Two-photon crosslinking in collagen hydrogel towards corneal tissue engineering

Corneal disease seriously threatens the quality of human vision and even causes blindness, but the shortage of corneal donors is insufficient to meet the demand for corneal transplantation. Artificial corneas prepared by hydrogel materials have the characteristics of high-water content, good biocompatibility and low cytotoxicity, is an effective way to treat corneal diseases. Although hydrogel technology has advanced over the past few years, their application often suffers from limitations in mechanical properties and complicated fabrication procedures. Here, a novel high-transparent and stiffness-enhanced bio-adhesive hydrogel composed of porcine type I collagen is developed by near infrared femtosecond laser based two-photon collagen crosslinking (CXL). Transmission spectra show that the transparency of the prepared hydrogel in the visible band is not less than 90 %, and the mechanical stiffness can be enhanced by 265.27 % ± 27.08 % without significantly reducing transparency after two-photon CXL. Additionally, the hydrogel’s microstructure offers insights into the reasons contributing to the observed improvement in the mechanical stiffness. Overall, this work presents a generalizable preparation strategy for hydrogel materials with high light transmission, mechanical strength, and also potential of biocompatibility and bioadhesion in terms of biocompatibility, that might be an excellent candidate for artificial cornea implants and will foster potential advances in soft materials.