Self-fitting shape memory polymer foam inducing bone regeneration: A rabbit femoral defect study.

Although tissue engineering has been attracted greatly for healing of critical-sized bone defects, great efforts for improvement are still being made in scaffold design. In particular, bone regeneration would be enhanced if a scaffold precisely matches the contour of bone defects, especially if it could be implanted into the human body conveniently and safely. In this study, polyurethane/hydroxyapatite-based shape memory polymer (SMP) foam was fabricated as a scaffold substrate to facilitate bone regeneration. The minimally invasive delivery and the self-fitting behavior of the SMP foam were systematically evaluated to demonstrate its feasibility in the treatment of bone defects in vivo. Results showed that the SMP foam could be conveniently implanted into bone defects with a compact shape. Subsequently, it self-matched the boundary of bone defects upon shape-recovery activation in vivo. Micro-computed tomography determined that bone ingrowth initiated at the periphery of the SMP foam with a constant decrease towards the inside. Successful vascularization and bone remodeling were also demonstrated by histological analysis. Thus, our results indicate that the SMP foam demonstrated great potential for bone regeneration.

Black phosphorus boosts wet-tissue adhesion of composite patches by enhancing water absorption and mechanical properties.

Wet-tissue adhesives have long been attractive materials for realizing complicated biomedical functions. However, the hydration film on wet tissues can generate a boundary, forming hydrogen bonds with the adhesives that weaken adhesive strength. Introducing black phosphorus (BP) is believed to enhance the water absorption capacity of tape-type adhesives and effectively eliminate hydration layers between the tissue and adhesive. This study reports a composite patch integrated with BP nanosheets (CPB) for wet-tissue adhesion. The patch's improved water absorption and mechanical properties ensure its immediate and robust adhesion to wet tissues. Various bioapplications of CPB are demonstrated, such as rapid hemostasis (within ~1-2 seconds), monitoring of physical-activity and prevention of tumour-recurrence, all validated via in vivo studies. Given the good practicability, histocompatibility and biodegradability of CPB, the proposed patches hold significant promise for a wide range of biomedical applications.

A programmable, fast-fixing, osteo-regenerative, biomechanically robust bone screw.

The use of a screw for repairing defected bones is limited by the dilemma between stiffness, bioactivity and internal fixation ability in current products. For polymer bone screw, it is difficult to achieve the bone stiffness and osteo-induction. Polymer composites may enhance bioactivity and mechanical properties but sacrifice the shape memory properties enormously. Herein, we fabricated a programmable bone screw which is composed of shape memory polyurethane, hydroxyapatite and arginylglycylaspartic acid to resolve the above problem. This composite has significantly improved mechanical and shape-memory properties with a modulus of 250 MPa, a shape fixity ratio of ~90% and a shape recovery ratio of ~96%. Moreover, shape fixity and recovery ratios of the produced SMPC screw in the simulative biological condition were respectively ~80% and ~82%. The produced screw could quickly recover to its original shape in vitro within 20 s leading to easy internal fixation. Additionally, the composite could support mesenchymal stem cell survival, proliferation and osteogenic differentiation in vitro tests. It also promoted tissue growth and showed beneficial mechanical compatibility after implantation into a rabbit femoral intracondyle for 12 weeks with little inflammation. Such bone screw exhibited a fast-fixing, tightened fitting, enhanced supporting and boosted bioactivity simultaneously in the defective bone, which provides a solution to the long-standing problem for bone repairing. We envision that our composite material will provide valuable insights into the development of a new generation of bone screws with good fixation and osteogenic properties. STATEMENT OF SIGNIFICANCE: The main obstacles to a wider use of a bone screw are unsatisfied stiffness, inflammatory response and screw loosening issues. Herein, we report a programmable screw with mechanically robust, bioactive and fast-fixing performances. The shape memory polymer composite takes advantage of the component in the natural bone and possesses a stable bush-like structure inside through the covalent bonding, and thus achieve significantly improved mechanical and memory properties. Based on its shape memory effect, the produced screw was proved to offer a recovery force to surroundings and promote the bone regeneration effectively. Therefore, the composite realizes our expectations on functions through structure design and paves a practical and effective way for the development of a new generation of bone screws.

Shape Memory Ankle-Foot Orthoses.

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.