The membranes were immersed in SBF to assess their weight loss (%) and pH change (n = 5/group/time point). The pH change from the baseline pH of the SBF was measured using the pH meter (SevenCompact, Mettler Toledo GmbH, Greifensee, Switzerland). Then, the 10 mm × 10 mm membrane specimens were immersed in 4 mL of SBF/tube in 50 mL centrifuge tubes (Corning, Merck KgaA, Darmstadt, Germany). The tubes were incubated at 37 °C, and the pH of the solution of each membrane was measured on days 1, 3, 7, 14, and 21. The control group consisted of a solution without membranes. To measure the weight loss, each membrane was weighed (Wd0) using an analytical balance (Satorius, Goettingen, Germany) before immersion in 4 mL of SBF/well in 12-well plates (Corning, Merck KgaA, Darmstadt, Germany). The membranes were incubated at 37 °C, and the SBF was added every 10 days to maintain a constant volume. To measure the weight loss on days 15, 30, 60, 90, and 120, the membranes were collected, rinsed with distilled water, and freeze-dried in a freeze dryer (LaboGene, Lillerød, Denmark) for 3 h. Their dry weights (Wdt) were measured, and their weight loss was calculated as:
The morphology of the membranes during the test was evaluated via SEM (n = 2/time point).
The morphology of the membranes during the test was evaluated via SEM (n = 2/time point).