Digital Light Processing-Based 3D Printing of Cell-Seeding Hydrogel Scaffolds with Regionally Varied Stiffness

Cell-seeding heterogeneous scaffolds with regionally varied stiffness play an important role in tissue engineering, e.g., bone and cartilage regeneration, that require the recapitulation of geometric complexity through biocompatible material to mimic the natural cell microenvironment in vivo. Here, we report the digital light processing (DLP)-based 3D printing of cell-seeding hydrogel scaffold with regionally varied stiffness by tuning the exposure time without changing the geometric architecture. Mechanical tests on printed poly(ethylene glycol) diacrylate (PEGDA) hydrogels homogeneous scaffold revealed that a 60% increase in the elastic modulus can be achieved by setting the optimal exposure time. Furthermore, regulating the stiffness by varying the exposure time was demonstrated in the printed three-sectional heterogeneous scaffolds. Uniaxial compression tests showed that no fracture was observed even when the compression strain reached up to 25%, indicating that by adjusting the exposure time, the undesired influence of the scaffold on mechanical integrity could be avoided. 3T3 fibroblasts were then seeded onto the scaffold, and the biocompatibility together with the physical support of the scaffolds were confirmed by observation and cell population assessment.