Browsing by Author "Luotonen, Otso"

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Host-guest Chemistry for Restricting Bacterial Quorum Sensing
(2025-01-30) Rantanen, Rasmus
School of Chemical Engineering | Master's thesis
In search of potential solutions to antimicrobial resistance (AMR), supramolecular host molecules have gained significant interest due to their characteristic ability to encapsulate various types of guest molecules. Supramolecular host molecules can be harnessed to restrict bacterial quorum sensing (QS) via encapsulation of N-acyl-homoserine lactones (HSLs). HSLs are the main signaling molecules used by Gram-negative bacteria to control a multitude of processes involved in bacterial virulence. In this work, a systematic study on the association constants between modified and native β-cyclodextrins (β-CDs) and HSLs is conducted. Specifically, this thesis investigates the impact of N-acyl chain length, substitution at C3-site of the N-acyl chain and modification of CD structure on the binding affinity. The studied HSL molecules include C4-HSL, C8-HSL and C12-HSL and their oxo- and hydroxy-substituted counterparts. The cyclodextrins used in this work contain native, amino-modified, trimethyl-ammonium-modified, lysine-modified, dimethyl-modified and trimethyl-modified β-CDs. The association constants are derived via fluorescence-based indicator displacement assays (IDAs) using 2-anilinonaphthalene-6-sulfonic acid (2,6-ANS) as fluorescent probe. HSL binding improves as the N-acyl chain length increases from a four-carbon chain to twelve-carbon chain across the studied CDs. On the other hand, the studied CD modifications do not improve the affinity to HSLs. In fact, the highest association constants are recorded for native β-CD across all the studied HSLs. Finally, the substitutions at C3-site of N-acyl chain yields mixed results. Substitution in C12-HSL increases the affinity, whereas substitution in C8-HSL decreases the affinity to the studied CDs.
Performance of bio-colloids as structural adhesives: effect of nanoscaled morphology and polymeric additives
(2021-10-19) Luotonen, Otso
Kemian tekniikan korkeakoulu | Master's thesis
Adhesives are an increasingly used material class, their application having distinct advantages over other joining methods. Current research is characterized by seeking more sustainable and specialised solutions to retain competitiveness. Novel approaches such as confined evaporation-induced self-assembly (C-EISA) of biopolymers could lead to solutions to these challenges. In this thesis, C-EISA bonds were produced with a range of biopolymers and bio-colloids (cellulose nanofibrils (CNF), proteins and cellulose-derivative polysaccharides), both alone and combined with cellulose nanocrystals (CNC). Formed bonds were studied using bright and polarized light microscopy, as well as scanning electron microscopy (SEM). Mechanical bond properties were tested under in-plane (lap shear) and out-of-plane loads. In addition to adhesive properties, self-assembly behaviour of the different formulations was analysed. Distinct assembly fingerprints were observed for different compounds, and combinations of CNCs and biopolymers produced hybrid assemblies of their fingerprints. Major variables affecting self-assembly include gelation behaviour, interfacial interactions, and inter-macromolecule interactions. Adhesion properties varied considerably, with certain formulations showing performance comparable to commercial formulations with the same dry matter content. Overall, this work highlights new routes of study for aqueous evaporative self-assembly and the various related applications, in particular adhesive purposes.