Plasmon rulers consisting of two optically coupled metal nanoparticles linked by biological macromolecules have provided a tool for bio-imaging and enzymology that is non-bleaching, non-blinking, and biocompatible.   To expand this technology to visualize the subtle conformational changes ubiquitous in biological systems, three-dimensional multicomponent nanoparticle assemblies are required.We report a chiral DNA-mediated nanoparticle assembly which exhibits circular dichroism (CD) and provides a unique substrate for detecting handedness in biological events. We calculated the optical response of metal nanoparticle assemblies using a coupled dipole model. Based on this model, we designed and synthesized a distorted DNA tetrahedron decorated with two 10 nm and two 20 nm diameter gold nanoparticles. A shorter side breaks the mirror plane, forming a chiral assembly. Calculations show that changes in the length of the shorter, symmetry breaking arm of the tetrahedron will change the intensity and spectral position of the CD, even inverting the handedness completely.

Chiral DNA-assembled gold nanostructure for biosensing

245th National Meeting (2013)

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