Document Detail

In vitro photodynamic effects of phthalocyaninatosilicon covalently linked to 2,2,6,6-tetramethyl-1-piperidinyloxy radicals on cancer cells.
MedLine Citation:
PMID:  15749388     Owner:  NLM     Status:  MEDLINE    
In this paper, we have investigated the ability to sensitize the phototoxicity toward HeLa cells in vitro, of tetra-tert-butylphthalocyaninatosilicon (SiPc) covalently linked to one or two 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) radicals (R1c or R2c), which are shown as photosensitizers efficiently producing singlet oxygen (1Delta(g)). Addition of R1c or R2c encapsulated in liposomes to cultures, followed by irradiation with a 680-nm dye laser, resulted in a highly significant phototoxicity toward HeLa cells, in contrast to negligible phototoxicity observed with (dihydroxy)SiPc (R0). EPR measurements indicate that R1c and R2c exist in some degree as nitroxide radicals even in HeLa cells. Electronic absorption spectra indicate that the degree of aggregation increases in the order R2c<R1c<R0. Thus, the high phototoxicity of R1c and R2c toward HeLa cells is reasonably interpreted by both the large singlet oxygen yield and the inhibition of aggregation due to the bulky TEMPO radicals. This increase in photodynamic effect on HeLa cells is an unusual and important example for increasing the photobiological reaction yields using paramagnetic radicals.
Kazuyuki Ishii; Atsushi Takayanagi; Shinsuke Shimizu; Hisaku Abe; Kazuhiro Sogawa; Nagao Kobayashi
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Free radical biology & medicine     Volume:  38     ISSN:  0891-5849     ISO Abbreviation:  Free Radic. Biol. Med.     Publication Date:  2005 Apr 
Date Detail:
Created Date:  2005-03-07     Completed Date:  2005-09-26     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  8709159     Medline TA:  Free Radic Biol Med     Country:  United States    
Other Details:
Languages:  eng     Pagination:  920-7     Citation Subset:  IM    
Department of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan.
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MeSH Terms
Antineoplastic Agents / chemistry,  toxicity*
Cyclic N-Oxides / chemistry
Hela Cells
Indoles / chemistry,  toxicity*
Organosilicon Compounds / chemistry,  toxicity*
Photosensitizing Agents / chemistry,  toxicity*
Reg. No./Substance:
0/Antineoplastic Agents; 0/Cyclic N-Oxides; 0/Indoles; 0/Organosilicon Compounds; 0/Photosensitizing Agents; 135719-28-7/silicon phthalocyanine; 2564-83-2/TEMPO

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