S. Hackbarth et al., Photophysical properties of pheophorbide-a-substituted diaminobutane poly-propylene-imine dendrimer, CHEM PHYS, 269(1-3), 2001, pp. 339-346
Dendrimers are very promising molecules as hosts for guest embedding as wel
l as for multiple covalent coupling of dye molecules to their peripheral gr
oups. The use of such dendrimer-dye conjugates as part of a modular carrier
system for photodynamic therapy has recently been discussed. Using covalen
t coupling we accomplished an average loading of 12-13 molecules of pheopho
rbide a to one diaminobutane poly-propylene-imine dendrimer molecule of the
third generation (DAB dendrimer) having a total number of 16 binding sites
. This was confirmed with various photophysical measurements and MALDI-mass
spectrometry.
As long as the dye molecules are covalently bound to the dendrimer, their p
hotosensitized generation of singlet oxygen is reduced dramatically due to
interactions between different dye molecules. The main interaction is suppo
sed to be a Forster-energy transfer along the surface of the dendrimer-dye
complex. Nevertheless the remaining photo-physical generated singlet oxygen
leads to a destruction of the dendrimer backbone under illumination. The p
hotophysical properties of the covalently linked dye-dendrimer complexes an
d especially the remarkable influence of illumination on these properties a
re presented in this paper. (C) 2001 Elsevier Science B.V. All rights reser
ved.