Esse trabalho é sobre a agregação da droga leishmanicida miltefosina e um análogo fluorescente e sua interação com vesículas fosfolipídicas. A leishmaniose é uma doença tropical causada por diferentes espécies do gênero Leishmania que atinge boa parte do mundo e, nas duas últimas décadas, sua manifestação visceral reapareceu de forma preocupante, uma vez que sua letalidade vem aumentando de forma gradativa. Vários medicamentos estão sendo testados, incluindo o análogo lipídico sintético hexadecilfosfocolina (miltefosina), que é um agente antitumoral e antileishmania administrado oralmente que age nas membranas celulares e pode induzir apoptose. O primeiro local de interação dos análogos de fosfolipídios é a membrana celular e eles apresentam atividade citotóxica não específica em concentrações acima da sua concentração micelar crítica, sendo importante o conhecimento de suas propriedades de agregação em meio aquoso e sua forma de interação com outros agregados presentes no meio. Além disso, derivados fluorescentes da miltefosina permitem o uso de técnicas de fluorescência para a caracterização de sua atividade leishmanicida. Neste trabalho examinamos propriedades de agregação da miltefosina (MT) e de seu análogo fluorescente MT-BODIPY em meio aquoso, utilizando técnicas baseadas em medidas de tensão superficial e de espectroscopia de fluorescência, tanto estática como com resolução temporal. Os resultados de cmc da miltefosina, a 25oC utilizando diferentes métodos, foram 60M em meio aquoso puro (água Milli-Q), 50M em tampão fosfato 10mM (pH 7,4), e 35M em tampão fosfato com NaCl 150mM. Através do estudo de vários parâmetros de fluorescência, verificamos que para a MT-BODIPY, um limite superior para sua cmc é de 10M. Utilizando a sonda fluorescente amino-hexadecil-benzamida (Ahba) estudamos a interação entre a miltefosina e vesículas fosfolipídicas de DMPC e DPPC, analisando os espectros de absorção e emissão fluorescente, a anisotropia estática e os decaimentos da intensidade fluorescente e da anisotropia. O conjunto de resultados mostrou que os efeitos do acréscimo de miltefosina às vesículas, no intervalo de razões molares entre 1:100 e 5:100, não são monitorados pela sonda Ahba, uma sonda localizada na região das cabeças polares. Por outro lado, a análise da fluorescência intrínseca da MT-BODIPY mostrou que seu acréscimo, no mesmo intervalo de razões molares, promove desorganização da bicamada lipídica. Como nesse caso o grupo fluorescente localiza-se no final da cadeia alifática, concluimos que os maiores efeitos da miltefosina sobre as bicamadas ocorrem na região interna das cadeias apolares. / This work is about the aggregation of the leishmanicidal drug miltefosine and a fluorescent analogue and their interaction with phospholipid vesicles. Leishmaniasis is a complex of tropical diseases caused by different species of the genus Leishmania which reaches almost the whole world, including Brazil, and, on the last decades, its visceral form reappeared with hundreds of million people at risk of infection, and the mortality rate increases every year. Several drugs have been used to treat the disease, and miltefosine, a synthetic phospholipid analogue, has been tested and it is already used in some countries. This drug has a confirmed antitumor and orally antileishmanial action on the cell membranes, which is the first local of interaction of a phospholipid analogue. The cytotoxic activity is not specific on concentrations above its critical micelle concentration (cmc), and the knowledge of the aggregation properties of the drug in aqueous medium becomes important, as well as its interaction with other aggregates presents in the environment. Fluorescent analogues of miltefosine allow the use of fluorescent techniques to characterize the antileishmanial activity of miltefosine. In this work we have investigated the aggregation properties of the drug miltefosine (MT), and the fluorescent analogue MT-BODIPY in aqueous medium, by using techniques of surface tension measurements and both, steady-state and time-resolved fluorescence spectroscopy. The values of miltefosine cmc at 25°C from different methods were about 60M in pure aqueous medium (Milli-Q water), 50M in phosphate buffer 10mM (pH 7,4), and 35M in phosphate buffer with the addition of NaCl 150mM. The fluorescent probe amino-hexadecyl-benzamide (Ahba) was used to study the interaction of miltefosine with phospholipid vesicles of DMPC and DPPC, from absorption and fluorescent emission spectra, steady-state anisotropy and fluorescence and anisotropy decays. The results have shown that the effects of miltefosine addition in the vesicles, with molar ratios between 1:100 and 5:100, are not monittored by the probe Ahba, which is located on the polar head groups region on the bilayer. On the other hand, analysing the intrinsic fluorescence of the analogue MT-BODIPY, we concluded that when the molecule is added, in the same molar ratio intervals, there is a disorder in the lipidic bilayer. The fluorescent group BODIPY is located on the aliphatic chain of MT, therefore, the more accentuated effects of miltefosine in the bilayers occur in the region of the apolar tails.

