No description available.

No description available.

The self-assembly blends of cellulose propionate (CP) and fluorine (F)-containing cellulose derivatives was examined on a model system of solvent cast films. The F-containing derivatives were either high molecular weight statistical cellulose esters with a number of F-containing substituent evenly distributed along the backbone (F-esters), or F-terminated CP-segments with exactly one F-containing endgroup. The F-esters were synthesized in a homogeneous phase and identified by 19F-NMR. Thermal analysis showed improved thermal stability of the F-esters when compared to F-free derivatives. 1-monohydroxy functionalized CP-segments were synthesized by HBr depolymerization using either a commercially available CP with residual OH-groups or a perpropionylated CP (CTP). The hydrolysis using the commercial CP yielded only segments of a minimum DP of 50 and the Mark-Houwink constant declined from 1 to 0.6. The results indicate that in the presence of free hydroxyls branches are formed by transglycosidation. The hydrolysis from perpropionylated CP resulted in segments with a minimum DP of 7, which is in accordance to previous studies. F-terminated CP segments were synthesized by coupling of the appropriate F-containing alcohol to the CP segment via toluene diisocyanate. Solutions containing F-terminated CP-segments showed typical critical micelle behavior. The critical micelle concentration depended on the molecular weight of the CP segment and the type of F-containing endgroup. The micelles are thought to consist of a core of the F-endgroups and a corona made-up of CP. Films containing the oligomers cast from micellar solution revealed a linear decrease in wetting force according to the blend composition of the oligomer, i.e. behavior according to the rule of mixing. This indicated the absence of surface segregation of the F-endgroup and it is explained with the fact that the micellar structure is retained in the solid state, suppressing surface segregation. The solid state micelles were visualized as dome-like protrusions by height image atomic force microscopy. In systems blended with CP the distance between the protrusions was found to increase with increasing CP content which was explained by a dilution process. Films containing F-esters were characterized by wetting force measurements and x-ray photoelectron spectroscopy (XPS). The wetting force decreased dramatically at low blend content of the F-ester and at the same time an F surface-concentration higher then expected from the blend composition was found by XPS. This indicated self-assembly by surface segregation of the F-containing species during film formation. The extent of surface segregation was found to depend on the type of the F-ester group as well as on the blend concentration of the F-ester. Dynamic wetting force measurements revealed hysteresis in films containing either F-esters or F-terminated CP segments. The hysteresis was found to be both kinetic (water sorption and reorganization) and thermodynamic (surface roughness and surface coverage with F-moieties) in nature. Consecutive force loops revealed an increase in the wetting force (advancing and receding) with increasing loop number, indicating the increased hydrophobicity of the surface. The force increase was determined to be due to water sorption as well as due to surface reorganization. An increase in the size of the F-groups signified a decrease in reorganization rate due to a decreased mobility of the group. The process of reorganization was fully reversible, a behavior which is congruent with the definition of smart behavior. / Ph. D.

