High levels of SOD2 are related to an increased frequency of invasion and metastasis of certain types of cancer (i.e. fibrosarcoma). Early detection of SOD2 in the circulatory or lymphatic system can help diagnosis and prognosis of these types of cancer. A highly sensitive method is required for detecting very low concentrations of this enzyme. The herein project detects collisions of a single CuZn SOD enzyme on the electrode’s surface. This detection is possible due to a catalytic amplification process occurring over the enzyme’s surface. The current transient is generated when the oxidation process occurs over the surface of the individual nanoparticle (CuZnSOD in this case) when this one impacts the ultramicroelectrode’s (UME) surface. The current blip generated is then use to calculate the enzyme's size. According to theoretical calculations, CuZn SOD has approximately 4 nm diameter. This number correlates with the size obtained by the electrochemical technique, and transmission electron microscopy (TEM) images.

Figure 1. Amperometric i vs t curve of a 0.089 fM CuZnSOD solution in phosphate buffer pH = 7.8 applying a potential of E = 0.2 V. Three electrode cell was used: a 10 μm Pt UME as the working electrode, Ag/AgCl as the reference electrode, and a Pt wire as the counter electrode.