Poly-L-lactide surfaces subjected to long-term cell cultures: cell proliferation and polymer degradation

Short term cell cultures are usually grown in contact with biomaterials to assess cytocompatibility. Depending on the rate of material degradation or corrosion, the time of culture can be a key-point in the method which, if too short, may not show any effect of the released material on the cells. A long term culture was therefore carried out with L929 fibroblast cells in contact with PLLA/PDLA samples for up to eight months. The degradation was measured in terms of shear-strength properties, intrinsic viscosity of the material and its cristallinity. The effect of the material on the cells was evaluated by measuring the growth rate of the cells. A significant decrease in the shear strength of the material was measured after three months. The rate of modification of the intrinsic viscosity was regular and decreased progressively throughout the culture period. Differential scanning calorimetry showed that the samples were initially essentially amorphous and that contact with the cell culture and its medium did not change its crystallinity level. The growth rate of the cells was not modified by the presence of the material when compared to the control. This study showed this material to be cytocompatible for a long period of time, even after detection of modifications of its physico-chemical properties.