Biogas is produced during anaerobic degradation of organic material and mainly consist of methane and carbon dioxide. During the anaerobic degradation, the products are fatty acids such as propionate, butyrate and acetate. In the biogas process a syntrophic cooperation between different microorganisms are important, this involves syntrophic acetate oxidizing bacteria (SAOB) which degrade acetate, syntrophic propionate oxidizing bacteria (SPOB) which degrade propionate and methanogens which produces methane. The propionate degradation is often the slowest step in the biogas process since the microorganism involved do not get much energy from it. It has been observed that FeSO4 and FeCl2 improved the propionate degradation rate in thermophilic SPOB enrichment cultures but no impact on mesophilic enrichment cultures was observed.  The aim of this study was to determine the impact by Fe/S-addition on the key species (SAOB, SPOB and methanogens) involved in the propionate degradation in mesophilic enrichment cultures and cultures with sludge with high ammonia concentration. Furthermore, cultivation studies are performed to reveal the optimal concentrations of iron (FeCl2), which boost the propionate degradation rate in mesophilic SPOB-cultures.  The cultivation study was performed in batches (<500 mL) with 50 mM propionate, 0.3 mM ammonium and different FeCl2 concentrations between 0 to 20 mM. To determine the optimal FeCl2 concentration, the cultures were analysed by measuring the propionate, methane and acetate concentration using High Performance Liquid Chromatography (HPLC). The mesophilic enrichment cultures were treated with FeSO4, FeCl2, NaSO4, FeS, FeCl3, Fe2(SO4)3 and Na2S. The mesophilic cultures with sludge were treated with FeSO4, FeCl2, FeCl3, and a combination of all three compounds. The impact of Fe/S compounds on SAOB, SPOB and methanogens were analysed on the mesophilic enrichment cultures and cultures with sludge by measuring the copies of 16S rRNA gene using quantitative PCR (qPCR). It could be concluded that in the mesophilic enrichment culture none of the Fe/S compounds affected the SPOB or methanogens, but FeS increased the concentration of SAOB. In the mesophilic culture with sludge, FeCl2 and FeCl3 increased the SPOB level, however, FeSO4 decreased the SPOB level. Moreover, the SAOB levels decreased for FeCl3 and when all three compounds were combined. The methanogen level decreased over time by the compounds FeCl2 and FeSO4. From the cultivation study, the optimal FeCl2 concentration was 20 mM.

Metagenomic sequencing has provided scientists with the ability to investigate microbial populations, termed microbiomes, in environmental and clinical settings. Current approaches to metagenomic research involve the use of next-generation sequencing (NGS) to generate short, precise reads for characterization of microbial compositions. While highly accurate, short reads possess several limitations that restrict their application in metagenomic research. Third generation, long-read sequencing technologies may offer several advantages for metagenomic research. Here, we used simulated datasets, as well as experimental data from murine fecal samples, to compare the relative performance of short and long reads for metagenomic research, and their impact on assessing microbial composition. Long-read data demonstrated increased precision for identification of microbiome constituents and assessing abundance without sacrificing sensitivity. Hierarchical clustering of microbiome similarity from paired short- and long-read datasets obtained from murine fecal samples revealed clustering was driven by read type as opposed to sample type, underscoring the importance of sequence type. These findings led us to use long-read sequencing for elucidating the effects of propionic acid (PPA) on the murine gut microbiome. PPA has been shown to induce physiological changes like those observed in autism spectrum disorder (ASD). Individuals with ASD may suffer from gastrointestinal comorbidities, suggesting an association with the gut microbiome. Murine offspring fed a PPA-rich diet were assessed for microbiota perturbations. Our results demonstrated that a PPA-rich diet alters the gut microbiome of progeny mice, selecting for several bacterial species that have previously been found in greater abundance among people iv with ASD. In our study, changes to microbial abundance were also associated with significant variation in bacterial metabolic pathways related to steroid hormone biosynthesis, amino sugar, and nucleotide sugar metabolism. Taken together, our findings provide empirical evidence supporting the use of long-read sequencing in metagenomic research by elucidating links between PPA exposure and gut microbiome composition.

