Immobilization of hemoglobin on functionalized multi-walled carbon nanotubes-poly-L-histidine-zinc oxide nanocomposites toward the detection of bromate and H2O2

Abstract

A novel biocompatible sensing strategy has been developed based on functionalized multi-walled carbon nanotube (f-MWCNT), poly-L-histine (P-L-His), and ZnO nanocomposite film for the immobilization of hemoglobin (Hb). The direct electron transfer properties and bioelectrocatalytic activity of the Hb in f-MWCNT-P-L-His-ZnO composite film is further investigated. The apparent heterogeneous electron transfer rate constant (k(s)) of Hb confined tof-MWCNT P L His ZnO nanocomposite is found to be 5.16 s(-1) using Laviron's equation. Moreover, the surface coverage concentration (Gamma) of the electroactive Hb in the f-MWCNT-P-L-His-ZnO film is estimated to be 1.88 x 10(-9) Mol Cm-2. The fabricated electrochemical biosensor based on the immobilized Hb revealed a fast response time (<3 s) with a wide linear range (4-18,000 mu M and 2-15,000 mu M) and detection limit (as low as 0.01 mu M and 0.30 mu M) for the electrocatalytic determination of a mediator-free H202 and bromate under optimal experimental conditions. The ca. apparent Michaelis-Menten constant is 0.14 mM, which indicates that the Hb has a high affinity to H2O2. The high sensitivity, good reproducibility, and long-term stability of the proposed nanocomposite film indicates that it can serve as an electrode for the development of an amperometric H2O2 and bromate-based biosensor. The proposed third-generation biosensor was successfully applied to milk and urine samples for the detection of H2O2 and bromate. (C) 2015 Elsevier B.V. All rights reserved.