Chemical bleaching of dyes using radical photoinitiators

1. A method of probing multiple targets in a multiplexed assay of a biological sample comprising:

(a) binding at least one probe to one or more first targets present in the biological sample including multiple targets, wherein the probe comprises at least one signal generator;

(b) detecting a signal from the at least one probe bound in step (a);

(c) contacting the sample comprising the bound probe of step (a) with a radical photoinitiator, wherein the photoinitiator generates free radicals upon irradiation wherein the at least one signal generator is capable of being inactivated by free radicals generated by the radical photoinitiator;

(d) irradiating the sample of step (c) to selectively chemically modify one or more signal generator of the at least one bound probe by reaction of the signal generator with the free radicals generated from the radical photoinitiator, wherein the modification substantially inactivates the signal generator;

(e) binding at least one probe to one or more second targets different from the first targets present in the sample of step (d); and

(f) detecting a signal from the probe bound in step (e),

wherein the radical photoinitiator comprises 2-(4-methoxystyryl)-4,6-bis (trichloromethyl)-1,3,5-triazine, Irgacure 819, diphenyliodonium triflate, hexachloro 2,4,4-trimethyl-1,3,5 triazine, benzoin ethers, camphorquinone, anthraquinone, benzil, aminoalkylphenones, thioxanthone, acylphosphine oxides, polysilanes, alpha-dialkyloxy acetophenones, a-hydroxyalkylphenones or titanocenes.

2. The method of claim 1 , wherein the probe in step (a) comprises an optical signal generator, and the signal detected in step (b) is an optical signal.

3. The method of claim 2 , wherein the probe in step (a) comprises a fluorescent signal generator, and the signal detected in step (b) is a fluorescent signal.

4. The method of claim 3 , wherein the fluorescent signal generator comprises a cyanine dye.

5. The method of claim 4 , wherein the cyanine dye is Cy3 or Cy5.

6. The method of claim 1 , wherein irradiating the sample in step (d) is carried out in the presence of an organic solvent.

7. The method of claim 6 , wherein the organic solvent comprises methanol.

8. The method of claim 1 , wherein steps (c) and (d) are carried out at the temperature of 4-50° C.

9. The method of claim 1 , wherein irradiating the sample in step (d) is accomplished by exposing the sample to light of 250 nm-1.3 μM in wavelength.

10. The method of claim 9 , wherein irradiating the sample in step (d) is accomplished by exposing the sample to light of 250-700 nm in wavelength.

11. The method of claim 1 , wherein steps (c)-(f) are repeated one or more times.

12. The method of claim 1 , wherein the steps (c) and (d) are performed for about 20 seconds to about 15 minutes.

13. The method of claim 1 , further comprising measuring one or more intensity values of the signal detected in detecting step (b), step (f), or steps (b) and (f).

14. The method of claim 13 , further comprising correlating the intensity value with an amount of target present in the sample.

15. The method of claim 1 , wherein the probe in step (a) and the probe in step (e) each comprise a signal generator, wherein the signal generator in step (a) is different from the signal generator in step (e).

16. The method of claim 1 , wherein the radicals produced comprises alkyl, aryl, or halogen radicals.

17. The method of claim 1 , wherein the signal generator is irreversibly modified.

18. The method of claim 1 , wherein no detectable signal is observed after step (d).