The purpose of this work was the development of a scalable and easy-to-use electronic noses (E-noses) system architecture for volatile organic compounds sensing, towards the final goal of using several E-noses acquiring large datasets at the same time. In order to accomplish this, each E-nose system is comprised by a delivery system, a detection system and a data acquisition and control system. In order to increase the scalability, the data is stored in a database common to all E-noses. Furthermore, the system was designed so it would only require five simple steps to setup a new E-nose if needed, since the only parameter that needs to be changed is the ID of the new E-nose. The user interacts with a node using an interface, allowing for the control and visualization of the experiment. At this stage, there are three different E-nose prototypes working with this architecture in a laboratory environment.

The development of LBG-based nanoparticles intending an application in oral immunization is presented. Nanoparticle production occurred by mild polyelectrolyte complexation, requiring the chemical modification of LBG. Three LBG derivatives were synthesized, namely a positively charged ammonium derivative (LBGA) and negatively charged sulfate (LBGS) and carboxylate (LBGC) derivatives. These were characterized by Fourier-transform infrared spectroscopy, elemental analysis, nuclear magnetic resonance spectroscopy, gel permeation chromatography, and x-ray diffraction. As a pharmaceutical application was aimed, a toxicological analysis of the derivatives was performed by both MTT test and LDH release assay.

Several nanoparticle formulations were produced using LBGA or chitosan (CS) as positively charged polymers, and LBGC or LBGS as negatively charged counterparts, producing nanoparticles with adequate properties regarding an application in oral immunization.

A new and never yet reported hetero arylidene-9(10H)-anthrone structure (4) was unexpectedly isolated on reaction of 1,2-dimethyl-3-ethylimidazolium iodide (2) and 9-anthracenecarboxaldehyde (3) under basic conditions. Its structure was unequivocally attributed by X-ray crystallography. No cytotoxicity in human healthy fibroblasts and in two different cancer cell lines was observed indicating its applicability in biological systems. Compound 4 interacts with CT-DNA by intercalation between the adjacent base pairs of DNA with a high binding affinity (Kb = 2.0(± 0.20) x 105 M-1) which is 10x higher than that described for doxorubicin (Kb = 3.2 (±0.23) × 104 M-1). Furthermore, compound 4 quenches the fluorescence emission of GelRed-CT-DNA system with a quenching constant (KSV) of 3.3(±0.3) x 103 M-1 calculated by the Stern-Volmer equation.

Biodegradable polyurethanes have been studied as scaffolds for tissue engineering due to their adjustable physico-chemical properties. In this work, we synthesized a biodegradable gelatin-based poly(urethane urea) using polycaprolactone-diol, as soft segment, and isophorone diisocyanate and gelatin from cold water fish skin as hard segment. The synthesis was confirmed by Fourier transform infrared spectroscopy and proton nuclear magnetic resonance and the influence of the amount of gelatin introduced in the polymer backbone was analyzed by thermal analysis. Gelatin-based poly(urethane urea) electrospun fibrous mats and solvent cast films were then produced and their physico-chemical and biological properties studied. They present an amorphous structure, elastomeric behavior and water contact angles typical of hydrophobic surfaces. Hydrolytic degradation was analyzed in phosphate buffer saline (PBS), lipase and trypsin solutions. No mass changes were detected during 37 days in PBS and trypsin while significant degradation by lipase was observed. Human foetal foreskin fibroblasts were seeded on the fibrous mats and films. Populations were evaluated by colorimetric cell viability assays and morphology by fluorescence imaging. The substrates supported cell adhesion and proliferation. The novel gelatin-based poly(urethane urea) fibrous mats offer attractive physico-chemical and biological properties for soft tissue engineering applications.

