OPTICAL DETECTION OF MOLECULAR INTERACTIONS ON THE SURFACE OF MATERIALS INDEX-MATCHED TO WATER.

The idea to have highly effective autonomous sensors able to measure and share information about the quality of our environment, and particularly water, in our lakes and rivers, our water supply system and the outputs of municipal and industrial wastewater treatment systems is revolutionary and fascinating. These sensors could be densely deployed at multiple locations, and the information may be available to citizens through the Internet. This idyllic vision, nowadays, is far away from being reality, despite the huge effort made to develop innovative molecular sensors. The main challenges related to the realization of these autonomous sensors network are the biofouling, power supply and compactness. In fact, despite thousands of papers in literature about development of novel nanostractured materials for sensing, for instance, there is still not a single example of any of these device being used in direct contact with water for long-term environmental monitoring. The work presented in this thesis proposes a new kind of optical sensor that combines a fast and low cost method to detect water pollutant with good performance and robustness. In particular, this work is focused on the detection of small molecular pollutants, as oils compounds and surfactants. An innovative aspect of the proposed approach relies on the use of a novel class of materials as sensing substrate which have peculiar and fascinating optical properties: these are amorphous perfluorinated polymers with refractive index similar to that of water. When immersed in aqueous solutions, they provide extremely low reflection or scattering of light, hence they become barely visible. For this reason, this class of materials is called phantom. In this limit, when a thin molecular layer spontaneously adsorbs on the surfaces of these materials, the reflected or scattered light increases, providing the basis for optical detection of molecules. In this work, three different phantom materials made of perfluorinated polymers are exploited in the framework of the detection of water contaminants: a prism, microporous membranes and micro-beads, that represent the building blocks for the assembly of an invisible chromatography column. The membrane and the micro-beads were produced for the first time during this work. The use of fluoropolymer prism substrate for molecular detection was already proposed in recent works to realize label-free biosensors based on the functionalization of the surface with antibodies. Here I extend the exploitation of this system to the detection of molecular pollutant through their adsorption on the bare surface of the fluoropolymer materials, without the need of any surface treatment. Despite the lack of surface functionalization, a selectivity in the adsorption of various classes of molecules is demonstrated

Zinc ions alter morphology and chitin deposition in an ericoid fungus

A sterile mycelium PS IV, an ascomycete capable of establishing ericoid mycorrhizas, was used to investigate how zinc ions affect the cellular mechanisms of fungal growth. Asignificant reduction of the fungal biomass was observed in the presence of millimolar zinc concentrations; this mirrored conspicuous changes in hyphal morphology which led to apical swellings and increased branching in the subapical parts. Specific probes for fluorescence and electron microscopy localised chitin, the main cell wall polysaccharide, on the inner part of the fungal wall and on septa in control specimens. In Zn-treated mycelium, hyphal walls were thicker and a more intense chitin labelling was detected on the transverse walls. Aquantitative assay showed a significant increase in the amount of chitin in metal- treated hyphae

Phantom membrane microfluidic cross-flow filtration device for the direct optical detection of water pollutants

The diffusion of autonomous sensing platforms capable of a remote large-scale surveillance of environmental water basins is currently limited by the cost and complexity of standard analytical methods. In order to create a new generation of water analysis systems suitable for continuous monitoring of a large number of sites, novel technical solutions for fluid handling and detection are needed. Here we present a microfluidic device hosting a perfluorinated microporous membrane with refractive index similar to that of water, which enables the combination of filtration and label-free sensing of adsorbing substances, mainly pollutants, in environmental water samples. The cross-flow design of the microfluidic device avoids the clogging of the membrane due to particulate, whereas molecules with some hydrophobic moiety contained in the crossing flow are partially retained and their adhesion on the inner surface of the membrane yields an increase of light scattering intensity, which can be easily measured using a simple instrument based on Light Emitting Diode illumination. By cycling sample water and pure water as a reference, we demonstrate the detection of 0.5 \uce\ubcM of a model cationic surfactant and regeneration of the sensing surface. The optical response of the membrane sensor was characterized using a simple theoretical model that enables to quantify the concentration of target molecules from the amplitude and kinetics of the measured binding curves. The device was tested with real water samples containing large amount of environmental particles, without showing clogging of the membrane, and enabling nonspecific quantification of adsorbing substances in a few minutes

Vertedero de residuos sólidos urbanos: Pedogénesis comparada entre sitios de una plantación de Eucalyptus camaldulensis Dehnh. y de vegetación herbácea naturalizad

