Alessio Varesano

Electrospun Porous Mats for High Efficiency Filtration

Submicron size fibers (so-called nanofibers) are easily produced with an electrospinning apparatus from polymer solutions of poly(ethylene oxide), poly(vinyl alcohol), and polyamide-6. Electrospinning seems the most powerful tool for fabricating polymer nanofibers. Fibers were directly deposited in the form of random fiber webs with high area-to-volume ratio and small porous size on ordinary nonwoven filters of PET microfibers. Morphology and diameter distribution of the electrospun filaments were characterized by SEM investigations. The flow resistance of the produced composite filters are evaluated by means of air permeability measurements. The electrospun fibers have diameters ranging from about 70—500 nm and are interconnected each other to form thin webs that have very small pore size. After the electrospinning treatment, the air permeability of the filter media decreases 6—17 times showing a significant change of flow resistance that can be controlled by the thickness of nanofibers layer and the pore size. High efficiency nano-microfibers composite filters could be used in a wide range of applications, ranging from air cleaning for automotive to environment conditioning or liquid filtration.

Improving Electrical Performances of Wool Textiles: Synthesis of Conducting Polypyrrole on the Fiber Surface

Antistatic treatments lower the electrical resistivity of textiles and facilitate charge dissipation avoiding high potential electrical discharges. Moreover, low surface resistivity gives textiles electro-conducting, soil release, thermal and electromagnetic shielding properties. A new way of producing electrically conducting textiles consists of treatments with organic conducting polymers. Unfortunately, conducting polymers have a low level of processability because of their poor mechanical and physical properties. These problems have been overcome by simple in situ depositions of conducting polymers on different substrates in order to produce composite materials with good mechanical properties. Polypyrrole (PPy) is one of the most promising candidates because it exhibits high conductivity and good environmental stability. In situ PPy synthesis on wool and on other animal fibers is presented in this work. A preliminary oxidative treatment (e.g. shrink-proofing, bleaching or depigmentation) improves the electrical properties of the resulting conductive composite textiles significantly.

Antibacterial efficacy of polypyrrole in textile applications

This paper describes application and evaluation of polypyrrole as an antibacterial polymer. Polypyrrole was produced embedding two doping agents: chloride and dicyclohexyl sulfosuccinate ions. Stability of the antibacterial efficacy of polypyrrole deposited on cotton fabrics was assessed before and after three different kinds of washing (namely, laundering with anionic and non-ionic detergents and dry-cleaning). Polypyrrole showed excellent antibacterial properties (100 % of bacterial reduction) against Escherichia coli for both doping agents. Treated fabrics were further characterised by scanning electron microscopy, energy dispersive X-ray analysis and infrared spectroscopy. The antibacterial efficacy diminished after launderings with anionic and non-ionic detergents because of two different mechanisms: the neutralisation of positive charges under alkali conditions (dedoping), and a partial removal of polypyrrole by abrasion and surfactant action. After dry-cleaning, polypyrrole embedding chloride and dicyclohexyl sulfosuccinate ions still showed excellent antibacterial efficacy. Moreover, scanning electron microscopy investigations were used to intuitively explain the bactericidal mechanism of polypyrrole on Escherichia coli bacteria.

FT-IR study of dopant-wool interactions during PPy deposition

Coating the fibre surface byin situ oxidative chemical polymerisation of polypyrrole (using FeCl3 as oxidant) is a readily industrial applicable way to give electrical properties to wool with good ageing stability [1], although pre-treatments are required to avoid damage of the cuticle surface due to the acidic condition of the process. FT-IR and EDX analysis reveal that organic sulphonates and sulphates, used as dopants, are absorbed by wool, while chlorine ions are preferably embedded on the polypyrrole layer. The resulting electrical conductivity seems mainly due to the presence of chlorine as counter-ion of polypyrrole; nevertheless, the presence of arylsulphonate in the polymerisation bath increases the electrical conductivity of the coating layer.

Chitosan coated cotton gauze for antibacterial water filtration

Communicable diseases can be transmitted by contaminated water. Water decontamination process is fundamental to eliminate microorganisms. In this work, cotton gauzes were coated with chitosan using an UV-curing process or cationized by introduction of quaternary ammonium groups and tested, in static and dynamic conditions, as water filter for biological disinfection against both Gram-negative and Gram-positive bacteria. Both materials showed good antibacterial activity, in static assessment, instead in dynamic conditions, chitosan treated gauze showed a high antimicrobial efficiency in few seconds of contact time. This composite could be a good candidate for application as biological filter.

