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Mechanically Robust Shape Memory Polyurethane Nanocompositesfor Minimally Invasive Bone RepairYuanchi Zhang,†Jinlian Hu,*,†,‡Xin Zhao,§Ruiqi Xie,†Tingwu Qin,?and Fenglong Ji?†Institute of Textiles and Clothing, The Hong Kong Polytechnic University, Hung Hom, Hong Kong 999077, China‡Smart Biomaterial Research Center, The Hong Kong Polytechnic University, Shen Zhen Base, Hong Kong 999077, China§Department of Biomedical Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong 999077, China?Institute of Stem Cell and Tissue Engineering, West China Hospital, Sichuan University, Chengdu 610065, China?School of Textiles Materials and Engineering, Wuyi University, Jiangmen 529020, China*SSupporting InformationABSTRACT:Shape memory polymers (SMPs) have great potential utility in the area of minimally invasive surgery; however,insufficient mechanical properties hinder their applications for bone defect repair, particularly in high load-bearing locations. Inthis study, hydroxyapatite (HA)/reduced graphene oxide (rGO) nanofillers were incorporated into a shape memorypolyurethane (SMPU) to enhance its mechanical properties. Then the nanocomposite was further modified using arginyl-glycyl-aspartic acid (RGD peptide) to improve its cellular adhesion toward promoting neotissue formation and integration withsurrounding bone tissue. The physical and biological properties in terms of their chemical structure, surface wettability,mechanical behaviors, shape memory performance, and cell adhesion were systematically investigated. The results demonstratedthat the multimodified SMPU/HA/rGO/RGD nanocomposite significantly enhanced mechanical properties (e.g.,?200%increase in Young’s modulus and >300% enhancement in tensile strength compared with the unmodified SMPU), which mightbe attributed to the intercalated structure and metal affinity inside the nanocomposite. Adhesion of rabbit bone mesenchymalstem cells was clearly demonstrated on an RGD-immobilized SMPU nanocomposite surface. With an excellent shape memorybehavior (e.g., 97.3% of shapefixity ratio and 98.2% of shape recovery ratio), we envision that our SMPU/HA/rGO/RGDnanocomposite can be implanted into a bone defect with a minimally invasive surgery