Burkholderia sacchari é uma espécie de bactéria capaz de acumular polihidroxialcanoatos em condições de limitação de um nutriente essencial e excesso de fonte de carbono. A partir do substrato sacarose, acumula o polímero poli-3-hidroxibutirato (P3HB), poliéster biodegradável de propriedades semelhantes às dos plásticos de origem petroquímica. A partir de sacarose e propionato como fontes de carbono, ela é capaz de acumular o copolímero poli-3-hidroxibutirato-co-3-hidroxivalerato (P3HB-co-3HV), que é mais maleável que o polímero P3HB. No entanto, apenas uma pequena porcentagem do propionato fornecido é convertida em 3HV. Isto se deve à presença de outras vias de catabolismo muito eficientes que transformam o propionato em biomassa, reduzindo a eficiência na produção do copolímero. Estudos em mutantes UV prp-, indicaram que duas vias de catabolismo de propionato podem atuar em B. sacchari: α-oxidação e o ciclo de 2-metilcitrato (2MCC). Esta última teve sua comprovação molecular comprovada, já a outra ainda está sendo estudada, mutantes afetados no consumo de intermediários da α-oxidação foram complementados fragmentos de DNA, obtidos de uma biblioteca genômica de B. sacchari os quais, após sequenciamento e comparação do banco de dados, verificou-se codificarem um regulador transcricional LysR. A análise dos genes adjacentes ao regulador sugeriu que poderiam compor um operon de uma via de α-oxidação. Diante disso, este trabalho busca a comprovação molecular da via da α-oxidação para o catabolismo de propionato em B. sacchari. / Burkholderia sacchari is a species of bacteria capable of accumulating polyhydroxyalkanoates under limiting conditions of an essential nutrient and excess carbon source. From the sucrose substrate, it accumulates polymer poly-3-hydroxybutyrate (P3HB), biodegradable polyester with properties similar to those of petrochemical plastics. From sucrose and propionate as carbon sources, it is able to accumulate the poly-3-hydroxybutyrate-co-3-hydroxyvalerate (P3HB-co-3HV) copolymer, which is more malleable than the polymer P3HB. However, only a small percentage of the supplied propionate is converted into 3HV. This is due to the presence of other very efficient catabolic pathways that transform the propionate into biomass, reducing the production efficiency of the copolymer. Studies on prp- UV mutants have indicated that two pathways of propionate catabolism may act on B. sacchari: the α-oxidation and the 2-methylcitrate cycle (2MCC). The latter had its molecular proof proven, while the other is still being studied, mutants affected in the consumption of α-oxidation intermediates were complemented DNA fragments obtained from a genomic library of B. sacchari which, after sequencing and comparison of the bank Coding for a LysR transcriptional regulator. Analysis of the genes adjacent to the regulator suggested that they could compose an operon of an α-oxidation pathway. In view of this, this work seeks the molecular proof of the α-oxidation pathway for the propionate catabolism in B. sacchari.

I formally joined Prof. M. R. N. Murthy’s laboratory at the Molecular Biophysics Unit, Indian institute of Science, on 1st August 2001. During that time, the interest in the laboratory was mainly focused on structural studies on a number of capsid mutants of two plant viruses, sesbania mosaic virus and physalis mottle virus, to gain an insight into the virus structure and its assembly. Besides these two projects, there were a few other collaborative projects running in the lab at that time such as NIa protease from pepper vein banding virus and diaminopropionate ammonia lyase from Escherichia coli with Prof. H. S. Savithri, triosephosphate isomerase from Plasmodium falciparum with Prof. P. Balaram and Prof. H. Balaram and a DNA binding protein (TP2) with Prof. M. R. S. Rao. During my first semester, along with my course work, I was assigned to make an attempt to purify and crystallize recombinant NIa protease and TP2 protein. I started with NIa protease which could be purified using one step Ni-NTA affinity column chromatography. Although the expression and protein yield were reasonably good, protein precipitated with in a couple of hours after purification. Attempts were made to prevent the precipitation of the purified enzyme and towards this end we were successful to some extent. However, during crystallization trials most of the crystallization drops precipitated completely even at low protein oncentration. TP2 protein was purified using three-step chromatographic techniques by one of the project assistant in Prof. M. R. S. Rao’s laboratory. Because of low expression level and three step purification protocol, protein yield was not good enough for complete crystallization screening. Hits obtained from our initial screening could not be confirmed