Gene knock-out studies on Geobacter sulfurreducens have shown that the monoheme c-type cytochrome OmcF is essential for the extracellular electron transfer pathways involved in the reduction of iron and uranium oxy-hydroxides, as well as, on electricity production in microbial fuel cells. A detailed electrochemical characterization of OmcF was performed for the first time, allowing attaining kinetics and thermodynamic data. The heterogeneous electron transfer rate constant was determined at pH 7 (0.16 ± 0.01 cm s−1) indicating that the protein displays high electron transfer efficiency compared to other monoheme cytochromes. The pH dependence of the redox potential indicates that the protein has an important redox-Bohr effect in the physiological pH range for G. sulfurreducens growth. The analysis of the structures of OmcF allowed us to assign the redox-Bohr centre to the side chain of His47 residue and its pKa values in the reduced and oxidized states were determined (pKox = 6.73; pKred = 7.55). The enthalpy, entropy and Gibbs free energy associated with the redox transaction were calculated, pointing the reduced form of the cytochrome as the most favourable. The data obtained indicate that G. sulfurreducens cells evolved to warrant a down-hill electron transfer from the periplasm to the outer-membrane associated cytochrome OmcF.

As consumption of fish and fish-based foods increases, non-destructive monitoring of fish freshness also becomes more prominent. Fish products are very perishable and prone to microbiological growth, not always easily detected by organoleptic evaluation. The analysis of the headspace of fish specimens through gas sensing is an interesting approach to monitor fish freshness. Here we report a gas sensing method for monitoring Tilapia fish spoilage based on the application of a single gas sensitive gel material coupled to an optical electronic nose. The optical signals of the sensor and the extent of bacterial growth were followed over time, and results indicated good correlation between the two determinations, which suggests the potential application of this simple and low cost system for Tilapia fish freshness monitoring.

Abstract Electrogenic bacteria, such as Geobacter, can couple the oxidation of carbon sources to the reduction of extracellular electron acceptors; such acceptors include toxic and radioactive metals, as well as electrode surfaces, making Geobacter a suitable candidate for applied use in bioremediation and bioenergy generation. Geobacter metallireducens is more promising in this regard than the better studied Geobacter sulfurreducens, as it has more efficient Fe (III) reduction rates and can respire nitrate to ammonia. The operon responsible for nitrate reductase activity in G. metallireducens includes the gene encoding the cytochrome PpcF, which was proposed to exchange electrons with nitrate reductase. In the present work, we perform a biochemical and biophysical characterization of PpcF. Spectroscopic techniques, including circular dichroism (CD), UV-visible, and nuclear magnetic resonance (NMR) revealed that the cytochrome is very stable (Tm > 85 °C), contains three low-spin hemes, and is diamagnetic (S=0) and paramagnetic (S=1/2) in the reduced and oxidized states, respectively. The NMR chemical shifts of the heme substituents were assigned and used to determine the heme core architecture of PpcF. Compared to the PpcA-family from G. sulfurreducens, the spatial disposition of the hemes is conserved, but the functional properties are clearly distinct. In fact, potentiometric titrations monitored by UV-visible absorption reveal that the reduction potential values of PpcF are significantly less negative (-56 and -64 mV, versus the normal hydrogen electrode at pH 7.0 and 8.0, respectively). NMR redox titrations showed that the order of oxidation of the hemes is IV-I-III a feature not observed for G. sulfurreducens. The different redox properties displayed by PpcF, including the small redox-Bohr effect and low reduction potential value of heme IV, were structurally rationalized and attributed to the lower number of positively charged residues located in the vicinity of heme IV. Overall, the redox features of PpcF suggest that biotechnological applications of G. metallireducens may require less negative working functional redox windows than those using by G. sulfurreducens.

Nano-Fe3O4-synthetic talc gel was used as filler in the synthesis of waterborne polyurethane/Fe3O4-synthetic talc nanocomposites. This filler presents numerous edges (Si–O and Mg–O) and OH groups easily forming hydrogen bonds and polar interaction with water conferring hydrophilic character, consequently improving filler dispersion within a water-based matrix. Yet, the use of waterborne polyurethane (WPU) as matrix must be highlighted due to its environmentally friendly characteristics and low toxicity compared to solvent-based product. Fe3O4-synthetic talc-nanofillers were well dispersed into the polyurethane matrix even at high filler content as supported by XRD and TEM analyses. NMR indicates the interaction of filler OH groups with the matrix. For all nanocomposites, one can see a typical ferromagnetic behavior below Curie temperature (about 120 K) and a superparamagnetic behavior above this temperature. The use of Fe3O4-synthetic talc for obtaining magnetic nanocomposites resulted in improved materials with superior mechanical properties compared to solvent-based nanocomposites.

