 The researchers developed a new electrochemical sensor that can detect low levels of cancer antigen 15-3, Ca15-3. This sensor combines two modes of detection, electrochemiluminescence, ECL, and electrochemistry, EC. It uses a vertically ordered mesoparasilica film, VMSF, as a substrate, which is modified with a bifunctional probe containing both RU, Bpy, 32-plus, and epoxy-functional salines. When Ca15-3 binds to the antibodies attached to the VMSF, it forms an immune complex that blocks the flow of electrons between the electrodes. This causes a decrease in the current generated by the ECL reaction, while the EC reaction remains unaffected. The sensor can detect Ca15-3 at concentrations as low as 0.1 microgram per milliliter, G-slash-ML.