Dendrimers are a class of highly structured three-dimensional macromolecules characterized by a well-defined periodically branched structure, high monodispersity and tunable size and shape. Among them amphiphilic dendrimers, in which two moieties of different hydrophilicity are covalently linked, can self-assemble in aqueous media generating many different types of aggregates whose morphology strictly depends on the balance between hydrophilic and hydrophobic portions. This allows to control their molecular conformation, the aggregation behavior both in bulk and in solution, and thus the final shape of the aggregate formed. The control of these parameters is important for the emergence of specific functions. A powerful tool for tuning the self-assembly behavior of dendritic amphiphiles and increasing their colloidal stability, also in biological media, is the introduction of linear or branched fluoroalkyl groups in their molecular structure. This enhances their tendency to segregate and influences their molecular supramolecular organization. In this regard, the search for more sustainable fluorinated materials focused attention on shorter chains perfluorocarbons (PFCs). However, simply cutting down chain length does not lead to satisfactory results in balancing environmental impact and performance. Recently, multibranched super-fluorinated derivatives obtained high attention since they combine good biocompatibility with performances assimilable to classical PFCs. Moreover, the presence of a high number of equivalent fluorine atoms in their structure renders them excellent 19F-Magnetic Resonance Imaging (19F-MRI) probes. We decided to exploit the advantages of branched fluorinated chains to generate new polyfluorinated amphiphilic dendrimers suitable for gene delivery and traceable by 19F-MRI, thus obtaining new theranostic systems. Firstly, this thesis gives an overview on the literature with particular attention to amphiphiles, especially dendritic amphiphiles. Moreover, an introduction on 19F-MRI probes and gene delivery vectors is also reported relative to the proposed application of the reported derivatives. Subsequently, synthesis and characterization of new polyfluorinated dendritic amphiphiles of different generations are discussed reporting on their properties both in bulk and in solution. We observed that the self-assembly of these molecules is strictly dependent on their generation, and that we are able to tune the aggregate shape with consequent change in the magnetic relaxivities of the fluorine nuclei. Gene delivery has become a powerful tool to treat diseases. The need to protect and deliver nucleic acids into cells requires the use of biocompatible and efficient vectors. Among those reported in literature, fluorinated dendrimers attracted high interest since they were shown to improve vector stability and enhance gene endosomal escape. Therefore, the chemical structure of the polyfluorinated dendritic amphiphiles was modified for promoting the interaction with nucleic acids. It has indeed been reported that fluorination can stabilize the formation of complexes with genes for similar compounds and facilitate their intracellular release. In this regard, the synthetic approach adopted here and the chemical characterization of the obtained derivative are discussed. Furthermore, self-assembly behavior in aqueous media of the obtained derivative is described with particular attention to the characterization of shape and stability of its aggregates. Finally, gene complexation ability and transfection efficiencies of the new dendritic vector are presented. In the last part of this thesis, here referred as pullout, the results obtained from another project, in which the effects of fluorination on the self-assembly of small molecules are discussed. Here the tendency of fluorinated moieties to microsegregate is combined with the high directional effect driven by halogen bond to tune the liquid crystal phase and thermal stability of new ionic liquid crystalline materials. In this final section the syntheses, crystal structures, and thermal properties of these new ionic liquid crystals are treated.
I dendrimeri sono una classe di macromolecole altamente strutturate caratterizzate da una struttura ramificata ben definita, elevata monodispersità e dimensione e forma modulabili. Tra questi spiccano i dendrimeri anfifilici, in cui due porzioni di differente idrofilicità sono covalentemente legate, che possono auto assemblarsi in mezzi acquosi generando aggregati di differente tipologia la cui morfologia dipende strettamente dal bilanciamento tra porzione idrofilica e idrofobica. Ciò consente di controllarne la conformazione molecolare, l’aggregazione allo stato solido e in soluzione e, di conseguenza, la forma degli aggregati. La modulazione di questi parametri è fondamentale per il controllo delle funzioni finali. Uno strumento potente per regolare il self-assembly di anfifili dendrimerici e aumentarne la stabilità colloidale, anche in ambiente biologico, è l’inserimento di gruppi fluoroalchilici lineari o ramificati nella struttura molecolare. Ciò ne aumenta la tendenza a segregare e ne influenza l’organizzazione molecolare e supramolecolare. A tal proposito la necessità di trovare materiali fluorurati più sostenibili ha portato allo sviluppo di perfluorocarburi (PFC) a catena più corta. Tuttavia, la semplice riduzione della lunghezza di catena non è sufficiente a bilanciare impatto ambientale e performances in modo soddisfacente. Di recente i derivati ramificati super-fluorurati hanno ricevuto grande attenzione poiché combinano una buona biocompatibilità con proprietà simili ai classici PFC. Inoltre, la presenza nella loro struttura di un alto numero di fluori equivalenti li rende eccellenti probe per la Risonanza Magnetica al fluoro-19 (19F-MRI). Sfruttando i vantaggi delle catene ramificate fluorurate, si è deciso di produrre nuovi anfifili dendrimerici polifluorurati applicabili per il trasporto genico e tracciabili mediante 19F-MRI, ottenendo così sistemi teranostici. Questo lavoro di tesi si apre con uno sguardo sulla letteratura, con particolare attenzione agli anfifili, specialmente quelli dendrimerici. Inoltre, vengono introdotti le sonde attive alla 19F-MRI e i vettori genici presenti ad oggi in relazione alle applicazioni proposte per i derivati mostrati in questa tesi. Successivamente, viene mostrata la sintesi e caratterizzazione strutturale dei nuovi anfifili dendrimerici polifluorurati di diversa generazione con particolare