Colorimetric method for glucose detection with enhanced signal intensity using ZnFe2O4–carbon nanotube–glucose oxidase composite material

Abstract

In this paper, a composite material comprised of ZnFe₂O₄ nanomaterial, carbon nanotubes (CNT) and glucose oxidase (GOD) was synthesized and used for glucose detection. ZnFe₂O₄–CNT was formed by a one-step solvothermal approach using acid-treated CNT as precursor, then GOD was linked to it by coupling reaction between –NH₂ and –COOH. After addition of glucose, which is oxidized by GOD, the intermediate product (H₂O₂) further oxidizes the 3,3′,5,5′-tetramethylbenzidine (TMB) substrate and forms a blue product. This process was accelerated in the presence of peroxidase-mimic ZnFe₂O₄ nanomaterial and the detected signal intensity was correspondingly enhanced. The linear detection range of glucose was 0.8 to 250 μM, with a limit of detection of 0.58 μM. This may originate from (1) the limited diffusion of intermediate species, which resulted in enhanced local concentrations of reaction compounds; (2) enhanced electron transmission among CNT, GOD and ZnFe₂O₄; (3) the synergistic enhancement of catalytic activity of ZnFe₂O₄ compared with other metal oxides; (4) the high loading capacity of ZnFe₂O₄–CNT for GOD molecules, because of its high surface-to-volume ratio. Meanwhile, this method has reasonable selectivity, stability and reusability and can be used for real serum detection, which may be useful for the development of sensitive biosensors.