Investigating the effect of processing parameters in the electrospinning of nanofibres

Nylon 6, Nylon 6.6, PEO/water, PEO/water/Ethanol, PVA/FeCl3 and PEO/wood pulp have been successfully electrospun into nanofibres in the range of 200 nm to 1500 nm. A comprehensive understanding of the effect of processing parameters on the morphological structure of these nanofibres has been established. Parameters such as concentration of polymer solution, applied voltage, electrospinning collection distance and flow rate have been found to affect fibre morphology. For Nylon 6 and Nylon 6.6 uniform nanofibres were produced using polymer solution concentrations, 20 wt.% and 25 wt.%, applied voltage of 15 kV, spinning distance of 8 cm and volume feed rate of 0.20 ml/hr. The produced nanofibres average diameter was 924 nm and 827 nm. For PEO/water, PEO/water/Ethanol and PEO/wood pulp optimum conditions of polymer solution concentration of 14 wt.% and 10 wt.%, an applied voltage of 15 kV, spinning collection distance of 11cm and volume feed rate of 0.20 ml/hr and 0.25 ml/hr, produced uniform nanofibres. The produced nanofibres average diameter was 452 nm, 544 nm and 494 nm. As for PVA/FeCl3, optimum conditions of polymer solution concentration of 8 wt.%, an applied voltage 15 kV, spinning collection distance 11 cm and flow rate 0.25 ml/hr produced uniform magnetic nanofibres. The produced nanofibres average diameters were 789 nm. These parameters have consequently been optimized to obtain uniform quality at different ranges of nanofibres. In this context it was established that the processing parameters vary significantly from one polymer to another but in general, the concentration the most important role in obtaining uniform fibre diameter without thin and thick places and beads. Applied voltage also played a significant role in determining the diameter of nanofibres and little significant effect on the fibre morphology was observed with the variation of spinning collection distance and noticeable structural change with a change in the solution flow rate. A selective range of microscopic techniques such as, Scanning Electron Microscopy, Atomic Force Microscopy and Transmission Electron Microscopy were used to characterise and evaluate the nanofibres produced during this study. DSC, X-ray diffraction and FTIR was used to identify the thermal properties of Nylon 6.6, PEO and PEO/wood pulp nanofibres produced. Nanofibres produced in this study have a wide range of potential applications in different fields, including, biomedical, magnetic sensor, mats for composite protective clothing, filtration, aerospace and others

Development and Characterization of Electrospun Wound Dressings Containing Birch Bark Extract

