Biorecognition platform based on electrodes modified with diazonium salts. Application to Concanavalin A immobilization

S. BOLLO; M. V. BRACAMONTE; G. A. RIVAS; N. F. FERREYRA

Santiago de Queretaro

Congreso; 28-64th Annual Meeting of the International Society of Electrochemistry; 2013

International Society of Electrochemistry

The immobilization of the biological molecules (nucleic acids, proteins, enzymes) is a crucial step in the development of electrochemical biosensors. The search for new ways of preparing perfect intermediary layer has attracted much attention. Among several strategies, the use of diazonium salt has been recently demonstrated. The procedure involves the formation of aryl radicals and its deposition by electro-reduction. The method offers a relatively simple way to modify surfaces with variety of functional groups (carboxyl, thiol, amines, nitrites, etc.). These functions can be used for chemical adsorption of biomolecules such as enzymes, DNA, antibodies and lectins, making the surfaces suitable for development of biosensors. In this work, we study the modification of gold (Au) and glassy carbon (GC) surfaces with SD derived from 4-aminobenzoic acid (PABA), 3-(4-aminophenyl) propionic acid (PAPA) and 4-(4-aminophenyl) butyric acid. Diazonium salts were obtained by reaction in situ of the arylamine with NaNO2 in acidic medium. The effect of arylamine and NaNO2 concentration and the reduction methodology (potentiodynamic and potentiostatic) were evaluated. Modified surfaces were characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in presence of different redox probes. The surface coverage of the arylamines, determined by analysis of charge and mass by electrochemical quartz crystal microbalance (EQCM), was compared. The surfaces modified under the selected conditions where used for the covalent immobilization of Concanavalin A (ConA) and the study of their interaction with α-D-glucose and α-D-manose. The adsorption of ConA was evaluated by surface plasmon resonance, CV and EIS. Conclusions: Under equivalent experimental conditions, GC surfaces are more reactive, producing structures of thickness higher than at gold. At both surfaces, the coverage obtained was higher than a monolayer, but each structures present holes or defects. The substituent chain length influences the surface coverage achieved. These values, determined from the change in frequency during the electro-grafting, were higher for 4-aminobenzoic acid (PABA) than 3-(4-aminophenyl) propionic acid (PAPA) and 4-(4-aminophenyl) butyric acid. The roughness of the DS layer favors adsorption of Con A, allowing to achieve coatings 4 times higher than the value of a compact monolayer of lectin. The adsorbed biomolecule retains its selective biorecognition ability to glucose.