because of low protein yield as well as batch to batch variation. My attempts to crystallize these two proteins remained unsuccessful but in due course I had learnt a great deal about the tips and tricks of expression, purification and mainly crystallization. To overcome the problems faced with these two proteins, we decided to make some changes in the gene construct and try different expression systems. By this time (beginning of 2002), I had finished my first semester and a major part of the course work, so we decided to start a new project focusing on some of the unknown enzymes from a metabolic pathway. Dr. Parthasarathy, who had finished his Ph. D. from the lab, helped me in literature work and in finding targets for structural studies. Finally, we decided to target enzymes involved in the propionate etabolism. The pathways for propionate metabolism in Escherichia coli as well as Salmonella typhimurium were just established and there were no structural information available for most of the enzymes involved in these pathways. Since, propionate metabolic pathways were well described in the case of Salmonella typhimurium, we decided to use this as the model organism. We first started with the enzymes present in the propionate catabolic pathway “2-methylcitrate pathway”, which converts propionate into pyruvate and succinate. 2-methylcitrate pathway resembles the well-studied glyoxylate and TCA cycle. Most of the enzymes involved in 2-methylcitrate pathway were not characterized biochemically as well as structurally. First, we cloned all the four enzymes PrpB, PrpC, PrpD and PrpE present in the prpBCDE operon along with PrpR, a transcription factor, with the help of Dr. P.S. Satheshkumar from Prof. H. S. Savithri’s laboratory. Since these five proteins were cloned with either N- or C-terminal hexa-histidine tag, they could be purified easily using one-step Ni-NTA affinity column chromatography. PrpB, PrpC and PrpD had good expression levels but with PrpE and PrpR, more than 50% of the expressed protein went into insoluble fraction, probably due to the presence of membrane spanning domains in these two enzymes. Around this time, crystallization report for the PrpD from Salmonella was published by Ivan Rayment’s group, so after that we focused only on the remaining four proteins leaving out PrpD. Our initial attempts to crystallize these proteins became successful in case of PrpB, 2-methylisocitrate lyase. We collected a complete diffraction data to a resolution of 2.5 Å which was later on extended to a resolution of 2.1 Å using another crystal. Repeated crystallization trials with PrpC also gave small protein crystals but they were not easy to reproduce and size and diffraction quality always remained a problem. Using one good crystal obtained for PrpC, data to a resolution of 3.5 Å could be collected. Unfortunately, during data collection due to failure of the cryo-system, a complete dataset could not be collected. Further attempts to crystallize this protein made by Nandashree, one of my colleagues in the lab at that time, was also without much success. Attempts to purify and crystallize PrpE and PrpR were made by me as well as one of my colleagues, Anupama. In this case, besides crystallization, low expression and precipitation of the protein after purification were major problems. Our attempt to phase the PrpB data using the closest search model (phosphoenolpyruvate mutase) by molecular replacement technique was unsuccessful,probably because of low sequence identity between them (24%). Further attempts were made to obtain heavy atom derivatives of PrpB crystal. We could obtain a mercury derivative using PCMBS. However, an electron density map based on this single derivative was not nterpretable. Around this time, the structure of 2-methylisocitrate lyase (PrpB) from E. coli was published by Grimm et. al. The structure of Salmonella PrpB could easily be determined using the E. coli PrpB enzyme as the starting model. We also solved the structure of PrpB in complex with pyruvate and Mg2+. Our attempts to crystallize PrpB with other ligands were not successful. Using the structures of PrpB and its complex with pyruvate and Mg2+, we carried out comparative studies with the well-studied structural and functional homologue, isocitrate lyase. These studies provided the plausible rationale for different substrate specificities of these two enzymes. Due to unavailability of PrpB substrate commercially and the extensive biochemical and mutational studies carried out by two different groups made us turn our attention to other enzymes in this metabolic pathway. Since our repeated attempts to obtain good diffraction quality crystals of PrpC, PrpE and PrpR continued to be unsuccessful, we decided to target other enzymes involved in propionate metabolism. We looked into