81% of the population in sub-Saharan Africa relies on charcoal and firewood to cover their energy needs for cooking. In Africa charcoal is usually produced by burning tree in a traditional kilns and then the food is cooked with a carbon-fired stoves indoors. All that links to three problems; deforestation, health issues and overpopulation, all of which can be reduced with a pellet cooking stove. Zambia in sub-Saharan Africa consumes charcoal equivalent to 6,089,000 tons of firewood each year. The total consumption of firewood being 13,967,000 tons per year. That leads to harvesting rate between 250,000 and 300,000 hectares each year making Zambia having one of the world’s fastest deforestation rates. Deforestation can be reduced by using the energy from the wood more efficient. In charcoal production and heating with charcoal about 72-86% of the produced energy is released to the atmosphere resulting the efficiency rate of only 14-28%. In comparison pellet production efficiency rate is 70-83%. Therefore if fuel pellets are used for cooking purposes energy instead of charcoal efficiency increases by 42-69% leading to lower need of wood material to cover equal energy demand. In this study five hardwood species and a softwood reference material from Zambia has been evaluated for fuel pellet production purposes. Evaluated hardwood species are Umsafwa, Umupundu, Umusamba, Umwenge and Umutondo. Reference material is already in use for pellet production in Zambia. Evaluation includes pellet production in a single pellet press, post production testing and X-ray examinations for tree different moisture contents; 8%, 10% and 12%. Pellet production includes friction energy, maximal friction energy and compression energy measurements. Post production testing includes density and hardness testing as well as X-ray examinations that indicate the amount of produced ash in the combustion process. High compression energy means higher energy cost in production so low compression energy is a desired property. Umupundu was the only wood species whose moisture content had no effect on the amount of compression energy. Umsamba and Umutondo gave the lowest and Umupundu and Umsafwa the highest compression energies of the tested hardwood pellets. Almost all of the friction energies of the tested materials were close to one another. The biggest exception was Umsafwa with 8% moisture content which had 38% higher friction energy than the reference material on average in this study. The values of the friction energy are low compared with other studies but within the reasonable limits compared with the reference material. A clear linear relationship was found between the friction energy and Fmax, so the friction energy directly implies the magnitude of the force of Fmax. A high hardness value is desirable because high hardness links directly to pellets high durability. All hardwood species tested were harder than the reference material. Ash significantly shortens the service life of the pellet stove, therefore it is desirable to produce as little ash as possible. Umsafwa and Unwenge has the lowest amount of metals that indicates the smallest amount of ash formed when burning pellets. Umsafwa with MC of 12% and Umwenge with MC of 10% are the best mix based on this study. / 81% av befolkningen i Afrika söder om Sahara är beroende av träkol och ved för att täcka sitt energibehov för matlagning. I Afrika produceras träkol vanligtvis genom att träden bränns i en traditionell ugn och sedan tillagas maten med en koleldad spis inomhus. Det leder till tre problem; avskogning, hälsoproblem och överbefolkning, allt detta kan minskas med en pellets spis. I Zambia förbrukar träkol motsvarande 6 089 000 ton ved varje år, och den totala förbrukningen av ved är 13 967 000 ton per år. Det leder till en avverkningstakt på mellan 250 000 och 300 000 hektar varje år vilket gör att Zambia har en av världens snabbaste avskogningshastigheter. Avskogningen kan minskas genom att energin från veden används mer effektivt. Vid produktion och användning av träkol frigörs cirka 72-86% av den producerade energin till atmosfären, vilket resulterar i en användningsgrad på endast 14-28%. Vid pelletstillverkning är motsvarande värde mycket högre, 70-83%. Om bränslepellets används istället för kol för matlagningsändamål ökar därför energieffektiviteten med 42-69%, vilket leder till lägre behov av trämaterial för att täcka lika energibehov. I denna studie har fem lövträslag och ett referensmaterial av barrträd från Zambia utvärderats för produktion av bränslepellets. De utvärderade lövträslag är Umsafwa, Umupundu, Umusamba, Umwenge och Umutondo. Referensmaterialet används redan för pelletstillverkning i Zambia. Utvärderingen inkluderar pelletsproduktion i enpetarpress, efterproduktionstestning och röntgenundersökningar för trädens olika fukthalter; 8%, 10% och 12%. Pelletsproduktion omfattar friktionsenergi, maximal friktionsenergi och mätningar av kompressionsenergi. Testning efter produktion inkluderar densitets- och hårdhetstestning samt röntgenundersökningar som indikerar mängden producerad aska i förbränningsprocessen. Hög kompressionsenergi innebär högre energikostnad i produktionen alltså låg kompressionsenergi är en önskad egenskap. Umupundu var det enda träslag vars fukthalt inte hade någon effekt på mängden kompressionsenergi. Umsamba och Umutondo gav de lägsta och Umupundu och Umsafwa de högsta kompressionsenergierna av de testade lövträpellets. Nästan alla friktionsenergier för de testade materialen låg nära varandra. Det största undantaget var Umsafwa med 8% fukthalt som hade 38% högre friktionsenergi än referensmaterialet i genomsnitt i denna studie. Värdena på friktionsenergierna är låga jämfört med andra studier men inom de tillåtna gränserna jämfört med referensmaterialet. Ett tydligt linjärt beroende hittades mellan friktionsenergin och Fmax, således friktionsenergin antyder direkt storleken på kraften hos Fmax. Ett högt hårdhetsvärde är önskvärt eftersom det kopplas direkt positivt till pellets hållbarhet. Alla lövträslag som testades var hårdare än referensmaterialet. Ask förkortar pelletskaminens livslängd avsevärt, därför är det önskvärt att producera så lite aska som möjligt. Umsafwa och Unwenge har den lägsta mängden metaller som anger den minsta mängd aska som bildas vid förbränning av pellets. Umsafwa med MC på 12% och Umwenge med MC på 10% är den bästa mixen baserat på denna studie.