The purpose of this work was compared different levels of pedogenetics process between sites with Eucalyptus camaldulensis plantation and naturalized grass. The trial was installed on landfill soil cover in Villa Domínico, Buenos Aires Province, Argentine, CEAMSE, 34°40’S,50’’; 58°18’45’’W; 4m osl. At five age of trees and forteen of the Landfill was realized the following determination: 1- Physical and Chemicals caracterization of own microsite tree and analogical microsite without trees influence. 2- Biomass root system of trees and naturalized herbaceus vegetation; 3- Microrganims qualitative evaluation in trees rhizosphere and 4- Survival trees and its developpmen as too patologycal and physiological damage. The results showing the antropyc evolution soil with ability to support life on differents espression. It was registred the culturals horizon in the cover landfill generated through the time. Exits the advantage about this process in the microsites tree more than the microsites grass.El objetivo de este trabajo fue comparar distintos niveles de procesos pedogenéticos entre sitios con una plantación de Eucalyptus camaldulensis y otros con vegetación herbácea naturalizada. El experimento se ubicó en la cubierta del vertedero de residuos sólidos urbanos de Villa Domínico, Buenos Aires, Argentina, (34 o 40’ 50’’ S; 58º 18’ 45’’W; 4 m snm). A las edades de seis años de la plantación y 14 del vertedero de residuos sólidos urbanos, fueron realizadas las siguientes determinaciones: 1- Caracterización físico química de micrositios análogos con influencia del árbol y del pastizal naturalizado; 2- Biomasa radicular de árboles y tapiz herbáceo naturalizado; 3- Evaluación cualitativa de microorganismos rizosféricos y 4- Desarrollo y estado sanitario de los árboles. Los resultados mostraron capacidad de soporte biológico producido por una marcada evolución pedogenética antrópica. Se registraron horizontes culturales dentro de la cubierta del vertedero de residuos sólidos urbanos a través del tiempo. Existió una ventaja de estos procesos en los micrositios con árboles respecto de los pastizales

Economic and accounting evaluation of rice milled production chains in Rio Grande do Sul (Brazil) and Uruguay with application of the Policy Analysis Matrix.

201

Emerging applications of label-free optical biosensors

Innovative technical solutions to realize optical biosensors with improved performance are continuously proposed. Progress in material fabrication enables developing novel substrates with enhanced optical responses. At the same time, the increased spectrum of available biomolecular tools, ranging from highly specific receptors to engineered bioconjugated polymers, facilitates the preparation of sensing surfaces with controlled functionality. What remains often unclear is to which extent this continuous innovation provides effective breakthroughs for specific applications. In this review, we address this challenging question for the class of label-free optical biosensors, which can provide a direct signal upon molecular binding without using secondary probes. Label-free biosensors have become a consolidated approach for the characterization and screening of molecular interactions in research laboratories. However, in the last decade, several examples of other applications with high potential impact have been proposed. We review the recent advances in label-free optical biosensing technology by focusing on the potential competitive advantage provided in selected emerging applications, grouped on the basis of the target type. In particular, direct and real-time detection allows the development of simpler, compact, and rapid analytical methods for different kinds of targets, from proteins to DNA and viruses. The lack of secondary interactions facilitates the binding of small-molecule targets and minimizes the perturbation in single-molecule detection. Moreover, the intrinsic versatility of label-free sensing makes it an ideal platform to be integrated with biomolecular machinery with innovative functionality, as in case of the molecular tools provided by DNA nanotechnology

Does fishing have an impact on Maltese maerl grounds?

The sedimentary bottoms off the northeastern coast of the Maltese Islands are important inshore fishing grounds. Between depths of 45m and 80m, these bottoms are characterized by accumulations of unattached calcareous rhodophytes, forming maerl beds. The complex structure of these free-living thalli (rhodoliths) introduces heterogeneity to the otherwise homogenous sedimentary bottoms, thus increasing biotic diversity. Maerl deposits may take hundreds of years to accumulate and their development is strongly correlated with the current and sedimentary regimes and with bottom disturbance, making such beds susceptible to anthropogenic disruption. Two fishing techniques in particular used locally may have an impact on maerl bottoms: parit fishing (bottom-set gill-nets) and bottom trawling using an otter trawl. We investigated the effect of the former by experimental fishing on maerl, and that of the latter by studying rhodolith structure, sediment granulometry, and benthic biodiversity of a 20km2 maerl bed, part of which is regularly trawled. Parit fishing may remove the larger rhodoliths but its impact depends greatly on the strength of the bottom current. The trawled site had more abundant rhodoliths and coarser sediments than the non- trawled site, but a lower sediment organic content. Rhodolith morphology was also different at the two sites. Both sites had a high species richness but low abundance and biomass. Differences in species composition were also noted. These results are discussed in relation to the different environmental characteristics of the two sites, including the role of disturbance, but the relative importance of anthropic activities and natural perturbations is not yet clear.peer-reviewe

Baseline ecological data collection from the marine area around Filfla (Malta, Central Mediterranean Sea)

Acoustic and limited video sampling were carried out in a 1.1 nautical mile-radius area around Filfla, an islet 4.4 to the south-west of Malta, to characterize the benthos and the habitat type distribution. In addition, identified priority areas were sampled during SCUBA diving surveys. A total of 173 species were recorded during the current survey. Rhodophytes were the most represented (29 species), followed by molluscs (25 species). The biotic assemblages recorded from the marine area around Filfla are generally representative of those found in Maltese inshore waters.peer-reviewe