Gold nanoparticle-mediated electron transfer of cytochrome c on a self-assembled surface

Abstract

The presence of gold nanoparticles (AuNPs) at the protein/electrode interface has a significant impact on the electrodic microenvironment, and allows the optimization of the activity catalysis as well as electrochemical properties. Here, we report a novel and accurate methodology to observe AuNP mediated electron transfer mechanism from Cytochrome c (Cyt c) to a polycrystalline gold surface. Poly(allylamine hydrochloride) molecules (PAH) were used as spacers between Cyt c and the electrode surface, and the electron rate constant within the PAH layer was measured in the presence and absence of AuNPs. Based on cyclic voltammetric experiments and Marcus Theory, a four-fold increase in the electron rate constant was observed in the presence of AuNPs, and the reorganization energy was estimated to be 0.49 eV. Furthermore, AuNPs decreased the effective distance between the redox center of Cyt c and the electrode surface by 20%. These results suggest that the electron transfer properties of Cyt c based protein electrodes are significantly enhanced in the presence of the AuNPs.

Electrochemical Behavior of Cytochrome C Immobilized in a Magnetically Induced Mesoporous Framework

“…Based on the faradaic current densities of oxidation curves for Cytc immobilized on Cyst modified polycrystalline gold electrode and into the ITO/Fe 3 O 4 −AuNPs/Cyst mesoporous framework, the calculated surface concentration ( Γ ) of redox‐active protein was 7.2×10 −11 mol cm −2 (or 8.9×10 −4 μg cm −2 ) and 3.4×10 −10 mol cm −2 (or 4.2×10 −3 μg cm −2 ), respectively. That latter presented a Γ value with an order of magnitude more than the value obtained when employed Au−NPs in self‐assembled electrode for mediate the electron transfer of Cytc …”

“…Since Film 3 exhibited the most relevant electrochemical behavior among all mesoporous framework‐like thin films, it was further employed to investigate the Cytc electron transfer after immobilization of this redox protein into their mesopores. For that, the Au−NPs which form the metallic coating onto the Fe 3 O 4 −NPs surface were modified with L‐cysteine (Cyst) molecules, in order to provide negatively charged active sites in neutral pH for an effective electrostatic immobilization of Cytc protein which possess positive surface charge . The effectiveness of Cytc immobilization was evaluated by measurements of UV‐Vis and FTIR spectroscopies.…”

“…The readily accumulation of Cytc into self‐assembled mesoporous films and its reversible reduction and oxidation have been previously reported . In addition, gold nanoparticles (Au−NPs) in the fabrication of self‐assembled electrode surfaces have been found as beneficial mediators for the electron transfer from Cytc . The presence of Au−NPs at the protein/electrode interface has a significant impact on the electrode microenvironment, and allows the optimization of catalytic process as well as electrochemical properties of redox protein …”

“…[10] In addition, gold nanoparticles (AuÀ NPs) in the fabrication of self-assembled electrode surfaces have been found as beneficial mediators for the electron transfer from Cytc. [15] The presence of AuÀ NPs at the protein/electrode interface has a significant impact on the electrode microenvironment, and allows the optimization of catalytic process as well as electrochemical properties of redox protein. [15] Electrochemical reactions, including bioelectrocatalytic and electrocatalytic processes, have been reversibly activated and inhibited upon physical translocation and reorientation of different magnetic micro/nano-species on the electrode surface, particularly using magnetic micro-and nanoparticles.…”

“…[15] The presence of AuÀ NPs at the protein/electrode interface has a significant impact on the electrode microenvironment, and allows the optimization of catalytic process as well as electrochemical properties of redox protein. [15] Electrochemical reactions, including bioelectrocatalytic and electrocatalytic processes, have been reversibly activated and inhibited upon physical translocation and reorientation of different magnetic micro/nano-species on the electrode surface, particularly using magnetic micro-and nanoparticles. [16] Recently, the magnetic-field-induced orientation of fructose dehydrogenase on iron oxide nanoparticles for enhanced direct electron transfer (DET) has been reported.…”