The use of nanocarriers is an intriguing approach in the development of efficacious treatment for brain disorders. The aim of the conducted research was to evaluate and quantify the impact of a liposomal nanocarrier formulation on the brain drug delivery. A novel approach for investigating the blood-brain barrier transport of liposomal DAMGO is presented, including in vivo microdialysis in rat, a high quality LC-MS/MS bioanalytical method and pharmacokinetic model analysis of the data. Factors limiting the brain distribution of the free peptide DAMGO were also investigated. Microdialysis, in combination with plasma sampling, made it possible to separate the released drug from the encapsulated and to quantify the active substance in both blood and brain interstitial fluid over time. The opioid peptide DAMGO entered the brain to a limited extent, with a clearance out of the brain 13 times higher than the clearance into the brain. The brain to blood ratio of unbound drug was not affected when the efflux transporter inhibitors cyclosporine A and elacridar were co-administered with DAMGO. Nor was the transport affected in the in vitro Caco-2 assay using the same inhibitors. This indicates that DAMGO is not transported by P-glycoprotein (Pgp) or breast cancer resistant protein (Bcrp). The blood-brain barrier transport was significantly increased for DAMGO when formulated in liposomes, resulting in 2-3 fold higher brain to blood ratio of unbound DAMGO. The increased brain delivery was seen both for glutathione tagged PEGylated liposomes, as well as for PEGyalted liposomes without specific brain targeting. The improvement in brain delivery was observed only when DAMGO was encapsulated into the liposomes, thus excluding any effect of the liposomes themselves on the integrity of the blood-brain barrier. Modeling of the data provided additional mechanistic understanding of the brain uptake, showing that endocytosis or transcytosis of intact liposomes across the endothelial cell membranes were unlikely. A model describing fusion of the liposomes with the luminal membrane described the experimental data the best. In conclusion, the studies presented in this thesis all contribute to an increased understanding of how to evaluate and improve brain delivery of CNS active drugs and contribute with important insights to the nanocarrier field.

Orientador: Maria Palmira Daflon Gremião / Resumo: Glioblastomas (GBM) representam 77% dos tumores malignos do sistema nervoso central (SNC) e ainda hoje, apesar de todos os avanços na terapia, continua com prognóstico limitado. A existência de barreiras fisiológicas como a barreira hematoencefálica (BHE) representa o principal obstáculo que impede que concentrações adequadas do fármaco atinjam o local de ação. Por suas vantagens anatômicas, uma estratégia proposta para a administração de fármacos destinados ao SNC consiste no uso da via nasal. Além disso, o uso de terapias combinadas utilizando fármacos capazes de agir em diferentes alvos moleculares deve ser considerada para o tratamento de doenças complexas como GBM. O candidato a fármaco ácido alfa-ciano-4-hidroxicinâmico (CHC) e o anticorpo monoclonal cetuximab (CTX) já são explorados devido à capacidade de agir em diferentes alvos moleculares nas células tumorais e aplicados em conjunto, como uma nova abordagem combinada, podem melhorar os resultados terapêuticos. De forma complementar, a utilização de sistemas de liberação baseados em nanotecnologia trará inevitavelmente ganhos terapêuticos à combinação proposta, permitindo que atributos específicos sejam agregados ao sistema e possibilite não somente a administração nasal, como também a associação de diferentes fármacos em um único carreador. Assim, o presente estudo propõe o desenvolvimento de diferentes plataformas poliméricas baseadas em poli(ácido láctico-co-glicólico) (PLGA) e quitosana trimetilada (TMC) ou quito... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Glioblastomas (GBM) account for 77% of malignant tumors in the central nervous system (SNC), and today, despite all advances in therapy, remains with a limited prognosis. The existence of physiological barriers as the blood brain barrier (BBB) represents the main obstacle that limits appropriate concentrations of drugs designed to therapy. Due to their anatomical advantages, a strategy proposed for direct delivery to SNC involves the use of the nose-to-brain route. Besides, combination therapy that uses multiple drugs against different molecular targets should be considered for complex diseases such as GBM. Drugs like alpha-cyano-4-hydroxycinnamic acid (CHC) and the monoclonal antibody cetuximab (CTX) are already explored for their capacity to act against different hallmarks of cancer and applied together, as a novel combining approach, might improve therapeutic outcomes. Therefore, advances in nanotechnology-based delivery systems will inevitably bring therapeutic gains to the proposed combination since they enable acquisition of important characteristics desired and also the association of different drugs into a single carrier. Thus, the current study proposes the development of different polymeric platforms based on poly(lactic-co-glycolic acid) (PLGA) and trimethyl chitosan (TMC) /chitosan oligosaccharide (OCS) for CHC encapsulation. Both CHC-loaded developed systems (PLGA/TMC and PLGA/OCS) exhibited nanostructure organization of about 300 to 400 nm, containing chitosan o... (Complete abstract click electronic access below) / Doutor