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

Abstract

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 Pb 2+ 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 Pb 2+ concentration range of 0.1-100 µM, and a detection limit of 11 nM. The sensor has been applied to the determination of Pb 2+ in an electroplating sludge reference material, the result agreeing with the certified value within 4.9%. Quantitative measurement of Pb 2+ 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.

Ion-Selective Electrodes for Detection of Lead (II) in Drinking Water: A Mini-Review

“…Compared to traditional inorganic reagents, the more complex biological molecules allow for reagents with greater selectivity and less interference. Sensors with enzymes that can detect ppb levels of lead, uranium, copper, mercury, zinc, and cadmium have been developed [17][18][19]. In particular, DNA-based sensors have gained increasing attention due to the fact that some metal ions selectively bind to some bases to form stable metal-mediated DNA duplexes [20,21].…”

Engineered 5S ribosomal RNAs displaying aptamers recognizing vascular endothelial growth factor and malachite green

“…Aptamers have been developed which bind small organic molecules (Hirao et al, 1997;Babendure et al, 2003;Sazani et al, 2004;Chu et al, 2006;Liu and Lu, 2006), proteins (Ruckman et al, 1998;Jayasena, 1999;Srisawat and Engelke, 2001; Lee et al, 2004), heavy metal ions (Chang et al, 2005;Swearingen et al, 2005;Wrzesinski and Ciesiolka, 2005;Stefan et al, 2006;Wernette et al, 2007) and even viruses (Gopinath et al, 2006a,b). Aptamers are best known as ligands to proteins, rivaling antibodies in both affinity and specificity (Jayasena, 1999), and aptamer-based therapeutics are now emerging (Ruckman et al, 1998).…”

Nanofluidic Devices and Their Potential Applications

“…For instance, applications included the delivery to the tip of an electrospray ionization-mass spectrometry (ESI-MS) device or a miniaturized lead sensor. 86,87 An improved design of preconcentration device was proposed by Han and coworkers from MIT, also taking advantage of the CP effect. 88 The layout and the concentration protocol are illustrated in Figure 5.11.…”