Optical fiber enzymatic biosensor for reagentless measurement of ethylene dibromide

A reagentless enzymatic optical biosensor has been constructed to measure the concentration of ethylene dibromide (EDB, 1,2-dibromoethane), a US EPA Priority Pollutant. This biosensor is based on the haloalkane dehalogenase DhaA, which generates protons as a product of the dehalogenation of EDB. The resulting pH change is detected as a shift in the fluorescence intensity of fluoresceinamine. When layers of fluoresceinamine and Rhodococcus sp. GJ70 expressing DhaA were immobilized on the tip of an optical fiber, the resulting changes in fluorescence were proportional to the EDB concentration in the range 1-10 mu g/L and nonlinear (saturation-type trend) for concentrations up to 10 mg/L. EDB concentrations as low as 1 mu g/L could be detected in aqueous solutions. Both the pH and buffer capacity of the sample had significant effects on the sensor's performance. EDB biosensors were active for at least 37 d, although their sensitivity decreased after 7 d. The biosensor's potential to measure continuously and in situ could make it useful for environmental or water treatment process monitoring systems.