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No description available.

Small proteins are difficult to study at high resolution with single-particle cryo-electron microscopy (cryo-EM). In general, sample properties such as large size (> 80 kDa), symmetry and rigidity are key to utilize this technology. To facilitate structural studies of small proteins as well, using cryo-EM, this project aims to incorporate a photo-inducible cross-link in a large and symmetric scaffold that is amenable for study, and covalently bind small proteins of interest to this scaffold. The scaffold in this project consists of rabbit muscle aldolase (157 kDa in tetrameric state) with an engineered affibody affinity protein (7 kDa) attached to the N-terminus of each aldolase monomer via a rigid helix fusion. The affibody-domain of the scaffold will be cross-linked to small proteins of structural interest, with a focus on a model target consisting of a second affibody with affinity for the affibody displayed on the aldolase scaffold. Photoconjugation of the affibody Zwt was performed to crosslink both the Fc of IgG and the anti-idiotypic affibody Z963, revealing that a methionine acceptor in the target is preferable but not necessary for UV crosslinking using BPA. Binding of affibodies rigidly displayed on of the scaffold to targets such as affibodies and antibody fragments was demonstrated , using surface plasmon resonance (SPR). / Att studera små protein vid hög upplösning med enpartikelsrekonstruktion i kryo-elektronmikroskopi (kryo-EM) är utmanande. Generellt så krävs stora (> 80 kDa), symmetriska och stabila protein för att använda sig av kryo-EM. Med målet att möjliggöra strukturbestämning och strukturella studier av små protein, så ska detta projekt föra in en foto-aktiverad korslänk i ett stort och symmetriskt bärarprotein. Bäraren består av aldolas från kaninmuskel (157 kDa som tetramer) med en affibody (7 kDa) kopplad till N-terminalen av varje aldolas-monomer via en rigidt fuserad helix. Affibody-domänen av bärarproteinet kan bilda korslänkar till små protein vars struktur sedan kan studeras. Fokus i projektet är ett modellprotein som består av en annan affibody som binder den affibody i bäraren. Fotokonjugering av affibodyn Zwt utfördes för att skapa korslänkar till både Fc av IgG, samt den anti-idiotypiska affibodyn Z963, vilket påvisade att en metionin-mottagare i målproteinet är fördelaktigt för UV korslänkning med BPA, men inte ett krav. Affinitet av affibodies i bärarproteinet till målprotein såsom andra affibodies och antikroppsfragment påvisades.

Interstrand cross-links (ICLs) are a type of DNA damage that prevents strand separation required for basic cellular processes. ICL-based anti-cancer therapies exploit the cytotoxic consequences of replication and transcription inhibition, however, they are limited by the ability of the cell to repair DNA crosslinks. The challenge of ICL repair involves coordinating multiple DNA repair pathways to remove damage occurring on both strands of DNA. Participation of factors that are both exclusive and essential to crosslink repair suggests a pathway requirement to process unique structures and/or intermediates arising only in ICL repair. SNM1A is a nuclease required for survival of human cells in response to ICL exposure, but the specific function and role of SNM1A remain unclear. Here we show that, in addition to known 5’-3’exonuclease activity, SNM1A possesses single-strand specific endonuclease activity. Furthermore, SNM1A exhibits translesion nuclease activity on crosslinks which deform the helical backbone, but not non-distorting stable ICLs. We report the identification and characterization of nine small molecules inhibitors of SNM1A, isolated from an in vitro high-throughput screen of nearly 4,000 bioactive compounds. Finally, we demonstrate that inhibitors of SNM1A potentiate the cytotoxicity of ICL-inducing agent cisplatin in HeLa cells. The work in this thesis expands the possible roles of SNM1A in ICL repair and lays the groundwork for SNM1A inhibition in ICL sensitization efforts. / Thesis / Doctor of Philosophy (PhD)

