Increased accumulation of misfolded proteins in the brain is a hallmark of several neurodegenerative disorders. In Alzheimer's disease (AD) abnormal levels of naturally occurring proteins clump together to form plaques that accumulate in the brain and disrupt functions of neurons [1]. S100A9 protein has amyloid-like properties and can be found in senile plaques together with amyloid beta peptide ($A\beta$). S100A9 is involved in the formation of aggregates and inflammatory processes [2]. One prevailing hypothesis suggests that toxic effect of amyloids is accomplished through a membrane disruption mechanism, which leads to loss of synaptic efficiency, neuronal dysfunction, and degeneration [3].
Biomimetic lipid bilayer systems are a useful tool for modelling specific properties of cellular membranes. In this work the interaction between S100A9 protein and tethered bilayer lipid membranes (tBLMs) was studied. Here we formed tBLMs and optimised their properties. The aim of our work was to use tBLM as a membrane model for studying S100A9 protein-induced membrane damage. Atomic force microscopy (AFM) was used for characterization of S100A9. By employing electrochemical impedance spectroscopy (EIS) we monitored membrane damage caused by protein. We observed that S100A9 aggregates at different stages of oligomerization exhibit different ability to impair integrity of phospholipid membranes. In addition, the effect of S100A9 protein depends on the lipid composition of the membrane.