A L-Asparaginase (ASNase) é um importante agente quimioterapêutico utilizado para o tratamento da leucemia linfoblástica aguda (ALL) há mais de 40 anos. No entanto, devido à origem biológica da ASNase, enzima produzida por Escherichia coli, problemas como a imunogenicidade e baixa meia vida-plasmática devem ser considerados. Com o objetivo de minimizar essas desvantagens, várias ASNases homólogas bem como formulações de ASNase de E. coli foram investigadas. Nenhuma das formulações desenvolvidas, entretanto, foi capaz de resolver definitivamente esses problemas associados à sua origem. Nesse sentido, considerando os recentes avanços na ciência de polímeros com a possibilidade do obtenção de vesículas poliméricas usando copolímeros, este trabalho concentrou-se no desenvolvimento de polimerossomos de poli(etileno glicol)-b-poli(ε-caprolactona) (PEG-PCL) para encapsular a ASNase. Diversas condições experimentais foram investigadas e, ao final, os polimerossomos foram produzidos pela técnica de hidratação do filme polimérico utilizando a centrifugação como técnica de pós-filme para remoção de copolímero precipitado, produzindo assim vesículas polímericas de 120 a 200nm com PDI de aproximadamente 0,250. A eficiência de encapsulação da ASNase, utilizando as metodologias de centrifugação ou cromatografia de exclusão molecular, revelou taxas de encapsulação de 20-25% e 1 a 7%, repectivamente. Esses resultados apontam a importância de se determinar a eficiência de encapsulação por cromatografia de exclusão molecular ou método direto no caso de nanoestruturas auto-agregadas formadas por copolímeros, devido a valores superestimados com o emprego da centrifugação. Ainda que estudos complementares se façam necessários para liberação da enzima encapsulada ou penetração da L-asparagina nas vesículas, nossos resultados demonstram o potencial de polimerossomos para veiculação de ASNase, bem como de outras proteínas terapêuticas. / L-Asparaginase (ASNase) is an important chemotherapeutic agent used for the treatment of acute lymphoblastic leukemia (ALL) for more than 40 years. However, due to the biological origin of ASNase (produced by Escherichia coli) some drawbacks such as immunogenicity and low plasma half life are present. In order to minimize the disadvantages, several ASNases proteoforms and formulations of E. coli ASNase were investigated. However, none of this formulations completely solved the main drawbacks of ASNase. In this sense, considering the recents advances in polymers science with the possibility to develop polymeric vesicles using copolymers, this work aimed at the development of poly(ethylene glycol)-b-poly(ε-caprolactone) (PEG-PCL) vesicles to encapsulate ASNase. Different experimental conditions were investigated and, the final polymersomes formulation was prepared by film hydratation using centrifugation as a post-film technique to remove the bulky coplymer. Polymeric vesicles of 120 to 200nm with PDI of approximately, 0.250 were obtained. The encapsulation efficiency of ASNase was determined indirectly by centrifugation and directly by size exclusion chromatography, resulting in encapsulation rates of 20-25% and 1 to 7%, respectively. These results indicate the importance of determining the efficiency of encapsulation by size exclusion chromatography or direct method in the case of self-aggregated nanostructures formed by copolymers, due to values overestimated with the use of centrifugation. Our results point to the potential of polymersomes for ASNase delivery, as well as other therapeutic proteins. Nonetheless, complimentary studies are still necessary for ASNase release or L-asparagine penetration into the vesicles.

O presente trabalho teve como objetivo produzir 3,6-O, O´-dimisritoilquitosana (QDM) com baixo grau médio de substituição ((GS) ̅ ≤ 10%) a partir da reação de quitosana com cloreto de miristoíla, de maneira a conferir caráter anfifílico às cadeias poliméricas. Neste estudo foram empregadas diferentes quitosanas de partida, a saber, quitosana de origem comercial (QC), que apresenta baixo grau médio de acetilação ((GA) ̅ = 5 %) e baixa massa molar média viscosimétrica ((Mv) ̅ = 87,000 g/mol), e quitosana DAIUS (QD), produzida a partir da desacetilação de beta-quitina assistida por irradiação de ultrassom de alta intensidade, que apresenta( GA) ̅ = 15 % e (Mv) ̅ = 300,000 g/mol. Para obtenção dos derivados QDM, diferentes razões molares quitosana/cloreto de miristoíla (Q/CM) foram empregadas (1:0,075; 1:0,1; 1:0,2 e 1:0,5), e as reações foram executadas por 1 h a 25 °C. As características estruturais e morfológicas das amostras geradas neste trabalho foram determinadas pelo emprego de espectroscopias de ressonância magnética nuclear e no infravermelho e difração de raios-X. A solubilidade das