Sol-gel derived urease-based optical biosensor for the rapid determination of heavy metals

A urease optical biosensor for the determination of heavy metals based on sol-gel immobilization technique was developed. A fluorescent dye, FITC-dextran, was encapsulated and parameters including optical properties of the probe, relative enzyme activity, initial pH value and the buffer concentration for substrate preparation were investigated. In sol-gel immobilization, 1 mM Tris-HCl at pH 7.1 provided a sufficient buffer capacity for metal ion analysis as well as the enzyme activity maintenance. Also, two analytical procedures, incubated and un-incubated systems, were compared to understand the sensitivity and applicability to heavy metal analysis. The developed optical biosensor showed high reproducibility and the relative standard deviation (R.S.D.) of 5.1% (n = 10) was obtained. Also, eight measurements can be completed automatically within 36 min. The biosensor has high sensitivity to Cu(II) and Cd(II) and an analytical range of 10-230 muM with a detection limit of 10 muM was achieved. Moreover, biological and environmental samples were examined to evaluate the applicability of the developed biosensor. A 19-82% of inhibition was observed when 20-45 muM metal ions were amended into tested samples, revealing that the developed system has the potential for the determination of heavy metals in real samples. (C) 2003 Elsevier Science B.V. All rights reserved.