Keratin-based Nanofibres

The interest in biopolymers from renewable resources as alternatives to polymers made from oil and other fossil resources has been increasing over the years. Biopolymers are also considered environmentally friendly over their entire live-cycle. There is much recent literature on carbohydrates and proteins derived from plants and animals and polyesters made from the fermentation of plant material. As to whether it is ethically justifiable to convert valuable foodstuffs into commodities is open to question. The focus here is on keratin, one of the most abundant and mostly unexploited non-food proteins, being the major component of hair, feathers, nails and horns of mammals and birds. In spite of their important and interesting characteristics keratin wastes represent a rather complicated disposal challenge because burning for fuel is inefficient and polluting due to the high sulphur content (3-4% wt). The total amount of keratin (including fibre by-products from the wool textile industry, poor quality raw wools from farms and butchery waste) has been estimated worldwide at more than 5 million tonnes per year (Barone et al., 2005). Ground horn and nail is used as a nitrogenous fertilizer for gardening and, more recently, has been processed by caustic hydrolysis to produce biodegradable surfactants for fire extinguisher foams. However, most keratin wastes made from unserviceable wools and feathers from poultry are not valorised and are simply disposed of (Martinez-Hernandez et al., 2007; Schmidt, 1998). Pooling and processing into biopolymers might be a better way of exploiting such a large quantity of protein biomass. Keratin-based materials can be used in biotechnological and biomedical fields for tissue engineering and the production of affinity membranes, due to their biocompatibility, their ability to support fibroblast growth and absorb heavy metal ions and volatile organic compounds (VOCs). Transforming keratin into nanofibres by electrospinning combines the aforementioned properties of keratin with the high surface to volume ratio and the high porosity of nano-structured textiles. This may be an original and promising approach for the fabrication of scaffolds for tissue engineering and filtration devices. Keratin distinguishes itself from other structural proteins by the quantity of cysteine residues in the protein molecules (7-20% of the total amino acid residues). In particular, cysteine amino acids form inter and intra molecular disulphide bonds (cysteine residues) giving rise to a compact three-dimensional structure that confers a high stability to the protein (Dowling et al., 1986). Because of their low molecular weight (9–60 kDa), keratin-based materials have poor mechanical properties. Moreover, like most natural polymers, keratin is not thermoplastic. For electrospinning keratin should be blended with suitable polymers using common,

Nanogrooves and keratin nanofibers on titanium surfaces aimed at driving gingival fibroblasts alignment and proliferation without increasing bacterial adhesion

Periimplantitis and epithelial downgrowth are nowadays the main conditions associated to transmucosal dental implants. Gingival fibroblasts can play an important role in periimplantitis because they are the promoters of the inflammatory process and eventual tissue homeostasis and destruction. Moreover, the related inflammatory state is commonly driven also to counteract bacteria implants colonization. In the present research, a new technology based on mechanically produced nanogrooves (0.1-0.2μm) and keratin nanofibers deposited by electrospinning has been proposed in order to obtain titanium surfaces able to drive gingival fibroblasts alignment and proliferation without increasing bacterial adhesion. The prepared surfaces have been characterized for their morphology (FESEM), chemical composition (FTIR, XPS), surface charge (zeta potential) and wettability (contact angle). Afterwards, their performances in terms of cells (human primary gingival fibroblasts) and bacteria (Staphylococcus aureus) adhesion were compared to mirror-like polished titanium surfaces. Results revealed that gingival fibroblasts viability was not negatively affected by the applied surface roughness or by keratin nanofibers. On the opposite, cells adhesion and spread were strongly influenced by surface roughness revealing a significant cell orientation along the produced nanogrooves. However, the keratin influence was clearly predominant with respect to surface topography, thus leading to increased cells proliferation on the surfaces with nanofibers, disregarding the presence of the surfaces grooves. Moreover, nor nanogrooves nor keratin nanofibers increase bacterial biofilm adhesion in comparison with mirror polished surfaces. Thus, the present research represents a promising innovative strategy and technology for a surface modification finalized to match the main requirements for transmucosal dental implants.

Electrospinning of polyamide 6/modified-keratin blends

Abstract Protein material resulting from chemical free steam explosion of wool was mixed in different proportion with polyamide 6 in formic acid. The viscosity of the blend solutions decreases with the increase of the protein amount in the blend. Nanofibres produced by electrospinning of these polymer blends show an increase of the filament diameters with increasing protein amounts, except for the 30/70 v/v polyamide 6/protein blend, where nanofibres with “beads” defects were produced. In blend films produced by casting, polyamide 6 crystallize in the form of large spherulites prevalently in the α crystalline structure, while protein is totally amorphous and tends to segregate in the course of drying at room temperature. Otherwise, in electrospun nanofibres polyamide 6 and protein show a better miscibility as suggested by spectroscopic and thermal analysis and polyamide 6 shows a higher thermal stability. Moisture regain and water solubility of blend cast films and electrospun nanofibres respectively were also determined.

Electrical performance and stability of polypyrrole coated PET fibres

Abstract PET non-wovens were treated with intrinsically electro-conducting polypyrrole (PPy) produced by chemical oxidative in situ polymerization from pyrrole aqueous solution, using Fe3+ or S2O82- as oxidant, and different dopants. The resulting materials have different electrical performances and thermal properties depending on the thickness of the PPy coating, the amount and the type of dopant embedded into the polymer layer, the type of oxidant used and the pH of the polymerization bath. Samples were maintained at different temperatures and humidity with the aim of gathering information about the electrical performance stability in different environmental conditions. Generally, PPy shows conductivity decay when maintained at high temperature, whereas the conductivity slightly decreases when stored for a long time at cold or room temperature. Moreover, the PPy coating enhances the resistance to heat of the PET fibres (i.e. increase in melting temperature).

Differential scanning calorimetry for the identification of animal hair fibres

Differential scanning calorimetry (DSC) was studied as an alternative qualitative method to identify different textile animal hair fibres. Differentiation of speciality or luxury fibres (such as cashmere) from other animal cheaper fibres (such as sheep’s wool or yak) is essential to repress adulteration of textile products. Moreover, DSC analysis can be used to distinguish fibres of different types and affected by industrial textile treatments like bleaching, steaming, descaling and stretching. Cashmere, wool, yak and goat fibres were analysed by DSC and their traces were compared. The traces were mathematically elaborated to establish criteria for fibres identification. These criteria were applied to study changes in the fibre traces due to industrial treatment. Differences in the DSC traces are evident from cashmere, yak, wool and goat due to differences in transition enthalpy and temperature of the crystalline material that constitutes the ortho- and para-cortex of animal hairs. Furthermore, it is possible to see changes in traces of the same fibres subjected to different treatments.