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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. In this study, hydroxyapatite (HA)/reduced graphene oxide (rGO) nanofillers were incorporated into a shape memory polyurethane (SMPU) to enhance its mechanical properties. Then the nanocomposite was further modified using arginyl-glycylaspartic acid (RGD peptide) to improve its cellular adhesion toward promoting neotissue formation and integration with surrounding 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 demonstrated that 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 might be attributed to the intercalated structure and metal affinity inside the nanocomposite. Adhesion of rabbit bone mesenchymal stem cells was clearly demonstrated on an RGD-immobilized SMPU nanocomposite surface. With an excellent shape memory behavior (e.g., 97.3% of shape fixity ratio and 98.2% of shape recovery ratio), we envision that our SMPU/HA/rGO/RGD nanocomposite can be implanted into a bone defect with a minimally invasive surgery.

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Electrically actuated ankle-foot orthoses (AFOs) were designed and prototyped using shape memory textile composites. Acrylic copolymers were synthesized as the matrix to demonstrate shape memory effects, whereas electrothermal fabrics were embedded to generate uniform heat as a trigger. Superior to conventional polymeric orthoses, shape memory AFOs (SM-AFOs) could be repeatedly programmed at least 20 times with stable shape fixity and recovery. Evidenced by clinical practice, SM-AFOs were effectively actuated at 10 V, allowing the correction of ankle angles with 10° plantarflexion. Ultimately, we envision a smart orthopedic system that can advance progressive rehabilitation with manipulation under safe and convenient conditions.

No abstract