An amperometric biosensor based on horseradish peroxidase immobilized onto maize tassel-multi-walled carbon nanotubes modified glassy carbon electrode for determination of heavy metal ions in aqueous solution

• Horseradish peroxidase was successfully immobilized into maize tassel-multiwalled composite.
• The FTIR and UV–vis results inferred that HRP was not denatured during its immobilization.
• Inhibition was observed for both Pb2+ and Cu2+.
• The inhibition was reversible and mixed for both metal ions studied.

A biosensor for trace metal ions based on horseradish peroxidase (HRP) immobilized on maize tassel-multiwalled carbon nanotube (MT-MWCNT) through electrostatic interactions is described herein. The biosensor was characterized using Fourier transform infrared (FTIR), UV–vis spectrometry, voltammetric and amperometric methods. The FTIR and UV–vis results inferred that HRP was not denatured during its immobilization on MT-MWCNT composite. The biosensing principle was based on the determination of the cathodic responses of the immobilized HRP to H2O2, before and after incubation in trace metal standard solutions. Under optimum conditions, the inhibition rates of trace metals were proportional to their concentrations in the range of 0.092–0.55 mg L−1, 0.068–2 mg L−1 for Pb2+ and Cu2+ respectively. The limits of detection were 2.5 μg L−1 for Pb2+ and 4.2 μg L−1 for Cu2+. Representative Dixon and Cornish-Bowden plots were used to deduce the mode of inhibition induced by the trace metal ions. The inhibition was reversible and mixed for both metal ions. Furthermore, the biosensor showed good stability, selectivity, repeatability and reproducibility.

The stepwise amperometric biosensor fabrication process and immobilized horseradish peroxidase inhibition in metal ion solution.Figure optionsDownload as PowerPoint slide