Natural and synthetic polymers are highly related to people's daily life in every perspective and determine everyone's life quality. This study investigated the interactions between polymer thin films and other molecules, specifically natural polymer films with other components in plant and fungal cell walls, crosslinked thermoplastic films with solvent molecules, as well as commodity thermoplastic films with air and moisture during aging by a powerful surface analysis instrument, a quartz crystal microbalance with dissipation monitoring (QCM-D). The assembly and interactions of glucan and chitin are crucial for understanding the fungal infection mechanism. Adsorption of mixed-linkage glucan (MLG) onto regenerated chitin (RChitin) and cellulose (RC) surfaces were investigated by QCM-D and atomic force microscopy (AFM). MLG was irreversibly adsorbed onto both surfaces and formed soft hydrogel-like layers with viscoelastic properties. This work established a QCM-D method to mimic the assembly of natural polymers in fungal cell walls and provided insight into the interactions of these polymers with chitin and cellulose. Poly(ether imide) (PEI) has poor solvent resistance towards solvents including chloroform, dimethylformamide (DMF), dichloromethane (DCM), and N-methyl pyrrolidone (NMP). Exposure to these solvents severely affects the thermal and mechanical performances of PEI. Therefore, crosslinked PEI (X-PEI) films was prepared from azide-terminated PEI (N₃-PEI-N₃) via a thermal crosslinking reaction. X-PEIs maintain outstanding solvent resistance towards common solvents by swelling ratio tests using QCM-D. Meanwhile, the thermal and mechanical properties of X-PEI were enhanced compared to the original PEI. Photo-oxidation is one of the dominant degradation mechanisms affecting the lifespan of polymers. The effect of photooxidative aging on the physiochemical properties of low-density polyethylene (LDPE) films were investigated using QCM-D, differential scanning calorimetry (DSC), and tensile stress-strain tests. The crystallinity, mechanical properties, and weight loss were correlated to understand the aging behavior. Materials after aging showed higher tensile stress and modulus, with reduced mass and elongation properties. Particularly, the aging-induced damage of polymer chain integrity was first determined by QCM-D through the evolution of mass loss during aging, providing supports to the changes of mechanical properties under aging. / Doctor of Philosophy / Natural polymers and thermoplastics are two major materials that are highly related to modern life. The interactions of these polymers with other molecules are important research topics for people to understand and predict the material properties. This dissertation studied the following three topics using a quartz crystal microbalance with dissipation monitoring (QCM-D): 1) interactions between plant natural polymer films and polymers in fungal cell wall; 2) solvent resistance of crosslinked thermoplastic films; and 3) physiochemical changes during photo-oxidation degradation of thermoplastic films. Pathogenic fungal cells can attack beneficial plant cell hosts by adhering themselves onto the plant cells, followed by penetration and enzymatic degradation of the multilayered plant cell walls until the host is digested. Therefore, the interaction between the components in fungal and plant cell walls is critical to understand pathogenic fungal cell invasion. Adsorption of mixed-linkage glucan (MLG) onto regenerated chitin (RChitin) and cellulose (RC) surfaces was monitored by QCM-D and atomic force microscopy (AFM). An irreversible binding interaction of MLG with chitin and cellulose films and a soft hydrogel-like layer on both surfaces were observed in our work. Poly(ether imide) (PEI) is a high-performance polymer with excellent thermal and mechanical properties. However, the good solubilities in common organic solvents that facilitate reasonable processibility limits its applications in solvent-related domains. Several methods of PEI crosslinking were developed in the literature to improve solvent resistance. This study prepared crosslinked PEI (X-PEI) films from azide-terminated PEI (N₃-PEI-N₃) via a simple thermal crosslinking reaction. X-PEI had better resistance to organic solvents from QCM-D measurements and maintained good thermal and mechanical performances. Photo-oxidation from air and sunlight slowly degrades plastics, shortens their service time, and leads to environmental pollution. This work bridged the gap between molecular integrity and its effect on the overall macroscopic mechanical changes through accurate measurement of the mass loss during degradation using a QCM-D. This work is essential in ensuring polymer design and active environmental protection.

