Colloid conference ECIS-2024 from the perspective of membrane biophysics

Written by Aleksei Nesterenko, PostDoc at CBU, University of Bergen

I attended the yearly European Colloid and Interface Society meeting in Copenhagen on 1-6th of September with my poster about the computation of microscopic stress at phase interfaces. As I am focused on lipids in my theoretical and experimental work, I want to share a brief review of the lipid component of this conference.

The first impression is that the most interesting lipid object for colloid scientists is now cubosomes and lipid-NA nanoparticles. The interest in the second object is clear because it was mostly facilitated by mRNA anti-covid vaccines; regarding this topic I would highlight the talk of Prof. Tobias Unruh from FAU (Erlangen-Nürnberg) who showed their neutron scattering data about these types of nanoparticles, especially about particles in the production bioNtech vaccine. Surprisingly, the scientific consensus regarding how these vaccines are organized is still under development. Tobias presented a talk mostly focused on his later publication in ACS Nano and mentioned the progress (very significant!) of the knowledge about these nanoparticles’ structure comparing to the information provided by the vaccine manufacturer to the European regulator.

Cubosomes – are lipid nanoparticles of cubic (bicontinuous phase). The high interest in cubosomes is still not completely clear for me, but according to many talks I would mention these properties:

• They are surprisingly stable. Participants showed a lot of TEM images of cubosomes which were quite large.
• They are good for delivery. If the aqueous subphase of a cubosome is loaded with some compound, this compound would diffuse from the interior relatively slowly.
• They have a natural preference in fusing with a lipid bilayer; however, I didn’t hear any talks or posters about the effectivity of this fusion, but this is probably a “bread” for membrane biophysicists.
• There are 3 types of cubic phases with different exchange rates between interior and exterior, and it is principally possible to induce a phase transition in pre-formed cubosomes.

Regarding the last point, I can mention the talk of Luna Gade (University of Copenhagen) who tried to analyse if it’s possible to switch cubosome by exposing to phospholipase A2. That’s an interesting thing for me, because she proposed that PL A2 can induce additional positive curvature in the layer by dividing lipids, which should in turn switch a cubosome from one symmetrical form to another. Seems that the work is at the preliminary stage, but it looks promising.

I brought to the conference my study about computing bending preference in lipid monolayers using virtual deformation approach (VDA), and there were many people who declared their interest in monolayer curvatures or intrinsic surfactant curvature. In one project, they even tried to compute intrinsic curvatures, but with a different method than I used. It was presented by Magali Duvail from the Institute of Separation Chemistry located in the orbit of Marcole Nuclear Site. She presented a published study about simulation of lanthanide extraction to the oil phase promoted by formation of inverted micelles with anionic surfactants. The free energy of these micelles’ formation depends on surfactant intrinsic curvature which they measured from MD simulation of micelle shape fluctuation.

What was also quite interesting for me is the manifold of scattering and reflectometry studies of lipid structures. I was especially interested in the studies with bacterial lipid lipopolyaccharide – and I met them: one poster of Samantha Micciula (from CNRS, Grenoble) and one talk by Bettina Tran (from University of Freiburg) brought their research with LPS to the conference. Bettina worked with LPS-containing liposomes whereas Samantha worked with langmuir monolayers of LPS.

Finally, it was a very fruitful conference and I would be happy to visit it again with my lipid projects.