Small DNAs that Bind Nickel(II) Specifically and Tightly.

Metal recognition by nucleic acids provides an intriguing route for biosensing of metal. Toward this goal, a key prerequisite is the acquisition of nucleic acids that can selectively respond to specific metals. Herein, we report for the first time the discovery of two small DNAs that can specifically bind Ni and discriminate against similar ions, particularly, Co. Their minimal effective constructs are 60-70 nucleotides (nt) in length with Ni binding even at harsh denaturing conditions of 8 M urea and 50 mM EDTA. Using isothermal titration calorimetry (ITC), we estimated the dissociation constant () of a representative DNA to be 24.0 ± 4.5 μM, with a 9:1 stoichiometry of Ni bound to DNA. As being engineered into nanosized particles, these DNAs can act like nanosponges to specifically adsorb Ni from artificial wastewater, demonstrating their potential as a novel molecular tool for high-quality nickel enrichment and detection.