Nanoscale dielectric mapping of biomembranes with in-liquid Scanning Dielectric Microscopy
- Autores: Martina di Muzio
- Directores de la Tesis: Gabriel Gomila Lluch (dir. tes.)
- Lectura: En la Universitat de Barcelona ( España ) en 2021
- Idioma: inglés
- Tribunal Calificador de la Tesis: Maria Garcia Parajo (presid.), Lorena Redondo Morata (secret.), Pierre-emmanuelle Milhiet (voc.)
- Materias:
- Enlaces
- Tesis en acceso abierto en: TDX
- Resumen
The structure and physicochemical properties of biomembranes are fundamental for the functioning of cells, and many pathologies have been associated with their alteration (cancer, neurodegenerations, obesity, etc.). For this reason, biomembranes have been the subject of intensive research. Yet, there is still limited knowledge of the physical properties of biomembranes showing a heterogeneous structure at the nanoscale, which are actually those naturally present in cells and that determine many of the phenomena occurring through them at the molecular level. Due to their prominent role in Electrophysiology, electrical properties are among the more relevant physical properties of biomembranes. Most often, attention is paid to biomembranes' conduction properties, and the role played in them by ionic channels. However, biomembranes' dielectric properties are also of central interest in bioelectric phenomena, and a powerful reporter of membranes' composition, which can be exploited to develop label-free mapping methods.
This work of thesis takes advantage of the latest developments of in-liquid Scanning Dielectric Microscospy (SDM) to characterize the dielectric properties of heterogeneous model and natural purified membranes systems in liquid. In this framework, new knowledge has been gained about imaging in liquid conditions with SDM, e.g. about the prominent electrostatic finite size effect and different models have been tested and optimized for the analysis of the measurements. First, I focused on characterizing mono- and bicomponent planar supported bilayer lipid mixtures containing cholesterol, providing a first proof-of-concept of the label-free mapping capabilities of the technique in liquid media, extending earlier work done in air on nanoparticles. Afterwards, we extended the methods to deal with more complex biomembrane 3D structures, such as liposomes. Liposomes with few hundred nanometers in height have been successfully imaged by in-liquid SDM. Once again, the dielectric properties of the liposomes’ membrane were precisely extracted, this time in a more natural configuration of the biomembrane.
This study also highlighted the technique’s sub-surface capabilities in the liquid environment, demonstrated earlier only in air measurements, and enabled to obtain in a label-free way the lamellarity of liposomes, a crucial parameter in liposomes technology. Finally, the thesis also considers the dielectric characterization of natural purified membranes in liquid environment (explicitly the purple membrane), and analyzed the complexities found when dealing with natural samples. The present thesis laid the ground for elucidating the structure and dielectric properties of more complex membranes systems, including living cells.
