Label-Free Pyrophosphate Recognition with Functionalized Asymmetric Nanopores

[EN] 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 (Zn2+) ion is achieved by exposing the modified pore to a solution of zinc chloride to form bis(Zn2+¿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(Zn2+¿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.
M.A., S.N., and W.E. acknowledge the funding from the Hessen State Ministry of Higher Education, Research and the Arts, Germany, under the LOEWE project iNAPO. P.R. and S.M. acknowledge financial support by the Generalitat Valenciana (Program of Excellence Prometeo/GV/0069), the Spanish Ministry of Economic Affairs and Competitiveness (MAT2015-65011-P), and FEDER. I. A. and C.M.N. acknowledge financial support through the Helmholtz programme BioInterfaces in Technology and Medicine. The authors are also thankful to Prof. C. Trautmann, Department of Materials Research from GSI, for support with irradiation experiments.