Previous research has shown that there are multiple factors in redox protein immobilisation that could influence the redox ability and, therefore, function. Gold nanoparticles (AuNPs) are a material often used as an immobilisation platform for Cyt c to exploit its ability to induce apoptosis or use as a biosensor due to their biocompatibility and unique optical properties . A previous study by found that smaller AuNPs had stronger electrochemical interactions when oxidising with L-cysteine (a thiol-containing amino acids), possibly due to the formation of agglomerates , suggesting that the redox ability of a protein like Cyt c could be influenced by the size of the material it is immobilised upon. Ligand exchange is a common way that the functionality of AuNPs can be modulated and is often required for the immobilisation of a protein like Cyt c. Ligand exchange produces three factors that could influence the redox ability of Cyt c, the distance between the surface of the material, the position at which Cyt c is conjugated to the ligand and the method used to conjugate Cyt c to the ligand. Previous work produced by showed that increasing the distance between a redox molecule and an electronrich node can reduce electron transfer abilities, as seen with ruthenium hexamine . Although this system differs from the present case, the principle may still apply to Cyt c and the iron at the centre of the heme contained within the protein and is responsible for the electron transfer abilities.