Corneal bioprinting using a high concentration pure collagen I transparent bioink

The use of 3D printing to produce a bioengineered cornea is emerging as an approach to help alleviate the global shortage of donor corneas. Collagen Type 1 (Col-1) is the most abundant collagen in the human cornea. However, Col-I presents challenges as a bioink. It can self-assemble at neutral pH, making phase transitions as required for 3D printing difficult to control. Furthermore, low concentration solutions required for the transparency of printed Col-I lead to weak mechanical properties in its printed structures. In this study, Col-I at high concentrations, was tested with 15 different solutions to identify the composition preventing Col-I self-assembly. A stable Col-I bioink was then developed using riboflavin as a photoinitiator and UV irradiation-induced crosslinking. The mechanical properties and transparency, of the structures produced, were evaluated. The optimised Col-I bioink with corneal stromal cells was tested using a spiral printing method. The printed structure was transparent, and the encapsulated corneal stromal cells had over 90% viability after three weeks of culturing.