Iron Oxide–Gold Core–Shell Nanoparticles: A Review of Spectral Properties for Multimodal Imaging and Targeted Therapy

Dr. E. Martins, Dr. T. Becker, Dr. J. Park, Dr. F. Dubois, Dr. A. Khan, Prof. L. Henderson

Abstract:

Multimodal nanotheranostics have emerged as a promising tool for combining both therapy
and diagnosis of disease into a single nanoplatform. Herein we explore further the optical
properties of core-shell, magnetic-plasmonic nanoparticles and their potential for
bioapplication in photothermal therapy and diagnostic imaging.
Through modification of commercial magnetite nanoparticles, magnetic-plasmonic, Fe3O4-Au,
nanoparticles were synthesised with various levels of gold coverage, ranging from a textured
core-satellite structure to a full-coverage smooth gold shell with structural verification by
transmission electron microscopy. Single-particle broadband dark-field scattering
microspectroscopy and solution extinction (absorption) experiments were used to optically
characterise the nanoparticles. Interestingly, a significant spectral drift of up to 110 nm was
observed between the experimental extinction and scattering.
We note that this spectral drift is potentially advantageous in multimodal applications and
demonstrate experimentally that it leads to enhanced photothermal activity away from the
wavelengths where imaging via scattering is best. To explore these applications, infrared
thermography and laser dark-field microscopy were used to monitor the photothermal activity
and imaging, respectively. We propose that the enhanced photothermal response results
directly from a reduced competition between absorption and scattering stemming from spectral
drift.