Unravelling adsorption and alignment of amyloid fibrils at interfaces by probe particle tracking

Abstract

We report the first direct, non-invasive experimental evidence of a 2D isotropic-nematic transition for highly anisotropic nanoparticles at liquid-liquid interfaces by using passive fluorescent particle tracking. In order to illustrate the potential of this approach on systems of high real practical and biological relevance, we select as a model anisotropic nanoparticles b-lactoglobulin amyloid fibrils of varying aspect ratios. Upon nanoparticle adsorption at the interface, we follow, in real time and as a function of fibril length and bulk concentration, the development of a 2D nematic phase by studying the anisotropy in probe particle traces. We furthermore demonstrate the long-range nature of the nematic phase by calculating order parameters for the traces as high as 0.8 over 10 2 to 10 3 mm 2 areas. The presented route is independent of the system investigated, and thus these findings open a new, general strategy for the experimental assessment of 2D structural changes at anisotropic fluid-fluid interfaces.

Non-equilibrium nature of two-dimensional isotropic and nematic coexistence in amyloid fibrils at liquid interfaces

“…A possible interpretation is that when adsorption takes place from low c init , it proceeds at low enough rates to allow fibrils to align into defined and isolated 2D domains. This is supported by passive probe particle tracking data, showing that trace anisotropy occurs while tracer motion is still diffusive 8 . At higher c init , the quenching rate is too high to permit unperturbed in-plane rotational rearrangement needed for the formation of nematic domains, leading to structures jammed into a more disordered alignment, hereby limiting the size of nematic domains, and yielding an overall viscoelastic interface (see Supplementary Fig.…”

“…LC alignment can also occur in two dimensions (2Ds) via interfacial adsorption and confinement. Of particular interest is the self-organization of macromolecules with a high aspect ratio into LC assemblies at interfaces, which has been treated theoretically [4][5][6] but less frequently shown experimentally 7,8 . In contrast to the 3D case and under the assumption of thermodynamic equilibrium, the 2D IN transition can be of first 4 , second order 5 , or of the Kosterlitz-Thouless continuous type leading to quasi-long-range order [9][10][11] , depending on the interactions between particles 12 and their rigidity 10 .…”

Amyloid Fibrils as Building Blocks for Natural and Artificial Functional Materials

“…In addition to genetically engineered amyloid fibrils demonstrating superior adhesion purposes, adhesiveness of amyloid fibrils tends to be a general fingerprint of these systems. It is likely that it is primarily the unique combination of the chemical nature of amyloid fibrils –composed of several amino acids with different amphiphilicity‐, with their nanoscopic dimensions, which provide them a very strong affinity for a variety of heterogeneous interfaces, such as the air‐water, oil‐water and lipid membranes‐water interfaces ‐for the liquid‐liquid interfaces‐, but also for liquid‐solid interfaces, the latter feature being exploited in the formation of layered composites, as discussed below. Indeed, by taking into account the commonly observed high aspect ratio of amyloid fibrils, the association energy of amyloid fibrils to liquid interfaces was calculated to be of the order of 60000 K B T, leading essentially to an irreversible adsorption and binding to the interfaces, with a stabilization mechanism very similar to Pickering stabilization.…”

Domain walls in two-dimensional nematics confined in a small circular cavity

“…When the density is increased from a dilute state, the bulk isotropic-nematic transition [6][7][8][9] induces some kind of orientational ordering in the cavity. However, due to the surface, the nematic director is unable to adopt a defect-free uniform configuration, and a global topological charge +1 [10] arises in the cavity: either as a central +1 disclination, or as two diametrically opposed +1/2 disclinations (on the surface or at a distance from it).…”