A novel PCL fiber membrane with a gradient structure for guided bone regeneration

Guided bone regeneration (GBR) requires membranes that act as a physical barrier while also supporting osteogenesis. Conventional bilayer membranes, which typically consist of two discrete layers with an abrupt interface, are usually difficult to meet clinical requirements due to mechanical mismatch and delamination at the abrupt interface. To overcome these limitations, we developed a one-step fabrication strategy to prepare a polycaprolactone (PCL) fiber membrane with a continuous gradient in porosity and fiber orientation controlled by the combination of humidity and collection speed during the electrospinning process. The fabricated PCL fiber membrane smoothed the interface and eliminated the inherently weak interfacial region of traditional bilayer membranes, resulting in a 2.4-fold higher peel strength, a 2.42-fold higher tensile strength, and an approximately 55% reduction in cell stacking. Furthermore, cells at the non-porous, directional fiber surface of the gradient membrane exhibited a spindle-shaped, shallow adhesion morphology, while cells at the porous random fiber surface displayed a spread, stellate-radial adhesion morphology with an infiltration depth more than 2.4 times greater than that in the non-porous region. Simultaneously, the gradient structure increased collagen and calcium deposition and enhanced the expression of osteogenic genes. This work presents a novel gradient structure GBR membrane that integrates superior mechanical properties with bidirectional cellular regulation to enhance bone repair.