Nano-plasmonic sensor for exosome detection

1. A nano-plasmonic sensor for detecting exosomes comprising,

a) a transparent planar substrate;

b) a metal film disposed onto one surface of the substrate, wherein the metal film comprises a plurality of nanoapertures in a predefined pattern to create a sensing area that produces surface plasmon resonance upon illumination;

c) a molecular spacer directly attached to the metal film, wherein the molecular spacer comprises long-chain PEG and short-chain PEG in a ratio of about 1:3; and

d) a linking agent directly attached to the molecular spacer and directly attached to a capture agent, wherein the capture agent specifically binds to an exosome marker.

2. The nano-plasmonic sensor of claim 1 , wherein the metal film comprises a noble metal, a transition metal, an alkali metal, or any combination thereof.

3. The nano-plasmonic sensor of claim 2 , wherein the substrate comprises glass, quartz, diamond, or a polymer.

4. The nano-plasmonic sensor of claim 3 , wherein the metal film comprises gold and the substrate comprises glass.

5. The nano-plasmonic sensor of claim 4 , wherein the metal film is between 50 to 500 nm thick.

6. The nano-plasmonic sensor of claim 5 , further comprising an adhesion layer located between the metal film and the substrate surface.

7. The nano-plasmonic sensor of claim 6 , wherein the adhesion layer is less than about 50 nm thick.

8. The nano-plasmonic sensor of claim 7 , wherein the predefined pattern is periodic.

9. The nano-plasmonic sensor of claim 8 , wherein the nanoapertures have a dimension and periodicity that produce an electromagnetic field with a decay length of about 50 nm to 200 nm when the nanoapertures are illuminated by light with a wavelength close to or at the surface plasmon resonance.

10. The nano-plasmonic sensor of claim 9 , wherein the nanoapertures are circular, elliptical, rectangular, triangular, oval, or hexagonal.

11. The nano-plasmonic sensor of claim 10 , wherein the circular nanoapertures are about 50 nm to 300 nm in diameter, and wherein the periodicity is about 400 nm to 700 nm.

12. The nano-plasmonic sensor of claim 11 , wherein the circular nanoapertures are about 200 nm in diameter, and wherein the periodicity is about 450 nm to 500 nm.

13. The nano-plasmonic sensor of claim 1 , wherein the linking agent comprises protein A/G or neutravidin.

14. A method of detecting exosomes in a sample, comprising

a) introducing a sample suspected of containing one or more exosomes onto a nano-plasmonic sensor of claim 1 under conditions which promote binding of the exosomes to the sensor;

b) washing the sensor to remove unbound materials;

c) illuminating the sensor to thereby transmit light through the sensor;

d) measuring the light transmitted through the sensor to identify a significant change from that of a negative control; and

e) detecting exosomes in the sample when the significant change m the transmitted light is identified.

15. The method of claim 14 , wherein the negative control is a solution substantially free of exosomes or exosome lysates.

16. The method of claim 14 , wherein the change is a shift in peak wavelength.

17. A method for determining an expression level of a target marker in a sample of exosomes, comprising:

a) detecting total exosomes in the sample by the method of claim 14 , using a capture agent that specifically binds a pan-exosomal marker;

b) detecting exosomes in the sample expressing the target marker by the method of claim 14 using a capture agent that specifically binds the target marker; and

c) calculating the ratio of exosomes with the target marker to total exosomes to thereby indicate the average expression level of the target marker per exosome from the sample.