Janus Membranes as Multifunctional Nanostructures for Bone Defect Repair: Advances, Challenges, and Clinical Translation

Bone defect repair, particularly for critically sized defects, remains a formidable clinical challenge owing to the limitations of conventional bone grafts and single-functional scaffolds. Janus membranes, with their asymmetric structure and capacity for multi-functional integration, offer an innovative "all-in-one" solution for bone tissue engineering. This review systematically outlines recent advancements in Janus membranes for bone repair, focusing on three core aspects: nanofabrication strategies for achieving asymmetric properties (eg wettability, charge, and porosity), multi-functional designs that mimic the natural periosteum for guided bone regeneration, antibacterial activity, soft-tissue integration, and haemostasis, and clinical translation potential along with future perspectives. This review summarises the progress in the use of Janus membranes as multi-functional nanostructures for bone regeneration. It systematically introduces the manufacturing techniques for Janus membranes, such as the layer-by-layer method and ion-modification approaches. Furthermore, it focuses on the dual-functional and multi-functional designs of Janus membranes and their integration with nanotechnology. In addition, we delve into the current challenges (eg complexity in manufacturing processes and limited research on material mechanical properties) and propose potential solutions, such as intelligent manufacturing (eg 3D printing) and dynamic response systems. This review provides a comprehensive reference for the field and promotes the clinical translation of Janus membranes.