Microstructures in 3D biological gels affect cell proliferation

Controlling the microscale environment in three-dimensional (3D) matrices for tissue engineering applications is a challenging but necessary goal. In this work, the effect of discrete microscale structures (microrods) on cell proliferation was assessed in 3D gels. Microrods were fabricated out of SU-8 with dimensions of 100 x 15 x 15 microm (L x H x W) and incorporated into Matrigel seeded with fibroblasts. The 3D microrod-Matrigel composite system inhibited proliferation of both primary and cell-line fibroblasts compared to cells seeded in Matrigel alone. To rule out bulk mechanical effects, the bulk shear modulus (G') and loss modulus (G") were assessed between 0.1 and 5 Hz for both Matrigel and microrod-Matrigel composites. The incorporation of microrods did not change the bulk stiffness of the gel. Moreover, it was determined that the chemistry of the microrod material itself did not inhibit cell proliferation. Therefore, results indicate that the presence of suspended microscale structures in three dimensions can regulate cell proliferation in a dose-dependent manner. This system provides a biocompatible, long-term way to modulate cell growth in 3D cultures and is amenable to in vivo applications.