After centrifugation (20,000 g, 20 min, 20°C), supernatants were transferred to a filtration plate (96-well plates Acroprep 1 ml, 45 μm GHP membrane, Pall Life Science, Portsmouth, United Kingdom) and filtered under a vacuum with a vacuum manifold (Pall Corporation, Portsmouth, United Kingdom) to be collected on a collector plate (a 96-well