Palladium Porphyrin-Modified Fibrin Hydrogel for Oxygen Sensing in Engineered Skin Tissue Applications

Tissue engineering is transforming regenerative medicine by enabling the creation of functional tissue substitutes for in vitro research and therapeutic applications. Optimization of skin-engineered tissues would clearly be favored by local, real-time, and precise oxygen concentration measurements, as oxygen plays a fundamental role in cellular metabolism, survival, and tissue regeneration. This work presents a fluorescence-based oxygen biosensor that is chemically stable and integrated into fibrin-based dermal matrices used as scaffolds in complete skin equivalents (including dermis and epidermis). The process involves synthesizing PdPFP-Jeff, a modified porphyrin incorporating palladium and Jeffamine ED 600, and covalently bonding it to alginate modified with N-hydroxysuccinimide (AlgNHS), previously introduced within plasma-derived hydrogels that would form the skin construct in vitro. The chemical bonding enables stable incorporation, preventing leaching and maintaining structural integrity, while also ensuring biocompatibility with aqueous environments. Various biological assays, including live/dead assays, hematoxylin and eosin staining, and immunofluorescence studies, were conducted to confirm the biocompatibility of PdPFP-Jeff-enhanced dermoepidermal equivalents. When applied to hydrogels containing primary fibroblasts (dermal equivalents), this technique produced reliable results for these physiologically significant systems and demonstrated the potential of PdPFP-Jeff hydrogels as biosensors for real-time oxygen monitoring. By integrating high-resolution optical sensing into skin equivalents, this approach advances smart biomaterials, and improves in vitro skin models, and paves the way for enhanced wound healing and regenerative medicine applications.