Ein effizientes und einfach zu handhabendes Wundmanagement ist immer noch eine große Herausforderung. In unserem täglichen Leben wäre es äußerst wünschenswert, einfache, akzeptable Verbandmaterialien zu haben, die einerseits direkt zur Abdeckung von Wunden und andererseits zur Beschleunigung der Wundheilung verwendet werden können. Ein Triterpentrockenextrakt (TE) aus der Birkenrinde kann nachgewiesenermaßen den Wundheilungsprozess beschleunigen. Daher war das Hauptziel dieser Arbeit die Entwicklung von elektrogesponnenen Wundauflagen mit TE als aktiver Komponente. Das Grundkonzept bestand darin, kolloidale Dispersionen von TE in eine Polyvinylalkohol (PVA)-Matrix einzuarbeiten und Wundauflagen durch Elektrospinnen herzustellen. Die TE-Partikel weisen jedoch einzigartige Strukturen auf, die mit herkömmlichen Verfahren nicht zerkleinert werden können. Selbst wenn hochenergetische Dispersionstechniken eingesetzt werden, lassen sich in öligen oder wässrigen Dispersionen keine Partikel im kolloidalen Größenbereich herstellen. Dies stellt ein Hindernis für eine einfache Verwendung des TE in die PVA-Matrix beim Elektrospinnen dar. Im ersten Teil dieser Doktorarbeit wurden kolloidale Dispersionen konzipiert, die TE, Sonnenblumenöl, Phospholipide (PL90H) und Wasser enthalten. Zunächst wurde eine Bestimmung der Grenzflächenspannung durchgeführt, um den potenziellen Einfluss von PL90H im Dispersionsprozess und seine Wechselwirkung mit TE zu untersuchen und zu verstehen. Es wurde eine synergistische Wechselwirkung zwischen PL90H und TE beobachtet. Durch ein optimiertes stufenweises Homogenisierungsverfahren war es möglich, kolloidale Dispersionen mit Partikelgrößen unter 1 µm herzustellen. Im zweiten Teil wurden bioaktive elektrogesponnene Wundauflagen entwickelt und charakterisiert, die TE kontrolliert freisetzen können. Elektrospinnparameter zur Herstellung von Wundauflagen wurden untersucht und optimiert. Insbesondere die Variation von Konzentration und Molekulargewicht des Polymers hatte einen signifikanten Einfluss auf die Spinnbarkeit, die rheologischen Eigenschaften der Polymerlösung und die resultierenden Fasereigenschaften. Wir konnten zeigen, dass bioaktive Wundauflagen mit glatten und gleichmäßigen Fasern hergestellt werden können. In-vitro-Freisetzungs- und Ex vivo-Permeationsuntersuchungen ergaben, dass elektrogesponnene Wundauflagen Betulin über einen Zeitraum von 72 Stunden freisetzen können. Durch die Veränderung der Komponenten von kolloidalen Dispersionen, nämlich PL90H und Sonnenblumenöl, kann die Freisetzung von Betulin gesteuert werden. Ex-vivo-Wundheilungsergebnisse deuten darauf hin, dass die Behandlung mit nanofaserigen Wundauflagen, insbesondere mit niedrigen TE-Mengen, eine überragende und beschleunigte Wundheilung erzielte. Als alternative Formulierung zur Wundtherapie wurden in der letzten Phase der Arbeit TE-haltige Filme mittels Solvent Casting Methode hergestellt. Aus den in-vitro-Freisetzungs- und ex vivo-Wundheilungsstudien ergaben diese Filme positive Erkenntnisse, sodass diese ebenfalls als Wundauflagen dienen können. Dennoch waren TE-basierte elektrogesponnene Wundauflagen im Vergleich zu den gegossenen Filmen bei der Wundheilung überlegen. Mit den aktuellen Entwicklungen in der Elektrospinntechnologie ist es möglich, elektrogesponnene Wundauflagen innerhalb kürzerer Zeit auf industrieller Ebene herzustellen. Andererseits könnte die Herstellung gegossener Filme auch als einfache Alternative zur Abdeckung von Wunden dienen. In-vivo-Studien könnten für die zukünftige Umsetzung der entwickelten TE-Wundauflagen unter Nutzung der Grundlage dieser Arbeit von wesentlicher Bedeutung sein. Dieses Projekt zeigt deutlich, dass wir durch einen innovativen Ansatz bioaktive Wundauflagen entwickelt haben, die ein alternatives pharmazeutisches Formulierungspotenzial für die Wundtherapie in naher Zukunft darstellen.Wound care is a challenging task in our daily lives. Therefore, it would be highly desirable to have simple, acceptable dressing materials that can be used directly to cover wounds and accelerate wound healing. Birch bark triterpene extract (TE) has the ability to accelerate the wound healing process. Thus, the main goal of this work was to develop novel electrospun wound dressings with TE as the active principal. The underlying concept was to blend colloidal dispersions of TE with polyvinyl alcohol (PVA) matrix and produce wound dressings by electrospinning. However, TE particles exhibit unique structures which cannot be crushed by common techniques to reach particles in the colloidal size range even when high energy dispersion techniques are used. This represents an obstacle for a simple incorporation of TE into the PVA matrix through electrospinning. In the first part of this PhD thesis, the colloidal dispersions were designed to contain TE, sunflower oil, phospholipids (PL90H) and water. First, an interfacial tension analysis was performed to investigate and understand the potential influence of PL90H in the dispersion process and its interaction with TE. A synergistic interaction between PL90H and TE was also discussed. An optimized stepwise homogenization process made it feasible to produce colloidal dispersions with particle sizes below 1 µm. In order to design and develop novel wound dressings as delivery devices capable of releasing TE, we focused on emulsion electrospinning technique for bioactive scaffold production. Electrospinning parameters to fabricate the dressings were investigated and optimized. In particular, the varying of concentration and molecular weight of the polymer had a significant effect on spinnability, rheological properties of polymer solution and the resulting fiber properties. We showed that bioactive wound dressings with smooth and uniform fibers can be produced. Cumulative in vitro drug release and ex vivo permeation profiles showed that TE-loaded scaffolds can release Betulin in a sustained release manner. By adjusting components of the colloidal dispersions, namely PL90H and sunflower oil, the release of Betulin can be controlled. Amazingly, ex-vivo wound healing results indicated that treatment with nanofibrous wound dressings especially with low TE amounts achieved superlative and accelerated wound healing recovery. In the last phase of this thesis, films containing colloidal dispersions were produced using the solvent casting method, for possible alternative formulations towards wound therapy. From the in vitro drug release and ex vivo wound healing studies, these films gave positive insights to serve as additional wound dressings. Nevertheless, TE-loaded electrospun wound dressings were superior to such cast films in wound healing. With the current developments in electrospinning technology, it is possible to manufacture electrospun dressings at industrial level within shorter times. On the other hand, fabrication of such cast films could also serve as efficient dressings for covering wounds. In vivo studies could be essential for future translation of the developed TE dressings while utilizing the basis of this work. This project clearly shows that through an innovative approach we have developed bioactive wound dressings that present an alternative pharmaceutical formulation potential for wound therapy in the near future