The aim of this work was to determine the physico-chemical characteristics of the stained-glass windows into the 19th century of two mausoleums located in the city of Belém do Pará (Brazil), and to evaluate their state of conservation. The glass chemical composition was determined by WXRF and SEM/EDS. The samples’ morphology and the microorganisms’ identification were carried out by optical microscopy. The results indicated that the samples were soda-lime silicate glass, with approximately 70wt. % of SiO2, which contributed to the resistance of the stained glass to the weathering. The concentration of Na2O was normally twice the K2O, which contrasts with the composition of other panels produced during the same period, as reported in the literature. The biofilm is composed by cyanobacteria and rotifers. Overall, the panels analysed were in a good state of conservation, despite their exposure to tropical climate conditions for more than a century with no preventive measures whatsoever. Resumen El objetivo del presente trabajo fue determinar las características físico-químicas de las vidrieras del siglo XIX correspondientes a dos mausoleos ubicados en la ciudad de Belém do Pará (Brasil) para evaluar su estado de conservación. La composición química del vidrio fue determinada por WXRF y SEM/EDS. La morfología de las muestras y la identificación de los microorganismos fueron realizadas por microscopia óptica. Los resultados indicaron que las muestras eran vidrios de silicato sódico-cálcico, con aproximadamente el 70% en peso de SiO2, lo que aumentó la resistencia a la corrosión de los vidrios de estas vidrieras. La concentración de Na2O fue normalmente el doble que de K2O, lo que contrasta con la composición de otros paneles producidos durante el mismo período, de acuerdo con la literatura. El biofilm presentó cianobacterias y rotíferas. En general, los paneles analizados presentaban un buen estado de conservación, a pesar de su exposición a las condiciones climáticas tropicales durante más de un siglo, sin las medidas de conservación preventivas.

G. metallireducens bacterium has highly versatile respiratory pathways that provide the microorganism an enormous potential for many biotechnological applications. However, little is known about the structural and functional properties of its electron transfer components. In this work, the periplasmic cytochrome PpcA from G. metallireducens was studied in detail for the first time using complementary biophysical techniques, including UV–visible, CD and NMR spectroscopy. The results obtained showed that PpcA contains three low-spin c-type heme groups with His-His axial coordination, a feature also observed for its homologue in G. sulfurreducens. However, despite the high sequence homology between the two cytochromes, important structural and functional differences were observed. The comparative analysis of the backbone, side chain and heme substituents NMR signals revealed differences in the relative orientation of the hemes I and III. In addition, redox titrations followed by visible spectroscopy showed that the redox potential values for PpcA from G. metallireducens (−78 and −93 mV at pH 7 and 8, respectively) are considerably less negative. Overall, this study provides biochemical and biophysical data of a key cytochrome from G. metallireducens, paving the way to understand the extracellular electron transfer mechanisms in these bacteria.

Geobacter sulfurreducens is a dissimilatory metal-reducing bacterium that exhibits an enormous respiratory versatility, including the utilization of several toxic and radioactive metals as electron acceptors. This versatility is also replicated in the capability of the most abundant cytochrome in G. sulfurreducens, the periplasmic triheme cytochrome PpcA, to reduce uranium, chromium and other metal ions. From all possible electron transfer pathways in G. sulfurreducens, those involved in the iron reduction are the best characterized to date. In a previous work we provided structural evidence for the complex interface established between PpcA and the electron acceptor Fe(III)-citrate. However, genetic studies suggested that this acceptor is mainly reduced by outer membrane cytochomes. In the present work, we used UV-visible measurements to demonstrate that PpcA is able to directly reduce the electron acceptor ferric nitrilotriacetic acid (Fe-NTA), a more outer membrane permeable iron chelated form. In addition, the molecular interactions between PpcA and Fe-NTA were probed by Nuclear Magnetic Resonance (NMR) spectroscopy. The NMR spectra obtained for natural abundance and 15N-enriched PpcA samples in the absence and presence of Fe-NTA showed that the interaction is reversible and encompasses a positively charged surface region located in the vicinity of the heme IV. Overall, the study provides for the first time a clear illustration of the formation of an electron transfer complex between PpcA and a readily outer-membrane permeable iron chelated form. The structural and functional relationships obtained explain how a single cytochrome is designed to effectively interact with a wide range of G. sulfurreducens electron acceptors, a feature that can be explored for optimal bioelectrochemical applications.