The subject of this project is to study spun cellulose fibers made by Spinnova Oy inFinland. The fibers are spun using an environmentally friendly spinning process withoutuse of harsh chemicals.The spun filaments and the yarn based on these filaments were characterized and usedas reinforcement in polylactic acid biopolymer (PLA) and in biobased epoxy resin. Acomprehensive mechanical and morphological characterization of the single filamentsand their yarn was conducted. It was found that the single filaments are flat with a largewidth/thickness ratio, they are porous especially on one side and some cellulosemicrofibril orientation is observed on the filament surface. The single filaments are stiffand strong if compared to commercial regenerated cellulose filaments but are difficultto handle as they are very small and extremely light. The yarn showed to have lowermechanical properties but is easier to handle during the process of compositemanufacturing. Unidirectional fiber-reinforced composites were made using theSpinnova-yarn and PLA polymer applying film-stacking processing method. Thecomposite mechanical properties were studied and the results showed that themechanical performance of the PLA was significantly improved. The strength improvedfrom 54 MPa of the neat PLA to 95 MPa and the stiffness from 3.4 to 8.6 GPa withaddition of 22 wt% Spinnova-yarn.The main challenge of the project was handling the single filaments and their yarn todevelop a suitable manufacturing process which allows to exploit the potential of themto obtain a homogeneous fiber “preform” and to achieve good impregnation with the PLA matrix.

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<p>Coated calcium-alginate beads are the basis of many encapsulation methods used in pursuit of cell-based enzyme and hormone replacement therapies. The standard alginate - poly-L-lysine - alginate (APA) capsules consist of a calcium-alginate hydrogel core containing cells designed to express a therapeutic product, coated with permeability controlling poly-L-lysine (PLL, a polycation) followed by an exterior layer of polyanionic alginate. Although this approach is promising, the required long-term survival of the implanted cells has remained largely elusive as the current APA capsules suffer from several biocompatibility and mechanical strength issues, one of which is the weakening of ionic crosslinks over time, exposing the encapsulated cells to the host.</p> <p>This thesis aims to replace the exterior layer of alginate with a Temporarily Reactive Polyelectrolyte (TPR) to reinforce AP capsules by forming covalently crosslinked shells. TRPs are polyanions that possess reactive electrophilic groups capable of forming permanent covalent crosslinks with the underlying polyamine (such as PLL), and subsequently hydrolyze, increasing the net negative charge of the polyanion. TRPs are thought to improve the biocompatibility and strength of the microcapsules by forming stable inert amide bonds, as well as increasing the net negative charge of the capsule through the liberation of carboxylates. This thesis will focus primarily on two TRPs: 50% hydrolyzed poly(methyl vinyl ether-<em>alt</em>-maleic anhydride), PMM₅₀ , and poly(methacrylic acid-co-2-vinyl-4,4-dimethylazlactone) with a 50:50 co-monomer ratio, PMV₅₀ . Their synthesis, rates of hydrolysis and capsule formation around encapsulated C2C12 cells for <em>in-vitro</em> and<em> in-vivo</em> studies will be described. Additionally the synthesis and rates of hydrolysis of other 2-vinyl-4,4-dimethylazlactone (VDMA)-copolymers are presented as potential candidates for future TRPs.</p> / Doctor of Philosophy (PhD)

Tissue engineering (TE) is an interdisciplinary field, in continuous evolution, that possesses as main goal the creation of efficient systems for tissues and organs healing and regeneration. For bone, TE strategies are typically based on the combined use of scaffolds, cells, and bioactive molecules. Different materials were successfully studied and proposed for the fabrication of scaffolds. Among them, silk fibroin (SF) was evaluated as particularly promising for different TE applications, especially for bone tissue regeneration. Silk fibroin, a natural protein forming the structural core of silk filaments, holds biocompatibility, mechanical properties and biodegradation rate suitable for applications in bone regeneration. However, in the past, SF has shown some limitations, especially in terms of bioactivity and effective differentiating ability of hMSCs in regenerating bone tissue. In this work, we wanted to demonstrate that SF, properly processed, chemically modified, and conjugated with selected bioactive species, can be used to prepare different systems: a functionalised scaffold; a bioresorbable material with mineralization ability; an implantable immunomodulatory material. The experimental activities performed and the deep investigation of the properties of the SF-based systems prepared, led to promising results, indicating that SF could be a flexible and powerful platform for the realization of different therapeutic tools. For some of the SF-based systems described in this dissertation, further studies are needed to assess the biological activity of the materials prepared.