amostras foi investigada por espectroscopia UV/visível e a estabilidade térmica foi estudada através de análise termogravimétrica. A partir da análise de espectroscopia no infravermelho, foi possível evidenciar a ocorrência da reação de acilação seletiva dos grupos OH das quitosanas, através da presença da banda observada em 1740 cm-1, referente à deformação axial de carbonila de éster, resultante da reação de O-acilação. A banda em 1577 cm-1 referente a N-acilação não foi evidenciada. Na segunda etapa deste estudo as amostras QCM1 ((DS) ̅ = 6,6%) e QCM4 ((DS) ̅ = 11 %), que apresentaram concentrações críticas de agregação (CAC) 8,9 × 10-3 mg/ mL e 13,2 × 10-3 mg/ mL, respectivamente, foram empregadas nos estudos de encapsulação e liberação de paclitaxel e camptotecina, fármacos hidrofóbicos anti-câncer insolúveis em água. A análise de microscopia eletrônica de transmissão (MET) mostrou que as micelas de QCM apresentaram formas aproximadamente esféricas, enquanto que o espalhamento dinâmico de luz (DLS) permitiu a determinação do diâmetro médio das micelas carregadas e vazias, que variou no intervalo 280 nm - 481 nm, enquanto o potencial zeta foi ≥ +30 mV. As micelas de QCM foram capazes de encapsular o paclitaxel e a camptotecina com elevada eficiência de encapsulação (EE > 60 %), como confirmado por análises de HPLC e UV-vis. Os estudos sobre a citotoxicidade das micelas em relação às células Caco-2 e HT29-MTX mostraram que estas não apresentaram citotoxicidade e que a encapsulação diminuiu a toxicidade de paclitaxel e camptotecina. Os estudos de permeação de paclitaxel e a camptotecina encapsulados em micelas de DMQ através da monocultura de Caco-2 e do modelo de co-cultura Caco-2 / HT29-MTX confirmaram o potencial das micelas na melhoria da absorção intestinal dos fármacos. Os estudos de liberação com ambos fármacos mostraram perfis de liberação sustentada. Os resultados obtidos sugerem que as micelas de QCM podem ser carreadoras promissoras para encapsular paclitaxel e camptotecina. / The aim of this work was to produce 3,6-O,O\'-dimyristoyl chitosan (DMC) with low average degree of substitution ((DS) ̅ ≤ 10%) from the reaction of chitosan with myristoyl chloride, in order to confer amphiphilic characteristics to the polymer chains. In this study, different chitosans were used, namely commercial chitosan (QC), which possesses low average degree of acetylation ((GA) ̅ = 5%) and a low viscosity average molecular weight ((Mv) ̅ = 87,000 g/mol), and chitosan QD, produced from the ultrasound assisted deacetylation of beta-chitin, which presents (GA) ̅ = 15% and (Mv) ̅ = 300,000 g/mol. Different molar ratios chitosan / myristoyl chloride (Q/CM) were used (1: 0.075, 1: 0.1, 1: 0.2 and 1: 0.5) to obtain the DMCh derivatives, and the reactions were carried out at 25 0C for 1 h. The structural and morphological characteristics of the samples produced in this work were determined by infrared and nuclear magnetic resonance spectroscopy and X-ray diffraction. The solubility of the samples was investigated by UV/visible spectroscopy and the thermal stability was studied by thermogravimetric analysis. From the infrared spectroscopy analysis, it was possible to observe a band at 1740 cm-1, which refers to the axial deformation of the carbonyl moiety of carboxylic ester, showing the occurrence of O-acylation. The band at 1577 cm-1, which refers to N-acylation, was not evidenced. Then, the samples DMC1 ((DS) ̅ =6,6% ) and DMC4 ((DS) ̅ =11% ), which presented critical aggregation concentrations of 8.9×10-3 mg/mL and 13.2×10-3 mg/mL, respectively, were employed in the studies of encapsulation and release of the water-insoluble anti-cancer hydrophobic drugs, paclitaxel and camptothecin. Transmission electron microscopy (TEM) analyses showed that DMC micelles presented roughly spherical shapes, and dynamic light scattering (DLS) allowed the determination of the mean diameter of charged and empty micelles, which varied between 280 nm and 481 nm, while the zeta potential, was ≥ +30 mV. DMC micelles were able to encapsulate paclitaxel and camptothecin with high encapsulation efficiency (EE> 60%), as confirmed by HPLC and UV-vis analyses. Furthermore, the micelles did not exhibit cytotoxicity toward Caco-2 and HT29-MTX cells, and the encapsulation decreased the toxicity of paclitaxel and camptothecin. Permeability studies of paclitaxel and camptothecin encapsulated into DMC micelles through Caco-2 monoculture and Caco-2 / HT29-MTX co-culture models confirmed the potential of micelles on the improvement of intestinal absorption of hydrophobic drugs. The release studies with both drugs showed sustained release profiles. Hence, the results suggest that the DMC micelles may be promising carriers for encapsulating paclitaxel and camptothecin.

