Batch-Injection Amperometric Determination of Glucose Using a NiFe2O4/Carbon Nanotube Composite Enzymeless Sensor

Abstract

The development of sensitive and selective analytical devices for monitoring glucose levels (GLU) in biological fluids is extremely important for clinical diagnostics. In this work, we produced a new composite based on NiFe2O4 and multi-walled carbon nanotubes (MWCNT), called NiFe2O4@MWCNT, to be applied as a non-enzymatic amperometric sensor for GLU. Both NiFe2O4 and NiFe2O4@MWCNT composites were properly characterized by XRD, SEM, FTIR, and Raman spectroscopy, which confirmed that the composite was successfully prepared. A glassy-carbon electrode (GCE) modified with NiFe2O4@MWCNT was investigated by cyclic voltammetry and applied for the amperometric GLU detection using batch-injection analysis (BIA). A linear working range between 50 and 600 µmol L−1 GLU with a significant increase in sensitivity (3-fold) in comparison with MWCNT/GCE was verified, with a detection limit of 36 µmol L−1. Inter-electrode measurements (n = 4, RSD = 10%) indicated that the sensor fabrication is reproducible. Furthermore, the proposed non-enzymatic sensor was selective even in the presence of other biomarkers found in urine. When applied to synthetic urine samples, recovery levels between 84 and 95% confirmed analytical accuracy and the absence of sample matrix effect. Importantly, the developed approach is simple (free of biological modifiers), fast (77 injections per hour), and practical (high-performance tool), which are suitable features for routine analyses.