Cell adhesion and proliferation on biomimetic calcium-phosphate coatings produced by a sodium silicate gel methodology

The present study describes a methodology to produce bioactive coatings on the surface of starch based biodegradable polymers or other polymeric biomaterials. As an alternative to the more typical bioactive glass percursors, a sodium silicate gel is being employed as a nucleating agent, for inducing the formation of a calcium-phosphate (Ca-P) layer. The method has the advantage of being able to coat efficiently both compact materials and porous 3D architectures aimed at being used on tissue replacement applications and as bone tissue engineering scaffolds. This treatment is also very effective in reducing the incubation periods, being possible to observe the formation of an apatite-like layer, only after 6h of immersion in a simulated body fluid (SBF). The influence of the SBF concentration on the formation of the apatite coating was also studied. The apatite coatings formed under different conditions were analyzed and compared in terms of morphology, chemical composition and structure. After the first days of SBF immersion, the apatite-like films exhibit the typical cauliflower like morphology. With increasing immersion times, these films exhibited a partially amorphous nature and the Ca/P ratios became very closer to the value attributed to hydroxyapatite (1.67). The obtained results are very promising for pre-calcifying bone tissue engineering scaffolds. Therefore, in order to study cell behavior and response to these apatite coatings, adhesion, morphology, and proliferation of a human osteoblast cell line (SaOS-2) was also analyzed after being cultured in the coatings formed after 15 days of immersion in SBF. Results indicate a good correlation between crystallinity of the apatite like coatings formed in these conditions and respective cell spreading and morphology. In general, higher cell proliferation was observed for higher crystalline Ca-P coatings.