Misure di scivolamento di gocce di gel polimerici su superfici chimicamente omogenee

Il presente lavoro di tesi si propone di studiare lo scivolamento di gocce di poliacrilammide (PAA) in una miscela di acqua e glicerolo a diverse concentrazioni, su una superficie inclinata di policarbonato, per indagare le conseguenze sullo scivolamento della sovrapposizione delle catene polimeriche in condizioni di Boger. Queste soluzioni sono caratterizzate infatti da un’elevata elasticità ma presentano al contempo una viscosità debolmente dipendente dal tasso di deformazione, grazie alla presenza del glicerolo. Tale proprietà consente, in linea di principio, di separare il contributo elastico dagli effetti viscosi non newtoniani del fluido. Vengono prese in esame anche soluzioni acquose di alcol polivinilico (PVA), successivamente gelificate con l’aggiunta di borace, al fine di indagare gli effetti della concatenazione dei polimeri sullo scivolamento. I dati ottenuti dalle misure di scivolamento, tuttavia, non hanno evidenziato particolari effetti dovuti all’elasticità delle catene polimeriche di PAA. Dal confronto della lunghezza delle gocce durante lo scivolamento a diverse inclinazioni, è invece emerso come il solvente presenti un allungamento maggiore rispetto alla soluzione contenente il polimero, e come questo diminuisca all'aumentare della quantità di PAA disciolta. La presenza del glicerolo in soluzione determina evidentemente una maggiore adesione della goccia alla superficie, mentre la presenza del polimero la contrasta favorendone lo scivolamento. Il tentativo svolto con le soluzioni di PVA e relativi gel, volto a studiare l'effetto della reticolazione delle catene polimeriche sullo scivolamento, ha purtroppo mostrato un'instabilità perfino superiore, a causa della forte riduzione dell'angolo di contatto dinamico posteriore. Come sviluppo futuro ci si potrà concentrare sugli effetti di bagnabilità delle superfici, sul cross-linking delle catene di PAA e sull'utilizzo di altri fluidi viscoelastici, come le cosiddette “micelle giganti” che presentano anche fasi di cristalli liquidi. In tal senso il presente elaborato costituisce dunque una base di partenza per lo studio di scivolamento in presenza di sovrapposizione e reticolazione di catene polimericheope

Protein sizing with Differential Dynamic Microscopy

Introduced more than fifty years ago, dynamic light scattering is routinely used to determine the size distribution of colloidal suspensions, as well as of macromolecules in solution, such as proteins, nucleic acids, and their complexes. More recently, differential dynamic microscopy has been proposed as a way to perform dynamic light scattering experiments with a microscope, with much less stringent constraints in terms of cleanliness of the optical surfaces, but a potentially lower sensitivity due to the use of camera-based detectors. In this work, we push bright-field differential dynamic microscopy beyond known limits and show it to be sufficiently sensitive to size small macromolecules in diluted solutions. By considering solutions of three different proteins (Bovine Serum Albumin, Lysozyme, and Pepsin), we accurately determine the diffusion coefficient and hydrodynamic radius of both single proteins and small protein aggregates down to concentrations of a few milligrams per milliliter. In addition, we present preliminary results showing unexplored potential for the determination of virial coefficients. Our results are in excellent agreement with the ones obtained in parallel with a state-of-the-art commercial dynamic light scattering setup, showing that differential dynamic microscopy represents a valuable alternative for rapid, label-free protein sizing with an optical microscope

Modulating brain integrative actions as a new perspective on pharmacological approaches to neuropsychiatric diseases

