Photoswitchable binary nanopore capable of detecting single molecules
Disclosed herein is the fabrication of a photo-regulated nanopore by covalently linking a photoswitch to the interior of a silicon-based membrane and related methods of translocating an analyte and distinguishing molecule types through such a nanopore.
1 . A re-configurable translocation device capable of translocating a sample and distinguishing molecule types contained therein, the device comprising a cell that comprises:
(a) a source reservoir capable of holding a source solution and configured to be in electrical communication with an electrical source outside the cell,
(b) a target reservoir capable of holding a target solution and configured to be in electrical communication with the electrical source outside the cell, and
(c) a silicon-based membrane disposed between the source reservoir and the target reservoir, the membrane having at least one interior surface defining a nanopore having an average diameter between about 1 nm and about 100 nm, wherein the nanopore fully penetrates the membrane allowing passage of molecules between the source reservoir and the target reservoir, and wherein the interior surface defining the nanopore has been functionalized with at least one functional group comprising a photo-isomerizable compound,
wherein the photo-isomerizable compound on the nanopore surface is responsive to either visible or ultraviolet light or both with at least one configurational change that alters the steric properties of the photo-isomerizable compound and effects distinguishing one molecule type from another based on a detectable change in electroosmotic or electrophoretic transport of the sample, thereby re-configures the nanopore, and wherein the detectable change comprises a change in pore conductance in connection with the passage of a molecule type through the nanopore; and
wherein, when an electrical potential is applied between the electrical source outside the cell and both the source reservoir and the target reservoir, measurements of electrical signals between the source reservoir and the target reservoir can be made, thereby providing distinguishing information on different molecule types that pass between the source reservoir and the target reservoir.
2 . The translocation device of claim 1 wherein electrolyte salt concentration in the source or target solution is varied to alter electroosmotic flow through the nanopore.
3 . The translocation device of claim 1 wherein a valve is disposed between the target reservoir and the membrane.
4 . A method of separating molecule types in a solution contained in the source reservoir of the translocation device of claim 3 , comprising the sequential steps of:
(a) configuring the nanopore by subjecting the nanopore surface to an initial radiation of visible, ultra-violet light, or thermal energy,
(b) applying a first electrical potential between the source reservoir and the target reservoir;
(c) operating the device for a first time period sufficient to translocate a first molecule type from the source reservoir into the target reservoir;
(d) preventing the first molecule type from passing back into the source reservoir through the valve and removing or otherwise isolating the first molecule type;
(e) optionally re-configuring the photo-isomerizable compound on the interior surface of the nanopore by subjecting the nanopore surface to radiation of visible, ultra-violet light or thermal energy;
(f) applying a second electrical potential between the source reservoir and the target reservoir; and
(g) operating the device for a second time period sufficient to translocate a second and different molecule type from the source reservoir into the target reservoir.
5 . A method of claim 4 , wherein step (e) further comprises adjusting at least one of the parameters selected from the group consisting of pore conductance, voltage polarity applied, the charge distribution or characteristics of the pore surface, hydrophilicity of the pore surface, ionic-solvent-composition, and ionic-solvent-pH value.
6 . The translocation device of claim 1 wherein any reservoir is removable.
7 . The translocation device of claim 1 wherein the nanopore is capable of distinguishing between two molecule types in an ionic fluid by altering the ratio or direction of electroosmotic transport to electrophoretic transport through the nanopore.
8 . The translocation device of claim 1 wherein the nanopore has of an average diameter between about 1 nm and about 20 nm.
9 . The translocation device of claim 1 wherein the interior surface of the membrane defines two or more nanopores where the sizes of at least two nanopores vary.
10 . The translocation device of claim 1 wherein the membrane is made from silicon nitride.
11 . The translocation device of claim 1 wherein the photo-isomerizable compound comprises an azobenzene or an azobenzene derivative.
12 . The translocation device of claim 1 wherein the distinguishing is made through resistive-pulse sensing.
13 . The translocation device of claim 1 wherein the photo-isomerizable compound comprises a photochromic molecule selected from the group consisting of spiropyrans, hydrazones, donor-acceptor Stenhouse adducts, stilbenes, azobenzene, azobenzene derivatives, diarylethenes and diarylethene derivatives, and dithienylethenes and dithienylethene derivatives.
14 . The translocation device of claim 1 wherein the membrane comprises a material selected from the group consisting of a polymer, an MXene, a transition metal dichalcogenide, silicon, silicon oxide, silicon nitride, graphene, molybdenum disulfide and hexagonal boron nitride.
15 . The translocation device of claim 1 , wherein the photo-isomerizable compound forms a monolayer on the nanopore surface with a thickness between 0.1 nm and 25 nm±5% or less.
16 . The translocation device of claim 1 , wherein the diameter of the pore is changed by a factor between 0 and approximately twice of length of the fully extended photoswitched molecule when the photoswitched molecule is changed between its available photo-isomers.
17 . The translocation device of claim 1 , wherein said one or more molecule types are each selected from the group consisting of oligo- or polynucleotides, oligo- or polypeptides, oligo- or polysaccharides, polymers, small molecules and mixtures thereof.
18 . The translocation device of claim 17 , wherein said one or more molecule types are each selected from the group consisting of DNA molecules, RNA molecules, neutral carbohydrates, charged carbohydrates, complex carbohydrates, proteins, lipids, sugars, starch, cellulose, collagen, and combinations thereof.
19 . The translocation device of claim 18 , wherein said complex carbohydrate is maltodextrin.
20 . The translocation device of claim 17 , wherein said photo-regulated nanopore may be tuned to either be responsive to sensing DNA or a complex carbohydrate biopolymer or unresponsive to sensing DNA or a complex carbohydrate biopolymer.
21 . A method for manufacturing a photo-regulated nanopore sensor comprising the steps of:
conducting controlled dielectric breakdown of a silicon nitride membrane until at least one nanopore having an average diameter between about 1 nm and about 100 nm is formed across the membrane; and
functionalizing an interior surface of said nanopore by photohydrosilyation of an azobenzene to the silicon nitride membrane until the azobenzene forms a monolayer covering substantially all of the nanopore surface.
22 . The method for manufacturing a photo-regulated nanopore sensor according to claim 21 , wherein said azobenzene is 4-(propargyloxy) azobenzene.
23 . The method for manufacturing a photo-regulated nanopore sensor according to claim 21 , wherein the thickness of the silicon nitride membrane is between 20 to 100 nm±5% after the photohydrosilyation step.
24 . The method for manufacturing a photo-regulated nanopore sensor according to claim 21 , wherein the thickness of the silicon nitride membrane is between 1 to 20 nm±5% after the photohydrosilyation step.