Urea is the most used fertilizer around the world as the main source of nitrogen to soil and plants. However, the administration of nitrogen dosage is critical, as its excess can be harmful to the environment. Therefore, the encapsulation of urea to achieve control on its release rates has been considered in several areas. In this work, encapsulation of urea by biodegradable polymer poly(3-hydroxybutyrate) (PHB) and its nanocomposites, namely PHB/MMT and PHB/OMMT, producing microcapsules by emulsion method is carried out. MMT and OMMT refer to Brazilian clays in a natural state and organophilized, respectively. In addition, the microcapsules are thus prepared to have their physicochemical characteristics investigated, then tested for biodegradation. Increment of microcapsules’ crystallinity due to the increased amount of poly(vinylacetate) (PVA), as emulsifier agent in the continuous phase, was confirmed by X-ray diffractometry (XRD) and atomic force microscopy (AFM). The presence of urea within microcapsules was verified by XRD, thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The soil biodegradation assessments showed that PHB/OMMT microcapsules present higher degradation rates in sandy soils. The overall results suggest that the composites performed better than neat PHB and are very promising; moreover, PHB/OMMT microcapsules proved to be the best candidate for the controlled-release of urea in soils.

The characterization of nanocomposites microcapsules made of biodegradable polymers is really important to science and technology, as different systems can be produced targeting unique properties. The aim of this study is to prepare and to evaluate oil loaded PHB/VMF2 microcapsules’ behavior in water. The microcapsules were analyzed by FTIR, SEM and XRD. The biodegradable nanocomposite present exfoliated clay (XRD) whose absorption at 989 cm-1(FTIR) indicates the Si-O stretching vibration, from VMF2. The microcapsules observed by SEM presented spherical shapes and some average diameters from 12 μm to 35 μm, depending on the composition of the shell and the presence or absence of the encapsulated oil. Compared to microcapsules’ shell made from PHB, those from the nanocomposite PHB/VMF2 proved to display better mechanical resistance thus very few fractured particles were observed by SEM.

pela orientação neste trabalho, pela atenção e apoio durante todo o projeto, além da disponibilidade dos materiais e laboratório. À Dra. Graça pela orientação dada há mais de 5 anos, pelo incentivo e confiança. Agradeço também pelas dicas, sugestões e ajuda nas caracterizações e finalizações deste trabalho.Aos meus colegas de laboratório Bianca, Thamyres, Raphael, Tatiana e Margarita, pela amizade, convívio e incentivo.Ao técnico Wilson, por todo auxílio prestado.Aos professores da Banca de Qualificação, Prof. Dra. Elizabeth e Prof. Dr.Leonardo, pelos sábios conselhos e direcionamentos em relação a este projeto. À Prof. Dra. Wang, pela ajuda e disponibilidade do equipamento de FTIR.Ao Prof. Dr. Jorge Tenório e aos colegas do laboratório Larex, pela disponibilidade dos equipamentos de Difração de raios X e Termogravimetria. Em especial, à Ana Carolina e Jorge Coleti pelas ajudas nas análises.Ao Dr. Daniel e ao LabMicro pelas análises de MEV.

Tuberculosis is a globally widespread infectious disease with elevated transmissibility and expressive mortality rate. It affects people throughout all age groups causing a strong economic impact on public health systems. Isoniazid, which was launched in the market in the 60’s, has been the most effective antimicrobial drug for the treatment of tuberculosis so far. However, this is a long treatment with many adverse effects resulting in poor patient compliance. Therefore, it is necessary to develop oral intake systems that minimize the adverse effects of the drug to guarantee patients adherence to the treatment. Over the last decade, extensive research has shown that the development of controlled release systems is an effective way of addressing isoniazid’s adverse effects. The intercalation of isoniazid in clay minerals such as bentonites present highly promising results and accounts for one of the uttermost contributions of material engineering science to human medicine. The present study review seeks to summarize and allow readers to understand the most recent researches on this subject