Binding detection using liquid crystal

1. A method for determining the presence of a ligand that is not labeled in a sample fluid, said method comprising:

(a) contacting said sample fluid with a surfactant-nucleic acid aptamer interfacial layer under conditions sufficient to form a nucleic acid aptamer-ligand complex in a non-hybridization manner when said ligand is present in said sample fluid, wherein said surfactant-aptamer interfacial layer is present at a liquid crystal and a polar solvent interface, and wherein said nucleic acid aptamer is capable of selectively binding to said ligand, and wherein said nucleic acid aptamer-ligand complex changes orientation of said liquid crystal compared to the orientation of said liquid-crystal in the absence of said nucleic acid aptamer-ligand complex; and

(b) detecting the orientation of said liquid crystal,

wherein detection of change in orientation of said liquid crystal indicates the presence of said ligand in said sample fluid.

2. The method of claim 1 , wherein said surfactant comprises a cationic surfactant.

3. The method of claim 1 , wherein said cationic surfactant comprises a monoalkylquaternary ammonium surfactant, dialkylquaternary ammonium surfactant, trialkylquaternary ammonium surfactant, a monoalkylpyridinium surfactants, quaternized polyoxyethylenated long chain amines, or a combination thereof.

4. The method of claim 1 , wherein said surfactant further comprises a nonionic surfactant.

5. The method of claim 4 , wherein said nonionic surfactant comprises an alkylpolyoxyethylene surfactant, a polyoxyethylenated polyoxypropylene, sorbitan alkyl ester, a polyoxyethylene glycol sorbitan alkyl ester surfactant, or a mixture thereof.

6. The method of claim 1 , wherein said liquid crystal is a thermotropic liquid crystal.

7. The method of claim 6 , wherein said liquid crystal comprises 4-cyano-4′-pentylbiphenyl, 4-cyano-4′-pentyl-p-terphenyl, N-(4-methoxybenzylidene)-4′-butylaniline, 4′-di-n-hexyldiphenyldiacetylene, other biphenyl or terphenyl liquid crystal compounds, or a mixture thereof.

8. The method of claim 1 , wherein said polar solvent comprises an aqueous solution.

9. The method of claim 1 , wherein said step of detecting orientation of said liquid crystal comprises detecting a change in the birefringence of said liquid crystal.

10. The method of claim 1 , wherein polarized light is used to detect orientation of said liquid crystal.

11. The method of claim 1 , where light microscopy is used to detect orientation of said liquid crystal.

12. A method for detecting the presence of a non-labeled ligand in a sample using a non-labeled nucleic acid aptamer, said method comprising:

placing said sample on a ligand detection apparatus comprising a liquid crystal, a surfactant, a polar solvent, and a non-labeled nucleic acid aptamer that binds selectively to said ligand in a non-hybridization manner, wherein a surfactant-nucleic acid aptamer interfacial layer is present at the interface of said liquid crystal and said polar solvent, and wherein said nucleic acid aptamer changes conformation upon binding to said ligand, and wherein the orientation of said liquid crystal changes depending on the conformation of said nucleic acid aptamer; and

detecting the change in orientation of said liquid crystal to determine the presence of said ligand in said sample.

13. The method of claim 12 , wherein said ligand detection apparatus further comprises a solid substrate, and wherein said liquid crystal is bound to said solid substrate.

14. The method of claim 12 , wherein said method of detecting the change in orientation of said liquid crystal comprises determining a change in birefringence of said liquid crystal.