Photoinactivation of amelanotic and melanotic melanoma cells sensitized by axially substituted Si-naphthalocyanines.
The photosensitizing activity of the new far-red absorbing naphthalocyanine SiNc [OSi (n-C10H21)3] [OSi(CH3)2(CH2)3N(CH3)2], (DAP-SiNc), and of its analogue SiNc [OSi(i-C4H9)2(n-C18H37)]2, (IsoBO-SiNc), was studied with two cell variants of B16 melanoma, the amelanotic clone B78H1 and the highly pigmented B16F1 cells. Upon excitation with a 776 nm diode laser, DAP-SiNc appeared to be a markedly more efficient photosensitizer than isoBO-SiNc. The higher photoefficiency of DAP-SiNc was likely to reflect its accumulation in significantly larger amounts by both cell types, as well as a much smaller tendency to undergo aggregation when bound to the cells. In any case, melanotic cells were less sensitive to the photoinactivating action of DAP-SiNc: the protective action of melanin was a consequence of an optical filtering of the 776 nm light and an appreciable shortening of the DAP-SiNc triplet lifetime (40 microseconds for the amelanotic vs. 17 microseconds for the melanotic cells). Functional and morphological studies on irradiated cells showed that cell death due to DAP-SiNc photosensitization was mainly correlated with the modification of targets located in the lysosomes and the cytoplasmic membrane.
Soncin
M
M
Department of Biology, University of Padova, Padua, Italy. polo@civ.bio.unipd.it
Busetti
A
A
Biolo
R
R
Jori
G
G
Kwag
G
G
Li
Y S
YS
Kenney
M E
ME
Rodgers
M A
MA
D000818:Animals; D000970:Antineoplastic Agents / Q000378:metabolism / Q000494:pharmacology*; D004354:Drug Screening Assays, Antitumor; D018328:Melanoma, Amelanotic; D008546:Melanoma, Experimental; D051379:Mice; D017319:Photosensitizing Agents / Q000378:metabolism / Q000494:pharmacology*; D011166:Porphyrins / Q000378:metabolism / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
D000970:Antineoplastic Agents; D017319:Photosensitizing Agents; D011166:Porphyrins; C076388:2,3-naphthalocyanine