Conclusion
In this work, we established the FVIO-mediated magnetothermal
neurostimulation technique by systematically investigating the effect of
FVIO dose on stimulus-response time and the in vitro and in vivo
biosafety, as well as exploring the effectiveness of using this system
for long-term, repeated stimulation and magnetothermal regulation in the
deep brains of transgene-free mice. Benefiting from the superior
heat-generating performance of the FVIOs, anti-His antibody-coated FVIOs
triggered Ca2+ transients in both transfected 293T
cells and cortical neurons at a minimum Fe concentration of 54μg/mL, which was 20.27-fold lower than the Fe concentration in
the SPIOs. In vivo magnetothermal stimulation of the CeA in freely
moving mice demonstrated that the mice treated with FVIOs at the optimal
dose of 0.05 μg had a short latency to fear behavior response of
approximately 2.51 s , which was 2.3 times faster than that of
the SPIO-treated mice under the same AMF conditions. Furthermore,
FVIO-mediated magnetothermal stimulation was safer and allowed long-term
control of the freezing behaviors of mice for more than 60 days. Even in
nongenetically modified mice, 0.28 μg of FVIOs was able to
activate the endogenous TRPV1 in the CeA and elicit fear behaviors.
Overall, we believe that the FVIO-mediated efficient and safe
neuromodulation technique established in this study has potential for
future neuroscience and therapeutic applications.