Tuning of ion-release capability from bio-ceramic-polymer composites for enhancing cellular activity

In our previous study, we investigated the synergetic effects of inorganic ions, such as silicate, Mg²⁺ and Ca²⁺ ions on the osteoblast-like cell behaviour. Mg²⁺ ions play an important role in cell adhesion. In the present study, we designed a new composite that releases a high concentration of Mg²⁺ ions during the early stage of the bone-forming process, and silicate and Ca²⁺ ions continuously throughout this process. Here, 40SiO₂-40MgO-20Na₂O glass (G) with high solubility and vaterite-based calcium carbonate (V) were selected as the source of silicate and Mg²⁺ and Ca²⁺ ions, respectively. These particles were mixed with poly(lactic-co-glycolic acid) (PLGA) using a kneading method at 110°C to prepare the composite (G-V/PLGA, G/V/PLGA = 4/56/40 (in weight ratio)). Most of the Mg²⁺ ions were released within 3 days of immersion at an important stage for cell adhesion, and silicate and Ca²⁺ ions were released continuously at rates of 70-80 and 180 ppm d^-1, respectively, throughout the experiment (until day 7). Mouse-derived osteoblast-like MC3T3-E1 proliferated more vigorously on G-V/PLGA in comparison with V-containing PLGA without G particles; it is possible to control the ion-release behaviour by incorporating a small amount of glass particles.