Barbara Kowalewska

Toward more efficient bioelectrocatalytic oxidation of ethanol for amperometric sensing and biofuel cell technology.

The integrated, structured, and multifunctional bioelectrocatalytic system for effective oxidation of ethanol is developed here. The concept is based on the layer-by-layer (LbL) assembly through electrostatic attraction of positively charged, multiwalled carbon nanotubes and the controlled combination of dehydrogenase enzymes. More specifically, the LbL technique was employed for sequential immobilization of two dehydrogenase enzymes and poly(diallyldimethylammonium chloride)-covered multiwalled carbon nanotubes onto a glassy carbon electrode substrate. Both monoenzymatic [utilizing a single enzyme, alcohol dehydrogenase (ADH)] and bienzymatic (anchoring sequentially both ADH and aldehyde dehydrogenase) systems were tested. Multilayers were characterized using scanning electron microscopy, infrared spectroscopy, and cyclic voltammetry. The results are consistent with the view that our approach enables good control of distribution and efficient utilization of both enzymes within the biocomposite film and leads to sizable enhancement of the oxidation of ethanol through significant (more than 2-fold) increase of bioelectrocatalytic currents and by shifting the ethanol oxidation potential to 0.1 V (vs Ag/AgCl) or decreasing the overvoltage by ca. 200 mV in comparison with the monoenzymatic electrode system. This simple biocomposite (enzyme-cascade) system permits fabrication of highly sensitive ethanol biosensors based on nicotinamide adenine dinucleotide coenzyme-dependent dehydrogenases. Our ethanol biosensor exhibited a good linearity ranging from 50 to 300 μM, and it was characterized by a high sensitivity of 118.8 μA mM(-1) cm(-2) as well as a low detection limit of 24 μM.

Dioxygen insensitive C70/AuNPs hybrid system for rapid and quantitative glucose biosensing

A novel hybrid system based on NAD-dependent glucose dehydrogenase immobilized on gold nanoparticles (AuNPs) covered with C70 fullerene has been developed for effective biosensing and quantitative detection of glucose. According to amperometric measurements, the new biosensor exhibited high sensitivity (26.1 μA mM−1 cm−2), wide linear range (0.25–12.0 mM), and rapid characteristic response (3 s). These unique properties suggest that the prepared hybrid nanocomposite is very promising to find potential application as a dioxygen insensitive biosensor for rapid and quantitative detection of glucose.

Enhancement of Bioelectrocatalytic Oxidation of Glucose by Application of Tetrathiafulvalene Modified Carbon Nanotubes as Mediating System

Combination of tetrathiafulvalene (TTF)-modified multi-walled carbon nanotubes and glucose oxidase within the film produces a bio-electrocatalytic system capable of effective oxidation of glucose in 0.1 mol dm phosphate buffer (pH=7.0). An important function of carbon nanotubes is to improve transport of electrons within the film. Here carbon nanotubes have been modified with ultra-thin layers of TTF to form stable colloidal suspensions of carbon nanostructures. They have been utilized to produce Nafioncontaining inks for sequential deposition of components. The presence of TTF is expected to facilitate an effective flow of electrons from the redox centers of glucose oxidase to the glassy carbon electrode. TTF constitutes a group of redox molecules that were successfully used as redox mediators in enzyme electrochemistry. Our highly porous film of carbon nanotubes on the electrode surface have presumably acted as three-dimensional network of nanowires around the enzyme molecules and have promoted the efficient electron transfers.