Indirect 3D bioprinting and characterization of alginate scaffolds for potential nerve tissue engineering applications

Low-concentration hydrogels have favorable properties for many cell functions in tissue engineering but are considerably limited from a scaffold fabrication point of view due to poor three-dimensional (3D) printability. Here, we developed an indirect-bioprinting process for alginate scaffolds and characterized the potential of these scaffolds for nerve tissue engineering applications. The indirect-bioprinting process involves (1) printing a sacrificial framework from gelatin, (2) impregnating the framework with low-concentration alginate, and (3) removing the gelatin framework by an incubation process, thus forming low-concentration alginate scaffolds. The scaffolds were characterized by compression testing, swelling, degradation, and morphological and biological assessment of incorporated or seeded Schwann cells. For comparison, varying concentrations of alginate scaffolds (from 0.5% to 3%) were fabricated and sterilized using either ultraviolet light or ethanol. Results indicated that scaffolds can be fabricated using the indirect-bioprinting process, wherein the scaffold properties are affected by the concentration of alginate and sterilization technique used. These factors provide effective means of regulating the properties of scaffolds fabricated using the indirect-bioprinting process. Cell-incorporated scaffolds demonstrated better cell viability than bulk gels. In addition, scaffolds showed better cell functionality when fabricated with a lower concentration of alginate compared to a higher concentration. The indirect-bioprinting process that we implemented could be extended to other types of low-concentration hydrogels to address the tradeoffs between printability and properties for favorable cell functions.