Nanostructured lipid carriers for nose-to-brain delivery in neurodegenerative diseases therapy

191 p.

Study of nanostructured targets for plasma production via laser ablation

Metal nanowires (NWs) - nanostructures 20-100 nm in diameter and up to tens of micrometers long - behave as waveguides when irradiated with light with wavelength much greater than their diameter. This is due to collective excitations of free electrons (plasmons) in the metal which couple to light and travel on the surface of the nanowire. This effect can be used to efficiently absorb laser pulses to produce dense and hot plasma on special nanostructured targets with metal nanowires vertically aligned on the surface. In this thesis work, nanostructured targets with different parameters (length, diameter, metal and fabrication process) have been irradiated with infrared laser light. X-ray flux emitted by the cooling plasma is measured during irradiation, and the depth of craters formed on the target is measured later. This data is used to choose which target parameters are best for plasma production. Different targets are compared with each other and against a control, non-nanostructured (bulk) target. As will be shown, highly significant (> 5 sigma) differences are found between targets with different nanostructures, and between nanostructured and bulk target. This differences are very difficult to explain whithout accounting for the nanostructures in the targets. Therefore, data collected and analized in this thesis work supports the hypotesys that nanostructured targets perform better than bulk targets for laser plasma production purposes, and provides useful indications for optimization of NWS' parameters.

A comparative study of alginate beads and an ion-exchange resin for the removal of heavy metals from a metal plating effluent

The capacity of dry protonated calcium alginate beads to sorb metals from an industrial effluent was studied and compared with a commercial ion-exchange resin (Lewatit TP 207). Both sorbents decreased zinc, nickel, iron and calcium concentrations in the effluent, and released sodium during treatment. Alginate beads removed lower amounts of heavy metals than the resin, but exhibited faster uptake kinetics. Zinc desorption from the sorbents was achieved in 30 minutes using 0.1 M HCl or 0.1 M H(2)SO(4). Desorption ratios with these acids varied between 90 and 100% for alginate, and 98 to 100% for the ion-exchange resin. Reusability tests with HCl showed that alginate beads can stand acid desorption and recover binding capacity. Overall, the comparison of dry protonated alginate beads with the resin supports the potential of the biosorbent for the treatment of industrial effluents.

Procesos hopping a través del modelo difusional en materiales nanocristalinos usados para aplicaciones fotovoltaicas

Se presentan los modelos de hopping de rango variable (variable range hopping; VRH), vecinos cercanos (nearest neighbor hopping; NNH) y barreras de potencial presentes en las fronteras de grano; como mecanismos de transporte eléctrico predominantes en los materiales semiconductores para aplicaciones fotovoltaicas. Las medidas de conductividad a oscuras en función de temperatura fueron realizadas para región de bajas temperaturas entre 120 y 400 K con Si y compuestos Cu3BiS2 y Cu2ZnSnSe4. Siguiendo la teoría de percolación, se obtuvieron parámetros hopping y la densidad de estados cerca del nivel de Fermi, N(EF), para todas las muestras. A partir de los planteamientos dados por Mott para VRH, se presentó el modelo difusional, que permitió establecer la relación entre la conductividad y la densidad de estados de defecto o estados localizados en el gap del material. El análisis comparativo entre modelos, evidenció, que es posible obtener mejora hasta de un orden de magnitud en valores para cada uno de los parámetros hopping que caracterizan el material.

Development and optimisation of protocols for surface cleaning of cultural heritage metals

The conservation and valorisation of cultural heritage is of fundamental importance for our society, since it is witness to the legacies of human societies. In the case of metallic artefacts, because corrosion is a never-ending problem, the correct strategies for their cleaning and preservation must be chosen. Thus, the aim of this project was the development of protocols for cleaning archaeological copper artefacts by laser and plasma cleaning, since they allow the treatment of artefacts in a controlled and selective manner. Additionally, electrochemical characterisation of the artificial patinas was performed in order to obtain information on the protective properties of the corrosion layers. Reference copper samples with different artificial corrosion layers were used to evaluate the tested parameters. Laser cleaning tests resulted in partial removal of the corrosion products, but the lasermaterial interactions resulted in melting of the desired corrosion layers. The main obstacle for this process is that the materials that must be preserved show lower ablation thresholds than the undesired layers, which makes the proper elimination of dangerous corrosion products very difficult without damaging the artefacts. Different protocols should be developed for different patinas, and real artefacts should be characterised previous to any treatment to determine the best course of action. Low pressure hydrogen plasma cleaning treatments were performed on two kinds of patinas. In both cases the corrosion layers were partially removed. The total removal of the undesired corrosion products can probably be achieved by increasing the treatment time or applied power, or increasing the hydrogen pressure. Since the process is non-invasive and does not modify the bulk material, modifying the cleaning parameters is easy. EIS measurements show that, for the artificial patinas, the impedance increases while the patina is growing on the surface and then drops, probably due to diffusion reactions and a slow dissolution of copper. It appears from these results that the dissolution of copper is heavily influenced by diffusion phenomena and the corrosion product film porosity. Both techniques show good results for cleaning, as long as the proper parameters are used. These depend on the nature of the artefact and the corrosion layers that are found on its surface.

