Bioinspired optical antennas: Gold plant viruses

The ability to capture the chemical signatures of biomolecules (i.e., electron-transfer dynamics) in living cells will provide an entirely new perspective on biology and medicine. This can be accomplished using nanoscale optical antennas that can collect, resonate and focus light from outside the cell and emit molecular spectra. Here, we describe biologically inspired nanoscale optical antennas that utilize the unique topologies of plant viruses (and thus, are called gold plant viruses) for molecular fingerprint detection. Our electromagnetic calculations for these gold viruses indicate that capsid morphologies permit high amplification of optical scattering energy compared to a smooth nanosphere. From experimental measurements of various gold viruses based on four different plant viruses, we observe highly enhanced optical cross-sections and the modulation of the resonance wavelength depending on the viral morphology. Additionally, in label-free molecular imaging, we successfully obtain higher sensitivity (by a factor of up to 10⁶) than can be achieved using similar-sized nanospheres. By virtue of the inherent functionalities of capsids and the plasmonic characteristics of the gold layer, a gold virus-based antenna will enable cellular targeting, imaging and drug delivery.