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In this image, gold nanorods, embedded in a cell-populated collagen gel, scatter light as viewed under a darkfield microscope. The collective excitation of electrons in the conduction band of gold nanoparticles arising from resonance with incident-visible radiation is referred to as localized surface plasmon resonance.
This excitation leads to resonant Rayleigh light scattering. Because of this strong scattering, individual nanoparticles, much smaller than the wavelength of light, can be observed using an optical microscope. There has been considerable interest in resonant Rayleigh scattering from gold and silver nanoparticles for biological and chemical analysis. In this application, a fibroblast-seeded collagen gel, an in vitro material system often used to model wound healing, is embedded with nanoparticles. The pattern of scattered light will be tracked using computerized pattern matching and image correlation techniques to measure the deformation that occurs as the collagen gel contracts, in a simulation of the formation of scar tissue. It is hoped that these small scale measurements will illustrate local heterogeneity in the mechanical response of the material.Image credit: The USC Nanocenter
