Robust and double-layer micro-patterned bioadhesive based on silk nanofibril/GelMA-alginate for stroma tissue engineering.

We develop a robust micro-patterned double-layer film that can adhere firmly to the tissue and provide a sustained release of ascorbic acid (AA) for corneal regeneration. This double-layer film consists of a AA reservoir sodium alginate (SA) adhesive and an anisotropic layer made of micro-patterned silk nanofibrils (SNF) incorporated gelatin methacrylate (GelMA) (S/G). The S/G layer facilitates the adhesion and orientation of corneal stroma cells, depending on the pattern sizes (50 μm (P1) and 100 (P2) μm). Results reveal that more than 90% and 80% of the cells are located at angles close to the vertical axis (0-20°) in the sample with the smaller and larger pattern size, respectively. The mechanical robustness and 90% light transmission of this hybrid film originate from the micro-patterned S/G layer. However, the micro-pattern size does not show a significant role in the mechanical properties of hybrid films (tensile strength of S/G-SA, S/G-SA(P1), and S/G-SA(P2) is 3.4 ± 0.1 MPa, 3.6 ± 0.6 MPa and 3.3 ± 0.2 MPa, respectively). In addition, the strong adhesion to the tissue of this double-layer film is related to the alginate layer. AA can release in a controlled manner, which can significantly promote corneal stroma cells' attachment, alignment, and proliferation compared to the control (AA-free micro-patterned film). Our results reveal that this innovative multifunctional S/G-SA + AA film can be a proper candidate for use in stroma tissue engineering of the human cornea.