Proteins and their intricate network of interactions are fundamental to many molecular processes that govern life. Mass spectrometry-based structural proteomics represents a powerful set of techniques for characterizing protein structures and interactions. The last decade has witnessed a large-scale adoption in the application of these techniques toward solving a variety of biological questions. Addressing these questions has often been coincident with the further development of these techniques. Insight into the structures of individual proteins and their interactions with other proteins in a proteome-wide context has been made possible by recent developments in the relatively new field of chemical crosslinking combined with mass spectrometry. In these experiments crosslinking reagents are used to capture protein-protein interactions by forming covalent linkages between proximal amino acid residues. The crosslinked proteins are then enzymatically digested into peptides, and the covalently-coupled crosslinked peptides are identified by mass spectrometry. These identified crosslinked peptides thus provide evidence of interacting regions within or between proteins. In this dissertation the development of tools and methods that facilitate this powerful technique are described. The primary arc of this work follows the development and application of mass spectrometry-based approaches for the identification of protein crosslinks ranging from those which exist endogenously to those which are introduced synthetically. Firstly, the development of a novel strategy for comprehensive determination of naturally occurring protein crosslinks in the form of disulfide bonds is described. Secondly, the application of crosslinking reagents to create synthetic crosslinks in proteins coupled with molecular dynamics simulations is explored in order to structurally characterize the intrinsically disordered tau protein. Thirdly, improvements to a crosslinking-mass spectrometry method for defining a protein-protein interactome in a complex sample is developed. Altogether, these described approaches represent a toolset to allow researchers to access information about protein structure and interactions. / Graduate

Die bisher gängigen PVC-Membranen ionenselektiver Elektroden weisen eine Reihe von Schwachstellen auf: Sie haften nur durch Adhäsion am Substrat, sodass sich bei miniaturisierten Elektroden die Membran ablösen kann; Membranbestandteile wie der Weichmacher, das Ionophor oder der Ionenaustauscher können bei der Verwendung ausgewaschen werden, sodass sich die chemischen und physikalischen Eigenschaften der Membran verschlechtern; auf der Membranoberfläche kann sich auf Grund ihrer Hydrophobie ein Biofilm ausbilden, der die Membran abschirmt. Diese Schwachstellen bewirken eine Dysfunktionalität der ionenselektiven Elektrode, weshalb im Rahmen dieser Arbeit ein Glycopolymerfilm entwickelt worden ist, der diese Schwachstellen nicht aufweist. Die in dieser Arbeit entwickelte Membran, die auf einem multifunktionalen Glycopolymer beruht, zielt auf die Egalisierung der Schwachstellen konventioneller ionenselektiver PVC-Membranen. Die entwickelte Membran kommt dabei ohne Weichmacher aus, reduziert die Ausbildung von Biofilmen, bindet kovalent an das darunterliegende organische Substrat und durch die kovalente Anbindung des Ionophors wird dessen Auswaschen verhindert. Um eine kovalente Bindung der Membran an organische Vermittlerschichten zu erreichen, wie sie bei All-solid-state-Elektroden zum Einsatz kommen, werden zunächst die photovernetzbaren Glycopolymere 12a–c entwickelt, bei denen etwa neun Photovernetzereinheiten über PEG-Spacer an den PEI25-Kern gebunden sind. Drei PEG-Spacer mit unterschiedlicher Länge werden hinsichtlich ihres Einflusses auf die Filmbildung untersucht: Sie besitzen vier (12a), acht (12b) und zwölf Ethylenglycoleinheiten (12c). Dabei zeigt sich, dass eine Spacerlänge von zwölf Ethylenglycoleinheiten für eine effektive Photovernetzung notwendig ist, weshalb für die folgenden Strukturen nur PEG12-Spacer eingesetzt werden. Um eine kovalente