A enzima L-Asparaginase (ASNase) é um biofámaco utilizado no tratamento da leucemia linfoblástica aguda, no entanto, a evolução da produção da ASNase como um medicamento desde o final da década de 1970 resultou em apenas quatro alternativas disponíveis no mercado farmacêutico, com relatos de graves reações imunogênicas e toxicidade. Desse modo, a nanotecnologia é uma plataforma que pode ser explorada para administração dessa enzima diminuindo a exposição da mesma a proteases e aumentando a sua meia-vida aparente. Os polimerossomos (PL) são opções que pela nanoestrutura vesicular poderiam encapsular a ASNase em seu core aquoso e pela presença de uma membrana polimérica, são mais robustos que os lipossomos. Assim, neste trabalho objetivou-se desenvolver PL para encapsulação da ASNase como uma alternativa às formulações deste biofármaco existentes. Foram desenvolvidos PL de PEG-PLA, PMPC-PDPA, PEG-PDPA e Pluronic® L-21. Foram estudados fatores relacionados à composição dos copolímeros (fração hidrofílica, responsividade a fatores externos tais como pH e temperatura) e métodos de elaboração (hidratação do filme polimérico, troca de pH e temperatura) bem como foi feita a caracterização dos PL obtidos (tamanho, índice de polidispersão, espessura de membrana, formação de excessivo bulk polimérico, obtenção de micelas). Também foi feito um planejamento racional para encapsulação da ASNase (hidratação direta do filme polimérico e encapsulação por eletroporação, autoagregação com encapsulação por troca de pH ou de temperatura). Para os PL preparados com PEG-PLA, a extrusão resultou em distribuição de tamanhos mais estreitos correspondentes aos valores de PDI de 0,345, 0,144 e 0,081 para PEG45-PLA69, PEG114-PLA153 e PEG114-PLA180, respectivamente. Foi demonstrado que copolímeros com menor fração hidrofóbica resultam em maior eficiência de encapsulação para proteínas, já que possuem volumes aquosos maiores. Com o PMPC25-PDPA72 foi possível encapsular em média três unidades de ASNase por vesículas através da eletroporação ou troca de pH, sendo que no primeiro método houve formação de túbulos e no último método as micelas não foram completamente removidas. Para PEG100-PDPA80, grandes agregados permaneceram após a purificação levando a um PDI alto, mas não foi observada a formação de túbulos, já a troca de pH para este copolímero resultou em maior perda de copolímeros como bulk polimérico precipitado. Para o copolimero tribloco Pluronic® L-121, foi observado que as vesículas eram estáveis durante uma semana à temperatura ambiente, contrariando o que era descrito na literatura. Nesses sistemas, quando preparados por hidratação do filme, a encapsulação da ASNase foi realizada por eletroporação mas a proteína não foi detectada dentro das vesículas. Atribuímos a não-encapsulação à organização da bicamada Pluronic® L-121 sem conformação definida das cadeias poliméricas, dificultando a reorganização do bloco hidrofílico na porção interna do poro durante eletroporação. Por troca de temperatura, cerca de 5 % de ASNase foi encapsulada e o método resultou em total recuperação da atividade da enzima. Desse modo foram obtidos diferentes PL com diferentes características nanoestruturais de acordo com os copolímeros utilizados para carreamento da ASNase. / The enzyme L-Asparaginase (ASNase) is a biopharmaceutical used in the treatment of acute lymphoblastic leukemia, still the industrial production of ASNase as a marketable drug since the late 1970s has resulted in only four alternatives available in the pharmaceutical market, with reports of severe immunogenic reactions and toxicity. In this sense, nanotechnology is a platform that can be exploited to administer this enzyme by decreasing its exposure to proteases and increasing its apparent half-life. Polymerosomes (PL) are interesting routes which by its intrinsically vesicular nanostructure could encapsulate the ASNase in its aqueous core and by the presence of a polymeric membrane, being more robust than the liposomes. Thus, in this work it was intended to develop PL for ASNase encapsulation as an alternative to existing formulations of this biopharmaceutical. PL of PEG-PLA, PMPC-PDPA, PEG-PDPA and Pluronic® L-21 were developed. It was studied the copolymers composition (i.e. hydrophilic fraction, responsiveness to external factors such as pH and temperature), PL design (i.e. polymer film hydration, pH change and temperature) and PL characterization (i.e. size, polydispersity index - PDI, membrane thickness, formation of excessive polymer bulk, micelles production). A suitable experimental planning for ASNase encapsulation (i.e. direct hydration of the polymeric film and encapsulation by electroporation, self-aggregation with encapsulation by pH or temperature change) was also performed. For the PL prepared with PEG-PLA, the extrusion resulted in narrower size distribution corresponding to the PDI values of 0.345, 0.144 and 0.081 for PEG45-PLA69, PEG114-PLA153 and PEG114-PLA180, respectively. It has been shown that copolymers with lower hydrophobic fraction result in higher encapsulation efficiency for proteins, since they have larger aqueous volumes. With PMPC25-PDPA72 PL, it was possible to encapsulate three units of ASNase per vesicles through electroporation or pH change. In the first method, tubules were formed and in the latter one the micelles were not completely removed. For PEO100-PDPA80 PL, large aggregates remained after purification leading to a high PDI value, nevertheless no tubule formation was observed, since the pH change for this copolymer resulted in greater loss of copolymers as a precipitated polymer bulk. For the Pluronic® L-121 triblock copolymer PL, it was observed that the vesicles were stable for one week at room temperature, contrary to what was described in the literature. These PLs were prepared by film hydration method and ASNase encapsulation was performed by electroporation, nonetheless the protein was not detected within the vesicles. It is attributed the non-encapsulation to the organization of the Pluronic® L-121 bilayer without defined conformation of the polymer chains, making it difficult to reorganize the hydrophilic block in the internal portion of the pore during electroporation. By temperature change, about 5% of ASNase was encapsulated and the method resulted in complete recovery of enzyme activity. In conclusion, several PLs with a vast range of differential nanostructural characteristics were obtained according to the copolymers used for ASNase loading.

