Carrageenan blended protein bioink with improved printability of extrusion-based 3D printing

초록

Bioprinting has shown a high potential for manufacturing constructs for culturing diverse cells in the 3D environment. As of today, many synthetic polymers have been printed into diverse soft tissue scaffolds. However, some still require harsh printing conditions, which limits the direct printing of live cells. In this sense, natural polymer-based bioink printing under mild temperatures and pressures is expected to solve these problems if it overcomes some challenges related to low viscosity, slow gelation rate, and poor mechanical properties. Here, silk fibroin(SF) and iota-carrageenan(CG) blend were chosen as a stimulus-reactive bioink material to surmount some restrictions. SF has durable mechanical properties due to its dominant β-sheet conformations, and for CG, it has a thermo-responsive property that promotes gelation around 22℃ from the 60°C-heated liquid solution. As the resulting SF/CG ink had shear-thinning properties and an adequate viscosity (~262.5 Pa·s within the shear rate of 0.2-0.6 s-1) for extrusion printing, at first, crosslinking of CG was induced by temperature change. However, the only physically crosslinked SF/CG ink could not sustain its structural integrity during ink deposition. Layer stackability with high printing resolution and further stabilization of printed 3D constructs was achieved in a second process by photo-crosslinking SF under visible light within 5 seconds. Printed constructs with Young’s modulus ~250 kPa were obtained and compared with that of the specific tissue cell types, including skin(20-250 kPa), bladder(140-526 kPa), and central cornea(86-700 kPa). This dual crosslinking strategy is beneficial for the adequate extrudability and printing resolution and the durable structural integrity of 3D construct. Moreover, these results presented that the SF/CG-blends would be a cell-favorable bioink, which is suitable for extrusion-based bioprinting.