Here Pt/PANI:PESA was reduced for 15 min in 1 mL they 0.1 M phosphate buffer pH 6.5 at a constant potential of -500 mV. Then the Pt/PANI:PESA electrode was placed in a cell containing 100 ��L HRP solution (10 mg/mL HRP, 3 mg BSA) and 900 ��L 0.1 M phosphate buffer pH 6.5 and oxidized for 20 min at a potential of +650 mV. During Inhibitors,Modulators,Libraries the oxidation process HRP was electrostatically attached to the nanocomposite layer [14,15] to form Pt/PANI:PESA/HRP biosensor. The bioelectrode was then rinsed with distilled water Inhibitors,Modulators,Libraries to remove unattached enzymes. To select the optimum pH for operating the biosensor, five 1 mM H2O2 solutions were prepared with 0.1 M phosphate buffer solutions of pH 4, 6.5, 7, 8 and 10. The CV and SWV responses of the biosensor at the five pH’s were determined using 3 mL of the H2O2 solutions.

Maximum response of the biosensor was obtained with 0.1 M phosphate buffer at pH 6.5. All biosensor experiments were then performed at pH 6.5.2.4. Biosensor ResponseCyclic and square wave voltammetric responses of the biosensor were recorded by successively adding 3 ��L aliquots of 1 mM H2O2 to a 1 mL cell solution containing Inhibitors,Modulators,Libraries 0.1 M phosphate buffer at pH 6.5. The long term Inhibitors,Modulators,Libraries stability of the bioelectrode was investigated by evaluating the changes in the biosensor response to H2O2 with time. In this case freshly prepared biosensor was placed in an electrochemical cell containing 3 mL of phosphate buffer and aliquots of 3 ��L of 1 mM H2O2 were added successively under argon atmosphere in a stirred solution at 21 �� 2 ��C. The bioelectrode was stored in phosphate buffer at 4 ��C when not in use.

The experiment was repeated with the same electrode every 36 h.3.?Results and Discussion3.1. Characterization of PANI:PESA CompositeThe loading of the nanocomposite on the electrode surface was gravimetrically determined and it was found that Cilengitide ~3.3 mg of the PANI:PESA composite material was deposited on the electrode surface. Figure 1(A) shows the low scan-rate CV’s of PANI:PESA in 1 M HCl. The CV shows tow main redox couples at a scan rate of 2 mV/s, corresponding to leucoemeraldine/leucoemeraldine radical cation (200 mV/350 mV) and pernigraniline/pernigraniline radical action (600 mV/470 mV) transitions [7,11,16]. However, as the scan rate increases the fully reduced and oxidised forms of the polymer, leucoemeraldine (200 mV) and pernigraniline (600 mV), become more prominent.

This shows that the formation of the Erlotinib radical cations are slow electron transfer processes. In buffer medium (Figure 2B) only the electrochemistry of the leucoemeraldine/leucoemeraldine radical cation (10 mV/100 mV) redox couple was observed. This behaviour of the composite electrode in buffer medium indicates that strong acidic conditions are required for the oxidation of the PANI composite to the pernigraniline form.