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.