Quantifying Complement and Leukocyte Activation

To determine complement and leukocyte activation, an enzyme-linked immunosorbent assay (ELISA) was performed. The SF, Hep/SF films, and PTFE sheets were pre-incubated with PBS at 37 °C for 5 min. The PBS was replaced with lithium heparinized blood and incubated at 37 °C for 1 h. Blood performed accordingly without samples was used as a control. After incubation, the plasma was isolated by centrifugation at 1400× g for 15 min. Complement activation was determined by using ELISA Kits for complement fragments C3a (ab279352, Abcam, Cambridge, UK) and C5a (ab193695, Abcam, Cambridge, UK). Leukocyte activation was determined by using ELISA Kits for polymorphonuclear neutrophil (PMN) elastase (ab119553, Abcam, Cambridge, UK). Measurements were performed according to the manufacturer’s instructions and in quadruplicate for each sample. The absorbance was measured using a microplate reader (SpectraMax® iD3, Molecular Devices, LLC., San Jose, CA, USA) [39 (link),40 (link)].