Harmonic Nanoparticles: High‐Speed Tracking of Murine Cardiac Stem Cells by Harmonic Nanodoublers (Small 17/2012)

Harmonic nanoparticles (HNPs), created by M. E. Jaconi, L. Bonacina, and co-workers on page 2752, label a neural rosette. HNPs double the frequency of NIR laser light, generating blue emission, while stem cells autofluoresce in green. The coherent nature of the HNP second harmonic emission is revealed by the appearance of an interference pattern. Thanks to the complete absence of bleaching or blinking and the possibility to be excited without wavelength limitation, HNPs are perfect for long-term tracking and depth tissue imaging of differentiating stem cell structures.