Fabrication of electropsun PLGA and small intestine submucosa-blended nanofibrous membranes and their biocompatibility for wound healing

In recent decades, tremendous research has focused on the production of nanoscale fibers using synthetic polymers, with the goal of fabricating nanofibrous scaffolds for wound healing. However, the hydrophobicity of such polymers typically hinders attachment and proliferation of the cells. In this study, we combined poly-d,l-lactide-co-glycolide (PLGA) and small intestine submucosa (SIS) to fabricate blended nanofibers for wound healing by electrospinning. PLGA and SIS were dissolved in 1,1,1,3,3,3-hexafluoro isopropanol to produce different weight ratios of PLGA/SIS-blended nanofibrous membranes (NFM). Physicochemical characterization of the electrospun NFM was performed by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy, water contact angle analysis, degradation test and tensile testing. The PLGA/SIS-blended NFM showed improved hydrophilicity and tensile strength. Better infiltration, attachment and proliferation of rat granulation fibroblasts of PLGA/SIS-blended NFMs compared to PLGA NFMs were identified by morphological differences determined by SEM and a water-soluble tetrazolium salt assay kit. Based on our results, the PLGA/SIS blended NFMs were found to be suitable for use as a potential material for wound dressing.     

N-halamine-bonded cotton fabric with antimicrobial and easy-care properties

N-halamine precursor 2,2,6,6-tetramethyl piperidinol (TMP), a hindered amine light stabilizer, was bonded onto cotton fabric by using 1,2,3,4-butanetetracarboxylic acid (BTCA) as a crosslinking agent. A variety of treating conditions including TMP concentration, curing temperature and time, and catalyst were studied. The treated fabrics were characterized using FTIR spectra and scanning electron microscope (SEM). The cotton fabric treated with TMP precursor could be rendered biocidal upon exposure to dilute household bleach. The chlorinated cotton swatches showed great efficacy and inactivated 100 % of Staphylococcus aureus with 7.1 log reduction with 5 min of contact and 83.25 % of E. coli O157:H7 at 10 min of contact. In addition, the wrinkle recovery angle of the treated cotton fabrics increased from 229 ° of untreated cotton fabrics to 253 °. This study provided a practical finishing process to produce cotton fabrics with easy care and antibacterial functionalities at the same time.     

Enhanced dielectric properties of electrospun titanium dioxide/polyvinylidene fluoride nanofibrous composites

Titanium dioxide/polyvinylidene fluoride (TiO₂/PVDF) composite was prepared by electrospinning process to enhance the dielectric properties for application as a gate insulator in organic thin-film transistors (OTFTs). Scanning electron microscopy, thermogravimetric analysis, and X-ray diffraction were employed to characterize the as-prepared samples, and then their dielectric constants were investigated by impedance analysis. The impedance results show that the dielectric constant of the electrospun TiO₂/PVDF nanofibers is higher than those of other samples, demonstrating that electrospun TiO₂/PVDF composite can be a proper candidate for gate insulators in OTFTs.     

Development and characterization of multifunctional electrospun ferric oxide-gelatin-glycerol nanofibrous mat for wound dressing applications

In this study, we developed optimal multifunctional electrospun wound dressings possessing an antibacterial activity and rich in iron, a vital trace element for cell growth. Therefore, synthetic ferric oxide nanoparticles (α-Fe₂O₃ NPs) were ultrasonically dispersed into preheated gelatin-glycerol solution. A variety of techniques (X-ray diffraction (XRD), Fourier transform infrared (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), differential thermal analysis (DTA), in-vitro swelling-degradation studies and antibacterial tests) were used to characterize the electrospun mats. The results highlight that α-Fe₂O₃ NPs could be successfully dispersed into the electrospun gelatin nanofibers. The electrospun ferric oxide-gelatin-glycerol nanofibrous mats revealed free beads nanofibers with appropriated swelling-degradation behavior. It was observed that addition of α-Fe₂O₃ NPs enhanced the antibacterial activity of electrospun mats against positive and negative bacteria.     

