist wound healing. The dope comprising sodium alginate was extruded into calcium chloride (CaC1₂) coagulation bath. The developed calcium alginate fibers were then passed through a bath containing hydrolyzed chitosan and dip coated with hyaluronic acid for 24 hours. The resulting ACH composite fibers were then rinsed with deionized water and dried using acetone. These fibers were tested for tensile properties, % swelling, liquid absorption (g/g) and controlled drug release. The results concluded that ACH composite fibers can be produced by wet spinning and have adequate tensile properties, high % swelling, liquid absorption (g/g) and controlled release of hyaluronic acid for improved wound healing.     

Electrospun Poly-lactic Acid/Chitosan Nanofibers Loaded with Paclitaxel for Coating of a Prototype Polymeric Stent

Electrospun composite fibers of poly-lactic acid (PLA), chitosan (Ch) and paclitaxel (PTX) were fabricated for surface covering of a polymeric prototype PLA stent by means of single nozzle electrospinning approach to prepare a low cytotoxicity drug-eluting stent. Different concentrations of the drug (40 %, 60 %, 80 %, 100 % and 120 %) and chitosan (3 %, 5 %, 7 % and 9 %) were incorporated to reach the optimum composite fibers. The electrospun composite fibers were subjected to detailed analyses including scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), tensile test, MTT assay, cell culture and in vitro drug release. Results have confirmed a proper physical encapsulation of PTX in the polymeric matrix in which no chemical bonding was detected between the polymers and the drug. Among the fabricated composite fibers, specimens including 40 % and 60 % drug also exhibited an excellent cytotoxicity and controlled drug release. SEM images have proved the effect of paclitaxel in resisting cell adhesion and propagation on the fibers. Findings from this study suggest a novel polymer/drug coating that could be potentially applicable in surface covering of polymeric stents e.g. PLA stents.     

Electrospun grape seed polyphenols/gelatin composite fibers contained silver nanoparticles as biomaterials

GSP/gelatin composite nanofiber membranes containing silver nanoparticles were successfully fabricated as a novel biomaterial by electrospinning. The silver nanoparticles (AgNPs) were synthesized with the grape seed polyphenols (GSP) as reducing agent in aqueous solution of gelatin, and then the GSP/gelatin/AgNPs mixed solution was electrospun into nanofibers at 55 °C. The scanning electron microscopy (SEM) confirmed that the composite fibers were uniform and the average fiber diameter ranged between 150 nm and 230 nm with an increase in applied potentials from 14 kV to 22 kV. And the transmission electron microscopy (TEM) showed that silver nanoparticles distributed individually in the fibers with the average particle size of about 11 nm. Furthermore, the ultraviolet visible spectrophotometer (UV-vis spectroscopy) test demonstrated that all of Ag⁺ converted to Ag⁰ when the concentration of gelatin was 24 wt% and the mass ratio of GSP to AgNO₃ was about 5:2. The antibacterial activities of the fiber membranes against E.coli and S.aureus were measured via a shake flank test and demonstrated good performance after the importation of silver nanopaticles. Cytotoxicity testing also revealed that fiber membranes contained silver nanoparticles had no cyto-toxic. All the results indicated that the GSP was effective for the formation and stabilization of silver nanoparticles in composite nanofibers mats which had the potential for applications in antimicrobial tissue engineering and wound dressing.     

Designing double-layered nanofibrous membranes as a wound dressing material

New generation wound dressings require the criteria that both bioactive and conventional wound dressing materials can recompense the fundamental properties like defense of wound from microbial invasion, dehydration during the wound care duration and mimic the healing process. In this study, functional double-layered nanofibrous composite membranes were fabricated via electrospinning method. The matrices consist of a sheet of ampicillin loaded poly(2-hydroxylethyl methacrylate/polyacrylic acid (pHEMA/pAA) nanofibers on the upper side (first layer: pH sensitive antibacterial barrier) and a sheet of poly(ε-caprolactone) (PCL)/gelatin nanofibers (second layer: bioactive part). Ampicillin was successfully incorporated to double-layered matrices which greatly changed the mechanical properties, biodegradability and water uptake ratios (up to 4 fold higher values). The success of the antimicrobial activity of ampicillin on Staphylococcus aureus and Escherichia coli was indicated by the inhibition zone test. pH sensitivity was confirmed by the swelling and ampicillin release studies by shifting pH value to basic environment. Thus, double-layered pHEMA-pAA nanofibers suggest as a potential wound dressing material for its pH sensitive drug delivery ability and its bioactive part.     

