Tesi di Dottorato
Permanent URI for this communityTesi di Dottorato
Browse
10 results
Search Results
Item Optical sectioning microscopies and forester resonance energy transfer as biological imaging techniques to overcome the problem of spectral overlap(2017-05-03) Gary, Ramla; Bartolino, Roberto; Barberi, RiccardoItem <> study wind behavior from the micro to the mesoscale of different temporal and spatial horizons: turbulent regime, mean and climate(2014-11-13) Tiriolo, Luca; Bartolino, Roberto; Sempreviva, Anna Maria; Carbone, VincenzoItem Molecular simulation of transport proteins in interaction with physiological and pharmacological ligands(2014-11-13) Evoli, Stefania; Bartolino, Roberto; Carbone, Vincenzo; Guzzi, Rita; Rizzuti, BrunoMolecular complexes of transport proteins with small compounds have been studied by using docking techniques and molecular dynamics simulations. The macromolecules considered are β- lactoglobulin and albumin, i.e. the most abundant proteins in bovine milk and human blood serum, respectively. The ligands are long-chain fatty acids of different length and ibuprofen, a molecule of pharmaceutical interest. Simulations of β-lactoglobulin with fatty acids, ranging from caprylic to stearic acid, revealed the key protein residues that contribute to the binding process. In particular, a rationale was found for the high binding affinity of both stearic and palmitic acid compared to shorter lipids. Moreover, the location of two low-affinity external binding sites was predicted for palmitic acid, by comparing docking results with those obtained for vitamin D3, for which an external site has already been identified in crystallography. For human serum albumin, docking results suggest different candidate binding locations for both charged and neutral ibuprofen. An alchemical free energy approach has been used to estimate the binding affinity for each pose. The results show that charged ibuprofen has a greater affinity for albumin compared to the ligand in the neutral form, suggesting that the former corresponds to the physiological binding state. The simulation findings were compared to experimental results and show an overall good agreement, predicting details of the protein-ligand interaction that include binding geometries and contacts with specific amino acid residues. The overall findings reveal significant features of the binding of well-known ligands to two extensively investigated transport proteins, and show how computational tools can be used to support experimental techniques in a variety of cases.Item Atomic forcemicroscopy of corneal biomechanics(2014-11-28) Labate, Cristina; Bartolino, Roberto; Versace, Carlo; Barberi, Riccardo; De Santo, Maria P.Item Advanced numerical models for highly frustrated liquid crystalline phases(2014-11-03) de Jesus, Caldera Teresita; Bartolino, Roberto; Versace, Carlo C.; Barberi, Riccardo; Lombardo, GiuseppeItem Complexity in climate(2012-12-25) Capparelli, Vincenzo; Bartolino, Roberto; Carbone, VincenzoItem Optical systems for diagnostics: Near-Infrared Imaging technique for detection of dental demineralisation(2012-11-30) Salsone, Silvia; Versace, Carlo; Lombardo, Giuseppe; Zakian, Christian; Bartolino, RobertoIn dentistry, a correct detection of caries severity is still a challenging descision-making task that crucially a ects the choice for the best treatment plan. The challenge is to nd both the most objective parameters to detect caries at di erent stages (from an early reversibile stage to a severe one) and the most reliable method(s) that should be used to distinguish these stages. Currently, methods used in clinics are visual inspection, aided with light probe and pick inspection tools, and radiography. The main issue rising by the use of these methods is that both of them are subjective, with possibility for intra- and inter-examiner variability. For this reason, radiography needs an extreme care of interpretation especially when assessing occlusal caries. Visual methods, instead, are a ected by confounding factors, such as stain or uorosis, a ecting the accurate assessment of early caries lesions. Radiography, moreover, should be performed with care considering that the emission of ionising radiation may cause malignant change in tissues, especially for young age patients and are counter-indicated during pregnancy. They are also inadequate for the detection of initial caries and to locate the lesions looking at the superimposition of the tooth along its buccal-lingual axis. The aim of this study was to overcome the limits of the current detection techniques, o ering a non-invasive, objective method for the detection of caries at any stage of the demineralisation process. The proposed method measures the near-infrared (NIR) re ectance response of the tooth at three speci c wavelengths. It is then possible to investigate properties of the sample at the surface and in depth and get an image that maps the lesions on the occlusal view of the sample when combining these wavelengths. Due to the properties of the NIR light, this method is non-invasive, non-contact and allows for detection both at the enamel and at the dentine level. The NIR method o ers objective supporting information to quantify and detect dental caries and is especially suitable for areas a ected by confounding factors, such as stain. The objective of the study was to design and implement a NIR multispetral imaging system, developing e cient image analysis algorithms. In order to prove this objective, an in vitro validation of the technique against gold standard histology was performed together with a comparison to other detection methods - International Caries Detection and Assessment System (ICDAS - clinical visual inspection), bre optic transillumination method (FOTI - visual inspection with light probe), radiography and Quantitative Light-induced Fluorescence method (QLF), used in clinics or in research. A total of 112 teeh, molars and premolars, with di erent lesion severities were used for this study. Histologcal sections were obtained to con rm the lesion severities and used as a gold standard to compare the sensitivity and speci cty among techniques. Visual inspection methods recorded the highest values