Initial growth of sunflower in soils with high concentrations of boron and heavy metals.

Phytoremediation studies have been conducted in an area contaminated by heavy metals, located in Piracicaba - SP, Brazil. This area was contaminated accidentally by the addition of auto scrap shredding to the soil and was limed later to reduce heavy metal mobility in the environment. Previous characterization showed that it also presents high concentration of boron, which has limited the initial plant development of some species. As sunflower plants require a high boron supply and the literature describes its use in the phytoremediation of soils contaminated with heavy metals under some conditions, the aim of this work was to evaluate its potential for the remediation of this area. In the present study, the results of preliminary tests are presented, aiming at the evaluation of sunflower plant germination and its initial development when cultivated in the contaminated soil described. Two sunflower hybrids were sown in soils treated with different rates of boron and in the soil from the contaminated area in study. The results showed that sunflower plants had a normal initial development, even in the soil from the contaminated area. Therefore, sunflower is a promising crop and further studies will be developed to evaluate the sunflower efficiency in phytoextraction or phytostabilization of heavy metals in areas where boron contamination also occurs, as is the case in the study area.

In vitro effects of metals on the acid phosphatase from the microalgae Pseudokirchneriella subcapitata.

2008

Initial growth of sunflower in soils with high concentrations of boron and heavy metals.

2008

Assessment of heavy metals in soils of a vineyard region with the use of principal component analysis.

Agricultural management with chemicals may contaminate the soil with heavy metals. The objective of this study was to apply Principal Component Analysis and geoprocessing techniques to identify the origin of the metals Cu, Fe, Mn, Zn, Ni, Pb, Cr and Cd as potential contaminants of agricultural soils. The study was developed in an area of vineyard cultivation in the State of São Paulo, Brazil. Soil samples were collected and GPS located under different uses and coverings. The metal concentrations in the soils were determined using the DTPA method. The Cu and Zn content was considered high in most of the samples, and was larger in the areas cultivated with vineyards that had been under the application of fungicides for several decades. The concentrations of Cu and Zn were correlated. The geoprocessing techniques and the Principal Component Analysis confirmed the enrichment of the soil with Cu and Zn because of the use and management of the vineyards with chemicals in the preceding decades.

Additive Manufacturing by LPBF and WAAM of metals: correlation between production process, microstructure and mechanical properties

In the most recent years, Additive Manufacturing (AM) has drawn the attention of both academic research and industry, as it might deeply change and improve several industrial sectors. From the material point of view, AM results in a peculiar microstructure that strictly depends on the conditions of the additive process and directly affects mechanical properties. The present PhD research project aimed at investigating the process-microstructure-properties relationship of additively manufactured metal components. Two technologies belonging to the AM family were considered: Laser-based Powder Bed Fusion (LPBF) and Wire-and-Arc Additive Manufacturing (WAAM). The experimental activity was carried out on different metals of industrial interest: a CoCrMo biomedical alloy and an AlSi7Mg0.6 alloy processed by LPBF, an AlMg4.5Mn alloy and an AISI 304L austenitic stainless steel processed by WAAM. In case of LPBF, great attention was paid to the influence that feedstock material and process parameters exert on hardness, morphological and microstructural features of the produced samples. The analyses, targeted at minimizing microstructural defects, lead to process optimization. For heat-treatable LPBF alloys, innovative post-process heat treatments, tailored on the peculiar hierarchical microstructure induced by LPBF, were developed and deeply investigated. Main mechanical properties of as-built and heat-treated alloys were assessed and they were well-correlated to the specific LPBF microstructure. Results showed that, if properly optimized, samples exhibit a good trade-off between strength and ductility yet in the as-built condition. However, tailored heat treatments succeeded in improving the overall performance of the LPBF alloys. Characterization of WAAM alloys, instead, evidenced the microstructural and mechanical anisotropy typical of AM metals. Experiments revealed also an outstanding anisotropy in the elastic modulus of the austenitic stainless-steel that, along with other mechanical properties, was explained on the basis of microstructural analyses.

