Entangled Polymer Surface Confinement, an Alternative Method to Control Stem Cell Differentiation in the Absence of Chemical Mediators

We have demonstrated that the moduli of spun cast and annealed polybutadiene films can be enhanced by nearly an order of magnitude, due to confinement near an attractive HF etched Si substrate interface. The region of enhancement scaled with the polymer radius of gyration and persisted for distances greater than twenty times the radius of gyration of the polymer, Rg, from the Si interface. We also showed that dental pulp stem cells (DPSC) can be plated directly on these films without any additional coatings and that the DPSCs were able to adjust their moduli in a continuous manner in response to that of the substrate. A critical value of the substrate modulus, Mc= 2.3MPa was found which was independent of substrate molecular weight or thickness, such that for substrates with moduli M>Mc, the DPSC were induced to produce hydroxyapatite mineral deposits and upregulate gene expression of osteocalcin (OCN) and alkaline phosphatase (ALP), in the absence of any other soluble factors.