Phosphoprotein Detection with a Single Nanofluidic Diode Decorated with Zinc Chelates.

Saima Nasir,Mubarak Ali,Christof M Niemeyer,Ishtiaq Ahmed,Wolfgang Ensinger

doi:10.1002/cplu.202000045

Abstract

We report a nanofluidic device for the label-free detection of phosphoprotein (PPn) analytes. To achieve this goal, a metal ion chelator, namely 4-[bis(2-pyridylmethyl)aminomethyl]aniline (DPA-NH2 ) compound was synthesized. Single asymmetric nanofluidic channels were fabricated in polyethylene terephthalate (PET) membranes. The chelator (DPA-NH2 ) molecules are subsequently immobilized on the nanochannel surface, followed by the zinc ion complexation to afford DPA-Zn2+ chelates, which act as ligand moieties for the specific binding of phosphoproteins. The success of the chemical reaction and biomolecular recognition process that occur in a confined geometry can be monitored from the changes in electrical readout of the nanochannel. The nanofluidic sensor has the ability to sensitively and specifically detect lower concentrations (≥1 nM) of phosphoprotein (albumin and α-casein) in the surrounding environment as evidenced from the significant decrease in ion current flowing through the nanochannels. However, dephosphoproteins such as lysozyme and dephospho-α-casein even at higher concentration (>1 μM) could not induce any significant change in the transmembrane ion flux. This observation indicated the sensitivity and specificity of the proposed nanofluidic sensor towards PPn proteins, and has potential for use in differentiating between phosphoproteins and dephosphoproteins.

Highlights

Chelates, which act as ligand moieties for the specific binding of phosphoproteins
Under applied bias higher value of ionic current is noticed at positive voltages compared to the negative one. This non-ohmic behavior is termed as ionic current rectification - a unique characteristic of asymmetric nanochannels.[5e,14–15] The polarity of the fixed chemical groups on the channel surface decides the direction of ion current rectification
DPA Zn2 + complexes which acted as an artificial ligand for the binding of phosphoproteins

Summary

Introduction

Chelates, which act as ligand moieties for the specific binding of phosphoproteins. The success of the chemical reaction and biomolecular recognition process that occur in a confined geometry can be monitored from the changes in electrical readout of the nanochannel. The nanofluidic sensor has the ability to sensitively and detect lower concentrations ( 1 nM) of phosphoprotein (albumin and α-casein) in the surrounding environment as evidenced from the significant decrease in ion current flowing through the nanochannels. Dephosphoproteins such as lysozyme and dephospho-α-casein even at higher concentration (> 1 μM) could not induce any significant change in the transmembrane ion flux. Among the various proteins/enzymes, phosphoprotein (PPn) plays a vital role in different biological processes including signal transduction, metabolic pathways, gene transcription, membrane transport, and others occurring in living organisms.[6]

Methods

Results

Conclusion