Owing to their key role in mucosal functioning as surface barriers with biospecific interaction potentials, the mucins are interesting candidates for use as surface modifiers in biomaterials applications. In this work, “mild” fractionation procedures were used to prepare mucins of bovine (BSM), porcine (PGM), and human (MG1) origin. Biophysicochemical analysis showed the prepared mucins to differ in size, charge, conformation, and composition. In turn, these factors were shown to govern mucin adsorption on hydrophilic and hydrophobic model surfaces. To enable for detailed coating analysis, methods for the qualitative and quantitative analysis of mucin-based coatings were developed. Of particular interest, a method for the determination of the fraction of surface-exposed, presumed bioactive proteins in a complex mucin coating was described. It was shown, using microscopy and activation assays, that mucin precoating effectively suppresses the neutrophil response towards a polymeric model biomaterial. Under optimal coating conditions, all mucins performed equally well, thus indicating them to be functionally similar. Coating analysis suggested that efficient mucin surface-shielding is critical for good mucin coating performance. Following a study on the complexation of albumin with preadsorbed mucin, we investigated the effect of mucin precoating on the conformation and neutrophil-activating properties of adsorbed host proteins. We found that mucin precoating greatly reduces the strong immune-response normally caused by adsorbed proinflammatory proteins (IgG and sIgA). Detailed coating analysis revealed that the fraction of surface-exposed protein in the mucin-protein composite influences the neutrophil response. Unexpectedly low neutrophil activation for composites containing near-monolayer concentrations of exposed IgG, suggested IgG to act synergistically with mucin on the surface. Conformational analysis supported this by showing that a preadsorbed mucin layer could stabilize adsorbed IgG through complexation. Our findings link well to the complex in vivo situation and suggest that functional mucosal mimics can be created in situ for improved biomaterials performance.

Wenn erworbene oder angeborene Knochendefekte aufgrund überkritischer Größe oder krankhafter Störungen nicht durch natürliche Regenerationsprozesse geheilt werden können, ist der Einsatz von Knochenersatzmaterialien notwendig. In der vorliegenden Arbeit ist es gelungen ein neuartiges Knochenersatzmaterial zu entwickeln und eingehend zu charakterisieren. Dazu wurden die Phasen Silikat und Kollagen in einem biomimetisch inspirierten Prozess zu einem Anorganik/Organik-Komposit verbunden. Calciumphosphatphasen konnten darüber hinaus als dritte Komponente hinzugefügt werden. Dafür wurden Herstellungsstrategien entwickelt, die Silikat in Form von Kieselsäure, Kollagen als hochkonzentrierte Suspension und gegebenenfalls Calciumphosphat als Pulver zu homogenen Mischungen vereinten. Als Zwischenprodukte wurden Komposithydrogele erhalten, deren Überführung in Xerogele in der Literatur als kritischer Schritt gilt, weil die dabei auftretenden Kapillarspannungen die Gelstruktur in der Regel irreversibel zerstören, wodurch das Material als Pulver oder Fragmente erhalten wird. Im vorliegenden Fall aber konnte die Gelfestigkeit in einem definierten Zusammensetzungsbereich durch die Kompositbildung und die kontrollierte Trocknung der Hydrogele so gesteigert werden, dass monolithische Proben von bis zu mehreren Kubikzentimetern Größe erhalten wurden. Diese konnten ohne weitere Verarbeitungsschritte einer Reihe von Untersuchungen zu mechanischen Eigenschaften, Bioaktivität, Degradabilität und Biokompatibilität unterzogen werden.