Anbindung des Ionophors an das Glycopolymer zu erreichen, werden verschiedene Syntheserouten genutzt und auf ihre Wirkung hin analysiert. Die frühe direkte Anbindung des Calix[4]arenderivats 3 an den PEI25-Kern der Glycopolymere 17a–c erweist sich als nachteilig, da hierdurch darauffolgende Syntheseschritte beeinträchtigt werden. Anderseits zeigen diese Glycopolymere, dass sich die Calix[4]areneinheiten nicht negativ auf die Glycopolymerfilmbildung auswirken. Zur Überwindung der erwähnten Probleme werden in den multifunktionalen Glycopolymeren 22a und 22b die Calix[4]arene wie der Photovernetzer am Ende der Syntheseroute über PEG12-Spacer angebunden. Dies erfolgt dabei über den upper rim des Calix[4]arens, da somit der lower rim, an dem sich ionenkomplexierenden Gruppen befinden, nicht beeinflusst wird. Neben der Struktur des Glycopolymers wird auch eine Methode zur Glycopolymerfilmbildung auf Modellsubstraten entwickelt. Hierfür werden Siliziumwafer mit einer hydrophilen organischen Vermittlerschicht aus (3-Glycidyloxypropyl)-trimethoxysilan (GOPS) eingesetzt. Bei der Filmbildung zeigt sich, dass die alleinige Bestrahlung mit UV-Licht nicht ausreichend ist, um eine stabile Vernetzung zu generieren. Erst nach vorausgehendem Tempern (1 h bei 120 °C) werden Filme mit einer Dicke von (42±8) nm für das Glycopolymer 12c erhalten. Die Glycopolymere 12a und 12b, die kürzere PEG-Spacer enthalten, bilden deutlich dünnere Filme aus. Für die vollständige Vernetzung ist eine Bestrahlungszeit von einer Stunde notwendig, was einer Energiedosis von etwa 290 J/cm² entspricht. Trotz möglicher freier Aminogruppen in der Struktur bilden die Glycopolymere 17a–c, bei denen unterschiedlich viele Calix[4]arene direkt an den PEI25-Kern gebunden sind, stabile Filme aus. Die sich ergebenden Schichtdicken zeigen dabei weder im Vergleich zum Glycopolymer 12c noch untereinander signifikante Unterschiede. Die Filmbildung auf dem hydrophilen GOPS wird demzufolge durch die direkt angebundenen Calix[4]arene nicht beeinträchtigt. Auf Grund des erwarteten amphiphilen Charakters der Glycopolymere 17a–c wird ihre Filmbildung nicht nur auf hydrophilen, sondern auch auf hydrophoben Modellsubstraten untersucht. Hierzu werden Siliziumwafer mit hydrophoben Vermittlerschichten aus Benzophenonsilan (BPS) und Poly-α-methylstyrol (PαMS) eingesetzt. Auf den hydrophoben Vermittlerschichten bilden die Glycopolymere 17a–c deutlich dünnere Filme aus als auf dem hydrophilen GOPS. Die Calix[4]areneinheiten sind demnach durch die Maltosehülle abgeschirmt und es treten kaum Wechselwirkungen mit den hydrophoben Substratoberflächen auf. Im Gegensatz dazu ermöglicht die Anbindung der Calix[4]arene über PEG12-Spacer den Glycopolymeren 22a und 22b auf hydrophilen wie hydrophoben Vermittlerschichten in etwa gleich dicke Filme auszubilden. Offensichtlich liegt bei diesen Glycopolymeren eine amphiphile Peripherie vor, sodass sich die Glycopolymere besonders zur Beschichtung von All-solid-state-Elektroden mit verschiedenen Mediatorschichten eignen. Die photovernetzten Glycopolymerfilme quellen auf Grund ihrer hydrophilen Eigenschaften. Der Quellungsgrad q liegt dabei niedriger, wenn hydrophobe Calix[4]arene in die Struktur eingebunden sind: q(17c) = 2,3 im Vergleich zu q(12c) = 3,6. Erfolgt die Anbindung der Calix[4]arene direkt an den PEI25-Kern, ist die Glycopolymerstruktur unflexibel, sodass der Quellungsprozess bis zu sieben Stunden benötigt. Durch die Anbindung der Calix[4]arene über PEG12-Spacer wird die Flexibilität der Glycopolymere hingegen nicht beeinträchtigt, sodass der Quellungsprozess weniger als zwei Stunden benötigt. PVC-Membranen verlieren schon nach kurzer Zeit ihre ionenselektiven Eigenschaften, weil etwa der Weichmacher aus den Membranen diffundiert und diese dadurch spröde werden. Die Glycopolymerfilme sind hingegen über einen Zeitraum von mindestens 100 Tagen gegenüber sauren (pH = 4), neutralen und basischen (pH = 10) Lösungen stabil. Die entwickelten Glycopolymere werden im Rahmen einer Kooperation mit dem Kurt-Schwabe-Institut (KSI) in Meinsberg auf All-solid-state-Elektroden