D. Demore et al., Enhancement of 5,10,15,20-tetra(m-hydroxyphenyl)chlorin fluorescence emission by inclusion in natural and modified cyclodextrins, APPL SPECTR, 53(5), 1999, pp. 523-527
Fluorescence properties of 5,10,15,20-tetra(m-hydroxyphenyl)chlorin (m-THPC
), a sensitizer used in photodynamic therapy (PDT), were studied in the pre
sence of three native cyclodextrins (CDs)-alpha-, beta-, and gamma-CD-and t
wo modified cyelodextrins-heptakis (2,6-di-O-methyl) beta-CD (Me-beta-CD) a
nd heptakis (2-O-hydroxy-propyl) beta-CD (HP-beta-CD), The CDs studied have
been shown to undergo the formation of an inclusion complex with m-THPC, l
eading to a large enhancement (up to 300 times) of m-THPC fluorescence inte
nsity depending on the CD used. Stoichiometry and association constants hav
e been determined on the basis of the variation of fluorescence intensity.
A 1:2 stoichiometry has been found for m-THPC complexes with gamma-CD, Me-b
eta-CD, and HP-beta-CD, Association constants as high as K = 9.5 x 10(8) M-
2 in the case of mTHPC/2Me-beta-CD and K = 2.7 x 10(9) M-2 in the case of m
-THPC/2HP-beta-CD complex were determined, whereas a lower value (K = 2.4 x
10(4) M (2)) was found in the case of m-THPC/2 gamma-CD, Because of the hi
ghest fluorescence enhancement (a factor of about 300) observed with Me-bet
a-CD, this compound would be the most suitable to improve the detection of
m-THPC in further pharmacokinetics and biodistribution studies.