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A new 3-dimensional (3D) network of crosslinked Horseradish Peroxidase/Carbon Nanotube (HRP/CNT) on a thiol-modified Au surface has been described in order to build up the effective electrical wiring of the enzyme units with the electrode. The synthesized 3D HRP/CNT network has been characterized with cyclic voltammetry and amperometry which results the establishment of direct electron transfer between the redox active unit of HRP and the Au surface. Electrochemical measurements reveal that the high biological activity and stability is exhibited by the immobilized HRP and a quasi-reversible redox peak of the redox centre of HRP was observed at about −0.355 and −0.275 V vs . Ag/AgCl. The electron transfer rate constant, K S and electron transfer co-efficient α were found as 0.57 s −1 and 0.42, respectively. Excellent electrocatalytic activity for the reduction of H 2 O 2 was exhibited by the developed biosensor. The proposed biosensor modified with HRP/CNT 3D network displays a broader linear range and a lower detection limit for H 2 O 2 determination. The linear range is from 1.0 × 10 −7 to 1.2 × 10 −4 M with a detection limit of 2.2.0 × 10 −8 M at 3 σ . The Michaelies–Menten constant K app M value is estimated to be 0.19 mM. Moreover, this biosensor exhibits very high sensitivity, good reproducibility and long-time stability. [ABSTRACT FROM AUTHOR]

Abstract: A novel hydrogen peroxide biosensor has been designed based on the co-immobilization of hemoglobin (Hb), TiO2 nanotubes and methylene blue (MB) onto a glassy carbon (GC) electrode. The titania nanotube arrays were directly grown on a Ti substrate using anodic oxidation first; and then detached from the Ti substrate using ultrasonication. A pair of well-defined redox peaks of Hb, enhanced by MB, appeared at an applied potential around −0.425V, revealing that the immobilized Hb exhibits direct electrochemistry. Our electrochemical study shows that the immobilized Hb remains highly bioactive and displays excellent electrocatalytic response toward H2O2. The effect of pH and applied electrode potential in H2O2 sensing has been systemically studied. Besides the advantages of fast response and high stability, under the optimized conditions the linearity of the developed biosensor for the detection of H2O2 was observed from 2×10−7 to 1.6×10−4 M with a detection limit as low as 8×10−8 M (based on S/N =3). [Copyright &y& Elsevier]

Abstract: The formation of horseradish peroxidase-lipid Langmuir–Blodgett film and its applicability as a biosensor have been studied. HRP was spread directly onto the subphase covered with a layer of lipid in LB trough. Our experimental results showed that surface pressure of this film from liquid to solid state ranged between 15 to 25 mN/m. At surface pressure of 25 mN/m, the monolayer was successfully transferred onto the gold surface. In addition, electrochemical properties of this film showed that protein molecules still kept their natural structure and can give a well electrocatalytic activity to H2O2. As an H2O2 biosensor, this LB film was able to detect concentration of H2O2 which were 3×10−7 M. [Copyright &y& Elsevier]