als ionenselektive Membranen eingesetzt. Die Graphitelektroden werden dafür mit einer Mediatorschicht aus leitfähigem Polypyrrol (PPy) und dem Glycopolymer 17c beschichtet. Die All-solid-state-Elektroden werden hinsichtlich ihres Ansprechverhaltens gegenüber verschiedenen Ionen untersucht. Die Anbindung und Vernetzung erfolgt nach der für die Modellsubstrate optimierten Methode. Jedoch werden die Bedingungen für das Tempern angepasst, um eine Beschädigung der All-solid-state-Elektrode auszuschließen: 12 h bei 45 °C statt 1 h bei 120 °C. Dabei bildet sich ein inhomogener Belag aus, bei dem Teile der PPy-Schicht frei bleiben. Im Vergleich zur reinen und zur mit Polypyrrol (PPy) beschichteten Graphitelektrode zeigt die Elektrode, die mit einem Glycopolymerfilm versehen ist, trotz der Inhomogenität stabile und reproduzierbare Potentiale. Diese sind jedoch nicht von der Konzentration der Kationen, sondern von der der Anionen abhängig. Durch die Auftragung einer Ionentauscherschicht auf die ionenselektive Membran soll das Vordringen der Anionen in die Membran der All-solid-state-Elektrode unterbunden werden. Dadurch soll das Ansprechverhalten der All-solid-state-Elektrode auf die Kationen gelenkt werden. Entsprechende Arbeiten werden am KSI durchgeführt.

Le byssus est un amas de fibres que les moules produisent afin de s’ancrer aux surfaces immergées sous l’eau. Ces fibres sont pourvues de propriétés mécaniques impressionnantes combinant rigidité, élasticité et ténacité élevées. De plus, elles possèdent un comportement d’auto-guérison de leurs propriétés mécaniques en fonction du temps lorsque la contrainte initialement appliquée est retirée. Les propriétés mécaniques de ces fibres sont le résultat de l’agencement hiérarchique de protéines de type copolymère blocs riches en collagène et de la présence de métaux formant des liens sacrificiels réversibles avec certains acides aminés comme les DOPA et les histidines. Bien que cette fibre soit très intéressante pour la production de matériaux grâce à son contenu élevé en collagène potentiellement biocompatible, cette ressource naturelle est traitée comme un déchet par les mytiliculteurs. L’objectif de cette thèse était de valoriser cette fibre en extrayant les protéines pour générer une nouvelle classe de matériaux biomimétiques. Un hydrolysat de protéines de byssus (BPH) riche en acides aminés chargés, i.e. ~30 % mol, et permettant de former des films a pu être généré. Lorsque solubilisé à pH 10.5, le BPH forme un hydrogel contenant des structures en triple hélice de collagène et des feuillets β anti-parallèles intra- et inter-moléculaires. Suite à l’évaporation de l’eau, le film de BPH résultant est insoluble en milieu aqueux à cause des structures secondaires très stables agissant comme points de réticulation effectifs. Les propriétés mécaniques des films de BPH sont modulables en fonction du pH. Au point isoélectrique (pI = 4.5), les interactions électrostatiques entre les charges opposées agissent comme points de réticulation et augmentent la rigidité des films et leur contrainte à la rupture sans affecter la déformation à la rupture. À pH plus élevé ou plus bas que le pI, les performances mécaniques des films sont plus faibles à cause de la répulsion entre les groupements fonctionnels de même charge qui interagissent plutôt avec les molécules d’eau et causent le gonflement de la matrice protéique des films. Le BPH contenant un nombre élevé d’acides aminés chargés et réactifs, nous avons pu réticuler les films de manière covalente à l’aide d’EDC ou de glutaraldéhyde. Les propriétés mécaniques des films sont modulables en fonction de la concentration d’EDC utilisée lors de la réticulation ou en employant du glutaraldéhyde comme agent réticulant. Les films sont à la fois plus rigides et plus forts avec un degré de réticulation élevé, mais perdent leur extensibilité à mesure que les segments libres de s’étirer lors d’une traction deviennent entravés par les points de réticulation. La réticulation augmente également la résistance à la dégradation enzymatique par la collagénase, les films