Miniaturized Lead Sensor Based on Lead-Specific DNAzyme in a Nanocapillary Interconnected Microfluidic Device

• Published in: Environmental science & technology Vol. 39; no. 10; pp. 3756 - 3761
• Main Authors: Chang, In-Hyoung, Tulock, Joseph J, Liu, Juewen, Kim, Won-Suk, Cannon, Donald M, Lu, Yi, Bohn, Paul W, Sweedler, Jonathan V, Cropek, Donald M
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 15-05-2005
• Subjects: Analysis methods; Applied sciences; Biosensing Techniques - instrumentation; DNA, Catalytic; Drinking water and swimming-pool water. Desalination; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Environmental Monitoring - instrumentation; Environmental Monitoring - methods; Equipment Design; Exact sciences and technology; Industrial Waste - analysis; Lead; Lead - analysis; Microfluidics - instrumentation; Nanostructured materials; Nanostructures; Natural water pollution; Pollution; Pollution, environment geology; Scientific apparatus & instruments; Sensors; Sewage - analysis; Water Pollutants, Chemical - analysis; Water treatment and pollution; Drinking water; Enzyme; Laser induced fluorescence; Heavy metal; Hybrid system; Array; Surveillance; Fluorescent labelling; Biosensor; DNA; Detection limit; Water quality; Lead; Water pollution; Miniaturization; Measurement method; Microfluidics; Nanotechnology; Ground water
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es040505f

A miniaturized lead sensor has been developed by combining a lead-specific DNAzyme with a microfabricated device containing a network of microfluidic channels that are fluidically coupled via a nanocapillary array interconnect. A DNAzyme construct, selective for cleavage in the presence of Pb2+ and derivatized with fluorophore (quencher) at the 5‘ (3‘) end of the substrate and enzyme strands, respectively, forms a molecular beacon that is used as the recognition element. The nanocapillary array membrane interconnect is used to manipulate fluid flows and deliver the small-volume sample to the beacon in a spatially confined detection window where the DNAzyme is interrogated using laser-induced fluorescence detection. A transformed log plot of the fluorescent signal exhibits a linear response (r 2 = 0.982) over a Pb2+ concentration range of 0.1−100 μM, and a detection limit of 11 nM. The sensor has been applied to the determination of Pb2+ in an electroplating sludge reference material, the result agreeing with the certified value within 4.9%. Quantitative measurement of Pb2+ in this complex sample demonstrates the selectivity of this sensor scheme and points favorably to the application of such technologies to analysis of environmental samples. The unique combination of a DNAzyme with a microfluidic−nanofluidic hybrid device makes it possible to change the DNAzyme to select for other compounds of interest, and to incorporate multiple sensing systems within a single device for greater flexibility. This work represents the initial steps toward creation of a robust field sensor for lead in groundwater or drinking water.