: A critical aspect of drug development in the therapy of neuropsychiatric diseases is the "Target Problem", that is, the selection of a proper target after not simply the etiopathological classification but rather the detection of the supposed structural and/or functional alterations in the brain networks. There are novel ways of approaching the development of drugs capable of overcoming or at least reducing the deficits without triggering deleterious side effects. For this purpose, a model of brain network organization is needed, and the main aspects of its integrative actions must also be established. Thus, to this aim we here propose an updated model of the brain as a hyper-network in which i) the penta-partite synapses are suggested as key nodes of the brain hyper-network and ii) interacting cell surface receptors appear as both decoders of signals arriving to the network and targets of central nervous system diseases. The integrative actions of the brain networks follow the "Russian Doll organization" including the micro (i.e., synaptic) and nano (i.e., molecular) levels. In this scenario, integrative actions result primarily from protein-protein interactions. Importantly, the macromolecular complexes arising from these interactions often have novel structural binding sites of allosteric nature. Taking G protein-coupled receptors (GPCRs) as potential targets, GPCRs heteromers offer a way to increase the selectivity of pharmacological treatments if proper allosteric drugs are designed. This assumption is founded on the possible selectivity of allosteric interventions on G protein-coupled receptors especially when organized as "Receptor Mosaics" at penta-partite synapse level

Warfarin, but not rivaroxaban, promotes the calcification of the aortic valve in ApoE-/- mice.

SummaryIntroductionVitamin K antagonists, such as warfarin, are known to promote arterial calcification through blockade of gamma‐carboxylation of Matrix‐Gla‐Protein. It is currently unknown whether other oral anticoagulants such as direct inhibitors of Factor Xa can have protective effects on the progression of aortic valve calcification.AimsTo compare the effect of warfarin and rivaroxaban on the progression of aortic valve calcification in atherosclerotic mice.Results42 ApoE−/− mice fed with Western‐type Diet (WTD) were randomized to treatment with warfarin (n = 14), rivaroxaban (n = 14) or control (n = 14) for 8 weeks. Histological analyses were performed to quantify the calcification of aortic valve leaflets and the development of atherosclerosis. The analyses showed a significant increase in valve calcification in mice treated with warfarin as compared to WTD alone (P = .025) or rivaroxaban (P = .005), whereas no significant differences were found between rivaroxaban and WTD (P = .35). Quantification of atherosclerosis and intimal calcification was performed on the innominate artery of the mice and no differences were found between the 3 treatments as far as atherogenesis and calcium deposition is concerned. In vitro experiments performed using bovine interstitial valve cells (VIC) showed that treatment with rivaroxaban did not prevent the osteogenic conversion of the cells but reduce the over‐expression of COX‐2 induced by inflammatory mediators.ConclusionWe showed that warfarin, but not rivaroxaban, could induce calcific valve degeneration in a mouse model of atherosclerosis. Both the treatments did not significantly affect the progression of atherosclerosis. Overall, these data suggest a safer profile of rivaroxaban on the risk of cardiovascular disease progression

Exosomes from astrocyte processes: Signaling to neurons

open13It is widely recognized that extracellular vesicles subserve non-classical signal transmission in the central nervous system. Here we assess if the astrocyte processes, that are recognized to play crucial roles in intercellular communication at the synapses and in neuron-astrocyte networks, could convey messages through extracellular vesicles. Our findings indicate, for the first time that freshly isolated astrocyte processes prepared from adult rat cerebral cortex, can indeed participate to signal transmission in central nervous system by releasing exosomes that by volume transmission might target near or longdistance sites. It is noteworthy that the exosomes released from the astrocyte processes proved ability to selectively target neurons. The astrocyte-derived exosomes were proven positive for neuroglobin, a protein functioning as neuroprotectant against cell insult; the possibility that exosomes might transfer neuroglobin to neurons would add a mechanism to the potential astrocytic neuroprotectant activity. Notably, the exosomes released from the processes of astrocytes maintained markers, which prove their parental astrocytic origin. This potentially allows the assessment of the cellular origin of exosomes that might be recovered from body fluids.openVenturini A.; Passalacqua M.; Pelassa S.; Pastorino F.; Tedesco M.; Cortese K.; Gagliani M.C.; Leo G.; Maura G.; Guidolin D.; Agnati L.F.; Marcoli M.; Cervetto C.Venturini, A.; Passalacqua, M.; Pelassa, S.; Pastorino, F.; Tedesco, M.; Cortese, K.; Gagliani, M. C.; Leo, G.; Maura, G.; Guidolin, D.; Agnati, L. F.; Marcoli, M.; Cervetto, C

