Preparation of metal-containing protein fibers and their antimicrobial properties

Prewetting Electron Beam Irradiated and Native Sheep Wool Can Affect Their Sorptivity

In this work, the effect of prewetting native and electron beam-modified wool on the resulting sorption of Cu(II) from wool solutions was studied. The following conditions and combinations were applied: 6 mM and 50 mM solutions, prewetting time 0-24 h, contact time 1-24 h. The sorption results showed that wetting the wool before sorption from the low concentrated solution can fundamentally improve the efficiency of the separation process. The opposite result was achieved when applying a more concentrated solution; that is, prewetting slightly reduced the sorptivity. The reasons for such results are discussed. The application of these findings can be used to optimize the separation process in technological practice, however, will require solute specification.

Insights into the Applications of Natural Fibers to Metal Separation from Aqueous Solutions

There is a wide range of renewable materials with attractive prospects for the development of green technologies for the removal and recovery of metals from aqueous streams. A special category among them are natural fibers of biological origin, which combine remarkable biosorption properties with the adaptability of useful forms for cleanup and recycling purposes. To support the efficient exploitation of these advantages, this article reviews the current state of research on the potential and real applications of natural cellulosic and protein fibers as biosorbents for the sequestration of metals from aqueous solutions. The discussion on the scientific literature reports is made in sections that consider the classification and characterization of natural fibers and the analysis of performances of lignocellulosic biofibers and wool, silk, and human hair waste fibers to the metal uptake from diluted aqueous solutions. Finally, future research directions are recommended. Compared to other reviews, this work debates, systematizes, and correlates the available data on the metal biosorption on plant and protein biofibers, under non-competitive and competitive conditions, from synthetic, simulated, and real solutions, providing a deep insight into the biosorbents based on both types of eco-friendly fibers.

A New Trend and Future Perspectives of the Miniaturization of Conventional Extraction Methods for Elemental Analysis in Different Real Samples: A Review

Sample preparation is one of the viable procedures to be used before analysis to enhance sensitivity and reduce the matrix effect. The current review is mainly emphasized the latest outcome and applications of microextraction techniques based on the miniaturization of the classical conventional methods based on liquid-phase and solid-phase extraction for the quantitative elemental analysis in different real samples. The limitation of the conventional sample preparation methods (liquid and solid phase extraction) has been overcome by developing a new way of reducing size as compared with the conventional system through the miniaturization approach. Miniaturization of the sample preparation techniques has received extensive attention due to its extraction at microlevels, speedy, economical, eco-friendly, and high extraction capability. The growing demand for speedy, economically feasible, and environmentally sound analytical approaches is the main intention to upgrade the conventional procedures apply for sample preparation in environmental investigation. A growing trend of research has been perceived to quantify the trace for elemental analysis in different natures of real samples. This review also recapitulates the current futuristic scenarios for the green and economically viable procedure with special overemphasis and concentrates on eco-friendly miniaturized sample-preparation techniques such as liquid-phase microextraction (LPME) and solid-phase microextraction (SPME). This review also emphasizes the latest progress and applications of the LPME and SPME approach and their future perspective.

Graphene oxide-silver nanocomposites embedded nanofiber core-spun yarns for durable antibacterial textiles

Antibacterial textiles, which effectively inhibit bacterial breeding and resist pathogenic diseases, have wide applications in medicine, hygiene, and related fields. However, traditional antibacterial textiles exhibit significant limitations, such as poor antibacterial durability and contamination during preparation. In this work, nanofiber yarn loaded with a high-efficiency antibacterial agent was prepared using electrospinning technology. Polyethyleneimine (PEI) was introduced as a solubilizing material to functionalize graphene oxide (GO) to form GO-PEI composites. A facile microwave heating method was used to synthesize GO-PEI and silver nanoparticles (AgNPs). A multi-needle conjugated electrospinning device was used to blend the nanofibers with the GO-PEI-Ag composite to form a nanofiber core-spun yarn. The antibacterial agent was firmly fixed on the fiber to prevent easy removal. A uniformly oriented yarn structure and internal morphology were observed, and the antibacterial activity of the fabric was measured. The antibacterial rate of the fabric was over 99.99%for both Escherichia coli and Staphylococcus aureus. After ten washes, the antibacterial rate remained above 99.99%. Thus, nanofiber fabric from electrospinning displays high antibacterial activity and excellent durability, thereby providing a feasible methodology for future production of antibacterial textiles.

