Gyromagnetic imaging: dynamic optical contrast using gold nanostars with magnetic cores.
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.
Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, Indiana 47907-2084, USA.
Qingshan
Q
Wei
Hyon-Min
HM
Song
Alexei P
AP
Leonov
Jacob A
JA
Hale
Dongmyung
D
Oh
Quy K
QK
Ong
Kenneth
K
Ritchie
Alexander
A
Wei
D001692:Biological Transport; D006046:Gold / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D007624:KB Cells; D049449:Luminescence; D008280:Magnetics; D053768:Metal Nanoparticles / Q000737:chemistry*; D009038:Motion; D055620:Optical Phenomena; D012399:Rotation; D013997:Time Factors; D041623:Tomography, Optical Coherence
D006046:Gold