Gas diffusion-mediated single-sided in situ gradient mineralized silk fibroin membrane for enhanced guided bone regeneration.

Traditional guided bone regeneration (GBR) membranes face challenges in balancing mechanical strength, bioactivity, and osteoconductivity for effective periodontal bone regeneration. While collagen-based GBR membranes dominate clinical use, the weak mechanical properties and lack of osteoinductive capacity limit regeneration efficacy. Here, we presented a gas diffusion-mediated single-sided mineralization strategy to fabricate silk fibroin (SF)-based GBR membranes with dual barrier/osteoinductive functions. SF was dissolved in formic acid with Ca^2 + and, optionally, other bioactive metal ions (BMIs, such as Sr²⁺, Cu²⁺, or Mg²⁺), and a colloid was formed after the evaporation of formic acid. Followed by gradient mineralization under CO₂/NH₃ atmosphere and β-sheet induction via ethanol treatment, SF-Ca/X (X refers to other BMIs) membranes were prepared. Mineralized SF membranes featured a dense, mineral-free side for mechanical support and barrier, and an osteoinductive side by releasing BMIs. Interestingly, the calcium phosphate layer formed on the mineralized side, and the phase of CaCO₃ changed from calcite to vaterite, which helps phosphate mineralization. In vitro results demonstrated that the SF-Ca/Sr membrane enhanced osteogenic differentiation by upregulating BMP2/SMAD1 expression. In a rat mandibular defect model, the SF-Ca/Sr membrane significantly promotes new bone regeneration and collagen formation. Overall, this gas diffusion-mediated single-sided gradient mineralization approach integrates barrier properties with localized bioactivity, allowing for the required barrier/osteoinduction functions in the GBR process in one membrane.