Influence of organic solvents on the structural and thermal characteristics of silk protein from the web of Orthaga exvinacea Hampson (Lepidoptera: Pyralidae)

The silk protein from the web of Orthaga exvinacea was isolated, purified, and casted into films. This film was treated separately with methanol, acetone, ethyl acetate, and isopropyl alcohol in 50 % concentration for about 30 min. The treated films were thus dried in a desiccator and subjected to FTIR and TG-DTA analysis. The structural studies revealed that the organic solvents induce conformatory changes in the protein film, especially the most sensitive amide I (1650 cm^-1) band. This band had shifted to lower wavenumber (1633-1636 cm^-1). Furthermore, the conformatory characteristics associated with amide I band also changed from random coil to β-sheet. Generally, β-sheet contributes strength to the protein film. Among the treated films, film treated with acetone showed much thermal stability. Moreover, the film treated with methanol had shown two different temperatures of maximum degradation. It is concluded that in addition to β-sheet content, various other factors such as various processing conditions and structural organization of protein may influence the stability of the films.

Fibrous proteins: At the crossroads of genetic engineering and biotechnological applications

Fibrous proteins, such as silk, elastin and collagen are finding broad impact in biomaterial systems for a range of biomedical and industrial applications. Some of the key advantages of biosynthetic fibrous proteins compared to synthetic polymers include the tailorability of sequence, protein size, degradation pattern, and mechanical properties. Recombinant DNA production and precise control over genetic sequence of these proteins allows expansion and fine tuning of material properties to meet the needs for specific applications. We review current approaches in the design, cloning, and expression of fibrous proteins, with a focus on strategies utilized to meet the challenges of repetitive fibrous protein production. We discuss recent advances in understanding the fundamental basis of structure-function relationships and the designs that foster fibrous protein self-assembly towards predictable architectures and properties for a range of applications. We highlight the potential of functionalization through genetic engineering to design fibrous protein systems for biotechnological and biomedical applications.

Chelating materials immobilizing carboxymethylated pentaethylenehexamine and polyethyleneimine as ligands

This article presents an overview of our recent progress on the development of chelating materials. Carboxymethylated pentaethylenehexamine (CM-PEHA) and polyethyleneimine (CM-PEI) as chelating ligands show excellent performance for the solid-phase extraction of trace elements. Chelating resins immobilizing these ligands can be readily prepared by immobilizing PEHA and PEI on methacrylate resins and then carboxymethylating them. Chelating fiber can also be prepared with a wet spinning technique using a mixture of a viscose solution and a solution containing fine particulate CM-PEHA resin or CM-PEI. The potentials of these chelating materials for the separation and preconcentration of trace elements are outlined.

Salicylic acid and some of its derivatives as antibacterial agents for viscose fabric

Salicylic acid and three of its derivatives were used to provide antibacterial properties to viscose fabrics. The four bactericides used were bonded to the viscose fabrics using epichlorohydrin or polymer binders. Optimization of the salicylic acid and its derivatives as well as the concentration of polymers was reported. The ability of the polymer binders to attract and bind the four bactericides was observed. The overall results show that the antibacterial reactivity of salicylic acid and its derivatives are in the following order 5-bromosalicylic acid>salicylic acid>5-chlorosalicylic acid>4-chlorosalicylic acid. Using epichlorohydrin as a binding agent, unfortunately, inhibits the bactericidal activity of the four bactericides. The FTIR study concludes that the reaction between salicylic acid as well as its derivatives with epichlorohydrin takes place through the phenolic group of the acids. The unexpected deterioration in the bactericidal properties of salicylic acid and its derivatives as a result of the treatment with epichlorohydrin could be due to the nature of interaction between the epichlorohydrin molecule and the acids molecules. PVP and PU show superior ability to sustain the four bactericides used even after 10 washing cycles.

Sporicidal/bactericidal textiles via the chlorination of silk

Bacterial spores, such as those of the Bacillus genus, are extremely resilient, being able to germinate into metabolically active cells after withstanding harsh environmental conditions or aggressive chemical treatments. The toughness of the bacterial spore in combination with the use of spores, such as those of Bacillus anthracis, as a biological warfare agent necessitates the development of new antimicrobial textiles. In this work, a route to the production of fabrics that kill bacterial spores and cells within minutes of exposure is described. Utilizing this facile process, unmodified silk cloth is reacted with a diluted bleach solution, rinsed with water, and dried. The chlorination of silk was explored under basic (pH 11) and slightly acidic (pH 5) conditions. Chloramine-silk textiles prepared in acidified bleach solutions were found to have superior breaking strength and higher oxidative Cl contents than those prepared under caustic conditions. Silk cloth chlorinated for ≥1 h at pH 5 was determined to induce >99.99996% reduction in the colony forming units of Escherichia coli, as well as Bacillus thuringiensis Al Hakam (B. anthracis simulant) spores and cells within 10 min of contact. The processing conditions presented for silk fabric in this study are highly expeditionary, allowing for the on-site production of protein-based antimicrobial materials from a variety of agriculturally produced feed-stocks.

