MMP-9 concentrations in supernatants from PMN cultures pre-treated with 10 _M PP1 on PEG hydrogels, PDMS, TCPS and GP hydrogels at 2 hours. Results represent the mean ± standard deviation with each data point representing a different donor, n = 4. **: significant difference with PP1 pre-treatment, p = 0.001–0.01; ***: significant difference with PP1 pre-treatment, p = 0.0001–0.001; ****: significant difference with PP1 pre-treatment, p < 0.0001.