Nylon textiles grafted with chitosan by open air plasma and their antimicrobial effect

Chitosan is a natural non-toxic biopolymer and is widely used in various fields because of the antimicrobial activities. In this study, the properties of nylon textiles grafted with chitosan oligomer or chitosan polymer after being activated by open air plasma were evaluated. Results showed that nylon textiles grafted with chitosan polymer had better antibacterial performances than those grafted with chitosan oligomer. Air plasma activation at a higher speed (26 m/min) for a few times facilitated the grafting of chitosan and critically determined the antibacterial activities. Further treatment with air plasma after grafting improved the antibacterial effect. Overall, chitosan-grafted nylon textiles showed good antibacterial potential as well as biocompatibility.     

Dyeing properties and antimicrobial activity of silk fabric with extract of unripe Citrus Unshiu fruits

This study was carried out to optimize dyeing conditions of unripe Citrus Unshiu extract on silk fabric and to evaluate antimicrobial activity of the dyed fabric for its potential use as a functional natural dye. Unripe fruits of Citrus Unshiu in Jeju Island, Korea, extracted in 80 % Ethanol solution to final solid dye powder were dyed on silk fabric under a variety of conditions such as dye bath concentrations, temperature, and dyeing duration together with mordanting. Dyeing fastness properties to washing, rubbing, perspiration, and light were tested and the antimicrobial activities of the dyed fabric against Staphylococcus aureus and Klebsiella pneumoniae were investigated quantitatively. As results, the fabric showed the maximum dye uptake (K/S) under the conditions of 80 °C for temperature, 30 min for duration, and 600 % (o.w.f.) for dye concentration. Both pre- and post-mordanting seemed not to be effective on increasing K/S values of the dyed silk fabrics under the optimum dyeing conditions. Fastness ratings to washing, rubbing, and perspiration were all very good (4–5 grades) for both 300 and 600 % dyed silk fabrics. Excellent antimicrobial activities over 99 % reduction rate against two both bacteria were exhibited for all of dyed fabrics undergone more than 300 % of dye concentration. From these results, it was concluded that the dye concentration of 300 % of unripe Citrus Unshiu could be employed to produce antimicrobial silk fabric. Furthermore, to get more saturated shades on the fabric by the citrus, higher dye concentration such as 600 % was available as well.     

The antimicrobial spectra of organic compounds with respect to their potential as hay preservatives

Formic acid, sodium diacetate, propionic acid and two of its ammonium salts, ammonium isobutyrate and tributyl phosphate, were examined for their antimicrobial effects with cultures of micro-organisms typical of the microflora of moist hay. The assays, which were conducted at pH 5, 6, 7 and 8, revealed that all potential preservatives discriminated against actinomycetes in particular and were least effective against fungi. In addition, it was apparent that antimicrobial properties were enhanced under slightly acid conditions and for this reason the use of mixtures of organic acids and salts in commercial hay preservatives is justified. Tributyl phosphate not only had the strongest antimicrobial properties of the compounds tested but was also the least affected by pH.     

Evaluation of comfort properties of polyester knitted spacer fabrics finished with water repellent and antimicrobial agents

In order to impart barrier properties against water and microorganisms on breathable three dimensional spacer fabrics as medical or technical textiles, fabric samples were treated with two water repellent agents and a quaternary ammonium salt namely cetyltrimethylammonium bromide (CTAB), using pad-dry-cure method. Two different water repellent agents based on hydrocarbon and acrylic copolymer were used. The water repellent property of samples was tested by Bundesmann and contact angle tests. Antimicrobial activity of samples was analyzed quantitatively according to AATCC 100. Simultaneous finishing of samples was done with 3 % CTAB and 4 % fluoroalkyl acrylic copolymer. To study the effect of various treatments on comfort related properties, air and water vapor permeability, water repellency and compression were measured. The results showed that the antimicrobial and water repellent spacer fabrics can be achieved applying selected material without significant changes on their comfort properties. Also a regression model was presented to predict the water vapour permeability of knitted spacer fabrics based on course density (CPC) changing.     

Electrospinning of PHBV/ZnO membranes: Structure and properties

Polyhydroxy butyrate-co-valerate (PHBV) ?? Zinc oxide (ZnO) nano composite fibers were prepared using electrospinning. The structural and optical properties were studied using Fourier transform infrared spectroscopy (FT-IR), Xray diffraction (XRD) and photoluminescence study (PL). The morphology observed with scanning electron microscope (SEM) revealed no significant changes in the nano composite fibers as compared to bare polymer. The low concentration of ZnO nanoparticles resulted in an increase in overall crystallinity of the polymer matrix which was confirmed from FT-IR and XRD results. The photoluminescence (PL) study indicated the quenching of visible emission in the composite fibers. The ratio of UV to visible emission (I_uv/I_vis) intensity was found to be 12.8 times enhanced in the composite fibers compared to bare ZnO nanoparticles. The nanofibrous mats are self supported and hence offer potential applications in optoelectronic devices and the biomedical imaging.     

