Electrochemical sensors based on enzymes, biopolymers and nanoparticles

The work described in this Dissertation includes three research projects, designed to make a contribution to the field of electrochemical sensors and biosensors. The electrochemical, spectroscopic, and microscopic analyses were used to explain encountered phenomena. The first project (Chapter 3) describes a unique case of minimally destructive activation of carbon nanotubes (CNT) toward the electro-oxidation of dihydronicotinamide adenine dinucleotide (NADH). NADH is an important biomolecule because it acts as a co-factor of hundreds of dehydrogenase enzymes and a biomarker of metabolic disorders. The proof-of-concept experiments are also presented for the development of new reagentless biosensors based on the activated CNT and NAD+-dependent dehydrogenases. The second project (Chapter 4) is focused on the non-enzymatic direct determination of glucose at gold electrodes in physiologically relevant neutral buffer solutions. Electrochemical determination of glucose at the conventional gold disc electrodes is compared with that at electrodes based on gold nanoparticles and gold nanostructured films. In addition, the effects of the ionic composition of a solution on the electrochemical determination of glucose at gold surfaces are also documented. The third project (Chapter 5) probes the role of the direct electron transfer (DET) between the enzyme glucose oxidase and CNT in electrochemical biosensing of glucose. It shows that the proper understanding of the mechanistic aspects of biosensing is critically important to the progress in development of a new generation of electrochemical devices including the mediatorless electrochemical biosensors and DET-based biological fuel cells.