Manja Kurečič

Electrospun nanofibrous CMC/PEO as a part of an effective pain-relieving wound dressing

Abstract A novel two-layered pain-relieving wound dressing was prepared from a combination of biocompatible polymers: carboxymethylcellulose and polyethyleneoxide, and two types of pain-relieving drugs: the non-steroid anti-inflammatory diclofenac and the local anesthetic lidocaine. To achieve the two-layered structure, electrospinning and impregnation of a commercially available wound dressing Aquacel® were used for preparation of respective layers. The electrospun nanofibers have been shown to possess similar features as found in the extracellular matrix, an important component of the skin. This characteristic could significantly contribute to the efficiency of wound healing. The second layer is based on Aquacel®, an important wound dressing in modern wound care. Since pain can drastically lower the wound healing process, as well as it is known to decrease the overall quality of patient life, pain-relieving drugs are very interesting for wound care applications. For efficient pain reduction, two types of drugs were used. When combined, these can cover different types of wound-related pain (due to the cause and treatment) and hence additionally aid the wound healing process. The combined features of the incorporated pain-relieving drugs and the mentioned materials are therefore very interesting for future studies toward clinical testing of possible prototype products.Graphical Abstract

Layering of different materials to achieve optimal conditions for treatment of painful wounds

Despite a range of advanced wound dressings that can facilitate wound healing, there are still no clinically used dressings for effective local pain management. The latter was the main motivation of the present study. We designed a novel wound dressing with three layers. A macro-porous polyethylene terephthalate (PET) mesh with incorporated lidocaine, a fast-acting local anesthetic, was chosen as the layer in direct contact with the skin. Fast release from this layer enables an immediate pain relieving effect, caused by dressing changes. For the second and third layer, alginate and viscose were chosen respectively. A potential long-lasting pain relieving effect was achieved through incorporation of a nonsteroidal anti-inflammatory drug diclofenac into both layers. The chosen dressing structure enables also an unhindered absorption of the wound exudate, which is possible through the macro-porous PET into the alginate layer. Alginate additionally maintains a moist wound environment. Our novel wound dressing was systematically tested in regard of the structural (contact angle measurements, IR spectroscopy, SEM), functional (water retention, air permeability) properties and its biocompatibility (Live/Dead and MTT assays) towards human skin fibroblasts. Combined results confirmed the suitability of the chosen wound dressing composition for a faster and painless wound treatment.

Polymer Nanocomposite Hydrogels for Water Purification

Contamination of water, due to the discharge of untreated or partially treated industrial wastewaters into the ecosystem, has become a common problem for many countries [1]. In various productions, such as textiles, leather, rubber, paper, plastic and other industries, the dyeing processes are among the most polluting industrial processes because they produce enormous amounts of coloured wastewaters [2-4]. In addition to their colour, some of these dyes may degrade to highly toxic products, potentially carcinogenic, mutagenic and aller‐ genic for exposed organisms even at low concentrations (less than 1 ppm) [5]. They contami‐ nate not only the environment but also traverse through the entire food chain, leading to biomagnifications [6-9]. The removals of such compounds particularly at low concentrations are a difficult problem.

Bio-nanofibrous mats as potential delivering systems of natural substances

Considering the increasing resistance of numerous bacteria to antibiotics, a novel wound dressing material was developed with naturally acquired olive leaf extract, which shows not only good antimicrobial activity, but also very good antioxidant activity. Besides that, the leaves are treated as waste in agriculture, giving an impact on waste management. An environmentally friendly procedure, electrospinning, was used for the first time to prepare polysaccharide nanofibrous mats with incorporated olive leaf extract, with the unique property of releasing the active phenolic components in a prolonged manner over 24 hours. The developed electrospun mats were characterized using scanning electron microscopy, high-performance liquid chromatography and ultraviolet-visible spectroscopy for determination of free radical scavenging activity by 2,2-diphenyl-1-picrylhydrazyl, antimicrobial testing and release kinetics. Antimicrobial tests have shown that electrospun mats with olive leaf extract achieve reduction towards the tested microorganisms: Staphylococcus aureus (G+), Escherichia coli (G-), Enterococcus faecalis (G+) and Pseudomonas aeruginosa (G-), while the high antioxidant activity of olive leaf extract was preserved during the electrospinning procedure. Release of olive leaf extract from electrospun mats was mathematically modeled, and the release kinetics evaluation indicates the appropriateness of the Korsmeyer–Peppas model for fitting the obtained results of release ability due to erosion of polysaccharide nanofiber mats.

Alternative cleaning of compost leachate using biopolymer chitosan

Compost leachate poses a threat to the environment because it contains many organic and inorganic pollutants. Chemical Oxygen Demand (COD) has been reported at values above 5000 mg/l O2. Heavy metals, such as nickel, lead, chromium are also present within these waters. Thus, in order to comply with the increasingly stringent environmental quality standards such contaminants must be removed effectively. The research approach in this paper is directed towards chelating pre-treatment procedures. Nontoxic and biodegradable biopolymer chitosan was used as a chelator for the removal of dissolved metals from compost leachate. The influence of chemical conditions regarding the chelation efficiency was studied in model solutions. The optimal treatment conditions were applied onto compost leachate which was analysed further regarding metals. In addition, the influence of chitosan was studied on compost leachate toxicity. The most important aspect of this paper is to demonstrate the potential of waste chitosan recycling. Thus, the chitosan chelates were subjected to the electrospinning procedure in order to develop new nano-porous structures, such as, for example, conductive textiles.

Electrokinetic Properties of Nanocomposite Fibres

Nanocomposite fibres are becoming of great importance since organic–inorganic nanoscale composites frequently exhibit unexpected hybrid properties synergistically derived from the two components. The incorporation of one-, twoand three-dimensional nano particles, e.g. layered clays, nano-tubes, nano-fibres, metal containing nano-particles, carbon black, etc. is used to prepare nanocomposite fibres. However, the preparation of nanocomposite fibres offers several possibilities, i.e. creation of nanocomposite fibres by dispersing of nanoparticles into polymer solutions, the polymer melt blending of nanoparticles, in situ prepared nanoparticles within a fibre, the intercalative polymerization of the monomer, introduction of nanoparticles from dispersion into a porous polymer, preparation of nanocoatings by different techniques, e.g. sol-gel process, etc. With the respect to nanoparticles organization in / on fibres, respectively nanocoated fibres and fibres with nanoinclusions can be divided. Nanocomposite fibres demonstrate improved applicable properties, e.g. mechanical, flammability, electromagnetic, electro-conductive, sorption properties, and/ or obtain additional functional properties, like antimicrobial, self-cleaning, shielding, UV protective properties, etc. Combining polymer fibre and nanopaticles of different structures and characteristics influences also fibre’s surface properties, i.e. morphological properties and electrokinetic behaviour. In order to analyse fibre’s surface charge, the zeta potential is often determined through streaming potential measurements as a function of pH. These properties are generated by the electrochemical double layer (EDL), which exists at the phase boundary between a solid and a solution containing ionic moieties. By variation of the solution’s pH value and electrolyte content it is possible to estimate the acidic / basic and polar / nonpolar character of the solid surface from zeta potential data. Some examples of nanocomposite fibres (e.g. nanofilled PP fibres, SiO2 – nanocoated different types of fibres) regarding their electrokinetic properties are presented in the contribution. In addition to, the influence of nanocomposite fibres preparation procedure conditions on their zeta potential values is demonstrated.