title: DNA Adsorption by ZnO Nanoparticles near Its Solubility Limit: Implications for DNA Fluorescence Quenching and DNAzyme Activity Assays.
abstract: Zinc oxide (ZnO) is a highly important material, and Zn(2+) is a key metal ion in biology. ZnO and Zn(2+) interconvert via dissolution and hydrolysis/condensation. In this work, we explore their interactions with DNA, which is important for biointerface, analytical, and bioinorganic chemistry. Fluorescently labeled DNA oligonucleotides were adsorbed by a low concentration (around 5 μg/mL) of ZnO nanoparticles, near the solubility limit. Right after mixing, fluorescence quenching occurred, indicating DNA adsorption. Then, fluorescence recovered, attributable to ZnO dissolution. The dissolution rate followed A5 > T5 > C5. Dissolution was slower with longer DNA. The adsorption affinity was also measured by a displacement assay to be G5 > C5 > T5 > A5, suggesting that tightly adsorbed DNA can retard ZnO dissolution. Electrostatic interactions are important for DNA adsorption because ZnO is positively charged at neutral pH, and a high salt concentration inhibits DNA adsorption. Next, in situ formation of ZnO from Zn(2+) was studied. First, titrating Zn(2+) into a fluorescently labeled oligonucleotide at pH 7.5 resulted in an abrupt fluorescence quenching beyond 0.2 mM Zn(2+). At pH 6, quenching occurred linearly with the Zn(2+) concentration, suggesting the effect of Zn(2+) precipitation at pH 7.5. Second, a Zn(2+)-dependent DNA-cleaving DNAzyme was studied. This DNAzyme was inhibited at higher than 2 mM Zn(2+), attributable to Zn(2+) precipitation and adsorption of the DNAzyme. This paper has established the interplay between DNA, Zn(2+), and ZnO. This understanding can avoid misinterpretation of DNA assay results and adds knowledge to DNA immobilization.
authors.affiliation: Department of Chemistry, Waterloo Institute for Nanotechnology, University of Waterloo , Waterloo, Ontario N2L 3G1, Canada.
authors.forename: Lingzi
authors.initials: L
authors.lastname: Ma
authors.affiliation: Department of Chemistry, Waterloo Institute for Nanotechnology, University of Waterloo , Waterloo, Ontario N2L 3G1, Canada.
authors.forename: Biwu
authors.initials: B
authors.lastname: Liu
authors.affiliation: Department of Chemistry, Waterloo Institute for Nanotechnology, University of Waterloo , Waterloo, Ontario N2L 3G1, Canada.
authors.forename: Po-Jung Jimmy
authors.initials: PJ
authors.lastname: Huang
authors.affiliation: Department of Chemistry, Waterloo Institute for Nanotechnology, University of Waterloo , Waterloo, Ontario N2L 3G1, Canada.
authors.forename: Xu
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Department of Chemistry, Waterloo Institute for Nanotechnology, University of Waterloo , Waterloo, Ontario N2L 3G1, Canada.
authors.forename: Juewen
authors.initials: J
authors.lastname: Liu
mesh_terms: D004247:DNA / Q000737:chemistry*; D021881:DNA, Catalytic / Q000737:chemistry*; D005453:Fluorescence; D006863:Hydrogen-Ion Concentration; D009841:Oligonucleotides / Q000737:chemistry*; D015034:Zinc Oxide / Q000737:chemistry*
chemical_list: D021881:DNA, Catalytic; D009841:Oligonucleotides; D004247:DNA; D015034:Zinc Oxide