Cyclic voltammetry (CV) was conducted on Cyt c free in solution (2 µM) and Cyt c conjugated to AuNPs to establish whether the redox ability of Cyt c is retained after conjugation. The heme group in Cyt c, containing iron at its centre, is responsible for the observed redox couple at approximately 0.09 V (oxidation peak) and 0.039 V (reduction peak), as shown in Figure and supported by the literature . The surface reactive groups of Cyt c, including carboxylic, amine, hydroxyl, and thiols, undergo protonation and deprotonation, but these events do not coincide with the redox peaks produced by the heme's Fe atom . The heme group in Cyt c plays a crucial role in the protein's primary functions, such as within the electron transport chain, where it facilitates electron transfer from complex II to complex III. Cyt c is also involved in apoptosis, acting as the first reversible point voltammograms' run from -0.2 to 1.2 V and PBS was used as the electrolyte (B).