Spatial Patterning of Modular Gelatin-Peroxide Microspheres in Melt-Electrowritten Scaffolds Provides Controlled...

Access to oxygen within tissue engineered hydrogel scaffolds is essential to promote cell survival, especially in large tissue constructs. One promising approach to deliver oxygen (O₂) relies on the decomposition of calcium peroxide (CaO₂), which generates molecular oxygen via hydrogen peroxide (H₂O₂) as an intermediate. However, generated oxygen interferes with radical-based hydrogel crosslinking, and the formation of cytotoxic H₂O₂ affects cell viability. In this study, materials engineering and bioassembly principles are applied to harness the oxygen generation capability of CaO₂, while mitigating the negative effects on crosslinking efficacy and cellular health. First, the use of a recyclable photoinitiator platform and thiol-ene clickable gelatin to reduce radical oxygen inhibition and improve crosslinking efficacy is systematically investigated. Next, microparticles containing CaO₂ or human mesenchymal stromal cells are bioassembled within a melt electrowritten (MEW) scaffold. By controlling the relative organization of particles within the MEW scaffold, we are able to circumvent the traditional challenges associated with H₂O₂ cytotoxicity, while oxygen production allows for cell survival under hypoxia (1% O₂) for up to 5 days. This bioassembly approach thus facilitates the application of CaO₂ as an effective oxygen generator within large tissue engineered constructs without traditional design constraints associated with crosslinking efficacy and toxicity.