Tetraethyl silicate

All precursors were reactive grade and used without further purification. The method was performed in two steps. In the first step, tetraethyl silicate (98% Sigma-Aldrich ^®, Michoacán, México) and 0.1 M nitric acid (JT Baker ^®, Michoacán, México) were mixed at room temperature. Then, triethyl phosphate (TEP: 99.8%, Sigma-Aldrich ^®, Michoacán, México) and calcium nitrate tetrahydrate (99%, Sigma-Aldrich ^®, Michoacán, México) were added at intervals. The reaction lasted for an additional hour after the last compound was added. The bioactive glass was obtained in this step. The general synthesis reactions can be observed in Equation (1). In the second step, the material obtained as a gel form was mixed with the PLA obtained in two weight percentages (wt.%), namely, BG30-PLA70 and BG70-PLA30, employing dissolvent propanone (Meyer ^®, Michoacán, México). The composite biomaterial was first kept in a sealed glass jar at room temperature for ten days and later at 70 °C for three days. Thermal treatment was performed at 120 °C for two days.
$$Si{C}_8{H}_{20}{O}_4\stackrel{HN{O}_{3 }0.1 M}{\to }Si{\left(OH\right)}_4\stackrel{TEP, Ca{(N{O}_3)}_2.4H_{2}O}{\to } {(Si{O}_2)}_x {(CaO)}_y{(P_2{O}_5)}_z$$