Chelating fibers prepared with a wet spinning technique using a mixture of a viscose solution and a polymer ligand for the separation of metal ions in an aqueous solution

Chelating fibers containing polymer ligands such as carboxymethylated polyallylamine, carboxymethylated polyethyleneimine, and a copolymer of diallylamine hydrochloride/maleic acid were prepared with a wet spinning technique using mixtures of a viscose solution and the polymer ligands. The chelating fibers obtained effectively adsorbed various metal ions, including Cd(II), Co(II), Cr(III), Cu(II), Fe(III), Mn(II), Ni(II), Pb(II), Ti(IV), and Zn(II). The metal ions adsorbed could be readily desorbed using 0.1 or 0.5 mol L(-1) HNO(3). The chelating fiber containing carboxymethylated polyallylamine was available for the separation of some metal ions in synthetic wastewater containing a large amount of Na(2)SO(4). The wet spinning technique using a solution containing a base polymer and a polymer ligand was quite simple and effective and would be applicable for preparing various chelating fibers.

Preparation and characterization of chelating fibers based on natural wool for removal of Hg(II), Cu(II) and Co(II) metal ions from aqueous solutions

The graft copolymerization of acrylonitrile (AN) onto natural wool fibers initiated by KMnO(4) and oxalic acid combined redox initiator system in limited aqueous medium was carried out in heterogeneous media. Moreover, modification of the grafted wool fibers was done by changing the nitrile group (-CN) into cyano-acetic acid α-amino-acrylic-hydrazide through the reaction with hydrazine hydrate followed by ethylcyanoacetate which eventually produce wool-grafted-poly(cyano-acetic acid α-amino-acrylic-hydrazide) (wool-g-PCAH) chelating fibers. The application of the modified fibers for metal ion uptake was studied using Hg(2+), Cu(2+) and Co(2+). The modified chelating fibers were characterized using FTIR spectroscopy, SEM and X-ray diffraction.

Antibacterial Nanofibers of Self-quaternized Block Copolymers of 4-Vinyl Pyridine and Pentachlorophenyl Acrylate

Well-defined antibacterial block copolymers of 4-vinyl pyridine (4VP) and pentachlorophenyl acrylate (PCPA) (P(4VP- b-PCPA)) were prepared via reversible addition—fragmentation chain transfer (RAFT) polymerization. Electrospinning of the P(4VP- b-PCPA) from a solution in mixed tetrahydrofuran and dimethylformamide gave rise to fibers with diameters in the range of 0.5—4.0 µm. The quaternary ammonium salts (QASs) were generated by N-alkylation of pyridine groups of P4VP block and chloro-aromatic compounds of PPCPA block (or self-quaternization of P(4VP- b-PCPA)). The self-quaternization of P(4VP- b-PCPA) nanofibers was studied by X-ray photoelectron spectroscopy. Attributable to the hydrophobicity of the PPCPA blocks and the electrostatic interaction of QASs generated from the self-quaternization of P(4VP- b-PCPA), the resulting nanofibers exhibit a high antibacterial efficiency. The antibacterial effect of the P(4VP- b-PCPA) nanofibers was assayed using Escherichia coli and Staphylococcus aureus cultures. It was found that 99.6% of E. coli and 99.1% S. aureus were killed after being in contact with 50 mg nanofibers in 10 min. The permanence of antibacterial activity of the self-quaternized P(4VP- b-PCPA) nanofibers was also demonstrated in repeat application.

Novel photonic crystals: incorporation of nano-CdS into the natural photonic crystals within peacock feathers

In this investigation, the natural 2D photonic crystals (PhCs) within peacock feathers are applied to incorporate CdS nanocrystallites. Peacock feathers are activated by ethylenediaminetetraacetic/dimethylformamide suspension to increase the reactive sites on the keratin component, on which CdS nanoparticles (nano-CdS) are in situ formed in succession and serve as the "seeds" to direct further incorporation during the following solvothermal procedure. Thus, homogeneous nano-CdS are loaded both on the feathers' surface layer and inside the 2D PhCs. The obtained nano-CdS/peacock feathers hybrids are novel photonic crystals whose photonic stop bands are markedly different from that of the natural PhCs within original peacock feathers, as observed by the reflection spectra.

