New peroxidase-substrate 3,5-di-tert-butylcatechol for colorimetric determination of blood glucose in presence of Prussian Blue-modified iron oxide nanoparticles

Prussian Blue-modified iron oxide (PB-Fe2O3) nanoparticles (NPs) have been demonstrated to exhibit peroxidase-like activity through catalytic oxidation of the peroxidase substrate 3,5-di-tert-butylcatechol (3,5-DTBC) in the presence of H2O2, producing a yellow-colored solution. Kinetic analysis of the data indicates typical Michaelis–Menten catalytic behavior. On the basis of the catalyzed color reaction, we have developed a simple, cheap, highly sensitive and selective colorimetric method for the detection and estimation of glucose in phosphate buffer solution of pH 7.0. 3,5-DTBC has been to be a better reagent for the estimation of glucose compared with common peroxidase substrate 3,3′,5,5′-tetramethylbenzidine (TMB) in that a phosphate buffer solution of pH 7.0 is optimum for the performance of glucose oxidase (GOx) activity as well as oxidation of 3,5-DTBC by the liberated hydrogen peroxide in a single step. Using PB-Fe2O3 NPs and 3,5-DTBC/glucose–GOx system, glucose can be estimated in the linear range 1–80 μM with a detection limit of 0.16 μM. Based on this single-step reaction, human blood glucose level can be monitored conveniently.