Hierarchically engineered collagen composite membrane for enhanced corneal repair

Corneal defects pose a significant threat to visual function, underscoring the need for advanced transplantable artificial corneas. Collagen-based biomimetic scaffolds offer a promising avenue for corneal regeneration. However, the impact of collagen's hierarchical architecture on scaffold properties and its role in corneal healing remains incompletely understood. In this study, we systematically compared two distinct high-density collagen membranes: a fibrous collagen membrane (FCM), fabricated via thermally controlled vitrification to induce collagen self-assembly, and a non-fibrous collagen membrane (NFCM), prepared by chemical crosslinking followed by vitrification drying. The FCM dried at 37 °C exhibited well-aligned collagen fibrils and lamellar organization, along with thermal stability, hydration capacity, and mechanical behavior closely resembling those properties of the native cornea. In contrast, the NFCM, while mechanically brittle, possessed a smooth surface that markedly promoted epithelial cell migration. Leveraging these distinct properties, we constructed a bilayer collagen composite comprising an upper NFCM layer and a lower FCM layer, designed to synergistically facilitate rapid epithelial wound closure and robust stromal integration, respectively. Our findings underscore the pivotal role of collagen microstructure in determining the mechanical, optical, and biological performance of corneal scaffolds, and provide a rational design strategy for developing hierarchically structured collagen membrane composites with translational potential for corneal repair.