Ni(II)-modified solid substrates as a platform to adsorb His-tag proteins

VALENTI, LAURA E.; MARTINS, VITOR L.; HERRERA, ELISA G.; TORRESI, ROBERTO M.; GIACOMELLI, CARLA E.

Journal of Materials Chemistry B

RCS Publishin

Año: 2013 vol. 1 p. 4921 - 4931

2050-7518

This work investigated a simple and versatile modification to a solid substrate to develop electrochemical bio-recognition platforms based on the bio-affinity interaction between histidine (His)-tagged proteins and Ni(II) surface sites. Carboxylate (COO)-functionalized substrates were prepared in multiple steps, initiated with an amino-terminated self assembled monolayer (SAM) on polycrystalline gold. Surface enhanced Raman spectroscopy (SERS), quartz crystal microbalance with dissipation monitoring (QCM-D) and contact angle measurements were used to follow the modification progress. Upon completion of the modification process, the surface COO-Ni(II) chelate complex and the coordination mode used to bind the His-tag proteins were characterized by X-ray absorption near-edge spectroscopy (XANES) at the Ni-K edge. Finally, the electrochemical stability and response of the modified substrates were evaluated by cyclic voltammetry (CV) in the presence of a redox mediator. The versatility of the modification process was verified using silica as the substrate, which only required the first modification step to be altered. QCM-D indicated that two types of films were formed: a COO-terminated SAM, which resulted from the reduction of previously incorporated surface aldehyde groups, and a physically adsorbed polymeric glutaraldehyde film, which was produced in the alkaline medium. XANES spectral features indicated that COO-Ni(II) formed a non-distorted octahedral complex on the substrate. The electrochemical stability and response towards the redox mediator of the COO-Ni(II)-terminated SAM indicated that this platform could be easily coupled to an electrochemical method to detect bio-recognition events. The polymeric glutaraldehyde film did not affect the surface properties (e.g., hydrophilicity), nor did the film interfere with the electrochemical response of the modified gold substrate.