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.

3D-printed NIR-responsive shape memory polyurethane/magnesium scaffolds with tight-contact for robust bone regeneration.

Patients with bone defects suffer from a high rate of disability and deformity. Poor contact of grafts with defective bones and insufficient osteogenic activities lead to increased loose risks and unsatisfied repair efficacy. Although self-expanding scaffolds were developed to enhance bone integration, the limitations on the high transition temperature and the unsatisfied bioactivity hindered greatly their clinical application. Herein, we report a near-infrared-responsive and tight-contacting scaffold that comprises of shape memory polyurethane (SMPU) as the thermal-responsive matrix and magnesium (Mg) as the photothermal and bioactive component, which fabricated by the low temperature rapid prototyping (LT-RP) 3D printing technology. As designed, due to synergistic effects of the components and the fabrication approach, the composite scaffold possesses a homogeneously porous structure, significantly improved mechanical properties and stable photothermal effects. The programmed scaffold can be heated to recover under near infrared irradiation in 60s. With 4 wt% Mg, the scaffold has the balanced shape fixity ratio of 93.6% and shape recovery ratio of 95.4%. The compressed composite scaffold could lift a 100 g weight under NIR light, which was more than 1700 times of its own weight. The results of the push-out tests and the finite element analysis (FEA) confirmed the tight-contacting ability of the SMPU/4 wt%Mg scaffold, which had a signficant enhancement compared to the scaffold without shape memory effects. Furthermore, The osteopromotive function of the scaffold has been demonstrated through a series of in vitro and in vivo studies. We envision this scaffold can be a clinically effective strategy for robust bone regeneration.

Robust Effects of Graphene Oxide on Polyurethane/Tourmaline Nanocomposite Fiber.

The use of energy therapy including tourmaline/negative ions has gained huge popularity due to their long-standing historical evidence in improving human health and the technology development. However, the limitations of tourmaline based polyurethane fibers including the unsatisfied mechanical properties and negative ions releasing performances hind their further applications for wearable energy therapy. In this study, graphene oxide was modified within the polyurethane/tourmaline nanocomposite and then the wet-spinning method was used to prepare the fibers. As expected, the results proved that polyurethane/tourmaline/graphene oxide fiber had enhanced Young's modulus (8.4 MPa) and tensile stain at break (335%). In addition, the number of released negative ions from polyurethane/tourmaline/graphene oxide fiber was significantly improved 17 times and 1.6 times more than that of neat polyurethane fiber and polyurethane/tourmaline fiber, respectively. Moreover, the releasing number of negative ions was significantly decreased after being applying voltage. We envision that the proposed polyurethane/tourmaline/graphene oxide fiber will provide valuable insights into the development of the wearable energy products.

Isocyanate Modified GO Shape-Memory Polyurethane Composite.

Shape-memory composites have benefits for minimally invasive surgery, but their wider applications for bone repair are hindered by conflicts between the mechanical and memory performances, especially at load-bearing locations. In this study, we fabricated a graphene oxide shape-memory polyurethane composite through the chemical combination of graphene oxide and isocyanate, in order to realize satisfactory mechanical and shape-memory effects. As desired, a modulus of ~339 MPa and a shape recovery ratio of 98% were achieved, respectively, in the composite. In addition, finite element analysis demonstrated that, after being implanted in a defective bone through a minimally invasive treatment, where the highest stress was distributed at the implant-bone interface, this composite could offer a generated force during the recovery process. Furthermore, we also discuss the origins of the improved mechanical and memory properties of the composites, which arise from increased net-points and the stable molecular structure inside. Therefore, with its superior structure and properties, we envision that this shape-memory composite can provide new insights toward the practical application of shape-memory polymers and composites in the field of bone repair.

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.

Mechanically Robust Shape Memory Polyurethane Nanocomposites for Minimally Invasive Bone Repair.

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-glycyl-aspartic 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.

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.

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.