Controlling Diffusion in Lipid Mesophases: Implications for Protein Crystallization, Reconstitution & Biosensors Developments

Speaker : Prof Raffaele Mezzenga – ETH Zürich

Venue    : 5 May 2016 – 4pm (Murdoch University, ECL1.031 – 1 floor below ECL2.031)

Lipid-based reversed liquid crystalline mesophases, such as bicontinuous cubic, reversed hexagonal or reversed micellar cubic phases, have attracted deep interest in the last few decades due to their potential applications in the food, cosmetic and pharmaceutical arenas. Different crystallographic structures of the lipid mesophase give access to different diffusion coefficients and distinct ensued diffusion and transport modes of both hydrophilic and hydrophobic molecules. It becomes thus crucial to engineer the space group of the mesophases in a controlled way, in order to provide a rationale design for all physical mechanisms associated with molecular transport within the lipid nanostructures. In this talk I will discuss our recent contributions to control molecular transport within lipid mesophases, by either exploiting endogenous or exogenous stimuli and I will emphasize how this has direct implications for in-meso protein crystallization, in-meso enzymatic reactions, protein reconstitution and biosensors development. A new detection strategy relying on nanoconfined enzymatic reactions coupled with molecular recognition and birefringence development in-meso for detection of biomarkers, viruses, bacteria and parasites will be introduced and discussed.

Figure 1. (a) Detection of E. Coli with cubic mesophases. (b) A simple biosensors made of lipidic cubic phases.⁵

References

1. Garti N, Somasundaran P, Mezzenga R., “Self-Assembled Supramolecular Architectures: Lyotropic Liquid Crystals”, Wiley (2012)

2. Zabara A, Negrini R, Onaca-Fischer O, Mezzenga R “Perforated bicontinuous cubic phases with pH-responsive interconnectivities”. Small, 9, 3602 (2013)

3. Vallooran JJ., Negrini R., Mezzenga R., “Controlling Anisotropic Drug Diffusion in Lipid-Fe3O4 Nanoparticle Hybrid Mesophases by Magnetic Alignment”, Langmuir, 29, 999 (2013)

4. Negrini R., Mezzenga R., “Diffusion, Molecular Separation, and Drug Delivery from Lipid Mesophases with Tunable Water Channels”, Langmuir, 28, 16455 (2012).

5. Vallooran, J. J., Handschin, S., Pillai, S.M., Vetter, B.N, Rusch, S., Beck, H.P., Mezzenga, R. (2016) Lipidic Cubic Phases as a Versatile Platform for the Rapid Detection of Biomarkers, Viruses, Bacteria, and Parasites, Adv. Funct. Mater., 26, 181-190.

Mimicking magnets with lattices of bacterial vortices

Speaker : Dr Francis Woodhouse – Cambridge University

Venue    : Thu 7 Apr 2016 @ 4pm, Murdoch University, room ECL1.031 (below ECL2.031)

When alone in an unbounded fluid, a rod-shaped motile bacterium like E. coli will swim in straight lines punctuated by random turns. Pack many of them together in the same fluid, however, and they adopt collective swirling patterns akin to macroscopic turbulence. Confining the bacteria within a small circular cavity tames this turbulence and leads instead to a steadily spinning bacterial vortex. If many such vortices are then linked together in a square lattice of cavities, the rotation sense of a vortex becomes dependent on those of its neighbours. By declaring the senses to be ‘up’ and ‘down’ spins, the result is a bacterial analogue of an Ising ferromagnet. After explaining the background to these so-called ‘active matter’ systems, I will explore the challenges involved in mapping classical statistical physics models to this decidedly non-classical system – but only after revealing an entirely unexpected twist in the experiments.