Interaction of microwave radiation with polyester yarn to enhance its textile properties

The interaction of microwave radiation with Partially Oriented Polyester yarn (PET-POY) was studied with a view to improve its structure and textile related properties. The PET-POY filaments were exposed to Microwave (MW) radiations of frequency 2450 MHz for different durations of time from 15 to 105 sec. The changes in structure and morphology were investigated by using the techniques of X-ray diffraction, birefringence and DSC. The changes in the textile related properties like tensile strength, shrinkage and dye uptake were evaluated. The microwave treatment enhanced the structural properties of PET-POY samples. Significant increase in crystallinity, crystal size and crystalline orientation were noted. In addition a great improvement in total orientation, as measured by birefringence, was found for the treated samples. DSC results showed that crystal distribution became narrower and crystallization rate increased for microwave treated samples as compared to control sample. The tensile strength, shrinkage and dye uptake also showed significant increase, which is very helpful for the textile processes.     

Surface modification of silk fibroin nanofibrous mat with dextran for wound dressing

In this study, we examined the effects of a dextran-modified silk fibroin nanofibrous mat (D-SFNM) on wound healing. To increase the hydrophilicity of silk fibroin (SF), the SF nanofibrous mat (SFNM) was modified with oxidized dextran. The D-SFNM absorbed water faster than the SFNM, and the swelling ratio was increased by approximately 80 % compared with the SFNM. An in vitro cell (NIH3T3) test revealed that fewer cells attached to the D-SFNM than the SFNM, but the proliferation of cells was not significantly affected by the presence of dextran. An in vivo wound healing test with mice indicated that the D-SFNM resulted in a good wound recovery effect similar to a commercial wound dressing material. The increased hydrophilicity of the D-SFNM might balance the moist environment at the wound site, which improves the wound healing compared with the SFNM.     

Investigation of mechanical properties of developed antimicrobial PPsuture/Ag nanocomposite

In order to prevent surgical complications due to microbial infections, we have developed polypropylene suture grafted with silver nanoparticles (PPsuture/Ag nanocomposite) by a simple immersion procedure. Physical and mechanical properties of developed suture are investigated. Suture surface characteristics are examined by scanning electron microscopy (SEM) imaging and atomic force microscopy (AFM). Silver content on suture surface was determined by Inductively coupled plasma atomic emission spectroscopy (ICP-AES). The mechanical properties of developed antibacterial PP suture/Ag were studied. We note that proposed silver coating method has not affected mechanical performances of suture. Antimicrobial performances of PP suture/Ag nanocomposites against S. aureus and E. coli colonies were also investigated.     

Preparation process and antimicrobial properties of cross-linking chitosan onto periodate-oxidized bamboo pulp fabric

Chitosan cross-linked bamboo pulp fabric (CCBPF) was prepared by treating the oxidized bamboo pulp fabric with the chitosan aqueous acetic acid solution. FTIR spectroscopy was used to examine the chemical bonding between chitosan and oxidized bamboo pulp fabrics, X-ray diffraction and thermogravimetry were used to detect the cellulose structure. The impact of the periodate oxidation and chitosan treatment on the physical properties of bamboo pulp fabrics was evaluated by determining the aldehyde content, weight loss, mechanical strength, wrinkle recovery angle, and moisture regain of fabrics as well as chitosan content in the composite chitosan-bamboo pulp fabrics. Antibacterial activity of the CCBPF against Staphylococcus aureus and Escherichia coli was investigated in vitro experiments. The results indicated that the aldehyde groups in the periodate oxidized bamboo pulp cellulose were reacted with the amino groups of chitosan to form Schiff base, and the resultant CCBPF displayed good wrinkle recovery angle and moisture regain. In comparison with those of the oxidized bamboo pulp fabric, the CCBPF exhibited a lower thermal stability, the crystallinity decreased from 42.73 % to 39.15 %, the mechanical strength of CCBPF had no significant change, and the CCBPF showed excellent antibacterial activity against both types of bacteria which was durable till 50 washes.     