Facile Fabrication of Electrospun Silica Nanofibrous Membrane with Hydrophobic,Oleophilic and Breathable Performances

We report a simple and versatile method to prepare hydrophobic composite SiO₂ membrane. The electrospun SiO₂ membrane was selected due to its good flexibility and thermal stability. The hydrophobic SiO₂ membrane was succussfully prepared by simply evaporating a thin polydimethylsiloxane (PDMS) layer on the fiber surface. The characterization results show that the PDMS layer is too thin to be observed. The PDMS coating has no influence on the porous structure of the fibrous membrane, but imparts the good hydrophobicity and oleophilicity to the SiO₂ nanofibers. As demonstration, the hydrophobic SiO₂-PDMS membrane displays good oil absorption performance from the oil/water mixture, as well as filtration membrane for oil/water separation. Additionally, due to the proper pore size and hydrophobic surface, the SiO₂- PDMS membrane shows good waterproof performance and breathability at the same time.     

Effects of zinc oxide Nanospheres on the Separation performance of Hollow fiber poly(piperazine-amide) composite nanofiltration membranes

The inner-skinned hollow fiber composite (HFC) nanofiltration (NF) membranes were modified through the incorporation of zinc oxide nanospheres in the poly(piperazine amide) layer during the interfacial polymerization (IP) process. The active layer was coated on the inner surface of polysulfone (PSF) support membrane via Two-way coating technique. The chemical composition and morphology of HFC membrane surface were evaluated through the Attenuated Total Reflectance Fourier Transform Infrared spectroscopy (ATR-FTIR) and Scanning Electronic Microscopy (SEM). The effects of zinc oxide (ZnO) nanospheres on membrane performance including the hydrophilicity, separation performance and chlorine resistance were investigated. The results showed that the modified HFC membranes with low concentration ZnO nanospheres (1.5 wt%) had an improved flux (33.8 L·m^-2·h^-1) meanwhile the salt rejection of MgSO₄ was well maintained (92.2 %) at 0.7 MPa. The introduction of ZnO also dramatically enhanced the chloride resistance of composite NF membranes in comparison with the control membranes prepared without ZnO. Therefore, nano metallic oxide like ZnO could be considered as a potential modifier to improve the performance of HFC nanofiltration membranes.     

Polyaniline-doped TiO<Subscript>2</Subscript>/PLLA fibers with enhanced visible-light photocatalytic degradation performance

A simple and practical strategy has been developed for preparing polyaniline(PANi)-doped TiO₂/poly(l-lactide) (P@TiP-C) fibers by a combination of coaxial-electrospinning and in-situ polymerization. The TiO₂/PLLA composite fibers with TiO₂ located on the surface were fabricated by coaxial-electrospinning, with PLLA as the core phase and a dispersion of TiO₂ particles, a well-known photocatalyst, in the sheath phase. The aniline monomers were also located in the core phase and in-situ polymerized by ammonium persulfate (APS) after electrospinning. SEM images show that TiO₂ particles were located on the surface of PLLA fibers. Photocatalytic degradation tests show that the P@TiP-C fibers exhibit enhanced photocatalytic activity for degradation of methyl orange under visible light, likely due to the synergistic effect of PANi and TiO₂.     

Bioadhesive Controlled Metronidazole Release Matrix Based on Chitosan and Xanthan Gum

Metronidazole, a common antibacterial drug, was incorporated into a hydrophilic polymer matrix composed of chitosan xanthan gum mixture. Hydrogel formation of this binary chitosan-xanthan gum combination was tested for its ability to control the release of metronidazole as a drug model. This preparation (MZ-CR) was characterized by in vitro, ex vivo bioadhesion and in vivo bioavailability study. For comparison purposes a commercial extended release formulation of metronidazole (CMZ) was used as a reference. The in vitro drug-release profiles of metronidazole preparation and CMZ were similar in 0.1 M HCl and phosphate buffer pH 6.8. Moreover, metronidazole preparation and CMZ showed a similar detachment force to sheep stomach mucosa, while the bioadhesion of the metronidazole preparation was higher three times than CMZ to sheep duodenum. The results of in vivo study indicated that the absorption of metronidazole from the preparation was faster than that of CMZ. Also, MZ-CR leads to higher metronidazole C_max and AUC relative to that of the CMZ. This increase in bioavailability might be explained by the bioadhesion of the preparation at the upper part of the small intestine that could result in an increase in the overall intestinal transit time. As a conclusion, formulating chitosan-xanthan gum mixture as a hydrophilic polymer matrix resulted in a superior pharmacokinetic parameters translated by better rate and extent of absorption of metronidazole.     

