Development and characterization of silk fibroin-enriched 3D printed hydrogels for photosensitizer delivery

Photodynamic therapy (PDT) uses photosensitizing drugs and visible light to produce cytotoxic reactive oxygen species for targeting cell death. The aggregation of photosensitizers poses a significant challenge to the delivery of the treatment deeper within the tissue. In this study we developed 3D-printed hydrogels composed of gelatin/alginate and Pluronic® F127/alginate polymers with various silk fibroin concentrations to act as reservoirs for the sustained delivery of photosensitizers using water-soluble porphyrin and phenalenone as model drugs. We used rheology and spectrophotometry to analyze the 3D hydrogel scaffolds, focusing on the effect of silk fibroin on photosensitiser incorporation and release. The study showed that increased silk fibroin concentration affected the mechanical strength and the printability of the hydrogels. Compression analysis showed decreased hydrogel mechanical strength at higher silk fibroin concentrations, and cell viability assays indicated the biocompatibility of these hydrogels. Rapid photosensitizer release was observed, aligning with first-order kinetics for gelatin-based and the Higuchi model for hydrogels based on Pluronic® F-127. These findings highlight the potential of 3D-printed hydrogels as a reservoir for the sustained release of photosensitizers and underscore the importance of hydrogel formulation.