Suspension Near-Field Electrospinning: a Nanofabrication Method of Polymer Nanoarray Architectures for Tissue Engineering

Chapter 1. This chapter is divided into six sections. The first will discuss the issue of nerve tissue loss, and the strategies of therapy (1.1). The second describes the role of nanofabrication in tissue engineering (1.2). The third section details the theoretical background of electrospinning in terms of solution and process parameters (1.3). The fourth section introduces near-field electrospinning (NFES), recent advances in this field and the principles of NFES techniques (1.4). The fifth section details objectives for a tissue engineered construct for neural cell therapy, and presents possible viable solutions (1.5). The sixth summarizes the aims and structure of this thesis (1.6)..

Plasma Science and Technology

Plasma science and technology (PST) is a discipline investigating fundamental transport behaviors, interaction physics, and reaction chemistry of plasma and its applications in different technologies and fields. Plasma has uses in refrigeration, biotechnology, health care, microelectronics and semiconductors, nanotechnology, space and environmental sciences, and so on. This book provides a comprehensive overview of PST, including information on different types of plasma, basic interactions of plasma with organic materials, plasma-based energy devices, low-temperature plasma for complex systems, and much more

Bibliography of Lewis Research Center technical publications announced in 1989

This compilation of abstracts describes and indexes the technical reporting that resulted from the scientific and engineering work performed and managed by the Lewis Research Center in 1989. All the publications were announced in the 1989 issues of STAR (Scientific and Technical Aerospace Reports) and/or IAA (International Aerospace Abstracts). Included are research reports, journal articles, conference presentations, patents and patent applications, and theses

Microfluidics and Nanofluidics Handbook

The Microfluidics and Nanofluidics Handbook: Two-Volume Set comprehensively captures the cross-disciplinary breadth of the fields of micro- and nanofluidics, which encompass the biological sciences, chemistry, physics and engineering applications. To fill the knowledge gap between engineering and the basic sciences, the editors pulled together key individuals, well known in their respective areas, to author chapters that help graduate students, scientists, and practicing engineers understand the overall area of microfluidics and nanofluidics. Topics covered include Finite Volume Method for Numerical Simulation Lattice Boltzmann Method and Its Applications in Microfluidics Microparticle and Nanoparticle Manipulation Methane Solubility Enhancement in Water Confined to Nanoscale Pores Volume Two: Fabrication, Implementation, and Applications focuses on topics related to experimental and numerical methods. It also covers fabrication and applications in a variety of areas, from aerospace to biological systems. Reflecting the inherent nature of microfluidics and nanofluidics, the book includes as much interdisciplinary knowledge as possible. It provides the fundamental science background for newcomers and advanced techniques and concepts for experienced researchers and professionals