Physical properties of estolides and their ester derivatives

Vegetable oil based lubricants have good lubricity and biodegradability but often fail to meet viscosity requirements at cold temperatures. These properties for a lubricant are often evaluated by pour point (PP), the minimum temperature at which a liquid will pour. Viscosity and viscosity index also provide information about a fluid's properties where a high viscosity index denotes a fluid that has little viscosity change over a wide temperature range. In order to develop better quality vegetable based lubricants, pour point, melting point and viscosity (40 and 100°C) were determined for a series of esters (methyl, butyl, decyl, oleyl, 2-propyl, 2-ethylhexyl, C18-Guerbet and C24-Guerbet) of meadowfoam, crambe and oleic fatty acids and estolides. Oleic estolide esters had the lowest melting points of all derivatives studied. Of the oleic estolide series the 2-ethylhexyl and C18-Guerbet esters had the lowest melting points, −34 and −43°C, respectively. Similar melting point trends within the series of esters were observed for both fatty acids and estolides. Pour points of the oleic estolides were also determined on a series of both free acid estolides and their 2-ethylhexyl esters. The series compared the effect of oligomerization on pour point. Pour points of oleic estolides were 5–10°C higher than the corresponding derivative's melting point. The extent of oligomerization (estolide number, EN) played a significant role in the pour point with higher oligomerization giving higher pour points (EN of 2.96 had a PP of 0°C; EN of 1.1 had a PP of −27°C). In a similar fashion, viscosity increased with higher oligomerization and free acid estolides were generally several hundred centistokes (cSt) more viscous than the corresponding esters. Viscosity index ranged from 151 to 238 with the fatty acid esters giving slightly higher indices than estolide esters. Hydrogenation of the estolides resulted in a dramatic increase in the pour point but only changed viscosity slightly.     

Eco-dyeing and antimicrobial properties of chlorophyllin copper complex extracted from Sasa veitchii

Cotton fabrics were dyed with the natural chlorophyll derivates (chlorophyllin, Chlin) after treatment with and without chitosan. The water-soluble Chlin extracted from Sasa veitchii based on Japanese bamboo leaves were investigated in order to improve the textile coloration and antimicrobial activity. The antimicrobial activity of the dyed fabrics that had been pretreated with chitosan as a biomordant over a concentration range of 0∼0.7 % was tested against two common gram pathogens: Staphylococcus aureus and Klebsiella pneumoniae. The color depth as measured by the K/S value, the color difference and the colorfastness to washing and light were also evaluated. The fabrics treated with chitosan resulted in an increase in dye uptake in all cases compared with the corresponding untreated fabrics, and did not affect fastness of washing and light. The cotton fabrics dyed with mordant and CuSO₄ extracts appeared to have over 99.9 % of antimicrobial activity, while MeOH extracts showed 71.8 %.     

Investigations on C-glycosyl flavonoids from Rhynchosia capitata,its antimicrobial and dyeing properties

Natural dyes extracted from a novel source Rhynchosia capitata (R. capitata) Heyne ex roth were applied to cotton fabric by applying traditional and pad dyeing processes using pre-, post- and simultaneous-mordanting techniques. Both dyeing processes were carried out in the presence of natural mordants: Myrobalan, Pomegranate rind, Rhizhophora mucronata fruits, Manjistha, and eco-friendly metallic mordants such as tannic acid, stannous chloride (SnCl₂), ferrous sulfate (FeSO₄), and copper sulfate (CuSO₄). The range of color developed on dyed materials was evaluated in terms of (L*, a*, b*, C*) CIELAB coordinates and dye absorption concentration on textile materials was studied by using K/S values. Natural mordant Rhizhopora mucronata fruits exhibited good absorption value. It was found that metallic mordants FeSO₄ and CuSO₄ exhibited higher K/S values than SnCl₂. For other mordants except FeSO₄ shade developed on cotton fabric varied from pale yellow to brown. The fastness properties ranged from good to excellent. High pressure thin layer chromatographic analysis for solvents of varying polarity has been investigated and maximum yield was obtained from 80 % aqueous ethanol fraction. Antimicrobial activity was carried out with the aid of two human pathogenic strains, Staphylococcus aureus and Klebsiella pneumonia and the cotton fabric dyed with plain extract of R. capitata shows good activity.     