les plus fortement réticulés lui étant pratiquement insensibles. La spectroscopie infrarouge montre enfin que la réticulation entraîne une transition de feuillets β anti-parallèles inter-moléculaires vers des structures de type hélices de collagène/PPII hydratées. Des liens sacrificiels ont été formés dans les films de BPH par traitement au pI et/ou avec différents métaux, i.e. Na+, Ca2+, Fe3+, afin de moduler les propriétés mécaniques statiques et d’évaluer le rôle de ces traitements sur le comportement d’auto-guérison lors de tests mécaniques cycliques avec différents temps de repos. Plus la valence des ions métalliques ajoutés augmente, plus les propriétés mécaniques statiques affichent un module, une contrainte à la rupture et une ténacité élevés sans toutefois affecter la déformation à la rupture, confirmant la formation de liens sacrificiels. Les tests mécaniques cycliques montrent que les traitements au pI ou avec Ca2+ créent des liens sacrificiels ioniques réversibles qui mènent à un processus d’auto-guérison des performances mécaniques dépendant du pH. L’ajout de Fe3+ à différentes concentrations module les performances mécaniques sur un plus large intervalle et la nature plus covalente de son interaction avec les acides aminés permet d’atteindre des valeurs nettement plus élevées que les autres traitements étudiés. Le Fe3+ permet aussi la formation de liens sacrificiels réversibles menant à l’auto-guérison des propriétés mécaniques. Les spectroscopies Raman et infrarouge confirment que le fer crée des liaisons avec plusieurs acides aminés, dont les histidines et les DOPA. Les résultats dans leur ensemble démontrent que les films de BPH sont des hydrogels biomimétiques du byssus qui peuvent être traités ou réticulés de différentes façons afin de moduler leurs performances mécaniques. Ils pourraient ainsi servir de matrices pour des applications potentielles dans le domaine pharmaceutique ou en ingénierie tissulaire. / The byssus is a set of protein-based anchoring threads produced by marine mussels to tether to water immersed surfaces. These fibers have impressive mechanical properties combining stiffness, elasticity and toughness, as well as a self-healing behavior of their mechanical performance upon rest following removal of stress. These properties are the result of collagen-rich block copolymer-like proteins hierarchically assembled and of the presence of organo-metallic reversible sacrificial bonds. Even though these fibers have outstanding mechanical properties and a high content of potentially biocompatible collagen, the mussel farming industry still treats them as a waste. The main objective of this thesis was to use byssus as a sustainable biological feedstock to produce a new family of biomimetic protein-based materials. We developed a method to produce a byssus protein hydrolyzate (BPH) rich in charged amino acids (~30 % mol) and with good film-forming capabilities. A hydrogel rich in inter- and intra-molecular anti-parallel β-sheets and in collagen triple helical structures forms following the BPH solubilization at pH 10.5. After evaporation of water, the resulting film is insoluble in aqueous media as a result of the BPH self-assembly into stable secondary structures. The mechanical properties of the films are pH-responsive owing to their high electrostatic charges content that act like effective crosslinking points at the isoelectric point (pI = 4.5), but causes swelling of the protein matrix and loss of mechanical performance at pH higher or lower than the pI. The strain at fracture remains constant, which increases the toughness of the materials when moving toward the pI. The high content in charged and reactive amino acids was used to covalently crosslink the BPH films using either EDC or glutaraldehyde. Increasing the crosslinking degree gives rise to stiffer and stronger films but leads to a loss of extensibility as a consequence of protein chains being trapped by the crosslinking points. The crosslinked films become resistant to collagenase degradation even though infrared spectroscopy shows the conversion