of sensitivity (ICDAS: >99%, FOTI: 93%) and speci city to dental caries (FOTI: >99%, ICDAS: 90%). However, these methods could have been highly facilitated by the in-vitro viewing of the samples. Sensitivity to dental caries was higher for NIR (91%) than for QLF (88%) and radiography (63%) while speci city was higher for radiography (81%) than for NIR (73%) and QLF (63%). The results from this study suggest that the NIR method has the ability to detect dental caries when other methods fail, providing an alternative to assist in the decision-making process with the further advantage of removing the confounding e ect of stain. This method can enhance patient communication and o ers an objective and safe alternative to ionising radiation methods.Item Properties of biomolecules at the interfaces: studies and characterization of chromonic mesogens, from the basis to applications(2013-11-28) Tone, Caterina; Bartolino, Roberto; Versace, Carlo; Ciuchi, FedericaThe study of the interaction between molecules, in particular biological molecules and liquid crystals (LC), has experienced a huge growth in the recent years because of the development in devices engineering applied not only in photonics but also in the biomedical eld. In order to design more e cient LC devices, it is rst necessary to understand the behavior and properties of newly-synthesized liquid crystals and to garner a more indepth understanding of currently-existing LCs in order to answer pending questions about them. The aim of this thesis work, is to better understand the interactions involved at the interface between liquid crystals and other materials, whatever is their nature, i.e. polymeric or biological. We started studying the e ect of di erent con ning surfaces on the alignment of a special class of lyotropic liquid crystals, called \chromonics", which, in addition of LC properties, are biocompatible. Di erently from the most common liquid crystals, i.e. thermotropic LC, the mesogens that constitute the chromonic LC phases are not amphiphilic, but they are \plan-like" aromatic compound. This class of molecules embraces not only dyes and drugs, but also DNA and its bases. Using the knowledge acquired with chromonic mesogen, we tried to understand a more complicate system, such as the phenomena involved at the biomolecules decorated-liquid crystals lms interfaces. More speci cally, it is possible to divide the work in two macro-parts. The rst part concerns the alignment of a chromonic molecule, \disodium cromoglycate" (DSCG). The study of chromonic LC behaviour in con ned geometries and its physical properties, could be a model for more complex biological assemblies. Hence, we demonstrated the role of alignment layer's surface energy in the alignment of nematic phase of DSCG, achieving both alignments and for the rst time, a stable-in-time homeotropic anchoring of this LC solution. With the knowledge acquired from DSCG, we were able to align also DNA bases liquid crystal solutions. In particular, guanosine monophosphate in pre-cholesteric and cholesteric liquid crystals phases were perfectly aligned homeotropically without means of external elds, as was done until now, and partially planar aligned. Moreover, we observed that if ionic and/or silver doped solutions are added to the LC guanosine phases, it is possible to control the pitch of the cholesteric phase, modifying the helix structure. Instead, varying the nature of the con ning surfaces, in such conditions, it is possible to obtain guanosine vesicles. Other studies have been carried out on new chromonic complexes, synthesized at Chemistry Department of UNICAL, with possible application as anticancer drugs. A complete characterization of these compounds were done (XRD, phase diagrams, etc) and also for these compounds, we developed a\route"to drive the alignment, particularly important for future application in biophotonic devices. The second part of the work is focused on LC based biosensors. From the biotechnological and biomedical applications point of view, the studies on interactions of proteins with lipids are an area of fundamental interest, due to enormous biological importance. In fact, studies on biosensor devices are tremendously increased in recent years, focusing the attention also on nding low cost raw materials with high e ciency: liquid crystals, thanks to their high sensitivity to the external conditions, represent the best candidate. It has been demonstrated that aqueous interface of LC has an instantaneous response when exposed to phospholipids. This is a good base to study the interaction between biomolecules using LC as probe. Starting from the results found in literature, we studied the e ect of phospholipids on protein decoratede-liquid crystal interfaces by means of optical microscopy and FT-IR measurements. The rst technique allowed us to observe the response of decorated LC lm when exposed to phospholipids vesicles, while the second, gave us insight on conformational changes involved in secondary structure of the protein in function of the time of interaction between protein and LC, and the pH of the surrounding environment. The results obtained show a new methods to report speci c binding of vesicles on protein decorated interfaces.Item Absorpitive losses mitigation in gain-plasmon hybrid systems as optical metamaterials(2013-11-29) Rashed, Alireza Rahimi; Bartolino, Roberto; Versace, Carlo C.; Strangi, GiuseppeIn the past decade, plasmonic nanoparticles (NPs) have gained a lot of interest due to their exceptional and fascinating properties which have been accomplishing vital role in emerging science and technology towards multifunctional applications. The extensive current research efforts in nanoplasmonics trigger towards various opto-electronic and medical applications such as invisibility, perfect lens, increasing the efficiency of solar cells, designing and extra-sensitive single-particle detection of biomolecular recognition and in particular optical metamaterials. The negative real part and the low value of the imaginary part of dielectric permittivity are crucial for applications of nanoparticles as subunits of optical metamaterials. However, the performance of plasmonic nanostructures is