Star-shaped gold nanoparticles as friendly interfaces for protein electrochemistry: the case study of cytochrome c

Gold nanostars with an average tip-to-tip length of 52±6 nm were functionalized with different capping agents and used as electrode modification materials for protein electrochemistry. Direct electron transfer between cytochrome c and nanostar-coated pyrolytic graphite electrodes was observed with the protein in solution. The electrochemical response was improved at nanostars functionalized with a 1 : 1 mixture of 11-mercaptoundecanoic acid and 4-mercaptobenzoic acid in comparison with gold nanospheres coated with a similar functionalization. Further immobilization of cytochrome c on pyrolytic graphite while conjugated with the same nanostars guaranteed the maintenance of the protein's native properties, whereas direct adsorption on the bare or nanostar-modified electrodes resulted in an altered conformational state. The pseudo-peroxidase activity of the altered cytochrome c was enhanced in the presence of the nanostars.