Zwitterionic hydrogel is one of the most promising cartilage repair and replacement materi-als with good biocompatibility and anti-bacteria adhesion properties.However,there is a certain gap in-volving in mechanical properties compared to natural cartilage,which greatly limits its practical applica-tion.Herein,the nano-hydroxyapatite was modified with dopamine by acid,and alkali conditions respec-tively to obtain a nanoparticle-modified composite hydrogel.It is found that an oxide film could form on the surface of nano hydroxyapatite modified by dopamine,and the benzene ring in the modified nano par-ticles is combined to form a covalent bond with the zwitterionic hydrogel polymer chain.Meanwhile,dopa-mine improves the dispersity of nano-hydroxyapatite by acidic condition,thereby enhancing the thermal stability of zwitterionic hydrogel(decomposing until 323℃),as well as its network structure strength(ener-gy storage modulus of 2.7 MPa)and internal friction capacity(loss factor of 0.041).Moreover,the com-pressive strength of acid nanocomposite hydrogel arrives at 11.66 MPa,which is 32 times higher than that of pure PSBMA zwitterionic hydrogel.Thus,the structural characteristics and mechanical properties of acid nanocomposite hydrogels are similar to those of natural cartilage,which provides a significant ref-erence for the design and preparation of bionic materials.
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