Composite wound dressing for drug release

Present study is focused on the preparation of two layers composite wound dressing for drug release. The outer layer is made of hydrogel which contains of drug and the core layer is made of fabric. The two layers structure of composite dressing is formed by grafting of polyacrylamide-co-acrylic acid hydrogel on cotton fabric using ammonium per sulphate (APS) as chemical initiator and polyethylene glycol (PEG) as crosslinker. The major factors affecting graft copolymerization of hydrogel on cotton fabric are optimized by varying concentration of monomers & initiator, reaction temperature and addition time of crosslinker. Maximum grafting of hydrogel is obtained at 5 % (w/v) APS and 15 % acrylamide/acrylic acid (1:1 w/w ratio) concentration. The FTIR spectra of composite dressing shows characteristics peak of acrylic acid and acrylamide. The composite wound dressing material is loaded with model drug bovine serum albumin (BSA) and drug release behaviour is studied at different pH. The dressing shows drug release in different pH with maximum release of drug in acidic medium.     

Electrospun in-situ hybrid polyurethane/nano-TiO<Subscript>2</Subscript> as wound dressings

By combining the organic-inorganic hybridization, wet phase inversion, and electrospinning, novel electrospun polyurethane (PU) membranes with in-situ generated nano-TiO₂ were prepared, which satisfied the requirements of an ideal wound dressing. The morphology of the PU-TiO₂ mats and the cross sectional morphologies of the membranes were characterized by a scanning electron microscopy (SEM). The average diameter of the individual fibers obtained from the solutions was 341±12 nm. SEM micrographs with higher magnification further showed that the in-situ generated TiO₂ particles were well-separated and dispersed homogeneously in the membranes. The average sizes of TiO₂ particles were increased from 31 to 57 nm, with the increase of nano-TiO₂ concentration. The water vapor transmission rates (WVTRs) of the membranes were in the range of 373.55–3121.86 g/m²·d and decreased gradually with the increase of nano-TiO₂ concentration. The water absorption of various PU membranes was in the range of 210.90–397.98 % which was enough to prevent wound beds from exudate accumulation. Shake flask testing indicated that the PU membrane exhibited antibacterial efficiency against Pseudomonas aeruginosa (Ps. aeruginosa) and Staphylococcus aureus (S. aureus) due to in-situ generated of nano-TiO₂. These electrospun nanofibrous membranes also had no toxic effect and showed good and immediate adherence to L929 cells.     

Characterization and antibacterial properties of Ag NPs doped nylon 6 tree-like nanofiber membrane prepared by one-step electrospinning

A hierarchically Ag/nylon 6 tree-like nanofiber membrane (Ag/PA6 TLNM) was fabricated by adding tetrabutylammonium chloride (TBAC) and silver nitrate (AgNO3) into spinning solution via one-step electrospinning. TBAC presented in PA6/formic acid (HCOOH) spinning solution was able to cause the formation of a tree-like structure due to its space steric structure and the increasing of solution conductivity. Electrospinning solvent acted as a reducing agent for in situ conversion of AgNO₃ into silver nanoparticles (Ag NPs) during the solution preparation. SEM, TEM, FT-IR XPS and XRD confirmed that Ag NPs were doped in the prepared nanofiber membrane successfully and the mechanical properties, pore size distribution and hydrophilicity of the membranes were investigated. The results showed that the tree-like structure improved the mechanical properties and hydrophilicity of the membrane while ensuring high specific surface area and small pore size. And the Ag/PA6 TLNM showed superior antibacterial properties against both E. coli and S. aureus compared with common Ag/PA6 nanofiber membranes (Ag/PA6 NMs). All of the results show that the Ag/PA6 TLNM would have potential applications in water purification.