Dokument: Synthesis and Characterization of Amphiphilic Precision Glycomacromolecules

Titel:	Synthesis and Characterization of Amphiphilic Precision Glycomacromolecules
Weiterer Titel:	Synthese und Charakterisierung von amphiphilen Präzisionsglykomakromolekülen
URL für Lesezeichen:	https://docserv.uni-duesseldorf.de/servlets/DocumentServlet?id=61458
URN (NBN):	urn:nbn:de:hbz:061-20221222-090905-0
Kollektion:	Dissertationen
Sprache:	Englisch
Dokumententyp:	Wissenschaftliche Abschlussarbeiten » Dissertation
Medientyp:	Text
Autor:	Banger, Alexander [Autor]
Dateien:	[Dateien anzeigen] Adobe PDF [Details] 9,48 MB in einer Datei [ZIP-Datei erzeugen] Dateien vom 11.12.2022 / geändert 11.12.2022
Beitragende:	Prof. Dr. Hartmann, Laura [Betreuer/Doktorvater] Prof. Dr. Karg, Matthias [Gutachter]
Dewey Dezimal-Klassifikation:	500 Naturwissenschaften und Mathematik » 540 Chemie
Beschreibungen:	- Carbohydrates are ubiquitous, nearly every cell of eukaryotes and prokaryotes is covered in a layer of carbohydrates the so called “glycocalyx”. The counterpart to the glycocalyx are carbohydrate binding proteins, for example the class of lectins. Interactions of lectins with various carbohydrates have been identified to play a key role in many biological processes like cell communication and signal transduction processes. Additionally, being one of the first point of contacts, carbohydrates and lectins are associated with pathogen adhesion to host cells but have also been associated with various developmental stages of cancer. A single carbohydrate-lectin binding is usually weak, hence Nature presents carbohydrates in a multivalent fashion combining multiple weak binding events to create stronger binding. Using this concept of multivalency, significant advances towards so-called glycomimetics have been made. Recently, Hartmann and co-workers have described the usage of a stepwise assembly process of tailormade monomer building blocks onto a solid support obtaining sequence defined oligo(amido)amines scaffolds for the multivalent presentation of different carbohydrates. Such precision glycooligomers are considered a new class of glycomimetics as they now offer high structural control and variability, more closely mimicking natural multivalent carbohydrate constructs such as oligosaccharides or glycoproteins and glycolipids. In this thesis, precision glycooligomers are extended by making them amphiphilic and thereby utilizing self-assembly as bottom approach for the synthesis of larger multivalent systems. Therefore, the synthesis of amphiphilic precision glycomacromolecules (APGs) is introduced, including the synthesis of novel building blocks, establishing design principles for APGs along with optimized synthetic protocols. In the second part, APG self-assembly and binding behavior is investigated and in the third part this approach is combined with AIE fluorophores for potential read-out of binding. Finally, alternative multivalent scaffold, active ester polymers are explored for combinations with precision glycooligomers. In the first part of this thesis, the APG synthesis was successfully established and applied to derive a series of APGs for systematic structure-property correlation studies. As part of the synthesis, two novel hydrophobic building block suited for SPPoS were developed. Starting from hexamethylenediamine a synthesis was established, which allowed for the preparation of the alkyl spacing building block hexamethylenediamine coupled with succinic anhydride (HDS) and the alkene bearing hexamethylenediamine coupled with maleic anhydride (HDM). These hydrophobic building blocks allowed to prolong the hydrophobic part of the APG and in the case of HDM also to introduce an alkene species, which was later used for micellar core-crosslinking. Here, three different strategies for micellar core-crosslinking were investigated utilizing the new HDM building block. Additionally, fatty acids as terminal hydrophobic moieties were introduced to solid phase tool box. C10, C12 and C15 fatty acids were attachable under standard coupling conditions to the APGs and were later shown to be sufficient to induce self-assembly in water. Building on to the first part, a series of 8 APGs was systematically analyzed regarding their self-assembly characteristics by the means of CMC, micellar size and shape. The CMC can be readily tuned by the length of the terminal fatty acid with CMCs ranging from micromolar to millimolar. Subsequently, the shape and size of the micelle were assessed using DLS, AFM and TEM. Here it was shown, that depending on the number of hydrogen bonds available in the APG backbone, spherical as well as rodlike micelles were accessible which is in agreement with comparable structures based on peptide amphiphiles. Furthermore, crosslinking of micelles was achieved using the novel HDM building block. Crosslinked micelles were not only more stable during AFM and TEM analysis, but they could also withstand dilution below CMC and solvent changes from water to ethanol. Lastly, APGs were tested regarding their potential as inhibitors of bacterial adhesion of FimH bearing E. coli. Here, non-crosslinked APGs showed a better inhibition as crosslinked micelles. Surprisingly, for crosslinked micelles a cooperativity factor of 2 was determined compared to the cooperativity factor of close to 1 for the non-crosslinked micelles suggesting that despite a lower overall binding affinity the crosslinking improved the probability of a secondary binding event once the first binding is established. In the third part of this thesis and based on preliminary studies by Peter Pasch, aggregation induced emission (AIE) dyes were integrated into the tail end of the APGs and their usage as clustering sensors was evaluated. For tetraphenylethylene containing APGs rod-like micelles were observed, whereas for carboxylated aromatic thioether luminophore containing APGs spherical micelles were detected. By combining AIE-APGs and commercial non-AIE, non-carbohydrate amphiphiles as well as non-AIE-APGs, so-called mixed micelles (micelles that are formed out of at least two different surfactants) experiments were conducted showing that the overall fluorescence of AIE-APG micelles can be reduced by adding a non-AIE containing APG. Subsequently, binding characteristics of these mixed micelle systems were investigated. As binding targets, the two tetrameric lectins Con A and GNA as well as the dimeric lectin LCA were employed. Titration of these lectins to the mixed micelles lead to a fluorescence increase but with a more pronounced effect for the tetramers. This experiment showcased the future potential of utilizing mix micelles as sensors for clustering events. In the last and fourth part of this thesis, polymers based on active esters as GAG mimetics for incorporation into hydrogels were developed. Therefore, a novel RAFT agent was synthesized bearing an Fmoc-protected terminal amine group allowing for later hydrogel integration. Polymerization with this RAFT agent showed good results in terms of dispersity but failed to reach polymer weights above 8000 g/mol. Furthermore, functionalization of the active ester polymer was readily accomplished and confirmed by 1H-NMR, 19F-NMR and H2O-GPC. Overall, the new concept as well as the synthesis of amphiphilic precision glycomacromolecules was established, thereby extending the field of peptide amphiphiles and other amide based amphiphiles. The approach allows for great synthetic flexibility due to the usage of tailormade building blocks, as demonstrated by the introduction of AIE units or the core-crosslinking of micelles. Additionally, as shown by initial binding experiments, APGs have great potential for various applications e.g., adhesion inhibitors or as multivalent binding partners in general. Furthermore, first insights regarding membrane clustering events were obtained using AIE-APGs.
Lizenz:	Dieses Werk ist lizenziert unter einer Creative Commons Namensnennung 4.0 International Lizenz
Fachbereich / Einrichtung:	Mathematisch- Naturwissenschaftliche Fakultät » WE Chemie » Organische Chemie und Makromolekulare Chemie
Dokument erstellt am:	22.12.2022
Dateien geändert am:	22.12.2022
Promotionsantrag am:	28.06.2022
Datum der Promotion:	22.11.2022