Nickel Nanowires Combined with Surface-Enhanced Raman Spectroscopy: Application in Label-Free Detection of Cytochrome c-Mediated Apoptosis.

Intrinsic properties of nickel have enabled its wide applications as an effective catalyst. In this study, nickel nanowires (Ni NWs) as electron donors for oxidized cytochrome c (Cyt c) are investigated, which are NW diameter, temperature, and pH value-dependent. The reductive and magnetic properties facilitate the Ni NWs to rapidly and conveniently reduce Cyt c in complicated biological samples. Moreover, we find that the Ni NWs combined with resonance Raman spectroscopy have specificity toward Cyt c detection in real biological samples, which is successfully used to distinguish the redox state of the released Cyt c from isolated mitochondria in apoptotic Hela cells. Moreover, rapid label-free Cyt c quantification can be achieved by surface-enhanced Raman spectroscopy with a limit of detection of 1 nM and long concentration linear range (1 nM-1 µM). The proposed Ni NWs-based reduction approach will significantly simplify the traditional biological methods and has great potential in the application of Cyt c-related apoptotic studies.