Bart Stel1 3 Ilja Gunkel4 5 2 Xiaodan Gu5 7 Behzad Rad3 Alexander Hexemer4 Thomas Russell5 James De Yoreo6 3 MagalĂ­ Lingenfelder1 3

1, EPFL, Lausanne, , Switzerland
3, Lawrence Berkeley National Laboratory, Berkeley, California, United States
4, Lawrence Berkeley National Laboratory, Berkeley, California, United States
5, University of Massachusetts Amherst, Amherst, Massachusetts, United States
2, Adolphe Merkle Institute, Fribourg, , Switzerland
7, Stanford University, Stanford, California, United States
6, Pacific Northwest National Laboratory, Richland, Washington, United States

One of the key challenges in the field of bottom-up fabrication is the rational use of existing self-assembling systems, while maintaining the level of control required for actual applications. Here we present a hierarchical bottom-up approach to controlled self-assembly. Self-assembled PS-b-PEO block copolymer (BCP) thin films express nanopatterned structures over macroscopic areas. The Non-specific interactions between chemically heterogeneous nanodomains and individual proteins is used to direct the self-assembly of bacterial surface layers (S-layers) in situ at the nanoscale. A comparison between physically and chemically patterned BCP substrates shows that chemical heterogeneity is required to confine the adhesion and eventual self-assembly of proteins to specific domains.
Collagen is the main structural protein in vertebrates and collagen films have been widely used as substrate to facilitate cell adhesion or as adhesion matrix for specific collagen-binding proteins. For this reason, a high level of local control over the position and orientation of collagen fibers is desired. The principle of hierarchical bottom-up self-assembly has been used to direct the formation of collagen fibers. It has been demonstrated that nanopatterned PS-b-PEO striped patterns can be used to direct the self-assembly of collagen molecules in situ along the local direction of the underlying substrate.
The dynamics of protein self-assembly at the solid-liquid interface is followed using high-resolution AFM measurements in an in situ continuous flow environment. This allows for the extraction of self-assembly rate constants. It has been shown that a pattern of alternating, chemically distinct nanoscale domains drastically increases both the rate of self-assembly as well as the total protein load compared to non-patterned chemically homogeneous substrates.