Thesis (Ph. D.)--Drexel University, 2007. / Includes abstract and vita. Includes bibliographical references (leaves 121-134).

Thesis (M.S.M.S.E.)--University of Delaware, 2007. / Principal faculty advisors: D. Bruce Chase and John F. Rabolt, Dept. of Materials Science & Engineering. Includes bibliographical references.

Membrane surface modification is often utilized to combat membrane fouling, i.e., the deterioration of membrane performance with time. Among many modification methods, the effect of coating the surface of a commercial membrane with electrospun nanofibers on the membrane performance has received little attention. In this work, a commercial polyethersulfone (PES) ultrafiltration membrane was modified by electrospinning PVDF hydrophobic nanofibers for different time periods, i.e., 25min, 125min, and 250min, and its effect on the filtration performance was investigated. It was found that coating with the electrospun nanofiber layer enhanced the pure water permeation (PWP) flux. While the fouling of electrospun PES (EPES) membranes was more severe when they filtered Ottawa River (OR) Water or protein solutions, their final flux was still higher than that of the PES membrane. The membranes were further characterized by scanning electron microscopy (SEM), contact angle measurement and pore size and pore size distribution. The relationship between these characteristics and the membrane performance was discussed.

Memoria para optar al Título Profesional de Médico Veterinario / Las nanofibras son fibras poliméricas que poseen al menos una dimensión de 100 nm estas pueden ser creadas a través de la técnica de electrospinnig que consta de una bomba de flujo, fuente de poder y colector. Los usos son variados entre ellos; liberación de fármacos, recubrimientos de tejidos, transporte de medicamentos, etc. Por esto mismo el área biomédica es una de las áreas con mayor aplicación. La formación de nanofibras esta basado en un elongamiento uniaxial y coaxial de la solución polimérica a través de la aplicación de un campo eléctrico. El electrospinnig coaxial o core-shell produce una fibra nanométrica que posee un núcleo que no necesariamente debe poseer propiedades dieléctricas. Esto permite encapsular materias de diferentes naturalezas, ampliando aún más el uso de estas fibras. En este trabajo se plantea que el alginato que no posee características dieléctricas para generar fibras mediante el proceso de electrospinning si puede ser utilizado como core al hacer electrospinnig coaxial al usar el polímero poli ε-caprolactona (PCL), que es un material ampliamente utilizado en medicina. Adicionalmente, se generó un protocolo de uso general y se logró formar con éxito fibras coaxiales de PCL – Alginato además de estudiar como afectan los diferentes parámetros propios de la técnica de electrospinning en los diámetros de las fibras formadas. / Nanofibers are polymeric fibers that have a maximum diameter of 100 nm this are made through the electrospinning technique that consists in a syringe, power source and a collector. These fibers have many uses such as drug release, tissue dressing, drug carriage, etc. This is why they are more useful in the biomedical field area. The development of nanofibers is based in a uniaxial or coaxial elongation of a polymeric solution when a electric field is applied. Coaxial electrospinning of a polymer forms a fiber which has a core and a shell. The core does not necessarily have to have dielectric proprieties to be electrospun, this allows the use of more kinds of material and expand even more its uses. In the current work it was demonstrate that alginate, which has no dielectric properties to be electrospun, could be used as core when performing a core-shell electrospinning using polycaprolactone (PCL) as ha shell. PCL is a widely used polymer in medicine. In addition, a general usage protocol that successfully formed core-shell nanofibers was developed using alginate– PCL and how the modulation of different parameters used in the electrospinning technique affected the diameter of the electrospun fibers. / Financiamiento: Proyecto Fondecyt No. 1140660 y Fondap ACCDiS No. 15130011.

Lack of potable water is one of the major challenges that the world faces currently and the effects of this are mainly experienced by people in developing countries. This has therefore propelled research in advanced oxidation technologies AOTs to improve the current water treatment methods using cost effective, non toxic and efficient treatment methods. Hence, in this study the sol-gel synthesis method was used to prepare TiO2 nanoparticles that were photocatalytically active under UV and visible solar light as well as possessing antibacterial properties. Silver and nitrogen doping was carried out to extend the optical absorption of TiO2. For easy removal and reuse of the photocatalyst the nanoparticles were immobilized on chitosan and poly (vinyl-alcohol-co-ethylene) using the electrospining technique. The synthesized nanomaterials were characterized by FTIR, XRD, SEM/EDS, TEM, DRS, and TGA. FTIR and EDS analysis confirmed the formation and composition of TiO2 nanopowders for the doped and undoped nanoparticles. XRD analysis showed that the anatase phase was the dominant crystalline phase of the synthesized nanopowders. SEM and TEM respectively illustrated the distribution and size of the electrospun nanofibers and the nanoparticles of TiO2. DRS results showed that there was a significant shift in the absorption band edge and wavelength of Ag-TiO2 to 397 nm, followed by N-TiO2 at 396 nm compared to the commercial titania which was at 359 nm. The photocatalytic activities and antibacterial properties of these materials were tested on methylene blue dye and E.coli microorganism respectively. Ag-TiO2 immobilized on nanofibers of chitosan and PVAE had the highest photocatalytic activity compared to N-TiO2. Similar results were observed when the biocide properties of these materials were tested on E. coli.

