Comparison of Microcontact-Printed and Solution-Adsorbed Cytochrome c Films on Indium Tin Oxide Electrodes

Abstract

Three different methods for preparing cytochrome c (cyt c) films on planar indium tin oxide (ITO) electrodes have been characterized and compared using electrochemical and surface spectroscopy methods. Protein films formed by adsorption of dissolved cyt c and by microcontact printing with both hydrophobic and hydrophilic poly(dimethylsiloxane) (PDMS) stamps are compared in terms of the total and electrochemical surface coverage, standard reduction potential, and rate of direct electron transfer with the ITO surface. Plasma treatment of the PDMS stamps, which renders them hydrophilic, dramatically increases the surface coverage of printed films to a level comparable to that of films formed by adsorption of dissolved cyt c. Their electrochemical properties are also very similar. This work is the first report of the direct electrochemical activity in a metalloprotein film formed by microcontact printing on an electrode surface.

Determination of Anisotropic Optical Constants and Surface Coverage of Molecular Films Using Polarized Visible ATR Spectroscopy. Application to Adsorbed Cytochrome c Films

“…The electroactive surface coverage is only 9.5 pmol/cm 2 , slightly less than a half monolayer, 18 which shows that less than half of the protein molecules adsorbed on the electrode surface can be directly oxidized or reduced. This could be due to the heterogeneous surface of ITO, 29 which has some insulating regions.…”

“…18,28 Ten micromolar solutions of ferricytochrome c in 10 mM phosphate buffer (pH 7) were used to prepare all protein films. Deionized (DI) water (18 MΩ) was obtained from a Barnstead Nanopure apparatus and was used throughout.…”

Modification of Transparent Conducting Oxide ( TCO ) Electrodes through Silanization and Chemisorption of Small Molecules

“…Above a certain scan rate, the conformational change can be overcome. More recently, Runge and Saavedra showed that cyt C forms a sufficiently stable adsorbed state such that it can be microcontact printed on ITO surfaces, while retaining high electron transfer rates [84]. …”

Gold nanoparticle-attached ITO as a biocompatible matrix for myoglobin immobilization: direct electrochemistry and catalysis to hydrogen peroxide

“…The direct electrochemistry of heme proteins such as cytochrome c and Mb in solution has been successfully observed at bare ITO electrodes [14][15][16][17], which also implies that ITO is an excellent substrate for heme protein immobilization. However, previous work concerning the immobilization of electroactive proteins on ITO has focused on cytochrome c [18][19][20][21]. Although, there is one report mentioning the Mb film on an ITO surface, it was stated that Mb needed to be thoroughly purified and freed from any surface-active impurities in order to observe the electrochemical response [22].…”