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.

A Stable Large Animal Model for Dural Defect Repair with Biomaterials and Regenerative Medicine.

IMPACT STATEMENT: Using biomaterials and regenerative medicine to repair tissue defects has been a very hot research field, during which the development of stable large animal models with appropriate biotechnology is crucial. Recently, more and more researchers are paying attention to dural defect repair. However, the lack of widely recognized stable large animal models has seriously affected the related further research. In this study, a stable large animal dural defect model is developed exactly for the first time. Therefore, the article would attract considerable attention and be highly cited after publication.

Efficacy and safety of small intestinal submucosa in dural defect repair in a canine model.

Dural defects are a common problem, and inadequate dural closure can lead to complications. Several types of dural substitute materials have recently been discarded or modified owing to poor biocompatibility or mechanical properties and adverse reactions. The small intestinal submucosa (SIS) is a promising material used in a variety of applications. Based on the limitations of previous studies, we conducted an animal study to evaluate the efficacy and safety of the SIS in preclinical trials. Twenty-four male beagle dogs were subjected to surgical resection to produce dural defects. SIS or autologous dural mater was patched on the dural defect. Gross and histological evaluations were carried out to evaluate the efficacy and safety of the therapy. Our findings demonstrated that the SIS, which stimulated connective and epithelial tissue responses for dural regeneration and functional recovery without immunological rejection, could provide prolonged defect repair and prevent complications. The mechanical properties of the SIS could be adjusted by application of multiple layers, and the biocompatibility of the material was appropriate. Thus, our data suggested that this material may represent an alternative option for clinical treatment of dural defects.