title: Immobilization of DNA on magnetic microparticles for mercury enrichment and detection with flow cytometry.
abstract: Mercury detection in water has attracted a lot of research interest due to its highly toxic nature and adverse environmental impact. In particular, the recent discovery of specific binding of Hg(II) to thymine-rich (T-rich) DNA resulting in T-Hg(II)-T base pairs has led to the development of a number of sensors with different signaling mechanisms. However, the majority of such sensors were non-immobilized. Immobilization, on the other hand, allows active mercury adsorption, signal amplification, and sensor regeneration. In this work, we immobilized a thymine-rich DNA on a magnetic microparticle (MMP) surface through biotin-streptavidin interactions. In the presence of Hg(II), the DNA changes from a random coil structure into a hairpin, upon which SYBR Green I binds to emit green fluorescence. Detection was carried out by using flow cytometry where the fluorescence intensity increased ≈9-fold in the presence of mercury and the binding of mercury reached equilibrium in less than 2 min. The sensor showed a unique sample-volume-dependent fluorescence signal change where a higher fluorescence was obtained with a larger sample volume, suggesting that the particles can actively adsorb Hg(II). Detection limits of 5 nM (1 ppb) and 14 nM (2.8 ppb) were achieved in pure buffer and in mercury-spiked Lake Ontario water samples, respectively.
authors: Department of Chemistry, Waterloo Institute for Nanotechnology, University of Waterloo, 200 University Avenue West, Waterloo, ON, N2L 3G1 Canada.
authors: Po-Jung Jimmy
authors: PJ
authors: Huang
authors: Juewen
authors: J
authors: Liu
mesh_terms: D001483:Base Sequence; D004247:DNA / Q000737:chemistry*; D005434:Flow Cytometry; D005453:Fluorescence; D008280:Magnetics; D008628:Mercury / Q000032:analysis* / Q000737:chemistry
chemical_list: D004247:DNA; D008628:Mercury