Macrophage uptake of 100nm polystyrene beads

CARS microscopy can be used to visualise polystyrene nanoparticles uptaken by live cells. The figure shows 100 nm polystyrene beads in cultured macrophage cells; the vibrational signatures of the nanoparticles and the cells can be separated by tuning (&omega _p – &omega_s). The green image contrast corresponds to the CH₂ of lipids (2485 cm^-1) and the red C=C vibrational stretch of polystyrene (~1600 cm^-1). This study is facilitated by the strong Raman response and high density of CH₂ groups in lipids and C=C in polystyrene, which yield strong CARS signals.