Changes of collagen, elastin, and tryptophan contents in laser welded porcine aorta tissues studied using fluorescence spectroscopy

The emission spectra from welded and un-welded (normal) porcine aorta tissues were measured on both sides of intima and adventitia layers. A tunable Forsterite laser and a Cr4+: YAG laser with wavelengths of 1250nm, 1455nm and 1460nm were used to weld porcine aorta tissues. Three emission bands emitted from three key fluorophores were studied under different welding and excitation conditions. With excitation wavelength of 340nm, the 395nm band is associated with the emission from the structural proteins of collagen type III and type I. The 445nm band obtained is associated with the emission of the structural protein of elastin. The 350nm band recorded with excitation wavelength of 300nm is associated with the amino acid of tryptophan. The relative emission intensities of collagen, elastin and tryptophan at their fluorescence peaks changes with laser tissue welding wavelengths indicate the change of contents of those tissue molecules. The ratio of emission peak intensities of collagen to elastin with welding laser wavelength of 1250nm increases by 0.13 as compared to the normal aorta tissue at the intimal side. For the adventitial side of aorta tissue, this ratio decreases by 0.38 in comparison with the normal tissue. These results indicate that content of collagen changes relative to elastin due to laser tissue welding. The peak fluorescence intensity of tryptophan for both sides of welded tunica intima and adventitia increases significantly in comparison with the normal tissue when the optimum laser welding wavelength of 1455 nm was used.