Mineralisation of Lysozyme Nanofibers: an Atomic Force Microscopy Study

Amyloid protein fibers are excellent candidates as templates for the formation of nanostructured materials owing to their mechanical properties, chemical resistance, self-assembly in a range of physicochemical conditions, and diameter as small as a few nanometers1. Moreover amyloid fibers are at the centre of many scientific investigations studying their pathological roles in disorders such as Alzheimer's and Parkinson's diseases, but also their functional properties that have been for a long time overlooked2. In electronic applications, conductive nanowires built from protein scaffolds have attracted much attention as a potential alternative to top-down fabricated wires. However, successful developments require a fundamental understanding of the mineralization process. In this contribution we have produced and analysed metal nanostructures formed from hen egg white lysozyme fibers and preformed gold nanoparticles. Atomic force microscopy (AFM) based methods provide topographical information of the hybrid nanostructure arrangement, and also offer the possibility to investigate their electrical properties at the nanometer scale using the Kelvin probe force microscopy (KPFM) modality3. The fibers growth process and kinetics are first studied using AFM and circular dichroism spectroscopy. The resulting protein scaffolds are then metallised by specifically grafting nanoparticles to their amine moieties, either when surface-bound or when suspended in solutions. The properties of bare and metal-coated structures are finally compared using intermittent-contact AFM and KPFM.status: publishe