Misure di scivolamento di gocce di gel polimerici su superfici chimicamente omogenee

Il presente lavoro di tesi si propone di studiare lo scivolamento di gocce di poliacrilammide (PAA) in una miscela di acqua e glicerolo a diverse concentrazioni, su una superficie inclinata di policarbonato, per indagare le conseguenze sullo scivolamento della sovrapposizione delle catene polimeriche in condizioni di Boger. Queste soluzioni sono caratterizzate infatti da un’elevata elasticità ma presentano al contempo una viscosità debolmente dipendente dal tasso di deformazione, grazie alla presenza del glicerolo. Tale proprietà consente, in linea di principio, di separare il contributo elastico dagli effetti viscosi non newtoniani del fluido. Vengono prese in esame anche soluzioni acquose di alcol polivinilico (PVA), successivamente gelificate con l’aggiunta di borace, al fine di indagare gli effetti della concatenazione dei polimeri sullo scivolamento. I dati ottenuti dalle misure di scivolamento, tuttavia, non hanno evidenziato particolari effetti dovuti all’elasticità delle catene polimeriche di PAA. Dal confronto della lunghezza delle gocce durante lo scivolamento a diverse inclinazioni, è invece emerso come il solvente presenti un allungamento maggiore rispetto alla soluzione contenente il polimero, e come questo diminuisca all'aumentare della quantità di PAA disciolta. La presenza del glicerolo in soluzione determina evidentemente una maggiore adesione della goccia alla superficie, mentre la presenza del polimero la contrasta favorendone lo scivolamento. Il tentativo svolto con le soluzioni di PVA e relativi gel, volto a studiare l'effetto della reticolazione delle catene polimeriche sullo scivolamento, ha purtroppo mostrato un'instabilità perfino superiore, a causa della forte riduzione dell'angolo di contatto dinamico posteriore. Come sviluppo futuro ci si potrà concentrare sugli effetti di bagnabilità delle superfici, sul cross-linking delle catene di PAA e sull'utilizzo di altri fluidi viscoelastici, come le cosiddette “micelle giganti” che presentano anche fasi di cristalli liquidi. In tal senso il presente elaborato costituisce dunque una base di partenza per lo studio di scivolamento in presenza di sovrapposizione e reticolazione di catene polimerich

