Laser-Induced Periodic Surface Structure Enhances Neuroelectrode Charge Transfer Capabilities and Modulates Astrocyte Function

Abstract

The brain machine interface (BMI) describes a group of technologies capable of communicating with excitable nervous tissue within the central nervous system (CNS). BMIs have seen major advances in recent years, but these advances have been impeded because of a temporal deterioration in the signal to noise ratio of recording electrodes following insertion into the CNS. This deterioration has been attributed to an intrinsic host tissue response, namely, reactive gliosis, which involves a complex series of immune mediators, resulting in implant encapsulation via the synthesis of proinflammatory signaling molecules and the recruitment of glial cells. There is a clinical need to reduce tissue encapsulation in situ and improve long-term neuroelectrode functionality. Physical modification of the electrode surface at the nanoscale could satisfy these requirements by integrating electrochemical and topographical signals to modulate neural cell behavior. In this study, commercially available platinum iridium (Pt/Ir) microelectrode probes were nanotopographically functionalized using femto/picosecond laser processing to generate laser-induced periodic surface structures (LIPSS). Three different topographies and their physical properties were assessed by scanning electron microscopy and atomic force microscopy. The electrochemical properties of these interfaces were investigated using electrochemical impedance spectroscopy and cyclic voltammetry. The in vitro response of mixed cortical cultures (embryonic rat E14/E17) was subsequently assessed by confocal microscopy, ELISA, and multiplex protein array analysis. Overall LIPSS features improved the electrochemical properties of the electrodes, promoted cell alignment, and modulated the expression of multiple ion channels involved in key neuronal functions.

Biomedical Implants with Charge‐Transfer Monitoring and Regulating Abilities

“…Results showed that microglia proliferation was hampered by nanoporous samples. A similar conclusion was obtained by research conducted by Chapman et al, [ 129b ] who constructed a nanoporous gold (np‐Au) electrode via an alloy corrosion process. The nanotopography of the np‐Au reduced astrocyte surface coverage while maintaining high neuronal coverage, which is expected to alleviate FBR and prolong the in vivo working time of the electrode.…”

“…Nanostructures have also been fabricated on other types of rigid electrodes including Ir and Au, and both Ir and Au electrodes with nanostructures have lower impedance and higher biocompatibility than their untreated counterparts. [ 129 ] However, some studies have pointed out that low‐dimensional nanomaterials may induce carcinogenic and teratogenic effects, [ 130 ] and thus the biosafety of these materials has yet to be tested before clinical trials. [ 131 ]…”

Hierarchical platinum–iridium neural electrodes structured by femtosecond laser for superwicking interface and superior charge storage capacity

“…Femtosecond laser processing has been recognized as an efficient approach to create numerous surface structures with reduced heat-affected zones, through ultrashort pulses. Because of the unique threshold effect, when the pulse energy is around the threshold value, a quasi-periodic structure with particles or ripples will be produced [12,25]. In this study, the pulse energy was significantly higher than the ablation threshold, and the material was precisely ablated, as shown in Fig.…”

Regulating Morphology and Composition of Laser-Induced Periodic Structures on Titanium Films with Femtosecond Laser Wavelength and Ambient Environment

“…Various theoretical approaches have been applied to explain the LIPSS occurrence, including the scattering-interference mechanism, excitation of surface electromagnetic waves (polaritons, plasmons), counter-propagating surface plasmons, and material reorganization [ 3 , 4 , 5 ]. Although a comprehensive theoretical picture is still in development, LIPSS attract research attention due to the remarkable simplicity and reliability of the single-step technique of patterning the surface with subwavelength periodic features suggesting a wide range of possible applications, such as surface colorization, reflection/transmission tuning, wettability and friction control, security marking, energy storage and solar cells efficiency enhancement, biosensing, living cell growth and adhesion control, and more [ 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 ].…”