Carbon nanotube-hydroxyapatite-hemoglobin nanocomposites with high bioelectrocatalytic activity

In this paper, carbon nanotubes-hydroxyapatite (MWCNTs-HA) composite were synthesized by self-assembling technique, and investigated by X-ray diffraction, scanning electron microscopy (SEM) and FT-IR spectroscopy. Hemoglobin (Hb) immobilized in MWCNTs-HA film not only retained its similarly native conformations, but also achieved the direct electron transfer. The apparent heterogeneous electron transfer rate constant (k(s)) was evaluated as (5.05 +/- 0.41) s(-1) according to Laviron's equation, and the surface coverage (Gamma*) was estimated as (9.25 +/- 0.69) x 10(-10) mol cm(-2). Moreover, the Hb immobilized in MWCNTs-HA film exhibited remarkable bioelectrocatalytic activity for the electrochemical reduction of H2O2. The amperometric response of the biosensor varied linearly with the H2O2 concentration ranging from 0.5 mu M to 2 mu M, and the results showed a detection limit of 0.09 mu M. Furthermore, the Hb-immobilized MWCNTs-HA film exhibited the excellent catalytic reactivity toward trichloroacetic acid (TCA). (C) 2009 Elsevier B.V. All rights reserved.