Experimental Platform to Study Heavy Metal Ion−Enzyme Interactions and Amperometric Inhibitive Assay of Ag + Based on Solution State and Immobilized Glucose Oxidase

The heavy metal (HM) ion−enzyme interaction is an important research topic in many areas. Using glucose oxidase (GOx) as an example, a comprehensive experimental platform based on quartz crystal microbalance and electroanalysis techniques is developed here to quantitatively study the HM ion−enzyme interactions and amperometric inhibitive assays of HM ions. The effects of some common HM ions on the bioactivities of solution-state GOx (GOxs), electrode surface-adsorbed GOx (GOxads), and polymer-entrapped GOx (GOxe) are comparatively examined on the basis of anodic amperometric detection of enzymatically generated H2O2. Ag+ shows the strongest inhibition effect among the HM ions examined, and the inhibitive assays of Ag+ based on GOxs, GOxads, and GOxe entrapped in poly(l-noradrenalin) (PNA) give limits of detection (LOD) of 2.0, 8.0, and 5.0 nM (S/N = 3), respectively. Inhibition effects of Hg2+, Cu2+, and Co2+ are detectable only at 15 μM or higher concentrations, and the other HM ions show undetectable in...