Metallic nanoparticles for biomedical imaging

The plasmon resonance conditions in nano-sized materials leads to local field enhancement resulting in amplified response of various linear and nonlinear optical processes at the nano-scale. In this paper, metallic nanoparticles are imaged using several modalities - brightfield, confocal reflectance, two-photon, and second harmonic generation. Two examples are discussed - Au nanoparticles in the zebrafish spinal column, and Ag nanoparticles in fresh skin excisions. We show that the optical properties of noble-metal nanoparticles offer an attractive alternative to the fluorophore-based staining and labeling of biological samples, and have potential use in a wide range of biological and physical applications.