Optimizing the Cross‐Linking of Poly(2‐oxazoline)‐Based Hybrid Microgels for Cell Encapsulation via Radiation‐free Thiol‐Michael‐Addition Reaction

Poly(2-oxazoline)s (POx) are an emerging class of synthetic polymers with potential in biomedical applications as most of them are characterized by biocompatibility, stealth properties, and structural tunability. Similarly, microgels gain attention for cell encapsulation, drug delivery, and as building blocks for physical hydrogels and tissue constructs. However, the predominant cross-linking methods for both POx and microgels rely on UV light and radicals, which can harm cells. This study aims to integrate the trends of POx and microgels and to overcome limitations of UV-based methods. It introduces a radiation-free cross-linking mechanism via thiol-Michael-addition for POx-based microgels, tailored for cell-friendly cell encapsulation. Therefore, a hybrid polymer system of thiolated POx, gelatin, and acrylated hyaluronic acid is chosen and its cross-linking kinetics is optimized for microfluidic procedures. Subsequently, hydrogels and microgels of different molar ratios of the functional groups are prepared. These differ in stiffness and degradation. Cell encapsulation tests with fibroblasts show cell viabilities >90% and that the gel systems support cell spreading and proliferation, irrespective of molar ratio. This confirms that the proposed cross-linking strategy is effective for creating POx-based microgels suitable for cell-friendly cell encapsulation.