MPO concentrations in supernatants from PMN cultures on PEG hydrogels, PDMS, TCPS and GP hydrogels at 2 and 4 hours. Results represent the mean ± standard deviation with each data point representing a different donor, n = 4. *: significant difference between materials, p = 0.01–0.05; **: significant difference between materials, p = 0.001–0.01.