the literature for the metabolic pathways by which propionate is synthesized in the Salmonella typhimurium and finally decided to target enzymes present in the metabolic pathway which converts L-threonine to propionate. Formation of propionate from L-threonine is the most direct route in many organisms. During February 2003, we initiated these studies with the last enzyme of this pathway, propionate kinase (TdcD), and within a couple of months we could obtain a well-diffracting crystal in complex with ADP and with a non-hydrolysable ATP analog, AMPPNP. TdcD structure was solved by molecular replacement using acetate kinase as a search model. Propionate kinase, like acetate kinase, contains a fold with the topology βββαβαβα, identical with that of glycerol kinase, hexokinase, heat shock cognate 70 (Hsc70) and actin, the superfamily of phosphotransferases. Examination of the active site pocket in propionate kinase revealed a plausible structural rationale for the greater specificity of the enzyme towards propionate than acetate. One of the datasets of TdcD obtained in the presence of ATP showed extra continuous density beyond the γ-phosphate. Careful examination of this extra electron density finally allowed us to build diadenosine tetraphosphate (Ap4A) into the active site pocket, which fitted the density very well. Since the data was collected at a synchrotron source to a resolution of 1.98 Å, we could identify the ligand in the active site pocket solely on the basis of difference Fourier map. Later on, co-crystallization trials of TdcD with commercially available Ap4A confirmed its binding to the enzyme. These studies suggested the presence of a novel Ap4A synthetic activity in TdcD, which is further being examined by biochemical experiments using mass-spectrometry as well as thin-layer chromatography experiments. By the end of 2004, we shifted our focus to the first enzyme involved in the anaerobic degradation of L-threonine to propionate, a biodegradative threonine deaminase (TdcB). Sagar Chittori, who had joined the lab as an integrated Ph. D student, helped me in cloning this enzyme. My attempt to crystallize this protein became finally successful and datasets in three different crystal forms were collected. Dataset for TdcB in complex with CMP was collected during a synchrotron trip to SPring8, Japan by my colleague P. Gayathri and Prof. Murthy. TdcB structure was solved by molecular replacement using the N-terminal domain of biosynthetic threonine deaminase as a search model. Structure of TdcB in the native form and in complex with CMP helped us to understand several unanswered questions related to ligand mediated oligomerization and enzyme activation observed in this enzyme. The structural studies carried out on these three enzymes have provided structural as well as functional insights into the catalytic process and revealed many unique features of these metabolic enzymes. All these have been possible mainly due to proper guidance and encouragement from Prof. Murthy and Prof. Savithri. Prof. Murthy’s teaching as well as discussions during the course of investigation has helped me in a great deal to learn and understand crystallography. Collaboration with Prof. Savithri kept me close to biochemistry and molecular biology, the background with which I entered the world of structural biology. The freedom to choose the project and carry forward some of my own ideas has given me enough confidence to enjoy doing research in future.

The upregulation of the inducible nitric oxide synthase (iNOS) and nitric oxide (NO) production have been implicated in inflammatory pathologies. Although research has revealed that glucocorticoids (GCs) such as dexamethasone and hydrocortisone inhibit iNOS expression and NO production, it remains unclear how these compounds attenuate iNOS expression and function. In response, this thesis has compared the effects of nonselective GCs (i.e., dexamethasone and hydrocortisone) with a selective GC namely, fluticasone propionate (fluticasone) to identify the precise GC actions that regulate the iNOS pathway. Additional investigations were performed to distinguish the GC and non-GC actions using receptor antagonists. Since the effects of GCs on upstream signalling pathways remain vague, further studies were conducted to investigate whether fluticasone regulates the p38 mitogen-activated protein kinases or protein kinase B (Akt) pathways, both of which have been reported to be critical for the induction of iNOS. All experiments were conducted using primary cultures of rat aortic smooth muscle cells (RASMCs). The cells were activated with bacterial LPS (100 μg/mL) and interferon-gamma (IFN-γ, 100 U/mL) to induce iNOS and NO. Nitrite levels in cellular supernatants were quantified by the Griess assay, and expressions of iNOS, phospho-p38 (P-p38), and phospho-Akt (P-Akt) were investigated by western blotting. Dexamethasone (0.1-10.0 μM) inhibited iNOS expression and NO production in a concentration dependent manner that was significant at higher concentrations (0.3-10.0 μM). Hydrocortisone (0.01-10.0 μM) also inhibited iNOS expression and NO production in a concentration dependent manner which was significant at the higher concentrations (0.1-10.0 μM). By contrast, fluticasone (0.1 nM-3.0 μM) inhibited NO production and iNOS expression only partially (~50%), and the effects were significant at 1 nM-3 μM. RU-486 (10 μM), a GC receptor (GCR) blocker, was able to reverse the inhibitions caused by dexamethasone, hydrocortisone, and fluticasone, though eplerenone (0.1-10.0 μM), the mineralocortocoid receptor blocker, had no effect. Fluticasone also inhibited the phosphorylation of p38 and Akt in activated RASMCs. The inhibitions were reversed upon incubation with RU-486 (10 μM) for 1 h prior to the addition of fluticasone. The partial inhibition of iNOS and NO by fluticasone suggests that the actions of dexamethasone and hydrocortisone were not restricted solely to GCR and that other receptors or pathways, if not both, might regulate iNOS and NO in RASMCs. In conclusion, the nonselective GCs (i.e., dexamethasone and hydrocortisone) showed a full inhibition of iNOS expression and function, whereas fluticasone only partially inhibited both processes. The inhibitions were reversed by RU-486, but not eplerenone, which strongly suggests a GC-mediated response to all three compounds investigated. Regarding fluticasone, mechanistic studies revealed that the GC can regulate key signalling pathways associated with the induction of iNOS. More specifically, fluticasone reduced the phosphorylation of p38 and Akt, thereby suggesting that its actions can be mediated by suppressing these kinase pathways, which are widely reported to critically regulate iNOS expression and function.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The aim of this work was the development of nanostructured formulations containing clobetasol propionate. Initially, it was validated a chromatographic method to assay clobetasol propionate in nanocapsule suspensions. Clobetasol propionate-loaded nanocapsules and nanospheres of poly(ε-caprolactone) (PCL) and nanoemulsion (0.5 mg mL-1) were prepared by the interfacial deposition of preformed polymer method, nanoprecipitation and spontaneous emulsification, respectively. Formulations were characterized by means of drug content, encapsulation efficiency, pH, mean size, polydispersity index, zeta potential, morphology analysis, and stability under storage. The PCL nanocapsules showed the highest physicochemical stability, followed by the nanoemulsions and nanospheres. In the evaluation of in vitro release of clobetasol propionate, the nanocapsules showed a better control of drug release, according to the biexponential model. The photodegradation study of clobetasol propionate against UVA light showed the importance of the polymer and the oil in the nanoparticles to protect the drug from light. From these results, the nanocapsules were chosen for the study of the influence of the polymerid material on the physicochemical stability umder storage, photostability, release profile of the drug and its release mechanism. The nanocapsules prepared with poly(lactide) (PLA) showed a higher stability in comparison to the nanocapsules prepared with poly(lactide-co-glycolide) 50:50 and 85:15, although its stability was lower than nanocapsules prepared with PCL. Photodegradation studies demonstrated the pretection of the nanoencapsulated drug, regardless of the polymeric material of the nanocapsule s wall. The in vitro release study demonstrated the controlled release of the drug according to an anomalous transport. Due to these results, the nanocapsules prepared with PCL were selected for the development and preparation of hydrogels. Similar formulations containing nanospheres and nanoemulsion were used to evaluate the influence of polymer and oil on different properties of the hydrogels. These dosage forms were evaluated for drug content, pH, spreadability, rheology and in vitro drug release. All hydrogels presented properties compatible to the topical application. The presence of the drug-loaded nanoparticles in hydrogels led a slower drug release, especially for the formulation containing nanocapsules. The drug release profile was according to the Higuchi model. / Este trabalho teve como principal objetivo o desenvolvimento de formulações nanoestruturadas contendo propionato de clobetasol. Inicialmente, foi validado um método cromatográfico para análise do propionato de clobetasol em suspensões de nanocápsulas poliméricas. As nanocápsulas e nanoesferas de poli(ε-caprolactona) (PCL) e