of aggregated strands to hydrated collagen/PPII related structures following the crosslinking reaction. Thus, the crosslinked collagen-related structural elements hinder the collagenase action on the BPH films. Sacrificial bonds were formed in the BPH films by treatments at their pI and/or with various metallic ions, i.e. Na+, Ca2+, Fe3+, in order to tune the mechanical properties and to evaluate the role of sacrificial bonds on the self-healing behavior during cyclic mechanical testing. Using metallic ions of higher valence to treat the films results in an increase of the modulus, strength and toughness without reducing the strain at fracture, confirming the formation of organo-metallic sacrificial bonds. Cyclic mechanical testing shows that pI and Ca2+ treatments create reversible ionic sacrificial bonds that induce a pH-dependent self-healing behavior. Fe3+ addition at various concentrations enables tuning the mechanical performances over a larger interval and to reach higher values than other treatments. This behavior is attributed to the more covalent nature of the iron-amino acids bonding and to the affinity of iron with numerous amino acids, including histidines and DOPA, as detected using Raman and infrared spectroscopy. Iron addition also leads to the formation of reversible sacrificial bonds that procure a self-healing behavior of the mechanical properties to BPH films. Altogether, our results show that the BPH films are byssus biomimetic hydrogels whose mechanical properties can be tuned by using various treatments or crosslinking reactions. The materials could thus find a niche as protein matrix in domains such as the pharmaceutical industry or soft tissue engineering.

A papaína, enzima proteolítica extraída do fruto da Carica papaya Linnaeus, apresenta grande perspectiva para carreamento de fármacos devido propriedade anti-inflamatória, antitumoral e aumento da permeação. O presente trabalho teve como objetivo estudar as variáveis de processo da síntese radio-induzida, com o propósito de avaliar a influência destes parâmetros na formação da nanopartícula além do seu potencial como nanocarreador. A síntese foi realizada na presença (20%, v/v) e ausência de etanol, tampão fosfato e radiação gama (10 kGy) para reticulação e esterilização simultânea. As amostras foram avaliadas através da técnica de espalhamento dinâmico de luz, para verificar diâmetro hidrodinâmico, UV e fluorescência para verificação do conteúdo proteico e estrutura secundária, respectivamente. A atividade enzimática foi avaliada utilizando o substrato N-alfa-benzoil-DL-arginina-4-nitroanilida (BAPA). Parâmetros como concentração proteica, molaridade do tampão, pH, tempo e temperatura de solvatação e taxa de dose foram estudados. Posteriormente, foi realizado estudo da estabilidade por 180 dias e demonstração da capacidade de radiomarcação utilizando o tecnécio-99m, além da natureza da reticulação e esterilização das amostras. Conclui-se que a síntese otimizada das nanopartículas de papaína ocorre a 10 mg.mL-1 utilizando tampão fosfato 50 mM com (pH 7) à 0°C, tempo de solvatação de 1 a 6 horas e taxa de dose de 5 kGy.h-1. Ao usar essas condições, a formação de nanopartículas ocorrerá de maneira mais efetiva e com atividade proteolítica preservada. A reticulação das nanopapaínas, nas condicões descritas acima, ocorrem majoritariamente por natureza intramolecular e apresenta esterilidade na dose estabelecida de 10 kGy. As amostras se mostraram estáveis por até 30 dias quando mantidas sob 0°C. A radiomarcação com 99mTc por via direta obteve eficiência de 90% e demonstrou o grande potencial da nanopartícula como nanocarreador. / Papain, proteolytic enzyme extracted from the fruit of Carica papaya Linnaeus, presents great prospect for drug delivery due to the anti-inflammatory and antitumor proprieties and increased permeation. The present work aims to study variable process conditions of radio-induced synthesis, with the purpose of evaluating the influence of the parameters on the nanoparticle formation and potential for radiopharmaceutical loading. The synthesis