2 research outputs found
Magnetic Nanoparticles for Ultrafast Mechanical Control of Inner Ear Hair Cells
We introduce cubic magnetic nanoparticles as an effective tool for precise and ultrafast control of mechanosensitive cells. The temporal resolution of our system is ∼1000 times faster than previously used magnetic switches and is comparable to the current state-of-the-art optogenetic tools. The use of a magnetism-gated switch reported here can address the key challenges of studying mechanotransduction in biological systems. The cube-shaped magnetic nanoparticles are designed to bind to components of cellular membranes and can be controlled with an electromagnet to exert pico-Newtons of mechanical force on the cells. The cubic nanoparticles can thus be used for noncontact mechanical control of the position of the stereocilia of an inner ear hair cell, yielding displacements of tens of nanometers, with sub-millisecond temporal resolution. We also prove that such mechanical stimulus leads to the influx of ions into the hair cell. Our study demonstrates that a magnetic switch can yield ultrafast temporal resolution, and has capabilities for remote manipulation and biological specificity, and that such magnetic system can be used for the study of mechanotransduction processes of a wide range of sensory systems
Quantitative Measurements of Size-Dependent Magnetoelectric Coupling in Fe<sub>3</sub>O<sub>4</sub> Nanoparticles
Bulk magnetite (Fe<sub>3</sub>O<sub>4</sub>), the loadstone used in magnetic compasses,
has been known to exhibit magnetoelectric (ME) properties below ∼10
K; however, corresponding ME effects in Fe<sub>3</sub>O<sub>4</sub> nanoparticles have been enigmatic. We investigate quantitatively
the ME coupling of spherical Fe<sub>3</sub>O<sub>4</sub> nanoparticles
with uniform diameters (<i>d</i>) from 3 to 15 nm embedded
in an insulating host, using a sensitive ME susceptometer. The intrinsic
ME susceptibility (MES) of the Fe<sub>3</sub>O<sub>4</sub> nanoparticles
is measured, exhibiting a maximum value of ∼0.6 ps/m at 5 K
for <i>d</i> = 15 nm. We found that the MES is reduced with
reduced <i>d</i> but remains finite until <i>d</i> = ∼5 nm, which is close to the critical thickness for observing
the Verwey transition. Moreover, with reduced diameter the critical
temperature below which the MES becomes conspicuous increased systematically
from 9.8 K in the bulk to 19.7 K in the nanoparticles with <i>d</i> = 7 nm, reflecting the core–shell effect on the
ME properties. These results point to a new pathway for investigating
ME effect in various nanomaterials