nanoemulsões contendo propionato de clobetasol (0,5 mg/mL) foram preparadas pelo método da deposição interfacial do polímero pré-formado, nanoprecipitação e emulsificação espontânea, respectivamente. Foram avaliados teores de fármaco, eficiências de incorporação, pHs, diâmetros de partícula, índices de polidispersão, potenciais zeta, características morfológicas e estabilidade frente ao armazenamento das diferentes formulações. As nanocápsulas apresentaram maior estabilidade físico-química, seguida pelas nanoemulsões e nanoesferas. Na avaliação da liberação in vitro do propionato de clobetasol, as nanocápsulas apresentaram o maior controle na liberação do fármaco, seguindo um modelo biexponencial. O estudo da fotodegradação do propionato de clobetasol frente à luz UVA demonstrou a importância da presença do polímero e do óleo para o aumento da fotoestabilidade. Diante destes resultados, as nanocápsulas foram selecionadas para o estudo da influência do material polimérico sobre as características físico-químicas, estabilidade frente ao armazenamento, fotoestabilidade, perfil de liberação do fármaco e seu mecanismo de liberação. As nanocápsulas preparadas com poli(ácido lactídeo) (PLA) apresentaram uma maior estabilidade frente ao armazenamento em comparação com as nanocápsulas preparadas com poli(ácido lactídeo-coglicolídeo) 50:50 e 85:15, embora sua estabilidade tenha sido inferior às nanocápsulas preparadas com PCL. O estudo da fotodegradação demonstrou a proteção do fármaco quando nanoencapsulado, independente do tipo de polímero empregado na sua preparação. A liberação in vitro demonstrou a liberação controlada do fármaco com transporte anômalo. Diante de todos esses resultados, as nanocápsulas preparadas com PCL foram selecionadas para o desenvolvimento de formas farmacêuticas semissólidas (hidrogéis). Formulações similares contendo nanoesferas e a nanoemulsão foram utilizadas para se avaliar a influência do polímero e do óleo sobre diferentes propriedades dos hidrogéis. Estas formas farmacêuticas foram avaliadas quanto ao teor de fármaco, pH, espalhabilidade, reologia e liberação in vitro do fármaco. Os hidrogéis apresentaram propriedades compatíveis com a aplicação tópica. A presença do fármaco nanoencapsulado nos hidrogéis proporcionou sua liberação controlada, principalmente para as formulações contendo as nanocápsulas. O perfil de liberação do fármaco a partir dos hidrogéis seguiu o modelo de Higuchi.

Increasing demand for freshwater and energy is pushing towards the development of alternative technologies that are sustainable. One of the realistic solutions to address this is utilization of the renewable resources like wastewater. Conventional wastewater treatment processes can be highly energy demanding and can fails to recover the full potential of useful resources such as energy in the wastewater. As a consequence, there is an urgent necessity for sustainable wastewater treatment technologies that could harness such resources present in wastewaters. Advanced treatment process based on microbial electrochemical technologies (METs) such as microbial fuel cells (MFCs) and microbial electrolysis cells (MECs) have a great potential for the resources recovery through a sustainable wastewater treatment process. METs rely on the abilities of microorganisms that are capable of transferring electrons extracellularly by oxidizing the organic matter in the wastewater and producing electrical current for electricity generation (MFC) or H2 and CH4 production (MEC). Propionate is an important volatile fatty acid (VFA) (24-70%) in some wastewaters and accumulation of this VFA can cause a process failure in a conventional anaerobic digestion (AD) system. To address this issue, MECs were explored as a novel, alternative wastewater treatment technology, with a focus on a better understanding of propionate oxidation in the anode of MECs. Having such knowledge could help in the development of more robust and efficient wastewater treatment systems to recover energy and produce high quality effluents. Several studies were conducted to: 1) determine the paths of electron flow in the anode of propionate fed MECs low (4.5 mM) and high (36 mM) propionate concentrations; 2) examine the effect of different set anode potentials on the electrochemical performance, propionate degradation, electron fluxes, and microbial community structure in MECs fed propionate; and 3) examine the temporal dynamics of microbial communities in MECs fed with low or high concentration of acetate or propionate relating to the reactor performance. Overall, the findings from these studies provides new knowledge on propionate oxidation in MECs. The discovery of such findings may shed light on the development of an energy positive wastewater treatment process capable of producing a high quality effluent.