192 Chapter 8 Statistical analysis All statistical analyses were performed using GraphPad Prism v9.1.0 (GraphPad Company, San Diego, USA). Data are presented as mean values with standard deviation (SD). All data was tested for outliers using the robust regression and outlier removal (ROUT) test and analysed for normality using Shapiro-Wilk and Q-Q plots (Supplementary Figure 3). For the data that were normally distributed, differences between control porcine lung ECM hydrogel and ruthenium crosslinked ECM hydrogels generated from the same batch of LdECM and used in the same experiment were tested by paired t-test to compare the effect of crosslinking between different experiments. For the data that were not normally distributed, Mann-Whitney test was used to compare the effect of crosslinking between different experiments. All data were considered significantly different when p < 0.05. RESULTS Ruthenium crosslinking increases hydrogel stiffness Both LdECM and Ru-LdECM solutions were able to form hydrogels after incubating at 37 °C. UV/Visible light crosslinking did not result in a macroscopic change in the LdECM hydrogels. Ru-LdECM hydrogels (and the solution before the crosslinking) had a bright orange colour due to the ruthenium addition. Stiffness measurements on LdECM and Ru-LdECM hydrogels were performed using a low-load compression tester (LLCT). Ruthenium crosslinking increased the stiffness of the Ru-LdECM 5-10-fold (p = 0.0026, paired t-test) (Figure 2).
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