Matthias Helmreich

Intracellular Uptake and Phototoxicity of 31, 32 -Didehydrophytochlorin-fullerene Hexaadducts

C60‐fullerene derivatives are potential building blocks in modular carrier systems for selective tumor targeting. In [5:1] fullerene hexakis adducts, one position can be occupied by an addressing unit (e.g. monoclonal antibody) while the other five positions are suitable for dendrimers or spacers loaded with several drug moieties. This article reports intracellular uptake and phototoxicity of three fullerene hexakis adducts coupled with a different number of photosensitizers: a bis(31,32‐didehydrophytochlorin)‐fullerene [5:1]‐hexaadduct (FHP1), a fullerene [5:1]‐hexaadduct with six 31,32‐didehydrophytochlorin groups (FHP6) and a fullerene [6:0]‐hexaadduct that carries 12 31,32‐didehydrophytochlorin units (FHP12).

Synthesis of novel pyropheophorbide a-fullerene conjugates

Two pyropheophorbide a units were attached via a malonate addition reaction to the [60]fullerene core to give a trichromophoric system. Also, in a different approach two pyropheophorbide a moieties were coupled to a hexasubstituted [60]fullerene diol. The mono-adduct was very light and oxygen sensitive whereas the corresponding hexaadduct showed a much higher stability.

Trap formation and energy transfer in pheophorbide a -DAB-dendrimers and pyropheophorbide a -fullerene C 60 hexaadduct molecular systems

The photophysical properties of DAB-dendrimers from 1st to 4th generation as well as Diaminohexane - all substituted with the in maximum achievable quantity of pheophorbide a (Pheo) molecules were studied in comparison with a novel hexapyropheophorbide a - fullerene hexaadduct (FHP6) and a fullerene [6:0]-hexaadduct which carries twelve pyropheophorbide a units (FHP12) using both steady-state and time-resolved spectroscopic methods. It was found that neighboring dye molecules covalently linked to one DAB- or fullerene moiety due to the length and high flexibility of carbon chains could stack with each other. This structural property is the reason for the possibility of formation different types of energy traps, which were resolved experimentally. The dipole-dipole resonance F&diaero;rster energy transfer between the dye molecules coupled to one complex caused a very fast and efficient delivery of the excitation to a trap. As result the fluorescence as well as the singlet oxygen quantum yields of the different complexes were reduced with increasing number of dye molecules per complex. Nevertheless in every case the singlet oxygen generation was less influenced then the fluorescence quantum yield, exposing the complex to a non-negligible amount of excited oxygen in the singlet state. While the fullerene complexes turned out to be stable under these conditions, the DAB-dendrimer-backbones were completely fragmented to small rudiments carrying just one or a small number of dye molecules.