Gallstone Formation Inspired Bimetallic Supra-Nanostructures for Computed Tomography Image Guided Radiation Therapy

Authors

Abstract

Inspired by the gallstone formation mechanism, we report a fast one-pot synthesis of high surface area bimetallic hierarchical supra-nanostructures. As gallstones are generated from metal-cholate complexes, cholate bile acid molecules with Au/Ag metal precursors formed stable nanocomplexes aggregated with metal Au ions and preformed ~ 2 nm silver halide nanoparticles before the reduction. When a reducing agent was added, the metal-cholate nanocomplexes quickly formed noble bimetallic hierarchical supra-nanostructures. The morphology of bimetallic supra-nanostructures could be tailored by changing the feeding ratio of each metal precursor. In situ synchrotron SAXS measurement with a custom designed reaction cell showed a two-step growth and attachment behavior towards hierarchical supra-nanostructures from the gallstone formation inspired metal-cholate nanocomplexes in a 60-second reaction. Additional WAXS, XANES, in situ FT-IR and high-resolution STEM investigations subsequently revealed the mechanism for the evolution of bimetallic hierarchical supra-nanostructures. The gallstone formation inspired synthesis mechanism can be universally applied to other metals, for example Pt-Ag and Pd-Ag bimetallic nanostructures. Finally, the synthesized high surface area bimetallic suprananostructures demonstrated significantly enhanced X-ray CT imaging contrast and radiosensitizing effect for a potential image guided nanomedicine application. We believe that our synthetic method inspired by gallstone formation and understanding represent an important step towards the development of hierarchical nanoparticles for various applications.