Laser induced periodic surface structures enhance neuroelectrode charge transfer capability and modulate astrocyte function in vitro

The brain machine interface (BMI) describes a group of technologies capable of communicating with excitable nervous tissue within the central nervous system (CNS). BMI’s have seen major advances in recent years but these advances have been impeded due to 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 (NT) 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.