Multiplexed biomarker quantitation by nanopore analysis of biomarker-polymer complexes
Devices and methods for detecting a target molecule are provided herein. The methods entail contacting a sample with a polymer scaffold, the polymer comprising at least one association site configured to associate with the target molecule. The sample is brought into contact with the polymer to determine whether the target molecule is present in the sample under conditions allowing the target molecule, if present, to associate with the polymer scaffold. The methods further involve loading the polymer into a device comprising a pore or channel that connects two volumes, configuring the device to pass the polymer through the pore or channel from one volume to the other volume, and determining, with a sensor configured to detect objects passing through the pore or channel, whether the target molecule is associated with the association site, and thereby detecting the presence or absence of the target molecule in the sample.
1. A method for determining a presence or an absence of a target protein in a biological sample, comprising the steps of:
(a) providing a dsDNA synthetically modified to comprise a plurality of target protein binding sites, wherein each target protein binding site of the plurality of target protein binding sites:
(i) comprises a 5 base pair (bp) to 30 bp polynucleotide having a specific affinity to the target protein,
(ii) is capable of binding to no more than one target protein,
(iii) is spaced apart from any other target protein binding site, and
(iv) is flanked by two polynucleotides, wherein the two polynucleotides flanking the target protein binding site are non-binding sites that do not bind to the target protein, such that the two polynucleotides inhibit non-specific binding of the target protein in the biological sample to the synthetically modified dsDNA;
(b) contacting the biological sample with the synthetically modified dsDNA under a condition allowing the target protein, if present, to bind to at least one target protein binding site on the synthetically modified dsDNA;
(c) loading the synthetically modified dsDNA into a single nanopore device comprising a silicon nitride substrate of a thickness ranging between 5 nm and 100 nm, wherein said single nanopore device comprises a nanopore having a diameter of no more than 100 nm and a depth of no more than 100 nm, a first chamber, and a second chamber, wherein each of the first chamber and the second chamber comprises a buffer, wherein the first chamber and the second chamber are in fluid communication through the nanopore, and wherein the single nanopore device comprises a sensitive voltage-clamp amplifier;
(d) applying a voltage across the nanopore to pass the synthetically modified dsDNA through said nanopore from the first chamber to the second chamber; collecting an electrical signal from the sensitive voltage-clamp amplifier, wherein the electrical signal is correlated with translocation of the synthetically modified dsDNA through the nanopore;
(e) comparing the electrical signal with a reference electrical signal through an open pore thereby detecting a change in the electrical signal; and
(g) determining from the change in the electrical signal whether the synthetically modified dsDNA is bound to the target protein, wherein the change in the electrical signal indicates whether or not the synthetically modified dsDNA is bound to the target protein.
2. The method of claim 1 , wherein the plurality of target protein binding sites comprises at least three target protein binding sites including a first target protein binding site, a second target protein binding site and a third target protein binding site.
3. The method of claim 2 , wherein the second target protein binding site comprises a nucleotide sequence that is different from the nucleotide sequence of the first target protein binding site.
4. The method of claim 2 , wherein the third target protein binding site comprises a nucleotide sequence that is identical to the nucleotide sequence of the first target protein binding site.
5. The method of claim 1 , wherein said target protein is a mammalian protein.
6. The method of claim 5 , wherein the mammalian protein is selected from the group consisting of an antibody, an epitope, a hormone, a neurotransmitter, a cytokine, a growth factor, a cell recognition molecule, and a receptor.
7. The method of claim 2 , wherein the synthetically modified dsDNA comprises a spacer polynucleotide of 100 base pairs (bp) to 1000 bp between the first target protein binding site and the second target protein binding site.
8. The method of claim 1 , wherein each binding site of the plurality of target protein binding sites is less than 20 base pair sequence.