Unraveling Surface Properties of Cytochrome c@Au Nanoparticle Bionanoprobes

Keywords:
gold nanoparticle, cytochrome, nanobioprobe, DLS, zeta potential, CD, AFM

Abstract:
Bionanoprobes were created using cytochromes c isolated from horse heart (HCc) or yeast (YCc); and citrate-stabilized AuNPs. The two cytochromes c generated bionanoprobes with remarkably distinct surface properties. The combination of spectrophotometric pH-titrations and circular dichroism spectroscopy provided information on the protein layer of the bionanoprobes, revealing distinct protonation patterns for the two systems as reflected by its pH-induced aggregation. The YCc bionanoprobe revealed changes in the secondary structure of its protein layer that were practically absent in the protein layer of the HCc bionanoprobes. Atomic force microscopy and dynamic light scattering and determination of -potencial, provided insights on the layer structure and surface coverage and potential. These techniques confirmed a thick protein layer for the YCc bionanoprobe of ca. 4 nm whereas the HCc bionanoprobe presented a protein layer with ca. 2 nm that can be removed by sample drying. The surface potential of both bionanoprobes was nevertheless similar, although largely different from either proteins or AuNPs alone. The data obtained corroborates the proposed differential protein binding to the AuNPs of both cytochromes c, either by electrostatic adsorption (HCc) or by the formation of a quasi-covalent bond between the AuNPs and the Cys 102 residue of YCc.

Nanotech 2008 Conference Program Abstract