Highly porous monolithic alumina columns find a wide variety of applications, including in chromatography, due to increased surface area and good accessibility to the ligands and reduced diffusional hindrances. Several modelling approaches have been applied to describe experimentally observed flow behaviour in such materials, which morphology plays a key role in determining their hydrodynamic and mass transfer properties. In this work, a direct computational fluid dynamics (CFD) modelling approach is proposed to simulate flow behaviour in monolithic porous columns. The morphological structure of a fabricated alumina monolith was first reconstructed using 3D X-ray tomography data and, subsequently, OpenFOAM, an open-source CFD tool, was used to simulate the essential parameters for monoliths’ performance characterisation and optimisation, i.e. velocity and pressure fields, fluid streamlines, shear stress and residence time distribution (RTD). Moreover, the tortuosity of the monolith was estimated by a novel method, using the computed streamlines, and its value (∼1.1) was found to be in the same range of the results obtained by known experimental, analytical and numerical equations. Besides, it was observed (for the case of the monolith studied) that fluid transport was dominated by flow heterogeneities and advection, while the shear stress at pore mouths was significantly higher than in other regions. The proposed modelling approach, with expected high potential for designing target materials, was successfully validated by an experimentally obtained residence time distribution (RTD).

The Cathedral of León has one of the most important ensembles of medieval stained glass windows in Europe; however, most of them have been altered by atmospheric weathering. The main objective of this study was the characterization of a set of glass samples from the Cathedral of León, the comparison with glasses from previous interventions in the cathedral and the study of the relation between the alteration pathologies, the chemical composition of the glasses and the environment in which they were placed. The samples were characterized by means of binocular microscopy, scanning electron microscopy and energy dispersive X-ray spectrometry, visible spectrophotometry, X-ray fluorescence spectrometry and X-ray diffraction. The main alteration of glasses exposed until the 19th century was the formation of pits by dealkalinization, while the glasses exposed until the present formed CaSO4 deposits as a consequence of the synergic effect of rainwater and gaseous pollutants. Glasses altered by the browning of manganese were also characterized. Resumen La Catedral de León posee una de las colecciones de vidrieras medievales más importantes de Europa; sin embargo, muchos de los vidrios se han alterado por degradación atmosférica. El objetivo principal de este estudio fue la caracterización de un conjunto de vidrios procedentes de la Catedral de León, su comparación con vidrios procedentes de intervenciones previas en la catedral y el estudio de la relación entre las patologías de alteración, la composición química del vidrio y el medio en el que estuvieron expuestas. Las muestras se caracterizaron mediante lupa binocular, microscopía electrónica de barrido y microanálisis de dispersión de energía de rayos X, espectrofotometría visible, espectrometría de fluorescencia de rayos X y difracción de rayos X. La alteración principal de los vidrios expuestos hasta el s. xix consistió en la formación de picaduras por desalcalinización, mientras que en los vidrios expuestos hasta la actualidad se formaron depósitos de CaSO4 como consecuencia del efecto sinérgico de la lluvia y los gases contaminantes. También se han caracterizado vidrios alterados por el enmarronamiento del manganeso.

Blends of rice waste streams were submitted to co-gasification assays. The resulting chars (G1C and G2C) were characterized and used in Cr(III) removal assays from a synthetic solution. A Commercial Activated Carbon (CAC) was used for comparison purposes. The chars were non-porous materials mainly composed by ashes (68.3–92.6% w/w). The influences of adsorbent loading (solid/liquid ratio – S/L) and initial pH in Cr(III) removal were tested. G2C at a S/L of 5 mg L−1 and an initial pH of 4.50 presented an uptake capacity significantly higher than CAC (7.29 and 2.59 mg g−1, respectively). G2C was used in Cr(III) removal assays from an industrial wastewater with Cr(III) concentrations of 50, 100 and 200 mg L−1. Cr(III) removal by precipitation (uptake capacity ranging from 11.1 to 14.9 mg g−1) was more effective in G2C, while adsorption (uptake capacity of 16.1 mg g−1) was the main removal mechanism in CAC.