Imaging prosthetic implant related wear debris in macrophages using coherent anti-Stokes Raman scattering spectroscopy

Wear debris produced from articulating prosthetic joints is thought to be phagocytosed by macrophages which then release pro-inflammatory cytokines leading to the eventual aseptic loosening of the implant. Currently it is difficult to image wear particles within cells due to the lack of suitable ways of introducing tag molecules into the materials. We report how coherent anti-Stokes Raman scattering (CARS) spectroscopy can be used to image unlabeled material within cells relying on inherent chemical contrast. Using model particles we show how CARS signals change with respect to size and environment of the scattering particle. Incubating particles of polystyrene, polymethylmethacrylate and polyethylene with RAW264.7 macrophage cells, we demonstrate that it is possible to image cells phagocyotosing particles as well as to characterize the location of particles in three dimensions using the inherent optical sectioning ability of CARS. These results suggest that CARS provides an important tool for monitoring the accumulation of wear debris generated from prosthetic implants.