Contrôle du vieillissement des mousses dans les milieux visco-élastiques

Foams are concentrated dispersions of gas bubbles in a continuous medium which arewidely encountered in many applications, from food industry to cosmetics, where theirliquid phase is often a fluid with complex rheology. Nevertheless, such systems are intrinsically unstable, as their structure can be altered over time by a competition of differentmechanisms, including pressure-driven gas diffusion between the bubbles. Even thoughthis coarsening process has been widely studied in aqueous foams, its dependence on themechanical properties of the liquid phase and its volume fraction still lacks a thorough understanding. In this thesis, we first experimentally probe how an increasing liquid fractioninfluences the coarsening process of aqueous bubble monolayers confined between two glass plates. The gradual decrease and eventual vanishing of the thin film area between adjacent bubbles results in a reduction of the global coarsening rate over time, which we compare with existing models. We then investigate the effect of a viscoelastic foam continuous phase on the coarsening process, by replacing the aqueous phase with concentrated oil-in-water emulsions. We show that an increase of the emulsion elasticity results in an heterogeneous bubble growth which deeply modifies the foam structure, with the appearance of unrelaxed bubble patterns. This leads to a delay in the shrinkage and disappearance of smaller bubbles which reduces the bubble growth rate. Further investigations on the coarsening dynamics in such systems show that the motion of the bubbles during coarsening is also reduced upon increase of emulsion elasticity. Finally, we show how aerated emulsions can be generated in a single step by simultaneously mixing the oil, gas and aqueous phases, ensuring a good scale separation between gas bubbles and oil drops. Moreover, we show how a standard light scattering technique such as laser diffraction granulometry can be used for a fast measure of the bubble size also in double dispersions of fluids having different refractive index. Our results on the phase separation of foamed emulsions provide new insights on their destabilising mechanism which can help controlling the stability of such complex systems for the design of new materials with atypical cellular morphology.Les mousses sont des dispersions concentrées de bulles de gaz dans un milieu continu,largement rencontrées dans de nombreuses applications, de l'industrie alimentaire à la cosmétique, où la phase liquide de la mousse est souvent un fluide à rhéologie complexe.Néanmoins, ces systèmes sont par nature instables: leur structure peut être modifiée aucours du temps par différents mécanismes, dont la diffusion de gaz entre les bulles due àleur différence de pression. Même si ce mûrissement a été largement étudié dans les mousses aqueuses, sa dépendance aux propriétés mécaniques de la phase liquide et sa fraction volumique manquent encore d'une compréhension approfondie. Dans cette thèse, nous étudions expérimentalement comment l'augmentation de la fraction liquide influence le mûrissement de monocouches de bulles aqueuses confinées entre deux plaques en verre. La diminution progressive et la disparition éventuelle des films minces entre les bulles entraîne une réduction du taux de mûrissement au cours du temps, que nous comparons avec les modèles existants. Nous étudions ensuite l'effet d'une phase continue viscoélastique sur le mûrissement des mousses, en remplaçant la phase aqueuse par des émulsions concentrées d'huile dans l'eau. Nous montrons que l'augmentation de l'élasticité de l'émulsion se traduit par une hétérogénéité de croissance des bulles qui modifie profondément la structure de lamousse, avec l'apparition de motifs de bulles non relaxés. Cela entraîne un retard dans lerétrécissement et la disparition des petites bulles, ce qui réduit le taux de croissance desbulles. D'autres résultats sur la dynamique de mûrissement dans ces mousses d'émulsions montrent que le mouvement des bulles pendant le grossissement est également réduit lors de l'augmentation de l'élasticité de l'émulsion. Enfin, nous montrons comment des émulsionsaérées peuvent être générées en une seule étape en mélangeant simultanément l'huile, l'airet la phase aqueuse, assurant une bonne séparation d'échelle entre les bulles de gaz et lesgouttes d'huile. En outre, nous montrons comment une technique standard de diffusion dela lumière telle que la granulométrie par diffraction laser peut être utilisée pour une mesurerapide de la taille des bulles dans des doubles dispersions de fluides ayant un indice deréfraction différent. Nos résultats sur la séparation de phase des mousses d'émulsions fournissent de nouvelles informations sur leur mécanisme de déstabilisation qui peuvent aider à contrôler la stabilité de ces systèmes complexes pour la création de nouveaux matériaux à morphologie cellulaire atypique

