Photoinduced effect of hypericin on collagen and tissues with high collagen content

摘要

Abstract: The photoinduced effects of hypericin, a polycyclic quinone, on collagen has been investigated. It was found that after laser irradiation at both 532 nm and 337 nm, the spectral form of triple helix structure collagen fluorescence, changed to a spectral profile bearing resemblance to that of its polypeptide single chain counterpart, gelatin, or heated collagen. The effect of Chlorin e$-6$/ on collagen was also investigated and proved to be dissimilar to that of hypericin and not indicative of profound structural alterations. Second Harmonic Generation (SHG) of 1064 nm- nanosecond laser radiation in collagen was studied. While it was very efficient for pure collagen, the signal intensity was found to diminish by at least an order of magnitude after hypericin photosensitization or heating. The above noted fluorescence spectra form alteration was also observed in a smaller scale in collagen rich chicken tissue (tendon). Non sensitized chicken tendon tissue exhibited very efficient SHG, unlike skin and artery samples.!10