Mass Transfer in Amperometric Biosensors Based on Nanocomposite Thin Films of Redox Polymers and Oxidoreductases

Abstract

Mass transfer in nanocomposite hydrogel thin films consisting of alternating layers of an organometallic redox polymer (RP) and oxidoreductase enzymes was investigated. Multilayer nanostructures were fabricated on gold surfaces by the deposition of an anionic self-assembled monolayer of 11-mercaptoundecanoic acid, followed by the electrostatic binding of a cationic redox polymer, poly[vinylpyridine Os(bis-bipyridine) 2 Clco-allylamine], and an anionic oxidoreductase. Surface plasmon resonance spectroscopy, Fourier transform infrared external reflection spectroscopy (FTIR-ERS), ellipsometry and electrochemistry were employed to characterize the assembly of these nanocomposite films. Simultaneous SPR/electrochemistry enabled real time observation of the assembly of sensing components, changes in film structure with electrode potential, and the immediate, in situ electrochemical verification of substrate-dependent current upon the addition of enzyme to the multilayer structure. SPR and FTIR-ERS studies also showed no desorption of polymer or enzyme from the nanocomposite structure when stored in aqueous environment occurred over the period of three weeks, suggesting that decreasing in substrate sensitivity were due to loss of enzymatic activity rather than loss of film compounds from the nanostructure.

Swelling of electrochemically active polyelectrolyte multilayers

“…cytochrome C [91,96], myoglobin [97,98]) or try to mimic biological signal chains by the assembly of protein stacks [99][100][101]. Although many measurements involving these systems are conducted using pure electrochemical methods often optical techniques, such as surface plasmon resonance spectroscopy are used as complementary methods [98,102]. These measurements are usually aimed at monitoring mass changes upon binding events.…”

Immunosensor interface based on physical and chemical immunoglobulin G adsorption onto mixed self-assembled monolayers

“…On the other hand, the physical adsorption of hIgG observed on the COOH-terminated SAM and on the mixed SAM with 50% of 11-mercaptoundecanoic acid, is very likely the consequence of electrostatic interactions between hIgG and most probably charged SAMs. According to the literature, it is expected that surface COOH, with a pK a of about 6.5 [37] is, at least, partially deprotonated at pH 7.4. At this pH it is possible that hIgG can adsorb electrostatically to the SAM, since the value is close to its reported pI (between 5.0 and 8.0) [38].…”

Design considerations in the use of interdigitated microsensor electrode arrays (IMEs) for impedimetric characterization of biomimetic hydrogels

“…The use of hydrogels for immobilization of biomolecules on IMEs is an ideal approach to develop highly sensitive impedimetric biosensors and biochips. Although there are multiple reports involving hydrogels that document their biocompatibility (Luo et al 2000), biodegradability (Metters et al 2000), bioadhesion (Peppas and Sahlin 1996), dielectric relaxation (Kyritsis et al 1995), and mass transport properties in various settings (Pishko et al 2002), impedimetric characterization of hydrogel-coatings on IMEs are rarely reported (Sheppard et al 1995). Of particular interest in this study is the effect of geometry (line and space) on the impedimetric responses of bioactive hydrogel layers.…”