A L-Asparaginase (ASNase) é um importante agente quimioterapêutico utilizado para o tratamento da leucemia linfoblástica aguda (ALL) há mais de 40 anos. No entanto, devido à origem biológica da ASNase, enzima produzida por Escherichia coli, problemas como a imunogenicidade e baixa meia vida-plasmática devem ser considerados. Com o objetivo de minimizar essas desvantagens, várias ASNases homólogas bem como formulações de ASNase de E. coli foram investigadas. Nenhuma das formulações desenvolvidas, entretanto, foi capaz de resolver definitivamente esses problemas associados à sua origem. Nesse sentido, considerando os recentes avanços na ciência de polímeros com a possibilidade do obtenção de vesículas poliméricas usando copolímeros, este trabalho concentrou-se no desenvolvimento de polimerossomos de poli(etileno glicol)-b-poli(ε-caprolactona) (PEG-PCL) para encapsular a ASNase. Diversas condições experimentais foram investigadas e, ao final, os polimerossomos foram produzidos pela técnica de hidratação do filme polimérico utilizando a centrifugação como técnica de pós-filme para remoção de copolímero precipitado, produzindo assim vesículas polímericas de 120 a 200nm com PDI de aproximadamente 0,250. A eficiência de encapsulação da ASNase, utilizando as metodologias de centrifugação ou cromatografia de exclusão molecular, revelou taxas de encapsulação de 20-25% e 1 a 7%, repectivamente. Esses resultados apontam a importância de se determinar a eficiência de encapsulação por cromatografia de exclusão molecular ou método direto no caso de nanoestruturas auto-agregadas formadas por copolímeros, devido a valores superestimados com o emprego da centrifugação. Ainda que estudos complementares se façam necessários para liberação da enzima encapsulada ou penetração da L-asparagina nas vesículas, nossos resultados demonstram o potencial de polimerossomos para veiculação de ASNase, bem como de outras proteínas terapêuticas. / L-Asparaginase (ASNase) is an important chemotherapeutic agent used for the treatment of acute lymphoblastic leukemia (ALL) for more than 40 years. However, due to the biological origin of ASNase (produced by Escherichia coli) some drawbacks such as immunogenicity and low plasma half life are present. In order to minimize the disadvantages, several ASNases proteoforms and formulations of E. coli ASNase were investigated. However, none of this formulations completely solved the main drawbacks of ASNase. In this sense, considering the recents advances in polymers science with the possibility to develop polymeric vesicles using copolymers, this work aimed at the development of poly(ethylene glycol)-b-poly(ε-caprolactone) (PEG-PCL) vesicles to encapsulate ASNase. Different experimental conditions were investigated and, the final polymersomes formulation was prepared by film hydratation using centrifugation as a post-film technique to remove the bulky coplymer. Polymeric vesicles of 120 to 200nm with PDI of approximately, 0.250 were obtained. The encapsulation efficiency of ASNase was determined indirectly by centrifugation and directly by size exclusion chromatography, resulting in encapsulation rates of 20-25% and 1 to 7%, respectively. These results indicate the importance of determining the efficiency of encapsulation by size exclusion chromatography or direct method in the case of self-aggregated nanostructures formed by copolymers, due to values overestimated with the use of centrifugation. Our results point to the potential of polymersomes for ASNase delivery, as well as other therapeutic proteins. Nonetheless, complimentary studies are still necessary for ASNase release or L-asparagine penetration into the vesicles.

