Functionalized ZnO nanorod-based selective magnesium ion sensor for intracellular measurements

Abstract

ZnO nanorods were grown on a silver-coated tip of a borosilicate glass capillary (0.7 μm in tip diameter) and used as selective potentiometric sensor of intracellular free Mg 2+. To functionalize the ZnO nanorods for selectivity of Mg 2+, a polymeric membrane with Mg 2+-selective ionophores were coated on the surface of the ZnO nanorods. These functionalized ZnO nanorods exhibited a Mg 2+-dependent electrochemical potential difference versus an Ag/AgCl reference microelectrode within the concentration range from 500 nM to 100 mM. Two types of cells, human adipocytes and frog oocytes, were used for the intracellular Mg 2+ measurements. The intracellular concentration of free Mg 2+ in human adipocytes and frog oocytes were 0.4–0.5 and 0.8–0.9 mM, respectively. Such type of nanoelectrode device paves the way to enable analytical measurements in single living cells and to sense other bio-chemical species at the intracellular level.