Plasmonic-Magnetic Active Nanorheology for Intracellular Viscosity

We demonstrate active plasmonic systems where plasmonic signals are repeatedly modulated by changing the orientation of nanoprobes under an external magnetic field, which is a prerequisite for in situ active nanorheology in intracellular viscosity measurements. Au/Ni/Au nanorods act as nanotransmitters, which transmit the mechanical motion of nanorods to an electromagnetic radiation signal as a periodic sine function. This fluctuating optical response is transduced to frequency peaks via Fourier transform surface plasmon resonance (FTSPR). As a driving frequency of the external magnetic field applied to the Au/Ni/Au nanorods increases and reaches above a critical threshold, there is a transition from the synchronous motion of nanorods to asynchronous responses, leading to the disappearance of the FTSPR peak, which allows us to measure the local viscosity of the complex fluids. Using this ensemble-based method with plasmonic functional nanomaterials, we measure the intracellular viscosity of cancer cells and normal cells in a reliable and reproducible manner.

Automated summary

We present active plasmonic systems that modulate plasmonic signals by changing the orientation of nanoprobes under an external magnetic field, enabling in situ nanorheology measurements of intracellular viscosity. Au/Ni/Au nanorods transmit mechanical motion to an electromagnetic radiation signal via a periodic sine function. This fluctuating optical response is transformed to frequency peaks by Fourier transform surface plasmon resonance (FTSPR). By increasing the driving frequency of the magnetic field, the synchronous motion of nanorods transitions to asynchronous responses, resulting in the disappearance of the FTSPR peak, allowing for measurement of local viscosity of complex fluids.