A enzima L-Asparaginase (ASNase) é um biofámaco utilizado no tratamento da leucemia linfoblástica aguda, no entanto, a evolução da produção da ASNase como um medicamento desde o final da década de 1970 resultou em apenas quatro alternativas disponíveis no mercado farmacêutico, com relatos de graves reações imunogênicas e toxicidade. Desse modo, a nanotecnologia é uma plataforma que pode ser explorada para administração dessa enzima diminuindo a exposição da mesma a proteases e aumentando a sua meia-vida aparente. Os polimerossomos (PL) são opções que pela nanoestrutura vesicular poderiam encapsular a ASNase em seu core aquoso e pela presença de uma membrana polimérica, são mais robustos que os lipossomos. Assim, neste trabalho objetivou-se desenvolver PL para encapsulação da ASNase como uma alternativa às formulações deste biofármaco existentes. Foram desenvolvidos PL de PEG-PLA, PMPC-PDPA, PEG-PDPA e Pluronic® L-21. Foram estudados fatores relacionados à composição dos copolímeros (fração hidrofílica, responsividade a fatores externos tais como pH e temperatura) e métodos de elaboração (hidratação do filme polimérico, troca de pH e temperatura) bem como foi feita a caracterização dos PL obtidos (tamanho, índice de polidispersão, espessura de membrana, formação de excessivo bulk polimérico, obtenção de micelas). Também foi feito um planejamento racional para encapsulação da ASNase (hidratação direta do filme polimérico e encapsulação por eletroporação, autoagregação com encapsulação por troca de pH ou de temperatura). Para os PL preparados com PEG-PLA, a extrusão resultou em distribuição de tamanhos mais estreitos correspondentes aos valores de PDI de 0,345, 0,144 e 0,081 para PEG45-PLA69, PEG114-PLA153 e PEG114-PLA180, respectivamente. Foi demonstrado que copolímeros com menor fração hidrofóbica resultam em maior eficiência de encapsulação para proteínas, já que possuem volumes aquosos maiores. Com o PMPC25-PDPA72 foi possível encapsular em média três unidades de ASNase por vesículas através da eletroporação ou troca de pH, sendo que no primeiro método houve formação de túbulos e no último método as micelas não foram completamente removidas. Para PEG100-PDPA80, grandes agregados permaneceram após a purificação levando a um PDI alto, mas não foi observada a formação de túbulos, já a troca de pH para este copolímero resultou em maior perda de copolímeros como bulk polimérico precipitado. Para o copolimero tribloco Pluronic® L-121, foi observado que as vesículas eram estáveis durante uma semana à temperatura ambiente, contrariando o que era descrito na literatura. Nesses sistemas, quando preparados por hidratação do filme, a encapsulação da ASNase foi realizada por eletroporação mas a proteína não foi detectada dentro das vesículas. Atribuímos a não-encapsulação à organização da bicamada Pluronic® L-121 sem conformação definida das cadeias poliméricas, dificultando a reorganização do bloco hidrofílico na porção interna do poro durante eletroporação. Por troca de temperatura, cerca de 5 % de ASNase foi encapsulada e o método resultou em total recuperação da atividade da enzima. Desse modo foram obtidos diferentes PL com diferentes características nanoestruturais de acordo com os copolímeros utilizados para carreamento da ASNase. / The enzyme L-Asparaginase (ASNase) is a biopharmaceutical used in the treatment of acute lymphoblastic leukemia, still the industrial production of ASNase as a marketable drug since the late 1970s has resulted in only four alternatives available in the pharmaceutical market, with reports of severe immunogenic reactions and toxicity. In this sense, nanotechnology is a platform that can be exploited to administer this enzyme by decreasing its exposure to proteases and increasing its apparent half-life. Polymerosomes (PL) are interesting routes which by its intrinsically vesicular nanostructure could encapsulate the ASNase in its aqueous core and by the presence of a polymeric membrane, being more robust than the liposomes. Thus, in this work it was intended to develop PL for ASNase encapsulation as an alternative to existing formulations of this biopharmaceutical. PL of PEG-PLA, PMPC-PDPA, PEG-PDPA and Pluronic® L-21 were developed. It was studied the copolymers composition (i.e. hydrophilic fraction, responsiveness to external factors such as pH and temperature), PL design (i.e. polymer film hydration, pH change and temperature) and PL characterization (i.e. size, polydispersity index - PDI, membrane thickness, formation of excessive polymer bulk, micelles production). A suitable experimental planning for ASNase encapsulation (i.e. direct hydration of the polymeric film and encapsulation by electroporation, self-aggregation with encapsulation by pH or temperature change) was also performed. For the PL prepared with PEG-PLA, the extrusion resulted in narrower size distribution corresponding to the PDI values of 0.345, 0.144 and 0.081 for PEG45-PLA69, PEG114-PLA153 and PEG114-PLA180, respectively. It has been shown that copolymers with lower hydrophobic fraction result in higher encapsulation efficiency for proteins, since they have larger aqueous volumes. With PMPC25-PDPA72 PL, it was possible to encapsulate three units of ASNase per vesicles through electroporation or pH change. In the first method, tubules were formed and in the latter one the micelles were not completely removed. For PEO100-PDPA80 PL, large aggregates remained after purification leading to a high PDI value, nevertheless no tubule formation was observed, since the pH change for this copolymer resulted in greater loss of copolymers as a precipitated polymer bulk. For the Pluronic® L-121 triblock copolymer PL, it was observed that the vesicles were stable for one week at room temperature, contrary to what was described in the literature. These PLs were prepared by film hydration method and ASNase encapsulation was performed by electroporation, nonetheless the protein was not detected within the vesicles. It is attributed the non-encapsulation to the organization of the Pluronic® L-121 bilayer without defined conformation of the polymer chains, making it difficult to reorganize the hydrophilic block in the internal portion of the pore during electroporation. By temperature change, about 5% of ASNase was encapsulated and the method resulted in complete recovery of enzyme activity. In conclusion, several PLs with a vast range of differential nanostructural characteristics were obtained according to the copolymers used for ASNase loading.

