In-situ AFM study of the mechanisms involved on calcium-phosphate film formation on partially crystallized bioglass and on hydroxylapatite immersed in a simulated body fluid

摘要

The present work investigates in-situ using atomic force microscopy (AFM) the in-vitro binactivity of partially crystallized 45S5 Bioglass as a function of immersion time in a simulated body fluid (SBF). The results obtained for partially crystallized Bioglass were compared to those of hydroxyapatite c- and a-faces. The calcium phosphate layer grows on the crystallized 45S5 BG by multiple two-dimensional nucleation and fusion of these two-dimensional nuclei, which is essentially the same mode as for the hydroxyapatite c-face. However, the lateral growth rate of nucleus on the crystallized BG is 10-17 times and 390-570 times higher than that on hydroxyapatite c-face and a-face, respectively. The surface of the crystallized 45S5 BG was fully covered with a dense and compact layer of spherical particles after 24 hours. The promotion of calcium phosphate formation on the crystallized BG arises from a low surface energy of the surface layer and/or an effect of the layer to lower the resistance when the growth units of calcium phosphate incorporate into the growing island. These results indicate that the crystallized 45S5 BG is suitable to be used as a filler for polymeric matrix bioactive composites, as it maintains a high bioactivity associated to a stiffer behaviour (as compared to standard Bioglass).