Gold-Coated Lysozyme Fibrils: Preparation and Alignment

In Nature, materials exhibit a high degree of refinement, including a variety of molecular functionalities and interactions, specific physical properties, together with exquisite structures which can be observed at different length scales. Such diversity and specificity can be used to address some of the current issues and challenges of nanosciences. One particular challenge in this field is the high throughput production of conductive nanowires able to interconnect nanometer-sized building blocks which will be used in future electronic and bioelectronic applications. Many biological molecules and organisms are able to self-assemble into fibrilar structures. DNA, rod-like viruses, microtubules and protein fibers have for example been tested as potential templates for the synthesis of conductive nanowires.[1] Owing to their good resistance to heat, flexibility and dimensions, β-sheet-rich amyloid protein fibers are especially suited for nanofabrication. In this study the preparation of Hen egg white lysozyme (HEWL) amyloid fibers by thermal denaturation in solution [2] is optimised with the aim of obtaining oriented protein fibers on substrates. The slow fibrillisation of lysozyme and subsequent fiber bundling are monitored by deposition of protein samples on surfaces at different times during the heat treatment, followed by a topographical characterization of the surfaces using Atomic force microscopy (AFM). The onset of fiber nucleation and growth is correlated with a structural reorganization of lysozyme, as demonstrated by circular dichroism spectroscopy, in particular a sharp increase in the proportion of -sheet structures after 48h heating. On the basis of this fibrillogenesis study, samples comprising long fibers and a low number of aggregates are selected and incubated in the presence of amine-reactive gold nanoparticles, either before or after surface deposition/alignment. AFM and Kelvin Probe Force Microscopy (KPFM) [3] demonstrate the formation of hybrid bioinorganic fibers and the distribution of nanoparticles on the fibers surface.status: publishe