Nanostructured luminescent chemosensors for environmental and biomedical applications

Nanomaterials are nowadays widely recognised as advantageous sensing tools due to their unique properties. Some natural nanomaterials, such as DNA or hyaluronic acid analysed in this PhD thesis, have an intrinsic biocompatibility that overcomes a series of issues in the field of sensing in biological environments. Therefore, the main aim of this project was to derivatize HA chains with luminescent dyes - both organic and metal complexes - in order to obtain natural polymer-based optical sensors. A derivatization of HA with these moieties was obtained and a photophysical characterization was provided. To prove their sensing ability towards nanomaterials, the interaction with. PluS Nanoparticles, featuring an outer PEG shell, was tested. It was mostly demonstrated that the main features of the luminophores used were present in the HA nanogels as well. For example, HA@Dansyl was proven to be a luminescent probe able to sense different environment polarities. Furthermore, in HA@PA the amount of excimers/monomers emission was found to be relatable to the degree of entanglement of HA chains, that changes upon interactions with nanoparticles. Moreover, two ruthenium bipyridyl derivatives were linked to HA and it was found out that HA interacts with long DNA sequences. Also, the presence of BPA, a small molecule of environmental concern, was detected using (i) an already studied hyaluronic acid derivative with rhodamine (HA@RB) , (ii) a dizinc ruthenium complex coordinating BPA to the metal centres, and (iii) a new probe constituted by PluSNPs@DEAC and HA@RB. Despite all the systems were found to be able to detect BPA, the latter probe presented advantages in terms of sensitivity. Furthermore, the chapter 2 of this thesis is focused on the detection of a NF-κB protein in PC3 cancer cells. via confocal microscopy by following a FRET signal variation on a triplex-hairpin derivatized with a FRET couple of dyes.

“Nanoglial interfaces: nanostructured materials, interfaces and devices to unveil the role of astrocytes in brain function and dysfunction”

The role of non-neuronal brain cells, called astrocytes, is emerging as crucial in brain function and dysfunction, encompassing the neurocentric concept that was envisioning glia as passive components. Ion and water channels and calcium signalling, expressed in functional micro and nano domains, underpin astrocytes’ homeostatic function, synaptic transmission, neurovascular coupling acting either locally and globally. In this respect, a major issue arises on the mechanism through which astrocytes can control processes across scales. Finally, astrocytes can sense and react to extracellular stimuli such as chemical, physical, mechanical, electrical, photonic ones at the nanoscale. Given their emerging importance and their sensing properties, my PhD research program had the general goal to validate nanomaterials, interfaces and devices approaches that were developed ad-hoc to study astrocytes. The results achieved are reported in the form of collection of papers. Specifically, we demonstrated that i) electrospun nanofibers made of polycaprolactone and polyaniline conductive composites can shape primary astrocytes’ morphology, without affecting their function ii) gold coated silicon nanowires devices enable extracellular recording of unprecedented slow wave in primary differentiated astrocytes iii) colloidal hydrotalcites films allow to get insight in cell volume regulation process in differentiated astrocytes and to describe novel cytoskeletal actin dynamics iv) gold nanoclusters represent nanoprobe to trigger astrocytes structure and function v) nanopillars of photoexcitable organic polymer are potential tool to achieve nanoscale photostimulation of astrocytes. The results were achieved by a multidisciplinary team working with national and international collaborators that are listed and acknowledged in the text. Collectively, the results showed that astrocytes represent a novel opportunity and target for Nanoscience, and that Nanoglial interface might help to unveil clues on brain function or represent novel therapeutic approach to treat brain dysfunctions.

Nanostructured piezoelectric materials for the design and development of self-sensing composite materials and energy harvesting devices

The work activities reported in this PhD thesis regard the functionalization of composite materials and the realization of energy harvesting devices by using nanostructured piezoelectric materials, which can be integrated in the composite without affecting its mechanical properties. The self-sensing composite materials were fabricated by interleaving between the plies of the laminate the piezoelectric elements. The problem of negatively impacting on the mechanical properties of the hosting structure was addressed by shaping the piezoelectric materials in appropriate ways. In the case of polymeric piezoelectric materials, the electrospinning technique allowed to produce highly-porous nanofibrous membranes which can be immerged in the hosting matrix without inducing delamination risk. The flexibility of the polymers was exploited also for the production of flexible tactile sensors. The sensing performances of the specimens were evaluated also in terms of lifetime with fatigue tests. In the case of ceramic piezo-materials, the production and the interleaving of nanometric piezoelectric powder limitedly affected the impact resistance of the laminate, which showed enhanced sensing properties. In addition to this, a model was proposed to predict the piezoelectric response of the self-sensing composite materials as function of the amount of the piezo-phase within the laminate and to adapt its sensing functionalities also for quasi-static loads. Indeed, one final application of the work was to integrate the piezoelectric nanofibers in the sole of a prosthetic foot in order to detect the walking cycle, which has a period in the order of 1 second. In the end, the energy harvesting capabilities of the piezoelectric materials were investigated, with the aim to design wearable devices able to collect energy from the environment and from the body movements. The research activities focused both on the power transfer capability to an external load and the charging of an energy storage unit, like, e.g., a supercapacitor.