Chemical and physical properties of sulfated silk fabrics

Silk fabrics were treated with chlorosulphonic acid in pyridine for different times. The amount of sulfur bound to silk increased during the first 2 h of reaction and then reached a plateau. The amino acidic pattern of sulfated silk remained essentially unchanged for short reaction times (< or =2 h). Longer reaction times resulted in drastic changes in the concentration of Asp, Glu, and Tyr. Surface morphology and texture of silk fabrics changed upon sulfation. Warp and weft yarns became progressively thinner, and deposits of foreign material appeared on the fiber surface. Changes were more evident at longer reaction times (> or =2 h). Spectroscopic analyses performed by FT-IR and FT-Raman showed the appearance of new bands attributable to various vibrations of sulfated groups. The IR bands at 1049 and 1014 cm-1, due to organic sulfate salts, were particularly intense. Bands assigned to alkyl sulfates and sulfonamides appeared in the 1300-1180 cm-1 range. Organic covalent sulfates displayed a weak but distinct IR band at 1385 cm-1. Both IR and Raman spectra revealed that silk fibroin mainly bound sulfates through the hydroxyl groups of Ser and Tyr, while involvement of amines could not be proved. Changes observed in the amide I and II range indicated an increase of the degree of molecular disorder of sulfated silk. Accordingly, the I850/I830 intensity ratio between the two Tyr bands at 850-830 cm-1 increased from 1.41 to 1.52, indicating a more exposed state of Tyr residues in sulfated silk. TGA, DSC, and TG analyses showed that sulfated silk attained a higher thermal stability. A thermal transition attributable to sulfated silk fibroin fractions appeared at about 260 degrees C in the DSC thermograms.

Tyrosinase-catalyzed modification of Bombyx mori silk fibroin: Grafting of chitosan under heterogeneous reaction conditions

The capability of mushroom tyrosinase to catalyze the oxidation of tyrosine residues of Bombyx mori silk fibroin was studied under heterogeneous reaction conditions, by using a series of silk substrates differing in surface and bulk morphology and structure, i.e. hydrated and insoluble gels, mechanically generated powder and fibre. Tyrosinase was able to oxidize 10-11% of the tyrosine residues of silk gels. The yield of the reaction was very low for the powder and undetectable for fibres. FT-Raman spectroscopy gave evidence of the oxidation reaction. New bands attributable to vibrations of oxidized tyrosine species (o-quinone) appeared, and the value of the I853/I829 intensity ratio of the tyrosine doublet changed following oxidation of tyrosine. The thermal behaviour of SF substrates was not affected by enzymatic oxidation. o-Quinones formed by tyrosinase onto gels and powder were able to undergo non-enzymatic coupling with chitosan. FT-IR and FT-Raman spectroscopy provided clear evidence of the formation of silk-chitosan bioconjugates under heterogeneous reaction conditions. Chitosan grafting caused a beta-sheet --> random coil conformational transition of silk fibroin and significant changes in the thermal behaviour. Chitosan grafting did not occur, or occurred at an undetectable level on silk fibres. The results reported in this study show the potential of the enzymatically initiated protein-polysaccharide grafting for the production of a new range of bio-based, environmentally friendly polymers.

Silver Bromide Nanoparticle/Polymer Composites: Dual Action Tunable Antimicrobial Materials

We present a simple method of fabricating highly potent dual action antibacterial composites consisting of a cationic polymer matrix and embedded silver bromide nanoparticles. A simple and novel technique of on-site precipitation of AgBr was used to synthesize the polymer/nanoparticle composites. The synthesized composites have potent antibacterial activity toward both gram-positive and gram-negative bacteria. The materials form good coatings on surfaces and kill both airborne and waterborne bacteria. Surfaces coated with these composites resist biofilm formation. These composites are different from other silver-containing antibacterial materials both in the ease of synthesis and in the use of a silver salt nanoparticle instead of elemental silver or complex silver compounds. We also demonstrate the ability to tune the release of biocidal Ag(+) ions from these composites by controlling the size of the embedded AgBr nanoparticles. These composites are potentially useful as antimicrobial coatings in a wide variety of biomedical and general use applications.