was performed in the presence (20%, v/v) and absence of ethanol, phosphate buffer and ionizing radiation at 10 kGy, using 60Co as a radioactive source to promote crosslinking and simultaneous sterilization. The samples were evaluated by dynamic light scattering to verify hydrodynamic diameter, UV and fluorescence for verification of protein content and secondary structure, respectively. The enzymatic activity was evaluated using N-alpha-benzoyl-DL-arginine-4-nitroanilide (BAPA) as specific substrate. Parameters such as protein concentration, buffer molarity, pH, time and temperature of solvation and dose rate were studied in order to evaluate the changes and the effect of each condition on the formation of the nanoparticle. Subsequently, a study of the stability of the samples for 180 days and the efficiency of the radiolabeling with technetium-99m were carried out. Additionally, the nature of protein crosslinking and the sterilization was studied. It was concluded that the optimized synthesis of papain nanoparticles occurs at 10 mg.mL-1 using 50 mM phosphate buffer (pH 6-7) at 0°C, solvation time of 1 to 6 hours and dose rate of 5 kGy.h-1. By using these conditions, the formation of nanoparticles will occur more rapidly, with preserved proteolytic activity and considerable levels of cross-linking. Papain crosslinking are intramolecular and 10 kGy demonstrate sterilized potential. Samples were stable for 20-30 days when kept at 20°C and 0-4°C, respectively. Radiolabeling with technetium by direct route obtained efficiency of 90% and demonstrated great potential as a nanocarrier.

Hidrogéis são materiais poliméricos com habilidade em intumescer em água e fluidos biológicos sem, contudo, se dissolver. Devido às suas propriedades de maciez e biocompatibilidade, estes materiais têm tido um crescimento enorme na área de engenharia de tecido, encapsulamento de células e liberação de drogas. Este trabalho visa a produção de hidrogéis de poli(N-vinil-2-pirrolidona) e seus copolímeros a partir de reticulações químicas. Como metodologia alternativa de produção de hidrogéis de poli(N-vinil-2-pirrolidona), foi estudada a reticulação do PVP por reação de Fenton, sendo que as concentrações dos reagentes foram avaliadas a fim de produzir um hidrogel com características semelhantes aos hidrogéis de PVP por radiação ionizante. O grande diferencial desta metodologia foi a rápida cinética de gelificação apresentada, creditanto um potencial de aplicação inédito. A partir de reticulações químicas mais brandas, foi estudada a produção de hidrogéis de copolímeros de N-vinil-2-pirrolidona e aldeídos com quitosana, e íons divalentes. Além de estudadas as propriedades relativas ao hidrogel tais como: conteúdo de gel, grau de intumescimento, cinética de reação, citotoxicidade, densidade de reticulação, massa molar média entre as ligações cruzadas e tamanho de poro. / Hydrogels are polymeric materials that have the ability to absorb water and biological fluids in their three-dimensional polymeric matrix without dissolution. Due to their interesting properties, such as softness and biocompatibility, there is a growing interest in their application in tissue engineering, cell encapsulation and drug delivery system. This work aims at the study of hydrogels from poly(N-vinyl-2-pyrrolidone) and copolymers produced by chemical crosslinking methods. PVP crosslinking by Fenton reaction was studied as an alternative methodology to produce poly(N-vinyl-2-pyrrolidone) hydrogels. The reagents concentrations were evaluated, in order to produce a hydrogel with the same properties of the hydrogels prepared by high energy radiation. The advantage of this methodology is its fast jellification kinetic, warranting new potential unprecedented applications. From mild chemical crosslinking methods, the production of hydrogels from copolymers of N-vinyl-2-pyrrolidone and aldehydes with chitosan, and divalent ions was studied. Hydrogels properties as: gel content, swelling ratio, reaction kinetics, cytotoxicity, crosslinking density, molecular weight and pore size were investigated.