Recent advances in the miniaturization of biosensors and drug delivery systems have allowed for the continuous and non-invasive monitoring of patient health. While sutures are mainly used for approximating tissues in clinical practice, there has been emerging development of new suture materials for improving wound healing outcomes. We report a novel method of continuous and high-throughput fabrication of multifunctional sutures and threads which allows for control over a wide range of important microstructural and physical properties. In the proposed fabrication method, a thread or suture is spooled across a base collecting plate. The fabrication method involves direct electrospinning (ES) onto the surface of threads and sutures. ES has also been widely used within the area of biomedical and tissue engineering, given its compatibility with a range of synthetic and natural biocompatible polymers. As the thread moves beneath a syringe pump and a spinerette needle that is positively charged, electrospun nanofibers collect on the surface of the thread. The coating layer thickness and the alignment of the nanofibers with the direction of the thread is tuned by varying the spooling speed and the distance between the spinerette needle and the thread. The resulting smart sutures have applications in both passive and on-demand drug release, durable wound biosensing, and improved cell viability and attachment. These structures may be manipulated in different materials (i.e. skin, fabrics, wound dressings) and be combined using textile methods (e.g. braiding, weaving, knitting) to form three dimensional (3D) constructs. / Graduate / 2022-09-10

No description available.

O desenvolvimento de scaffolds para a aplicação em biomateriais, seja na produção de tecidos biomiméticos ou mesmo em sistemas para liberação de drogas, tem sido fundamental tanto para o entendimento dos mecanismos de crescimento de tecidos biológicos e seu funcionamento, quanto para o desenvolvimento de biomateriais que possam ser incorporados aos tecidos naturais para seu reparo e para a efetiva aplicação de agentes terapêuticos. Dentre as várias técnicas para a produção destes scaffolds, a técnica de Electrospinning (ES) foi utilizada neste trabalho para a confecção de scaffolds poliméricos com a incorporação moléculas de interesse biotecnológico. Foram produzidos scaffolds e scaffolds compósitos pela adição de nanopartículas de óxido de cério, nanoargila haloisita e protoporfirina IX complexada à nanoargila haloisita, os quais foram estudados quanto à sua morfologia e propriedades tênseis, além de terem sidos testados quanto a sua viabilidade como sistemas biomiméticos de tecidos. Os scaffolds compósitos mostraram um ganho em ordenamento e homogeneidade, e os scaffolds compósitos contendo óxido de cério mostraram um leve aumento em sua capacidade elástica, além de terem sido viáveis para o crescimento de células HCat / The development of scaffolds for biomaterials applications, in biomimetic tissues production and drug-delivery systems, have been a fundamental tool for the understanding of biological tissues growing and repair mechanisms and for the development of biomaterials that can be incorporated to the natural tissues for both repair and effective application of therapeutic agents. Amongst the several techniques for scaffolds production, the Electrospinning (ES) methodology was applied in this work for developing polymeric scaffolds with the encapsulation of molecules of biotechnological interest. Scaffolds and blend scaffolds by cerium oxide nanoparticles and haloisite nanoclay addiction were produced and studied regarding its morphology, tensile properties and cell viability as biomimetic tissues. The blend scaffolds shoed an enhancement in order and homogeneity, and those within cerium oxide showed also an increase in elastic capacity and viable physical base for HCat cells