Contrôle du vieillissement des mousses dans les milieux visco-élastiques

Les mousses sont des dispersions concentrées de bulles de gaz dans un milieu continu,largement rencontrées dans de nombreuses applications, de l'industrie alimentaire à la cosmétique, où la phase liquide de la mousse est souvent un fluide à rhéologie complexe.Néanmoins, ces systèmes sont par nature instables: leur structure peut être modifiée aucours du temps par différents mécanismes, dont la diffusion de gaz entre les bulles due àleur différence de pression. Même si ce mûrissement a été largement étudié dans les mousses aqueuses, sa dépendance aux propriétés mécaniques de la phase liquide et sa fraction volumique manquent encore d'une compréhension approfondie. Dans cette thèse, nous étudions expérimentalement comment l'augmentation de la fraction liquide influence le mûrissement de monocouches de bulles aqueuses confinées entre deux plaques en verre. La diminution progressive et la disparition éventuelle des films minces entre les bulles entraîne une réduction du taux de mûrissement au cours du temps, que nous comparons avec les modèles existants. Nous étudions ensuite l'effet d'une phase continue viscoélastique sur le mûrissement des mousses, en remplaçant la phase aqueuse par des émulsions concentrées d'huile dans l'eau. Nous montrons que l'augmentation de l'élasticité de l'émulsion se traduit par une hétérogénéité de croissance des bulles qui modifie profondément la structure de lamousse, avec l'apparition de motifs de bulles non relaxés. Cela entraîne un retard dans lerétrécissement et la disparition des petites bulles, ce qui réduit le taux de croissance desbulles. D'autres résultats sur la dynamique de mûrissement dans ces mousses d'émulsions montrent que le mouvement des bulles pendant le grossissement est également réduit lors de l'augmentation de l'élasticité de l'émulsion. Enfin, nous montrons comment des émulsionsaérées peuvent être générées en une seule étape en mélangeant simultanément l'huile, l'airet la phase aqueuse, assurant une bonne séparation d'échelle entre les bulles de gaz et lesgouttes d'huile. En outre, nous montrons comment une technique standard de diffusion dela lumière telle que la granulométrie par diffraction laser peut être utilisée pour une mesurerapide de la taille des bulles dans des doubles dispersions de fluides ayant un indice deréfraction différent. Nos résultats sur la séparation de phase des mousses d'émulsions fournissent de nouvelles informations sur leur mécanisme de déstabilisation qui peuvent aider à contrôler la stabilité de ces systèmes complexes pour la création de nouveaux matériaux à morphologie cellulaire atypique.Foams are concentrated dispersions of gas bubbles in a continuous medium which arewidely encountered in many applications, from food industry to cosmetics, where theirliquid phase is often a fluid with complex rheology. Nevertheless, such systems are intrinsically unstable, as their structure can be altered over time by a competition of differentmechanisms, including pressure-driven gas diffusion between the bubbles. Even thoughthis coarsening process has been widely studied in aqueous foams, its dependence on themechanical properties of the liquid phase and its volume fraction still lacks a thorough understanding. In this thesis, we first experimentally probe how an increasing liquid fractioninfluences the coarsening process of aqueous bubble monolayers confined between two glass plates. The gradual decrease and eventual vanishing of the thin film area between adjacent bubbles results in a reduction of the global coarsening rate over time, which we compare with existing models. We then investigate the effect of a viscoelastic foam continuous phase on the coarsening process, by replacing the aqueous phase with concentrated oil-in-water emulsions. We show that an increase of the emulsion elasticity results in an heterogeneous bubble growth which deeply modifies the foam structure, with the appearance of unrelaxed bubble patterns. This leads to a delay in the shrinkage and disappearance of smaller bubbles which reduces the bubble growth rate. Further investigations on the coarsening dynamics in such systems show that the motion of the bubbles during coarsening is also reduced upon increase of emulsion elasticity. Finally, we show how aerated emulsions can be generated in a single step by simultaneously mixing the oil, gas and aqueous phases, ensuring a good scale separation between gas bubbles and oil drops. Moreover, we show how a standard light scattering technique such as laser diffraction granulometry can be used for a fast measure of the bubble size also in double dispersions of fluids having different refractive index. Our results on the phase separation of foamed emulsions provide new insights on their destabilising mechanism which can help controlling the stability of such complex systems for the design of new materials with atypical cellular morphology

Controlling foam ageing in viscoelastic media

Foams can be defined as dispersions of gas bubbles in a continuous medium. They exhibit a typical cellular structure, where the gas bubbles are tightly packed together, so that the liquid phase is spread in a network of thin films and channels between bubbles. Thanks to their lightness and their peculiar mechanical properties, foams are suitable for several industrial applications. Foams are intrinsically unstable. During their life, they can undergo three different mechanisms of destabilisation: drainage, coalescence and coarsening. These processes alter the foam structure and can be a strong limitation in industrial processes. The desired longevity of a foam clearly depends on the specific applications, which call for a thorough understanding of foam stabilisation. The purpose of the present thesis is to investigate how the mechanical properties of the continuous phase impact on liquid foam coarsening, in conditions where drainage and coalescence can both be neglected. In order to do that, we use emulsions as the liquid phase, because of their viscoelasticity. The study of foams requires the use of non-invasive methods. Thus, foamed emulsions are studied by employing diffusing-wave spectroscopy and imaging, to get information about the evolution of the mean bubble size and the gas permeability of the liquid films between bubbles. What we observed is that the emulsion elasticity does influence the foam coarsening either in two or in three dimensions, showing a peculiar behaviour that lays the groundwork for further investigations