Facile glucose oxidase immobilization onto amino-functionalized multi-walled carbon nanotubes for glucose detection

Glucose detection is crucial in food processing, pharmaceuticals, and clinical diagnostics. To enhance the performance of glucose detection, enzyme immobilization has emerged as a key strategy that improves enzyme stability and reusability. Multi-walled carbon nanotubes (MWCNTs) have served to immobilize enzymes and fabricate electrochemical biosensors due to their physicochemical properties. Here, MWCNTs were aminofunctionalized through an effective and easy three-step chemical reaction (hydroxylation, chlorination, and amination). Then, glucose oxidase (GOx) was immobilized onto MWCNTs-NH2 modified glassy carbon electrode (GOx/MWCNTs-NH2/GCE) to construct an enzymatic glucose biosensor. The chemical, structural, and morphological characteristics of MWCNTs-NH2 were confirmed through various analytical techniques, including Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), energy-dispersive X-ray (EDX) spectroscopy, field emission scanning electron microscopy (FE-SEM), and atomic force microscopy (AFM). The electrochemical behavior of GOx/MWCNTs-NH2/GCE was examined using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV). CV voltammogram of GOx/MWCNTs-NH2/GCE shows redox peaks with formal potential (ES ') of-0.446 V related to immobilized GOx. Also, the kinetics parameters including electron transfer rate constants (ks) were determined as 5.94 s-1. Moreover, GOx/MWCNTs-NH2/GCE was used for glucose biosensing via the DPV method with the linear range 1.9-49.5 mu M along with the limit of detection (LOD) and sensitivity of 0.75 mu M and 1143 mu A mM-1 cm-2, respectively. In real samples of orange, apple, and pineapple fruit juices, glucose was measured as 2.30, 1.58 and 1.64 gL-1, respectively. This biosensor provides an appropriate platform for glucose determination and purpose MWCNTs-NH2 as a candidate to immobilize biological molecules.