Fabrication of cone-shaped boron doped diamond and gold nanoelectrodes for AFM-SECM

We demonstrate a reliable microfabrication process for a combined atomic force microscopy (AFM) and scanning electrochemical microscopy (SECM) measurement tool. Integrated cone-shaped sensors with boron doped diamond (BDD) or gold (Au) electrodes were fabricated from commercially available AFM probes. The sensor formation process is based on mature semiconductor processing techniques, including focused ion beam (FIB) machining, and highly selective reactive ion etching (RIE). The fabrication approach preserves the geometry of the original AFM tips resulting in well reproducible nanoscaled sensors. The feasibility and functionality of the fully featured tips are demonstrated by cyclic voltammetry, showing good agreement between the measured and calculated currents of the cone-shaped AFM-SECM electrodes.

Cytotoxicity evaluation of polymer-derived ceramics for pacemaker electrode applications.

Ceramics are known to be chemically stable, and the possibility to electrically dope polymer-derived ceramics makes it a material of interest for implantable electrode applications. We investigated cytotoxic characteristics of four polymer-derived ceramic candidates with either electrically conductive or insulating properties. Cytotoxicity was assessed by culturing C2C12 myoblast cells under two conditions: by exposing them to material extracts and by putting them directly in contact with material samples. Cell spreading was optically evaluated by comparing microscope observations immediately after the materials insertion and after 24 h culturing. Cell viability (MTT) and mortality (LDH) were quantified after 24-h incubation in contact with the materials. Comparison was made with biocompatible positive references (alumina, platinum, biocompatible stainless steel 1.4435), negative references (latex, stainless steel 1.4301) and controls (no material present in the culture wells). We found that the cytotoxic properties of tested ceramics are comparable to established reference materials. These ceramics, which are reported to be very stable, can be microstructured and electrically doped to a wide range of conductivity and are thus excellent candidates for implantable electrode applications including pacemakers.