Substrate Fluidity Regulates Cell Adhesion and Morphology on Poly(ε-caprolactone)-Based Materials

Although mechanostructural signals from the surrounding matrix have been known to regulate cell functions, the effects of substrate fluidity are poorly understood. Here, we demonstrate that the adhesion and morphology of cells are regulated by the fluidity on widely used biodegradable polymer substrates, rather than the substrate elasticity. We have designed cell culture films with different elasticity and fluidity using poly(epsilon-caprolactone-co-D,L-lactide) (CL-DLLA). The elasticity was successfully controlled by adjusting the amorphous crystal phase transition temperature (T-m) of CL-DLLA without changing the surface wettability; i.e., the CL-DLLA displays more viscous (liquidlike) behavior at 37 degrees C with increasing DLLA contents. The fluidity was varied by chemically cross-linking the polymer networks. This CL-DLLA system was used to test the effect of variations in a substrate's fluidity on cell behavior. Differences were observed in adhesion, spreading and morphology of NIH 3T3 fibroblasts. Increasing the fluidity decreased cell spread area but enhanced the formation of spheroids. Although direct comparison of the elastic modulus between cross-linked and non-cross-linked samples are difficult, it was found that the substrate stiffness produced little changes in cell spread area, indicating that cells sense more dynamic nature of their surrounding environment. These findings will serve as the basis for new development of tissue engineering scaffolds and engineered stem cell niche as well as investigation of dynamic effects of mechanostructural stimuli on cell fate.