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Bart Stel1 Karla Banjac1 Chiara Masellis2 Sabine Abb3 Klaus Kern3 Thomas Rizzo2 Stephan Rauschenbach3 Magalí Lingenfelder1 3

1, EPFL, Lausanne, , Switzerland
2, EPFL, Lausanne, , Switzerland
3, Max-Planck-Institute for Solid State Research, Stuttgart, , Germany

Biointerfaces are ubiquitous in nature as well as in technological applications such as biosensors and medical implants. Their structure and response to stimuli are ultimately determined by intra- and intermolecular interactions at the nanoscale. In order to achieve functional biointerfaces at the nanoscale over macroscopic areas, bottom-up fabrication through self-assembly is one of the few viable fabrication pathways. However, the rational use of self-assembly requires a deep understanding of the underlying forces that drive the interactions between individual building blocks and their surroundings.
We present a systematical study of self-assembly at the nanoscale using model systems such as synthetic peptides and self-assembling proteins. Synthetic peptides are highly tunable due to their modular nature, large variety of functional groups and well-established techniques for synthesis. Additionally, 2D self-assembling protein layers (S-layers) present a robust and biomimetic approach to surface functionalization.
Electrospray Ion Beam Deposition (ES-IBD) enables full control over the transfer of large biomolecules to the solid-vacuum interface. By comparing ES-IBD and in situ drop casting techniques, a direct comparison is possible between self-assembly at the solid-vacuum interface (UHV conditions) and self-assembly at the solid-liquid interface.
In this way, the self-assembly of alanine-based peptides was locally studied in different environments, i.e. gas phase, solid-vacuum and solid-liquid interface. Thus enabling the underlying intra- and intermolecular interactions to be elucidated. By carefully choosing both deposition and imaging conditions, specific self-assembling behavior can be selected. This control over the conformational output allows us to tune the function exposed at the biointerface. Furthermore, high-speed in situ Atomic Force Microscopy is used to resolve the intermolecular dynamics of biomolecular self-assembly on a variety of surfaces.

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