Among the great breakthroughs in nanoscience and nanotechnology is the emergence of synthetic polymers that demonstrate biological activity and thus can be exploited for biomedical applications, extending from agents in therapeutics to drug delivery and tissue engineering. A key factor in the fabrication of such polymeric materials is the ability to tune and control their properties. To this end, an insight into the mode of interactions with biological systems is imperative. Computer simulations have proved to be a valuable tool that can compliment experiments and provide -otherwise inaccessible- information. In the context of this thesis, different aspects of the polymeric biological activity were investigated by studying two polymeric materials suitable for different types of applications, aiming to clarify yet undisclosed mechanisms that govern the polymers' behaviour either in solution or in conjunction with model lipid membranes. The first part of the thesis is dedicated to a nonionic amphiphilic copolymer known as Pluronic L64 that is considered as a candidate for the design of novel hybrid polymer-lipid vesicles that will act as carriers for drugs or genes. The hybrid bilayers are subjected to mechanical stress and their properties are compared to those of pure lipid bilayers. The simulations showed that the hybrid membranes can sustain increased surface tension prior to rupture, are stiffer, thicker and the polymers can induce higher lipid tail packing and also reduce the lipid mobility, rendering the membranes more ordered and less fluid. At high values of lateral pressure, which leads to pore formation, the copolymer chains decelerate the pore growth. The examination of the defect formation mechanism reveals that the hydrophilic PEO segment plays the most vital role. The same systems were also observed in varying temperatures and the impact of the inserted polymers on the phase behaviour was investigated. The data suggested that the polymers change the nature of the phase transition from a discontinuous to a continuous one. The hybrid membranes transform between the ordered and the disordered phase in a continuous manner and not at a critical melting temperature. Interestingly, the effect of polymers is different at the low and high temperature regions, as proved by the analysis of the mechanical, structural and dynamic membrane properties. The second part is focused on the study of polyhexamethylene biguanide (PHMB), a biguanide-based polyelectrolyte, that possesses remarkable biocidal properties. Even though PHMB's activity is known, the specific mode of action against bacterial membranes is still puzzling. Our work revealed that the polyelectrolyte assumes a counterintuitive behaviour in aqueous solution tending to self-organise into ordered compact structures, despite the repulsive electrostatic interactions of its positively charged segments. The formed nano-objects are thermodynamically stable, as was confirmed by free energy calculations and could be linked to PHMB's antibacterial mechanism. These findings pave the way for further computational and experimental exploration of these fascinating and promising materials that could lead to the design of novel smart biologically active nanoparticles.

Le but de ce projet est de synthétiser des peptides amphiphiles ayant une partie structurante en feuillet beta afin d'obtenir des micelles cylindriques. La partie hydrophile du peptide est associée à un polymère qui va être le support de la membrane car le peptide seul ne se structure qu'en micelle cylindrique. Une fois la membrane créée, le peptide peut être enlevé ou alors laissé au sein de la membrane et cette membrane a des applications dans la filtration spécifique car elle est nanostructurée. / The goal of this project is to synthesize amphphilic peptides with a structuring part in beta sheet in order to obtain cylindrical mycelles. The hydrophylic part of the peptide is associated to a polymer which will be the support of the membrane because the peptide itself doesn't associate to crate a membrane. With the membrane, we can remove the peptide or not and this membrane has specific filtration properties since it is nanostructured.

Bacterial infections have posed a serious threat to the public health due to the significant rise of the infections caused by antibiotic-resistant bacteria. There has been considerable interest in the development of antimicrobial agents which mimic the natural HDPs, and among them biodegradable polymers are newly discovered drug candidates with ease of synthesis and low manufacture cost compared to synthetic host defense peptides. Herein, we present the synthesis of biocompatible and biodegradable polymers including polycarbonate polymers, unimolecular micelle hyperbranched polymers and dendrimers that mimic the antibacterial mechanism of HDPs by compromising bacterial cell membranes. The developed amphiphilic polycarbonates are highly selective to Gram-positive bacteria, including multidrug-resistant pathogens and the unimolecular micelle hyperbranched polymers showed promising broad-spectrum activity. However, lipidated amphiphilic dendrimers with low molecular weight display potent and selective antimicrobial activity against both Gram-positive and Gram-negative bacteria, including multidrug-resistant strains. In addition to antibacterial activity against planktonic bacteria, these dendrimers were also shown to inhibit bacterial biofilms effectively. These class of polymers may lead to a useful generation of antibiotic agents with practical applications.

