Abstract
Nitric oxide (NO) is known to mediate many beneficial physiology processes, motivating its detection in vivo as well as in vitro. Electrochemical detection provides the required cellular level determination of NO among several other techniques.
In this work, electrochemical micro-sensors for both types of detection, in vivo and in vitro, were developed, exploring the silicon planar technology, which presents high yield and reliability and also permits batch fabrication.
The developed in vitro sensor features eight detection sites (10 μm × 10 μm microelectrodes), for determination of nitric oxide spatial distribution or multi-species analysis. Different electrochemical methods were applied to provide sensor calibration and chemical reproducibility.
For in vivo analysis, the designed structures have a needle shape (40 μm thick) and they were silicon micro-machined by using plasma etching or etch stop techniques. Different configurations were designed and implemented, containing a number of detection microelectrodes that vary from 2 to 10.
The amperometric detection of both nitric oxide and nitride (NO2−) — a molecule that causes an interference — were investigated by using the in vitro micro-sensor configuration. The need of a cationic exchanger (Nafion) was demonstrated in order to provide selectivity to NO for low concentrations. Also, the developed sensor has a sensitivity of 500 A/M.cm2 and a detection limit of 10 μM.
