Neuro-SWARM3 is a system-on-a-nanoparticle probe, that enables non-invasive measurement of in vivo electrophysiological activity using near-infrared light. Neuro-SWARM3 converts electrophysiological activity to an optically detectable signal that can be picked up from outside the brain using near-infrared (NIR-II, 1000-1700 nm) light. Neuro-SWARM3 provides a bioelectrical signal detection capability in a single nanoparticle device that packs wireless powering, electrophysiological signal detection, and data broadcasting capabilities at nanoscale dimensions.
Neuro-SWARM3 uses optical excitation power transfer and signal readout primarily useful as a contrast agent for sensing the electrical field produced by neurons.
Neuro-SWARM3 enables direct measurement of local electric field dynamics through near-infrared light via localized surface plasmon enhanced scattering and electro-optic sensitivity to local electric-field dynamics, primarily through electrochromic loading of PEDOT: PSS.
NeuroSWARM3 can be made with a dielectric (silica, SiO2) and magnetic (magnetite, Fe3O4) core, covered by a metallic (gold) shell, an electrochromic polymer (PEDOT) coat, and optional surface functionalization with, for example, lipids or antibodies. This technology can also work with a semiconductor core, but methods to produce semiconductor nanoparticles that are uniform in shape and distribution remain elusive1.
The layers of NeuroSWARM3 can be altered to change the wavelength used for optical sensing, but it is originally designed for near-infrared wavelengths with dimensions of silica-gold-PEDOT layers totaling less than 200 nanometers in diameter.
A fundamental limitation of the implantable brain-machine interfaces (BMI) is the wiring requirements for power transfer and signal transmission. Microelectrode arrays (MEAs), the workhorse technology in neuroscience, offer multiplexed electrophysiological recordings with high temporal resolution. However, their use is inherently limited to a few hundred electrodes as direct electronic measurements suffer from complex wiring requirements and inherent bandwidth (spatial multiplexing) limitations due to electron-electron interactions within conductors. Moreover, electrode arrays can only record from small sections of the brain and require invasive cranial surgical operations.
The recent discovery of genetically encoded voltage-sensitive fluorescence indicators (GEVI) has created tremendous excitement as light offers unparalleled multiplexing and information-carrying capabilities. However, GEVI cannot be used in humans as it requires the expression of voltage-sensitive molecules by neurons and therefore genetic manipulation. In addition, attenuation of visible light in biological tissue renders much of the brain inaccessible to fluorescence-based techniques.
Neuro-SWARM offers five fundamental advancements simultaneously:
(1) it enables the use of infrared light within the biologically transparent near-infrared (NIR-II, 1000-1700 nm) window for direct read-out through the skull,
(2)it circumvents invasive surgical operations since no wiring or power supply is needed for the wireless electroplasmonic excitation and remote detection backscattering signal,
(3)due to its nanoscale dimensions (< 200 nm) comparable to viral particles, NeuroSWARM can be delivered to brain tissue through the blood or cerebrospinal fluid,
(4) as the electro-plasmonic signal conversion removes front-end signal processing requirements and enables optical read-out, it opens the door to large scale in vivo measurements that are not restricted by electrode dimensions, wiring, or electronic bandwidth limitations,
(5) by being much smaller than the critical dimensions that trigger glial cell response (~ 12 μm),it offers a long-term operation capability.
Name: Jeff Jackson
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