Specific Designed Electrochemical Microprobes for Neural Therapy and Spectroscopic Analysis

Abstract

Electrochemistry is an effective analytical method for biological and surface analysis because of monitoring substances without destruction. For this, various-sized probes are used and micro-sized probe is especially useful for practical purposes due to producing optimal spatial resolution. In Part 1, we introduce a outline of analytical methods and explain why micro-sized electrochemical probe is needed for biological and surface analysis. In Part 2, Nanoporous Pt with extremely small (1–2 nm) and uniform nanopores, L2-ePt, was electrochemically investigated in embryo brain. For comparison study under precise control of electrochemical potential, we constituted an electrochemical cell beneath the embryo surface by introducing a flat and a nanoporous Pt twisted wires around which a Ag/AgCl wound. L2-ePt and flat Pt in the brain were compared with each other by conventional voltammetry and electrochemical impedance spectroscopy at the dc bias, which was carefully selected to minimize faradaic interference. The electrochemical behavior at L2-ePt implanted in embryo brain is immune to severe passivation and closer to an ideal capacitor than flat Pt. Lower electrode impedance of L2-ePt leads to less potential drop at the interface between the electrode and the extracellular solution, protecting the implanted system from unwanted faradaic reactions. Various aspects including the low electrode impedance and electrochemical stability of L2-ePt in the embryo brain suggest L2-ePt as a promising electrode material for effectively stimulating distant neuronal cells and recording local field potential signals. In Part 3, we suggest a new strategy for probe fabrication to simultaneously acquire electrochemical signals from ultramicroelectrode (UME) and spectroscopic information from surface-enhanced Raman scattering (SERS). The proposed Electrochemical-SERS (EC-SERS) probe was prepared by elaborately tuning the SERS-active gold microshell (μ-shell) to maximize Raman scattering, mechanically fixing it at the end of micropipette, and electrically connecting with the ruthenium inner layer through electroless deposition process. This μ-shell based SERS-active UME is barely smaller than the laser focal volume (ca. 2 μm in diameter) but still visible through optical microscope. It proposes novel opportunities to scanning electrochemical microscope (SECM) that enables gap-mode free in situ EC-SERS analysis in electrochemical and biological systems.