Photoconductivity of Pea-Pod-Type Chains of Gold Nanoparticles Encapsulated within Dielectric Amyloid Protein Nanofibrils of α-Synuclein

摘要

Encapsulation of noble-metal nanoparticles within dielectric matrices has been used to develop fast optoelectric response systems near the surface plasmon resonance (SPR) fre-quency. Light energy can thus be transported through nanoparticles whose sizes are substantially smaller than the wavelength of corresponding light. We introduce herein a convenient bottom-up approach to fabricate a pea-pod-type gold-nanoparticle (AuNP) arrangement into anisotropic one-dimensional chain structures within the dielectric amyloid fibrils of α-synuclein. The assembly units composed of α-synuclein encapsulating AuNPs were manipulated by either hexane or the pH value to induce structural rearrangement within the protein coat. These structural alterations led to instantaneous AuNP alignment into the pea-pod-type chain structures from single- to multichain format wrapped with the fibrillar protein coat. These AuNP-embedded amyloid protein nanofibrils exhibited photoconductivity with visible light; this property is essential for the development of a subwavelength-size light-guiding system that could contribute to the continuous pursuit of miniaturization of nanooptics. Our approach, therefore, offers a facile and general means to align noble-metal nanoparticles into chain structures. Moreover, the properties of insulation, rich chemistry for modification, and biocompatibility provided by the protein sheath make the resulting nanochains multifunctional photoconductive fusion nanomaterials that are suitable for applications in future nano-biotechnology applications.