Development and Assessment of Poly(ethylene glycol) Diacrylate-Embedded Metalloporphyrin for Phosphorescence Lifetime-Based In Vivo Monitoring of Oxygen Tension

The timely detection of ischemia is crucial for enhancing outcomes in reconstructive surgery. This study presents the development and in vivo evaluation of a metalloporphyrin-based phosphorescence lifetime oxygen sensor embedded in poly(ethylene glycol) diacrylate (PEGDA) hydrogel for monitoring local tissue oxygen tension (TOT). Palladium(II) tetraphenyltetrabenzoporphyrin was incorporated into microporous PEGDA hydrogels using polystyrene to facilitate dispersion and enhance photophysical properties. Sensors were calibrated under controlled oxygen conditions and characterized for oxygen-dependent phosphorescence lifetime response. In vivo performance was assessed using rat flap models and a swine tongue ischemia model. Implant localization and local tissue response were evaluated using luminescence imaging and histological analysis. The sensors demonstrated an inverse relationship between phosphorescence lifetime and pO2, with a dynamic response to experimentally varied oxygen conditions. In vivo, the sensors detected regional oxygen differences associated with ischemia and areas that later developed tissue necrosis in flap models. In the rat pedicle flap model, a decrease in oxygenation was detected within approximately 70 s of vascular clamping. In the swine tongue model, sensors detected acute oxygenation changes during vascular compromise and partial recovery after tourniquet release and tongue massage. Implants remained localized without visible migration, and histological analysis showed no granulomatous inflammation or multinucleated giant-cell reaction over the 28-day study period. This injectable PEGDA-embedded metalloporphyrin sensor enables non-invasive phosphorescence lifetime-based monitoring of local tissue oxygen tension after implantation. Its oxygen-responsive lifetime behavior, short-term positional stability, and proof-of-concept ischemia detection support further development as a localized monitoring tool for surgical tissue viability.