Horseradish peroxidase biosensor based on maize tassel–MWCNTs composite for cadmium detection

The present work is focused on the application of a hydrogen peroxide (H2O2) biosensor for the detection of heavy metals ions. The biosensor was constructed by physical adsorption of horseradish peroxidase (HRP) onto a maize tassel (MT)-multiwalled carbon nanotube (MWCNT) composite and was characterized using spectroscopic and voltammetric methods. 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. Using Cd2+ as a model metal ion, the inhibition rate of the trace metal was proportional to concentration in the range of 2–30 μg L−1 with a limit of detection of 0.51 μg L−1. Representative Dixon and Cornish-Bowden plots showed that the reaction was non-competitive. The developed biosensor exhibited good stability, repeatability and reproducibility, thus providing a new promising tool for analysis of enzyme inhibitors.