Scanning Electrochemical Microscopy (SECM) study of DNA biosensors based on chitosan carbon nanotubes

S. BOLLO, N. F. FERREYRA, G. A. RIVAS

Edimburgo, Escocia

Congreso; 57th Annual Meeting of the International Society of Electrochemistry; 2006

International Society of Electrochemistry

The studies with DNA molecules are mainly devoted to study specific sequences or detection of DNA damage. In both cases the challenge for the analytical biosensor chemistry is to detect quantifiable differences between double strand DNA (dsDNA) and single strand DNA (ssDNA) or small variations in the signals that can correlates with a disruption of the DNA integrity. In this way the electrochemical DNA biosensors represent a rapid and sensitive alternative for these studies. On the other hand, SECM is a versatile technique for extracting electron-transfer kinetics information and/or studying biological systems. The technique demonstrates to be very useful for controlling the preparation and the characterization ofbiosensors and sensor structures, as well as the optirnization of their performance. The aim of this work was to apply SECM imaging to study of DNA biosensors based on chitosan and carbon nanotubes. A glassy carbon electrode was modified with chitosan or chitosan doped with carbon nanotubes previous to the adsorption ofDNA. The SECM feedback mode was selected to image each modified surfaces using ferrocene methanol in phosphate buffer pH 7.4 as redox mediator. It was found that chitosan modified GCE has a reduced electroactive surface compare with a bare GCE (black line voltammogram), producing a decrease from 1.25 to 0.15 in the SECM normalized current. When chitosan is doped with CNT (blue line voltammogram) the conductivity enhances respect to GCE-CHIT electrode, but never reach the bare GCE conductivity and the surface is more irregular . Nevertheless, for DNA adsorption. CHIT/CNT film was the most suitable to obtain reproducible and sensitive signal ofthe guanine oxidation.