Celestine Blue is an electroactive indicator in DNA biosensors, strongly adsorbed on spinel phases and CNT (carbon nanotubes), facilitating dispersion, acting as a capping agent, and enabling the fabrication of spinel-decorated CNT. It is an efficient charge transfer mediator, significantly improving capacitive behavior. TiO2 nanoparticles doped with Celestine Blue can be used as a label in a sandwich immunoassay for the hepatitis C virus (HCV) core antigen [1] [2] [3].