Fabrication of anisotropic nanocomposite hydrogels by magnetic field‐induced orientation for mimicking cardiac tissue

The ordered structure of biological tissues is a precondition for the development of high performance in these tissues. Hydrogels with anisotropic structures provide a good starting point for studying their biomimetic applications. In this work, a hydrogel that mimics the endogenous anisotropic structure of heart tissue was reported. The gel consists of acrylamide (AM) and 2-Acrylamide-2-methylpro panesulfonic acid (AMPS) as gel monomers, alpha-ketoglutaric acid as photoinitiator, and modified magnetic nanoparticles (Fe3O4-R-S) as crosslinking agent. Thus, AM, AMPS and Fe3O4-Rs was called AAF for short. In the system, the orientation of Fe3O4-Rs was arranged by an external magnetic field. Under ultraviolet (UV) irradiation, the precursor solution was polymerized in situ to form an AAF hydrogel. The structure, pore distribution, rheological properties, mechanical performance, swelling property, and biocompatibility of the prepared anisotropic AAF hydrogel were studied in this paper. Results showed that the mechanical performance of the AAF hydrogels was remarkably enhanced in comparison with the isotropic ones. The tensile strength of AAF hydrogel could reached 184 kPa in the direction of the parallel Orientation of Fe3O4-Rs, and 80 kPa in the direction of the vertical Orientation of Fe3O4-Rs under 25% strain (no magnetic field was applied during all test). Moreover, the anisotropic tensile ratio of AAF hydrogel also reached 2.3. The strength and modulus of anisotropic hydrogels were similar to cardiac tissue (anisotropic tensile ratio was 2.5), which has great potential for application in cardiac tissue engineering.