title: Label-Free Pyrophosphate Recognition with Functionalized Asymmetric Nanopores.
abstract: The label-free detection of pyrophosphate (PPi) anions with a nanofluidic sensing device based on asymmetric nanopores is demonstrated. The pore surface is functionalized with zinc complexes based on two di(2-picolyl)amine [bis(DPA)] moieties using carbodiimide coupling chemistry. The complexation of zinc (Zn(2+) ) ion is achieved by exposing the modified pore to a solution of zinc chloride to form bis(Zn(2+) -DPA) complexes. The chemical functionalization is demonstrated by recording the changes in the observed current-voltage (I-V) curves before and after pore modification. The bis(Zn(2+) -DPA) complexes on the pore walls serve as recognition sites for pyrophosphate anion. The experimental results show that the proposed nanofluidic sensor has the ability to sense picomolar concentrations of PPi anion in the surrounding environment. On the contrary, it does not respond to other phosphate anions, including monohydrogen phosphate, dihydrogen phosphate, adenosine monophosphate, adenosine diphosphate, and adenosine triphosphate. The experimental results are described theoretically by using a model based on the Poisson-Nernst-Planck equations.
authors.affiliation: Department of Material- and Geo-Sciences, Materials Analysis, Technische Universität Darmstadt, D-64287, Darmstadt, Germany.|Materials Research Department, GSI Helmholtzzentrum für Schwerionenforschung, D-64291, Darmstadt, Germany.
authors.forename: Mubarak
authors.initials: M
authors.lastname: Ali
authors.affiliation: Karlsruhe Institute of Technology (KIT), Institute for Biological Interfaces (IBG-1), D-76344, Eggenstein-Leopoldshafen, Germany.
authors.forename: Ishtiaq
authors.initials: I
authors.lastname: Ahmed
authors.affiliation: Departamento de Física Aplicada, Universitat Politécnica de València, E-46022, Valencia, Spain.
authors.forename: Patricio
authors.initials: P
authors.lastname: Ramirez
authors.affiliation: Department of Material- and Geo-Sciences, Materials Analysis, Technische Universität Darmstadt, D-64287, Darmstadt, Germany.|Materials Research Department, GSI Helmholtzzentrum für Schwerionenforschung, D-64291, Darmstadt, Germany.
authors.forename: Saima
authors.initials: S
authors.lastname: Nasir
authors.affiliation: Karlsruhe Institute of Technology (KIT), Institute for Biological Interfaces (IBG-1), D-76344, Eggenstein-Leopoldshafen, Germany.
authors.forename: Christof M
authors.initials: CM
authors.lastname: Niemeyer
authors.affiliation: Departamento de Física de la Terra i Termodinàmica, Universitat de València, E-46100, Burjassot, Spain.
authors.forename: Salvador
authors.initials: S
authors.lastname: Mafe
authors.affiliation: Department of Material- and Geo-Sciences, Materials Analysis, Technische Universität Darmstadt, D-64287, Darmstadt, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Ensinger
mesh_terms: D000588:Amines / Q000138:chemical synthesis / Q000737:chemistry; D011756:Diphosphates / Q000138:chemical synthesis / Q000737:chemistry*; D058608:Nanopores; D010848:Picolinic Acids / Q000138:chemical synthesis / Q000737:chemistry; D013194:Staining and Labeling
chemical_list: C501847:2,2'-dipicolylamine; D000588:Amines; D011756:Diphosphates; D010848:Picolinic Acids
keywords: Zn(II)-dipicolylamine complexes; current rectification; functionalization; pyrophosphate, track-etching; sensors