Enhancement of Thermoplasmonic Neural Modulation Using a Gold Nanorod-Immobilized Polydopamine Film

Abstract

Photothermal neural activity inhibition has emerged as a minimally invasive neuromodulation technology with submillimeter precision. One of the techniques involves the utilization of plasmonic gold nanoparticles (AuNPs) to modulate neural activity by photothermal effects ("thermoplasmonics"). A surface modification technique is often required to integrate AuNPs onto the neural interface. Here, polydopamine (pDA), a multifunctional adhesive polymer with a wide light absorption spectrum, is introduced both as a primer layer for the immobilization of gold nanorods (GNRs) on the neural interface and as an additional photothermal agent by absorbing near-infrared red (NIR) lights for more efficient photothermal effects. First, the optical and photothermal properties of pDA as well as the characteristics of GNRs attached onto the pDA film are investigated for the optimized photothermal neural interface. Due to the covalent bonding between GNR surfaces and pDA, GNRs immobilized on pDA showed strong attachment onto the surface, yielding a more stable photothermal platform. Lastly, when photothermal neural stimulation was applied to the primary rat hippocampal neurons, the substrate with GNRs immobilized on the pDA film allowed more laser power-efficient photothermal neuromodulation as well as photothermal cell death. This study suggests the feasibility of using pDA as a surface modification material for developing a photothermal platform for the inhibition of neural activities.

Polydopamine-based plasmonic nanocomposites: rational designs and applications

“…[82][83][84] In 2022, Nam and co-workers developed a photothermal neural activity platform by immobilizing Au nanorods on the PDA film. 85 Empowered by the synergistic effects between the photothermal response of Au nanorods and the light-absorbing properties of the PDA film, the hybrid nanostructures allowed more energy-efficient photothermal neuromodulation. Francesco Galeotti et al fabricated a SERS substrate by in situ growth of Au NPs on the PDA film.…”

Conducting polymer‐based nanostructured materials for brain–machine interfaces

“…Such nanoporous arrays can tune cell adhesion and provide a high spatial resolution of electrical recording and stimulation. Besides porous nanosphere‐like structures, nanoclusters (Shah et al, 2013), or nanorods (Ganji et al, 2018; Jang et al, 2022) can further increase the electrode surface area. Zhou et al show that the Au nanorods layer (70 nm in diameter and 500 nm in length) on a flexible PI has approximately 25 times lower interface impedance than conventional planar electrodes (1.85 vs. 50 kΩ at 1 kHz), which corresponds well with the increase in surface area (Hong‐Bo Zhou et al, 2009).…”

Progress, Opportunities, and Challenges of Magneto-Plasmonic Nanoparticles under Remote Magnetic and Light Stimulation for Brain-Tissue and Cellular Regeneration

“…The unique optical property further enables the applications of Au NPs in ultrasensitive biosensing probes according to the LSPR-absorbance-band change [124] for the detection of dopamine [125,126] and alpha synuclein [127]. In addition to the application in the bi- On the other hand, the plasmonic effects are reported to inhibit neuronal activities [114], activate heat-sensitive ion channels [115] and light-sensitive ion channels [116], and stimulate action potentials [117]. For example, Jang et al reported the usage of gold nanorod to absorb NIR light and realize a photothermal neuronal modulation by inhibiting neural activities, such as reducing the spike rate [114].…”

“…In addition to the application in the bi- On the other hand, the plasmonic effects are reported to inhibit neuronal activities [114], activate heat-sensitive ion channels [115] and light-sensitive ion channels [116], and stimulate action potentials [117]. For example, Jang et al reported the usage of gold nanorod to absorb NIR light and realize a photothermal neuronal modulation by inhibiting neural activities, such as reducing the spike rate [114]. Others found that the laser stimulation of gold NPs could activate the heat-sensitive transient receptor potential vanilloid 1 (TRPV1) channel in nociceptive neurons, and turn that channel into a drug-entering site to allow the entrance of an N-type calcium-channel blocker for the purpose of silencing targeted nociceptors (Figure 7b) [115].…”