Nanopore device for reversible ion and molecule sensing or migration
Disclosed are methods and devices for detection of ion migration and binding, utilizing a nanopipette adapted for use in an electrochemical sensing circuit. The nanopipette may be functionalized on its interior bore with metal chelators for binding and sensing metal ions or other specific binding molecules such as boronic acid for binding and sensing glucose. Such a functionalized nanopipette is comprised in an electrical sensor that detects when the nanopipette selectively and reversibly binds ions or small molecules. Also disclosed is a nanoreactor, comprising a nanopipette, for controlling precipitation in aqueous solutions by voltage-directed ion migration, wherein ions may be directed out of the interior bore by a repulsing charge in the bore.
1. A nanopipette for use in an apparatus detecting analyte in a sample, comprising:
(a) a capillary portion defining an interior bore of the nanopipette leading to a nanopore;
(b) said interior bore adapted for containing therein an electrode and an interior solution communicating with an exterior solution through said nanopore; and
(c) a coating on an interior surface of said nanopore, comprising
(i) a polyelectrolyte layer bound directly to said interior surface; and
(ii) a binding molecule, linked to said polyelectrolyte, specific for binding an analyte which is selected from the group consisting of an ion or a small molecule.
2. The nanopipette of claim 1 wherein said binding molecule is a boronic acid.
3. The nanopipette of claim 2 wherein said polyelectrolyte is a polycation.
4. The nanopipette of claim 3 wherein said polycation is a polyalkyl pyridine or a polyamine.
5. The nanopipette of claim 2 wherein said coating further comprises a portion that extends into and partially blocks said nanopore.
6. The nanopipette of claim 1 wherein the binding molecule is a chelating agent.
7. The nanopipette of claim 6 wherein the polyelectrolyte layer is selected from the group consisting of (a) a polyacrylic layer, (b) a polyamine layer; and (c) alternating layers of polyacrylic and polyamine.
8. The nanopipette of claim 7 wherein the polyamine is a polyalkyl pyridine.
9. The nanopipette of claim 1 wherein the binding molecule is an ion binding polymer which is a polysaccharide or a polypeptide.
10. The nanopipette of claim 9 wherein the polymer is chitosan.
11. The nanopipette of claim 9 wherein the polymer is calmodulin.
12. A nanopipette apparatus for measuring a saccharide analyte in a sample, comprising:
(a) a nanopipette having an interior bore and a nanopore opening into said sample;
(b) an electrode within said interior bore, arranged to contact an interior solution, and a reference electrode arranged for contacting said sample;
(c) a coating on an inner surface of said nanopore;
(d) said coating comprising a binding molecule specific for binding a saccharide, and effective to bind said saccharide; and
(e) a voltage control circuit for generating a voltage between electrodes and measuring positive and negative ionic current through the sample, the nanopore, and the interior solution, whereby saccharide in said sample causes a concentration dependent change in negative ionic current when bound to said coating comprising said binding molecule.
13. The nanopipette apparatus of claim 12 wherein the binding molecule is a protein.
14. The nanopipette apparatus of claim 12 wherein the binding molecule is a boronic acid.
15. The nanopipette apparatus of claim 12 wherein the nanopipette is quartz.
16. The nanopipette apparatus of claim 12 wherein said voltage control circuit comprises a voltage clamp amplifier.
17. The nanopipette apparatus of claim 12 wherein said coating comprises a polycation.