Uptake and release of photosensitizers in a hydrogel for applications in photodynamic therapy: the impact of structural parameters on intrapolymer transport dynamics

In this study a hydrogel is presented that can be used as a carrier and release system for photosensitizers. Because of the high structural variety of photosensitizers, four different substances were analysed. Two porphyrins, 5,10,15,20-tetrakis(1-methyl-4-pyridinio)porphyrin tetra(p-toluene-sulfonate) and sodium meso-tetraphenylporphine-4,4′,4′′,4′′′-tetrasulfonat, eosin y and methylene blue were selected. Uptake and release of these photosensitizers were studied. All photosensitizers were taken up by the hydrogel not depending significantly on the structure of the photosensitizer, and it was possible to load the hydrogels in the μmol g(−1) range. Nevertheless, size and pK(a) value were shown to influence the release behaviour. Finally, the singlet oxygen generation of the photosensitizer after release was demonstrated. The photosensitizer was still highly active and produced a sufficient amount of singlet oxygen.