Ionic topochemical tuned biosensor interface.

Two new hydrophilic, poly(ethylene glycol) (PEG)-based redox copolymers bearing electrochemically active ferrocene (Fc) and thiol/disulfide anchoring functionalities were synthesized. These copolymers are shown to adsorb on gold surfaces causing polymeric self-assembled monolayers (pSAMs) that possess triple functions: "redox-active", "ionic-tunable", and "bio-inert". Both immobilized polymers showed redox potentials at +400 mV (Ag|AgCl), and facilitate the electrocatalytical oxidation of NADH. Additionally, interfacial architecture of the polymers is affected by an increase in Ca(2+) concentration, which leads to an amplification of the electrochemical response. The electrode current, measured for NADH-oxidation, increased by 80% after addition of 10 mM Ca(2+) ions. Considering the Ca(2+) influence on the heterogeneous electron transfer a structural model of the immobilized polymers is proposed based on the strong chelating ability of noncyclic PEG moieties.