Superóxido Dismutase em Eletrodo de Ouro Modificado com Poli(azo-Bismarck Y)/NTC Biossensor para a Determinação de Superóxido

An electrochemical superoxide biosensor was developed involving immobilization of superoxide dismutase (SOD) onto Au disc electrodes modified with poly(azo-Bismarck Y) (polyBBY) together with carbon nanotubes (CNT) in a chitosan dispersion in different compositions. The polyBBY film on the gold surface (0.02 cm2 ) was prepared by potential cycling between 0.00 and +1.10 V (vs. Ag/AgCl) at a scan rate of 100 mV s-1 for 50, 75 or 100 cycles, in a deaerated ethanolic solution containing 10 mmol L-1 BBY + 0.1 mol L-1 HCl. For CNT deposition, suspensions of 0.1% and 1% CNT were prepared in 1% (w/v) chitosan dissolved in 1% (v/v) acetic acid. The solutions were sonicated for 4 h and 2 L was applied by drop casting on the polyBBY/Au. For the preparation of biosensors, an enzyme solution containing 0.1% SOD and 2% BSA was mixed with a 2.5% GA solution (2:1) and 2 L applied onto the poly(BBY)/Au. Table 1 shows the amperometric response of all modified electrodes tested to successive additions of KO2 at an applied potential of -0.3 V vs Ag/AgCl in 0.1 mol L-1 NaPBS, pH 7.0. The sensor with a polymer film made by scanning for 50 cycles and coated with a suspension of 1% CNT presented the best electrochemical performance with a wide linear range (42 to 720 mol L-1), high sensitivity and fast response time (2 s).