In Situ Investigation of the Cytotoxic and Interfacial Characteristics of Titanium When Galvanically Coupled with Magnesium Using Scanning Electrochemical Microscopy

Abstract

Recently, the cytotoxic properties of galvanically coupled Mg-Ti particles have been shown to different cells, although this cytotoxic effect has been attributed mainly to Mg due to its tendency to undergo activation when coupled with Ti forming a galvanic cell consisting of an anode (Mg) and a cathode (Ti). However, the role of the Ti cathode has been ignored in explaining the cytotoxic effect of Mg-Ti particles due to its high resistance to corrosion. In this work, the role of titanium (Ti) in the cytotoxic mechanism of galvanically coupled Mg-Ti particles was examined. A model galvanic cell was prepared to simulate the Mg-Ti particles.The electrochemical reactivity of the Ti sample and the pH change above it due to galvanic coupling with Mg were investigated using scanning electrochemical microscopy (SECM). It was observed that the Ti surface changed from passive to electrochemically active when coupled with Mg. Furthermore, after only 15 min galvanic coupling with Mg, the pH in the electrolyte volume adjacent to the Ti surface increased to an alkaline pH value. The effects of the galvanic coupling of Ti and Mg, as well as of the alkaline pH environment, on the viability of Hs27 fibroblast cells were investigated. It was shown that the viability of Hs27 cells significantly diminished when Mg and Ti were galvanically coupled compared to when the two metals were electrically disconnected. Next, the generation of reactive oxygen species (ROS) increased when the Ti and Mg were galvanically coupled. Thus, although Ti usually exhibited high corrosion resistance when exposed to physiological environments, an electrochemically active surface was observed when galvanically coupled with Mg, and this surface may participate in electron transfer reactions with chemical species in the neighboring environment; this participation resulted in the increased pH values above its surface and enhanced generation of ROS. These features contributed to the development of cytotoxic effects by galvanically coupled Mg-Ti particles.

In Situ Studies of Hydrogen Evolution Kinetics on Pure Titanium Surface: The Effects of Pre-Reduction and Dissolved Oxygen

“…However, under its service or experimental conditions, this film tends to be reduced by cathodic polarization. For example, Ti often works as the cathode when it is electrically coupled with a less noble metal, like Mg . Another typical example is the anodic oxidation of Ti, where a cathodic potential is often employed to remove the air-formed oxide film with poor conductivity. , Moreover, Ti and its alloys are often used in highly corrosive environments with low pH values, such as the industrial conditions containing H 2 SO 4 or H 2 S. , Under these conditions, the hydrogen evolution reaction (HER) on the Ti surface becomes a dominant reaction in a wide cathodic potential range.…”

“…Scanning electrochemical microscopy (SECM) is an in situ electrochemical technology to investigate the interface reactions in the fields of corrosion, , battery, catalysis, and so forth. In the study of corrosion, most studies focused on the mapping of reaction current at the metal/solution interface using typical redox couples, like ferrocenylmethanol (FeMeOH) and its cations (FeMeOH + ), with the planar metal electrodes as the substrate electrodes.…”