Effects of 1-butyl-3-methylimidazolium tetrafluoroborate on the oxidation of glucose catalyzed by glucose oxidase

The effects of room temperature ionic liquids (ILs) on the conformation and electrocatalytic activity of enzymes were studied using glucose oxidase (GOx) and 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim]BF4) as models. UV–vis and circular dichroic (CD) spectra indicated that [bmim]BF4 did not affect the conformation of the enzyme, and the secondary structure of GOx in [bmim]BF4–PBS mixtures (the content of the IL is from 0 to 20 vol%) was essentially the same as that of the native one. The Raman spectra showed that no interaction existed between glucose and [bmim]BF4. The oxidation of glucose catalyzed by GOx was investigated under a substrate-saturated condition in [bmim]BF4–PBS mixtures using ferroceneacetic acid (FcA) as a mediator. The voltammetric results showed that electrocatalytic current (icat) decreased with the increase of the content of [bmim]BF4 in the mixtures. The reason causing the decrease of icat was analyzed. The reduction in the diffusion rate of FcA due to the increase of the viscosity after the addition of the IL was a key factor of causing the decrease of icat. The results presented here will be useful for the designing of the related biosensor used in ILs-containing system.