Document Detail

Cationic dye-sensitized degradation of sodium hyaluronate through photoinduced electron transfer in the upper excited state.
MedLine Citation:
PMID:  11594048     Owner:  NLM     Status:  PubMed-not-MEDLINE    
The formation of ground-state complexes of methylene blue (MB) and thionine (TN) with sodium hyaluronate (NaHA) was clearly observed by means of absorption spectra in aqueous solution. Irradiation of the complexes using 313 nm light caused significant degradation of NaHA under oxygen and argon. However, the use of visible light over 400 nm, which gives the lowest excited singlet state of the cationic dyes, caused no degradation. MB and TN were more efficient sensitizers for the degradation of NaHA than rose bengal (RB), although RB is a more efficient singlet oxygen (1O2) sensitizer than the cationic dyes. Under similar conditions the polysaccharides with carboxyl groups, such as alginic acid and polygalacturonic acid, also photodecomposed. However, the polysaccharides without carboxyl groups, such as pullulan and methyl cellulose, did not. The irradiation of the polysaccharides in the presence of powdered titanium dioxide as a photocatalyst to generate the hydroxyl radical (.OH) in aerated aqueous solution caused the fragmentation of all the polymers. It was confirmed that methyl viologen, an electron-accepting sensitizer, formed a charge-transfer complex with NaHA, the irradiation of which caused the efficient degradation of NaHA. In the presence of beta- and gamma-cyclodextrins the MB- and TN-sensitized photodegradation of NaHA was markedly suppressed. This was probably due to the formation of the inclusion complexes comprising the cationic dyes and the cyclodextrins. On the basis of the results obtained we propose that the cationic dye-sensitized degradation of NaHA involves a photoinduced electron-transfer process between the upper excited dyes and the ground-state NaHA and that .OH and 1O2 do not participate in the degradation.
M Kojima; K Takahashi; K Nakamura
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Photochemistry and photobiology     Volume:  74     ISSN:  0031-8655     ISO Abbreviation:  Photochem. Photobiol.     Publication Date:  2001 Sep 
Date Detail:
Created Date:  2001-10-11     Completed Date:  2001-12-04     Revised Date:  2003-10-31    
Medline Journal Info:
Nlm Unique ID:  0376425     Medline TA:  Photochem Photobiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  369-77     Citation Subset:  -    
Department of Bioscience and Biotechnology, Faculty of Agriculture, Shinshu University, Kami-ina, Nagano 399-4598, Japan.
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