TY - DATA T1 - Gyromagnetic Imaging: Dynamic Optical Contrast Using Gold Nanostars with Magnetic Cores PY - 2009/07/22 AU - Qingshan Wei AU - Hyon-Min Song AU - Alexei P. Leonov AU - Jacob A. Hale AU - Dongmyung Oh AU - Quy K. Ong AU - Kenneth Ritchie AU - Alexander Wei UR - https://acs.figshare.com/articles/journal_contribution/Gyromagnetic_Imaging_Dynamic_Optical_Contrast_Using_Gold_Nanostars_with_Magnetic_Cores/2841772 DO - 10.1021/ja901562j.s003 L4 - https://ndownloader.figshare.com/files/4539505 KW - signal KW - contrast KW - gyromagnetic imaging KW - Dynamic Optical Contrast KW - background KW - NIR KW - nanostar N2 - Plasmon-resonant nanoparticles with optical scattering in the near-infrared (NIR) are valuable contrast agents for biophotonic imaging and may be detected at the single-particle limit against a dark background, but their contrast is often limited in environments with high noise. Here we consider gyromagnetic imaging as a dynamic mode of optical contrast, using gold nanostars with superparamagnetic cores. The nanostars exhibit polarization-sensitive NIR scattering and can produce a frequency-modulated signal in response to a rotating magnetic field gradient. This periodic “twinkling” can be converted into Fourier-domain images with a dramatic reduction in background. We demonstrate gyromagnetic imaging of nanostars inside of tumor cells, using broadband excitation: while their time-domain signals are obscured by incoherent scattering, their Fourier-domain signals can be clearly resolved in less than a second. The gyromagnetically active nanostars do not cause a loss in viability, and can even have a mild stimulatory effect on cell growth. ER -