Tanja Pivec

Novel cellulose based materials for safe and efficient wound treatment.

The present study aims at achieving effects of improved hydrophilicity and microorganism inhibition, which are rarely simultaneously present in wound dressings. Viscose fibers in their non-woven form were modified using two different pathways. Effects of a two-step procedure, i.e. alkaline or oxygen plasma treatment followed by the attachment of silver chloride nanoparticles were compared to a one-step procedure, i.e. ammonium plasma treatment, which results in both desired material characteristics simultaneously. The surface properties of untreated and differently modified cellulose samples were analyzed by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), in vitro silver release, and hydrophilicity measurements. The treatment effect on antimicrobial activity was determined by the AATCC 100-1999 standard test. In light of the introduced wound dressing preparation procedures and the desired wound dressing characteristics, the effectiveness of the used procedures was evaluated. Antimicrobial activity was proven against all Gram negative bacteria, while the Gram positive bacteria survive the as-prepared samples. Hydrophilicity was proven to be excellent using both preparation procedures. The mentioned results prove the potential of the used procedures and encourage future developments toward the clinical proof of concept.

In situ preparation of silver nanocomposites on cellulosic fibers – Microwave vs. conventional heating

A green approach for the preparation of silver nanocomposites on viscose fibers using microwave and conventional heating is presented. Reduction of silver nitrate is induced by addition of 6-O chitosan sulfate (S-Chi) in aqueous media which provides steric protection and electrostatic stabilization to prevent agglomeration of the nanoparticles. The particles are formed in close spatial proximity to the fibers and adsorption of the particles via structural similarity takes place to create silver nanocomposites. All nanocomposites have been subjected to antimicrobial tests and high antimicrobial activity toward Escherichia coli bacteria has been determined. Further, the nanocomposites are characterized using different analytical techniques which reveal very similar results for both heating techniques. The only significant difference is observed concerning the shape of the nanoparticles on the viscose fibers which are slightly elongated for the microwave method in comparison to spheres observed by conventional heating. Therefore, detailed investigations on the formation of colloidal silver nanoparticles have been performed, comparing microwave dielectric and conventional heating at the exact same temperature and reaction times. These experiments resulted in nearly identical nanoparticle shape and size for both heating methods as demonstrated by dynamic light scattering, UV-vis spectroscopy and transmission electron microscopy. A wide range of parameters has been varied (temperature, AgNO3 to S-Chi ratio, reaction time, and stirring speed) to study the nanoparticle formation under microwave and conventional conditions. No evidence for the existence of so-called specific microwave effects was obtained.

Modification of cellulose non-woven substrates for preparation of modern wound dressings

Different ways are presented of modifying cellulosic non-woven substrates, which can serve as potential wound dressings with satisfactory antimicrobial and hydrophilic properties. For safe attachment of silver particles without a measurable release from the used materials, a sol–gel derived process was used. Alkaline and oxygen plasma treatments were used to improve the hydrophilicity of the materials. Their efficiency was determined by measuring contact angles and water retention values. Scanning electron microscopy (SEM) was used for determination of sample morphology prior to and after treatment. The efficiency of silver attachment and activity was evaluated by in vitro release studies and antimicrobial tests. Atomic force microscopy (AFM) and SEM, combined with dynamic light scattering, were used for determination of silver particle size. Additionally, we evaluated the influence of treatment on technological parameters, important for application performance, i.e. mechanical properties and air permeability.

Advanced Wound Care

The world is ageing rapidly. The percentage of older people (aged 60 years and over) worldwide increased from 9.2 % in 1990 to 11.7 % in 2013, and will reach 21.1 % by 2050 (Wound Management in An

Other Solutions to Achieve Desired Wound Healing Characteristics

18.5 billion+ worldwide market in 2021, 2015 [1]). That means the number of elderly is expected to more than double, from 841 million people in 2013 to more than 2 billion in 2050 (Fig. 1a). The ageing is connected strongly with the higher incidence of wounds. Exponential growth of older people is, therefore, parallel, followed by exponential growth of the wound management market (Fig. 1b).

Tissue Engineering Products

The variety of wound types has resulted in a wide range of wound care approaches, which are fast developing due to numerous researches. The integration of technological advances with understanding of the complex cellular and biochemical mechanisms of wound healing has led to the development of various advanced wound healing modalities, such as bioengineered skin and tissue equivalents, Negative Pressure Wound Therapy (NPWT), use of plasma, photochemical tissue bonding, electroactive material and hyperbaric oxygen therapy.

Safety and Efficiency Testing

The importance and demand for relatively cheap and available skin-replacement products encouraged many research groups worldwide to focus on creating biomaterials for skin substitution [1]. Engineered tissues that not only close wounds, but also stimulate the regeneration of the dermis, would provide a significant benefit in human wound healing [2].

Polysaccharide Based Wound Care Materials

The biocompatibility/cytotoxicity of materials intended for biomedical applications are always of utter importance (Danoux et al. in Acta Mater 17:1–15, 2015 [1], Yan et al. in Acta Biomater 12:227–241, 2015 [2]) Although the main objective of such testing is mostly related to assessment of the respective material safety and efficiency, functional testing of materials in relation to their targeted use is also needed to be considered. The main objective of the approach towards such testing is, therefore, not only related to the assessment of the specific materials’ biocompatibility with desired cells, but also the execution of the test as similar to the physiological application as possible (Naranda et al. in Sci Rep 6:28695, 2016 [3], Finsgar et al. in Sci Rep 6:26653, 2016 [4]). Related to this, the effect of possibly released toxic degradation products that could hinder cell growth can be determined, as well as possible local overdoses of respective drugs, which are often part of tested formulations, could be assessed, since these could also potentially harm the growing cells (Finsgar et al. in Sci Rep 6:26653, 2016[4]). Another related testing approach is to determine the respective formulation influence on the cell growth in comparison with different control samples (Naranda et al. in Sci Rep 6:28695, 2016 [3], Gradisnik et al. in Global Spine J 6:WST014, 2016 [5], Velnar et al. in Global Spine J 6:WST019, 2016 [6]). The following chapter will, therefore, be composed of two main parts. The first will review briefly some of the most used testing approaches in general (mostly according to the related ISO Standard—ISO 10993), while the second part will review and describe some of possible modifications of such standard approaches to get the best possible overview of the respective materials’ safety and efficiency for a specific purpose.

Emerging Techniques in the Preparation of Wound Care Products

Polysaccharides are finding an increasing number of applications in medical and pharmaceutical fields thanks to their biodegradability, biocompatibility, and, in some cases, bioactivity (Liu et al. in Cellulose 23:3129–3143, 2016 [1]). Since they also play an important role in the field of Wound Healing, the second chapter will be dedicated entirely to them.

Active Substances for Acceleration of Wound Healing

Numerous methods have been utilised to fabricate scaffolds with varying mechanical properties, suitable also to be used in wound care, for instance, conventional techniques, which include solvent casting and particle leaching, freeze-drying, thermally induced phase separation, gas foaming, and the sol–gel technique [1].