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Paclitaxel and rapamycin have been reported to act synergistically to treat breast cancer. Albeit paclitaxel is available for breast cancer treatment, the most commonly used formulation in the clinic presents side effects, limiting its use. Furthermore, both drugs present pharmacokinetics drawbacks limiting their in vivo efficacy and clinic combination. As an alternative, drug delivery systems, particularly liposomes, emerge as an option for drug combination, able to simultaneously deliver co-loaded drugs with improved therapeutic index. Therefore, the purpose of this study is to develop and characterize a co-loaded paclitaxel and rapamycin liposome and evaluate it for breast cancer efficacy both in vitro and in vivo. Results showed that a SPC/Chol/DSPE-PEG (2000) liposome was able to co-encapsulate paclitaxel and rapamycin with suitable encapsulation efficiency values, nanometric particle size, low polydispersity and neutral zeta potential. Taken together, FTIR and thermal analysis evidenced drug conversion to the more bioavailable molecular and amorphous forms, respectively, for paclitaxel and rapamycin. The pegylated liposome exhibited excellent colloidal stability and was able to retain drugs encapsulated, which were released in a slow and sustained fashion. Liposomes were more cytotoxic to 4T1 breast cancer cell line than the free drugs and drugs acted synergistically, particularly when co-loaded. Finally, in vivo therapeutic evaluation carried out in 4T1-tumor-bearing mice confirmed the in vitro results. The co-loaded paclitaxel/rapamycin pegylated liposome better controlled tumor growth compared to the solution. Therefore, we expect that the formulation developed herein might be a contribution for future studies focusing on the clinical combination of paclitaxel and rapamycin.

siRNA has recently emerged as a potential therapeutic tool for the treatment of a variety of human diseases, such as viral infection, cancer, cardiovascular and inflammatory disorders. Briefly, siRNAs are double-stranded RNAs formed by 21-23 nucleotides that are able to bind to and trigger the degradation of specific target messenger RNAs (mRNAs) through the silencing induced by the RNA-induced silencing complex. Compared with conventional therapeutics, it affords high specificity, resulting in improved efficacy and decreased side effects. However, many hurdles hamper the effective clinical application, including low intracellular delivery and poor in vivo stability. These drawbacks can be improved by the use of drug delivery systems as non-viral carriers of siRNA, which present important advantages over viral carriers, particularly the lower immunogenicity. Lipid nanoparticles are the most commonly reported type of drug delivery system for siRNA. They consist of vesicular systems, with an inner aqueous cavity, where siRNA can be loaded, surrounded by a lipid bilayer. This chapter will focus on the efforts that have been carried out to deliver siRNA loaded in lipid nanoparticles, highlighting the advantages, disadvantages, applications, clinical relevance, and future perspectives.

A doença de Chagas é causada pelo Trypanosoma cruzi e acomete milhões de pessoas, principalmente as de baixa renda em países subdesenvolvidos. É considerada uma doença negligenciada, não existindo uma terapia eficaz contra os parasitas na fase crônica da doença. Estudos preliminares demonstraram que o ácido ursólico apresenta atividade tripanocida, entretanto, este fármaco possui baixa solubilidade em água, o que prejudica a sua biodisponibilidade. Com o intuito de viabilizar a terapia com ácido ursólico, as nanopartículas poliméricas são sistemas de liberação promissores, devido a sua capacidade de liberação modificada. Além disso, os sistemas nanoencapsulados destacam-se pela alta eficiência de encapsulação do fármaco, proteção contra degradação, e menor possibilidade de causar toxicidade. O objetivo deste trabalho foi o desenvolvimento e a caracterização de nanopartículas de policaprolactona para a veiculação de ácido ursólico, visando à otimização da terapia da Doença de Chagas. O estudo teve início com o desenvolvimento das nanopartículas poliméricas contendo ácido ursólico. A formulação obtida neste estudo pela técnica da nanoprecipitação apresentou menor valor de tamanho de partícula (173,17±4,20) e índice de polidispersividade (0,09±24,77), com perfil monomodal, potencial zeta de -36 mV e eficiência de encapsulação de 94,1±1,31%. O tamanho das partículas observado na microscopia eletrônica de varredura demonstrou ser compatível com os valores observados nas análises de espalhamento dinâmico de luz, embora tenha apresentado uma característica agregada e ligeiramente esférica. Através da determinação do coeficiente de partição do ácido ursólico foi possível avaliar a alta lipofilicidade do ácido ursólico. Na determinação do coeficiente de solubilidade do ácido ursólico, o lauril sulfato de sódio foi o tensoativo de escolha para o estudo in vitro do perfil de liberação, solubilizando aproximadamente 300 ?g.mL-1 de fármaco, mas não foi possível a realização do estudo in vitro do perfil de liberação, devido a sua característica altamente lipofílica. O estudo da citotoxicidade por ensaio de resazurina mostrou que a formulação escolhida não alterou a viabilidade celular de células LLCMK2, portanto sem toxicidade para o meio biológico, bem como evidenciou a capacidade das nanopartículas poliméricas contendo ácido ursólico de reduzir a viabilidade dos parasitas em aproximadamente 50%. A avaliação da atividade biológica do ácido ursólico em camundongo C57BL/6 infectados com a cepa Y do Trypanosoma cruzi apresentou uma redução acentuada (p

Although hydrophilic small molecule drugs are widely used in the clinic, their rapid clearance, suboptimal biodistribution, low intracellular absorption and toxicity can limit their therapeutic efficacy. These drawbacks can potentially be overcome by loading the drug into delivery systems, particularly liposomes; however, low encapsulation efficiency usually results. Many strategies are available to improve both the drug encapsulation efficiency and delivery to the target site to reduce side effects. For encapsulation, passive and active strategies are available. Passive strategies encompass the proper selection of the composition of the formulation, zeta potential, particle size and preparation method. Moreover, many weak acids and bases, such as doxorubicin, can be actively loaded with high efficiency. It is highly desirable that once the drug is encapsulated, it should be released preferentially at the target site, resulting in an optimal therapeutic effect devoid of side effects. For this purpose, targeted and triggered delivery approaches are available. The rapidly increasing knowledge of the many overexpressed biochemical makers in pathological sites, reviewed herein, has enabled the development of liposomes decorated with ligands for cell-surface receptors and active delivery. Furthermore, many liposomal formulations have been designed to actively release their content in response to specific stimuli, such as a pH decrease, heat, external alternating magnetic field, ultrasound or light. More than half a century after the discovery of liposomes, some hydrophilic small molecule drugs loaded in liposomes with high encapsulation efficiency are available on the market. However, targeted liposomes or formulations able to deliver the drug after a stimulus are not yet a reality in the clinic and are still awaited.