title: Visual detection of lead(II) using a label-free DNA-based sensor and its immobilization within a monolithic hydrogel.
abstract: Lead is highly toxic and its detection has attracted a lot of research interests. In recent years, DNA has been used for Pb(2+) recognition and many fluorescent sensors with low to sub-nM detection limits have been reported. These figures of merit were typically measured using a spectrophotometer that can detect nM DNA with a high signal-to-noise ratio. For visual detection, however, μM DNA or dye was required, making it difficult to detect low nM targets. We recently achieved a visual sensitivity of 10 nM Hg(2+) by immobilizing a DNA probe in a hydrogel. This was made possible because the gel was able to actively adsorb Hg(2+). In this work, we aim to test whether this method can be extended to the detection of Pb(2+). First, a new Pb(2+) sensor was designed based on a guanine-rich DNA and DNA binding dyes such as thiazole orange and SYBR Green I. The free DNA showed a detection limit of 8 nM Pb(2+) using 40 nM DNA. For visual detection in solution with 1 μM of the DNA probe, however, ∼300 nM Pb(2+) was required. After immobilization in a monolithic polyacrylamide hydrogel, even 20 nM Pb(2+) could be visually detected with a sample volume of 50 mL. Therefore, sensitive detection without signal amplification was achieved. Finally, we demonstrated simultaneous detection of both Hg(2+) and Pb(2+) in the same water sample with shape encoded hydrogel sensors.
authors.affiliation: Department of Chemistry, Waterloo Institute for Nanotechnology, University of Waterloo Waterloo, Ontario, Canada N2L 3G1.
authors.forename: Zachary E
authors.initials: ZE
authors.lastname: Jacobi
authors.forename: Lu
authors.initials: L
authors.lastname: Li
authors.forename: Juewen
authors.initials: J
authors.lastname: Liu
mesh_terms: D020106:Acrylamide / Q000737:chemistry; D001483:Base Sequence; D015374:Biosensing Techniques; D004247:DNA / Q000737:chemistry*; D015342:DNA Probes; D020100:Hydrogels; D007854:Lead / Q000032:analysis*; D057230:Limit of Detection
chemical_list: D015342:DNA Probes; D020100:Hydrogels; D020106:Acrylamide; D007854:Lead; D004247:DNA