Preparation of starch-based polyurethane films and their mechanical properties

In this study, polyurethane films were prepared using starch as the main polyol component, and the mechanical properties of these films were investigated. The starch content of the polyols was 30–50 wt%. To confirm the formation of a urethane linkage between the −OH of starch and −NCO of toluene 2,4-diisocyanate, Fourier transform infrared (FT-IR) spectroscopic analysis was performed. Differential scanning calorimetry (DSC) thermograms of the polyurethanes resulted in two endothermic peaks, which shifted to higher temperatures with increasing starch content and −NCO/−OH molar ratio. Due to the melting behavior of polyurethane, films could be prepared by hot pressing at an appropriate temperature. Polyurethane films were prepared with various polyol starch content and −NCO/−OH molar ratios. Tensile testing indicated that the breaking stress and elastic modulus increased significantly with starch content and −NCO/−OH molar ratio. In addition, bending tests indicated an increase in breaking stress and bending modulus with starch content and −NCO/−OH molar ratio and decreased breaking strain. The strain rate in both tensile and bending tests had a significant effect on the mechanical properties.     

Azocalix[4]pyrrole dyes: Application in dyeing of fibers and their antimicrobial activity

The dyeing performance of the azocalix[4]pyrrole dyes on fibers like nylon, wool, acrylic, and silk have been determined. Their fastness properties towards light, water, washing, and acid-alkali perspiration have been studied. The position of color in CIELAB coordinates (L*, a*, b*, H, and C*) was assessed. The azocalix[4]pyrrole demonstrated good antimicrobial activity against Escherichia coli, Staphylococcus aureus, and Aspergillus niger. These super molecules exhibit bright shades on fabric with very good fastness properties.     

Effect of thermal annealing on mechanical properties of polyelectrolyte complex nanofiber membranes

Optimization of mechanical properties is required in the applications of tissue-engineered scaffolds. Thermal annealing strategy is proposed to improve the mechanical properties of polyelectrolyte complex nanofiber membranes. The effects of annealing on the structural and mechanical properties of electrospun chitosan-gelatin (CG) nanofiber membranes were investigated using tensile tests, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and differential scanning calorimetry (DSC). Tensile test results showed that annealing processing at 90 °C produced 1.3-fold and 1.1-fold increase on Young’s modulus and tensile strength, respectively. By scanning electron microscopy (SEM) observation, it was found there was a formation of partial interfiber bonding when annealing temperature was elevated over the glass transition temperature (T _g ) of CG nanofibers. FTIR results showed enhanced molecular interactions within fibers, suggesting that annealing treatment promoted the conjunction between chitosan and gelatin. In contrast, no detectable changes in crystallinity for CG nanofiber specimens were exhibited on XRD patterns following annealing treatment. In addition, thermal annealing induced the improvement in thermal stability, aqueous stability and swelling capacity. Therefore, annealing is proved to be an effective strategy for mechanical enhancement of polyelectrolyte complex nanofibrous scaffolds. The enhanced stiffness and strength is mainly attributed to the formation of interfiber bonding and strengthened molecular interactions between chitosan and gelatin.     

Surface-modified nanofibrous biomaterial bridge for the enhancement and control of neurite outgrowth

Biomaterial bridges constructed from electrospun fibers offer a promising alternative to traditional nerve tissue regeneration substrates. Aligned and unaligned polycaprolactone (PCL) electrospun fibers were prepared and functionalized with the extracellular matrix proteins collagen and laminin using covalent and physical adsorption attachment chemistries. The effect of the protein modified and native PCL nanofiber scaffolds on cell proliferation, neurite outgrowth rate, and orientation was examined with neuronlike PC12 cells. All protein modified scaffolds showed enhanced cellular adhesion and neurite outgrowth compared to unmodified PCL scaffolds. Neurite orientation was found to be in near perfect alignment with the fiber axis for cells grown on aligned fibers, with difference angles of less than 7° from the fiber axis, regardless of the surface chemistry. The bioavailability of PCL fibers with covalently attached laminin was found to be identical to that of PCL fibers with physically adsorbed laminin, indicating that the covalent chemistry did not change the protein conformation into a less active form and the covalent attachment of protein is a suitable method for enhancing the biocompatibility of tissue engineering scaffolds.