Inclusion and aggregation properties of an anionic porphyrin with ionic and non-ionic cyclodextrins vesicles for diagnostic applications

Amphiphilic cyclodextrins (CDs) are useful carriers for delivering porphyrins inside cells. The balance between hydrophobic and hydrophilic portion of CDs drives the self-assembly of these compounds in aqueous solutions, affording different organized systems such as micelles or bilayer vesicles, resembling "stealth" liposomes. The size of these vesicles (-100 nm) as well as their biocompatibility could help to avoid renal exclusion and consequently reduce uptake/degradation by the reticulo-endothelial system (RES), affording a prolonged systernic circulation time. The intracellular delivery of different supramolecular oligomers of porphyrins in liposomes is a stimulating challenge for diagnostic applications. Here we present the study of inclusion of an anionic porphyrin (TPPS) in cationic (SC16NH2) and neutral CD vesicles (SC160H). The supramolecular aggregates (CD/TPPS) were isolated by size exclusion chromatography and studied by complementary techniques (UV-Vis, steady-state and time resolved fluorescence, anisotropy and lightscattering). The encapsulation process is mainly driven by Coulombic and/or weak interactions at different pH and ionie strength. The repartition of porphyrins between the hydrophilic core and the hydrophobic moieties of the vesicles. was investigated by fluorescence quenching and competition experiments in presence of Triton X-100. The aggregation properties of TPPS in CD vesicles and for comparison in liposomes at different molar ratio (CD/TPPS) are also discussed.