Polymerization induced phase separation as a generalized methodology for multi-layered hydrogel tubes

Herein, we report a conceptually chemical strategy to facilitate the fabrication of layered hydrogel tubes based on the polymerization-induced phase separation mechanism. In a typical case, a high purity iron wire is immersed into a sodium alginate (SA) saturated 2-hydroxyethyl methacrylate (HEMA) monomer solution to perform Surface Catalytically Initiated Radical Polymerization (SCIRP), followed by Ca²⁺ post-crosslinking. Subsequently, the successful removal of the iron wire template enables the formation of a hollow PHEMA/SA-Ca²⁺ layered hydrogel tube. The layered hydrogel tubes can be prepared with tunable sizes, good tensile strength, perfusable 3D complex structure and minimal cytotoxicity. Multi-layered hydrogel tubes can be obtained as well on the basis of monomers diffusion and re-initiation mechanism, which may address the demands for tissue manufacturing. Finally, the bioactivity of the PHEMA/SA-Ca²⁺ layered hydrogel tube is proved by the surface adhesion and proliferation of two types of cells-NIH3T3 and PAECs on the inner side of the layered hydrogel tubes.