title: In Vitro Selection of Chromium-Dependent DNAzymes for Sensing Chromium(III) and Chromium(VI).
abstract: Chromium is a very important analyte for environmental monitoring, and developing biosensors for chromium is a long-standing analytical challenge. In this work, in vitro selection of RNA-cleaving DNAzymes was carried out in the presence of Cr(3+) . The most active DNAzyme turned out to be the previously reported lanthanide-dependent Ce13d DNAzyme. Although the Ce13d activity was about 150-fold lower with Cr(3+) than that with lanthanides, the activity of lanthanides and other competing metals was masked by using a phosphate buffer; this left Cr(3+) as the only metal that could activate Ce13d. With 100 μm Cr(3+) , the cleavage rate is 1.6 h(-1) at pH 6. By using a molecular beacon design, Cr(3+) was measured with a detection limit of 70 nm, which was significantly lower than the United States Environmental Protection Agency (EPA) limit (11 μm). Cr(4+) was measured after reduction by NaBH4 to Cr(3+) , and it could be sensed with a similar detection limit of 140 nm Cr(4+) ; this value was lower than the EPA limit of 300 nm. This sensor was tested for chromium speciation analysis in a real sample, and the results supported its application for environmental monitoring. At the same time, it has enhanced our understanding of the interactions between chromium and DNA.
authors.affiliation: School of Pharmaceutical Sciences, Central South University, Changsha, Hunan, 410013, P.R. China.|Department of Chemistry, Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada.
authors.forename: Wenhu
authors.initials: W
authors.lastname: Zhou
authors.affiliation: Department of Chemistry, Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada.
authors.forename: Mahsa
authors.initials: M
authors.lastname: Vazin
authors.affiliation: Department of Chemistry, Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada.
authors.forename: Tianmeng
authors.initials: T
authors.lastname: Yu
authors.affiliation: School of Pharmaceutical Sciences, Central South University, Changsha, Hunan, 410013, P.R. China.
authors.forename: Jinsong
authors.initials: J
authors.lastname: Ding
authors.affiliation: School of Pharmaceutical Sciences, Central South University, Changsha, Hunan, 410013, P.R. China. liujw@uwaterloo.ca.|Department of Chemistry, Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada. liujw@uwaterloo.ca.
authors.forename: Juewen
authors.identifier: http://orcid.org/0000-0001-5918-9336
authors.initials: J
authors.lastname: Liu
keywords: DNA; chromium; polymerase chain reaction; sensors; water chemistry