Bilayer Scaffold for Corneal Stromal Engineering: Solvent-Cast Polyvinyl Alcohol/Sodium Alginate and Electrospun Aligned Polycaprolactone Fibers.

Due to their limited functional range, single-layer engineered scaffolds often fall short of meeting the complex clinical requirements for corneal stromal engineering (CSE). To overcome these challenges, bilayer constructs that integrate complementary material properties have emerged as promising alternatives. In this study, we developed a bilayer membrane by electrospinning polycaprolactone (PCL) fibers onto a solvent-cast polyvinyl alcohol/sodium alginate (PVS) membrane. The dense PVS layer provided a smooth, crack-free surface with favorable physicochemical and thermal stability. In contrast, the PCL nanofibrous layer (232 ± 44 nm) exhibited a continuous, bead-free, and highly aligned morphology. Comprehensive characterization confirmed the structural integrity of the bilayer scaffold, which showed two distinct thermal transitions (~65 °C for PCL and ~225 °C for PVS), confirming good stability and minimal interfacial disruption. Functionally, the PCL-PVS bilayer scaffold demonstrated an intermediate contact angle (57.44°), high water uptake capacity (424.44%), and a high gel fraction (96.12%), along with controlled biodegradation (39.65%), highlighting its suitability for physiological environments. Mechanical testing revealed a Young's modulus of 2.60 ± 0.20 megapascals (MPa), an ultimate tensile strength (UTS) of 5.74 ± 0.02 MPa, and an elongation at break of 3.32 ± 0.10%, values well aligned with the mechanical demands of corneal tissue. Additionally, the construct achieved 85.01% light transmittance, essential for visual clarity, and supported measurable cell viability, although additional optimization is required to further enhance cytocompatibility. These findings demonstrate that the bilayer combines structural stability, favorable physicochemical performance, transparency, and biological compatibility, positioning it as a promising platform for further optimization toward CSE.