attenzione alle proprietà osservate sia in bulk che in soluzione. Si è notato che il self-assembly di queste molecole dipende strettamente dalla generazione e che è possibile modulare la forma dell’aggregato influenzando di conseguenza le proprietà magnetiche dei nuclei di fluoro. Il trasporto genico è diventato uno strumento potente per trattare molte malattie, ma la necessità di proteggere e trasportare gli acidi nucleici nelle cellule richiede l’uso di vettori efficienti e biocompatibili. Tra quelli presenti in letteratura, i dendrimeri fluorurati sono di particolare interesse per la loro tendenza a formare vettori genici più stabili e a sfuggire alla degradazione endosomiale. Di conseguenza si è deciso di modificare chimicamente la struttura degli anfifili dendrimerici polifluorurati per favorirne l’interazione con gli acidi nucleici. Infatti, è stato dimostrato che la fluorurazione induce una maggiore stabilità nei complessi coi geni e ne facilita il rilascio intracellulare. Quindi vengono mostrati l’approccio sintetico adottato per la produzione del derivato e la sua caratterizzazione chimica. Inoltre, ne viene descritto il self-assembly in mezzo acquoso con particolare attenzione alla forma e stabilità degli aggregati. Infine, vengono mostrate le abilità di complessazione genica e le efficienze di trasfezione del nuovo vettore dendrimerico. Nell’ultima parte di questa tesi, qui riferita come inserto, vengono mostrati i risultati ottenuti in un altro progetto in cui si è studiato l’effetto della fluorurazione sul self-assembly di piccole molecole. Qui la tendenza delle catene fluorurate a microsegregare viene combinata con l’alta direzionalità data dal legame ad alogeno per modulare le proprietà termiche e le fasi liquido cristalline di nuovi liquidi ionici cristallini. Vengono quindi mostrate la sintesi, le strutture cristalline e le proprietà termiche di questi nuovi cristalli liquidi ionici.
Dendritic amphiphiles for 19F-MRI and gene delivery
ROSATI, MARTA
2020/2021
Abstract
Dendrimers are a class of highly structured three-dimensional macromolecules characterized by a well-defined periodically branched structure, high monodispersity and tunable size and shape. Among them amphiphilic dendrimers, in which two moieties of different hydrophilicity are covalently linked, can self-assemble in aqueous media generating many different types of aggregates whose morphology strictly depends on the balance between hydrophilic and hydrophobic portions. This allows to control their molecular conformation, the aggregation behavior both in bulk and in solution, and thus the final shape of the aggregate formed. The control of these parameters is important for the emergence of specific functions. A powerful tool for tuning the self-assembly behavior of dendritic amphiphiles and increasing their colloidal stability, also in biological media, is the introduction of linear or branched fluoroalkyl groups in their molecular structure. This enhances their tendency to segregate and influences their molecular supramolecular organization. In this regard, the search for more sustainable fluorinated materials focused attention on shorter chains perfluorocarbons (PFCs). However, simply cutting down chain length does not lead to satisfactory results in balancing environmental impact and performance. Recently, multibranched super-fluorinated derivatives obtained high attention since they combine good biocompatibility with performances assimilable to classical PFCs. Moreover, the presence of a high number of equivalent fluorine atoms in their structure renders them excellent 19F-Magnetic Resonance Imaging (19F-MRI) probes. We decided to exploit the advantages of branched fluorinated chains to generate new polyfluorinated amphiphilic dendrimers suitable for gene delivery and traceable by 19F-MRI, thus obtaining new theranostic systems. Firstly, this thesis gives an overview on the literature with particular attention to amphiphiles, especially dendritic amphiphiles. Moreover, an introduction on 19F-MRI probes and gene delivery vectors is also reported relative to the proposed application of the reported derivatives. Subsequently, synthesis and characterization of new polyfluorinated dendritic amphiphiles of different generations are discussed reporting on their properties both in bulk and in solution. We observed that the self-assembly of these molecules is strictly dependent on their generation, and that we are able to tune the aggregate shape with consequent change in the magnetic relaxivities of the fluorine nuclei. Gene delivery has become a powerful tool to treat diseases. The need to protect and deliver nucleic acids into cells requires the use of biocompatible and efficient vectors. Among those reported in literature, fluorinated dendrimers attracted high interest since they were shown to improve vector stability and enhance gene endosomal escape. Therefore, the chemical structure of the polyfluorinated dendritic amphiphiles was modified for promoting the interaction with nucleic acids. It has indeed been reported that fluorination can stabilize the formation of complexes with genes for similar compounds and facilitate their intracellular release. In this regard, the synthetic approach adopted here and the chemical characterization of the obtained derivative are discussed. Furthermore, self-assembly behavior in aqueous media of the obtained derivative is described with particular attention to the characterization of shape and stability of its aggregates. Finally, gene complexation ability and transfection efficiencies of the new dendritic vector are presented. In the last part of this thesis, here referred as pullout, the results obtained from another project, in which the effects of fluorination on the self-assembly of small molecules are discussed. Here the tendency of fluorinated moieties to microsegregate is combined with the high directional effect driven by halogen bond to tune the liquid crystal phase and thermal stability of new ionic liquid crystalline materials. In this final section the syntheses, crystal structures, and thermal properties of these new ionic liquid crystals are treated.| File | Dimensione | Formato | |
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Dendritic amphiphiles for 19F-MRI and gene delivery_Marta Rosati.pdf
Open Access dal 11/10/2022
Descrizione: PhD Thesis
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7.26 MB
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https://hdl.handle.net/10589/179362