significantly limited by the intrinsic and strong energy dissipation in metals, especially in the visible range. In fact, regardless of the challenges to synthesize plasmonic nanostructures, the path to use them as building blocks of optical metamaterial is crossing through the finding a solution to mitigate their optical losses. In this research thesis, it is demonstrated experimentally that the incorporation of gain material such as organic dye molecules and quantum dots in close proximity of enhanced local fields of various properly designed plasmonic systems makes it possible to induce resonant energy transfer processes from gain units to plasmonic nanoparticles, to accompanish loss compensation in optical metamaterials. Steady-state experiments and time resolved spectroscopy along with modification of Rayleigh scattering and optical transmission of a probe beam as a function of impinging energy are crucial evidences of mitigation of absorptive losses in different gain doped plasmonic systems The strategy that has been followed here towards mitigation of absorptive losses in optical metamaterials acts at different spatial scales from nano to macro (see Figure 1). The systems at nano-scale (10-100 nm) are based on dispersion of NPs, in particular, gain assisted (nanoparticle-dye dispersion), gain-functionalized core-shell gold NPs (encapsulated dye molecules into the shell) and dye grafted gold core multimeric nanostructures. The study of such nano-composites allows to recognize experimentally how the parameters such as the geometry and size of the metal nanostructures, inter-particle distance, overlap between emission spectrum of gain material and plasmon band of metal NPs, concentration and quantum yield of donor molecules are playing an important role to create more efficient nonradiative RET processes from donor molecules to acceptors. Figure 1 The followed spatial stages on this research study ranged from (a) nano-scale and (b) mesco scale towards (c) macro scale. The obtained results in nano-scale generate further motivations to move forward to study meso-scale (100-900 nm) plasmonic systems which include both dispersion (nanoshell composites) and bulk (periodic layers of gain materials and lossy metal elements) systems. The nanoshells which are consisted of dye doped dielectric core coated gold shell dispersed in ethanol solution are designed with an optimized ratio of core diameter and metallic shell thickness. The time resolved fluorescence spectroscopy results along with pump-probe experiments on nanoshells are convincing evidences for optical loss mitigation. Finally in third stage, the optical properties of gain-plasmon composites dispersed in PDMS host matrix as an example for bulk samples at the macroscopic scale (1 μm and beyond) have been investigated. The achieved results on this stage can help to design and fabricate such plasmonic structures that lead from fundamental physics towards practical applications. In this regard, the first four chapters provide the background concerning the main elements of this research work. The first chapter contains an introduction to the metamaterials. Second chapter describes the optical properties of plasmonic nanostructures. In third chapter, gain materials and the optical processes beyond these materials have been investigated. The fourth chapter deals with the optical properties of hybrid systems consisted of active materials and nano-plasmonic elements. After providing a brief introduction regarding the applied setups and instruments in this research study in chapter five, the last three chapters represent the acquired experimental results in each mentioned spatial scale. In chapter six, the optical properties of nano-scaled gain-plasmon systems in solution including gain-assisted, gainfunctionalized and dye grafted multimeric samples are investigated. Chapter seven explores the optical characteristics of dispersion of nanoshell sample as an example of the study in mesoscale. Finally, the thesis is completed with the study of the optical features of macro-scaled bulk samples based on core–shell type quantum dots and gold NPs dispersed in PDMS, and a short conclusion of this research study. This study emphasizes effective progress in materials science and paves the way towards further promising scientific research aimed to enable the wide range of electromagnetic properties of plasmonic metamaterialsItem Strategies to control linear anisotropy and chirality in polymeric materials:from the basic issues to the micro-devices developments(2016-10-05) Lepera, Eugenia; Bartolino, Roberto; Versace, Carlo C.; Cipparrone, GabrieleThe development of devices with increasing levels of functionality represents an important technological issue. To this aim, innovative materials with tunable functionalities play a crucial role. The challenge is to obtain multifunctional materials through simple procedures with high performance and low cost, and eventually external control parameters. Moreover the understanding of multifunctionality of materials is hence an exciting scientific opportunity. For these purpose, the main objectives of the present work have been to explore two main strategies. In the first one, azobenzene based materials and their light induced functionalities has been exploited to develop microdevices for polarimetric applications. Already know effects of linear and circular photoinduced optical anisotropies in azobenzene based polymers was investigated coupling the materials properties with holographic techniques, both to characterize the photoinduced properties of the materials and to develop diffractive devices useful for the above cited applications. The second topic is addressed towards the development of a materials science approach to build up polymeric matrices with controllable supramolecular chiral structures and subnanometric cavities. Both explored features are connected to intriguing topics as chirality and small size cavities. Their chirooptical properties and supramolecular structures suggest high potentiality for development of chiral sensors or filtration devices. Key words: micro-devices, azo-polymers, polarization holography, syndiotactic polystyrene, supramolecular chirality.