ELETRODE MATERIALS CHEMICALLY MODIFIED: BIOLOGICAL SYSTEMS APPLICATIONS

FQ6

Marcela Di Mambro Rodrigues Gil¹ (IC), Edgar Toshiro Suzuki Yamamoto¹ (IC), Leandro Fontanetti do Nascimento² (PG), Fernando Grine Martins^1,3(PG), Alberto Federman Neto²(PQ), Zeki Naal¹ (PQ). zekinaal@usp.br

¹FCFRP-USP, Ribeirão Preto-SP; ²FFCLRP-USP,Ribeirão Preto-SP; ³IQ-UNICAMP, Campinas,SP.

Introduction: The immobilization of biological macromolecules (e.g.,proteins, enzymes, antibodies, receptor, peptides, DNA,etc.) on a transducer surface in a controlled manner that fully preserves their biological activity is one of the major challenges in making a functioning biosensor. Coupled to this area, the study of the electrochemical behavior of redox enzymes has received a great deal of attention, driven in many cases by the desire to construct practical, self-contained enzyme electrodes for biosensor applications. Closely related to such studies has been the use of various types of electroactive polymers employed in conjunction with redox enzymes for immobilization of the enzyme itself and for the acceleration of electron-transfer kinetics. In this way, modification of carbon surfaces is an important objective in electrochemistry and material science. More generally, active attention is currently paid to covalently modified electrodes for catalytic or analytical purposes and also in view of biotechnological applications. Covalent bonding (chemisorption) of the modifier to the carbon surface can be initiated via the direct electrochemical oxidation of amines, electrochemical reduction of aryl diazonium salts, or by gentle thermolysis or photolysis of the aryl diazonium salts. Alternatively, covalent bond formation can be activated by chemical means for example a Friedel-Crafts acylation on graphite and carbon nanotube recently studied in our laboratory. Another platform that we are exploring, is the electropolymerization of of N-(3-pyrrol-1-yl-propyl)-4,4’-bipyridinium (PPB).The interaction between the PPB layer and maltose binding protein fusion is through a nonquaternized pyridine nitrogen (in the PPB film). Objective: The aim of our laboratory is to obtain novels electrode materials to analyze and/or study molecules of interest in farmaceutical sciences, food, agriculture and biological systems as well. Materials and Methods: All electrochemical experiments were carried out with a BAS CV-27 potentiostat. Data were recorded on a SoltecXYrecorder. A three electrode conventional electrochemical cells were employed. A glassy carbon disk (area) 0.003 cm² or a gold disk (area) 0.006 cm² electrode was used as the working electrode. Prior to use, the electrode was polished with 1 mmdiamond paste (Buehler) and rinsed thoroughly with water and acetone. A sodium chloride saturated Ag/AgCl and a coiled Pt wire were used as reference and counter electrodes, respectively. The electrochemical behavior of Nimesulide (Nimes) and reduced nimes (NimesH) were carried out in PB pH 7 / 0.1 mol L^-1.Results and Discussion:. Electropolymerized films of PPB on glassy carbon electrodes retain their redox activity in aqueous solutions. Further modification with MBP-NR (nitroreductase) gave rise to electrodes that exhibited very high electroactivity for the reduction of trinitrotoluene TNT and dinitrotoluene DNT. However, PPB electrodes modified with wild type NR did not exhibit such activity.  Conclusion: Results from biosensor research suggest that the presence of specific interactions between the PPB layer and MBP fusions might represent a general way to immobilize enzymes onto surfaces with a high retention of activity. Electrochemical behavior of nimesulide in presence of NADH suggests that the oxidation reaction of NADH is made by nitrogroup in nimes. Graphite and carbon nanotube functionalized have applications in electronalysis that carbon paste electrode has not.