Supported Lipid Membranes and Their Use for the Characterization of Biological Nanoparticles
Doktorsavhandling, 2020

Biological nanoparticles (BNPs) are nano-sized lipid vesicles of biological origin, which are involved in multiple biological processes. BNP characterization techniques are critical for improving the understanding of how these particles contribute to cellular communication, viral infections and drug-delivery applications. However, due to their small size (between 50 and 200 nm in diameter) and molecular heterogeneity, quantitative characterization of their physical, chemical and biological properties is demanding, especially since their large structural and compositional heterogeneity calls for methods with single nanoparticle resolution. To address this challenge, work in this thesis has been focused on investigating and using supported lipid bilayers (SLBs) and their two-dimensional fluidity as a platform for nanoparticle characterization.

To investigate SLBs, we combined confocal microscopy with microfluidics to identify the mechanisms by which lipid vesicles are spontaneously converted into various types of planar membranes on a multitude of surfaces (Paper I) and found that most of the studied materials can support lipid film formation. In the context of SLB formation, specific focus was put on using total internal reflection fluorescence (TIRF) microscopy to monitor the kinetics of vesicle adsorption, rupture and spreading of individual SLB patches on glass (Paper II), revealing that the SLB formation process was driven by the autocatalytic growth and merger of multiple small SLB patches at appreciably high vesicle coverage. TIRF was also successfully employed to monitor lipid-enveloped drug permeation through an SLB formed on a mesoporous silica thin film (Paper III). The insights gained from investigating SLBs was also used for in depth characterization of BNPs using the surface-based flow-nanometry method, allowing for independent determination of size and fluorescence emission of individual BNPs tethered to a laterally fluid SLB formed on the floor of a microfluidic channel. This way we could demonstrate that the fluorescence emission from lipophilic dyes depends in a non-trivial way on nanoparticle size, and varies significantly between the different types of BNPs (Paper IV). The flow-nanometry concept was also used to elucidate the effect of vesicle size on their diffusivity on the SLB in the limit of few tethers (Paper V).

The insights gained in this thesis work on lipid self-assembly at different surfaces and the possibility to use SLBs on silica for in-depth characterization of BNPs demonstrate this as a promising approach in the field of single nanoparticle analytics, which in future work will be possible to extend into a novel means to probe interactions between BNPs and cell-membrane mimics representing a near-native situation.


size determination

fluorescence microscopy

lipophilic dyes

supported lipid bilayer


Kollektorn, MC2, Kemivägen 9, Chalmers
Opponent: Jonas Tegenfeldt, Lund University, Sweden


Silver Jõemetsa

Chalmers, Fysik, Biologisk fysik

Molecular Lipid Films on Microengineering Materials

Langmuir,; Vol. 35(2019)p. 10286-10298

Artikel i vetenskaplig tidskrift

Spatiotemporal Kinetics of Supported Lipid Bilayer Formation on Glass via Vesicle Adsorption and Rupture

Journal of Physical Chemistry Letters,; Vol. 9(2018)p. 5143-5149

Artikel i vetenskaplig tidskrift

TIRF Microscopy-Based Monitoring of Drug Permeation Across a Lipid Membrane Supported on Mesoporous Silica

Angewandte Chemie - International Edition,; Vol. 60(2021)p. 2069-2073

Artikel i vetenskaplig tidskrift

Silver Jõemetsa, Erik Olsén, Adrián González Rodríguez, Paul Joyce, and Fredrik Höök Effects of Vesicle Size on Their Diffusivity when Linked to a Supported Lipid Bilayer

Many diseases threaten our well-being, including cancer, viral infections and neurodegenerative diseases. These diseases are often debilitating, having both societal and personal cost, and can ultimately lead to significant suffering and premature death. Cells are the building blocks of all life forms on earth and are therefore at the epicenter of all processes that maintain or threaten the health of an individual. Each cell is equipped with a biological membrane which contains its processes and protects it from outside influences. Furthermore, the membrane also contains various small molecular channels and “hooks” which enable communication with its surrounding environment or other cells. Millions of molecules are responsible for the communication with the nearest neighbors, and this complexity is a prerequisite for life; however, it can also be exploited by bacteria and viruses to introduce disease-causing material into the cells. For example, viruses, which are often also enclosed by a membrane, have evolved to hijack these processes for their own gain by hooking themselves to the cell membrane, transferring their own genetic information into cells to turn them into virus factories. Comparable to viruses, other similarly sized biological particles, about 1000-times smaller than the diameter of a human hair, have also been observed to transfer genetic information between cells, but rather than causing disease, they fulfill key biological functions. These particles can be found in all biological fluids, including blood, urine and saliva. It is clear from these exemplary mechanisms that they are a highly efficient way of affecting target cells and as such, there is a need to study these small particles to understand their complex interactions with cellular membranes. Furthermore, aided by an understanding of these interactions, new drugs targets could be identified and addressed, to take advantage of these particles to cure diseased cells or even destroy cancer cells. Finally, yet importantly, due to their presence in many bodily fluids, the hope for early detection of slow progressing diseases, rests on these particles.

In this work, I have investigated these small particles and their interactions with simplified cell membrane models. Specifically, I have studied how these model membranes react with common materials used in implants and as drug-carriers, but also how the membranes interacted with relevant drugs themselves. It became apparent, that the model membrane system can aid the development and testing of future more advanced means of drug-delivery. Secondly, I studied small virus-like particles to help characterize their size and membrane properties for further usage in diagnostics and drug discovery applications. This was all made possible by advanced microscopy techniques and small microfluidic devices.

It is my hope that the insights gained from this research will bring us one step closer to discovering the early stages of disease progression and to better address debilitating diseases through more efficient delivery of new drugs.


Annan fysik






Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 4702



Kollektorn, MC2, Kemivägen 9, Chalmers

Opponent: Jonas Tegenfeldt, Lund University, Sweden

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