Integrated membrane sensor for rapid molecular detection
Disclosed are methods, compositions, and devices for an integrated, heterogeneous ion-exchange membrane-based plastic microfluidic biochip platform that can be used to detect multiple diagnostic markers present in real samples. Its various components can be easily integrated in a modular fashion for different applications. Automated control allows sequential and dynamic activation of different components on the chip. The integrated platform consists of three units and is designed to execute the following functions: (i) separation of the target biomolecules from the real sample, (ii) localizing and concentrating the targeted molecules at a specific location in the microfluidic chip, and (iii) detection of the targeted molecules using hybridization/docking events against a complementary ssDNA oligoprobe sequence or a specific antibody.
1. A system for concentrating charged molecules, the system comprising a pre-concentration unit comprising:
a pre-concentration fluidic channel;
a pre-treatment unit comprising:
a pre-treatment fluidic channel, fluidly coupled to the pre-concentration fluidic channel;
at least two electrodes coupled to a voltage-current source and configured to generate an electric field within the pre-treatment fluidic channel; and
a molecular filter within the pre-treatment fluidic channel, wherein sample molecules flowing through the pre-treatment fluidic channel are separated by both charge and by molecular weight;
an upstream ion exchange membrane and a downstream ion exchange membrane disposed along the pre-concentration fluidic channel; and a negatively charged electrode and a positively charged electrode coupled to the voltage-current source and configured to generate an electric field within the pre-concentration fluidic channel, wherein the charged molecules are concentrated within the pre-concentration fluidic channel at a location where opposing flow and electrophoretic forces are substantially equivalent.
2. The system of claim 1 , wherein the charged molecules are present in a pre-treated sample.
3. The system of claim 2 , wherein the pre-treated sample is a sample of blood, serum, or urine that has been pre-treated.
4. The system of claim 1 , wherein the charged molecules are biomolecules.
5. The system of claim 4 , wherein the biomolecules are nucleic acids.
6. The system of claim 1 , wherein the upstream ion exchange membrane and the downstream ion exchange membrane are cation exchange membranes or anion exchange membranes.
7. The system of claim 1 , wherein the upstream ion exchange membrane and the downstream ion exchange membrane are separated by a distance of about 1 cm or less.
8. The system of claim 1 , wherein the upstream ion exchange membrane is ion non-selective, and wherein the downstream ion exchange membrane is ion selective.
9. The system of claim 1 , wherein the pre-concentration unit further comprises an upstream reservoir in fluid communication with the upstream ion exchange membrane and a downstream reservoir in fluid communication with the downstream ion exchange membrane, and wherein the upstream reservoir and the downstream reservoir are not in fluid communication with the pre-concentration fluidic channel.
10. The system of claim 9 , wherein the positively charged electrode is within the upstream reservoir and the negatively charged electrode is within the downstream reservoir, or wherein the negatively charged electrode is within the upstream reservoir and the positively charged electrode is within the downstream reservoir.
11. The system of claim 1 , further comprising a sensor region and/or a pumping system.
12. The system of claim 1 , wherein the pre-treatment unit comprises: a fluid inlet; and a sample inlet.
13. A method for concentrating a charged molecule, the method comprising:
introducing a pre-treated sample to a pre-concentration unit, wherein the pre-concentration unit comprises:
a pre-concentration fluidic channel;
an upstream ion exchange membrane and a downstream ion exchange membrane disposed along the pre-concentration fluidic channel; and
a negatively charged electrode and a positively charged electrode coupled to a voltage-current source and configured to generate an electric field within the pre-concentration fluidic channel, wherein the pre-concentration unit further comprises an upstream reservoir in fluid communication with the upstream ion exchange membrane and a downstream reservoir in fluid communication with the downstream ion exchange membrane, and wherein the upstream reservoir and the downstream reservoir are not in fluid communication with the pre-concentration fluidic channel; and
applying voltage to the pre-concentration unit,
wherein the charged molecules are concentrated within the pre-concentration fluidic channel at a location where opposing flow and electrophoretic forces are substantially equivalent.
14. The method of claim 13 , wherein applying voltage generates a concentration region defined by high concentrations of charged molecules and a depletion region defined by low concentrations of charged molecules.
15. The method of claim 13 , wherein the electrical field moves charged molecules to a sensor region.
16. The method of claim 13 , wherein the voltage is in a range between about 25 V to about 200 V.
17. The method of claim 13 , wherein the positively charged electrode is within the upstream reservoir and the negatively charged electrode is within the downstream reservoir, or wherein the negatively charged electrode is within the upstream reservoir and the positively charged electrode is within the downstream reservoir.
18. The method of claim 17 , wherein the electric field is generated by applying the voltage—current source to the upstream reservoir and the downstream reservoir.
19. The method of claim 13 , wherein the pre-treated sample flows through the pre-concentration fluidic channel at a flow rate ranging from about 1 μL/minute to about 100 μL/minute.