Time-resolved laser-induced fluorescence spectroscopy systems and uses thereof

1. A system for characterizing a biological sample by analyzing emission of fluorescent light from the biological sample upon excitation comprising:

(i) a laser source connected to a biological sample via excitation fibers (ExF), wherein the laser source is configured to radiate the biological sample with a laser pulse at a predetermined wavelength to cause the biological sample to produce a responsive fluorescence signal;

(ii) collection fibers (CF), wherein the CF collect the fluorescence signal from the biological sample, and relays the fluorescence signal to a demultiplexer;

(iii) a demultiplexer configured to split the fluorescence signal from the CF at pre-determined wavelengths to obtain spectral bands of <365 nm , 365-410 nm, 410- 450 nm, 450-500 nm, 500-560 nm, 560-600 nm and >600 nm,

wherein the demultiplexer comprises a first wavelength splitting device at about 500 nm, a second wavelength splitting device at about 560 nm, a third wavelength splitting device at about 600 nm, a fourth wavelength splitting device at about 410 nm, a fifth wavelength splitting device at about 450 nm, and a sixth wavelength splitting device at about 365 nm,

wherein the fluorescence signal from the CF is split by the first wavelength splitting device into a <500 nm signal and a >500 nm signal, the >500 nm signal is split by the second wavelength splitting device into a 500-560 nm signal and a >560 nm signal, the >560 nm signal is split by the third wavelength splitting device into a 560-600 nm signal and a >600 nm signal, the <500 nm signal is split by the fourth wavelength splitting device into a <410 nm signal and a 410-500 nm signal, the 410-500 nm signal is split by the fifth wavelength splitting device into a 410-450 nm signal and a 450-500 nm signal, and the <410 nm signal is split by the sixth wavelength splitting device into a <365 nm signal and a 365-410 nm signal; and

(iv) an optical delay device.

2. The system of claim 1 , wherein the optical delay device is adapted to couple the spectral bands from the demultiplexer into the optical delay device, allow the spectral bands to travel through the optical delay device and introduce a controlled time delay as the spectral bands travel through the optical delay device, so as to capture multiple wavelengths in a single shot.

3. The system of claim 1 , wherein the collection fibers form a single bundle.

4. A method for characterizing a biological sample by analyzing emission of a fluorescence signal from the biological sample upon excitation comprising:

(i) radiating the biological sample with a laser pulse at a predetermined wavelength to cause the biological sample to produce a responsive fluorescence signal;

(ii) collecting the fluorescence signal from the biological sample;

(iii) splitting the fluorescence signal at predetermined wavelengths to obtain spectral bands of <365 nm , 365-410 nm, 410-450 nm, 450-500 nm, 500-560 nm, 560-600 nm and >600 nm,

wherein the fluorescence signal is split into a <500 nm signal and a >500 nm signal, the >500 nm signal is split into a 500-560 nm signal and a >560 nm signal, the >560 nm signal is split into a 560-600 nm signal and a >600 nm signal, the <500 nm signal is split into a <410 nm signal and a 410-500 nm signal, the 410-500 nm signal is split into a 410-450 nm signal and a 450-500 nm signal, and the <410 nm signal is split into a <365 nm signal and a 365-410 nm signal;

(iv) passing the spectral bands through a time-delay mechanism;

(v) obtaining the time-delayed spectral bands; and

(vi) processing the time-delayed spectral bands.

5. The method of claim 4 , wherein the fluorescence signal is emitted by a biomolecule.

6. The method of claim 5 , wherein the biomolecule is any one or more of PLP-GAD (pyridoxal-5′-phosphate (PLP) glutamic acid decarboxylase (GAD)), bound NADH, free NADH, flavin mononucleotide (FMN) riboflavin, flavin adenine dinucleotide (FAD) riboflavin, lipopigments, endogenous porphyrins or a combination thereof.

7. A method for determining tissue viability comprising analyzing emission of fluorescence signals from biomolecules in a biological sample by the method of claim 4 , wherein an increase in fluorescence signals in the biological sample relative to a normal sample is indicative of poor tissue viability.

8. A method for continuously monitoring cellular metabolism comprising analyzing emission of a fluorescence signal by the method of claim 4 .

9. A method for determining drug or metabolite level in plasma comprising analyzing emission of a fluorescence signal from a biomolecule by the method of claim 4 .

10. The method of claim 9 , wherein the biomolecule is NADH.

11. The method of claim 10 , wherein NADH is in free form, bound form or a combination thereof.

12. The system of claim 1 , further comprising a photomultiplier tube configured for detecting the signal received from the optical delay device.

13. The system of claim 12 , further comprising a digitizer configured for digitizing the signal received from the photomultiplier tube.

14. The system of claim 13 , further comprising a preamplifier configured for amplifying the signal received from the photomultiplier tube before the signal is digitized by the digitizer.

15. The system of claim 13 , further comprising a computer system configured for processing and displaying the signal received from the digitizer.

16. The method of claim 4 , wherein processing the time-delayed spectral bands comprises detecting the time-delayed spectral bands.

17. The method of claim 16 , further comprising digitizing the detected signal.

18. The method of claim 17 , further comprising amplifying the detected signal before digitizing the detected signal.

19. The method of claim 17 , further comprising processing and displaying the digitized signal with a computer system.