Assembly of collagen fibril meshes using gold nanoparticles functionalized with tris(hydroxymethyl)phosphine-alanine...

We report on the use of tris(hydroxymethyl)phosphine-alanine (THPAL) functionalized gold nanoparticles as a multivalent cross-linking agent to assemble collagen fibrils into a mesh-like structure. Atomic force microscopy (AFM) was used for characterization of the structure after adsorption onto an atomically flat mica substrate, revealing a mesh-like construct in which the collagen fibrils and the gold nanoparticles interact to form interconnected nodes measuring from 100 to 500 nm. As expected, the density of the collagen mesh can be increased with a higher initial concentration of gold nanoparticles. The maximum thickness of the meshes (∼ 20 nm) obtained through cross-sectional height measurements confirms that the adsorbed structure consists of a single layer of collagen fibrils/gold nanoparticles assembled in two-dimensions. We propose that the capability of gold nanoparticles functionalized with the THPAL to bind to several collagen fibrils combined with the large persistence length of the fibrils, which was reported to be in the hundreds of nanometer range, are determinant factors for the preferential 2D growth of the mesh in solution.