Figure 4. ROS production in macrophages treated with 24-h extracts from ZnO-coated anodized aluminum oxide membranes over 1 h, 3 h, 12 h, and 24 h. Cells were treated with H₂O₂ as a positive control. All experimental groups, including ZnO-coated and uncoated anodized aluminum oxide, had similar responses to cells grown with fresh media, indicating no significant ROS generation for any surface extract.