Abstract:

A hemoglobin/poly(L-glutamic acid)/glassy carbon electrode(Hb/PGA/GCE), targeted for reversible oxidation of p-phenylenediamine(PPD), has been fabricated by covalently immobilizing Hb on GCE with a thin layer of conductive preelectropolymerized PGA. Electrochemical impedance spectra of the electrode confirmed the immobilization of Hb. The resulting modified electrode(Hb/PGA/GCE) gave a redox couple for Hb in PBS buffer and a better electrocatalytic performance to H₂O₂. This indicated that the direct electron transfer of the active group of the protein could be retained on the electrode surface. The oxidation of PPD was reversible on Hb/PGA/GCE instead of GCE or PGA/GCE. The redox peak current was proportional to the scan rate, and I_p,a/I_p,c about 1.02, indicating a characteristic of quasi-reversible, surface confined electrochemical behavior. Moreover, a new measurement method for PPD in samples was provided since the redox peak currents increased linearly with the concentration of PPD, I_p,a(μA)=3.124+0.705c_PPD(mmol/L)(r=0.9973). The enzymatic oxidation might be the plausible mechanism because the existence of H₂O₂ was in favor of the reversible redox of PPD.

Key words: hemoglobin (Hb), poly (L-glutamic acid) (PGA), p-phenylenediamine (PPD), reversible oxidation