title: Electrodes modified with nitrofluorenone derivatives as a basis for new biosensors.
abstract: We report about the electrocatalytic properties of electrodes modified by adsorption of nitro-fluorenone derivatives. The stable, adherent monolayer of these catalyst precursors can be transformed electrochemically into the corresponding hydroxylamine compounds (R-NO(2)+4e+4H(+)-->R-NHOH+H(2)O). The completely reversible two electron oxidation of the hydroxylamine leads to the nitroso compounds (R-NHOH-->R-NO+2e+2H(+)) that exhibit high catalytic activity in the electrooxidation of NADH at low overpotentials (-30 mV vs. Ag/AgCl) and therefore constitute a new family of efficient redox mediators for biosensor applications. A significant increase in catalytic activity (up to 500%) is observed after addition of calcium ions to the electrolyte. This is explained by a specific and bridging complexation between the coenzyme's phosphate groups and a carboxyl group present in the catalyst molecule. The interaction favours the contact between NADH and the surface confined catalyst, leading to a higher electron transfer efficiency. This interaction can be used in an approach of molecular level design for controlled monolayer deposition of catalyst, Ca(2+), NAD+ and enzyme. A very simple and inexpensive modification scheme, essentially based on electrostatic attraction, leads to electrodes that can be employed as reagentless biosensors for the electrochemical detection of common and commercially interesting analytes like glucose.
authors.affiliation: Laboratoire d'Analyse Chimique par Reconnaissance Moléculaire, Ecole Nationale Supérieure de Chimie et de Physique de Bordeaux, B.P. 108, 33402 Talence, France.
authors.forename: N
authors.initials: N
authors.lastname: Mano
authors.forename: A
authors.initials: A
authors.lastname: Kuhn
mesh_terms: D015374:Biosensing Techniques; D002118:Calcium; D004563:Electrochemistry; D004566:Electrodes; D004800:Enzymes, Immobilized; D005449:Fluorenes; D005947:Glucose / Q000032:analysis; D042843:Glucose 1-Dehydrogenase; D005948:Glucose Dehydrogenases; D009243:NAD; D009574:Nitro Compounds; D010084:Oxidation-Reduction
chemical_list: D004800:Enzymes, Immobilized; D005449:Fluorenes; D009574:Nitro Compounds; D009243:NAD; D005948:Glucose Dehydrogenases; D042843:Glucose 1-Dehydrogenase; D005947:Glucose; D002118:Calcium