Ein Schlüsselfeld der gegenwärtigen Biomaterialforschung ist die Modifizierung von Oberflächen mit Bestandteilen der extrazellulären Matrix (EZM) oder Molekülen, die bestimmte Funktionen nachahmen. Trotz einer Reihe positiver Ergebnisse in vitro und in vivo ist es mit den gegenwärtig zur Verfügung stehenden Immobilisierungsmethoden nicht möglich, unterschiedliche Komponenten in einem Prozessschritt zu immobilisieren, definierte Freisetzungscharakteristika für gleiche und/oder unterschiedliche Moleküle zu realisieren und die Beschichtung der Oberflächen nach Sterilisation der Implantate vorzunehmen, um empfindliche bioaktive Substanzen, wie Proteine, vor Schädigung zu bewahren. An diesem Punkt setzt die vorliegende Arbeit mit dem Ziel an, ein nukleinsäurebasiertes Immobilisierungssystem für Titanwerkstoffe zu entwickeln. Es wird zunächst am Beispiel eines Peptids mit der Aminosäuresequenz Arginin–Glyzin–Asparaginsäure (RGD) nachgewiesen, dass an der Grenzfläche Passivschicht/Elektrolyt von Titanwerkstoffen vorliegende Moleküle in durch anodische Polarisation verdickte Oxidschichten partiell eingebaut werden können und dabei ihre Funktionalität erhalten bleibt. Diese Immobilisierungsmethode wird zum Immobilisierungssystem erweitert, indem Nukleinsäureeinzelstränge mit der beschriebenen Methode als Ankerstränge (AS) in anodisch formierte Oxidschichten fixiert und in einem zweiten Prozessschritt mit komplementären Gegensträngen (GS) hybridisiert werden. In der Arbeit wird gezeigt, dass das Peptid in einem weiten Parameterbereich der elektrochemischen Bedingungen immobilisiert werden kann. Demgegenüber führen im Falle des nukleinsäurebasierten Immobilisierungssystems die Bildung reaktiver Sauerstoffspezies, die Photoaktivität der Oxidschicht sowie mehrfache Trocknungen und Wiederbenetzungen zu einer Schädigung gebundener AS bis hin zu einem vollständigen Verlust der Hybridisierbarkeit. Durch Zugabe von Ethanol in hoher Konzentration während des Immobilisierungsschritts, Arbeit unter Lichtausschluss sowie Vermeidung mehrerer Trocknungen und Wiederbenetzungen können die Nebenwirkungen soweit eingeschränkt werden, dass alle immobilisierten AS hybridisierbar sind. Nach dessen Etablierung im Rahmen dieser Arbeit ist es in nachfolgenden Projekten möglich, das nukleinsäurebasierte Immboilisierungssystem zu einem modularen, nukleinsäurebasierten Immobilisierungssystem zu erweitern, um die eingangs beschriebenen Grenzen etablierter Methoden zu umgehen. Dazu müssen im zweiten Prozessschritt Konjugate aus GS und bioaktiven Molekülen, wie z. B. Peptide oder Wachstumsfaktoren, eingesetzt werden. Weiterhin können durch die Nutzung verschiedener Längen und Basensequenzen die Hybridstabilität und damit die Freisetzungskinetik beeinflusst werden. / Surface functionalization with bioactive molecules is a main field in current biomaterial research. However, in vitro and in vivo results are heterogeneous. This may be at least partially attributed to the limits of the applied immobilization methods. With established immobilization methods possibilities are limited to immobilize different molecules in one step, to implement defined release kinetics for similar and/or different substances, or to carry out the immobilization after sterilization of the implant to save sensitive molecules from damage. Therefore in this thesis a nucleic acid based immobilization system for bioactive molecules is developed for titanium based materials. Using a peptide with the amino acid sequence arginine–glycine–aspartic acid (RGD) it is demonstrated at first, that small molecules, being present at the interface electrolyte/passive layer, can be immobilized by their partial incorporation in anodically formed oxide layers. The immobilization can be carried out in a wide range of electrochemical parameters and the peptide preserves its biological function under all conditions. This immobilization method is enhanced by utilizing single-stranded nucleic acids as anchor strands (AS), which can be hybridized by complementary strands (CS) in a second step. Contrary to the peptide, bound AS are damaged by the formation of reactive oxygen species during anodic polarization of the substrate, the photoyctivity of the titanium oxide layer and multiple drying and wetting cycles. These side effects must be constrained by adding ethanol in a high concentration to the electrolyte during the immobilization procedure, excluding light during preparation and avoiding multiple drying and wetting cycles. Applying these conutermeasures, a 100% hybridization of immobilized AS can be achieved. After establishing the nucleic acid based immobilization system it can be developed further to a modular, nucleic acid based immobilization system to overcome limitations of established immobilization methods. At first, conjugates of CS and bioactive molecules, such as peptides or growth factors, should be used in the hybridization step for a true functionalization of the surface. Furthermore, hybrid stability and thus release kinetics can be adjusted by using CS of different length and base sequences.