Synthesis of the multi-walled carbon nanotubes-COOH/graphene/gold nanoparticles nanocomposite for simple determination of Bilirubin in human blood serum

In this work, the multi-walled carbon nanotubes-COOH (MWCNTs-COOH)/graphene (GNs)/gold nanoparticles (AuNPs) composite materials were synthesized by in situ growth of AuNPs on the surface of the MWCNTs-COOH/GNs. And then, the Bilirubin oxidase (BUD) was immobilized on the surface of the film to construct a biosensor for determination of Bilirubin. Morphology of the nanomaterials was analyzed by field-emission scanning electron microscopy, high resolution transmission electron microscopy, Brunauer-Emmett-Teller, and X-ray photoelectron spectroscopy. The performance of the biosensor was studied by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and amperometric response (i-t). It was demonstrated that the nanocomposite materials exhibited enhanced fast electron transfer and excellent biocompatibility. In this assay, the MWCNTs-COOH/GNs/AuNPs composite film based biosensor showed prominently electrocatalytic activity for the detection of Bilirubin with a linear range from 1.33 μM to 71.56 μM and the low limit of detection (LOD) is 0.34 μM based on a signal to noise ratio (S/N = 3). Meanwhile, the apparent Michaelis-Menten constant (Km) was 64.86 μM. In addition, this biosensor exhibited satisfying reproducibility, stability, feasibility and fast responses. These results provide a novel way for exact detection of Bilirubin in biotechnology and clinical diagnosis, and broaden the application of graphene and carbon nanotubes in biomaterials.