The Reversible Addition Fragmentation Chain Transfer (RAFT) process using the new RAFT agent benzyldithiophenyl acetate is shown to be a powerful polymerization tool to synthesize novel well-defined amphiphilic diblock copolymers composed of the constant hydrophobic block poly(butyl acrylate) and of 6 different hydrophilic blocks with various polarities, namely a series of non-ionic, non-ionic comb-like, anionic and cationic hydrophilic blocks. The controlled character of the polymerizations was supported by the linear increase of the molar masses with conversion, monomodal molar mass distributions with low polydispersities and high degrees of end-group functionalization. <br><br> The new macro-surfactants form micelles in water, whose size and geometry strongly depend on their composition, according to dynamic and static light scattering measurements. The micellization is shown to be thermodynamically favored, due to the high incompatibility of the blocks as indicated by thermal analysis of the block copolymers in bulk. The thermodynamic state in solution is found to be in the strong or super strong segregation limit. Nevertheless, due to the low glass transition temperature of the core-forming block, unimer exchange occurs between the micelles. Despite the dynamic character of the polymeric micellar systems, the aggregation behavior is strongly dependent on the history of the sample, i.e., on the preparation conditions. The aqueous micelles exhibit high stability upon temperature cycles, except for an irreversibly precipitating block copolymer containing a hydrophilic block exhibiting a lower critical solution temperature (LCST). Their exceptional stability upon dilution indicates very low critical micelle concentrations (CMC) (below 4∙10^-4 g∙L^-1). All non-ionic copolymers with sufficiently long solvophobic blocks aggregated into direct micelles in DMSO, too. Additionally, a new low-toxic highly hydrophilic sulfoxide block enables the formation of inverse micelles in organic solvents. <br><br> The high potential of the new polymeric surfactants for many applications is demonstrated, in comparison to reference surfactants. The diblock copolymers are weakly surface-active, as indicated by the graduate decrease of the surface tension of their aqueous solutions with increasing concentration. No CMC could be detected. Their surface properties at the air/water interface confer anti-foaming properties. The macro-surfactants synthesized are surface-active at the interface between two liquid phases, too, since they are able to stabilize emulsions. The polymeric micelles are shown to exhibit a high ability to solubilize hydrophobic substances in water. / Amphiphile sind Moleküle, die aus einem hydrophilen und einem hydrophoben Molekülteil aufgebaut sind. Beispiele für Amphiphile sind Tenside, deren makromolekulares Pendant amphiphile Block-Copolymere sind, die häufig auch als Makro-Tenside bezeichnet sind. Ihre Lösungseigenschaften in einem selektiven Lösungsmittel, i.e., ein für einen Block gutes und für den anderen schlechtes Lösungsmittel, sind analog zu denen von Tensiden. Die Unverträglichkeit der Polymersegmente führt zu einer von hydrophoben Wechselwirkungen getriebenen Mikrophasenseparation, d.h. zur Selbstorganisation der amphiphilen Makromoleküle zu Mizellen unterschiedlichster Form, während die kovalente Bindung zwischen den Blöcken eine Makrophasenseparation verhindert. Aufgrund ihres besonderen strukturellen Aufbaus adsorbieren Makro-Tenside an Grenzflächen, was zahlreiche Anwendungen, z.B. zur (elektro)sterischen Stabilisierung von Emulsionen und Dispersionen findet. <br><br> Die vorliegende Arbeit demonstriert, dass die neuen kontrollierten radikalischen Polymerisationen wie die RAFT-Methode („Reversible Addition Fragmentation Chain Transfer“) für die Synthese von neuen wohldefinierten amphiphilen Diblock-Copolymerstrukturen sehr gut geeignet sind. Eine Reihe von neuen amphiphilen Diblock-Copolymeren wurde mittels RAFT synthetisiert, mit einem konstanten hydrophoben Block und verschiedenen hydrophilen Blöcken unterschiedlichster Polaritäten. Die engen Molmassenverteilungen und der lineare Aufstieg der Molmassen mit dem Umsatz belegen den kontrollierten Charakter der Polymerisation. <br><br> Die thermodynamisch favorisierte Selbstorganisation der synthetisierten Blockcopolymere in Wasser führt zur Bildung von Mizellen, deren Eigenschaften aber von der Präparationsmethode stark abhängig sind. Korrelationen zwischen den Mizelleigenschaften und der Blockcopolymerstruktur zeigen, dass die Mizellgröße vor allem von der Länge des hydrophoben Blocks kontrolliert wird, wohindagegen die Natur des hydrophilen Blocks der entscheidende Faktor für die Mizellgeometrie ist. Die gebildeten Mizellen sind besonders stabil gegenüber Verdünnung und Temperaturzyklen, was ein großer Vorteil für eventuelle Anwendungen ist. Wegen der niedrigen Glasübergangstemperatur des hydrophoben Blocks findet ein Austausch von Makromolekülen zwischen den Mizellen statt, d.h. es handelt sich um dynamische Mizellsysteme. <br><br> Das Potential der neuen Makrotenside für Anwendungen wurde untersucht. Die Polymermizellen zeigen eine hohe Kapazität wasserunlösliche Substanzen in Wasser zu solubilisieren. Die Blockcopolymere sind grenzflächenaktiv, d.h. sie adsorbieren an Wasser / Luft oder Wasser / Öl Grenzflächen. Entsprechend sind die Blockcopolymere in der Lage, Emulsionen zu stabilisieren oder als Antischaumsubstanzen zu wirken.