Speaker
Description
Membranes are an essential building block in cells, and their biophysical properties impact cellular metabolism and functions. Synthetic lipid membranes are widely used as model systems to understand properties of their much more complex biological counterparts. However, the accuracy of this approximation remains an open question. Advancements in sample preparation and instrumentation now allow the study of the structure of native biological membranes with an unprecedented resolution [1]. We isolated the cytoplasmic membrane from human red blood cells (RBCs) and measured its bending modulus κ using Neutron Spin Echo (NSE) Spectrometry and X-ray diffuse scattering (XDS). Despite their high cholesterol content of 50 mol%, we find surprisingly small bending rigidities between 2-6 kBT [2], much smaller than literature values of most single component lipid bilayers. We speculate that this extreme softness results from the presence of highly unsaturated lipids in biological membranes. We also show that this bending rigidity significantly increases during blood storage due to an increased fraction of liquid ordered membrane domains as function of storage time. This effect potentially explains the observed organ dysfunction and the increased mortality in patients who received older blood bags [3].
RBCs are ideal for pharmaceutical applications as they provide access to numerous targets in the human body and superior biocompatibility over synthetic particles. We developed protocols to functionalize RBC membranes to form hybrid membranes [4] that can contain different types of synthetic lipids and proteins. Erythro-VLPs (virus like particles) were designed by embedding the SARS-CoV 2 spike protein into RBC hybrid liposomes that work as COVID vaccine [5].
[1] S. Himbert, et.al. Scientific Reports 7 (39661), (2017)
[2] S. Himbert, et.al. The Bending Rigidity of Red Blood Cell Membranes, submitted
[3] S. Himbert, et.al. Plos one 16 (11), e0259267
[4] S. Himbert, et.al Advanced Biosystems, 1900185.
[5] S. Himbert, et.al. ErythroVLPs: Erythro-VLPs: anchoring SARS-CoV-2 spike proteins in erythrocyte liposomes, accepted for publication in Plos One
