Fiber-Optic Biosensor for the Detection of Atrazine: Characterization and Continuous Measurements

Abstract

An optical fiber enzymatic biosensor was formed by immobilizing cells containing atrazine chlorohydrolase to the surface of a pH-sensitive optode. This enzyme catalyzes the dechlorination of atrazine, releasing hydrochloric acid and creating a signal response from the optode that was proportional to the atrazine concentration. Biosensors capable of quantitative and sensitive atrazine concentration measurements were developed using the atrazine chlorohydrolase of both Pseudomonas sp. ADP and Clavibacter michiganese sp. ATZ1. The biosensors based on both bacteria had a limit of detection of less than 1 ppb (validated using gas chromatography) and a linear range from 1 ppb to 100 ppb atrazine. Response times were a function of concentration and the source of enzyme, with a response time of 10 or 20 min for a 25 ppb atrazine solution. The performance of these sensors at various temperatures, pH values, and buffer capacities was also studied. The use of poly-L-lysine to increase the physical stability of biosensors containing Pseudomonas sp. ADP provided higher durability with no performance drawbacks. The atrazine biosensor was also used to measure atrazine concentrations in a soil column that was continuously fed a solution in which the atrazine concentration was increased or decreased. The atrazine biosensor provided continuous, in-situ measurements in the soil column, the first time that continuous biosensor measurements have been demonstrated in a soil system.

Keywords:

• Atrazine
• Environmental monitoring
• Enzymatic biosensor

Acknowledgments

This paper was submitted as part of a Special Issue on Biosensors organized by Dr. Yu Lei of the University of Connecticut.

The authors are grateful for financial support for this research from the Colorado Institute for Research in Biotechnology and from the Colorado Agricultural Experiment Station (project COL00643). We also thank Dr. Lawrence P. Wackett for generously supplying Pseudomonas sp. strain ADP and Clavibacter michiganese ATZ1.

Notes

^a 90% of response to 25 ppb atrazine.

^b standard deviation based on three measurements.