Les benzoxaboroles sont des dérivés cycliques d'acides boroniques, récemment développés en médecine comme agents thérapeutiques. Dans cette thèse, une étude fondamentale de la formulation des benzoxaboroles dans des matériaux a été effectuée, utilisant le benzoxaborole le plus simple ainsi qu'un dérivé fluoré, l'AN2690 (antifongique approuvé par la FDA). L'étude a commencé par la détermination des données spectroscopiques de ces molécules à l'état solide, sous leur forme acide (à partir des molécules cristallisées), et basique (utilisant des matériaux modèles à base de benzoxaborolates) ; une variété de paramètres RMN a ainsi été établie pour chaque forme de la molécule. Par la suite, une première formulation a été développée par association de benzoxaborolates à un matériau inorganique de type « hydroxyde double lamellaire » (HDL Mg/Al-NO3). Un taux de charge à ~30 % massique en benzoxaboroles a pu être atteint, et des cinétiques de libérations rapides ont été observées. Cependant, une sensibilité des molécules au caractère basique de la matrice a été mise en évidence, et la structure de ces matériaux s'est avérée complexe, évoluant d'un mode d'intercalation normale à une structure de type « staging », en fonction du taux d'hydratation de l'espace interlamellaire. Dans une deuxième formulation, nous avons incorporé les benzoxaboroles, à divers taux de charge (jusqu'à 25% en masse), dans un polymère biorésorbable, l'acide poly-L-lactique (PLLA), avec une mise en forme en films et fibres, ces dernières étant formées par électrospinning. Dans ce cas, plusieurs vitesses de libération ont été obtenues, en modulant la composition et les conditions de préparation des matériaux, et les tests cellulaires réalisés (migration de cellules cancéreuses et tests antifongiques) sont en bonne corrélation avec ces cinétiques. Cette étude, dans son ensemble, permet d'élargir la gamme de formulations envisageables pour les benzoxaboroles, mais souligne aussi les enjeux associés à leur formulation dans des matériaux, du fait de la réactivité intrinsèque de la fonction benzoxaborole / Benzoxaboroles are cyclic derivatives of boronic acids, which have recently been developed as therapeutic agents. In this thesis, a fundamental study was carried out on the formulation of benzoxaboroles in materials, using the simplest benzoxaborole molecule and its fluorinated derivative, AN2690 (an antifungal agent approved by the FDA). The spectroscopic signatures of these molecules were first determined in the solid state, by looking at their acid form (using the crystallized molecules) and their basic form (using model materials based on benzoxaborolates), and this led to the establishment of the NMR parameters of each form of the molecules. A first formulation was then performed by association of benzoxaborolates with an inorganic material, a “layered double hydroxide” (Mg/Al-NO3 LDH). A loading capacity of ~ 30 wt% could be reached for this system and fast release kinetics were observed. However, the molecules were found to be sensitive to the basic character of the matrix. The resulting structure of these materials was also complex, due to the evolution from a normal mode of intercalation to a “staging” structure by dehydration of the interlamellar space. In a second formulation, the benzoxaboroles were incorporated at different loadings (up to 25 wt %), in a bioresorbable polymer, poly L lactic acid (PLLA), and shaped under the form of films and also fibers (which were obtained by electrospinning). Different release rates were achieved by varying the composition or the preparation conditions of the materials. Cellular assays investigating the migration of cancer cells and the inhibition of fungi showed a good correlation between these release rates and the cellular responses. Overall, this study allowed not only to increase the span of possible formulations of the benzoxaboroles, but also to highlight the issues related to their formulation in materials, due to the inherent reactivity of the benzaxoborole function.

Il a été montré que l’addition de fluor en petite quantité sur la surface de nanotubes de carbone mono et multiparois engendre des radicaux à long temps de vie, caractérisés ici par RPE. Ce phénomène a pu être mis à profit pour initier la polymérisation du styrène, de l’acide acrylique ou encore de l’aniline. Les chaînes polymères formées apparaissent alors greffées à la surface des tubes. Il a été observé qu’un tel greffage facilite grandement la mise en suspension des nanotubes dans des solvants organiques. Ce travail s’est également attaché à exalter la complémentarité entre nouveaux matériaux fluorés et techniques avancées de mise en œuvre. Pour la première fois, l’incorporation de nanocarbones fluorés de différentes dimensionnalités (noirs de carbone, nanotubes, nanofibres, nanodisques) dans une matrice polymère électrofilée de polyvinylpyrrolidone a été réalisée. Les tissus nanocomposites microfibreux ainsi obtenus ont ensuite fait l’objet de traitements de re-fluoration en conditions douces, afin d’augmenter leur taux de fluor final et d’en modifier la texture. Les caractérisations par microscopie à balayage, RMN du solide et XPS ont permis d’établir que l’enrichissement en fluor de la matrice polymère et la structure multi échelle spectaculaire résultant du traitement de post-fluoration réalisé permettent d’induire la propriété de superhydrophobicité, mise en évidence par la mesure d’angles de contact avec l’eau supérieurs à 150°. / It has been shown that the addition of a small amount of fluorine to the surface of single and multi-walled carbon nanotubes generates long life-time radicals, here studied by EPR. The latter phenomenon can be usefully harnessed to initiate the polymerization of styrene, acrylic acid or still aniline. The polymeric chains thus formed appear to be grafted to the tubes surface. It has been observed that such a grafting process highly increases the dispersibility of tubes in some organic solvents. This work also focused on illustrating how advanced processing techniques may complement the assets of novel fluorinated materials. Hence, the inclusion of fluorinated nanocarbons with varied dimensionalities (carbon black, nanotubes, nanofibers, nanodisks) into an electrospun polyvinylpyrrolidone polymer matrix has been achieved for the first time. The nanocomposite-based microfibrous membranes thus obtained have been reacted with gaseous fluorine in mild conditions, in order to increase their final fluorine content and modify their texture. Characterizations performed using scanning electron microscopy, solid state NMR and XPS have shown that both the fluorination of the polymer matrix and quite spectacular multiscale structure resulting from etching by fluorine induce superhydrophobicity, evidenced through contact angles of the membranes with water exceeding 150°.