Spatial Patterning of Modular Gelatin‐Peroxide Microspheres in Melt‐Electrowritten Scaffolds Provides Controlled Oxygen Generation and Mitigates Hypoxia and Cytotoxicity

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.